publicationDate,title,abstract,id 2005-10-28,Negative-coupling resonances in pump-coupled lasers,"We consider coupled lasers, where the intensity deviations from the steady state, modulate the pump of the other lasers. Most of our results are for two lasers where the coupling constants are of opposite sign. This leads to a Hopf bifurcation to periodic output for weak coupling. As the magnitude of the coupling constants is increased (negatively) we observe novel amplitude effects such as a weak coupling resonance peak and, strong coupling subharmonic resonances and chaos. In the weak coupling regime the output is predicted by a set of slow evolution amplitude equations. Pulsating solutions in the strong coupling limit are described by discrete map derived from the original model.",0510072v1 2024-04-09,Dynamics of large oscillator populations with random interactions,"We explore large populations of phase oscillators interacting via random coupling functions. Two types of coupling terms, the Kuramoto-Daido coupling and the Winfree coupling, are considered. Under the assumption of statistical independence of the phases and the couplings, we derive reduced averaged equations with effective non-random coupling terms. As a particular example, we study interactions that have the same shape but possess random coupling strengths and random phase shifts. While randomness in coupling strengths just renormalizes the interaction, a distribution of the phase shifts in coupling reshapes the coupling function.",2404.06193v1 2022-06-12,Occasional coupling enhances amplitude death in delay-coupled oscillators,"This paper aims to study amplitude death in time delay coupled oscillators using the occasional coupling scheme that implies the intermittent interaction among the oscillators. An enhancement of amplitude death regions (i.e., an increment of the width of the amplitude death regions along the control parameter axis) can be possible using the occasional coupling in a pair of delay-coupled oscillators. Our study starts with coupled limit cycle oscillators (Stuart-Landau) and coupled chaotic oscillators (R\""ossler). We further examine coupled horizontal Rijke tubes, a prototypical model of thermoacoustic systems. Oscillatory states are highly detrimental to thermoacoustic systems such as combustors. Consequently, a state of amplitude death is always preferred. We employ the on-off coupling (i.e., a square wave function), as an occasional coupling scheme, to these coupled oscillators. On monotonically varying the coupling strength (as a control parameter), we observe an enhancement of amplitude death regions using the occasional coupling scheme compared to the continuous coupling scheme. In order to study the contribution of the occasional coupling scheme, we perform a detailed linear stability analysis and analytically explain this enhancement of the amplitude death region for coupled limit cycle oscillators. We also adopt the frequency ratio of the oscillators and the time delay between the oscillators as the control parameters. Intriguingly, we obtain a similar enhancement of the amplitude death regions using frequency ratio and time delay as the control parameters in the presence of the occasional coupling. Finally, we use a half-wave rectified sinusoidal wave function (motivated by practical reality) to introduce the occasional coupling in time-delay coupled oscillators and get similar results.",2206.05774v2 2017-10-27,A note on faithful coupling of Markov chains,"One often needs to turn a coupling $(X_i, Y_i)_{i\geq 0}$ of a Markov chain into a sticky coupling where once $X_T = Y_T$ at some $T$, then from then on, at each subsequent time step $T'\geq T$, we shall have $X_{T'} = Y_{T'}$. However, not all of what are considered couplings in literature, even Markovian couplings, can be turned into sticky couplings, as proved by Rosenthal through a counter example. Rosenthal then proposed a strengthening of the Markovian coupling notion, termed as faithful coupling, from which a sticky coupling can indeed be obtained. We identify the reason why a sticky coupling could not be obtained in the counter example of Rosenthal, which motivates us to define a type of coupling which can obviously be turned into a sticky coupling. We show then that the new type of coupling that we define, and the faithful coupling as defined by Rosenthal, are actually identical. Our note may be seen as a demonstration of the naturalness of the notion of faithful coupling.",1710.10026v1 2020-07-01,Coupling Learning of Complex Interactions,"Complex applications such as big data analytics involve different forms of coupling relationships that reflect interactions between factors related to technical, business (domain-specific) and environmental (including socio-cultural and economic) aspects. There are diverse forms of couplings embedded in poor-structured and ill-structured data. Such couplings are ubiquitous, implicit and/or explicit, objective and/or subjective, heterogeneous and/or homogeneous, presenting complexities to existing learning systems in statistics, mathematics and computer sciences, such as typical dependency, association and correlation relationships. Modeling and learning such couplings thus is fundamental but challenging. This paper discusses the concept of coupling learning, focusing on the involvement of coupling relationships in learning systems. Coupling learning has great potential for building a deep understanding of the essence of business problems and handling challenges that have not been addressed well by existing learning theories and tools. This argument is verified by several case studies on coupling learning, including handling coupling in recommender systems, incorporating couplings into coupled clustering, coupling document clustering, coupled recommender algorithms and coupled behavior analysis for groups.",2007.13534v1 2022-01-24,The Coupled Rejection Sampler,"We propose a coupled rejection-sampling method for sampling from couplings of arbitrary distributions. The method relies on accepting or rejecting coupled samples coming from dominating marginals. Contrary to existing acceptance-rejection coupling methods, the variance of the execution time of the proposed method is limited and stays finite as the two target marginals approach each other in the sense of the total variation norm. In the important special case of coupling multivariate Gaussians with different means and covariances, we derive positive lower bounds for the resulting coupling probability of our algorithm, and we then show how the coupling method can be optimized in closed form. Finally, we show how we can modify the coupled rejection-sampling method to propose from coupled ensemble of proposals, so as to asymptotically recover a maximal coupling. We then apply the method to the problem of coupling rare events samplers, derive a parallel coupled resampling algorithm to use in particle filtering, and show how the coupled rejection-sampler can be used to speed up unbiased MCMC methods based on couplings.",2201.09585v2 2001-10-19,Spectral Properties and Synchronization in Coupled Map Lattices,"Spectral properties of Coupled Map Lattices are described. Conditions for the stability of spatially homogeneous chaotic solutions are derived using linear stability analysis. Global stability analysis results are also presented. The analytical results are supplemented with numerical examples. The quadratic map is used for the site dynamics with different coupling schemes such as global coupling, nearest neighbor coupling, intermediate range coupling, random coupling, small world coupling and scale free coupling.",0110037v1 2004-07-07,Stabilization of causally and non-causally coupled map lattices,"Two-dimensional coupled map lattices have global stability properties that depend on the coupling between individual maps and their neighborhood. The action of the neighborhood on individual maps can be implemented in terms of ""causal"" coupling (to spatially distant past states) or ""non-causal"" coupling (to spatially distant simultaneous states). In this contribution we show that globally stable behavior of coupled map lattices is facilitated by causal coupling, thus indicating a surprising relationship between stability and causality. The influence of causal versus non-causal coupling for synchronous and asynchronous updating as a function of coupling strength and for different neighborhoods is analyzed in detail.",0407011v1 2011-10-03,Solutions of Several Coupled Discrete Models in terms of Lame Polynomials of Order One and Two,"Coupled discrete models abound in several areas of physics. Here we provide an extensive set of exact quasiperiodic solutions of a number of coupled discrete models in terms of Lame polynomials of order one and two. Some of the models discussed are (i) coupled Salerno model, (ii) coupled Ablowitz-Ladik model, (iii) coupled saturated discrete nonlinear Schrodinger equation, (iv) coupled phi4 model, and (v) coupled phi6 model. Furthermore, we show that most of these coupled models in fact also possess an even broader class of exact solutions.",1110.0540v1 2017-10-26,Markovian Maximal Coupling of Markov Processes,"Markovian maximal couplings of Markov processes are characterized by an equality of total variation and a distance of Wasserstein type. If a Markovian maximal coupling is a Feller process, the generator can be calculated, e.g. for reflection coupled Brownian motion. Apart from processes with continuous paths also jump processes are treated for the first time. For subordinated Brownian motion a Markovian maximal coupling is constructed by subordinating reflection coupled Brownian motion. This coupling is the unique Markovian maximal coupling and its generator is determined by state-space dependent mirror coupling of the corresponding L\'evy measures.",1710.09654v1 2017-11-11,Completion of the integrable coupling systems,"In this paper, we proposed an procedure to construct the completion of the integrable system by adding a perturbation to the generalized matrix problem, which can be used to continuous integrable couplings, discrete integrable couplings and super integrable couplings. As example, we construct the completion of the Kaup-Newell (KN) integrable coupling, the Wadati-Konno-Ichikawa (WKI) integrable couplingsis, vector Ablowitz-Kaup-Newell-Segur (vAKNS) integrable couplings, the Volterra integrable couplings, Dirac type integrable couplings and NLS-mKdV type integrable couplings.",1711.04073v1 2014-10-17,A definition of the coupled-product for multivariate coupled-exponentials,"The coupled-product and coupled-exponential of the generalized calculus of nonextensive statistical mechanics are defined for multivariate functions. The nonlinear statistical coupling is indexed such that k_d = k/(1+dk), where d is the dimensions of the argument of the multivariate coupled-exponential. The coupled-Gaussian distribution is defined such that the argument of the coupled-exponential depends on the coupled-moments but not the coupling parameter. The multivariate version of the coupled-product is defined such that the output dimensions are the sum of the input dimensions. This enables construction of the multivariate coupled-Gaussian from univariate coupled-Gaussians. The resulting construction forms a model of coupling between distributions, generalizing the product of independent Gaussians.",1410.4727v3 2022-01-10,Character of couple and couple-stress in continuum mechanics,"In this paper, the concept of moment and couple in mechanics is examined from a fundamental perspective. It turns out that although representing a couple by its moment vector is very useful in rigid body mechanics and strength of materials, it has been very misleading in continuum mechanics. To specify the effect of a concentrated couple in continuum mechanics, not only the couple moment, but also the line of action of its constituent parallel opposite forces must be specified. However, in the governing equations of equilibrium or motion of a continuum, only moment of body couple, moment of couple-tractions, and moment of couple-stresses appear without specifying the line of action of any couple density forces. This results in non-uniqueness of the state of stresses and deformation in the continuum, which has shown itself in the indeterminacy of the couple-stress tensor. Nevertheless, the physical state of stress and deformation in the continuum is unique and determinate. Therefore, this imposes some restrictions on the form of body couple, couple-traction and couple-stresses. Here, the uniqueness of interactions in the continuum is used to establish that the continuum does not support a distribution of body couple, and a distribution of surface twisting couple-traction with normal moment. From this the mechanism of action of the couple-traction as a double layer of shear force-tractions, and the skew-symmetric character of the couple-stress moment tensor in continuum mechanics are also established.",2202.02152v1 2006-07-13,Generalized Synchronization in Ginzburg-Landau Equations with Local Coupling,"The establishment of generalized chaotic synchronization in Ginzburg-Landau equations unidirectionally coupled at discrete points of space (local coupling) has been studied. It is shown that generalized syn-chronization regimes are also established with this type of coupling, but the necessary intensity of coupling issignificantly higher than that in the case of a spatially homogeneous coupling",0607024v1 2008-03-17,Partially Locked States in Coupled Oscillators due to Inhomogeneous Coupling,"We investigate coupled identical phase oscillators with scale-free distribution of coupling strength. It is shown that partially locked states can occur due to the inhomogeneity in coupling and some properties of the coupling function. Various quantities of the partially locked states are computed through a self-consistency argument and the values show good agreement with simulation results.",0803.2426v2 2022-02-01,Approximate boundary synchronization by groups for a coupled system of wave equations with coupled Robin boundary conditions,"In this paper, we first give an algebraic characterization of uniqueness of continuation for a coupled system of wave equations with coupled Robin boundary conditions. Then, the approximate boundary controllability and the approximate boundary synchronization by groups for a coupled system of wave equations with coupled Robin boundary controls are developed around this fundamental characterization.",2202.00746v1 2017-03-23,Dimensional-invariance principles in coupled dynamical systems-- A unified analysis and applications,"In this paper we study coupled dynamical systems and investigate dimension properties of the subspace spanned by solutions of each individual system. Relevant problems on \textit{collinear dynamical systems} and their variations are discussed recently by Montenbruck et. al. in \cite{collinear2017SCL}, while in this paper we aim to provide a unified analysis to derive the dimensional-invariance principles for networked coupled systems, and to generalize the invariance principles for networked systems with more general forms of coupling terms. To be specific, we consider two types of coupled systems, one with scalar couplings and the other with matrix couplings. Via the \textit{rank-preserving flow theory}, we show that any scalar-coupled dynamical system (with constant, time-varying or state-dependent couplings) possesses the dimensional-invariance principles, in that the dimension of the subspace spanned by the individual systems' solutions remains invariant. For coupled dynamical systems with matrix coefficients/couplings, necessary and sufficient conditions (for constant, time-varying and state-dependent couplings) are given to characterize dimensional-invariance principles. The proofs via a rank-preserving matrix flow theory in this paper simplify the analysis in \cite{collinear2017SCL}, and we also extend the invariance principles to the cases of time-varying couplings and state-dependent couplings. Furthermore, subspace-preserving property and signature-preserving flows are also developed for coupled networked systems with particular coupling terms. These invariance principles provide insightful characterizations to analyze transient behaviors and solution evolutions for a large family of coupled systems, such as multi-agent consensus dynamics, distributed coordination systems, formation control systems, among others.",1703.07955v2 2021-02-20,Multi-Phase Locking Value: A Generalized Method for Determining Instantaneous Multi-frequency Phase Coupling,"Many physical, biological and neural systems behave as coupled oscillators, with characteristic phase coupling across different frequencies. Methods such as $n:m$ phase locking value and bi-phase locking value have previously been proposed to quantify phase coupling between two resonant frequencies (e.g. $f$, $2f/3$) and across three frequencies (e.g. $f_1$, $f_2$, $f_1+f_2$), respectively. However, the existing phase coupling metrics have their limitations and limited applications. They cannot be used to detect or quantify phase coupling across multiple frequencies (e.g. $f_1$, $f_2$, $f_3$, $f_4$, $f_1+f_2+f_3-f_4$), or coupling that involves non-integer multiples of the frequencies (e.g. $f_1$, $f_2$, $2f_1/3+f_2/3$). To address the gap, this paper proposes a generalized approach, named multi-phase locking value (M-PLV), for the quantification of various types of instantaneous multi-frequency phase coupling. Different from most instantaneous phase coupling metrics that measure the simultaneous phase coupling, the proposed M-PLV method also allows the detection of delayed phase coupling and the associated time lag between coupled oscillators. The M-PLV has been tested on cases where synthetic coupled signals are generated using white Gaussian signals, and a system comprised of multiple coupled R\""ossler oscillators. Results indicate that the M-PLV can provide a reliable estimation of the time window and frequency combination where the phase coupling is significant, as well as a precise determination of time lag in the case of delayed coupling. This method has the potential to become a powerful new tool for exploring phase coupling in complex nonlinear dynamic systems.",2102.10471v2 2021-10-21,Array Element Coupling in Radio Interferometry I: A Semi-Analytic Approach,"We derive a general formalism for interferometric visibilities, which considers first-order antenna-antenna coupling and assumes steady-state, incident radiation. We simulate such coupling features for non-polarized skies on a compact, redundantly-spaced array and present a phenomenological analysis of the coupling features. Contrary to previous studies, we find mutual coupling features manifest themselves at nonzero fringe rates. We compare power spectrum results for both coupled and non-coupled (noiseless, simulated) data and find coupling effects to be highly dependent on LST, baseline length, and baseline orientation. For all LSTs, lengths, and orientations, coupling features appear at delays which are outside the foreground 'wedge', which has been studied extensively and contains non-coupled astrophysical foreground features. Further, we find that first-order coupling effects threaten our ability to average data from baselines with identical length and orientation. Two filtering strategies are proposed which may mitigate such coupling systematics. The semi-analytic coupling model herein presented may be used to study mutual coupling systematics as a function of LST, baseline length, and baseline orientation. Such a model is not only helpful to the field of 21cm cosmology, but any study involving interferometric measurements, where coupling effects at the level of at least 1 part in 10^4 could corrupt the scientific result. Our model may be used to mitigate coupling systematics in existing radio interferometers and to design future arrays where the configuration of array elements inherently mitigates coupling effects at desired LSTs and angular resolutions.",2110.10879v2 2020-07-27,A critical quartet for queuing couples,"We enumerate arrangements of $n$ couples, i.e. pairs of people, placed in a single-file queue, and consider four statistics from the vantage point of a distinguished given couple. In how many arrangements are exactly $p$ of the $n-1$ other couples i) interlaced with the given couple, ii) contained within them, iii) containing the given couple, and iv) lying outside the given couple? We provide generating functions which enumerate these arrangements and obtain the associated continuous asymptotic distributions in the $n\to\infty$ limit. The asymptotic distributions corresponding to cases i), iii), and iv) evince critical phenomena around the value $p_c=(n-1)/2$, such that the probability that 1) the couple is interlaced with more than half of the other couples, and 2) the couple is contained by more than half of the other couples, are both zero in the strict $n\to\infty$ limit. We further show that the cumulative probability that less than half of the other couples lie outside the given couple is $\pi/4$ in the limit, and that the associated distribution is uniform for $p3$. It is found that the critical scaling behaviors depend on the range of coupling interaction. In the extreme long-range case of global coupling, in which each area-preserving map is coupled to all the other area-preserving maps with equal strength, there exist an infinite number of bifurcation routes in the parameter plane, each of which ends at a critical point. The critical behaviors, which vary depending on the type of bifurcation routes, are the same as those for the previously-studied small $N$ cases $(N=2,3)$, independently of $N$. However, for any other non-global coupling cases of shorter range couplings, there remains only one bifurcation route ending at the zero-coupling critical point, at which the $N$ area-preserving maps become uncoupled, The critical behavior at the zero-coupling point is also the same as that for the small $N$ cases $(N=2,3)$, independently of the coupling range.",9411002v1 1996-04-05,Period p-tuplings in coupled maps,"We study the critical behavior (CB) of all period $p$-tuplings $(p \!=\!2,3,4,\dots)$ in $N$ $(N \!=\! 2,3,4,\dots)$ symmetrically coupled one-dimensional maps. We first investigate the CB for the $N=2$ case of two coupled maps, using a renormalization method. Three (five) kinds of fixed points of the renormalization transformation and their relevant ``coupling eigenvalues'' associated with coupling perturbations are found in the case of even (odd) $p$. We next study the CB for the linear- and nonlinear-coupling cases (a coupling is called linear or nonlinear according to its leading term), and confirm the renormalization results. Both the structure of the critical set (set of the critical points) and the CB vary according as the coupling is linear or nonlinear. Finally, the results of the two coupled maps are extended to many coupled maps with $N \geq 3$, in which the CB depends on the range of coupling.",9604002v1 1998-09-17,Critical Behavior of Period Doublings in Coupled Inverted Pendulums,"We study the critical behaviors of period doublings in N (N=2,3,4,...) coupled inverted pendulums by varying the driving amplitude $A$ and the coupling strength $c$. It is found that the critical behaviors depend on the range of coupling interaction. In the extreme long-range case of global coupling, in which each inverted pendulum is coupled to all the other ones with equal strength, the zero-coupling critical point and an infinity of critical line segments constitute the same critical set in the $A-c$ plane, independently of $N$. However, for any other nonglobal-coupling cases of shorter-range couplings, the structure of the critical set becomes different from that for the global-coupling case, because of a significant change in the stability diagram of periodic orbits born via period doublings. The critical scaling behaviors on the critical set are also found to be the same as those for the abstract system of the coupled one-dimensional maps.",9809014v1 2006-10-19,Network Synchronization with an Adaptive Coupling Strength,"In this paper, new schemes to synchronize linearly or nonlinearly coupled chaotic systems with an adaptive coupling strength are proposed. Unlike other adaptive schemes, which synchronize coupled chaotic systems to a special trajectory (or an equilibrium point) of the uncoupled node by adding negative feedbacks adaptively; here, adaptive schemes for the coupling strength are used to synchronize coupled chaotic systems without knowing the synchronization trajectory. Moreover, in many applications, the state variables are not observable; instead, some functions of the states can be observed. How to synchronize coupled systems with the observed data is of great significance. In this paper, synchronization of nonlinearly coupled chaotic systems with an adaptive coupling strength is also discussed. The validity of those schemes are proved rigorously. Moreover, simulations show that by choosing some proper parameter $\alpha$, the coupling strength obtained by adaptation could be much smaller. It means that chaos oscillators can be easily synchronized with a very weak coupling.",0610580v1 2012-09-02,Coupling and tracking of regime-switching martingales,"This paper describes two explicit couplings of standard Brownian motions $B$ and $V$, which naturally extend the mirror coupling and the synchronous coupling and respectively maximise and minimise (uniformly over all time horizons) the coupling time and the tracking error of two regime-switching martingales. The generalised mirror coupling minimizes the coupling time of the two martingales while simultaneously maximising the tracking error for all time horizons. The generalised synchronous coupling maximises the coupling time and minimises the tracking error over all co-adapted couplings. The proofs are based on the Bellman principle. We give counterexamples to the conjectured optimality of the two couplings amongst a wider classes of stochastic integrals.",1209.0180v3 2016-04-12,Synchronization of linearly coupled reaction-diffusion neural networks with hybrid coupling and time-varying delays via aperiodically intermittent pinning control,"In this paper, the complete synchronization problem of linearly coupled neural networks with reaction-diffusion terms and time-varying delays via aperiodically intermittent pinning control is investigated. The coupling matrix for the network can be asymmetric. Compared with state coupling in the synchronization literature, we design a novel distributed coupling protocol by using the reaction-diffusion coupling-spatial coupling, which can accelerate the synchronization process. This can be regarded as the main difference between this paper and previous works. Using the Lyapunov function and theories in the aperiodically intermittent control, we present some criteria for the complete synchronization with a static coupling strength. In this case, there is no constraint on the bound of time-varying delays, so it can be larger than the length of control span. On the other hand, for the network with an adaptive coupling strength, we propose a simple adaptive rule for the coupling strength and prove its effectiveness rigorously. In this case, the bound of time-varying delay is required to be less than the infimum of the control time span. Finally, numerical simulations are given to verify the theoretical results.",1604.03379v1 2014-06-13,The Exact Effective Couplings of 4D N=2 gauge theories,"The anomalous dimensions of operators in the purely gluonic SU(2,1|2) sector of any planar conformal N=2 theory can be read off from the N=4 SYM results by replacing the N=4 coupling constant by an interpolating function of the N=2 coupling constants, to which we refer to as the effective coupling. For a large class of N=2 theories we compute the weak coupling expansion of these functions as well as the leading strong coupling term by employing supersymmetric localization. Via Feynman diagrams, we interpret our results as the relative (between N=2 and N=4) finite renormalization of the coupling constant. Using the AdS/CFT dictionary, we identify the effective couplings with the effective string tensions of the corresponding gravity dual theories. Thus, any observable in the SU(2,1|2) sector can be obtained from its N=4 counterpart by replacing the N=4 coupling constant by the universal, for a given theory, effective coupling.",1406.3629v2 2020-09-25,Optimal control of network-coupled subsystems: Spectral decomposition and low-dimensional solutions,"In this paper, we investigate optimal control of network-coupled subsystems where the dynamics and the cost couplings depend on an underlying undirected weighted graph. The graph coupling matrix in the dynamics may be the adjacency matrix, the Laplacian matrix, or any other symmetric matrix corresponding to the underlying graph. The cost couplings can be any polynomial function of the underlying coupling matrix. We use the spectral decomposition of the graph coupling matrix to decompose the overall system into (L+1) systems with decoupled dynamics and cost, where L is the rank of the coupling matrix. Furthermore, the optimal control input at each subsystem can be computed by solving (Ldist + 1) decoupled Riccati equations where Ldist (Ldist \leq L) is the number of distinct non-zero eigenvalues of the coupling matrix. A salient feature of the result is that the solution complexity depends on the number of distinct eigenvalues of the coupling matrix rather than the size of the network. Therefore, the proposed solution framework provides a scalable method for synthesizing and implementing optimal control laws for large-scale network-coupled subsystems.",2009.12367v2 2023-11-09,More on closed string effective actions at order $α'^2$,"Recent progress in string theory has unveiled the discovery of NS-NS couplings in bosonic and heterotic effective actions at order $\alpha'^2$, which were achieved by imposing $O(1,1)$ symmetry on the circle reduction of classical effective actions. While the bosonic theory features 25 couplings, the heterotic theory encompasses 24 parity-even and 3 parity-odd couplings, excluding the pure gravity couplings. In this study, we redefine the even-parity couplings in the bosonic and heterotic theories through the application of appropriate field redefinitions, resulting in 10 and 8 couplings, respectively. To establish the validity of these couplings, a cosmological reduction is conducted, demonstrating that the cosmological couplings in the heterotic theory vanish, subject to one-dimensional field redefinitions that include the lapse function and total derivative terms. Additionally, it is observed that the cosmological couplings in the bosonic theory can be expressed as $\mathrm{tr}(\dS^6)$. These results are consistent with existing literature, where such behavior is attributed to the pure gravity component of the couplings. Furthermore, the consistency of the obtained couplings with 4-point string theory S-matrix elements is confirmed.",2311.05207v2 1995-09-12,Optical absorption in the strong coupling limit of Eliashberg theory,"We calculate the optical conductivity of superconductors in the strong-coupling limit. In this anomalous limit the typical energy scale is set by the coupling energy, and other energy scales such as the energy of the bosons mediating the attraction are negligibly small. We find a universal frequency dependence of the optical absorption which is dominated by bound states and differs significantly from the weak coupling results. A comparison with absorption spectra of superconductors with enhanced electron-phonon coupling shows that typical features of the strong-coupling limit are already present at intermediate coupling.",9509065v1 1998-02-23,Capacitively coupled Josephson-junction chains: straight and slanted coupling,"Two chains of ultrasmall Josephson junctions, coupled capacitively with each other in the two different ways, straight and slanted coupling, are considered. As the coupling capacitance increases, regardless of the coupling scheme, the transport of particle-hole pairs in the system is found to drive the quantum-phase transition at zero temperature, which is a insulator-to-superfluid transition of the particle-hole pairs and belongs to the Berezinskii-Kosterlitz-Thouless universal class. The different underlying transport mechanisms for the two coupling schemes are reflected in the difference between the transition points.",9802237v1 2001-09-21,Slower Speed and Stronger Coupling: Adaptive Mechanisms of Self-Organized Chaos Synchronization,"We show that two initially weakly coupled chaotic systems can achieve self-organized synchronization by adaptively reducing their speed and/or enhancing the coupling strength. Explicit adaptive algorithms for speed-reduction and coupling-enhancement are provided. We apply these algorithms to the self-organized synchronization of two coupled Lorenz systems. It is found that after a long-time self-organized process, the two coupled chaotic systems can achieve synchronization with almost minimum required coupling-speed ratio.",0109395v1 2002-01-21,Stability of Synchronized Chaos in Coupled Dynamical Systems,"We consider the stability of synchronized chaos in coupled map lattices and in coupled ordinary differential equations. Applying the theory of Hermitian and positive semidefinite matrices we prove two results that give simple bounds on coupling strengths which ensure the stability of synchronized chaos. Previous results in this area involving particular coupling schemes (e.g. global coupling and nearest neighbor diffusive coupling) are included as special cases of the present work.",0201037v1 2006-04-26,Synchronization of Mutually Versus Unidirectionally Coupled Chaotic Semiconductor Lasers,"Synchronization dynamics of mutually coupled chaotic semiconductor lasers are investigated experimentally and compared to identical synchronization of unidirectionally coupled lasers. Mutual coupling shows high quality synchronization in a broad range of self-feedback and coupling strengths. It is found to be tolerant to significant parameter mismatch which for unidirectional coupling would result in loss of synchronization. The advantages of mutual coupling are emphasized in light of its potential use in chaos communications.",0604068v1 2002-10-22,$π$NN coupling and two-pion photoproduction on the nucleon,"Effects of non-resonant photoproductions arising from two different $\pi NN$ couplings are investigated in the $\gamma N\to\pi\pi N$ reaction. We find that the pseudoscalar (PS) $\pi NN$ coupling is generally preferable to the pseudovector (PV) $\pi NN$ coupling and particularly the total cross sections are successfully described by the model with the PS $\pi NN$ coupling. In order to see the difference between the two couplings, we also show the results of invariant mass spectra and helicity-dependent cross sections in various isospin channels calculated with the PS and PV couplings.",0210063v2 2003-08-15,Entangled two atoms through different couplings and the thermal noise,"The entanglement of two atoms is studied when the two atoms are coupled to a single-mode thermal field with different couplings. The different couplings of two atoms are in favor of entanglement preparation: it not only makes the case of absence entanglement with same coupling appear entanglement, but also enhances the entanglement with the increasing of the relative difference of two couplings. We also show that the diversity of coupling can improved the critical temperature. If the optical cavity is leaky during the time evolution, the dissipative thermal environment is benefit to produce the entanglement.",0308086v1 2003-10-29,Thermal entanglement of Bosonic atoms in an optical lattice with nonlinear couplings,"The thermal entanglement of two spin-1 atoms with nonlinear couplings in optical lattices is investigated in this paper. It is found that the nonlinear couplings favor the thermal entanglement creating. The dependence of the thermal entanglement in this system on the linear coupling, the nonlinear coupling, the magnetic field and temperature is also presented. The results show that the nonlinear couplings really change the feature of the thermal entanglement in the system, increasing the nonlinear coupling constant increases the critical magnetic field and the threshold temperature.",0310169v2 2008-01-22,LQR-based coupling gain for synchronization of linear systems,"Synchronization control of coupled continuous-time linear systems is studied. For identical systems that are stabilizable, a linear feedback law obtained via algebraic Riccati equation is shown to synchronize any fixed directed network of any number of coupled systems provided that the coupling is strong enough. The strength of coupling is determined by the smallest distance of a nonzero eigenvalue of the coupling matrix to the imaginary axis. A dual problem where detectable systems that are coupled via their outputs is also considered and solved.",0801.3390v1 2008-04-23,Synchronization of oscillators coupled through an environment,"We study synchronization of oscillators that are indirectly coupled through their interaction with an environment. We give criteria for the stability or instability of a synchronized oscillation. Using these criteria we investigate synchronization of systems of oscillators which are weakly coupled, in the sense that the influence of the oscillators on the environment is weak. We prove that arbitrarily weak coupling will synchronize the oscillators, provided that this coupling is of the 'right' sign. We illustrate our general results by applications to a model of coupled GnRH neuron oscillators proposed by Khadra and Li, and to indirectly weakly-coupled lambda-omega oscillators",0804.3734v1 2008-05-13,Coupled Dynamics on Networks,"We study the synchronization of coupled dynamical systems on a variety of networks. The dynamics is governed by a local nonlinear map or flow for each node of the network and couplings connecting different nodes via the links of the network. For small coupling strengths nodes show turbulent behavior but form synchronized clusters as coupling increases. When nodes show synchronized behaviour, we observe two interesting phenomena. First, there are some nodes of the floating type that show intermittent behaviour between getting attached to some clusters and evolving independently. Secondly, we identify two different ways of cluster formation, namely self-organized clusters which have mostly intra-cluster couplings and driven clusters which have mostly inter-cluster couplings.",0805.1836v1 2008-09-19,Phase Response Curves of Coupled Oscillators,"Many real oscillators are coupled to other oscillators and the coupling can affect the response of the oscillators to stimuli. We investigate phase response curves (PRCs) of coupled oscillators. The PRCs for two weakly coupled phase-locked oscillators are analytically obtained in terms of the PRC for uncoupled oscillators and the coupling function of the system. Through simulation and analytic methods, the PRCs for globally coupled oscillators are also discussed.",0809.3371v1 2011-02-15,Reconstructing phase dynamics of oscillator networks,"We generalize our recent approach to reconstruction of phase dynamics of coupled oscillators from data [B. Kralemann et al., Phys. Rev. E, 77, 066205 (2008)] to cover the case of small networks of coupled periodic units. Starting from the multivariate time series, we first reconstruct genuine phases and then obtain the coupling functions in terms of these phases. The partial norms of these coupling functions quantify directed coupling between oscillators. We illustrate the method by different network motifs for three coupled oscillators and for random networks of five and nine units. We also discuss nonlinear effects in coupling.",1102.3064v1 2011-10-19,Relaying phase synchrony in chaotic oscillator chains,"We study the manner in which the effect of an external drive is transmitted through mutually coupled response systems by examining the phase synchrony between the drive and the response. Two different coupling schemes are used. Homogeneous couplings are via the same variables, while heterogeneous couplings are through different variables. With the latter scenario, synchronization regimes are truncated with increasing number of mutually coupled oscillators, in contrast to homogeneous coupling schemes. Our results are illustrated for systems of coupled chaotic R\""ossler oscillators.",1110.4318v1 2014-02-11,Diagonal Couplings of Quantum Markov Chains,"In this article we extend the coupling method from classical probability theory to quantum Markov chains on atomic von Neumann algebras. In particular, we establish a coupling inequality, which allow us to estimate convergence rates by analyzing couplings. For a given tensor dilation we construct a self-coupling of a Markov operator. It turns out that on a dense subset the coupling is a dual version of the extended dual transition operator previously studied by Gohm etal. We deduce that this coupling is successful if and only if the dilation is asymptotically complete.",1402.2448v1 2014-09-29,Strong-coupling phases of the anisotropic Kardar-Parisi-Zhang equation,"We study the anisotropic Kardar-Parisi-Zhang equation using nonperturbative renormalization group methods. In contrast to a previous analysis in the weak-coupling regime we find the strong coupling fixed point corresponding to the isotropic rough phase to be always locally stable and unaffected by the anisotropy even at non-integer dimensions. Apart from the well-known weak coupling and the now well established isotropic strong coupling behavior, we find an anisotropic strong coupling fixed point for nonlinear couplings of opposite signs at non-integer dimensions.",1409.8314v2 2015-02-12,Synchronization in Networks of Linearly Coupled Dynamical Systems via Event-triggered Diffusions,"In this paper, we utilize event-triggered coupling configuration to realize synchronization of linearly coupled dynamical systems. Here, the diffusion couplings are set up from the latest observations of the nodes of its neighborhood and the next observation time is triggered by the proposed criteria based on the local neighborhood information as well. Two scenarios are considered: continuous monitoring, that each node can observe its neighborhood's instantaneous states, and discrete monitoring, that each node can only obtain its neighborhood's states at the same time point when the coupling term is triggered. In both cases, we prove that if the system with persistent coupling can synchronize, then these event-trigger coupling strategies can synchronize the system, too.",1502.03602v1 2015-03-09,Enhanced electromechanical coupling of a nanomechanical resonator to coupled superconducting cavities,"We investigate the electromechanical coupling between a nanomechanical resonator and two parametrically coupled superconducting coplanar waveguide cavities that are driven by a two-mode squeezed microwave source. We show that, with the selective coupling of the resonator to the cavity Bogoliubov modes, the radiation-pressure type coupling can be greatly enhanced by several orders of magnitude, enabling the single photon strong coupling to be reached. This allows the investigation of a number of interesting phenomena such as photon blockade effects and the generation of nonclassical quantum states with electromechanical systems.",1503.02393v2 2015-09-15,Microscopic coupled-channel calculations of nucleus-nucleus scattering including chiral three-nucleon-force effects,"We analyze $^{16}$O-$^{16}$O and $^{12}$C-$^{12}$C scattering with the microscopic coupled-channels method and investigate the coupled-channels and three-nucleon-force (3NF) effects on elastic and inelastic cross sections. In the microscopic coupled-channels calculation, the Melbourne g-matrix interaction modified according to the chiral 3NF effects is used. It is found that the coupled-channels and 3NF effects additively change both the elastic and inelastic cross sections. As a result, the coupled-channels calculation including the 3NF effects significantly improves the agreement between the theoretical results and the experimental data. The incident-energy dependence of the coupled-channels and 3NF effects is also discussed.",1509.04459v1 2015-11-25,Persistence of Network Synchronization under Nonidentical Coupling Functions,"We investigate the persistence of synchronization in networks of diffusively coupled oscillators when the coupling functions are nonidentical. Under mild conditions, we uncover the influence of the network interaction structure on the mismatches of the coupling function. We show that Erd\""os-R\'enyi random graphs support large perturbations in the coupling function. In contrast scale-free graphs do not allow large perturbations in the coupling function, that is, as the network size n goes to infinity it forces the coupling functions to be identical.",1511.08065v1 2016-02-29,Ab initio determination of effective electron-phonon coupling factor in copper,"The electron temperature dependent electron density of states, Fermi-Dirac distribution, and electron-phonon spectral function are computed as prerequisites before achieving effective electron-phonon coupling factor. The obtained coupling factor is implemented into a molecular dynamics (MD) and two-temperature model (TTM) coupled simulation of femtosecond laser heating. By monitoring temperature evolutions of electron and lattice subsystems, the result utilizing coupling factor from ab initio calculation, shows a faster decrease of electron temperature and increase of lattice temperature than those using coupling factor from phenomenological treatment. The approach of calculating coupling factor and its implementation into MD-TTM simulation is applicable to other metals.",1602.09031v2 2008-07-28,Gap anisotropy and universal pairing scale in a spin fluctuation model for cuprates,"We consider the evolution of d-wave pairing, mediated by nearly critical spin fluctuations, with the coupling strength. We show that the onset temperature for pairing, T*, smoothly evolves between weak and strong coupling, passing through a broad maximum at intermediate coupling. At strong coupling, T* is of order the magnetic exchange energy J. We argue that for all couplings, pairing is confined to the vicinity of the Fermi surface. We also find that thermal spin fluctuations only modestly reduce T*, even at criticality, but they substantially smooth the gap anisotropy. The latter evolves with coupling, being the largest at weak coupling.",0807.4404v1 2011-11-26,Solutions of Several Coupled Discrete Models in terms of Lame Polynomials of Arbitrary Order,"Coupled discrete models abound in several areas of physics. Here we provide an extensive set of exact quasiperiodic solutions of a number of coupled discrete models in terms of Lam\'e polynomials of arbitrary order. The models discussed are (i) coupled Salerno model, (ii) coupled Ablowitz-Ladik model, (iii) coupled $\phi^4$ model, and (iv) coupled $\phi^6$ model. In all these cases we show that the coefficients of the Lam\'e polynomials are such that the Lam\'e polynomials can be reexpressed in terms of Chebyshev polynomials of the relevant Jacobi elliptic function.",1111.6138v1 2017-05-03,Internal control of systems of semilinear coupled 1-D wave equations,"We prove the internal controllability of some systems of two coupled wave equations in one space dimension, with one control, under certain conditions on the coupling. To do this we apply the ""fictitious control method"" in two cases: general systems with a ""non-degenerate"" coupling, and a particular case where the coupling is ""degenerate"", namely a cubic coupling. In the latter case, our proof requires to find nontrivial trajectories of the control system that go from $0$ to $0$. We build these trajectories by adapting (in $1$ space dimension) a construction developed by Jean-Michel Coron, Sergio Guerrero and Lionel Rosier for the study of coupled parabolic systems.",1705.01383v1 2018-03-09,Non-local coupling between antiferromagnets and ferromagnets in cavities,"Microwaves couple to magnetic moments in both ferromagnets and antiferromagnets. Although the magnons in ferromagnets and antiferromagnets radically differ, they can become entangled via strong coupling to the same microwave mode in a cavity. The equilibrium configuration of the magnetic moments crucially governs the coupling between the different magnons because the antiferromagnetic and ferromagnetic magnons have the opposite spins when their dispersion relations cross. We derive analytical expressions for the coupling strengths and find that the coupling between antiferromagnets and ferromagnets is comparable to the coupling between two ferromagnets. Our findings reveal a robust link between cavity spintronics with ferromagnets and antiferromagnets.",1803.03486v1 2019-04-19,Symmetry Breaking Creates Electro-Momentum Coupling in Piezoelectric Metamaterials,"Metamaterials posses microstructure designed to acquire properties not found in nature. An epitome in acoustics and solid mechanics is Willis coupling, which refers to the particle velocity-stress coupling, and of great significance since it controls mechanical waves. We here reveal new couplings, analogous to Willis coupling, when considering patterns of materials that mechanically interact with magnetic, electric or thermal fields. To this end, we develop a rigorous homogenization method for the effective properties of such responsive metamaterials. As an example, we apply the scheme to piezoelectric materials, and unveil coupling of the velocity and electric fields. Hence, Willis-like couplings in responsive metamaterials open new avenues for active wave control by modulation of external stimuli.",1904.09180v2 2017-07-29,EIT-Enhanced Coupled-Resonance Spectroscopy,"Coupled-resonance spectroscopy has been recently reported and applied for spectroscopic measurements and laser stabilizations. With coupled-resonance spectroscopy, one may indirectly measure some transitions between the excited states that are hard to be measured directly because of the lack of populations in the excited states. An improvement of the coupled-resonance spectroscopy by combining the technology of electromagnetically induced transparency (EIT) is proposed. The coupled-resonance spectroscopy signal can be significantly enhanced by EIT. Several experimental schemes have been discussed. The line shape of the EIT-enhanced coupled-resonance spectroscopy has been calculated.The EIT-enhanced coupled-resonance spectroscopy can be used for simultaneously stabilizing two lasers to the same atomic source.",1707.09559v1 2013-06-25,Dynamical spin-spin coupling of quantum dots,"We carried out a nested Schrieffer-Wolff transformation of an Anderson two-impurity Hamiltonian to study the spin-spin coupling between two dynamical quantum dots under the influence of rotating transverse magnetic field. As a result of the rotating field, we predict a novel Ising type spin-spin coupling mechanism between quantum dots, whose strength is tunable via the magnitude of the rotating field. The strength of the new coupling could be comparable to the strength of the RKKY coupling. The dynamical coupling with the intristic RKKY coupling enables to construct a four level system of maximally entangled Bell states in a controllable manner.",1306.5889v2 2018-08-14,Dynamical and Coupling Structure of Pulse-Coupled Networks in Maximum Entropy Analysis,"Maximum entropy principle (MEP) analysis with few non-zero effective interactions successfully characterizes the distribution of dynamical states of pulse-coupled networks in many experiments, e.g., in neuroscience. To better understand the underlying mechanism, we found a relation between the dynamical structure, i.e., effective interactions in MEP analysis, and the coupling structure of pulse-coupled network to understand how a sparse coupling structure could lead to a sparse coding by effective interactions. This relation quantitatively displays how the dynamical structure is closely related to the coupling structure.",1808.04499v1 2020-03-11,Pattern in non-linearly coupled network of identical Thomas oscillators,"We have investigated synchronized pattern in a network of Thomas oscillators coupled with sinusoidal nonlinear coupling. Pattern like chimera states are not only observed for many non-locally coupled oscillators but there is a signature of it even for locally coupled few oscillators. For certain range of intermediate coupling, clusters are also observed. These patterns do resemble with motion of real self propelled coupled dynamical systems.",2003.05210v2 2020-08-26,Caccioppoli-type estimates and $\mathcal{H}$-Matrix approximations to inverses for FEM-BEM couplings,"We consider three different methods for the coupling of the finite element method and the boundary element method, the Bielak-MacCamy coupling, the symmetric coupling, and the Johnson-N\'ed\'elec coupling. For each coupling we provide discrete interior regularity estimates. As a consequence, we are able to prove the existence of exponentially convergent $\mathcal{H}$-matrix approximants to the inverse matrices corresponding to the lowest order Galerkin discretizations of the couplings.",2008.11498v1 2021-05-06,Snaking bifurcations of localized patterns on ring lattices,"We study the structure of stationary patterns in bistable lattice dynamical systems posed on rings with a symmetric coupling structure in the regime of small coupling strength. We show that sparse coupling (for instance, nearest-neighbour or next-nearest-neighbour coupling) and all-to-all coupling lead to significantly different solution branches. In particular, sparse coupling leads to snaking branches with many saddle-node bifurcations, whilst all-to-all coupling leads to branches with six saddle nodes, regardless of the size of the number of nodes in the graph.",2105.02380v1 2023-07-27,High-order phase reduction for coupled 2D oscillators,"Phase reduction is a general approach to describe coupled oscillatory units in terms of their phases, assuming that the amplitudes are enslaved. For such a reduction, the coupling should be small, but one also expects the reduction to be valid for finite coupling. This paper presents a general framework allowing us to obtain coupling terms in higher orders of the coupling parameter for generic two-dimensional oscillators and arbitrary coupling terms. The theory is illustrated with an accurate prediction of Arnold's tongue for the van der Pol oscillator exploiting higher-order phase reduction.",2307.14711v2 2023-08-20,New Solutions of Coupled Nonlocal NLS and Coupled Nonlocal mKdV Equations,"We provide several novel solutions of the coupled Ablowitz-Musslimani (AM) version of the nonlocal nonlinear Schr\""odinger (NLS) equation and the coupled nonlocal modified Korteweg-de Vries (mKdV) equations. In each case we compare and contrast the corresponding solutions of the relevant coupled local equations. Further, we provide new solutions of the coupled local NLS and the coupled local mKdV equations which are not the solutions of the corresponding nonlocal equations.",2308.10163v1 2023-09-07,Axion-Gauge Coupling Quantization with a Twist,"The possible couplings of an axion to gauge fields depend on the global structure of the gauge group. If the Standard Model gauge group is minimal, or equivalently if fractionally charged color-singlet particles are forbidden, then the QCD axion's Chern-Simons couplings to photons and gluons obey correlated quantization conditions. Specifically, the photon coupling can have a fractional part which is a multiple of 1/3, but which is determined by the gluon coupling. A consequence of this result is that, among all theories with a minimal gauge group and minimal axion coupling to gluons, the smallest possible axion-photon amplitude $|g_{a\gamma\gamma}|$ arises for $E/N = 8/3$. This provides a new motivation for experiments targeting this axion-photon coupling.",2309.03939v1 2011-03-17,Waltzing peakons and compacton pairs in a cross-coupled Camassa-Holm equation,"We consider singular solutions of a system of two cross-coupled Camassa-Holm (CCCH) equations. This CCCH system admits peakon solutions, but it is not in the two-component CH integrable hierarchy. The system is a pair of coupled Hamiltonian partial differential equations for two types of solutions on the real line, each of which separately possesses exp(-|x|) peakon solutions with a discontinuity in the first derivative at the peak. However, there are no self-interactions, so each of the two types of peakon solutions moves only under the induced velocity of the other type. We analyse the `waltzing' solution behaviour of the cases with a single bound peakon pair (a peakon couple), as well as the over-taking collisions of peakon couples and the antisymmetric case of the head-on collision of a peakon couple and a peakon anti-couple. We then present numerical solutions of these collisions, which are inelastic because the waltzing peakon couples each possess an internal degree of freedom corresponding to their `tempo' -- that is, the period at which the two peakons of opposite type in the couple cycle around each other in phase space. Finally, we discuss compacton couple solutions of the cross-coupled Euler-Poincar\'e (CCEP) equations and illustrate the same types of collisions as for peakon couples, with triangular and parabolic compacton couples. We finish with a number of outstanding questions and challenges remaining for understanding couple dynamics of the CCCH and CCEP equations.",1103.3326v1 2017-02-01,Time-varying coupling functions: dynamical inference and cause of synchronization transitions,"Interactions in nature can be described by their coupling strength, direction of coupling and coupling function. The coupling strength and directionality are relatively well understood and studied, at least for two interacting systems, however there can be a complexity in the interactions uniquely dependent on the coupling functions. Such a special case is studied here { synchronization transition occurs only due to the time-variability of the coupling functions, while the net coupling strength is constant throughout the observation time. To motivate the investigation, an example is used to present an analysis of cross-frequency coupling functions between delta and alpha brainwaves extracted from the electroencephalography (EEG) recording of a healthy human subject in a freerunning resting state. The results indicate that time-varying coupling functions are a reality for biological interactions. A model of phase oscillators is used to demonstrate and detect the synchronization transition caused by the varying coupling functions, during an invariant coupling strength. The ability to detect this phenomenon is discussed with the method of dynamical Bayesian inference, which was able to infer the time-varying coupling functions. The form of the coupling function acts as an additional dimension for the interactions and it should be taken into account when detecting biological or other interactions from data.",1702.00202v1 2018-02-15,Mitigation of dynamical instabilities in laser arrays via non-Hermitian coupling,"Arrays of coupled semiconductor lasers are systems possessing complex dynamical behavior that are of major interest in photonics and laser science. Dynamical instabilities, arising from supermode competition and slow carrier dynamics, are known to prevent stable phase locking in a wide range of parameter space, requiring special methods to realize stable laser operation. Inspired by recent concepts of parity-time ($\mathcal{PT}$) and non-Hermitian photonics, in this work we consider non-Hermitian coupling engineering in laser arrays in a ring geometry and show, both analytically and numerically, that non-Hermitian coupling can help to mitigate the onset of dynamical laser instabilities. In particular, we consider in details two kinds of nearest-neighbor non-Hermitian couplings: symmetric but complex mode coupling (type-I non-Hermitian coupling) and asymmetric mode coupling (type-II non-Hermitian coupling). Suppression of dynamical instabilities can be realized in both coupling schemes, resulting in stable phase-locking laser emission with the lasers emitting in phase (for type-I coupling) or with $\pi/2$ phase gradient (for type-II coupling), resulting in a vortex far-field beam. In type-II non-Hermitian coupling, chirality induced by asymmetric mode coupling enables laser phase locking even in presence of moderate disorder in the resonance frequencies of the lasers.",1802.05439v2 2017-05-23,Effect of Heterogeneity in Models of El-Niño Southern Oscillations,"The emergence of oscillations in models of the El-Ni\~no effect is of utmost relevance. Here we investigate a coupled nonlinear delay differential system modeling theEl-Ni\~no/ Southern Oscillation (ENSO) phenomenon, which arises through the strong coupling of the ocean-atmosphere system. In particular, we study the temporal patterns of the sea surface temperature anomaly of the two sub-regions. For identical sub-regions we typically observe a co-existence of amplitude and oscillator death behavior for low delays, and heterogeneous oscillations for high delays, when inter-region coupling is weak. For moderate inter-region coupling strengths one obtains homogeneous oscillations for sufficiently large delays and amplitude death for small delays. When the inter-region coupling strength is large, oscillations are suppressed altogether, implying that strongly coupled sub-regions do not exhibit ENSO-like oscillations. Further we observe that larger strengths of self-delay coupling favours oscillations, while oscillations die out when the delayed coupling is weak. This indicates again that delayed feedback, incorporating oceanic wave transit effects, is the principal cause of oscillatory behaviour. So the effect of trapped ocean waves propagating in a basin with closed boundaries is crucial for the emergence of ENSO. Further, we show how non-uniformity in delays, and difference in the strengths of the self-delay coupling of the sub-regions, affect the rise of oscillations. Interestingly we find that larger delays and self-delay coupling strengths lead to oscillations, while strong inter-region coupling kills oscillatory behaviour. Thus, we find that coupling sub-regions has a very significant effect on the emergence of oscillations, and strong coupling typically suppresses oscillations, while weak coupling of non-identical sub-regions can induce oscillations, thereby favouring ENSO.",1705.08171v1 2020-10-02,High-Order Accuracy Computation of Coupling Functions for Strongly Coupled Oscillators,"We develop a general framework for identifying phase reduced equations for finite populations of coupled oscillators that is valid far beyond the weak coupling approximation. This strategy represents a general extension of the theory from [Wilson and Ermentrout, Phys. Rev. Lett 123, 164101 (2019)] and yields coupling functions that are valid to higher-order accuracy in the coupling strength for arbitrary types of coupling (e.g., diffusive, gap-junction, chemical synaptic). These coupling functions can be used to understand the behavior of potentially high-dimensional, nonlinear oscillators in terms of their phase differences. The proposed formulation accurately replicates nonlinear bifurcations that emerge as the coupling strength increases and is valid in regimes well beyond those that can be considered using classic weak coupling assumptions. We demonstrate the performance of our approach through two examples. First, we use diffusively coupled complex Ginzburg-Landau (CGL) model and demonstrate that our theory accurately predicts bifurcations far beyond the range of existing coupling theory. Second, we use a realistic conductance-based model of a thalamic neuron and show that our theory correctly predicts asymptotic phase differences for non-weak synaptic coupling. In both examples, our theory accurately captures model behaviors that weak coupling theories can not.",2010.01194v2 2021-01-29,One dimensional martingale rearrangement couplings,"We are interested in martingale rearrangement couplings. As introduced by Wiesel [37] in order to prove the stability of Martingale Optimal Transport problems, these are projections in adapted Wasserstein distance of couplings between two probability measures on the real line in the convex order onto the set of martingale couplings between these two marginals. In reason of the lack of relative compactness of the set of couplings with given marginals for the adapted Wasserstein topology, the existence of such a projection is not clear at all. Under a barycentre dispersion assumption on the original coupling which is in particular satisfied by the Hoeffding-Fr\'echet or comonotone coupling, Wiesel gives a clear algorithmic construction of a martingale rearrangement when the marginals are finitely supported and then gets rid of the finite support assumption by relying on a rather messy limiting procedure to overcome the lack of relative compactness. Here, we give a direct general construction of a martingale rearrangement coupling under the barycentre dispersion assumption. This martingale rearrangement is obtained from the original coupling by an approach similar to the construction we gave in [24] of the inverse transform martingale coupling, a member of a family of martingale couplings close to the Hoeffding-Fr\'echet coupling, but for a slightly different injection in the set of extended couplings introduced by Beiglb\""ock and Juillet [9] and which involve the uniform distribution on [0, 1] in addition to the two marginals. We last discuss the stability in adapted Wassertein distance of the inverse transform martingale coupling with respect to the marginal distributions.",2101.12651v1 2022-03-15,Single-photon scattering in a giant-molecule waveguide-QED system,"We study the coherent single-photon scattering in a one-dimensional waveguide coupled to a giant artificial molecule consisting of two coupled giant atoms. Since each giant atom couples to the waveguide via two coupling points, the couplings of the molecule with the waveguide have three different coupling configurations: the separated-, braided-, and nested-coupling cases. We obtain the exact expressions of the single-photon transmission and reflection amplitudes with the real-space approach. It is found that the behavior of the scattering spectra depends on the phase shift between two neighboring coupling points, the coupling configuration, and the coupling between the two giant atoms. Concretely, we study the photon scattering in both the Markovian and non-Markovian regimes, in which the photon propagating time between two neighboring coupling points is neglected and considered, respectively. Under the Markovian limit, the asymmetric Fano line shapes in different coupling configurations of the giant-molecule waveguide-QED system can be obtained by choosing proper phase shift, and the transmission window can be adjusted by the coupling strength between the two giant atoms in these three coupling configurations. In particular, multiple reflection peaks and dips in these configurations are revived in the non-Markovian regime. This paper will pave the way for the study of controllable single-photon devices based on the giant-molecule waveguide-QED systems.",2203.07812v2 2004-03-30,Stability of vacuum in coupled directed percolation processes,"We study the absorbing phase transitions in coupled directed percolation (DP) processes with $N$-species particles in one dimension. The interspecies coupling is linear, bidirectional, and excitatory. We find that the presence of a spontaneous annihilation process $A\to 0$ is essential in stabilizing the absorbing phase (vacuum). In the coupled contact processes, the vacuum is stable and the system exhibits DP type transitions, regardless of the coupling strength, for all $N$. However, in the coupled branching annihilation random walks with one offspring (BAW), where particle annihilations occur only through binary diffusion processes $A+A\to 0$, the vacuum becomes unstable with respect to an arbitrarily small branching rate in a sufficiently strong coupling regime for $N\ge 3$. The N=2 BAW exhibits the DP type transition for any coupling strength, but the inclusion of interspecies hard core (HC) interaction makes the vacuum unstable again and the system is always active in a strong coupling regime. Critical behavior near the zero branching point is characterized by the scaling exponents, $\beta=\nu_{\bot}=1/2$ and $\nu_{||}=1$, regardless of the presence of HC interaction. We also discuss the effects of the asymmetric coupling.",0403730v1 2006-02-26,Controllable Coupling in Phase-Coupled Flux Qubits,"We propose a scheme for tunable coupling of phase-coupled flux qubits. The phase-coupling scheme can provide a strong coupling strength of the order of Josephson coupling energy of Josephson junctions in the connecting loop, while the previously studied inductive coupling scheme cannot provide due to small mutual inductance and induced currents. We show that, in order to control the coupling, we need {\it two} dc-SQUID's in the connecting loop and the control fluxes threading the dc-SQUID's must be in {\it opposite} directions. The coupling strength is analytically calculated as a function of the control flux at the co-resonance point.",0602604v3 2006-10-13,Electrical transport through a single-electron transistor strongly coupled to an oscillator,"We investigate electrical transport through a single-electron transistor coupled to a nanomechanical oscillator. Using a combination of a master-equation approach and a numerical Monte Carlo method, we calculate the average current and the current noise in the strong-coupling regime, studying deviations from previously derived analytic results valid in the limit of weak-coupling. After generalizing the weak-coupling theory to enable the calculation of higher cumulants of the current, we use our numerical approach to study how the third cumulant is affected in the strong-coupling regime. In this case, we find an interesting crossover between a weak-coupling transport regime where the third cumulant heavily depends on the frequency of the oscillator to one where it becomes practically independent of this parameter. Finally, we study the spectrum of the transport noise and show that the two peaks found in the weak-coupling limit merge on increasing the coupling strength. Our calculation of the frequency-dependence of the noise also allows to describe how transport-induced damping of the mechanical oscillations is affected in the strong-coupling regime.",0610358v1 2005-07-02,"Staticity, Self-Similarity and Critical Phenomena in a Self-Gravitating Nonlinear Sigma Model","The main part of the thesis deals with continuously and discretely self-similar solutions and type II critical phenomena in a family of self-gravitating non-linear sigma-models. The phenomena strongly depend on the dimensionless coupling constant. For small couplings we numerically construct continuously self-similar (CSS) solutions and analyze their stability properties. For large couplings we construct a discretely self-similar (DSS) solution with one unstable mode. We argue that at some critical coupling the DSS solution bifurcates from the first CSS excitation in a heteroclinic loop bifurcation. We study critical phenomena between dispersal and singularity formation (at very small couplings) respectively black hole formation (for larger couplings). We give numerical evidence that for very small couplings the generic end state of ``intermediately strong'' data is the stable CSS ground state. For small couplings the critical solution is the first CSS excitation whereas for strong couplings the threshold of black hole formation is governed by the DSS solution. We describe the phenomena occurring at intermediate couplings where the critical solution changes from CSS to DSS. Content and references are at the state of October 2001.",0507009v1 2003-11-10,Meson-Baryon Couplings from QCD Sum Rules,"Coupling constants of the pseudoscalar mesons to the octet baryons are calculated in the QCD sum rule approach. Two-point correlation function of the baryons are evaluated in a single meson state and the vacuum, which yields the designated coupling. The emphasis is on the flavor SU(3) structure of the coupling constants and reliability in extracting the coupling constants from the two-point correlation functions. We first calculate the baryon-diagonal couplings and study the reliability of the sum rule. The F/D ratio of the coupling is determined in the SU(3) limit. We further formulate the baryon-off-diagonal couplings using the projected correlation functions and the vertex functions, so that the unwanted excited states do not contaminate the sum rule. As an example, the (\pi - \Lambda - \Sigma) coupling constant is calculated and the flavor SU(3) breaking effect is studied. We find that the effect of SU(3) breaking on the (\pi - \Lambda - \Sigma) coupling constant is small.",0311117v1 2001-07-20,"Dynamics of Coupling Functions in Globally Coupled Maps: Size, Periodicity and Stability of Clusters","It is shown how different globally coupled map systems can be analyzed under a common framework by focusing on the dynamics of their respective global coupling functions. We investigate how the functional form of the coupling determines the formation of clusters in a globally coupled map system and the resulting periodicity of the global interaction. The allowed distributions of elements among periodic clusters is also found to depend on the functional form of the coupling. Through the analogy between globally coupled maps and a single driven map, the clustering behavior of the former systems can be characterized. By using this analogy, the dynamics of periodic clusters in systems displaying a constant global coupling are predicted; and for a particular family of coupling functions, it is shown that the stability condition of these clustered states can straightforwardly be derived.",0107046v1 2010-10-24,Correlated couplings and robustness of coupled networks,"Most real-world complex systems can be modelled by coupled networks with multiple layers. How and to what extent the pattern of couplings between network layers may influence the interlaced structure and function of coupled networks are not clearly understood. Here we study the impact of correlated inter-layer couplings on the network robustness of coupled networks using percolation concept. We found that the positive correlated inter-layer coupling enhaces network robustness in the sense that it lowers the percolation threshold of the interlaced network than the negative correlated coupling case. At the same time, however, positive inter-layer correlation leads to smaller giant component size in the well-connected region, suggesting potential disadvantage for network connectivity, as demonstrated also with some real-world coupled network structures.",1010.4971v1 2011-01-06,Effects of gradient coupling on amplitude death in nonidentical oscillators,"In this work, we investigate gradient coupling effect on amplitude death in an array of N cou- pled nonidentical oscillators with no-flux boundary conditions and periodic boundary conditions respectively. We find that the effects of gradient coupling on amplitude death in diffusive coupled nonidentical oscillators is quite different between those two boundaries conditions. With no-flux boundary conditions, there is a system size related critical gradient coupling $r_c$ within which the gradient coupling tends to monotonically enlarge the amplitude death domain in the parameter space. With the periodical boundary conditions, there is an optimal gradient coupling constant $r_o$ to realize largest AD domain. The gradient coupling first enlarges then decreases the amplitude death domain of diffusive coupled oscillators. The amplitude death domain of parameter space are analytically predicted for small number of gradient coupled oscillators.",1101.1127v1 2011-06-27,Running coupling corrections to inclusive gluon production,"We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. At leading order there are three powers of fixed coupling; in our final answer, these three couplings are replaced by seven factors of running coupling: five in the numerator and two in the denominator, forming a `septumvirate' of running couplings, analogous to the `triumvirate' of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. It is interesting to note that the two running couplings in the denominator of the `septumvirate' run with complex-valued momentum scales, which are complex conjugates of each other, such that the production cross section is indeed real. We use our lowest-order result to conjecture how running coupling corrections may enter the full fixed-coupling k_T-factorization formula for gluon production which includes non-linear small-x evolution.",1106.5456v1 2011-08-31,Curvature-induced spin-orbit coupling and spin relaxation in a chemically clean single-layer graphene,"The study of spin-related phenomena in materials requires knowledge on the precise form of effective spin-orbit coupling of conducting carriers in the solid-states systems. We demonstrate theoretically that curvature induced by corrugations or periodic ripples in single-layer graphenes generates two types of effective spin-orbit coupling. In addition to the spin-orbit coupling reported previously that couples with sublattice pseudospin and corresponds to the Rashba-type spin-orbit coupling in a corrugated single-layer graphene, there is an additional spin-orbit coupling that does not couple with the pseudospin, which can not be obtained from the extension of the curvature-induced spin-orbit coupling of carbon nanotubes. Via numerical calculation we show that both types of the curvature-induced spin-orbit coupling make the same order of contribution to spin relaxation in chemically clean single-layer graphene with nanoscale corrugation. The spin relaxation dependence on the corrugation roughness is also studied.",1108.6128v3 2013-02-28,Coupled skinny baker's maps and the Kaplan-Yorke conjecture,"The Kaplan-Yorke conjecture states that for ""typical"" dynamical systems with a physical measure, the information dimension and the Lyapunov dimension coincide. We explore this conjecture in a neighborhood of a system for which the two dimensions do not coincide because the system consists of two uncoupled subsystems. We are interested in whether coupling ""typically"" restores the equality of the dimensions. The particular subsystems we consider are skinny baker's maps, and we consider uni-directional coupling. For coupling in one of the possible directions, we prove that the dimensions coincide for a prevalent set of coupling functions, but for coupling in the other direction we show that the dimensions remain unequal for all coupling functions. We conjecture that the dimensions prevalently coincide for bi-directional coupling. On the other hand, we conjecture that the phenomenon we observe for a particular class of systems with uni-directional coupling, where the information and Lyapunov dimensions differ robustly, occurs more generally for many classes of uni-directionally coupled systems (also called skew-product systems) in higher dimensions.",1303.0030v1 2013-11-26,Measurement of Higgs couplings and self-coupling at the ILC,"In the Standard Model (SM) the couplings of the Higgs boson to SM particles and itself (self-couplings) are uniquely specified once the masses of the particles in question as well as the Higgs boson mass are given. Precision measurements of these couplings in the future collider experiments are the key to either verifying the mechanism of the electroweak symmetry breaking in the SM or uncovering physics beyond the SM. This article gives an overview of how various Higgs couplings will be measured at the ILC. Emphasis is put on the ILC's capability of performing fully model independent determination of absolute $HZZ$ and $HWW$ couplings, the Higgs total width, and hence various other Higgs couplings, which cover essentially all the crucial ones including the top-Yukawa coupling $Htt$ and the trilinear Higgs self-coupling $\lambda_{HHH}$. The strategy to get the best precision measurements at the ILC is through staged running, which provides many independent $\sigma\times\mathrm{Br}$ measurements for different production channels and at different energies. A method of global fitting is discussed to utilize all of the available information and to derive combined precisions.",1311.6528v1 2015-04-11,Collapse of spin-orbit coupled Bose-Einstein condensates,"A finite-size quasi two-dimensional Bose-Einstein condensate collapses if the attraction between atoms is sufficiently strong. Here we present a theory of collapse for condensates with the interatomic attraction and spin-orbit coupling. We consider two realizations of spin-orbit coupling: the axial Rashba coupling and balanced, effectively one-dimensional, Rashba-Dresselhaus one. In both cases spin-dependent ""anomalous"" velocity, proportional to the spin-orbit coupling strength, plays a crucial role. For the Rashba coupling, this velocity forms a centrifugal component in the density flux opposite to that arising due to the attraction between particles and prevents the collapse at a sufficiently strong coupling. For the balanced Rashba-Dresselhaus coupling, the spin-dependent velocity can spatially split the initial state in one dimension and form spin-projected wavepackets, reducing the total condensate density. Depending on the spin-orbit coupling strength, interatomic attraction, and the initial state, this splitting either prevents the collapse or modifies the collapse process. These results show that the collapse can be controlled by a spin-orbit coupling, thus, extending the domain of existence of condensates of attracting atoms.",1504.02860v1 2016-01-29,Spin torque driven dynamics of a coupled two layer structure: interplay between conservative and dissipative coupling,"In this manuscript the general concepts of spin wave theory are adapted to the dynamics of a self-polarized system based on two layers coupled via interlayer exchange (conservative coupling) and mutual spin torque (dissipative coupling). An analytical description of the non-linear dynamics is proposed and validated through numerical simulations. In contrast to the single layer model, the phase equation of the coupled system has a contribution coming from the dissipative part of the LLGS equation. It is shown that this is a major contribution to the frequency mandatory to describe well the most basic features of the dynamics of coupled systems. Using the proposed model a specific feature of coupled dynamics is addressed: the redshift to blueshift transition observed in the frequency current dependence of this kind of exchange coupled systems upon increasing the applied field. It is found that the blueshift regime can only occur in a region of field where the two linear eigenmodes contribute equally to the steady state mode (i.e. high mode hybridization). Finally, a general perturbed Hamiltonian equation for the coupled system is proposed.",1601.08150v1 2016-04-04,Disturbance scaling in bidirectional vehicle platoons with different asymmetry in position and velocity coupling,"This paper considers a string of vehicles where the local control law uses the states of the vehicle's immediate predecessor and follower. The coupling towards the preceding vehicle can be chosen different to the coupling towards the following vehicle, which is often referred to as an asymmetric bidirectional string. Further, the asymmetry for the velocity coupling can be chosen differently to the asymmetry in the position coupling. It is investigated how the effect of disturbance on the control errors in the string depends on the string length. It is shown, that in case of symmetric position coupling and asymmetric velocity coupling, linear scaling can be achieved. For symmetric interaction in both states, i.e., in symmetric bidirectional strings, the errors scale quadratically in the number of vehicles. When the coupling in position is asymmetric, exponential scaling may occur or the system might even become unstable. The paper thus gives a comprehensive overview of the achievable performance in linear, asymmetric, bidirectional platoons. The results reveal that symmetry in the position coupling and asymmetry in velocity coupling qualitatively improves the performance of the string. Extensive numerical results illustrate the theoretical findings.",1604.00868v2 2017-03-22,Modification of Higgs Couplings in Minimal Composite Models,"We present a comprehensive study of the modifications of Higgs couplings in the SO(5)/SO(4) minimal composite model. We focus on three couplings of central importance to Higgs phenomenology at the LHC: the couplings to top and bottom quarks and the coupling to two gluons. We consider three possible embeddings of the fermionic partners in 5, 10 and 14 of SO(5) and find tth and bbh couplings to be always suppressed in 5 and 10, while in 14 they can be either enhanced or suppressed. Assuming partial compositeness, we analyze the interplay between the tth coupling and the top sector contribution to the Coleman-Weinberg potential for the Higgs boson, and the correlation between tth and ggh couplings. In particular, if the electroweak symmetry breaking is triggered radiatively by the top sector, we demonstrate that the ratio of the tth coupling in composite Higgs models over the Standard Model expectation is preferred to be less than the corresponding ratio of the ggh coupling.",1703.07791v2 2018-11-12,Axion couplings to electroweak gauge bosons,"We determine the model-independent component of the couplings of axions to electroweak gauge bosons, induced by the minimal coupling to QCD inherent to solving the strong CP problem. The case of the invisible QCD axion is developed first, and the impact on $W$ and $Z$ axion couplings is discussed. The analysis is extended next to the generic framework of heavy true axions and low axion scales, corresponding to scenarios with enlarged confining sector. The mass dependence of the coupling of heavy axions to photons, $W$ and $Z$ bosons is determined. Furthermore, we perform a two-coupling-at-a-time phenomenological study where the gluonic coupling together with individual gauge boson couplings are considered. In this way, the regions excluded by experimental data for the axion-$WW$, axion-$ZZ$ and axion-$Z\gamma$ couplings are determined and analyzed together with the usual photonic ones. The phenomenological results apply as well to ALPs which have anomalous couplings to both QCD and the electroweak bosons.",1811.05466v1 2018-12-10,Coupled Sasaki-Ricci solitons,"Motivated by the study of coupled K\""ahler-Einstein metrics by Hultgren and Witt Nystr\""om and coupled K\""ahler-Ricci solitons by Hultgren, we study in this paper coupled Sasaki-Einstein metrics and coupled Sasaki-Ricci solitons. We first show an isomorphism between the Lie algebra of all transverse holomorphic vector fields and certain space of coupled basic functions related to coupled twisted Laplacians for basic functions, and obtain extensions of the well-known obstructions to the existence of K\""ahler-Einstein metrics to this coupled case. These results are reduced to coupled K\""ahler-Einstein metrics when the Sasaki structure is regular. Secondly we show the existence of toric coupled Sasaki-Einstein metrics when the basic first Chern class is positive extending the work of Hultgren.",1812.03784v2 2019-08-05,Tunable strong coupling of two adjacent optical λ/2 Fabry-Pérot microresonators,"Optical half-wave microresonators enable to control the optical mode density around a quantum system and thus to modify the temporal emission properties. If the coupling rate exceeds the damping rate, strong coupling between a microresonator and a quantum system can be achieved, leading to a coherent energy exchange and the creation of new hybrid modes. Here, we investigate strong coupling between two adjacent lambda/2 Fabry-P\'erot microresonators, where the resonance of one microresonator can be actively tuned across the resonance of the other microresonator. The transmission spectra of the coupled microresonators show a clear anticrossing behavior, which proves that the two cavity modes are strongly coupled. Additionally, we can vary the coupling rate by changing the resonator geometry and thereby investigate the basic principles of strong coupling with a well-defined model system. Finally, we will show that such a coupled system can theoretically be modelled by coupled damped harmonic oscillators.",1908.01566v1 2019-08-09,Coherent coupling completes an unambiguous optomechanical classification framework,"In most optomechanical systems a movable mirror is a part of an optical cavity, and its oscillation modulates either the resonance frequency of the cavity, or its coupling to the environment. There exists the third option -- which we call a ""coherent coupling"" -- when the mechanical oscillation couples several non-degenerate optical modes supported by the cavity. Identifying the nature of the coupling can be an important step in designing the setup for a specific application. In order to unambiguously distinguish between different optomechanical couplings, we develop a general framework based on the Hamiltonian of the system. Using this framework we give examples of different couplings, and discuss in details one particular case of a purely coherent coupling in a ring cavity with a movable mirror inside. We demonstrate that in certain cases coherent coupling can be beneficial for cooling the motion of the mechanical oscillator. Our general framework allows to approach the design of optomechanical experiments in a methodological way, for precise exploitation of the strengths of particular optomechanical couplings.",1908.03372v1 2018-10-08,Zeeman spin-orbit coupling in antiferromagnetic conductors,"This article is a brief review of Zeeman spin-orbit coupling, arising in a low-carrier commensurate N\'eel antiferromagnet subject to magnetic field. The field tends to lift the degeneracy of the electron spectrum. However, a hidden symmetry protects double degeneracy of Bloch eigenstates at special momenta in the Brillouin zone. The effective transverse $g$-factor vanishes at such points, thus acquiring a substantial momentum dependence, which turns a textbook Zeeman term into a spin-orbit coupling. After describing the symmetry underpinnings of the Zeeman spin-orbit coupling, I compare it with its intrinsic counterparts such as Rashba coupling, and then show how Zeeman spin-orbit coupling may survive in the presence of intrinsic spin-orbit coupling. Finally, I outline some of the likely experimental manifestations of Zeeman spin-orbit coupling, and compare it with similar phenomena in other settings such as semiconducting quantum wells.",1810.03720v1 2015-12-23,Unravelling the non-standard top and Higgs couplings in associated top-Higgs production at the High-luminosity LHC,"We study the sensitivities of non-standard top and Higgs couplings in the $pp\to thj$ process at the 14 TeV high-luminosity run of Large Hadron Collider (HL-LHC). We calculate top polarization and construct various lab-frame observables to study their sensitivities on anomalous couplings at HL-LHC. Both anomalous Wtb and hVV couplings contribute in the production process. However, only the former contributes in top decay and only the latter takes part in Higgs decay. We study this interesting interplay of couplings in the production and decay observables. In production, these couplings significantly affect the top polarization. As a measure of top polarization, we look at decay-lepton angular distributions in the laboratory frame and study the effect of anomalous couplings on these distributions. We construct certain asymmetries to study the sensitivity of these distributions to top quark couplings. In particular, real and imaginary parts of an hVV coupling and real part of a Wtb coupling f2R significantly alter the top polarization and, in turn, affect the decay-lepton distributions in laboratory frame.",1512.07408v1 2017-04-23,From discrete nonlocal nonlinear Schrödinger equation to coupled discrete Heisenberg ferromagnet equation,"In this paper, we show that the nonlocal discrete focusing nonlinear Schr\""odinger (NLS) and nonlocal discrete defocusing NLS equation are gauge equivalent to the discrete coupled Heisenberg ferromagnet (HF) equation and the discrete modified coupled HF equation, respectively. Under the continuous limit, the discrete coupled HF equation and the modified discrete coupled HF equation lead to the corresponding coupled HF equation and modified coupled HF equation. This means that the nonlocal focusing and defocusing NLS equations are gauge equivalent to the coupled HF and coupled modified HF equations. The solution of the modified coupled HF equation is obtained by using the solution of nonlocal defocusing NLS equation.",1704.06937v1 2019-07-15,Cavity mediated dissipative coupling of distant magnetic moments: theory and experiment,"We investigate long-range coherent and dissipative coupling between two spatially separated magnets while both are coupled to a microwave cavity. A careful examination of the system shows that the indirect interaction between two magnon modes is dependent on their individual mechanisms of direct coupling to the cavity. If both magnon modes share the same form of coupling to the cavity (either coherent or dissipative), then the indirect coupling between them will produce level repulsion. Conversely, if the magnon modes have different forms of coupling to the cavity (one coherent and one dissipative), then their indirect coupling will produce level attraction. We further demonstrate the cavity-mediate nature of the indirect interaction through investigating the dependence of the indirect coupling strength on the frequency detuning between the magnon and cavity modes. Our work theoretically and experimentally explores indirect cavity mediate interactions in systems exhibiting both coherent and dissipative coupling, which opens a new avenue for controlling and utilizing light-matter interactions.",1907.06783v1 2020-03-11,O-plane couplings at order $α'^2$: one R-R field strength,"It is known that the anomalous Chern-Simons (CS) coupling of O$_p$-plane is not consistent with the T-duality transformations. Compatibility of this coupling with the T-duality requires the inclusion of couplings involving one R-R field strength. In this paper we find such couplings at order $\alpha'^2$. By requiring the R-R and NS-NS gauge invariances, we first find all independent couplings at order $\alpha'^2$. There are $1,\, 6,\,28,\,20,\, 19,\, 2$ couplings corresponding to the R-R field strengths $F^{(p-4)}$, $\,F^{(p-2)}$, $\,F^{(p)}$, $\,F^{(p+2)}$, $\,F^{(p+4)}$ and $F^{(p+6)}$, respectively. We then impose the T-duality constraint on these couplings and on the CS coupling $C^{(p-3)}\wedge R\wedge R$ at order $\alpha'^2$ to fix their corresponding coefficients. The T-duality constraint fixes all coefficients in terms of the CS coefficient. They are fully consistent with the partial couplings that have been already found in the literature by the S-matrix method.",2003.05359v2 2020-11-23,Impact of Magnetic Coupling and Density on STT-MRAM Performance,"As a unique mechanism for MRAMs, magnetic coupling needs to be accounted for when designing memory arrays. This paper models both intra- and inter-cell magnetic coupling analytically for STT-MRAMs and investigates their impact on the write performance and retention of MTJ devices, which are the data-storing elements of STT-MRAMs. We present magnetic measurement data of MTJ devices with diameters ranging from 35nm to 175nm, which we use to calibrate our intra-cell magnetic coupling model. Subsequently, we extrapolate this model to study inter-cell magnetic coupling in memory arrays. We propose the inter-cell magnetic coupling factor Psi to indicate coupling strength. Our simulation results show that Psi=2% maximizes the array density under the constraint that the magnetic coupling has negligible impact on the device's performance. Higher array densities show significant variations in average switching time, especially at low switching voltages, caused by inter-cell magnetic coupling, and dependent on the data pattern in the cell's neighborhood. We also observe a marginal degradation of the data retention time under the influence of inter-cell magnetic coupling.",2011.11349v1 2021-04-23,Existence of a negative next-nearest-neighbor coupling in evanescently coupled dielectric waveguides,"We experimentally demonstrate that the next-nearest-neighbor(NNN)coupling in an array of waveguides can naturally be negative. To do so, dielectric zig-zag shaped waveguide arrays are fabricated with direct laser writing (DLW). By changing the angle of the zig-zag shape it is possible to tune between positive and negative ratios of nearest and next-nearest-neighbor coupling, which also allows to reduce the impact of the NNN-coupling to zero at the correct respective angle. We describe how the correct higher order coupling constants in tight-binding models can be derived, based on non-orthogonal coupled mode theory. We confirm the existence of negative NNN-couplings experimentally and show the improved accuracy of this refined tight-binding model. The negative NNN-coupling has a noticeable impact especially when higher order coupling terms can no longer be neglected. Our results are also of importance for other discrete systems in which the tight-binding model is often used.",2104.11711v1 2022-03-30,Resonance induced by higher-order coupling diversity,"The studies of collective oscillations induced by higher-order interactions point out the necessity of group effect in coupling modelization. As yet the related advances are mainly concentrated on nonlinear coupling patterns and cannot be straightforwardly extended to the linear ones. In present work, we introduce the standard deviation of dynamic behavior for the interacting group to complement the higher-order effect that beyond pairwise in diffusive coupling. By doing so, the higher-order effect can be flexibly extended to the linearly coupled system. We leverage this modelization to embrace the influence of heterogeneous higher-order coupling, including promoting and inhibiting effects, on the signal response for two conventional models, the globally coupled overdamped bistable oscillators and excitable FitzHugh-Nagumo neurons. Particularly, we numerically and analytically reveal that the optimal signal response can be obtained by an intermediate degree of higher-order coupling diversity for both systems. This resonant signal response stems from the competition between dispersion and aggregation induced by heterogeneous higher-order and positive pairwise couplings, respectively. Our results contribute to a better understanding of the signal propagation in linearly coupled systems.",2203.16010v1 2022-10-27,"Unified Treatment for Scattering, Absorption, and Photoluminescence of coupled Metallic Nanoparticles with Vertical Polarized Excitation","Optical properties of coupled metallic particles (MNPs) have been widely reported due to their unique characteristics such as peak shift/splitting of the coupling spectra and electromagnetic enhancement at sub-wavelength scale, etc. In a previous work, we have investigated the coupling spectra of two coupled MNPs with parallel polarized excitation. In this study, we investigate the vertical polarization case in detail. Different from the parallel one, the vertical one has its unique properties: (a) three coupling coefficients; (b) positive coupling terms in the coupling equations; (c) blue-shifts of the peaks with the increasing coupling strength for identical MNPs spectra, including scattering, absorption, and photoluminescence. Comparison with published experimental results shows the validity of this model. This work provides a deeper understanding on the optical properties of coupled MNPs and is beneficial to relevant applications.",2211.04469v1 2022-12-19,On the synchronization of the Kuramoto-type model of oscillators with lossy couplings,"We consider the problem of synchronization of coupled oscillators in a Kuramoto-type model with lossy couplings. Kuramoto models have been used to gain insight on the stability of power networks which are usually nonlinear and involve large scale interconnections. Such models commonly assume lossless couplings and Lyapunov functions have predominantly been employed to prove stability. However, coupling conductances can impact synchronization. We therefore consider a more advanced Kuramoto model that includes coupling conductances, and is characterized by nonhomogeneous coupling weights and noncomplete coupling graphs. Lyapunov analysis once such coupling conductances and aforementioned properties are included becomes nontrivial and more conventional energy-like Lyapunov functions are not applicable or are conservative. Small-signal analysis has been performed for such models, but due to the fact that we have convergence to a manifold, stability analysis via a linearization is on its own inconclusive for the nonlinear model. In this paper, we provide a formal derivation using centre manifold theory that if a particular condition on the equilibrium point associated with the coupling conductances and susceptances holds, then the synchronization manifold for the nonlinear system considered is asymptotically stable. Our analysis is demonstrated with simulations.",2212.09634v1 2023-01-27,Tunable Strong Magnon-Magnon Coupling in Two-Dimensional Array of Diamond Shaped Ferromagnetic Nanodots,"Hybrid magnonics involving coupling between magnons and different quantum particles have been extensively studied during past few years for varied interests including quantum electrodynamics. In such systems, magnons in magnetic materials with high spin density are utilized where the coupling strength is collectively enhanced by the square root of the number of spins to overcome the weaker coupling between individual spins and the microwave field. However, achievement of strong magnon-magnon coupling in a confined nanomagnets would be essential for on-chip integration of such hybrid systems. Here, through intensive study of interaction between different magnon modes in a Ni80Fe20 (Py) nanodot array, we demonstrate that the intermodal coupling can approach the strong coupling regime with coupling strength up to 0.82 GHz and cooperativity of 2.51. Micromagnetic simulations reveal that the intermodal coupling is mediated by the exchange field inside each nanodot. The coupling strength could be continuously tuned by varying the bias field strength and orientation, opening routes for external control over hybrid magnonic systems. These findings could greatly enrich the rapidly evolving field of quantum magnonics.",2301.11583v1 2023-04-26,Critical Cavity-Magnon Polariton Mediated Strong Long-Distance Spin-Spin Coupling,"Strong long-distance spin-spin coupling is desperately demanded for solid-state quantum information processing, but it is still challenged. Here, we propose a hybrid quantum system, consisting of a coplanar waveguide (CPW) resonator weakly coupled to a single nitrogen-vacancy spin in diamond and a yttrium-iron-garnet (YIG) nanosphere holding Kerr magnons, to realize strong long-distance spin-spin coupling. With a strong driving field on magnons, the Kerr effect can squeeze magnons, and thus exponentially enhance the coupling between the CPW resonator and the squeezed magnons, which produces two cavity-magnon polaritons, i.e., the high-frequency polariton (HP) and low-frequency polariton (LP). When the enhanced cavity-magnon coupling approaches to the critical value, the spin is fully decoupled from the HP, while the coupling between the spin and the LP is significantly improved. In the dispersive regime, a strong spin-spin coupling is achieved with accessible parameters, and the coupling distance can be up to $\sim$cm. Our proposal provides a promising way to manipulate remote solid spins and perform quantum information processing in weakly coupled hybrid systems.",2304.13553v2 2023-08-14,N-Body Oscillator Interactions of Higher-Order Coupling Functions,"We introduce a method to identify phase equations that include $N$-body interactions for general coupled oscillators valid far beyond the weak coupling approximation. This strategy is an extension of the theory from [Park and Wilson, SIADS 20.3 (2021)] and yields coupling functions for $N\geq2$ oscillators for arbitrary types of coupling (e.g., diffusive, gap-junction, chemical synaptic). These coupling functions enable the study of oscillator networks in terms of phase-locked states, whose stability can be determined using straightforward linear stability arguments. We demonstrate the utility of our approach with two examples. First, we use $N=3$ diffusively coupled complex Ginzburg-Landau (CGL) model and show that the loss of stability in its splay state occurs through a Hopf bifurcation \yp{as a function of non-weak diffusive coupling. Our reduction also captures asymptotic limit-cycle dynamics in the phase differences}. Second, we use $N=3$ realistic conductance-based thalamic neuron models and show that our method correctly predicts a loss in stability of a splay state for non-weak synaptic coupling. In both examples, our theory accurately captures model behaviors that weak and recent non-weak coupling theories can not.",2308.07425v2 2024-01-19,Diffusive coupling facilitates and impedes noise-induced escape in interacting bistable elements,"Diverse complex systems often undergo sudden changes in their states, such as epileptic seizures, climate changes, and social uprisings. Such behavior has been modeled by noise-induced escape of bistable elements, which is the escape from an attracting state driven by a fluctuation in the system's state. We consider a system of interacting bistable elements and investigate the effect of diffusive coupling among elements on the process of noise-induced escape. We focus on the influence of the coupling strength over the escape time, which is the time it takes for noise-induced escape to occur. We performed numerical simulations and observed that weak coupling reduced the mean escape time, whereas strong coupling impeded escape. We argue that, although diffusive coupling both facilitates and impedes escape, the facilitating effect is dominant when coupling is weak. For weak coupling cases, we develop an approximate theory that can predict the mean and variance of escape times. In contrast, strong coupling reduces the effective noise intensity to impede escape. Our results suggest that diffusive coupling among multistable elements contributes to regulating the rate of transitions among attracting states.",2401.10489v1 2024-03-27,Unveiling the inconsistency of the Proca theory with non-minimal coupling to gravity,"We study the degrees of freedom of the Proca theory, non-minimally coupled to gravity. In the Minkowski background, this theory propagates five degrees of freedom - a massive longitudinal mode, two massive vector ones, and two massless tensor modes. At first sight, the non-linear coupling between the metric perturbations and the vector field indicates that both longitudinal and tensor modes become strongly coupled, at the same scale. This would imply that no matter how small the photon mass is if non-minimal coupling is taken into account, gravitational waves would necessarily be strongly coupled. We show that the way out of this inconsistency is through the introduction of the disformal coupling to the metric perturbations that resemble the vector-type disformal transformations. This way, the unphysical coupling between the two types of modes can be avoided, rendering the model consistent. As a result, we show that only the longitudinal modes enter a strong coupling regime, while both tensor and transverse modes remain weakly coupled at all scales up to the Planck length. Finally, we show how this cures recently reported runaway modes in curved spacetime.",2403.18673v2 2012-09-04,Comment on the frozen QCD coupling,"The frozen QCD coupling is a parameter often used as an effective fixed coupling. It is supposed to mimic both the running coupling effects and the lack of knowledge of alpha_s in the infrared region. Usually the value of the frozen coupling is fixed from the analysis of the experimental data. We present a novel way to define such coupling(s) independently of the experiments. We argue that there are different frozen couplings which are used in the double- (DL) and single- logarithmic (SL) Approximations. We introduce four kinds of the frozen couplings: the coupling used in DLA with a time-like argument (i.e. the coupling present in the non-singlet scattering amplitudes and DIS structure functions) which we find 0.24 approximately; the DLA coupling with a space-like argument (in e+e- -annihilation, in DY processes and in any scattering amplitude in the hard or backward kinematics) which is a factor two larger, namely 0.48. We also show that the frozen coupling in the SL evolution equations like BFKL has to be defined in a way less accurate compared to DLA, and our estimate for this coupling is 0.1. Our estimates for the singlet and non-singlet intercepts are also in a good agreement with the results available in the literature.",1209.0564v2 2014-08-15,Influence of anomalous VVH and VVHH on determination of Higgs self couplings at ILC,"The recent discovery of a Higgs boson at LHC, while establishing the Higgs mechanism as the way of electroweak symmetry breaking, started an era of precision measurements involving the Higgs boson. In an effective Lagrangian framework, we consider the e+e- --> ZHH process, at an ILC running at a centre of mass energy of 800 GeV to investigate the effect of the ZZH and ZZHH couplings on the sensitivity of HHH coupling on this process. Our results show that the sensitivity of the trilinear Higgs self couplings on this process has somewhat strong dependence on the Higgs-gauge boson couplings. Single and two parameter reach of ILC with integrated luminosity of 1000 /fb are obtained on the effective couplings, c6 and cH, which are related to the HHH couplings, indicating how these limits are affected by the presence of anomalous ZZH and ZZHH couplings. The kinematic distributions studied to understand the effect of the anomalous couplings, again, show strong influence of Z-H couplings on the dependence of these distributions on HHH coupling. Similar results are indicated in the case of the process, e+e- --> nu nu HH, considered at a centre of mass energy of 2 TeV, where the cross section is large enough. The effect of WWH and WWHH couplings on the sensitivity of HHH coupling is clearely established through our analyses of this process.",1408.3563v2 2014-03-12,An asymptotic relationship between coupling methods for stochastically modeled population processes,"This paper is concerned with elucidating a relationship between two common coupling methods for the continuous time Markov chain models utilized in the cell biology literature. The couplings considered here are primarily used in a computational framework by providing reductions in variance for different Monte Carlo estimators, thereby allowing for significantly more accurate results for a fixed amount of computational time. Common applications of the couplings include the estimation of parametric sensitivities via finite difference methods and the estimation of expectations via multi-level Monte Carlo algorithms. While a number of coupling strategies have been proposed for the models considered here, and a number of articles have experimentally compared the different strategies, to date there has been no mathematical analysis describing the connections between them. Such analyses are critical in order to determine the best use for each. In the current paper, we show a connection between the common reaction path (CRP) method and the split coupling (SC) method, which is termed coupled finite differences (CFD) in the parametric sensitivities literature. In particular, we show that the two couplings are both limits of a third coupling strategy we call the ""local-CRP"" coupling, with the split coupling method arising as a key parameter goes to infinity, and the common reaction path coupling arising as the same parameter goes to zero. The analysis helps explain why the split coupling method often provides a lower variance than does the common reaction path method, a fact previously shown experimentally.",1403.3127v2 2013-09-12,Energy-Efficient and Robust Associative Computing with Electrically Coupled Dual Pillar Spin-Torque Oscillators,"Dynamics of coupled spin-torque oscillators can be exploited for non-Boolean information processing. However, the feasibility of coupling large number of STOs with energy-efficiency and sufficient robustness towards parameter-variation and thermal-noise, may be critical for such computing applications. In this work, the impacts of parameter-variation and thermal-noise on two different coupling mechanisms for STOs, namely, magnetic-coupling and electrical-coupling are analyzed. Magnetic coupling is simulated using dipolar-field interactions. For electricalcoupling we employed global RF-injection. In this method, multiple STOs are phase-locked to a common RF-signal that is injected into the STOs along with the DC bias. Results for variation and noise analysis indicate that electrical-coupling can be significantly more robust as compared to magnetic-coupling. For room-temperature simulations, appreciable phase-lock was retained among tens of electrically coupled STOs for up to 20% 3s random variations in critical device parameters. The magnetic-coupling technique however failed to retain locking beyond ~3% 3s parameter-variations, even for small-size STO clusters with near-neighborhood connectivity. We propose and analyze Dual-Pillar STO (DP-STO) for low-power computing using the proposed electrical coupling method. We observed that DP-STO can better exploit the electrical-coupling technique due to separation between the biasing RF signal and its own RF output.",1309.3306v1 2017-05-16,Coupling conditions for globally stable and robust synchrony of chaotic systems,"We propose a set of general coupling conditions to select a coupling profile (a set of coupling matrices) from the linear flow matrix (LFM) of dynamical systems for realizing global stability of complete synchronization (CS) in identical systems and robustness to parameter perturbation. The coupling matrices define the coupling links between any two oscillators in a network that consists of a conventional diffusive coupling link (self-coupling link) as well as a cross-coupling link. The addition of a selective cross-coupling link in particular plays constructive roles that ensure the global stability of synchrony and furthermore enables robustness of synchrony against small to non-small parameter perturbation. We elaborate the general conditions for the selection of coupling profiles for two coupled systems, three- and four-node network motifs analytically as well as numerically using benchmark models, the Lorenz system, the Hindmarsh-Rose neuron model, the Shimizu-Morioka laser model, the R\""ossler system and a Sprott system. The role of the cross-coupling link is, particularly, exemplified with an example of a larger network where it saves the network from a breakdown of synchrony against large parameter perturbation in any node. The perturbed node in the network transits from CS to generalized synchronization (GS) when all the other nodes remain in CS. The GS is manifested by an amplified response of the perturbed node in a coherent state.",1705.05912v1 2018-12-15,Breaking the bonds of weak coupling: the dynamic causal modelling of oscillator amplitudes,"Models of coupled oscillators are useful in describing a wide variety of phenomena in physics, biology and economics. These models typically rest on the premise that the oscillators are weakly coupled, meaning that amplitudes can be assumed to be constant and dynamics can therefore be described purely in terms of phase differences. Whilst mathematically convenient, the restrictive nature of the weak coupling assumption can limit the explanatory power of these phase-coupled oscillator models. We therefore propose an extension to the weakly-coupled oscillator model that incorporates both amplitude and phase as dependent variables. We use the bilinear neuronal state equations of dynamic causal modelling as a foundation in deriving coupled differential equations that describe the activity of both weakly and strongly coupled oscillators. We show that weakly-coupled oscillator models are inadequate in describing the processes underlying the temporally variable signals observed in a variety of systems. We demonstrate that phase-coupled models perform well on simulations of weakly coupled systems but fail when connectivity is no longer weak. On the other hand, using Bayesian model selection, we show that our phase-amplitude coupling model can describe non-weakly coupled systems more effectively despite the added complexity associated with using amplitude as an extra dependent variable. We demonstrate the advantage of our phase-amplitude model in the context of model-generated data, as well as of a simulation of inter-connected pendula, neural local field potential recordings in rodents under anaesthesia and international economic gross domestic product data.",1812.06315v1 2020-01-07,Switching dynamics of single and coupled VO2-based oscillators as elements of neural networks,"In the present paper, we report on the switching dynamics of both single and coupled VO2-based oscillators, with resistive and capacitive coupling, and explore the capability of their application in oscillatory neural networks. Based on these results, we further select an adequate SPICE model to describe the modes of operation of coupled oscillator circuits. Physical mechanisms influencing the time of forward and reverse electrical switching, that determine the applicability limits of the proposed model, are identified. For the resistive coupling, it is shown that synchronization takes place at a certain value of the coupling resistance, though it is unstable and a synchronization failure occurs periodically. For the capacitive coupling, two synchronization modes, with weak and strong coupling, are found. The transition between these modes is accompanied by chaotic oscillations. A decrease in the width of the spectrum harmonics in the weak-coupling mode, and its increase in the strong-coupling one, is detected. The dependences of frequencies and phase differences of the coupled oscillatory circuits on the coupling capacitance are found. Examples of operation of coupled VO2 oscillators as a central pattern generator are demonstrated.",2001.01854v1 2020-07-13,"Modeling Nonlocal Electron-Phonon Coupling in Organic Crystals Using Interpolative Maps: The Spectroscopy of Crystalline Pentacene and 7,8,15,16-Tetraazaterrylene","Electron-phonon coupling plays a central role in the transport properties and photophysics of organic crystals. Successful models describing charge- and energy-transport in these systems routinely include these effects. Most models for describing photophysics, on the other hand, only incorporate local electron-phonon coupling to intramolecular vibrational modes, while nonlocal electron-phonon coupling is neglected. One might expect nonlocal coupling to have an important effect on the photophysics of organic crystals, because it gives rise to large fluctuation in the charge-transfer couplings, and charge-transfer couplings play an important role in the spectroscopy of many organic crystals. Here, we study the effects of nonlocal coupling on the absorption spectrum of crystalline pentacene and 7,8,15,16-tetraazaterrylene. To this end, we develop a new mixed quantum-classical approach for including nonlocal coupling into spectroscopic and transport models for organic crystals. Importantly, our approach does not assume that the nonlocal coupling is linear, in contrast to most modern charge-transport models. We find that the nonlocal coupling broadens the absorption spectrum non-uniformly across the absorption line shape. In pentacene, for example, our model predicts that the lower Davydov component broadens considerably more than the upper Davydov component, explaining the origin of this experimental observation for the first time. By studying a simple dimer model, we are able to attribute this selective broadening to correlations between the fluctuations of the charge-transfer couplings. Overall, our method incorporates nonlocal electron-phonon coupling into spectroscopic and transport models with computational efficiency, generalizability to a wide range of organic crystals, and without any assumption of linearity.",2007.06729v2 2022-08-22,Coherence behavior of strongly coupled bosonic modes,"We study the effect of the intermode coupling in the generation of coherence when two bosonic modes are bilinearly coupled. We consider the case for which the two modes are weakly coupled and the rotating-wave approximation (RWA) applies and the case for which they are strongly coupled and the (RWA) does not apply. Then, in the regime of validity of (RWA), there is no coherence generation solely due to squeezing effects, which means there is an exchange of excitation between the modes and negligible squeezing. On the other hand, if the two modes are strongly coupled coherence is generated by the squeezing interaction. For the system of two bosonic modes weakly coupled with a Markovian bath at temperature $T$ the coherence decreases with $T$. In general, when both kinds of couplings (exchange of excitation and squeezing) are turned on the exchange of excitation contributes to generating more coherence in comparison with a purely squeezing coupling. Thus, the coherence decreases more slowly with the temperature when both couplings are present. Finally, we explore the case when only one of the two coupled modes interacts with a Markovian bath while the other one remains free from the environment. We observe that the intermode coupling induces oscillations in the coherence and fidelity dynamics similar to the behavior for the coupling with a non-Markovian environment.",2208.10649v1 2016-07-12,Coupling proofs are probabilistic product programs,"Couplings are a powerful mathematical tool for reasoning about pairs of probabilistic processes. Recent developments in formal verification identify a close connection between couplings and pRHL, a relational program logic motivated by applications to provable security, enabling formal construction of couplings from the probability theory literature. However, existing work using pRHL merely shows existence of a coupling and does not give a way to prove quantitative properties about the coupling, which are need to reason about mixing and convergence of probabilistic processes. Furthermore, pRHL is inherently incomplete, and is not able to capture some advanced forms of couplings such as shift couplings. We address both problems as follows. First, we define an extension of pRHL, called xpRHL, which explicitly constructs the coupling in a pRHL derivation in the form of a probabilistic product program that simulates two correlated runs of the original program. Existing verification tools for probabilistic programs can then be directly applied to the probabilistic product to prove quantitative properties of the coupling. Second, we equip pRHL with a new rule for while loops, where reasoning can freely mix synchronized and unsynchronized loop iterations. Our proof rule can capture examples of shift couplings, and the logic is relatively complete for deterministic programs. We show soundness of xpRHL and use it to analyze two classes of examples. First, we verify rapid mixing using different tools from coupling: standard coupling, shift coupling, and path coupling, a compositional principle for combining local couplings into a global coupling. Second, we verify (approximate) equivalence between a source and an optimized program for several instances of loop optimizations from the literature.",1607.03455v5 1994-05-15,Globally Coupled Maps: Almost Analytical Treatment of Phase Transitions,"Bifurcations in a system of coupled maps are investigated. Using symbolic dynamics it is proven that for coupled shift maps the well known space--time--mixing attractor becomes unstable at a critical coupling strength in favour of a synchronized state. For coupled non--hyperbolic maps analytical and numerical evidence is given that arbitrary small coupling changes the dynamical behaviour. The anomalous dependence of fluctuations on the system size is attributed to these bifurcations.",9405008v1 1997-03-26,On the Collective Motion in Globally Coupled Chaotic Systems,"A mean-field formulation is used to investigate the bifurcation diagram for globally coupled tent maps by means of an analytical approach. It is shown that the period doubling sequence of the single site map induces a continuous family of periodic states in the coupled system. This type of collective motion breaks the ergodicity of the coupled map lattice. The stability analysis suggests that these states are stable for weak coupling strength but opens the possibility for more complicated types of motion in the regime of moderate coupling.",9703017v1 1998-07-27,Renormalization analysis of intermittency in two coupled maps,"The critical behavior for intermittency is studied in two coupled one-dimensional (1D) maps. We find two fixed maps of an approximate renormalization operator in the space of coupled maps. Each fixed map has a common relavant eigenvaule associated with the scaling of the control parameter of the uncoupled one-dimensional map. However, the relevant ``coupling eigenvalue'' associated with coupling perturbation varies depending on the fixed maps. These renormalization results are also confirmed for a linearly-coupled case.",9807036v1 1993-11-08,Universality of Period Doubling in Coupled Maps,"We study the critical behavior of period doubling in two coupled one-dimensional maps with a single maximum of order $z$. In particurlar, the effect of the maximum-order $z$ on the critical behavior associated with coupling is investigated by a renormalization method. There exist three fixed maps of the period-doubling renormalization operator. For a fixed map associated with the critical behavior at the zero-coupling critical point, relevant eigenvalues associated with coupling perturbations vary depending on the order $z$, whereas they are independent of $z$ for the other two fixed maps. The renormalization results for the zero-coupling case are also confirmed by a direct numerical method.",9311014v1 1995-06-22,Weak-Coupling Approach to Hole-Doped S=1 Haldane Systems,"As a weak-coupling analogue of hole-doped $S=1$ Haldane systems, we study two models for coupled chains via Hund coupling; coupled Hubbard chains, and a Hubbard chain coupled with an $S=1/2$ Heisenberg chain. The fixed point properties of these models are investigated by using bosonization and renormalization group methods. The effect of randomness on these fixed points is also studied. It is found that the presence of the disorder parameter inherent in the Haldane state in the former model suppresses the Anderson localization for weak randomness, and stabilizes the Tomonaga-Luttinger liquid state with the spin gap.",9506118v1 1998-02-27,Noise Effects on Synchronized Globally Coupled Oscillators,"The synchronized phase of globally coupled nonlinear oscillators subject to noise fluctuations is studied by means of a new analytical approach able to tackle general couplings, nonlinearities, and noise temporal correlations. Our results show that the interplay between coupling and noise modifies the effective frequency of the system in a non trivial way. Whereas for linear couplings the effect of noise is always to increase the effective frequency, for nonlinear couplings the noise influence is shown to be positive or negative depending on the problem parameters. Possible experimental verification of the results is discussed.",9802300v1 2000-04-13,Laterally coupled few-electron quantum dots,"We present ground-state calculations for laterally coupled quantum dots containing 2, 4, and 8 electrons. As our emphasis is on spin effects our results are obtained by applying spin-density functional theory (SDFT). By varying the distance between the centers of the coupled quantum dots, the transition from weak to strong coupling situation is realized. For the 2-electron system we also apply the Heitler-London approximation and analytical concepts to check the reliability of SDFT calculations in this case. In addition we discuss the features of the Coulomb staircase of laterally coupled quantum dots in the weak and strong coupling regimes in comparison to that of a circular parabolic quantum dot.",0004209v1 2002-09-12,Coupling parameter in synchronization of diluted neural networks,"We study the critical features of coupling parameter in the synchronization of neural networks with diluted synapses. Based on simulations, the exponential decay form is observed in the extreme case of global coupling among subsystems and fully linking in each network: there exists maximum and minimum of the critical coupling intensity for synchronization in this spatially extended system. For the partial coupling, we present the primary result about the critical coupling fraction for various linking degrees of networks.",0209293v1 2003-09-23,Persistent current in a ring coupled to an external fermionic reservoir,"We study the energy spectrum and the persistent current in an ideal one-dimensional mesoscopic ring coupled to a fermionic reservoir. We find that the tunnel coupling in general leads to the suppression of the persistent current. However, with increasing coupling, the effective level structure of the ring coupled to the reservoir changes and quasistates with a sharp eigenenergy develop. Depending on the number of ring states coupled to the reservoir this results in a nonzero persistent current even at very large tunneling between the ring and the reservoir.",0309527v1 2003-11-24,Coupling theory for counterion distributions based in Tsallis statistics,"It is well known that the Poisson-Boltzmann (PB) equation yields the exact counterion density around charged objects in the weak coupling limit. In this paper we generalize the PB approach to account for coupling of arbitrary strength by making use of Tsallis q-exponential distributions. Both the weak coupling and the strong coupling limits are reproduced. For arbitrary coupling we also provide simple analytical expressions which are compared to recent Monte Carlo simulations by A. G. Moreira and R. R. Netz [Europhys. Lett. 52 (2000) 705]. Excellent agreement with these is obtained.",0311546v2 2004-02-16,Selfduality for coupled Potts models on the triangular lattice,"We present selfdual manifolds for coupled Potts models on the triangular lattice. We exploit two different techniques: duality followed by decimation, and mapping to a related loop model. The latter technique is found to be superior, and it allows to include three-spin couplings. Starting from three coupled models, such couplings are necessary for generating selfdual solutions. A numerical study of the case of two coupled models leads to the identification of novel critical points.",0402420v1 2007-01-31,Coupled spin-charge drift-diffusion approach for a two-dimensional electron gas with Rashba spin-orbit coupling,"Based on kinetic equations for the density matrix, drift-diffusion equations are derived for a two-dimensional electron gas with Rashba spin-orbit coupling. Universal results are obtained for the weak coupling case. Most interesting is the observation that with increasing spin-orbit coupling strengths there is a sharp transition between spin diffusion and ballistic spin transport. For strong spin-orbit coupling, when the elastic scattering time is much larger than the spin relaxation time, undamped spin-coherent waves are identified. The existence of these long-lived spin-coherent states is confirmed by exact analytical results obtained from microscopic kinetic equations valid in the ballistic regime.",0701782v1 2007-02-26,Switchable coupling for superconducting qubits using double resonance in the presence of crosstalk,"Several methods have been proposed recently to achieve switchable coupling between superconducting qubits. We discuss some of the main considerations regarding the feasibility of implementing one of those proposals: the double-resonance method. We analyze mainly issues related to the achievable effective coupling strength and the effects of crosstalk on this coupling approach. We also find a new, crosstalk-assisted coupling channel that can be an attractive alternative when implementing the double-resonance coupling proposal.",0702603v3 2005-09-16,Isotropisation of flat homogeneous Bianchi type I model with a non minimally coupled and massive scalar field,"In previous works, we studied the isotropisation of Bianchi class A models with a minimally coupled scalar field. In this paper, we extend these results to the case of a non minimally coupled one. We first make the calculations in the Einstein frame where the scalar field is minimally coupled to the curvature but non minimally coupled to the perfect fluid. Then, we use a conformal transformation to generalise our results to a scalar field non minimally coupled to the curvature. Universe isotropisation for the Brans-Dicke and low energy string theories are studied.",0509070v1 2003-05-13,Measurement of gauge boson couplings and W spin density matrix,"During the LEP2 period the e+e- collider increased its center of mass energy from 161 GeV to 209 GeV and a total integrated luminosity of approximately 700 pb-1 was recorded per experiment. Pairs of W bosons are produced and allow the study of gauge boson couplings involving W, Z and photon. The coupling of the W boson to the neutral gauge bosons have been measured and are in agreement with the Standard Model prediction. Limits are set on CP-violating couplings by a Spin Density Matrix analysis of the W decay products. No evidence has been found for couplings of three neutral gauge bosons. Limits are derived on couplings of four gauge bosons.",0305025v1 2004-09-28,Strong coupling analysis of diquark condensation,"The phenomenon of diquark condensation at non-zero baryon density and zero temperature is analyzed in the strong coupling limit of lattice QCD. The results indicate that there is attraction in the quark-quark channel also at strong coupling, and that the attraction is more effective at high baryon density, but for infinite coupling it is not enough to produce diquark condensation. It is argued that the absence of diquark condensation is not a peculiarity of the strong coupling limit, but persists at sufficiently large finite couplings.",0409159v1 1993-07-11,Light Quark Spin-Flavor Symmetry for Baryons Containing a Heavy Quark in Large N QCD,"The couplings and interactions of baryons containing a heavy quark are related by light quark spin-flavor symmetry in the large $N$ limit. The single pion coupling constant which determines all heavy quark baryon-pion couplings is equal to the pion coupling constant for light quark baryons. Light quark symmetry relations amongst the baryon couplings are violated at order $1/N^2$. Heavy quark spin-flavor symmetry is used in conjunction with large $N$ light quark spin-flavor symmetry to determine the couplings of the degenerate doublets of heavy quark baryons.",9307243v1 1994-06-07,Minimal String Unification and Yukawa Couplings in Orbifold Models,"We study the minimal supersymmetric standard model derived from $Z_N \times Z_M$ orbifold models. Moduli dependent threshold corrections of the gauge couplings are investigated to explain the measured values of the coupling constants. Also we study Yukawa couplings of the models. We find that the $Z_2 \times Z_6'$, $Z_2\times Z_6$, $Z_3 \times Z_6$ and $Z_6 \times Z_6$ orbifold models have the possibility to derive Yukawa couplings for the second and third generations as well as the measured gauge coupling constants. Allowed models are shown explicitly by combinations of modular weights for the matter fields.",9406238v1 2000-09-06,Infrared Fixed Points and Fixed Lines for Couplings in the Chiral Lagrangian,"In the framework of the low energy chiral Lagrangian renormalization group equations for the couplings are investigated up to order p^6 -- as well for SU(2)xSU(2) as for SU(3)xSU(3) chiral symmetry. Infrared attractive fixed points for ratios of O(p^4) couplings are found, which turn out to agree with the values determined from experiment in a surprisingly large number of cases. Infrared attractive fixed line solutions for O(p^6) couplings in terms of O(p^4) couplings and among O(p^6) couplings are determined.",0009069v2 2006-01-19,Secondary particles spectra in the decay of a polarized top quark with anomalous $tWb$ coupling,"Analytic expression for energy and angular dependence of a secondary charged lepton in the decay of a polarized top quark with anomalous $tWb$ couplings in the presence of all anomalous couplings are derived. The angular distribution of the b-quark is derived as well. It is presented that the charged lepton spin correlation coefficient is not very sensitive to the anomalous couplings. However, the b-quark spin correlation coefficient is sensitive to anomalous couplings and could be used as a powerful tool for searching of non-SM coupling.",0601155v3 2006-06-09,Determining the SUSY-QCD Yukawa Coupling,"Among the firm predictions of softly broken supersymmetry is the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions. In the event that a SUSY-like spectrum of new particles is discovered at future colliders, a key follow-up will be to test these relations experimentally. In detailed studies it has been found that the SUSY-Yukawa couplings of the electroweak sector can be studied with great precision at the ILC, but a similar analysis for the Yukawa coupling of the SUSY-QCD sector is far more challenging. Here a first phenomenological study for determining this coupling is presented, using a method which combines information from LHC and ILC.",0606121v1 2000-12-18,Reduction of Coupling Parameters in Quantum Field Theories,"A concise survey is given of the general method of reduction in the number of coupling parameters. Theories with several independent couplings are related to a set of theories with a single coupling. The reduced theories may or may not have particular symmetries. A few have asymptotic power series expansions, others contain non-integer powers and/or logarithmic factors. An example is given with two power series solutions, one with N = 2 Supersymmetry, and one with no known symmetry. In a second example, the reduced Yukawa coupling of the superpotential in a dual magnetic supersymmetric gauge theory is uniquely given by the square of the magnetic gauge coupling with a known factor.",0012162v1 2005-12-12,K-divisibility constants for some special couples,"We prove new estimates of the $K$-divisibility constants for some special Banach couples. In particular, we prove that the $K$-divisibility constant for a couple of the form $(U\oplus V, U)$ where $U$ and $V$ are non-trivial Hilbert spaces equals $2/\sqrt{3}$. We also prove estimates for the $K$-divisibility constant of the two-dimensional version of the couple $(L_2,L_\infty)$, proving in particular that this couple is not exactly $K$-divisible. There are also several auxiliary results, including some estimates for relative Calder\'on constants for finite dimensional couples.",0512234v2 2006-09-20,Mixing times via super-fast coupling,"We provide a coupling proof that the transposition shuffle on a deck of n cards is mixing of rate Cn(log{n}) with a moderate constant, C. This rate was determined by Diaconis and Shahshahani, but the question of a natural probabilistic coupling proof has been missing, and questions of its existence have been raised. The proof, and indeed any proof, requires that we enlarge the methodology of coupling to include intuitive but non-adapted coupling rules, because a typical Markovian coupling is incapable of resolving finer questions of rates.",0609568v3 2007-01-13,On uniqueness of maximal coupling for diffusion processes with a reflection,"A maximal coupling of two diffusion processes makes two diffusion particles meet as early as possible. We study the uniqueness of maximal couplings under a sort of ""reflection structure"" which ensures the existence of such couplings. In this framework, the uniqueness in the class of Markovian couplings holds for the Brownian motion on a Riemannian manifold whereas it fails in more singular cases. We also prove that a Kendall-Cranston coupling is maximal under the reflection structure.",0701372v1 2004-09-21,Global Analysis of Synchronization in Coupled Maps,"We introduce a new method for determining the global stability of synchronization in systems of coupled identical maps. The method is based on the study of invariant measures. Besides the simplest non-trivial example, namely two symmetrically coupled tent maps, we also treat the case of two asymmetrically coupled tent maps as well as a globally coupled network. Our main result is the identification of the precise value of the coupling parameter where the synchronizing and desynchronizing transitions take place.",0409043v2 2006-10-06,Synchronization in semiconductor laser rings,"We examine the dynamics of semiconductor lasers coupled in a ring configuration. The lasers, which have stable output intensity when isolated, behave chaotically when coupled unidirectionally in a closed chain. In this way, we show that neither feedback nor bidirectional coupling is necessary to induce chaotic dynamics at the laser output. We study the synchronization phenomena arising in this particular coupling architecture, and discuss its possible application to chaos-based communications. Next, we extend the study to bidirectional coupling and propose an appropriate technique to optical chaos encryption/decryption in closed chains of mutually coupled semiconductor lasers.",0610014v1 2002-09-02,A Systematic Investigation of Light Heavy-Ion Reactions,"We introduce a novel coupling potential for the scattering of deformed light heavy-ion reactions. This new approach is based on replacing the usual first-derivative coupling potential by a new, second derivative coupling potential in the coupled-channels formalism. The new approach has been successfully applied to the study of the $^{12}$C+$^{12}$C, $^{12}$C+$^{24}$Mg, $^{16}$O+$^{28}$Si and $^{16}$O+$^{24}$Mg systems and made major improvements over all the previous coupled-channels calculations for these systems. This paper also shows the limitations of the standard coupled-channels theory and presents a global solution to the problems faced in the previous theoretical accounts of these reactions.",0209006v1 2003-10-30,Coupled cluster calculations of ground and excited states of nuclei,"The standard and renormalized coupled cluster methods with singles, doubles, and noniterative triples and their generalizations to excited states, based on the equation of motion coupled cluster approach, are applied to the He-4 and O-16 nuclei. A comparison of coupled cluster results with the results of the exact diagonalization of the Hamiltonian in the same model space shows that the quantum chemistry inspired coupled cluster approximations provide an excellent description of ground and excited states of nuclei. The bulk of the correlation effects is obtained at the coupled cluster singles and doubles level. Triples, treated noniteratively, provide the virtually exact description.",0310082v1 1999-10-25,Analyzing symmetry breaking within a chaotic quantum system via Bayesian inference,"Bayesian inference is applied to the level fluctuations of two coupled microwave billiards in order to extract the coupling strength. The coupled resonators provide a model of a chaotic quantum system containing two coupled symmetry classes of levels. The number variance is used to quantify the level fluctuations as a function of the coupling and to construct the conditional probability distribution of the data. The prior distribution of the coupling parameter is obtained from an invariance argument on the entropy of the posterior distribution.",9910035v1 2002-01-04,Coupled multi-component systems: A Simple Membrane Model,"We present initial results regarding the existence, stability and interaction of linear and nonlinear vibrational modes in a system of two coupled, one dimensional lattices with unequal numbers of masses. The effects on these nonlinear modes of coupling a near continuum system to a discrete system using a nonlinear coupling are examined. This numerical model is a first step towards investigating the dynamical behavior of a flexible sheet coupled nonlinearly to a semi-rigid support, a system which could conceivably represent a biological cell membrane with a supporting protein network. General implications for the dynamical behavior of continuum systems coupled nonlinearly to discrete systems are introduced.",0201005v1 1999-12-03,Integrable Couplings of Soliton Equations by Perturbations I. A General Theory and Application to the KdV Hierarchy,"A theory for constructing integrable couplings of soliton equations is developed by using various perturbations around solutions of perturbed soliton equations being analytic with respect to a small perturbation parameter. Multi-scale perturbations can be taken and thus higher dimensional integrable couplings can be presented. The theory is applied to the KdV soliton hierarchy. Infinitely many integrable couplings are constructed for each soliton equation in the KdV hierarchy, which contain integrable couplings possessing quadruple Hamiltonian formulations and two classes of hereditary recursion operators, and integrable couplings possessing local 2+1 dimensional bi-Hamiltonian formulations and consequent 2+1 dimensional hereditary recursion operators.",9912004v1 2007-07-27,Persistent Current in Two Coupled Rings,"We report the solution of the persistent current in two coupled rings in the presence of external magnetic fluxes. We showed that the magnetic fluxes modify the global phase of the electronic wave function for multiple connected geometry formed by the coupled rings. We obtained an exact solution for the persistent current and investigated the exact solution numerically. For two large coupled rings with equal fluxes, we found that the persistent current in the two coupled rings is in fact equal to that in a single ring. This theory explains the experimental results observed in a line of sixteen coupled rings. (Phys. Rev. Lett. 86, 3124 (2001).)",0707.4041v1 2008-03-08,Resonance Clustering in Globally Coupled Electrochemical Oscillators with External Forcing,"Experiments are carried out with a globally coupled, externally forced population of limit-cycle electrochemical oscillators with an approximately unimodal distribution of heterogeneities. Global coupling induces mutually entrained (at frequency $\omega_{1}$) states; periodic forcing produces forced-entrained ($\omega_{\mathrm{F}}$) states. As a result of the interaction of mutual and forced entrainment, resonant cluster states occur with equal spacing of frequencies that have discretized frequencies following a resonance rule $\omega_{n}\cong n\omega_{1}-(n-1)\omega_{\mathrm{F}}$. Resonance clustering requires an optimal, intermediate global coupling strength; at weak coupling the clusters have smaller sizes and do not strictly follow the resonance rule, while at strong coupling the population behaves similar to a single, giant oscillator.",0803.1204v1 2008-05-28,Numerical Study of Energy Loss by a Nanomechanical Oscillator Coupled to a Cooper Pair Box,"We calculate the dynamics of a nanomechanical oscillator (NMO) coupled capacitively to a Cooper pair box (CPB), by solving a stochastic Schrodinger equation with two Lindblad operators. Both the NMO and the CPB are assumed dissipative, and the coupling is treated within the rotating wave approximation. We show numerically that, if the CPB decay time is smaller than the NMO decay time, the coupled NMO will lose energy faster, and the coupled CPB more slowly, than do the uncoupled NMO and CPB. The results show that the efficiency of energy loss by an NMO can be substantially increased if the NMO is coupled to a CPB.",0805.4401v1 2008-09-16,High energy scattering in the saturation regime including running coupling and rare fluctuation effects,"The analytic result for the $S$-matrix in the saturation regime including the running coupling is obtained. To get this result we solve the Balitsky and Kovchegov-Weigert evolution equations in the saturation regime, which include running coupling corrections. We study also the effect of rare fluctuations on top of the running coupling. We find that the rare fluctuations are less important in the running coupling case as compared to the fixed coupling case.",0809.2666v1 2008-11-20,Interlayer exchange coupling in Co2FeAl0.5Si0.5/Cr/Co2FeAl0.5Si0.5 trilayers,"Interlayer exchange couplings were examined for Co2FeAl0.5Si0.5(CFAS)/Cr/CFAS trilayered films grown on MgO (001) single crystal and thermally oxidized Si substrates. The films were (001) epitaxial on MgO and (110) textured polycrystalline on SiO2. Strong exchange couplings were observed for the films with the 1.5 nm thick Cr spacer layer. A 90 degree coupling is dominant in the (001) epitaxial film. In contrast, an antiparallel coupling exists in the polycrystalline one. The relationship of interlayer couplings with the structure is discussed.",0811.3278v1 2008-12-31,Search for anomalous top quark couplings with the D0 detector,"Anomalous Wtb couplings modify the angular correlations of the top quark decay products and change the single top quark production cross section. We present limits on anomalous top quark couplings by combining information from W boson helicity measurements in top quark decays and anomalous coupling searches in the single top quark final state. We set limits on right-handed vector couplings as well as left-handed and right-handed tensor couplings based on about 1fb^-1 of data collected by the D0 experiment.",0901.0151v1 2010-02-15,Reactive-Coupling-Induced Normal Mode Splittings in Microdisk Resonators Coupled to Waveguides,"We study the optomechanical design introduced by M. Li et al. [Phys. Rev. Lett. {\bf 103}, 223901 (2009)], which is very effective for investigation of the effects of reactive coupling. We show the normal mode splitting which is due solely to reactive coupling rather than due to dispersive coupling. We suggest feeding the waveguide with a pump field along with a probe field and scanning the output probe for evidence of reactive-coupling-induced normal mode splitting.",1002.2914v2 2010-08-04,Plasmon-phonon coupling in graphene,"Collective excitations of coupled electron-phonon systems are calculated for both monolayer and bilayer graphene, taking into account the non-perturbative Coulomb coupling between electronic excitations in graphene and the substrate longitudinal optical phonon modes. We find that the plasmon-phonon coupling in monolayer graphene is strong at all densities, but in bilayer graphene the coupling is significant only at high densities satisfying the resonant condition $\omega_{pl} \approx \omega_{ph}$. The difference arises from the peculiar screening properties associated with chirality of graphene. Plasmon-phonon coupling explains the measured quasi-linear plasmon dispersion in the long wavelength limit, thus resolving a puzzle in the experimental observations.",1008.0862v1 2010-11-21,Creating very slow optical gap solitons with inter-fiber coupling,"We show that gap-acoustic solitons, i.e., optical gap solitons with electrostrictive coupling to sound modes, can be produced with velocities down to less than 2.5% of the speed of light using a fiber Bragg grating that is linearly coupled to a non-Bragg fiber over a finite domain. Forward- and backward-moving light pulses in the non-Bragg fiber that reach the coupling region simultaneously couple into the Bragg fiber and form a moving soliton, which then propagates beyond the coupling region.",1011.4668v1 2010-12-08,Global stability of synchronous and out-of-phase oscillations in central pattern generators,"Coupled arrays of Andronov-Hopf oscillators are investigated. These arrays can be diffusively or repulsively coupled, and can serve as central pattern generator models in animal locomotion and robotics. It is shown that repulsive coupling generates out-of-phase oscillations, while diffusive coupling generates synchronous oscillations. Specifically, symmetric solutions and their corresponding amplitudes are derived, and contraction analysis is used to prove global stability and convergence of oscillations to either symmetric out-of-phase or synchronous states, depending on the coupling constant. Next, the two mechanisms are used jointly by coupling multiple arrays. The resulting dynamics is analyzed, in a model inspired by the CPG-motorneuron network that controls the heartbeat of a medicinal leech.",1012.1788v1 2011-02-27,Towards extending the Chern-Simons couplings at order $O(α'^2)$,"Using the compatibility of the anomalous Chern-Simons couplings on D$_p$-branes with the linear T-duality and with the antisymmetric B-field gauge transformations, some couplings have been recently found for $C^{(p-3)}$ at order $O(\alpha'^2)$. We examine these couplings with the S-matrix element of one RR and two antisymmetric B-field vertex operators. We find that the S-matrix element reproduces these couplings as well as some other couplings. Each of them is invariant under the linear T-duality and the B-field gauge transformations.",1102.5510v2 2011-09-26,Inverse Ising problem for one-dimensional chains with arbitrary finite-range couplings,"We study Ising chains with arbitrary multispin finite-range couplings, providing an explicit solution of the associated inverse Ising problem, i.e. the problem of inferring the values of the coupling constants from the correlation functions. As an application, we reconstruct the couplings of chain Ising Hamiltonians having exponential or power-law two-spin plus three- or four-spin couplings. The generalization of the method to ladders and to Ising systems where a mean-field interaction is added to general finite-range couplings is as well as discussed.",1109.5529v2 2011-10-03,Diagnostics of plasma photoemission at strong coupling,"We compute the spectrum of photons emitted by the finite-temperature large-N SU(N) ${\cal {N}}=4$ supersymmetric Yang-Mills plasma coupled to electromagnetism, at strong yet finite 't Hooft coupling. We work in the holographic dual description, extended by the inclusion of the full set of ${\cal{O}}(\alpha'^3)$ type IIB string theory operators that correct the minimal supergravity action. We find that, as the t' Hooft coupling decreases, the peak of the spectrum increases, and the momentum of maximal emission shifts towards the infra-red, as expected from weak-coupling computations. The total number of emitted photons also increases as the 't Hooft coupling weakens.",1110.0526v1 2012-06-08,Synchronization of globally coupled two-state stochastic oscillators with a state dependent refractory period,"We present a model of identical coupled two-state stochastic units each of which in isolation is governed by a fixed refractory period. The nonlinear coupling between units directly affects the refractory period, which now depends on the global state of the system and can therefore itself become time dependent. At weak coupling the array settles into a quiescent stationary state. Increasing coupling strength leads to a saddle node bifurcation, beyond which the quiescent state coexists with a stable limit cycle of nonlinear coherent oscillations. We explicitly determine the critical coupling constant for this transition.",1206.1664v1 2012-11-29,Possible Manipulation of Kondo Effect by Transition between Antiferromagnetic and Ferromagnetic s-d Coupling,"Kondo effect originates from antiferromagnetic (AFM) s-d coupling between magnetic impurity and the conduction electron, while it will be totally quenched in ferromagnetic (FM) regime due to malfunction of spin-flip. We investigate the possibility of switching on/off Kondo effect by transition of AFM/FM s-d coupling using 3d-metal phthalocyanine molecule (MPc) on Au(111) as a model system. A Hamiltonian model is constructed based on the feature of MPc molecule to show the condition for AFM/FM s-d coupling. The AFM s-d coupling could transform to FM s-d coupling if the spin state of the lowest unoccupied orbital changes.",1211.6955v1 2013-04-29,Multi-matrix models at general coupling,"The eigenvalue distribution of Hoppe's two matrix model is investigated in detail as a function of the model's coupling. For small couplings it is a perturbed Wigner semicircle, while for large couplings it is a parabolic distribution which crosses over to a Wigner semicircle for eigenvalues within approximatley an inverse coupling from the boundary of the distribution. The model is approximately commuting at large couplings and we find the joint eigenvalue distribution of the two matrices. We also study a related three matrix model finding the corresponding three dimensional eigenvalue distribution there also. The techniques developed here are more widely applicable to other multi-matrix models.",1304.7723v1 2013-11-25,Inverted-wedge silica resonators for controlled and stable coupling,"Silica microresonators with an inverted-wedge shape were fabricated using conventional semiconductor fabrication methods. The measured quality factors of the resonators were greater than $10^6$ in 1550 nm band. Controllable coupling from under coupling, through critical coupling, to over coupling was demonstrated by horizontally moving a fiber taper while in touch with the top surface of the resonator. Thin outer ring of the resonator provided a support for the fiber taper leading to a robust stable coupling.",1311.6382v1 2014-02-27,Jarzynski equality and the second law of thermodynamics beyond the weak-coupling limit: The quantum Brownian oscillator,"We consider a time-dependent quantum linear oscillator coupled to a bath at an arbitrary strength. We then introduce a generalized Jarzynski equality (GJE) which includes the terms reflecting the system-bath coupling. This enables us to study systematically the coupling effect on the linear oscillator in a non-equilibrium process. This is also associated with the second law of thermodynamics beyond the weak-coupling limit. We next take into consideration the GJE in the classical limit. By this generalization we show that the Jarzynski equality in its original form can be associated with the second law, in both quantal and classical domains, only in the vanishingly small coupling regime.",1402.7056v1 2014-04-22,Signal amplification by unidirectional coupling of oscillators,"We report our investigation on the input signal amplification in unidirectionally coupled monostable Duffing oscillators in one- and two-dimensions with first oscillator alone driven by a weak periodic signal. Applying a perturbation theory we obtain a set of nonlinear equations for the response amplitude of the coupled oscillators. We identify the conditions for undamped signal propagation with enhanced amplitude through the coupled oscillators. When the number of oscillators increases the response amplitude approaches a limiting value. We determine this limiting value. Also, we analyse the signal amplification in the coupled oscillators in two-dimensions with fraction of oscillators chosen randomly for coupling and forcing.",1404.5397v1 2014-07-01,Near-field tuning of optomechanical coupling in a split-beam nanocavity,"Tunable evanescent coupling is used to modify the optomechanical interactions within a split-beam photonic crystal nanocavity. An optical fiber taper probe is used to renormalize the optical nanocavity field and introduce a dissipative optomechanical coupling channel, reconfiguring and enhancing coupling between the optical and mechanical resonances of the device. Positioning of the fiber taper allows preferential coupling to specific mechanical modes and provides a mechanism for tuning the optomechanical interaction between dissipative and dispersive coupling regimes.",1407.0106v1 2014-07-16,Ultralow mode-volume photonic crystal nanobeam cavities for high efficiency coupling to individual carbon nanotube emitters,"We report on high efficency coupling of individual air-suspended carbon nanotubes to silicon photonic crystal nanobeam cavities. Photoluminescence images of dielectric- and air-mode cavities reflect their distinctly different mode profiles and show that fields in the air are important for coupling. We find that the air-mode cavities couple more efficiently, and estimated spontaneous emission coupling factors reach a value as high as 0.85. Our results demonstrate advantages of ultralow mode-volumes in air-mode cavities for coupling to low-dimensional nanoscale emitters.",1407.4200v1 2014-09-23,Exact Coupling Threshold for Structural Transition in Interconnected Networks,"Interconnected networks are mathematical representation of systems where two or more simple networks are coupled to each other. Depending on the coupling weight between the two components, the interconnected network can function in two regimes: one where the two networks are structurally distinguishable, and one where they are not. The coupling threshold--denoting this structural transition--is one of the most crucial concepts in interconnected networks. Yet, current information about the coupling threshold is limited. This letter presents an analytical expression for the exact value of the coupling threshold and outlines network interrelation implications.",1409.6560v1 2014-12-17,Energy spectra of two interacting fermions with spin-orbit coupling in a harmonic trap,"We explore the two-body spectra of spin-$1/2$ fermions in isotropic harmonic traps with external spin-orbit potentials and short range two-body interactions. Using a truncated basis of total angular momentum eigenstates, non-perturbative results are presented for experimentally realistic forms of the spin-orbit coupling: a pure Rashba coupling, Rashba and Dresselhaus couplings in equal parts, and a Weyl-type coupling. The technique is easily adapted to bosonic systems and other forms of spin-orbit coupling.",1412.5634v2 2015-01-13,Path Coupling and Aggregate Path Coupling,"In this survey paper, we describe and characterize an extension to the classical path coupling method applied statistical mechanical models, referred to as aggregate path coupling. In conjunction with large deviations estimates, we use this aggregate path coupling method to prove rapid mixing of Glauber dynamics for a large class of statistical mechanical models, including models that exhibit discontinuous phase transitions which have traditionally been more difficult to analyze rigorously. The parameter region for rapid mixing for the generalized Curie-Weiss-Potts model is derived as a new application of the aggregate path coupling method.",1501.03107v1 2015-02-06,Wake Potential in Strong Coupling Plasma from AdS/CFT Correspondence,"With the dielectric function computed from AdS/CFT correspondence, we studied the wake potential induced by a fast moving charge in strong coupling plasma, and compared it with the weak coupling wake potential for different particle velocities as $v=0.55c$ and $v=0.99c$. The most prominent difference between strong and weak wake potential is that when $v=0.99c$ the remarkable oscillation due to Cerenkov-like radiation and Mach cone in weak coupling disappears in strong coupling, which implies that the plasmon mode with phase velocity lower than the speed of light dose not exist in strong coupling plasma.",1502.01841v1 2015-03-24,Reduced coupling with global pulses in quantum registers,"Decoupling is an important tool to prolong the coherence time of quantum systems. Most decoupling schemes have been assuming selective controls on the system and it is believed that with global pulses one can only decouple systems with certain coupling terms like secular dipole-dipole coupling. In this article we show that with global pulses it is possible to reduce the coupling strength of other types of coupling, which we demonstrate with Ising coupling. The complexity of such pulses is independent of the size of system.",1503.07058v1 2015-05-28,Intrinsic spin Hall effect in systems with striped spin-orbit coupling,"The Rashba spin-orbit coupling arising from structure inversion asymmetry couples spin and momentum degrees of freedom providing a suitable (and very intensively investigated) environment for spintronic effects and devices. Here we show that in the presence of strong disorder, non-homogeneity in the spin-orbit coupling gives rise to a finite spin Hall conductivity in contrast with the corresponding case of a homogeneous linear spin-orbit coupling. In particular, we examine the inhomogeneity arising from a striped structure for a two-dimensional electron gas, affecting both density and Rashba spin-orbit coupling. We suggest that this situation can be realized at oxide interfaces with periodic top gating.",1505.07667v1 2015-11-04,Generalised matter couplings in massive bigravity,"We investigate matter couplings in massive bigravity. We find a new family of such consistent couplings, including and extending known consistent matter couplings, and we investigate their decoupling limits, ADM decompositions, Higuchi bounds and further aspects. We show that differences to previous known consistent couplings only arise beyond the $\Lambda_3$ decoupling limit and discuss the uniqueness of consistent matter couplings and how this is related to the so-called symmetric vielbein condition. Since we work in a vielbein formulation, these results easily generalise to multi-gravity.",1511.01485v1 2015-11-10,Waveguide-loaded silica fibers for coupling to high-index micro-resonators,"Tapered silica fibers are often used to rapidly probe the optical properties of micro-resonators. However, their low refractive index precludes phase-matching when coupling to high-index micro-resonators, reducing efficiency. Here we demonstrate efficient optical coupling from tapered fibers to high-index micro-resonators by loading the fibers with an ancillary adiabatic waveguide-coupler fabricated via angled-etching. We demonstrate greatly enhanced coupling to a silicon multimode micro-resonator when compared to coupling via the bare fiber only. Signatures of resonator optical bistability are observed at high powers. This scheme can be applied to resonators of any size and material, increasing the functional scope of fiber coupling.",1511.03332v1 2016-04-05,Anomalous Top and Bottom Yukawa Couplings and LHC Run 1 Data,"In some extensions of the Standard Model, Yukawa couplings of the physical Higgs boson can be deviated from those in the Standard Model. We study a possibility whether or not such anomalous Yukawa couplings are consistent with the LHC Run 1 data. It is found that sizable deviations of top and bottom (and tau) Yukawa couplings from the Standard Model predictions can nicely fit the data. New physics beyond the Standard Model can be revealed through more precise measurements of such anomalous Yukawa couplings at the LHC Run 2 in the near future. We also discuss a simple setup which can leads to anomalous Yukawa couplings.",1604.01150v1 2017-02-17,Generalized two-temperature model for coupled phonons,"The design of graphene-based composite with high thermal conductivity requires a comprehensive understanding of phonon coupling in graphene. We extended the two-temperature model to coupled groups of phonon. The study give new physical quantities, the phonon-phonon coupling factor and length, to characterize the couplings quantitatively. Besides, our proposed coupling length has an obvious dependence on system size. Our studies can not only observe the nonequilibrium between different groups of phonon, but explain theoretically the thermal resistance inside graphene.",1702.05237v2 2018-11-19,Controllable coupled-resonator-induced transparency in a dual-recycled Michelson interferometer,"We theoretically and experimentally study the effect of the coupled-resonator-induced transparency in the Michelson interferometer with the dual-recycled configuration, which is equivalent to the adjustable coupled resonator. The coupling strength, corresponding to the splitting of the reflection spectrum and associated with the width of the coupled-resonator-induced transparent window,can be controlled by adjusting the arm lengths, i.e., the relative phase of the interference arms on the 50/50 beam splitter. Thus, this tunability of the coupling strength can be very fast, and the absorptive and dispersive properties can be effectively controlled. This work provides a new system to coherently control and storage optical field.",1811.07444v1 2018-11-26,Destabilization of the EW vacuum in non-minimally coupled inflation,"Current cosmological data favour inflationary models non-minimally coupled to gravity. In this work we study the implications of the metastability of the electroweak vacuum in this framework. We consider an inflaton field with a non-minimal coupling to Ricci curvature and a portal coupling between the Higgs field and the inflaton and find that the ratio of the two couplings is severely constrained from stability during inflation and reheating dynamics, with constraints becoming more severe for weaker non-minimal coupling as during inflation Higgs fluctuations are amplified by inflationary expansion and after inflation by parametric resonance due to an oscillating inflaton background.",1811.10569v1 2014-03-05,Black hole temperature: minimal coupling vs conformal coupling,"In this article, we discuss the propagation of scalar fields in conformally transformed spacetimes with either minimal or conformal coupling. The conformally coupled equation of motion is transformed into a one-dimensional Schr\""{o}dinger-like equation with an invariant potential under conformal transformation. In a second stage, we argue that calculations based on conformal coupling yield the same Hawking temperature as those based on minimal coupling. Finally, it is conjectured that the quasi normal modes of black holes are invariant under conformal transformation.",1403.1014v2 2017-01-13,Bose-Einstein condensates in the presence of Weyl spin-orbit coupling,"We consider two-component Bose-Einstein condensates subject to Weyl spin-orbit coupling. We obtain mean-field ground state phase diagram by variational method. In the regime where interspecies coupling is larger than intraspecies coupling, the system is found to be fully polarized and condensed at a finite momentum lying along the quantization axis. We characterize this phase by studying the excitation spectrum, the sound velocity, the quantum depletion of condensates, the shift of ground state energy, and the static structure factor. We find that spin-orbit coupling and interspecies coupling generally leads to competing effects.",1701.03673v1 2008-07-28,Non supersymmetric strong coupling background from the large N quantum mechanics of two matrices coupled via a Yang-Mills interaction,"We derive the planar large N non-supersymmetric background of the quantum mechanical hamiltonian of two hermitean matrices coupled via a Yang-Mills interaction, in terms of the density of eigenvalues of one of the matrices. This background satisfies an implicit non linear integral equation, with a perturbative small coupling expansion and a solvable large coupling solution, which is obtained. The energy of system and the expectation value of several correlators are obtained in this strong coupling limit. They are free of infrared divergences.",0807.4376v1 2011-11-22,Chaos synchronization in networks of delay-coupled lasers: Role of the coupling phases,"We derive rigorous conditions for the synchronization of all-optically coupled lasers. In particular, we elucidate the role of the optical coupling phases for synchronizability by systematically discussing all possible network motifs containing two lasers with delayed coupling and feedback. Hereby we explain previous experimental findings. Further, we study larger networks and elaborate optimal conditions for chaos synchronization. We show that the relative phases between lasers can be used to optimize the effective coupling matrix.",1111.5131v2 2016-08-05,Transition from Amplitude Death to Oscillation Death in Coupled Chua Circuits,"In this piece of work, an important transition from amplitude death (AD) to oscillation death (OD) state in coupled Chua circuit has been explored for the first time. Here, mean field diffusively (MFD) coupled Chua circuits are when additionally coupled through direct coupling, it exhibits the AD-OD transition phenomena. The effect of design parameters and coupling parameters are investigated in details. For both identical and non-identical systems the AD make transition to OD through symmetry breaking. These are investigated through numerical simulations and are established through hardware experiment. The present study includes a new dimension to versatility of Chua circuit in the field of nonlinear dynamics.",1608.01750v1 2017-10-23,Phases of a strongly coupled four-fermion theory,"We present ongoing investigations of a four-dimensional lattice field theory with four massless reduced staggered fermions coupled through an SU(4)-invariant four-fermion interaction. As in previous studies of four-fermion and Higgs--Yukawa models with different lattice fermion discretizations, we observe a strong-coupling phase in which the system develops a mass gap without breaking any lattice symmetry. This symmetric strong-coupling phase is separated from the symmetric weak-coupling phase by a narrow region of four-fermi coupling in which the system exhibits long-range correlations.",1710.08137v1 2018-09-26,Period-doubling route from synchronization to chaos of an oscillator coupled to a regular oscillator,"Spatiotemporal chaos in the form of defect-mediated turbulence is known for oscillators coupled by diffusion. Here we explore the same conditions that produce defect turbulence, in an array of oscillators that are coupled through the activator to a regular oscillator. We find that for very small coupling the oscillators behave independent of each other and then there is a transition to complete synchronization. On further increasing the coupling strength, there is period doubling and a transition to chaotic behavior of each driven unit. However the global behavior shows some ordering, and the period-two oscillations become period-one with a further increase in the coupling strength.",1809.10010v1 2020-12-25,Colossal stability of antiferromagnetically exchange coupled nanomagnets,"Bistable nanomagnets store a binary bit of information. Exchange coupled nanomagnets can increase the thermal stability at low dimensions. Here we show that the antiferromagnetically (AFM) coupled nanomagnets can be highly stable at low dimensions than that of the ferromagnetically (FM) coupled nanomagnets. By solving stochastic Landau-Lifshitz-Gilbert equation of magnetization dynamics at room temperature, we analyze the stability of the exchange coupled nanomagnets in the presence of correlated, uncorrelated, and anti-correlated noise. The results show that the correlated noise can make the stability of the AFM coupled nanomagnets very high. Such finding will lead to very high-density non-volatile storage and logic devices in our future information processing systems.",2012.13590v1 2020-12-29,A constructive method to minimize couple matchings,"This paper provides constructive procedures for the indeterminacy coupling between two marginal distributions, an alternative to independence coupling. It also introduces a drawing under indeterminacy into a mixture of three independent couplings. Leveraging on this decomposition it states that indeterminacy optimally reduces couple matchings, minimizing the expected number of equal couples drawn in a row. Besides it is seen that the Janson Vegelius coefficient is nothing but a deviation to indeterminacy and it is shown that it tends to 0 when the number of modalities increases.",2012.14674v2 2000-06-20,Note on the Chandrasekhar Model of the Optical Activity of Crystals,"In this paper we discuss more wide applicability of the Chandrasekhar model of coupled oscillators in the optical rotatory dispersion of the crystals. We solve the problem using the Chandrasekhar model of two coupled oscillators in the case when we include all couplings between adjacent oscillators on the helix that is given by the crystal structure. Further we discuss the results of coupled oscillators models in the case of the including of the couplings between even and odd oscillators on the helix. The optical rotatory dispersion results obtained after the approximations of the oscillator strengths verify that these couplings have the important influence on the crystal optical rotatory dispersion.",0006300v1 2017-05-14,Electroweak Baryogenesis driven by Extra Top Yukawa Couplings,"We study electroweak baryogenesis driven by the top quark in a general two Higgs doublet model with flavor-changing Yukawa couplings, keeping the Higgs potential $CP$ invariant. With Higgs sector couplings and the additional top Yukawa coupling $\rho_{tt}$ all of $\mathcal{O}$(1), one naturally has sizable $CP$ violation that fuels the cosmic baryon asymmetry. Even if $\rho_{tt}$ vanishes, the favor-changing coupling $\rho_{tc}$ can still lead to successful baryogenesis. Phenomenological consequences such as $t\to ch$, $\tau \to \mu\gamma$, electron electric dipole moment, $h\to\gamma\gamma$, and $hhh$ coupling are discussed.",1705.05034v2 2017-09-20,Superfluid transition temperature of spin-orbit and Rabi coupled fermions with tunable interactions,"We obtain the superfluid transition temperature of equal Rashba-Dresselhaus spin-orbit and Rabi coupled Fermi superfluids, from the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) regimes in three dimensions. Spin-orbit coupling enhances the critical temperature in the BEC limit, and can convert a first order phase transition in the presence of Rabi coupling into second order, as a function of the Rabi coupling for fixed interactions. We derive the Ginzburg-Landau equation to sixth power in the superfluid order parameter to describe both first and second order transitions as a function of spin-orbit and Rabi couplings.",1709.07042v1 2017-09-28,Negative index and mode coupling in all-dielectric metamaterials at terahertz frequencies,"We report on the role of the coupling of the modes of Mie resonances in all-dielectric metamaterials to ensure negative effective index at terahertz frequencies. We study this role according to the lattice period and according to the frequency overlapping of the modes of resonance. We show that negative effective refractive index requires sufficiently strong mode coupling and that for even more strong mode coupling, the first two modes of Mie resonances are degenerated; the effective refractive index is then undeterminded. We also show that adjusting the mode coupling leads to near-zero effective index, or even null effective index. Further, we compare the mode coupling effect with hybridization in metamaterials.",1709.09998v1 2018-07-16,Free field structure of the model with a spin-$\frac{3}{2}$ Rarita-Schwinger field directly coupled to a spin-$\frac{1}{2}$ field,"In earlier work we introduced an abelianized gauge field model in which a Rarita-Schwinger field is directly coupled to a spin-$\frac{1}{2}$ field, and showed that this model admits a perturbative expansion in the gauge field coupling. As a preliminary to further study of the coupled model, in this paper we present a detailed analysis of the free field structure that obtains when the dimensionless gauge coupling is set to zero, but the dimension one coupling of the spin-$\frac{3}{2}$ and spin-$\frac{1}{2}$ fields remains nonzero.",1807.06146v1 2018-12-26,Soliton lattices in the Gross-Pitaevskii equation with nonlocal and repulsive coupling,"Spatially-periodic patterns are studied in nonlocally coupled Gross-Pitaevskii equation. We show first that spatially periodic patterns appear in a model with the dipole-dipole interaction. Next, we study a model with a finite-range coupling, and show that a repulsively coupled system is closely related with an attractively coupled system and its soliton solution becomes a building block of the spatially-periodic structure. That is, the spatially-periodic structure can be interpreted as a soliton lattice. An approximate form of the soliton is given by a variational method. Furthermore, the effects of the rotating harmonic potential and spin-orbit coupling are numerically studied.",1812.10218v1 2019-01-25,Translation-Rotation Coupling in the Dynamics of Linear Molecules in Water,"We study by computer simulations the coupled rotational and translational dynamics of three important linear diatomic molecules, namely, carbon monoxide (CO), nitric oxide (NO) and cyanide ion (CN-) in water. Translational diffusion of these molecules is found to be strongly coupled to their own rotational dynamics which in turn are coupled to similar motions of surrounding water. We examined the validity of hydrodynamic predictions and found them to be largely insufficient, particularly for rotational diffusion. A mode coupling theory approach is developed and applied to understand the complexity of translation-rotation coupling.",1901.08852v1 2019-03-17,Sensing Kondo correlations in a suspended carbon nanotube mechanical resonator with spin-orbit coupling,"We study electron mechanical coupling in a suspended carbon nanotube (CNT) quantum dot device. Electron spin couples to the flexural vibration mode due to spin-orbit coupling in the electron tunneling processes. In the weak coupling limit, i.e. electron-vibration coupling is much smaller than the electron energy scale, the damping and resonant frequency shift of the CNT resonator can be obtained by calculating the dynamical spin susceptibility. We find that strong spin-flip scattering processes in Kondo regime significantly affect the mechanical motion of the carbon nanotube: Kondo effect induces strong damping and frequency shift of the CNT resonator.",1903.07049v1 2016-03-20,Different Types of Synchronization in Coupled Network Based Chaotic Circuits,"We propose a simple and new unified method to achieve lag, complete and anticipatory synchronizations in coupled nonlinear systems. It can be considered as an alternative to the subsystem and intentional parameter mismatch methods. This novel method is illustrated in a unidirectionally coupled RC phase shift network based Chua's circuit. Employing feedback coupling, different types of chaos synchronization are observed experimentally and numerically in coupled identical chaotic oscillators {\emph{without using time delay}}. With a simple switch in the experimental set up we observe different kinds of synchronization. We also analyze the coupled system with numerical simulations.",1603.06250v1 2016-10-11,Uniform Avoidance Coupling of Simple Random Walks,"We start by introducing avoidance coupling of Markov chains, with an overview of existing results. We then introduce and motivate a new notion, uniform avoidance coupling. We show that the only Markovian avoidance coupling on a cycle is of this type, and that uniform avoidance coupling of simple random walks is impossible on trees, and prove that it is possible on several classes of graphs. We also derive a condition on the vertex neighborhoods in a graph equivalent to that graph admitting a uniform avoidance coupling of simple random walks, and an algorithm that tests this with run time polynomial in the number of vertices.",1610.03418v1 2017-11-23,Explosive synchronization transition in a ring of coupled oscillators,"Explosive synchronization(ES), as one kind of abrupt dynamical transition in nonlinearly coupled systems, is currently a subject of great interests. Given a special frequency distribution, a mixed ES is observed in a ring of coupled phase oscillators which transit from partial synchronization to ES with the increment of coupling strength. The coupling weight is found to control the size of the hysteresis region where asynchronous and synchronized states coexist. Theoretical analysis reveals that the transition varies from the mixed ES, to the ES and then to a continuous one with increasing coupling weight. Our results are helpful to extend the understanding of the ES in homogenous networks.",1711.08567v1 2020-06-04,A Study on the Synchronization Aspect of Star Connected Identical Chua Circuits,"This paper provides a study on the synchronization aspect of star connected $N$ identical chua's circuits. Different coupling such as conjugate coupling, diffusive coupling and mean-field coupling have been investigated in star topology. Mathematical interpretation of different coupling aspects have been explained. Simulation results of different coupling mechanism have been studied.",2006.03155v1 2021-02-02,Couplings of the Random-Walk Metropolis algorithm,"Couplings play a central role in contemporary Markov chain Monte Carlo methods and in the analysis of their convergence to stationarity. In most cases, a coupling must induce relatively fast meeting between chains to ensure good performance. In this paper we fix attention on the random walk Metropolis algorithm and examine a range of coupling design choices. We introduce proposal and acceptance step couplings based on geometric, optimal transport, and maximality considerations. We consider the theoretical properties of these choices and examine their implication for the meeting time of the chains. We conclude by extracting a few general principles and hypotheses on the design of effective couplings.",2102.01790v1 2015-07-13,Ambipolar spin-spin coupling in p$^+$-GaAs,"A novel spin-spin coupling mechanism that occurs during the transport of spin-polarized minority electrons in semiconductors is described. Unlike the Coulomb spin drag, this coupling arises from the ambipolar electric field which is created by the differential movement of the photoelectrons and the photoholes. Like the Coulomb spin drag, it is a pure spin coupling that does not affect charge diffusion. Experimentally, the coupling is studied in $p^+$ GaAs using polarized microluminescence. The coupling manifests itself as an excitation power dependent reduction in the spin polarization at the excitation spot \textit{without} any change of the spatially averaged spin polarization.",1507.03347v1 2020-01-23,Bright solitons in a spin-tensor-momentum-coupled Bose-Einstein condensate,"Synthetic spin-tensor-momentum coupling has recently been proposed to realize in atomic Bose-Einstein condensates. Here we study bright solitons in Bose-Einstein condensates with spin-tensor-momentum coupling and spin-orbit coupling. The properties and dynamics of spin-tensor-momentum-coupled and spin-orbit-coupled bright solitons are identified to be different. We contribute the difference to the different symmetries.",2001.08794v1 2020-03-05,Deformation for coupled Kähler-Einstein metrics,"The notion of coupled K\""ahler-Einstein metrics was introduced recently by Hultgren-WittNystr\""om. In this paper we discuss deformation of a coupled K\""ahler-Einstein metrics on a Fano manifold. In particular we obtain a necessary and sufficient condition for a coupled K\""ahler-Einstein metric to be deformed to another coupled K\""ahler-Einstein metric for a Fano manifold admitting non-trivial holomorphic vector fields. In addition we also discuss deformation for a coupled K\""aher-Einstein metric on a Fano manifold when the complex structure varies.",2003.02410v3 2020-05-12,Circuit-model formulas for external-Q factor of resonant cavities with capacitive and inductive coupling,"The external-Q factor of a resonant mode of a cavity represents the strength of the electromagnetic coupling between this resonant mode and the transmission mode of a waveguide coupled to the cavity. In this paper, we derive formulas to explicitly give the external Q of the cavities coupled with the waveguide through capacitive and inductive coupling. The derivation is based on the classical method that uses the reflection coefficient to estimate the coupling strength. Although the external Q is evaluated via three-dimensional computer simulations currently, these formulas may be useful for making speculations in the initial stages of cavity design.",2005.05843v2 2020-05-26,Coupled McKean-Vlasov stochastic differential equations with jumps,"This work concerns a type of coupled McKean-Vlasov stochastic differential equations (MVSDEs in short) with jumps. First, we prove superposition principles for these coupled MVSDEs with jumps and non-local space-distribution dependent Fokker-Planck equations. Since superposition principles are related to the well-posedness of weak solutions for coupled MVSDEs with jumps, then we give some conditions to assure it. After this, we construct space-distribution valued Markov processes associated with these coupled MVSDEs with jumps. Finally, the ergodicity of these coupled MVSDEs with jumps are investigated. As a by-product, we show the exponential ergodicity for a type of MVSDEs with jumps.",2005.13036v2 2020-10-16,Maximal couplings of the Metropolis-Hastings algorithm,"Couplings play a central role in the analysis of Markov chain Monte Carlo algorithms and appear increasingly often in the algorithms themselves, e.g. in convergence diagnostics, parallelization, and variance reduction techniques. Existing couplings of the Metropolis-Hastings algorithm handle the proposal and acceptance steps separately and fall short of the upper bound on one-step meeting probabilities given by the coupling inequality. This paper introduces maximal couplings which achieve this bound while retaining the practical advantages of current methods. We consider the properties of these couplings and examine their behavior on a selection of numerical examples.",2010.08573v1 2020-10-16,Quasinormal Coupled Mode Theory,"Coupled mode theory (CMT) is a powerful framework for decomposing interactions between electromagnetic waves and scattering bodies into resonances and their couplings with power-carrying channels. It has widespread use in few-resonance, weakly coupled resonator systems across nanophotonics, but cannot be applied to the complex scatterers of emerging importance. We use quasinormal modes to develop an exact, ab initio generalized coupled mode theory from Maxwell's equations. This quasinormal coupled mode theory, which we denote ""QCMT"", enables a direct, mode-based construction of scattering matrices without resorting to external solvers or data. We consider canonical scattering bodies, for which we show that a CMT model will necessarily be highly inaccurate, whereas QCMT exhibits near-perfect accuracy.",2010.08650v2 2021-03-18,Noise-assisted routing in mode-coupling devices,"The dynamical control of energy transfer between interacting systems is fundamental in diverse applications related to physical, electronic and chemical processes. Recent developments show that noise may enhance or suppress power transfer in systems described by Coupled-Mode Theory. We show a semi-analytic approach to utilize dynamical noise to produce routing in coupled mode devices. We present results for an optical mode-coupling device with induced noise in the refractive index of the material. However, our approach is valid for networks of coupled oscillators of any type as long as their dynamics are described by Coupled-Mode Theory.",2103.10256v1 2021-05-10,Self-Bound Quantum Droplet with Internal Stripe Structure in 1D Spin-Orbit-Coupled Bose Gas,"We study the quantum-droplet state in a 3-dimensional (3D) Bose gas in the presence of 1D spin-orbit-coupling and Raman coupling, especially the stripe phase with density modulation, by numerically computing the ground state energy including the mean-field energy and Lee-HuangYang correction. In this droplet state, the stripe can exist in a wider range of Raman coupling, compared with the BEC-gas state. More intriguingly, both spin-orbit-coupling and Raman coupling strengths can be used to tune the droplet density.",2105.04172v1 2021-10-15,"Loosely coupled, non-iterative time-splitting scheme based on Robin-Robin coupling: unified analysis for parabolic/parabolic and parabolic/hyperbolic problems","We present a loosely coupled, non-iterative time-splitting scheme based on Robin-Robin coupling conditions. We apply a novel unified analysis for this scheme applied to both a Parabolic/Parabolic coupled system and a Parabolic/Hyperbolic coupled system. We show for both systems that the scheme is stable, and the error converges as $\mathcal{O}\big(\Delta t \sqrt{T +\log{\frac{1}{\Delta t}}}\big)$, where $\Delta t$ is the time step",2110.08181v1 2022-01-24,Combination of dissipative and dispersive coupling in the cavity optomechanical systems,"An analysis is given for the Fabry-Perot cavity having a combination of dissipative and dispersive optomechanical coupling. It is established that the combined coupling leads to optical rigidity. At the same time, this rigidity appears in systems with the combined coupling on the resonant pump, which is not typical for pure dispersive and dissipative couplings. A proposal is made to use this system to detect small signal forces with better sensitivity than SQL. It is also demonstrated that this optomechanical system can create ponderomotive squeezing with controllable parameters over a wider range than ponderomotive squeezing using dispersive coupling.",2201.09920v1 2022-02-09,Rational design of piezoelectric metamaterials with tailored electro-momentum coupling,"Piezoelectric materials have wide sensing and energy transduction applications due to their inherent coupling of mechanical deformation and electric field. Recent discoveries have revealed that asymmetric or heterogeneous microstructures of piezoelectric composites can create an additional coupling of macroscopic momentum to an electric field termed electro-momentum coupling, introducing a new degree of design freedom. In this work, by employing the homogenization scheme, the physical origin of electro-momentum coupling is explored by a high throughput sweep over the microstructure design space of a piezoelectric composite system. This study shows how material constituent properties and geometrical arrangements can affect electro-momentum coupling and be smartly tailored for applications of interest.",2202.04275v1 2022-10-12,Orthogonal Approximate Message-Passing for Spatially Coupled Linear Models,"Orthogonal approximate message-passing (OAMP) is proposed for signal recovery from right-orthogonally invariant linear measurements with spatial coupling. Conventional state evolution is generalized to a unified framework of state evolution for the spatial coupling and long-memory case. The unified framework is used to formulate the so-called Onsager correction in OAMP for spatially coupled systems. The state evolution recursion of Bayes-optimal OAMP is proved to converge for spatially coupled systems via Bayes-optimal long-memory OAMP and its state evolution. This paper proves the information-theoretic optimality of Bayes-optimal OAMP for noiseless spatially coupled systems with right-orthogonally invariant sensing matrices.",2210.06019v2 2022-10-13,Long-Memory Message-Passing for Spatially Coupled Systems,"This paper addresses the reconstruction of sparse signals from spatially coupled, linear, and noisy measurements. A unified framework of rigorous state evolution is established for developing long-memory message-passing (LM-MP) in spatially coupled systems. LM-MP utilizes all previous messages to compute the current message while conventional MP only uses the latest messages. The unified framework is utilized to propose orthogonal approximate message-passing (OAMP) for spatially coupled systems. The framework for LM-MP is used as a technical tool to prove the convergence of state evolution for OAMP. Numerical results show that OAMP for spatially coupled systems is superior to that for systems without spatial coupling in the so-called waterfall region.",2210.06755v1 2023-01-30,Non-adiabatic derivative coupling elements for the coupled cluster singles and doubles model,"We present an efficient implementation of analytical non-adiabatic derivative coupling elements for the coupled cluster singles and doubles model. The derivative coupling elements are evaluated in a biorthonormal formulation in which the nuclear derivative acts on the right electronic state, where this state is biorthonormal with respect to the set of left states. This stands in contrast to earlier implementations based on normalized states and a gradient formula for the derivative coupling. As an illustration of the implementation, we determine a minimum energy conical intersection between the n{\pi}* and {\pi}{\pi}* states in the nucleobase thymine.",2301.13264v1 2023-05-17,"Couplings of Brownian motions on $SU(2,\mathbb{C})$ and $SL(2,\mathbb{R})$","The Lie groups $SU(2)$ and $SL(2,\mathbb{R})$ can be viewed as model spaces in subRiemannian geometry. Coupling two subelliptic Brownian motions on $SU(2)$ (resp. $SL(2,\mathbb{R})$) consists in coupling two Brownian motions on the sphere (resp. the hyperbolic plane) and simultaneously their swept areas. Using this approach we propose an explicit construction of a co-adapted successful coupling on $SU(2)$. The strategy is to alternate between reflection and synchronous (with noise) coupling on the sphere. We also describe some more general constructions of co-adapted couplings on $SU(2)$ and also on $SL(2,\mathbb{R})$.",2305.10017v3 2023-09-07,Evaluating Microservice Organizational Coupling based on Cross-service Contribution,"For traditional modular software systems, ""high cohesion, low coupling"" is a recommended setting while it remains so for microservice architectures. However, coupling phenomena commonly exist therein which are caused by cross-service calls and dependencies. In addition, it is noticeable that teams for microservice projects can also suffer from high coupling issues in terms of their cross-service contribution, which can inevitably result in technical debt and high managerial costs. Such organizational coupling needs to be detected and mitigated in time to prevent future losses. Therefore, this paper proposes an automatable approach to evaluate the organizational couple by investigating the microservice ownership and cross-service contribution.",2309.03552v1 2023-10-25,Significance of Elastic Coupling for Stresses and Leakage in Frictional Contacts,"We study how the commonly neglected coupling of normal and in-plane elastic response affects tribological properties when Hertzian or randomly rough indenters slide past an elastic body. Compressibility-induced coupling is found to substantially increase maximum tensile stresses, which cause materials to fail, and to decrease friction such that Amontons law is violated macroscopically even when it holds microscopically. Confinement-induced coupling increases friction and enlarges domains of high tension. Moreover, both types of coupling affect the gap topography and thereby leakage. Thus, coupling can be much more than a minor perturbation of a mechanical contact.",2310.16692v1 2023-12-06,"""Quantum bipolaron'' superconductivity from quadratic electron-phonon coupling","When the electron-phonon coupling is quadratic in the phonon coordinates, electrons can pair to form bipolarons due to phonon zero-point fluctuations, a purely quantum effect. We study superconductivity originating from this pairing mechanism in a minimal model and reveal that, in the strong coupling regime, the critical temperature ($T_c$) is only mildly suppressed by the coupling strength, in stark contrast to the exponential suppression in linearly coupled systems, thus implying higher optimal $T_c$ values. We demonstrate that large coupling constants of this flavor are achieved in known materials such as perovskites, and discuss strategies to realize such superconductivity using superlattices.",2312.03844v3 2024-02-16,Mean field coupled dynamical systems: Bifurcations and phase transitions,"We develop a bifurcation theory for infinite dimensional systems satisfying abstract hypotheses that are tailored for applications to mean field coupled chaotic maps. Our abstract theory can be applied to many cases, from globally coupled expanding maps to globally coupled Axiom A attractors. To illustrate the range of applicability, we analyze an explicit example consisting of globally coupled Anosov diffeomorphisms. For such an example, we classify all the invariant measures as the coupling strength varies; we show which invariant measures are physical, and we prove that the existence of multiple invariant physical measures is a purely infinite dimensional phenomenon, i.e., the model exhibits phase transitions in the sense of statistical mechanics.",2402.11076v1 2024-02-19,On Coupling Constraints in Linear Bilevel Optimization,"It is well-known that coupling constraints in linear bilevel optimization can lead to disconnected feasible sets, which is not possible without coupling constraints. However, there is no difference between linear bilevel problems with and without coupling constraints w.r.t. their complexity-theoretical hardness. In this note, we prove that, although there is a clear difference between these two classes of problems in terms of their feasible sets, the classes are equivalent on the level of optimal solutions. To this end, given a general linear bilevel problem with coupling constraints, we derive a respective problem without coupling constraints and prove that it has the same optimal solutions (when projected back to the original variable space).",2402.12191v1 1995-11-23,Generalized phase transitions in finite coupled map lattices,"We investigate generalized phase transitions of type localization - delocalization from one to several Sinai-Bowen-Ruelle invariant measures in finite networks of chaotic elements (coupled map lattices) with general graphs of connections in the limit of weak coupling.",9511005v1 1999-11-24,Renormalization Group Evolution and Infra-red Fixed Points in Minimal Supersymmetric Standard Model with Baryon and Lepton Number Violation,"We study the renormalization group evolution and infra-red stable fixed points of the Yukawa couplings and the soft supersymmetry breaking trilinear couplings of the minimal supersymmetric standard model with baryon and lepton number (and R-parity) violation involving the heaviest generations. We show analytically that in the Yukawa sector there is only one infra-red stable fixed point. This corresponds to non-trivial fixed point for the top-, bottom-quark Yukawa couplings and the $B$ violating coupling $\lambda_{233}''$, and a trivial one for the $\tau$-Yukawa coupling. All other possible fixed points are either unphysical or unstable in the infra-red region. We then carry out an analysis of the renormalization group equations for the soft supersymmetry breaking trilinear couplings, and determine the corresponding fixed points for these couplings. We also study the quasi-fixed point behaviour, both algebraically and with numerical solutions of the evolution equations, of the third generation Yukawa couplings and the baryon number violating coupling, and those of the soft supersymmetry breaking trilinear couplings. From the analysis of the fixed point behaviour, we obtain upper and lower bounds on the baryon number violating coupling $\lambda_{233}''$, as well as on the supersymmetry breaking trilinear couplings.",9911464v2 2000-05-31,Can Nucleon Tell Where the Couplings Run?,"The comparison of magnetic moments of neutron and proton reveals three possible states of a nucleon with the same correction of 0.033 for the central quarks. This may be interpreted as the contribution of a universal coupling as the common value where all the running couplings unite.",0005329v1 2001-03-01,Nonminimal Supersymmetric Standard Model with Baryon and Lepton Number Violation,"We carry out a comprehensive analysis of the nonminimal supersymmetric standard model (NMSSM) with baryon and lepton number violation. We catalogue the baryon and lepton number violating dimension four and five operators of the model. We then study the renormalization group evolution and infrared stable fixed points of the Yukawa couplings and the soft supersymmetry breaking trilinear couplings of this model with baryon and lepton number (and R-parity) violation involving the heaviest generations. We show analytically that in the Yukawa sector of the NMSSM there is only one infrared stable fixed point. This corresponds to a non-trivial fixed point for the top-, bottom-quark Yukawa couplings and the $B$ violating coupling $\lambda_{233}''$, and a trivial one for all other couplings. All other possible fixed points are either unphysical or unstable in the infrared region. We also carry out an analysis of the renormalization group equations for the soft supersymmetry breaking trilinear couplings, and determine the corresponding fixed points for these couplings. We then study the quasi-fixed point behaviour, both of the third generation Yukawa couplings and the baryon number violating coupling, and those of the soft supersymmetry breaking trilinear couplings. From the analysis of the fixed point behaviour, we obtain upper and lower bounds on the baryon number violating coupling $\lambda_{233}''$, as well as on the soft supersymmetry breaking trilinear couplings. Our analysis shows that the infrared fixed point behavior of NMSSM with baryon and lepton number violation is similar to that of MSSM.",0103005v1 1997-05-27,The topology of multi-coupling deformations of CFT,"We discuss the topological properties of the manifold of coupling constants for multi-coupling deformations of conformal field theories. We calculate the Euler and Betti numbers and briefly discuss physical applications of these results.",9705201v1 1999-04-06,A Comment on the Entropy of Strongly Coupled N=4,"We propose a field theory argument, which rests on the non-renormalization of the two point function of the energy-momentum tensor, why the ratio between the entropies of strongly coupled and weakly coupled N=4 is of order one.",9904035v1 1991-09-21,"The K_t-functional for the interpolation couple L_1(A_0),L_infinity(A_1)","Let (A_0,A_1) be a compatible couple of Banach spaces in the interpolation theory sense. We give a formula for the K_t-functional of the interpolation couples (l_1(A_0),c_0(A_1)) or (l_1(A_0),l_infinity(A_1)) and (L_1(A_0),L_infinity(A_1)).",9201232v1 2004-10-20,Coupling for some partial differential equations driven by white noise,"We prove, using coupling arguments, exponential convergence to equilibrium for reaction--diffusion and Burgers equations driven by space-time white noise. We use a coupling by reflection.",0410441v1 1999-11-02,A Phase Transistion in the Water Coupled to a Local External Perturbation,"A flux of ideal fluid coupled to perturbation is investigated by nonperturbative methods of the quantum field theory. Asymptotic behavior of the flux coupled to perturbation turns out to be similiar to that of superfluids.",9911002v1 2010-07-29,Dilaton coupling revisited,"We reinvestigate the dilaton coupling in the string theory, which comes from a wrapped membrane. The ghost number anomaly associated with the string worldsheet diffeomorphism is shown to induce the dilaton coupling.",1007.5156v2 2012-09-03,The dynamics of a qubit coupled strongly with a quantum oscillator,"The dynamics of a qubit coupled with a quantum oscillator is re-studied in the region of strong coupling. The non-degenerate perturbation is added to the usual degenerate one and new results are given.",1209.0321v1 2014-10-28,Existence of Bound and Ground States for a System of Coupled Nonlinear Schrödinger-KdV Equations,"We prove the existence of bound and ground states for a system of coupled nonlinear Schr\""odinger-Korteweg-de Vries equations, depending on the size of the coupling coefficient.",1410.7638v2 2015-04-28,Fully Coupled Forward-backward Stochastic Differential Equations on Markov Chains,"We define fully coupled forward-backward stochastic differential equations on spaces related to continuous time, finite state Markov Chains. Existence and uniqueness results of the fully coupled forward-backward stochastic differential equations on Markov Chains are obtained.",1504.07368v1 2018-09-04,Chiral magnetic interlayer coupling in synthetic antiferromagnets,"The exchange coupling underlies ferroic magnetic coupling and is thus the key element that governs statics and dynamics of magnetic systems. This fundamental interaction comes in two flavors - symmetric and antisymmetric coupling. While symmetric coupling leads to ferro- and antiferromagnetism, antisymmetric coupling has attracted significant interest owing to its major role in promoting topologically non-trivial spin textures that promise high-speed and energy-efficient devices. So far, the antisymmetric exchange coupling rather short-ranged and limited to a single magnetic layer has been demonstrated, while the symmetric coupling also leads to long-range interlayer exchange coupling. Here, we report the missing component of the long-range antisymmetric interlayer exchange coupling in perpendicularly magnetized synthetic antiferromagnets with parallel and antiparallel magnetization alignments. Asymmetric hysteresis loops under an in-plane field unambiguously reveal a unidirectional and chiral nature of this novel interaction, which cannot be accounted for by existing coupling mechanisms, resulting in canted magnetization alignments. This can be explained by spin-orbit coupling combined with reduced symmetry in multilayers. This new class of chiral interaction provides an additional degree of freedom for engineering magnetic structures and promises to enable a new class of three-dimensional topological structures.",1809.01080v2 2018-09-10,Probing top-quark couplings indirectly at Higgs factories,"We perform a global effective-field-theory analysis to assess the combined precision on Higgs couplings, triple gauge-boson couplings, and top-quark couplings, at future circular $e^+e^-$ colliders, with a focus on runs below the $t\bar t$ production threshold. Deviations in the top-quark sector entering as one-loop corrections are consistently taken into account in Higgs and diboson processes. We find that future lepton colliders running at center-of-mass energies below the $t\bar t$ production threshold can still provide useful information on top-quark couplings, by measuring virtual top-quark effects. With rate and differential measurements, the indirect individual sensitivity achievable is better than at the high-luminosity LHC. However, strong correlations between the extracted top-quark and Higgs couplings are also present and lead to much weaker global constraints on top-quark couplings. This implies that a direct probe of top-quark couplings above the $t\bar t$ production threshold is helpful also for the determination of Higgs and triple-gauge-boson couplings. In addition, we find that below the $e^+e^-\to t\bar th$ production threshold, the top-quark Yukawa coupling can be determined by its loop corrections to all Higgs production and decay channels. Degeneracy with the $ggh$ coupling can be resolved, and even a global limit is competitive with the prospects of a linear collider above the threshold. This provides an additional means of determining the top-quark Yukawa coupling indirectly at lepton colliders.",1809.03520v2 2020-12-01,Angle-Independent Plasmonic Substrates for Multi-Mode Vibrational Strong Coupling with Molecular Thin Films,"Vibrational strong coupling of molecules to optical cavities based on plasmonic resonances has been explored recently, because plasmonic near-fields can provide strong coupling in sub-diffraction limited volumes. Such field localization maximizes coupling strength, which is crucial for modifying the vibrational response of molecules and, thereby, manipulating chemical reactions. Here, we demonstrate an angle-independent plasmonic nanodisk substrate that overcomes limitations of traditional Fabry-Perot optical cavities, because the design can strongly couple with all molecules on the surface of the substrate regardless of molecular orientation. We demonstrate that the plasmonic substrate provides strong coupling with the C=O vibrational stretch of deposited films of PMMA. We also show that the large linewidths of the plasmon resonance allows for simultaneous strong coupling to two, orthogonal water symmetric and asymmetric vibrational modes in a thin film of copper sulfate monohydrate deposited on the substrate surface. A three-coupled-oscillator model is developed to analyze the coupling strength of the plasmon resonance with these two water modes. With precise control over the nanodisk diameter, the plasmon resonance is tuned systematically through the modes, with the coupling strength to both modes varying as a function of the plasmon frequency, and with strong coupling to both modes achieved simultaneously for a range of diameters. This work may aid further studies into manipulation of the ground-state chemical landscape of molecules by perturbing multiple vibrational modes simultaneously and increasing the coupling strength in sub-diffraction limited volumes.",2012.00710v2 2019-05-16,Measuring Higgs self couplings in the presence of VVH and VVHH at the ILC,"The recent discovery of a Higgs boson at the LHC, while establishing the Higgs mechanism as the way of electroweak symmetry breaking, started an era of precision measurements involving the Higgs boson. In an effective Lagrangian framework, we consider the $e^+e^-\rightarrow ZHH$ process at the ILC running at a centre of mass energy of 500 GeV to investigate the effect of the $ZZH$ and $ZZHH$ couplings on the sensitivity of $HHH$ coupling in this process. Our results show that the sensitivity of the trilinear Higgs self couplings on this process has somewhat strong dependence on the Higgs-gauge boson couplings. Single and two parameter reach of the ILC with an integrated luminosity of 1000 fb$^{-1}$ are obtained on all the effective couplings indicating how these limits are affected by the presence of anomalous $ZZH$ and $ZZHH$ couplings. The kinematic distributions studied to understand the effect of the anomalous couplings, again, show a strong influence of $Z$-$H$ couplings on the dependence of these distributions on $HHH$ coupling. Similar results are indicated in the case of the process, $e^+e^-\rightarrow \nu\bar \nu HH$, considered at a centre of mass energy of 2 TeV, where the cross section is large enough. The effect of $WWH$ and $WWHH$ couplings on the sensitivity of $HHH$ coupling is clearly established through our analyses in this process.",1905.06601v1 2020-04-13,Discrete solitons in zigzag waveguide arrays with different types of linear mixing between nearest-neighbor and next-nearest-neighbor couplings,"We study discrete solitons in zigzag discrete waveguide arrays with different types of linear mixing between nearest-neighbor and next-nearest-neighbor couplings. The waveguide array is constructed from two layers of one-dimensional (1D) waveguide arrays arranged in zigzag form. If we alternately label the number of waveguides between the two layers, the cross-layer couplings (which couple one waveguide in one layer with two adjacent waveguides in the other layer) construct the nearestneighbor couplings, while the couplings that couple this waveguide with the two nearest-neighbor waveguides in the same layer, i.e., self-layer couplings, contribute the next-nearest-neighbor couplings. Two families of discrete solitons are found when these couplings feature different types of linear mixing. As the total power is increased, a phase transition of the second kind occurs for discrete solitons in one type of setting, which is formed when the nearest-neighbor coupling and next-nearest-neighbor coupling feature positive and negative linear mixing, respectively. The mobilities and collisions of these two families of solitons are discussed systematically throughout the paper, revealing that the width of the soliton plays an important role in its",2004.06006v1 2020-05-07,Coherent dynamics in frustrated coupled parametric oscillators,"We explore the coherent dynamics in a small network of three coupled parametric oscillators and demonstrate the effect of frustration on the persistent beating between them. Since a single-mode parametric oscillator represents an analog of a classical Ising spin, networks of coupled parametric oscillators are considered as simulators of Ising spin models, aiming to efficiently calculate the ground state of an Ising network - a computationally hard problem. However, the coherent dynamics of coupled parametric oscillators can be considerably richer than that of Ising spins, depending on the nature of the coupling between them (energy preserving or dissipative), as was recently shown for two coupled parametric oscillators. In particular, when the energy-preserving coupling is dominant, the system displays everlasting coherent beats, transcending the Ising description. Here, we extend these findings to three coupled parametric oscillators, focusing in particular on the effect of frustration of the dissipative coupling. We theoretically analyze the dynamics using coupled nonlinear Mathieu's equations, and corroborate our theoretical findings by a numerical simulation that closely mimics the dynamics of the system in an actual experiment. Our main finding is that frustration drastically modifies the dynamics. While in the absence of frustration the system is analogous to the two-oscillator case, frustration reverses the role of the coupling completely, and beats are found for small energy-preserving couplings.",2005.03562v2 2021-05-08,Are Low-energy Data already Hinting at Five Dimensions?,"Low-energy data, combined with renormalization group (RG) equations, can predict new physics at far higher energy scales. In this paper, we consider the possibility that the measured Higgs boson mass and top quark mass hint at a five-dimensional gauge-Higgs unification (5D GHU) model at a scale above TeV. We note that the vanishing of the Higgs quartic coupling and the proximity of the top quark Yukawa coupling and weak gauge coupling at high scales, inferred from the experimental data, are in harmony with 5D GHU, because in 5D GHU models the Higgs quartic coupling is forbidden by the 5D gauge symmetry and the Yukawa couplings and the weak gauge coupling originate from a common 5D gauge coupling. Based on the above insight, we propose a 5D GHU model where the Standard Model fermions are embedded in 5D fermions in a way to tightly relate the top Yukawa coupling with the weak gauge coupling. Also, the model predicts the presence of vector-like fermions (other than the Kaluza-Klein modes), which can affect the RG evolutions of the 4D theory and reconcile the scale of vanishing Higgs quartic coupling and that of equality of the top Yukawa and weak gauge couplings, thereby achieving a successful matching of the 4D theory with 5D GHU. We predict the vector-like fermion mass and the compactification scale of 5D GHU from the conditions for the successful matching.",2105.03661v2 2021-09-14,Emergent Dynamics and Spatio Temporal Patterns on Multiplex Neuronal Networks,"We present a study on the emergence of a variety of spatio temporal patterns among neurons that are connected in a multiplex framework, with neurons on two layers with different functional couplings. With the Hindmarsh-Rose model for the dynamics of single neurons, we analyze the possible patterns of dynamics in each layer separately and report emergent patterns of activity like in-phase synchronized oscillations and amplitude death for excitatory coupling and anti-phase mixed-mode oscillations in multi-clusters with phase regularities when the connections are inhibitory. When they are multiplexed, with neurons of one layer coupled with excitatory synaptic coupling and neurons of the other layer coupled with inhibitory synaptic coupling, we observe transfer or selection of interesting patterns of collective behavior between the layers. While the revival of oscillations occurs in the layer with excitatory coupling, the transition from anti-phase to in-phase and vice versa is observed in the other layer with inhibitory synaptic coupling. We also discuss how theselection of these spatio temporal patterns can be controlled by tuning the intralayer or interlayer coupling strengths or increasing the range of non-local coupling. With one layer having electrical coupling while the other synaptic coupling of excitatory(inhibitory)type, we find in-phase(antiphase) synchronized patterns of activity among neurons in both layers.",2109.06615v2 2022-07-13,Non-geometric tilt-to-length coupling in precision interferometry: mechanisms and analytical descriptions,"This paper is the second in a set of two investigating tilt-to-length (TTL) coupling. TTL describes the cross-coupling of angular or translational jitter into an interferometric phase signal and is an important noise source in precision interferometers, including space gravitational wave detectors like LISA. We discussed in 10.1088/2040-8986/ac675e the TTL coupling effects originating from optical path length changes, i.e. geometric TTL coupling. Within this work, we focus on the wavefront and detector geometry dependent TTL coupling, called non-geometric TTL coupling, in the case of two interfering fundamental Gaussian beams. We characterise the coupling originating from the properties of the interfering beams, i.e. their absolute and relative angle at the detector, their relative offset and the individual beam parameters. Furthermore, we discuss the dependency of the TTL coupling on the geometry of the detecting photodiode. Wherever possible, we provide analytical expressions for the expected TTL coupling effects. We investigate the non-geometric coupling effects originating from beam walk due to the angular or translational jitter of a mirror or a receiving system. These effects are directly compared with the corresponding detected optical path length changes in 10.1088/2040-8986/ac675e. Both together provide the total interferometric readout. We discuss in which cases the geometric and non-geometric TTL effects cancel one-another. Additionally, we list linear TTL contributions that can be used to counteract other TTL effects. Altogether, our results provide key knowledge to minimise the total TTL coupling noise in experiments by design or realignment.",2207.06278v3 2022-11-18,High energy solutions of quadratic coupling Schrodinger equation with nonconstant potential,"In this paper, we use the variational method, especially the perturbation method, to find the perturbed high energy solutions of the quadratic coupled Schrodinger system with asymmetric asymptotic potential and their asymptotic behavior as the coupling coefficient converges to 0.",2211.10115v1 2023-09-16,Entangling two giant atoms via a topological waveguide,"We study the entanglement generation of two two-level giant atoms coupled to a photonic waveguide, which is formed by a Su-Schrieffer-Heeger (SSH) type coupled-cavity array. Here, each atom is coupled to the waveguide through two coupling points. We focus on the two-atom separate-coupling case, and consider sixteen coupling configurations for the coupling-point distributions between the two atoms and the waveguide. We derive quantum master equations to govern the evolution of the two atoms and characterize atomic entanglement by calculating the concurrence of the two-atom states. It is found that the two giant-atom entanglement depends on the coupling configurations and the coupling-point distance of the giant atoms. In particular, the entanglement dynamics of the two giant atoms in fourteen coupling configurations depends on the dimerization parameter of the SSH waveguide. According to the self-energies of the two giant atoms, we find that ten of these sixteen coupling configurations can be divided into five pairs. We also show that delayed sudden birth of entanglement between the two giant atoms is largely enhanced in these five pairs of coupling configurations. This work will promote the study of quantum effects and coherent manipulation in giant-atom topological-waveguide-QED systems.",2309.08856v1 2024-02-21,Non-Markovian maximal couplings and a vertical reflection principle on a class of sub-Riemannian manifolds,"We develop non-Markovian, non-co-adapted couplings for sub-Riemannian Brownian motions in various sub-Riemannian manifolds, namely the three-dimensional Heisenberg group, higher-dimensional non-isotropic Heisenberg groups, SL(2,R) and its universal cover, and SU(2,C). Our primary focus is on the situation when the processes start from two points on the same vertical fiber, since in general co-adapted couplings cannot give the sharp rate for the coupling time in this case. Then for general points, we use this vertical coupling as the second stage of a two-stage coupling. Non-Markovian couplings in this context were first introduced by Banerjee-Gordina-Mariano, for the three-dimensional Heisenberg group, and were more recently extended by B\'en\'efice to SL(2,R) and SU(2,C), using a detailed consideration of the Brownian bridge. In contrast, our couplings are based on global isometries of the space, giving couplings that are maximal, as well as making the construction relatively simple and uniform across different manifolds. Moreover, this construction gives a coupling time that equals a hitting time for the vertical component of one of the Brownian motions, and this vertical component satisfies a reflection principle, which is useful in explicitly bounding the tail probability of the coupling time. We estimate the coupling time in these various situations and give applications to inequalities for the heat semigroup.",2402.13976v1 1998-08-02,Intermittency in coupled maps,"Using a renormalization method, we study the critical behavior for intermittency in two coupled one-dimensional (1D) maps. We find two fixed maps of the renormalization transformation. They all have common relevant eigenvalues associated with scaling of the control parameter of the uncoupled 1D map. However, the relevant ``coupling eigenvalues'' associated with coupling perturbations vary depending on the fixed maps. It is also found that the two fixed maps are associated with the critical behavior in the vicinity of a critical line segment. One fixed map with no relevant coupling eigenvalues governs the critical behavior at interior points of the critical line segment, while the other one with relevant coupling eigenvalues governs the critical behavior at both ends. The results of the two coupled 1D maps are also extended to many globally-coupled 1D maps, in which each 1D map is coupled to all the other ones with equal strength.",9808002v1 1998-11-10,Coupling between electron-spin and ferromagnetic clusters,"We analyze the adiabatic magnetization of ferromagnetic clusters in an intermediate coupling regime, where the anisotropic potential is comparable to other energy scales. We find a non-monotonic behavior of the magnetic susceptibility as a function of coupling with a peak. Coriolis coupling effects are calculated for the first time; they reduce the susceptibility somewhat.",9811126v1 2004-02-11,Linearly Coupled Directed Percolation in the Strong Coupling Regime,"We consider directed percolation processes for particle types A and B coupled unidirectionally by a transmutation reaction A -> B. It is shown that the strong coupling regime of this recently introduced problem defines a universality class with upper critical dimension d=6. Exact expressions are derived for the scaling dimensions in the inactive phase above d=4. Below d=4 the interactions of the normal directed percolation also get relevant.",0402316v1 2005-03-14,Transmission and Conversion of Energy by Coupled Soft Gears,"Dynamical aspects of coupled deformable gears are investigated to clarify the differences of mechanical properties between the machines consist of hard materials and those of soft materials. In particular, the performances of two functions, the transmission and the conversion of the energy, are compared between the hard and soft gears systems. First, the responses of the coupled gears against a constant torque working on one of gears are focused for two types of couplings; P) a pair gears are coupled, and T) three gears are coupled with forming a regular triangle. In systems with the coupling P), we obtain trivial results that the rotational energy can be transmitted to other gear only if these gears are hard enough. On the other hand, in systems with the coupling T), the transmission of the rotational energy to one of the other gears appears only if these gears are soft enough. Second, we show the responses of this system in which one of gears have contact with a high temperature heat bath and the other gears have contact with a 0 temperature heat bath. With the coupling T), the directional rotations appear in two gears having contact with 0 temperature heat bath. Here, the direction of these rotations change depending on the noise strength.",0503320v2 2007-01-08,Effects of degree distribution in mutual synchronization of neural networks,"We study the effects of the degree distribution in mutual synchronization of two-layer neural networks. We carry out three coupling strategies: large-large coupling, random coupling, and small-small coupling. By computer simulations and analytical methods, we find that couplings between nodes with large degree play an important role in the synchronization. For large-large coupling, less couplings are needed for inducing synchronization for both random and scale-free networks. For random coupling, cutting couplings between nodes with large degree is very efficient for preventing neural systems from synchronization, especially when subnetworks are scale-free.",0701138v1 2004-08-02,The purely gravitational generalization of spin-rotation couplings,"The nature of Mashhoon's spin-rotation coupling is the interaction between a particle spin (gravitomagnetic moment) and a gravitomagnetic field. Here we will consider the coupling of graviton spin to the weak gravitomagnetic fields by analyzing the Lagrangian density of weak gravitational field, and hence study the purely gravitational generalization of Mashhoon's spin-rotation couplings.",0408005v1 2006-03-24,"Torsion, Dilaton and Gauge Couplings","Non-Abelian gauge fields are traditionally not coupled to torsion due to violation of gauge invariance. However, it is possible to couple torsion to Yang-Mills fields while maintaining gauge invariance provided one accepts that the gauge couplings then become scalar fields. In the past this has been untenable from experimental constraints at the current epoch for the electromagnetic field at least. Recent researches on the ""landscape"" arising out of string theory provides for many scalar fields which eventually determine the various low energy parameters including gauge couplings in the universe. With this scenario, we argue that the very early universe provides a Riemann-Cartan geometry with non-zero torsion coupling to gauge fields. The torsion is just the derivative of gauge coupling (scalar) fields. As a result, in the evolution of the Universe, when the scalar (moduli) fields determine the geometry of the universe to be Riemannian, torsion goes to zero, implying that the associated modulus (and hence the gauge coupling) has a constant value. An equivalent view is that the modulus fixes the gauge coupling at some constant value causing the torsion to vanish as a consequence. Of course, when torsion vanishes we recover Einstein's theory for further evolution of the universe.",0603095v1 2002-05-10,Measurement of Boson Self Couplings at LEP and Search for Anomalies,"With center of mass energies up to 209 GeV of LEP II, massive W and Z bosons can be produced in pairs and jointly with photons. This allows to study boson-boson couplings. Since the W and Z bosons are unstable and decay into fermions, two- and four-fermion final states, accompanied possibly by photons, play an important role for these measurements. The couplings of the W to other bosons have been measured to be g1Z = 0.990+0.023-0.024, kappa_gamma = 0.896+0.058-0.056, and lambda_gamma = -0.023 +0.025 -0.023. They are in agreement with the Standard Model expectation of g1Z = 1, kappa_gamma = 1, and lambda_gamma = 0. No sign for couplings of three neutral bosons, parametrized by the couplings f_i^V and h_i^V, and for anomalous couplings of four gauge bosons, parametrized by a_0, a_n and a_c has been found.",0205024v3 2004-08-31,Higgs coupling constants as a probe of new physics,"We study new physics effects on the couplings of weak gauge bosons with the lightest CP-even Higgs boson ($h$), $hZZ$, and the tri-linear coupling of the lightest Higgs boson, $hhh$, at the one loop order, as predicted by the two Higgs doublet model. Those renormalized coupling constants can deviate from the Standard Model (SM) predictions due to two distinct origins; the tree level mixing effect of Higgs bosons and the quantum effect of additional particles in loop diagrams. The latter can be enhanced in the renormalized $hhh$ coupling constant when the additional particles show the non-decoupling property. Therefore, even in the case where the $hZZ$ coupling is close to the SM value, deviation in the $hhh$ coupling from the SM value can become as large as plus 100 percent, while that in the $hZZ$ coupling is at most minus 1 percent level. Such large quantum effect on the Higgs tri-linear coupling is distinguishable from the tree level mixing effect, and is expected to be detectable at a future linear collider.",0408364v2 1996-09-18,Strong-Weak Coupling Duality in Quantum Mechanics,"We present a strong-weak coupling duality for quantum mechanical potentials. Similarly to what happens in quantum field theory, it relates two problems with inverse couplings, leading to a mapping of the strong coupling regime into the weak one, giving information from the nonperturbative region of the parameters space. It can be used to solve exactly power-type potentials and to extract deep information about the energy spectra of polynomial ones.",9609156v1 2000-03-01,Measurability of the non-minimal coupling,"The ""measurability"" of the non-minimal coupling is discussed in the context of the effective field theory of gravity. Although there is no obvious motive for excluding a non-minimal scalar coupling from the theory, we conclude that for reasonable values of the coupling constant it makes only a very small correction.",0003008v1 2005-09-20,Shy couplings,"A pair of Markov processes is called a Markov coupling if both processes have the same transition probabilities and the pair is also a Markov process. We say that a coupling is ``shy'' if the processes never come closer than some (random) strictly positive distance from each other. We investigate whether shy couplings exist for several classes of Markov processes.",0509458v1 1996-07-26,Validity of the linear coupling approximation in heavy-ion fusion reactions at sub barrier energies,"The role of higher order coupling of surface vibrations to the relative motion in heavy-ion fusion reactions at near-barrier energies is investigated. The coupled channels equations are solved to all orders, and also in the linear and the quadratic coupling approximations. Taking $^{64}$Ni + $^{92,96}$Zr reactions as examples, it is shown that all order couplings lead to considerably improved agreement with the experimentally measured fusion cross sections and average angular momenta of the compound nucleus for such heavy nearly symmetric systems. The importance of higher order coupling is also examined for asymmetric systems like $^{16}$O + $^{112}$Cd, $^{144}$Sm, for which previous calculations of the fusion cross section seemed to indicate that the linear coupling approximation was adequate. It is shown that the shape of the barrier distributions and the energy dependence of the average angular momentum can change significantly when the higher order couplings are included, even for systems where measured fusion cross sections may seem to be well reproduced by the linear coupling approximation.",9607053v1 1999-09-22,Coupled non-equilibrium growth equations: Self-consistent mode coupling using vertex renormalization,"We find that studying the simplest of the coupled non-equilibrium growth equations of Barabasi by self-consistent mode coupling requires the use of dressed vertices. Using the vertex renormalization, we find a roughness exponent which already in the leading order is quite close to the numerical value.",9909046v1 2003-07-07,Suppressing Weak Ising Couplings: Tailored Gates for Quantum Computation,"I describe the use of techniques based on composite rotations to develop controlled phase gates in which the effects of weak Ising couplings are suppressed. A tailored composite phase gate is described which both suppresses weak couplings and is relatively insensitive to systematic errors in the size of strong couplings.",0307050v1 2006-11-10,Non-Markovian Decay and Lasing Condition in an Optical Microcavity Coupled to a Structured Reservoir,"The decay dynamics of the classical electromagnetic field in a leaky optical resonator supporting a single mode coupled to a structured continuum of modes (reservoir) is theoretically investigated, and the issue of threshold condition for lasing in presence of an inverted medium is comprehensively addressed. Specific analytical results are given for a single-mode microcavity resonantly coupled to a coupled resonator optical waveguide (CROW), which supports a band of continuous modes acting as decay channels. For weak coupling, the usual exponential Weisskopf-Wigner (Markovian) decay of the field in the bare resonator is found, and the threshold for lasing increases linearly with the coupling strength. As the coupling between the microcavity and the structured reservoir increases, the field decay in the passive cavity shows non exponential features, and correspondingly the threshold for lasing ceases to increase, reaching a maximum and then starting to decrease as the coupling strength is further increased. A singular behavior for the ""laser phase transition"", which is a clear signature of strong non-Markovian dynamics, is found at critical values of the coupling between the microcavity and the reservoir.",0611113v1 2007-05-24,Ground-state long-range order in quasi-one-dimensional Heisenberg quantum antiferromagnets: High-order coupled-cluster calculations,"We investigate the ground-state magnetic long-range order of quasi-one-dimensional quantum Heisenberg antiferromagnets for spin quantum numbers s=1/2 and s=1. We use the coupled cluster method to calculate the sublattice magnetization in dependence on the inter-chain coupling. We find that for the unfrustrated spin-1/2 system an infinitesimal inter-chain coupling is sufficient to stabilize magnetic long-range order, which is in agreement with results obtained by some other methods. For s=1 we find that a finite inter-chain coupling of about 10% of the in-chain coupling is necessary to stabilize magnetic long-range order. Furthermore, we consider a quasi one-dimensional spin-1/2 system, where a frustrating next-nearest neighbor in-chain coupling is included. We find that for stronger frustration also a finite inter-chain coupling is necessary to have magnetic long-range order in the ground state, where the strength of the inter-chain coupling necessary to establish magnetic long-range order is related to the size of the spin gap of the isolated chain.",0705.3582v2 2007-07-16,Odderon with a running coupling constant,"The running coupling is introduced into the equation for the odderon via the bootstrap relation. It is shown that the previously found odderon state with a maximal intercept, which is constructed from antisymmetric pomeron wave function, continues to exist in the running coupling case. Its intercept is found to remain equal to unity independent of the behaviour assumed for the running coupling at low momenta.",0707.2314v1 2007-07-17,Desynchronization of pulse-coupled oscillators with delayed excitatory coupling,"Collective behavior of pulse-coupled oscillators has been investigated widely. As an example of pulse-coupled networks, fireflies display many kinds of flashing patterns. Mirollo and Strogatz (1990) proposed a pulse-coupled oscillator model to explain the synchronization of South East Asian fireflies ({\itshape Pteroptyx malaccae}). However, transmission delays were not considered in their model. In fact, the presence of transmission delays can lead to desychronization. In this paper, pulse-coupled oscillator networks with delayed excitatory coupling are studied. Our main result is that under reasonable assumptions, pulse-coupled oscillator networks with delayed excitatory coupling can not achieve complete synchronization, which can explain why another species of fireflies ({\itshape Photinus pyralis}) rarely synchronizes flashing. Finally, two numerical simulations are given. In the first simulation, we illustrate that even if all the initial phases are very close to each other, there could still be big variations in the times to process the pulses in the pipeline. It implies that asymptotical synchronization typically also cannot be achieved. In the second simulation, we exhibit a phenomenon of clustering synchronization.",0707.2442v1 2007-10-26,Unitarity constraints on MSSM trilinear couplings,"For MSSM phenomenology, soft SUSY breaking dimension-three operators are important, in particular the couplings between Higgs bosons and squarks. In scattering processes, perturbative unitarity is violated at modest center-of-mass energy if these couplings are much larger than the masses of the scalar particles involved. Assuming perturbative unitarity, constraints on the trilinear couplings can be determined using a computer program that we have developed.",0710.5175v1 2007-11-16,Intermittency transition to generalized synchronization in coupled time-delay systems,"In this paper, we report the nature of transition to generalized synchronization (GS) in a system of two coupled scalar piecewise linear time-delay systems using the auxiliary system approach. We demonstrate that the transition to GS occurs via on-off intermittency route and also it exhibits characteristically distinct behaviors for different coupling configurations. In particular, the intermittency transition occurs in a rather broad range of coupling strength for error feedback coupling configuration and in a narrow range of coupling strength for direct feedback coupling configuration. It is also shown that the intermittent dynamics displays periodic bursts of period equal to the delay time of the response system in the former case, while they occur in random time intervals of finite duration in the latter case. The robustness of these transitions with system parameters and delay times has also been studied for both linear and nonlinear coupling configurations. The results are corroborated analytically by suitable stability conditions for asymptotically stable synchronized states and numerically by the probability of synchronization and by the transition of \emph{sub}Lyapunov exponents of the coupled time-delay systems. We have also indicated the reason behind these distinct transitions by referring to unstable periodic orbit theory of intermittency synchronization in low-dimensional systems.",0711.2611v1 2009-01-20,Coupled Mode Effects on Energy Transfer Rates in Two Temperature Plasmas,"We investigate the effects of collective modes on the temperature relaxation rates in fully coupled electron-ion systems. Firstly, the well-understood limit of weakly coupled plasmas is considered and the coupled mode formula within the random phase approximation is derived starting from the Lenard-Balescu kinetic equation. We show how the frequency integration can be performed by standard methods without applying additional approximations. Due to the well-defined approximation scheme, the results can serve as a benchmark for more approximate theories and numerical simulations in this limit. The coupled mode electron-ion transfer rates show a considerable reduction compared to the Fermi-Golden Rule approach for certain parameters and very small changes for other systems. We demonstrate how these coupled mode effects are connected to the occurrence of ion acoustic modes and under which conditions they occur. Interestingly, coupled mode effects can also occur for plasmas with very high electron temperatures; a regime, where the Landau-Spitzer approach is believed to give accurate results. Finally, we extend the approach to systems with strongly coupled ions by applying static local field corrections. This extension can substantially increase the coupled mode effects.",0901.3101v1 2009-02-19,Two atomic quantum dots interacting via coupling to BECs,"We consider a system of three weakly coupled Bose-Einstein condensates and two atomic quantum dots embedded in the barriers between the condensates. Each dot is coupled to two neighboring condensates by optical transitions and can be described as a two-state system, or a pseudospin 1/2. Although there is no direct coupling between the dots, an effective interaction between the pseudospins is induced due to their coupling to the condensate reservoirs. We investigate this effective interaction, depending on the strengths of the dot-condensate coupling T and the direct coupling J between the condensates. In particular, we show that an initially ferromagnetic arrangement of the two pseudospins stays intact even for large T/J. However, antiferromagnetically aligned spins undergo peculiar ""breathing"" modes for weak coupling T/J<1, while for strong coupling the behaviour of the spins becomes uncorrelated.",0902.3406v1 2009-02-28,Quantum Measurements of Coupled Two-Level Systems,"We propose an approach to measuring nonresonant coupled systems, which gives a parametrically smaller error than the conventional fast projective measurements. The approach takes into account that, due to the coupling, excitations are not entirely localized on individual systems. It combines high spectral selectivity of the detector with temporal resolution and uses the ideas of the quantum diffusion theory. The results bear on quantum computing with perpetually coupled qubits.",0903.0012v1 2009-04-29,Electron-vibron coupling in suspended carbon nanotube quantum dots,"Motivated by recent experiments, we investigate the electron-vibron coupling in suspended carbon nanotube quantum dots, starting with the electron-phonon coupling of the underlying graphene layer. We show that the coupling strength depends sensitively on the type of vibron and is strongly sample dependent. The coupling strength becomes particularly strong when inhomogeneity-induced electronic quantum dots are located near regions where the vibronic mode is associated with large strain. Specifically, we find that the longitudinal stretching mode and the radial breathing mode are coupled via the strong deformation potential, while twist modes couple more weakly via a mechanism involving modulation of the electronic hopping amplitudes between carbon sites. A special case are bending modes: for symmetry reasons, their coupling is only quadratic in the vibron coordinate. Our results can explain recent experiments on suspended carbon nanotube quantum dots which exibit vibrational sidebands accompanied by the Franck-Condon blockade with strong electron-vibron coupling.",0904.4653v1 2009-08-03,Nonlinearly coupled harmonic oscillators: high frequency oscillations yield synchronization,"Synchronization of coupled harmonic oscillators is investigated. Coupling considered here is pairwise, unidirectional, and described by a nonlinear function (whose graph resides in the first and third quadrants) of some projection of the relative distance (between the states of the pair being coupled) vector. Under the assumption that the interconnection topology defines a connected graph, it is shown that the synchronization manifold is semiglobally practically asymptotically stable in the frequency of oscillations.",0908.0207v1 2010-01-19,Signature of strong atom-cavity interaction on critical coupling,"We study a critically coupled cavity doped with resonant atoms with metamaterial slabs as mirrors. We show how resonant atom-cavity interaction can lead to a splitting of the critical coupling dip. The results are explained in terms of the frequency and lifetime splitting of the coupled system.",1001.3205v1 2010-08-19,A nonlocal connection between certain linear and nonlinear ordinary differential equations : Extension to coupled equations,"Identifying integrable coupled nonlinear ordinary differential equations (ODEs) of dissipative type and deducing their general solutions are some of the challenging tasks in nonlinear dynamics. In this paper we undertake these problems and unearth two classes of integrable coupled nonlinear ODEs of arbitrary order. To achieve these goals we introduce suitable nonlocal transformations in certain linear ODEs and generate the coupled nonlinear ODEs. In particular, we show that the problem of solving these classes of coupled nonlinear ODEs of any order, effectively reduces to solving a single first order nonlinear ODE. We then describe a procedure to derive explicit general solutions for the identified integrable coupled ODEs, when the above mentioned first order nonlinear ODE reduces to a Bernoulli equation. The equations which we generate and solve include the two coupled versions of modified Emden equations (in second order), coupled versions of Chazy equations (in third order) and their variants, higher dimensional coupled Ricatti and Abel chains as well as a new integrable chain and higher order equations.",1008.3232v2 2010-09-02,Running Coupling Corrections to High Energy Inclusive Gluon Production,"We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. In the final answer for the cross section the three powers of fixed coupling are replaced by seven factors of running coupling, five in the numerator and two in the denominator, forming a 'septumvirate' of running couplings, analogous to the 'triumvirate' of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. It is interesting to note that the two running couplings in the denominator of the 'septumvirate' run with complex-valued momentum scales, which are complex conjugates of each other, such that the production cross section is indeed real. We use our lowest-order result to conjecture how running coupling corrections may enter the full fixed-coupling kT-factorization formula for gluon production which includes non-linear small-x evolution.",1009.0545v2 2011-01-17,Hydrodynamic coupling between two fluid membranes,"The coupled in-plane diffusion dynamics between point-particles embedded in stacked fluid membranes are investigated. We calculate the contributions to the coupling longitudinal and transverse diffusion coefficients due to particle motion within the different as well as the same membranes. The stacked geometry leads to a hydrodynamic coupling between the two membranes.",1101.3128v1 2011-03-16,Adjoint methods for obstacle problems and weakly coupled systems of PDE,"The adjoint method, recently introduced by Evans, is used to study obstacle problems, weakly coupled systems, cell problems for weakly coupled systems of Hamilton-Jacobi equations, and weakly coupled systems of obstacle type. In particular, new results about the speed of convergence of common approximation procedures are derived.",1103.3226v2 2011-08-31,Plasma conductivity at finite coupling,"By taking into account the full order(\alpha'^3) type IIB string theory corrections to the supergravity action, we compute the leading finite 't Hooft coupling order(\lambda^{-3/2}) corrections to the conductivity of strongly-coupled SU(N) {\cal {N}}=4 supersymmetric Yang-Mills plasma in the large N limit. We find that the conductivity is enhanced by the corrections, in agreement with the trend expected from previous perturbative weak-coupling computations.",1108.6306v1 2011-09-21,"Electron transport through a coupled double dot molecule: role of inter-dot coupling, phononic and dissipative effects","In this work, we have investigated conduction through an artificial molecule comprising two coupled quantum dots. The question addressed is the role of inter-dot coupling on electronic transport. We find that the current through the molecule exhibits step-like features as a function of the voltage between the leads, where the step size increases as the inter-dot coupling is increased. These step-like features disappear with increasing tunneling rate from the leads, but we find that in the presence of coupling, this smooth behavior is not observed rather two kinks are seen in the current voltage curve. This shows that the resolution of the two levels persists if there is finite inter-dot coupling. Furthermore, we also consider the effects of electron-phonon interaction as well as dissipation on conduction in this system. Phononic side bands in the differential conductance survive for finite inter-dot coupling even for strong lead to molecule coupling.",1109.4477v1 2012-03-06,Rotational optomechanical coupling of a spinning dielectric sphere,"We formulate a non-relativistic Hamiltonian in order to describe how the rotational degrees of freedom of a dielectric sphere and quantized light fields are coupled. Such an interaction is shown to take a form of angular momentum coupling governed by the field angular momentum inside the dielectric. As a specific example, we show that the coupling due to a single whispering gallery mode can lead to precession dynamics and frequency shifts of light.",1203.1121v1 2012-03-09,Critical Reinvestigation on Vibronic Couplings in Picene from View of Vibronic Coupling Density Analysis,"Vibronic coupling constants in the monoanionic, trianionic, and excited states of picene are evaluated from the total energy gradients using the density functional theory. Employing the calculated vibronic coupling constants in the excited state of the neutral molecule, electron energy loss spectrum (EELS) is simulated to be compared with the experimental spectrum. The calculated vibronic coupling constants are analyzed in terms of the vibronic coupling density which enables us to analyze vibronic couplings based on the relation between the electronic and vibrational structures. The vibronic coupling constants reported by Kato et al. [J. Chem. Phys. 116, 3420 (2002) and Phys. Rev. Lett. 107, 077001 (2011)] are critically discussed based on the vibronic coupling density analysis.",1203.2013v1 2012-03-30,Minimal coupling in oscillator models of quantum dissipation,"The dissipative harmonic oscillator has two representations. In the first representation the central oscillator couples with its position to an oscillator bath. In the second one it couples with its momentum to the bath. Both representations are related by a unitary transformation. If the central oscillator couples with its position and momentum to two independent baths, no such unitary transformation exists. We discuss two possible models of this type and their physical relevance.",1203.6804v1 2012-06-04,Circuit QED using a semiconductor double quantum dot,"Vacuum Rabi splitting is observed in a coupled qubit-resonator system consisting of a GaAs double quantum dot and a coplanar waveguide resonator. Derived values of the qubit-resonator coupling strength and the decoherence rate indicate strong coupling, which assures distinct vacuum Rabi oscillation in the system. The amplitude of decoherence is reasonably interpreted in terms of the coupling of electrons to piezoelectric acoustic phonons in GaAs.",1206.0674v1 2012-07-17,Asymptotic Dynamics of a Class of Coupled Oscillators Driven by White Noises,"This paper is devoted to the study of the asymptotic dynamics of a class of coupled second order oscillators driven by white noises. It is shown that any system of such coupled oscillators with positive damping and coupling coefficients possesses a global random attractor. Moreover, when the damping and the coupling coefficients are sufficiently large, the global random attractor is a one-dimensional random horizontal curve regardless of the strength of the noises, and the system has a rotation number, which implies that the oscillators in the system tend to oscillate with the same frequency eventually and therefore the so called frequency locking is successful. The results obtained in this paper generalize many existing results on the asymptotic dynamics for a single second order noisy oscillator to systems of coupled second order noisy oscillators. They show that coupled damped second order oscillators with large damping have similar asymptotic dynamics as the limiting coupled first order oscillators as the damping goes to infinite and also that coupled damped second order oscillators have similar asymptotic dynamics as their proper space continuous counterparts, which are of great practical importance.",1207.3864v1 2012-07-25,Higgs Couplings after the Discovery,"Following the ATLAS and CMS analyses presented around ICHEP 2012 we determine the individual Higgs couplings. The new data allow us to specifically test the effective coupling to photons. We find no significant deviation from the Standard Model in any of the Higgs couplings.",1207.6108v2 2012-09-28,"Spin-Hamilton Operator, Graviton-Photon Coupling and an Eigenvalue Problem","We solve exactly the eigenvalue problem for a spin Hamilton operator describing graviton-photon coupling. Entanglement of the eigenstates are also studied. Other spin-coupled Hamilton operators involving spin-1 and spin-2 are also investigated and compared.",1209.6494v2 2012-10-28,Boson features in STM spectra of cuprate superconductors: Weak-coupling phenomenology,"We derive the shape of the high-energy features due to a weakly coupled boson in cuprate superconductors, as seen experimentally in Bi_2 Sr_2 Ca_1 Cu_2 O_8+x (BSCCO) by Lee et al. [Nature (London) 442, 546 (2006)]. A simplified model is used of d-wave Bogoliubov quasiparticles coupled to Einstein oscillators with a momentum-independent electron-boson coupling and an analytic fitting form is derived, which allows us (a) to extract the boson mode's frequency and (b) to estimate the electron-boson coupling strength. We further calculate the maximum possible superconducting gap due to an Einstein oscillator with the extracted electron-boson coupling strength, which is found to be less than 0.2 times of the observed gap indicating at the observed boson's non-dominant role in the superconductivity's mechanism. The extracted momentum-independent electron-boson coupling parameter (that we show a posteriori to indeed be in the weak-coupling regime) is then to be interpreted as an (band-structure detail dependent weighted) average over the Brillouin zone of the actual momentum-dependent electron-boson coupling in BSCCO.",1210.7490v2 2012-11-18,"Classical FEM-BEM coupling methods: nonlinearities, well-posedness, and adaptivity","We consider a (possibly) nonlinear interface problem in 2D and 3D, which is solved by use of various adaptive FEM-BEM coupling strategies, namely the Johnson-N\'ed\'elec coupling, the Bielak-MacCamy coupling, and Costabel's symmetric coupling. We provide a framework to prove that the continuous as well as the discrete Galerkin solutions of these coupling methods additionally solve an appropriate operator equation with a Lipschitz continuous and strongly monotone operator. Therefore, the coupling formulations are well-defined, and the Galerkin solutions are quasi-optimal in the sense of a C\'ea-type lemma. For the respective Galerkin discretizations with lowest-order polynomials, we provide reliable residual-based error estimators. Together with an estimator reduction property, we prove convergence of the adaptive FEM-BEM coupling methods. A key point for the proof of the estimator reduction are novel inverse-type estimates for the involved boundary integral operators which are advertized. Numerical experiments conclude the work and compare performance and effectivity of the three adaptive coupling procedures in the presence of generic singularities.",1211.4225v1 2012-11-19,Finite-size scaling in globally coupled phase oscillators with a general coupling scheme,"We investigate a critical exponent related to synchronization transition in globally coupled nonidentical phase oscillators. The critical exponents of susceptibility, correlation time, and correlation size are significant quantities to characterize fluctuations in coupled oscillator systems of large but finite size and understand a universal property of synchronization. These exponents have been identified for the sinusoidal coupling but not fully studied for other coupling schemes. Herein, for a general coupling function including a negative second harmonic term in addition to the sinusoidal term, we numerically estimate the critical exponent of the correlation size, denoted by $\nu_+$, in a synchronized regime of the system by employing a non-conventional statistical quantity. First, we confirm that the estimated value of $\nu_+$ is approximately 5/2 for the sinusoidal coupling case, which is consistent with the well-known theoretical result. Second, we show that the value of $\nu_+$ increases with an increase in the strength of the second harmonic term. Our result implies that the critical exponent characterizing synchronization transition largely depends on the coupling function.",1211.4364v1 2013-03-11,Crossover between integer and fractional vortex lattices in coherently coupled two-component Bose-Einstein condensates,"We study effects of the internal coherent (Rabi) coupling in vortex lattices in two-component BECs under rotation. We find how the vortex lattices without the Rabi coupling known before are connected to the Abrikosov lattice of integer vortices with increasing the Rabi coupling. We find that 1) for small Rabi couplings, fractional vortices in triangular or square lattice for small or large inter-component coupling constitute hexamers or tetramers, namely multi-dimer bound states made of six or four vortices, respectively, 2) these bound states are broken into a set of dimers at intermediate Rabi couplings, and 3) vortices change their partners in various ways depending on the inter-component coupling to organize themselves for constituting the Abrikosov lattice of integer vortices at strong Rabi couplings.",1303.2592v3 2013-03-14,On the skew-symmetric character of the couple-stress tensor,"In this paper, the skew-symmetric character of the couple-stress tensor is established as the result of arguments from tensor analysis. Consequently, the couple-stress pseudo-tensor has a true vectorial character. The fundamental step in this development is that the isotropic couple-stress tensor cannot exist.",1303.3569v2 2013-03-21,Synchronization in hyperchaotic time-delayed electronic oscillators coupled indirectly via a common environment,"The present paper explores the synchronization scenario of hyperchaotic time-delayed electronic oscillators coupled indirectly via a common environment. We show that depending upon the coupling parameters a hyperchaotic time-delayed system can show in-phase or complete synchronization, and also inverse-phase or anti-synchronization. This paper reports the first experimental confirmation of synchronization of hyperchaos in time-delayed electronic oscillators coupled indirectly through a common environment. We confirm the occurrence of in-phase and inverse-phase synchronization phenomena in the coupled system through the dynamical measures like generalized autocorrelation function, correlation of probability of recurrence, and the concept of localized sets computed directly from the experimental time-series data. We also present a linear stability analysis of the coupled system. The experimental and analytical results are further supported by the detailed numerical analysis of the coupled system. Apart from the above mentioned measures, we numerically compute another quantitative measure, namely, Lyapunov exponent spectrum of the coupled system that confirms the transition from the in-phase (inverse-phase) synchronized state to the complete (anti-) synchronized state with the increasing coupling strength.",1303.5339v1 2013-03-26,Predicting the statistics of wave transport through chaotic cavities by the Random Coupling Model: a review and recent progress,"In this review, a model (the Random Coupling Model) that gives a statistical description of the coupling of radiation into and out of large enclosures through localized and/or distributed channels is presented. The Random Coupling Model combines both deterministic and statistical phenomena. The model makes use of wave chaos theory to extend the classical modal description of the cavity fields in the presence of boundaries that lead to chaotic ray trajectories. The model is based on a clear separation between the universal statistical behavior of the isolated chaotic system, and the deterministic coupling channel characteristics. Moreover, the ability of the random coupling model to describe interconnected cavities, aperture coupling, and the effects of short ray trajectories is discussed. A relation between the random coupling model and other formulations adopted in acoustics, optics, and statistical electromagnetics, is examined. In particular, a rigorous analogy of the random coupling model with the Statistical Energy Analysis used in acoustics is presented.",1303.6526v1 2013-11-13,Synchronization of Coupled Boolean Phase Oscillators,"We design, characterize, and couple Boolean phase oscillators that include state-dependent feedback delay. The state-dependent delay allows us to realize an adjustable coupling strength, even though only Boolean signals are exchanged. Specifically, increasing the coupling strength via the range of state-dependent delay leads to larger locking ranges in uni- and bi-directional coupling of oscillators in both experiment and numerical simulation with a piecewise switching model. In the unidirectional coupling scheme, we unveil asymmetric triangular-shaped locking regions (Arnold tongues) that appear at multiples of the natural frequency of the oscillators. This extends observations of a single locking region reported in previous studies. In the bidirectional coupling scheme, we map out a symmetric locking region in the parameter space of frequency detuning and coupling strength. Because of large scalability of our setup, our observations constitute a first step towards realizing large-scale networks of coupled oscillators to address fundamental questions on the dynamical properties of networks in a new experimental setting.",1311.2996v2 2013-11-13,BSM Theories Face Higgs Coupling data,"We discuss how much Higgs couplings (including the Higgs self coupling) can deviate from their Standard Model values, in different Beyond Standard Model (BSM) theories, if no other BSM states are accessible at the LHC. Then, we focus on supersymmetric theories and show that there is a connection between the mechanism to raise the Higgs mass and the pattern of Higgs coupling deviations.",1311.3040v1 2013-11-25,Existence of pulses in excitable media with nonlocal coupling,"We prove the existence of fast traveling pulse solutions in excitable media with non-local coupling. Existence results had been known, until now, in the case of local, diffusive coupling and in the case of a discrete medium, with finite-range, non-local coupling. Our approach replaces methods from geometric singular perturbation theory, that had been crucial in previous existence proofs, by a PDE oriented approach, relying on exponential weights, Fredholm theory, and commutator estimates.",1311.6508v1 2014-04-08,Coupled Matrix Factorization within Non-IID Context,"Recommender systems research has experienced different stages such as from user preference understanding to content analysis. Typical recommendation algorithms were built on the following bases: (1) assuming users and items are IID, namely independent and identically distributed, and (2) focusing on specific aspects such as user preferences or contents. In reality, complex recommendation tasks involve and request (1) personalized outcomes to tailor heterogeneous subjective preferences; and (2) explicit and implicit objective coupling relationships between users, items, and ratings to be considered as intrinsic forces driving preferences. This inevitably involves the non-IID complexity and the need of combining subjective preference with objective couplings hidden in recommendation applications. In this paper, we propose a novel generic coupled matrix factorization (CMF) model by incorporating non-IID coupling relations between users and items. Such couplings integrate the intra-coupled interactions within an attribute and inter-coupled interactions among different attributes. Experimental results on two open data sets demonstrate that the user/item couplings can be effectively applied in RS and CMF outperforms the benchmark methods.",1404.7467v2 2014-07-21,Gradient Estimates for Nonlinear Diffusion Semigroups by Coupling Methods,"Our purpose is to obtain gradient estimates for certain nonlinear partial differential equations by coupling methods. First we derive uniform gradient estimates for a certain semi-linear PDEs based on the coupling method introduced in Wang (2011) and the theory of backward SDEs. Then we generalize Wang's coupling to the $G$-expectation space and obtain gradient estimates for nonlinear diffusion semigroups, which correspond to the solutions of a certain fully nonlinear PDEs.",1407.5426v1 2014-08-29,High fidelity quantum state transfer in electromechanical systems with intermediate coupling,"Hybrid quantum systems usually consist of two or more subsystems, which may take the advantages of the different systems. Recently, the hybrid system consisting of circuit electromechanical subsystems have attracted great attention due to its advanced fabrication and scalable integrated photonic circuit techniques. Here, we propose a scheme for high fidelity quantum state transfer between a superconducting qubit and a nitrogen-vacancy center in diamond, which are coupled to a superconducting transmission-line resonator with coupling strength $g_1$ and a nanomechanical resonator with coupling strength $g_2$, respectively. Meanwhile, the two resonators are parametrically coupled with coupling strength $J$. The system dynamics, including the decoherence effects, is numerical investigated. It is found that both the small ($J \ll \{g_1, g_2\}$) and large ($J \gg \{g_1, g_2\}$) coupling regimes of this hybrid system can not support high fidelity quantum state transfer before significant technique advances. However, in the intermediate coupling regime ($J \sim g_1 \sim g_2$), in contrast to a conventional wisdom, high fidelity quantum information transfer can be implemented, providing a promising route towards high fidelity quantum state transfer in similar coupled resonators systems.",1408.7015v1 2014-10-01,Resurgence and Holomorphy: From Weak to Strong Coupling,"We analyze the resurgence properties of finite-dimensional exponential integrals which are prototypes for partition functions in quantum field theories. In these simple examples, we demonstrate that perturbation theory, even at arbitrarily weak coupling, fails as the argument of the coupling constant is varied. It is well-known that perturbation theory also fails at stronger coupling. We show that these two failures are actually intimately related. The formalism of resurgent transseries, which takes into account global analytic continuation properties, fixes both problems, and provides an arbitrarily accurate description of exact result for any value of coupling. This means that strong coupling results can be deduced by using merely weak coupling data. Finally, we give another perspective on resurgence theory by showing that the monodromy properties of the weak coupling results are in precise agreement with the monodromy properties of the strong-coupling expansions, obtained using analysis of the holomorphy structure of Picard-Fuchs equations.",1410.0388v3 2015-05-05,Numerical corrections to the strong coupling effective Polyakov-line action for finite T Yang-Mills theory,"We consider a three-dimensional effective theory of Polyakov lines derived previously from lattice Yang-Mills theory and QCD by means of a resummed strong coupling expansion. The effective theory is useful for investigations of the phase structure, with a sign problem mild enough to allow simulations also at finite density. In this work we present a numerical method to determine improved values for the effective couplings directly from correlators of the 4d Yang-Mills theory. For values of the gauge coupling up to the vicinity of the phase transition, the dominant short range effective coupling are well described by their corresponding strong coupling series. We provide numerical results also for the longer range interactions, Polyakov lines in higher representations as well as four-point interactions, and discuss the growing significance of non-local contributions as the lattice gets finer. Within this approach the critical Yang-Mills coupling $\beta_c$ is reproduced to better than one percent from a one-coupling effective theory on $N_\tau=4$ lattices while up to five couplings are needed on $N_\tau=8$ for the same accuracy.",1505.01021v1 2015-06-21,Giant enhancement of tunable optomechanical coupling via ultrarefractive medium,"Exploring the fundamental quantum behaviour of optomechanical resonators is of great interest recently but requires the realization of the strong coupling regime. We study the optical photon-phonon coupling of the so-called membrane in the middle (MITM) optomechanical system. Using coupled-mode theory we find that the optomechanical coupling is proportional to the electric susceptibility of the membrane. By considering the doping atoms or spins into the membrane and driving these appropriately we induce a tunable ultra-large refractive index without absorption which enhances the optomechanical coupling. Using this we predict an ultra-strong single-optical photon strong coupling with large quantum cooperativity for Er3+ dopants at low temperature, while Cr3+ in a Ruby membrane may display ultra-large quantum cooperativity at room temperature. Our scheme also can tune the strength of the coupling over a wide range and can also control whether the optomechanical force is attractive or repulsive. Our work opens a door for fundamental physics and applications relying on the realization of the strong coupling regime in quantum optomechanical systems.",1506.06315v1 2015-06-23,Mode coupling and photon antibunching in a bimodal cavity containing a dipole-quantum-emitter,"We study the effect of mode-coupling on a single-photon device in which a dipole-quantum-emitter (DQE) is embedded in a bimodal whispering-gallery-mode cavity (WGMC). A scatterer is used to induce mode coupling between counter-clockwise and clockwise propagating light fields, which interact with the DQE. In contrast to models for the interaction between a DQE and a (one-mode or two-mode) cavity field, we find that strong photon antibunching can occur even for a weak DQE-field coupling and large dephasing of the DQE, when mode coupling is introduced. We also find that mode coupling can make the device robust against either the frequency mismatch between cavity modes and the DQE or the coupling strength mismatch between the DQE and each mode in the two-mode cavity. Moreover, we find that these mismatches can be used to generate better antibunching in the weak DQE-field coupling regime. Our study shows that mode coupling in a bimodal cavity is very important for the realization of a good single-photon device.",1506.06889v1 2015-09-11,Relational reasoning via probabilistic coupling,"Probabilistic coupling is a powerful tool for analyzing pairs of probabilistic processes. Roughly, coupling two processes requires finding an appropriate witness process that models both processes in the same probability space. Couplings are powerful tools proving properties about the relation between two processes, include reasoning about convergence of distributions and stochastic dominance---a probabilistic version of a monotonicity property. While the mathematical definition of coupling looks rather complex and cumbersome to manipulate, we show that the relational program logic pRHL---the logic underlying the EasyCrypt cryptographic proof assistant---already internalizes a generalization of probabilistic coupling. With this insight, constructing couplings is no harder than constructing logical proofs. We demonstrate how to express and verify classic examples of couplings in pRHL, and we mechanically verify several couplings in EasyCrypt.",1509.03476v2 2016-01-12,"Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal","We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices.",1601.02736v1 2016-06-15,Double shadow of a regular phantom black hole as photons couple to Weyl tensor,"We have studied the shadow of a regular phantom black hole as photons couple to Weyl tensor. We find that the coupling yields that photons with different polarization directions propagate along different paths in the spacetime so that there exits double shadow for a black hole, which is quite different from that in the non-coupling case where only a single shadow emerges. The umbra of black hole increases with the phantom charge and decreases with the coupling strength. The dependence of the penumbra on the phantom charge and the coupling strength is converse to that of the umbra. Combining with the supermassive central object in our Galaxy, we estimated the shadow of the black hole as the photons couple to Weyl tensor. Our results show that the coupling brings richer behaviors of the propagation of coupled photon and the shadow of the black hole in the regular phantom black hole spacetime.",1606.04634v2 2017-02-23,Current in nanojunctions : Effects of reservoir coupling,"We study the effect of system reservoir coupling on currents flowing through quantum junctions. We consider two simple double-quantum dot configurations coupled to two external fermionic reservoirs and study the net current flowing between the two reservoirs. The net current is partitioned into currents carried by the eigenstates of the system and by the coherences between the eigenstates induced due to coupling with the reservoirs. We find that current carried by populations is always positive whereas current carried by coherences are negative for large couplings. This results in a non-monotonic dependence of the net current on the coupling strength. We find that in certain cases, the net current can vanish at large couplings due to cancellation between currents carried by the eigenstates and by the coherences. These results provide new insights into the non-trivial role of system-reservoir couplings on electron transport through quantum dot junctions. In the presence of weak coulomb interactions, net current as a function of system reservoir coupling strength shows similar trends as for the non-interacting case.",1702.07122v2 2017-08-16,Amplitude death in a ring of nonidentical nonlinear oscillators with unidirectional coupling,"We study the collective behaviors in a ring of coupled nonidentical nonlinear oscillators with unidirectional coupling, of which natural frequencies are distributed in a random way. We find the amplitude death phenomena in the case of unidirectional couplings and discuss the differences between the cases of bidirectional and unidirectional couplings. There are three main differences; there exists neither partial amplitude death nor local clustering behavior but oblique line structure which represents directional signal flow on the spatio-temporal patterns in the unidirectional coupling case. The unidirectional coupling has the advantage of easily obtaining global amplitude death in a ring of coupled oscillators with randomly distributed natural frequency. Finally, we explain the results using the eigenvalue analysis of Jacobian matrix at the origin and also discuss the transition of dynamical behavior coming from connection structure as coupling strength increases.",1708.04736v1 2017-08-16,Inductively shunted transmon qubit with tunable transverse and longitudinal coupling,"We present the design of an inductively shunted transmon qubit with flux-tunable coupling to an embedded harmonic mode. This circuit construction offers the possibility to flux-choose between pure transverse and pure longitudinal coupling, that is coupling to the $\sigma_x$ or $\sigma_z$ degree of freedom of the qubit. While transverse coupling is the coupling type that is most commonly used for superconducting qubits, the inherently different longitudinal coupling has some remarkable advantages both for readout and for the scalability of a circuit. Being able to choose between both kinds of coupling in the same circuit provides the flexibility to use one for coupling to the next qubit and one for readout, or vice versa. We provide a detailed analysis of the system's behavior using realistic parameters, along with a proposal for the physical implementation of a prototype device.",1708.04917v2 2018-04-11,Analysis of the non-stationary model of coupled oscillators with inductive coupling,"The model of coupled oscillators plays an important role in modern physics. It is used for description of various processes: from vibrations atoms in solid states to electromagnetic oscillations in slow-wave structures. The model with short-range coupling is the most widely used, for which a separate oscillator is coupled with two adjacent ones only. There are two main types of oscillators coupling: capacitive (electric, power) and inductive (magnetic, inertial). In the first case, the coupling is proportional to the amplitudes of oscillations in the adjacent cells, in the second one - to the second derivative of these amplitudes. For numerical study of dynamics of a system that can be described by a model of coupled oscillators with an inductive coupling, it is necessary to find explicit expressions for the second derivatives of the amplitudes. To find these expressions, we propose to use the method that is based on the solution of difference equations. The results of the analysis of this method are given in the paper.",1804.03832v1 2018-04-23,Demonstration of an effective ultrastrong coupling between two oscillators,"When the coupling rate between two quantum systems becomes as large as their characteristic frequencies, it induces dramatic effects on their dynamics and even on the nature of their ground state. The case of a qubit coupled to a harmonic oscillator in this ultrastrong coupling regime has been investigated theoretically and experimentally. Here, we explore the case of two harmonic oscillators in the ultrastrong coupling regime. Specifically, we realize an analog quantum simulation of this coupled system by dual frequency pumping a nonlinear superconducting circuit. The pump amplitudes directly tune the effective coupling rate. We observe spectroscopic signature of a mode hybridization that is characteristic of the ultrastrong coupling. Further we experimentally demon- strate a key property of the ground state of this simulated ultrastrong coupling between modes by observing simultaneous single-mode and two-mode squeezing of the radiated field below vacuum fluctuations.",1804.08705v1 2018-11-18,The inverse problem of two-state quantum systems with non-adiabatic static linear coupling,"We consider the inverse problem of determining the coupling coefficients in a two-state Schr\""odinger system. We prove a Lipschitz stability inequality for the zeroth and first order coupling terms by finitely many partial lateral measurements of the solution to the coupled Schr\""odinger equations.",1811.07302v2 2014-03-03,Electromagnetically induced transparency like transmission in a metamaterial composed of cut-wire pairs with indirect coupling,"We theoretically and numerically investigate metamaterials composed of coupled resonators with indirect coupling. First, we theoretically analyze a mechanical model of coupled resonators with indirect coupling. The theoretical analysis shows that an electromagnetically induced transparency (EIT)-like phenomenon with a transparency bandwidth narrower than the resonance linewidths of the constitutive resonators can occur in the metamaterial with strong indirect coupling. We then numerically examine the characteristics of the metamaterial composed of coupled cut-wire pairs using a finite-difference time-domain (FDTD) method. The FDTD simulation confirms that an EIT-like transparency phenomenon occurs in the metamaterial owing to indirect coupling. Finally, we compare the results of the theoretical and numerical analyses. The behavior of the EIT-like metamaterial is found to be well described by the mechanical model of the coupled resonators.",1403.0400v1 2014-03-04,Nonminimal GUT inflation after Planck results,"In the present work we study GUT Coleman-Weinberg inflation with a nonminimal coupling to gravity. In this kind of model one usually finds that either the nonminimal coupling is large or the inflaton self-coupling in unnaturally small. We have shown here that the model is in agreement with the recent results from Planck for natural values of the couplings.",1403.0931v1 2017-01-11,Signatures of strong coupling on nanoparticles: Revealing absorption anticrossing by tuning the dielectric environment,"Strongly coupled plasmon-exciton systems offer promising applications in nanooptics. The classification of the coupling regime is currently debated both from experimental and theoretical perspectives. We present a method to unambiguously identify strong coupling in plasmon-exciton core-shell nanoparticles by measuring true absorption spectra of the system. We investigate the coupling of excitons in J-aggregates to the localized surface plasmon polaritons on gold nanospheres and nanorods by fine-tuning the plasmon resonance via layer-by-layer deposition of polyelectrolytes. While both structures show a characteristic anticrossing in extinction and scattering experiments, the careful assessment of the systems' light absorption reveals that strong coupling of the plasmon to the exciton is only present in the nanorod system. In a phenomenological model of two classical coupled oscillators, intermediate coupling strengths split up only the resonance frequency of the light-driven oscillator, while the other one still dissipates energy at its original frequency. Only in the strong-coupling limit, both oscillators split up the frequencies at which they dissipate energy, qualitatively explaining our experimental finding.",1701.02907v1 2018-04-28,Spin-1 Bosons in the Presence of Spin-orbit Coupling,"In this paper, I'm going to talk about the theoretical and experimental progress in studying spin-orbit coupled spin-1 bosons. Realization of spin-orbit coupled quantum gases opens a new avenue in cold atom physics. In particular, the interplay between spin-orbit coupling and inter-atomic interaction leads to many intriguing phenomena. Moreover, the non-zero momentum of ground states can be controlled by external fields, which allows for good quantum control.",1805.00001v1 2009-12-03,Critical coupling in a system of two coupled negative index medium layers,"We study critical coupling (CC) in a system of two coupled negative index medium (NIM) layers leading to near-total suppression of both reflection and transmission at specified frequencies. The tunability of the CC frequency is demonstrated by varying the angle of incidence retaining the full causal response for the NIM materials.",0912.0575v1 2012-04-12,Symmetric coupling of four spin-1/2 systems,"We address the non-binary coupling of identical angular momenta based upon the representation theory for the symmetric group. A correspondence is pointed out between the complete set of commuting operators and the reference-frame-free subsystems. We provide a detailed analysis of the coupling of three and four spin-1/2 systems and discuss a symmetric coupling of four spin-1/2 systems.",1204.2615v1 2014-06-03,"Comparing electron-phonon coupling strength in diamond, silicon and silicon carbide: First-principles study","Renormalization of the electronic band gap due to electron-phonon coupling in the tetrahedral semiconductors diamond, silicon and cubic silicon carbide is studied from first principles. There is a marked difference between the coupling of the vibrational state to the valence band maximum and to the conduction band minimum. The strength of phonon coupling to the valence band maximum is similar between the three systems and is dominated by vibrations that change the bond length. The coupling strength to the conduction band minimum differs significantly in diamond, silicon carbide and silicon. In diamond, the coupling is dominated by six small pockets of vibrational states in the phonon Brillouin zone, that are ultimately responsible for the stronger electron-phonon coupling in this material. Our results represent a first step towards the development of an a priori understanding of electron-phonon coupling in semiconductors and insulators, that should aid the design of materials with tailored electron-phonon coupling properties.",1406.0654v1 2017-06-15,Thermal rectification and negative differential thermal conductance in harmonic chains with nonlinear system-bath coupling,"Thermal rectification and negative differential thermal conductance were realized in harmonic chains in this work. We used the generalized Caldeira-Leggett model to study the heat flow. In contrast to the most previous studies considering only the linear system-bath coupling, we considered the nonlinear system-bath coupling based on recent experiment [A. Eichler \emph{et al.}, Nat. Nanotech. \textbf{6}, 339 (2011)]. When the linear coupling constant is weak, the multiphonon processes induced by the nonlinear coupling allow more phonons transport across the system-bath interface and hence the heat current is enhanced. Consequently, thermal rectification and negative differential thermal conductance are achieved when the nonlinear couplings are asymmetric. However, when the linear coupling constant is strong, the umklapp processes dominate the multiphonon processes. Nonlinear coupling suppresses the heat current. Thermal rectification is also achieved. But the direction of rectification is reversed comparing to the results of weak linear coupling constant.",1706.04706v1 2017-06-26,"Fluctuating, Lorentz-force-like coupling of Langevin equations and heat flux rectification","In a description of physical systems with Langevin equations, interacting degrees of freedom are usually coupled through symmetric parameter matrices. This coupling symmetry is a consequence of time-reversal symmetry of the involved conservative forces. If coupling parameters fluctuate randomly, the resulting noise is called multiplicative. For example, mechanical oscillators can be coupled through a fluctuating, symmetric matrix of spring ""constants"". Such systems exhibit well-studied instabilities. In this note, we study the complementary case of antisymmetric, time-reversal symmetry breaking coupling that can be realized with Lorentz forces or various gyrators. We consider the case that these antisymmetric couplings fluctuate. This type of multiplicative noise does not lead to instabilities in the stationary state but renormalizes the effective non-equilibrium friction. Fluctuating Lorentz-force-like couplings also allow to control and rectify heat transfer. A noteworthy property of this mechanism of producing asymmetric heat flux is that the controlling couplings do not exchange energy with the system..",1706.08367v3 2017-12-11,Discrete Shilnikov attractor and chaotic dynamics in the system of five identical globally coupled phase oscillators with biharmonic coupling,"We argue that a discrete Shilnikov attractor exists in the system of five identical globally coupled phase oscillators with biharmonic coupling. We explain the scenario that leads to birth of this kind of attractor and numerically illustrate the sequence of bifurcations that supports our statement.",1712.03839v1 2020-12-08,Conditional Stability of Coefficients Inverse Problem for Strongly Coupled Schrödinger Equations,"This paper concerns inverse problems for strongly coupled Schr\""odinger equations. The purpose of this inverse problem is to retrieve a stationary potential in the strongly coupled Schr\""odinger equations from either boundary or internal measurements. Two stability results are derived from a new Carleman estimate for the strongly coupled Schr\""odinger equations.",2012.04292v1 2020-12-29,Nonreciprocal Multi-mode and Indirect Couplings in Cavity Magnonics,"We investigate the magnon-photon couplings by employing a small magnet within an irregular resonant cavity, which leads to a desirable nonreciprocity with a big isolation ratio. Moreover, the higher-order couplings between the spin wave modes with the polarized photon modes also exhibit the nonreciprocity. These couplings between polarized photon and spin waves could be regarded as an indirect multi-modes coupling between the ferromagnetic resonance (FMR) mode and spin wave mode magnons mediated by the cavity mode photons. We also derive a coupling matrix to predict the characteristics of this kind of indirect coupling. The existence of the indirect couplings broaden the field range of the nonreciprocity of the system. The achieved nonreciprocal multi-mode magnon-photon couplings in a single system offer a feasible method to improve the signal transmission quality.",2012.14765v2 2020-12-30,Non-equilibrium effects on electron-phonon coupling constant in metals,"Understanding of the energy exchange between electrons and phonons in metals is important for micro- and nano-manufacturing and system design. The electron-phonon (e-ph) coupling constant is to describe such exchange strength, yet its variation remains still unclear at micro- and nanoscale where the non-equilibrium effects are significant. In this work, an e-ph coupling model is proposed by transforming the full scattering terms into relaxation time approximation forms in the coupled electron and phonon Boltzmann transport equations. Consequently, the non-equilibrium effects are included in the calculation of e-ph coupling constant. The coupling model is verified by modeling the ultrafast dynamics in femtosecond pump-probe experiments on metal surface, which shows consistent results with the full integral treatment of scattering terms. The e-ph coupling constant is strongly reduced due to both the temporal non-equilibrium between different phonon branches and the spatial non-equilibrium of electrons in confined space. The present work will promote not only a fundamental understanding of the e-ph coupling constant but also the theoretical description of coupled electron and phonon transport at micro- and nanoscale.",2012.15129v1 2017-09-26,Enhancing cavity QED via anti-squeezing: synthetic ultra-strong coupling,"We present and analyze a method where parametric (two-photon) driving of a cavity is used to exponentially enhance the light-matter coupling in a generic cavity QED setup, with time-dependent control. Our method allows one to enhance weak-coupling systems, such that they enter the strong coupling regime (where the coupling exceeds dissipative rates) and even the ultra-strong coupling regime (where the coupling is comparable to the cavity frequency). As an example, we show how the scheme allows one to use a weak-coupling system to adiabatically prepare the highly entangled ground state of the ultra-strong coupling system. The resulting state could be used for remote entanglement applications.",1709.09091v1 2018-03-09,Spin-vorticity coupling in viscous electron fluids,"We consider spin-vorticity coupling - the generation of spin polarization by vorticity - in viscous two-dimensional electron systems with spin-orbit coupling. We first derive hydrodynamic equations for spin and momentum densities in which their mutual coupling is determined by the rotational viscosity. We then calculate the rotational viscosity microscopically in the limits of weak and strong spin-orbit coupling. We provide estimates that show that the spin-orbit coupling achieved in recent experiments is strong enough for the spin-vorticity coupling to be observed. On the one hand, this coupling provides a way to image viscous electron flows by imaging spin densities. On the other hand, we show that the spin polarization generated by spin-vorticity coupling in the hydrodynamic regime can, in principle, be much larger than that generated, e.g. by the spin Hall effect, in the diffusive regime.",1803.03549v1 2018-03-12,The Hagedorn temperature of AdS5/CFT4 at finite coupling via the Quantum Spectral Curve,"Building on the recently established connection between the Hagedorn temperature and integrability [Phys.Rev.Lett. 120 (2018) no.7, 071605], we show how the Quantum Spectral Curve formalism can be used to calculate the Hagedorn temperature of AdS5/CFT4 for any value of the 't Hooft coupling. We solve this finite system of finite-difference equations perturbatively at weak coupling and numerically at finite coupling. We confirm previous results at weak coupling and obtain the previously unknown three-loop Hagedorn temperature. Our finite-coupling results interpolate between weak and strong coupling and allow us to extract the first perturbative order at strong coupling. Our results indicate that the Hagedorn temperature for large 't Hooft coupling approaches that of type IIB string theory in ten-dimensional Minkowski space.",1803.04416v2 2018-03-19,Solving coupled problems of lumped parameter models in a platform for severe accidents in nuclear reactors,"This paper focuses on solving coupled problems of lumped parameter models. Such problems are of interest for the simulation of severe accidents in nuclear reactors~: these coarse-grained models allow for fast calculations for statistical analysis used for risk assessment and solutions of large problems when considering the whole severe accident scenario. However, this modeling approach has several numerical flaws. Besides, in this industrial context, computational efficiency is of great importance leading to various numerical constraints. The objective of this research is to analyze the applicability of explicit coupling strategies to solve such coupled problems and to design implicit coupling schemes allowing stable and accurate computations. The proposed schemes are theoretically analyzed and tested within CEA's procor platform on a problem of heat conduction solved with coupled lumped parameter models and coupled 1D models. Numerical results are discussed and allow us to emphasize the benefits of using the designed coupling schemes instead of the usual explicit coupling schemes.",1803.07016v1 2018-07-18,Coupled-Ring Resonance and Unitary Groups,"The group-theoretic content of photonic coupled microrings resonance phenomena is shown, in particular, an interesting emergence of pseudo-unitary group. The application to the resonance condition in a tri-microring configuration is solved exactly. A practical application of this work will be in the resonance frequency tuning based on the coupling coefficient, in particular, the Mach-Zehnder interferometer approach was analyzed for the coupling modulation.",1807.06773v1 2018-12-19,Logarithmic Stability for Coefficients Inverse Problem of Coupled Schrödinger Equations,"In this paper, we study an inverse coefficients problem for two coupled Schr\""{o}dinger equations with an observation of one component of the solution. The observation is done in a nonempty open subset of the domain where the equations hold. A logarithmic type stability result is obtained. The main method is based on the Carleman estimate for coupled Schr\""{o}dinger equations and coupled heatn equations, and the Fourier-Bros-Iagolnitzer transform.",1812.07820v1 2019-08-05,On the Relationship Between Coupling and Refactoring: An Empirical Viewpoint,"[Background] Refactoring has matured over the past twenty years to become part of a developer's toolkit. However, many fundamental research questions still remain largely unexplored. [Aim] The goal of this paper is to investigate the highest and lowest quartile of refactoring-based data using two coupling metrics - the Coupling between Objects metric and the more recent Conceptual Coupling between Classes metric to answer this question. Can refactoring trends and patterns be identified based on the level of class coupling? [Method] In this paper, we analyze over six thousand refactoring operations drawn from releases of three open-source systems to address one such question. [Results] Results showed no meaningful difference in the types of refactoring applied across either lower or upper quartile of coupling for both metrics; refactorings usually associated with coupling removal were actually more numerous in the lower quartile in some cases. A lack of inheritance-related refactorings across all systems was also noted. [Conclusions] The emerging message (and a perplexing one) is that developers seem to be largely indifferent to classes with high coupling when it comes to refactoring types - they treat classes with relatively low coupling in almost the same way.",1908.01501v1 2019-12-13,A review of Local-to-Nonlocal coupling methods in nonlocal diffusion and nonlocal mechanics,"Local-to-Nonlocal (LtN) coupling refers to a class of methods aimed at combining nonlocal and local modeling descriptions of a given system into a unified coupled representation. This allows to consolidate the accuracy of nonlocal models with the computational expediency of their local counterparts, while often simultaneously removing additional nonlocal modeling issues such as surface effects. The number and variety of proposed LtN coupling approaches have significantly grown in recent year, yet the field of LtN coupling continues to grow and still has open challenges. This review provides an overview of the state-of-the-art of LtN coupling in the context of nonlocal diffusion and nonlocal mechanics, specifically peridynamics. We present a classification of LtN coupling methods and discuss common features and challenges. The goal of this review is not to provide a preferred way to address LtN coupling but to present a broad perspective of the field, which would serve as guidance for practitioners in the selection of appropriate LtN coupling methods based on the characteristics and needs of the problem under consideration.",1912.06668v1 2016-10-20,The convergence problem in mean field games with a local coupling,"The paper studies the convergence, as $N$ tends to infinity, of a system of $N$ coupled Hamilton-Jacobi equations (the Nash system) when the coupling between the players becomes increasingly singular. The limit equation is a mean field game system with local coupling.",1610.06410v2 2017-07-13,Optimal coupling patterns in interconnected communication networks,"Traffic dynamics on single or isolated complex networks has been extensively studied in the past decade. Recently, several coupled network models have been developed to describe the interactions between real-world networked systems. In a system of interconnected networks, the coupling links refer to the physical links between networks and provide paths for traffic transmission. Thus, the coupling pattern, i.e., the way coupling links are added, has a profound influence on the overall traffic performance. In this paper, we employ a simulated annealing (SA) algorithm to find a near-optimal configuration of the coupling links, which effectively improves the overall traffic capacity compared with random, assortative and disassortative couplings. Furthermore, we investigate the optimal configuration of coupling links given by the SA algorithm and develop a faster method to select the coupling links.",1707.03966v2 2017-07-30,Effect of off-diagonal exciton-phonon coupling on intramolecular singlet fission,"Intramolecular singlet fission (iSF) materials provide remarkable advantages in terms of tunable electronic structures, and quantum chemistry studies have indicated strong electronic coupling modulation by high frequency phonon modes. In this work, we formulate a microscopic model of iSF with simultaneous diagonal and off-diagonal coupling to high-frequency modes. A non-perturbative treatment, the Dirac-Frenkel time-dependent variational approach is adopted using the multiple Davydov trial states. It is shown that both diagonal and off-diagonal coupling can aid efficient singlet fission if excitonic coupling is weak, and fission is only facilitated by diagonal coupling if excitonic coupling is strong. In the presence of off-diagonal coupling, it is found that high frequency modes create additional fission channels for rapid iSF. Results presented here may help provide guiding principles for design of efficient singlet fission materials by directly tuning singlet-triplet interstate coupling.",1707.09619v1 2019-05-26,Minimal independent couplings at order $α'^2$,"Using field redefinitions and Bianchi identities on the general form of the effective action for metric, $B$-field and dilaton, we have found that the minimum number of independent couplings at order $\alpha'^2$ is 60. We write these couplings in two different schemes in the string frame. In the first scheme, each coupling does not include terms with more than two derivatives and it does not include structures $R,\,R_{\mu\nu},\,\nabla_\mu H^{\mu\alpha\beta}$, $ \nabla_\mu\nabla^\mu\Phi$. In this scheme, 20 couplings which are the minimum number of couplings for metric and $B$-field, include dilaton trivially as the overall factor of $e^{-2\Phi}$, and all other couplings include derivatives of dilaton. In the second scheme, the dilaton appears in all 60 coupling only as the overall factor of $e^{-2\Phi}$. In this scheme, 20 of the couplings are exactly the same as those in the previous scheme.",1905.10800v1 2020-06-27,Multiple Chaotic Attractors in Coupled Lorenz Systems,"Unidirectionally coupled Lorenz systems in which the drive possesses a chaotic attractor and the response admits two stable equilibria in the absence of the driving is under investigation. It is found that double chaotic attractors coexist in the dynamics. The approach is applicable for chains of coupled Lorenz systems. The existence of four chaotic attractors in three coupled Lorenz systems is also demonstrated.",2006.15364v1 2021-02-01,Minimal gauge invariant couplings at order $\ell_p^6$ in M-theory,"Removing the field redefinitions, the Bianchi identities and the total derivative freedoms from the general form of the gauge invariant couplings at order $\ell_p^6$ for the bosonic fields of M-theory, we have found that the minimum number of independent couplings in the structures with even number of the three-form, is 1062. We find that there are schemes in which there is no coupling involving $R,\,R_{\mu\nu},\,\nabla_\mu F^{\mu\alpha\beta\gamma}$. In these schemes, there are sub-schemes in which, except one coupling which has the second derivative of $F^{(4)}$, the couplings can have no term with more than two derivatives. We find some of the parameters by dimensionally reducing the couplings on a circle and comparing them with the known couplings of the one-loop effective action of type IIA superstring theory. In particular, we find the coupling which has term with more than two derivatives is zero.",2102.00639v2 2021-02-22,Transition in the spectral gap of the massless overlap Dirac operator coupled to abelian fields in three dimensions,"The low lying spectrum of the massless overlap Dirac operator coupled to abelian fields in three dimensions with three different measures are shown to exhibit two phases: a strong coupling gapped phase and a weak coupling gapless phase. The vanishing of the gap from the strong coupling side with a Maxwell and a conformal measure is governed by a Gaussian exponent. Contrary to this result, the vanishing of the gap from the strong coupling side with a compact Thirring measure is not consistent with a Gaussian exponent. The low lying spectrum with a non-compact Thirring measure does not exhibit a simple non-monotonic behavior as a function of the lattice size on the weak coupling side. Our combined analysis suggests exploring the possibility of a strongly coupled continuum theory starting from a compact lattice Thirring model where a compact U(1) gauge field with a single link action is coupled to even number of flavors of massless overlap Dirac fermions.",2102.11367v1 2013-06-12,Contribution of the Electron-Phonon Coupling to the Pairing Interaction in LiFeAs,"The coupling strengths for intra- and inter-band electron-phonon pair scattering are calculated for LiFeAs. While the sum of these couplings, which gives the total electron-phonon coupling $\lambda$, is of order 0.2, we find that their contribution to the presumed $s^\pm$ superconducting state is reduced by approximately an order of magnitude.",1306.2925v1 2013-06-18,The confinement induced resonance in spin-orbit coupled cold atoms with Raman coupling,"We investigate the confinement induced resonance in spin-orbit coupled cold atoms with Raman coupling. We find that the quasi-bound levels induced by the spin-orbit coupling and Raman coupling result in the Feshbach-type resonances. For sufficiently large Raman coupling, the bound states in one dimension exist only for sufficiently strong attractive interaction. Furthermore, the bound states in quasi-one dimension exist only for sufficient large ratio of the length scale of confinement to three dimensional s-wave scattering length. The Raman coupling substantially changes the confinement-induced resonance position. We give a proposal to realize confinement induced resonance by increasing the Raman coupling strength in experiments.",1306.4099v5 2016-09-06,Methods for calculation of the coupling coefficients in the Coupling Cavity Model of arbitrary chain of resonators,"We present the short description of the methods for calculation of the coupling coefficients in the Coupling Cavity Model of arbitrary chain of resonators. In the first part the procedure that is based on the Mode Matching Method is given. Then we present the new method that used only one eigen vector.",1609.01481v1 2018-01-26,Some Spectrum Property of Periodic Coupling AMO Operator,"We study spectrum of the periodic coupling AMO model. Meantime there establish the continuity of Lyapunov exponent about the the periodic coupling of AMO model. Through the dynamical method can find a interval the AMO model only have absolutely continuous spectrum. At the same time, some condition make the periodic coupling of AMO model is singular continuous.",1801.08826v1 2019-06-24,Coupled-wire constructions: a Luttinger liquid approach to topology,"Coupled-wire constructions use bosonization to analytically tackle the strong interactions underlying fractional topological states of matter. We give an introduction to this technique, discuss its strengths and weaknesses, and provide an overview of the main achievements of coupled-wire constructions.",1906.09771v2 2019-07-02,Coupling microwave photons to a mechanical resonator using quantum interference,"In recent years, the field of microwave optomechanics has emerged as leading platform for achieving quantum control of macroscopic mechanical objects. Implementations of microwave optomechanics to date have coupled microwave photons to mechanical resonators using a moving capacitance. While simple and effective, the capacitive scheme suffers from inherent and practical limitations on the maximum achievable coupling strength. Here, we experimentally implement a fundamentally different approach: flux-mediated optomechanical coupling. In this scheme, mechanical displacements modulate the flux in a superconducting quantum interference device (SQUID) that forms the inductor of a microwave resonant circuit. We demonstrate that this flux-mediated coupling can be tuned in-situ by the magnetic flux in the SQUID, enabling nanosecond flux tuning of the optomechanical coupling. Tuning the external in-plane magnetic transduction field, we observe a linear scaling of the single-photon coupling strength, reaching rates comparable to the current state-of-the-art. Finally, this linear scaling is predicted to overcome the limits of single-photon coupling rates in capacitive optomechanics, opening the door for a new generation of groundbreaking optomechanical experiments in the single-photon strong coupling regime.",1907.01418v1 2019-07-25,Unusual Transport Properties with Non-Commutative System-Bath Coupling Operators,"Understanding non-equilibrium heat transport is crucial for controling heat flow in nano-scale systems. We study thermal energy transfer in a generalized non-equilibrium spin-boson model (NESB) with non-commutative system-bath coupling operators and discover unusual transport properties. Compared to the conventional NESB, the heat current is greatly enhanced by rotating the coupling operators. Constructive contribution to thermal rectification can be optimized when two sources of asymmetry, system-bath coupling strength and coupling operators, coexist. At the weak coupling and the adiabatic limit, the scaling dependence of heat current on the coupling strength and the system energy gap changes drastically when the coupling operators become non-commutative. These scaling relations can further be explained analytically by the non-equilibrium polaron-transformed Redfield equation. These novel transport properties, arising from the pure quantum effect of non-commutative coupling operators, should generally appear in other non-equilibrium set-ups and driven-systems.",1907.11262v1 2019-10-25,Electronic structure and transport properties of coupled CdS/ZnSe quantum dots,"Electronic structure and transport characteristics of coupled CdS and ZnSe quantum dots are studied using density functional theory and non equilibrium Greens function method respectively. Our investigations show that in these novel coupled dots, the frontier occupied and unoccupied molecular orbitals are spatially located in two different parts of the coupled dot, thereby indicating the possibility of asymmetry in electronic transport. We have calculated electronic transport through the coupled quantum dot by varying the coupling strength between the individual quantum dots in the limits of weak and strong coupling. Calculations reveal asymmetric current vs voltage curves in both the limits indicating the rectifying properties of the coupled quantum dots. Additionally we discuss the possibility to tune the switching behavior of the coupled dots by different gate geometries.",1910.11813v2 2020-07-27,Enhancement of dynamical robustness in a mean-field coupled network through self-feedback delay,"In this article, we propose a very efficient technique to enhance the dynamical robustness for a network of mean-field coupled oscillators experiencing aging transition. In particular, we present a control mechanism based on delayed negative self-feedback, which can effectively enhance dynamical activities in a mean-field coupled network of active and inactive oscillators. Even for a small value of delay, robustness gets enhanced to a significant level. In our proposed scheme, the enhancing effect is more pronounced for strong coupling. To our surprise even if all the oscillators perturbed to equilibrium mode delayed negative self-feedback able to restore oscillatory activities in the network for strong coupling strength. We demonstrate that our proposed mechanism is independent of coupling topology. For a globally coupled network, we provide numerical and analytical treatment to verify our claim. Also, for global coupling to establish the generality of our scheme, we validate our results for both Stuart-Landau limit cycle oscillators and chaotic Rossler oscillators. To show that our scheme is independent of network topology, we also provide numerical results for the local mean-field coupled complex network.",2007.13405v1 2020-08-26,"Couplings, generalized couplings and uniqueness of invariant measures","We provide sufficient conditions for uniqueness of an invariant probability measure of a Markov kernel in terms of (generalized) couplings. Our main theorem generalizes previous results which require the state space to be Polish. We provide an example showing that uniqueness can fail if the state space is separable and metric (but not Polish) even though a coupling defined via a continuous and positive definite function exists.",2008.11581v1 2021-01-18,Phase and amplitude dynamics of coupled oscillator systems on complex networks,"We investigated the locking behaviors of coupled limit-cycle oscillators with phase and amplitude dynamics. We focused on how the dynamics are affected by inhomogeneous coupling strength and by angular and radial shifts in the coupling function. We performed mean-field analyses of oscillator systems with inhomogeneous coupling strength, testing Gaussian, power-law, and brain-like degree distributions. Even for oscillators with identical intrinsic frequencies and intrinsic amplitudes, we found that the coupling strength distribution and coupling function generated a wide repertoire of phase and amplitude dynamics. These included fully and partially locked states in which high-degree or low-degree nodes would phase-lead the network. The mean-field analytical findings were confirmed via numerical simulations. The results suggest that, in oscillator systems in which individual nodes can independently vary their amplitude over time, qualitatively different dynamics can be produced via shifts in the coupling strength distribution and the coupling form. Of particular relevance to information flows in oscillator networks, changes in the non-specific drive to individual nodes can make high-degree nodes phase-lag or phase-lead the rest of the network.",2101.06913v1 2021-01-27,Microcavity phonon polaritons from weak to ultrastrong phonon-photon coupling,"Strong coupling between molecular vibrations and microcavity modes has been demonstrated to modify physical and chemical properties of the molecular material. Here, we study the much less explored coupling between lattice vibrations (phonons) and microcavity modes. Embedding thin layers of hexagonal boron nitride (hBN) into classical microcavities, we demonstrate the evolution from weak to ultrastrong phonon-photon coupling when the hBN thickness is increased from a few nanometers to a fully filled cavity. Remarkably, strong coupling is achieved for hBN layers as thin as 10 nm. Further, the ultrastrong coupling in fully filled cavities yields a cavity polariton dispersion matching that of phonon polaritons in bulk hBN, highlighting that the maximum light-matter coupling in microcavities is limited to the coupling strength between photons and the bulk material. The tunable cavity phonon polaritons could become a versatile platform for studying how the coupling strength between photons and phonons may modify the properties of polar crystals.",2101.11468v1 2021-05-28,Superfluidity breakdown of Rabi-coupled two-component Bose-Einstein condensates in optical lattices,"We demarcate the unstable regimes of superfluids in a Rabi-coupled two-component Bose-Einstein condensate in the presence of optical lattices. We find that the Rabi coupling can stabilize superfluids. A significant separation between Landau and dynamical instabilities is presented in a Rabi-coupled Zeeman lattice.",2105.13682v1 2021-06-25,A Time-domain Approach to the Design of Coupled-Resonator Microstrip Filters,"Coupled-resonator microstrip filters are among the most versatile filter topologies. A known design approach uses full-wave electromagnetic simulations to determine the coupling coefficient between resonators as a function of their relative position. This could be done using time-domain simulations using a fast Fourier transform (FFT) to extract the couplings from the S parameters obtained from time-domain signals. However, this approach has a poor performance in terms of resolution and specially for weak couplings, leading to unreasonably long simulation times. To overcome this, we introduce a technique to obtain the couplings directly from time signals, without moving to the frequency domain. This procedure works for strong and weak couplings, with much shorter simulation times and a reduced simulation domain over the FFT approach. This technique is used to design coupled resonator filter efficiently from time domain simulations. We implement this procedure using the finite-difference time-domain framework using an open source solver and discuss our implementation. We show that its results are very similar to previously published ones obtained from frequency domain simulations, even in the case of very weak couplings. Finally, we design and measure a filter to show the good performance of the proposed approach.",2106.13737v1 2021-07-09,Effect of Rashba spin-orbit and Rabi couplings on the excitation spectrum of binary Bose-Einstein condensates,"We present the collective excitation spectrum analysis of binary Bose-Einstein condensates (BECs) with spin-orbit (SO) and Rabi couplings in a quasi-two-dimensional system. In particular, we investigate the role of SO and Rabi coupling strengths in determining the dynamical stability of the coupled BECs using Bogoliubov-de Gennes (BdG) theory. Using the eigenergy of BdG spectrum, we confirm the existence of phonon, roton, and maxon modes with weak repulsive intra- and inter-species contact interactions. The depth of the minimum corresponding to the roton mode depends strongly on the coupling strength. We find that the increase of the SO coupling leads to instability, while the increase in the Rabi coupling stabilizes the system. Also the eigenvectors of BdG spectrum indicates the presence of density like mode in the stable regime and spin like modes in unstable regimes. A phase diagram demonstrating the stability regime in the plane of SO and Rabi coupling strengths is obtained. Finally, we complement the observation of the excitation spectrum with the direct numerical simulation results of coupled Gross-Pitaevskii equations.",2107.04237v1 2021-07-21,Coupled embeddability,"We introduce the notion of coupled embeddability, defined for maps on products of topological spaces. We use known results for nonsingular biskew and bilinear maps to generate simple examples and nonexamples of coupled embeddings. We study genericity properties for coupled embeddings of smooth manifolds, extend the Whitney embedding theorems to statements about coupled embeddability, and we discuss a Haefliger-type result for coupled embeddings. We relate the notion of coupled embeddability to the $\mathbb{Z}/2$-coindex of embedding spaces, recently introduced and studied by the authors. With a straightforward generalization of these results, we obtain strong obstructions to the existence of coupled embeddings in terms of the combinatorics of triangulations. In particular, we generalize nonembeddability results for certain simplicial complexes to sharp coupled nonembeddability results for certain pairs of simplicial complexes.",2107.09816v1 2021-10-04,Using C++ to Calculate $\mathsf{SO(10)}$ Tensor Couplings,"\noindent Model building in $\mathsf{SO(10)}$, which is the leading grand unification framework, often involves large Higgs representations and their couplings. Explicit calculations of such couplings is a multi-step process that involves laborious calculations that are time-consuming and error-prone, an issue which only grows as the complexity of the coupling increases. Therefore, there exists an opportunity to leverage the abilities of computer software in order to algorithmically perform these calculations on-demand. This paper outlines the details of such a software, implemented in C++ using in-built libraries. The software is capable of accepting invariant couplings involving an arbitrary number of $\mathsf{SO(10)}$ Higgs tensors, each having up to 5 indices. The output is then produced in \LaTeX, so that it is universally readable and sufficiently expressive. Through the use of this software, $\mathsf{SO(10)}$ coupling analysis can be performed in a way that minimizes calculation time, eliminates errors, and allows for experimentation with couplings that have not been computed before in the literature. Furthermore, this software can be expanded in the future to account for similar Higgs-Spinor coupling analysis, or extended to include further $\mathsf{SO(N)}$ invariant couplings.",2110.01702v1 2021-10-07,Twist-diameter coupling drives DNA twist changes by salt and temperature,"DNA deformations play crucial roles in many biological processes and material applications. During DNA deformation, DNA structural parameters often exhibit non-trivial and counterintuitive couplings, such as the twist-stretch and twist-bending couplings. Here, we reveal an unexpectedly strong negative twist-diameter coupling through the synergy of magnetic-tweezers experiments, atomistic molecular dynamics simulations, and theoretical calculations. In experiments, the DNA twist angle always increases with the concentration of NaCl, KCl, or RbCl. Our simulations quantitatively reproduce salt-induced twist changes and reveal the underlying physical mechanism: the reduction of DNA diameter under a high salt concentration leads to the increase in DNA twist angle through a strong negative twist-diameter coupling. The twist-diameter coupling is mediated by two dihedral angles in DNA structure and the coupling constant is 4.5 kBT/(deg nm) for one base-pair. Based on this coupling constant, we predict the temperature-dependence of DNA twist -0.0102 deg/K per bp, which agrees with our and previous experimental results. Our analysis suggests that the twist-diameter coupling is a common driving force for salt- and temperature-induced DNA twist changes.",2110.03495v1 2022-03-21,Energy analysis of bursting Hindmarsh-Rose neurons with time-delayed coupling,"Mathematical modeling is an important tool to study the role of delay in neural systems and to evaluate its effects on the signaling activity of coupled neurons. Models for delayed neurons are often used to represent the dynamics of real neurons, but rarely to assess the energy required to maintain these dynamics. In this work, we address these questions from an energy perspective by considering a pair of Hindmarsh-Rose burst neurons coupled by reciprocal time-delayed coupling with electrical and chemical synapses. We examine the average energy consumption required to maintain cooperative behavior and quantify the contribution of synapses to total energy consumption. We show that unlike electrical coupling, where the time delay appears to reduce the instantaneous average relative weight of the synaptic contribution, in chemical coupling this average synaptic contribution appears to be much higher in delayed coupling than in instantaneous coupling, except at certain values of coupling strength where the instantaneous synaptic contribution is more important.",2203.11252v1 2022-05-04,Mechanical coupling effects of 2D lattices uncovered by decoupled micropolar elasticity tensor and symmetry operation,"Mechanical couplings such as axial-shear and axial-bending have great potential in the design of active mechanical metamaterials with directional control of input and output loads in sensors and actuators. However, the current ad hoc design of mechanical coupling without theoretical support of elasticity cannot provide design guidelines for mechanical coupling with lattice geometries. Moreover, the correlation between mechanical coupling effects and geometric symmetry is not yet clearly understood. In this work, we systematically search for all possible mechanical couplings in 2D lattice structures by determining the non-zero diagonal terms in the decomposed micropolar elasticity tensor. We also correlate the mechanical couplings with the point-group symmetry of 2D lattices by applying the symmetry operation to the decomposed micropolar elasticity tensor. The decoupled micropolar constitutive equation uncovers eight coupling effects for 2D lattice structures. The symmetry operation of the decoupled micropolar elasticity tensor reveals the correlation of the mechanical coupling with the point groups. Our findings can strengthen the design of mechanical metamaterials with potential applications in areas including sensors, actuators, soft robots, and active metamaterials for elastic/acoustic wave guidance and thermal management.",2205.02062v1 2022-07-07,Mechanical couplings of 3D lattice materials discovered by micropolar elasticity and geometric symmetry,"Similar to Poisson's effect, mechanical coupling is a directional indirect response by a directional input loading. With the advance in manufacturing techniques of 3D complex geometry, architected materials with unit cells of finite volume rather than a point yield more degrees of freedom and foster exotic mechanical couplings such as axial-shear, axial-rotation, axial-bending, and axial-twisting. However, most structural materials have been built by the ad hoc design of mechanical couplings without theoretical support of elasticity, which does not provide general guidelines for mechanical couplings. Moreover, no comprehensive study of all the mechanical couplings of 3D lattices with symmetry operations has been undertaken. Therefore, we construct the decoupled micropolar elasticity tensor of 3D lattices to identify individual mechanical couplings correlated with the point groups. The decoupled micropolar elasticity tensors, classified with 32 point groups, provide 15 mechanical couplings for 3D lattices. Our findings help provide solid theoretical guidelines for the mechanical couplings of 3D structural materials with potential applications in various areas, including active metamaterials, sensors, actuators, elastic waveguides, and acoustics.",2207.03117v2 2022-07-11,Explosive synchronization in coupled nonlinear oscillators on multiplex network,"We report the emergence of explosive synchronization in a multiplex network where oscillators on the first layer are coupled with attractive coupling and those on the second layer, coupled with repulsive coupling. With Stuart-Landau and FitzHugh-Nagumo oscillators as the nodal dynamics, we consider non-local and mean-field intralayer couplings. We establish that explosive synchronization occurs in the multiplex network in the presence of Gaussian noise, and the transition is first order with hysteresis to a state of complete intra-layer and in-phase interlayer synchronization. The width of the hysteresis depends on the range of intralayer attractive coupling, strength of interlayer coupling and noise. We also see how to have control over this induced transition so that the explosive nature, if undesirable, can be converted to continuous type by tuning the strength of repulsive coupling or noise.",2207.04822v2 2022-09-03,Single photon controlled steady state electron transport through a resonance DQD-Cavity system in a strong coupling regime,"We perform theoretical calculations to study steady-state electron transport in a double quantum dot, DQD, coupled to a quantized cavity photon field both in resonance and off-resonance regimes considering weak and strong coupling. In the resonant strong coupling regime, photon exchanges between the energy states of the DQD and the cavity are found reflecting multiple Rabi-resonances. The electron occupation of the states and the transport current can be smoothly increased by tuning the cavity-environment coupling strength. Making the system off-resonant, but still in the strong coupling regime, the photon exchange is diminished and the electron occupation of the system and the transport current through it are prominent for high cavity-environment coupling strength. In the weak coupling regime between the DQD and the cavity, the system has almost the same response in the resonant and the off-resonant regimes at high values of the cavity-environment coupling strength.",2209.01495v1 2022-10-19,Berezinskii-Kosterlitz-Thouless phase transition with Rabi-coupled bosons,"We theoretically investigate the superfluid-normal-state Berezinskii-Kosterlitz-Thouless transition in a binary mixture of bosonic atoms with Rabi coupling under balanced densities. We find the nonmonotonic behavior of the transition temperature with respect to the intercomponent coupling and amplification of the transition temperature for finite values of Rabi coupling, but for small intracomponent couplings. We develop the Nelson-Kosterlitz renormalization-group equations in the two-component Bose mixture and obtain the Nelson-Kosterlitz criterion modified by a fractional parameter, which is responsible for half-integer vortices, and by Rabi coupling. Adopting the renormalization-group approach, we clarify the dependence of the Berezinskii-Kosterlitz-Thouless transition temperature on the Rabi coupling and the intercomponent coupling. Analysis of the first and second sound velocities also reveals the suppression of quasicrossing of the two sound modes with a finite Rabi coupling in the low-temperature regime. Our results for a two-dimensional binary Bose superfluid contribute to the understanding of a broad range of multicomponent quantum systems such as two-dimensional multiband superconductors.",2210.10866v2 2022-11-15,Energy Transport Induced by Transition from Weak to Strong Coupling Regime Between Non-Hermitian systems,"Recently, strong coupling between non-Hermitian physical systems of different nature is widely investigated due to it endows them with new properties. In this work, we investigate the energy transport between strongly coupled systems. We use a partial-secular approach for the description of an open quantum system to investigate the system dynamics during the transition from a weak to a strong coupling regime with an increase of coupling between subsystems. On the example of strongly coupled two-level atoms, we show that near the transition point enhancement of energy transport between the system and reservoirs takes place. This manifests in the fact that energy flow normalized to the coupling constant reaches the maximum both in the cases of zero and non-zero frequency detuning. We show that maximization of normalized energy flow can be used for the determination of the transition to the strong coupling regime in the case of non-zero detuning when there is no clear transition point from the weak to strong coupling regime. The suppression of the energy flow at high relaxation is demonstrated.",2211.08484v1 2022-11-21,Mean-Field Coupled Systems and Self-Consistent Transfer Operators: A Review,"In this review we survey the literature on mean-field coupled maps. We start with the early works from the physics literature, arriving to some recent results from ergodic theory studying the thermodynamic limit of globally coupled maps and the associated self-consistent transfer operators. We also give few pointers to related research fields dealing with mean-field coupled systems in continuous time, and applications.",2211.11245v1 2022-11-28,Forward-backward stochastic differential equations driven by G-Brownian motion under weakly coupling condition,"In this paper, we obtain the existence and uniqueness theorem of $L^{p}$-solution for coupled forward-backward stochastic differential equations driven by G-Brownian motion (G-FBSDEs) with arbitrary $T$ under weakly coupling condition. Specially, the result for $p\in(1,2)$ is completely different from the one for $p\geq2$. Furthermore, by considering the dual linear FBSDE under a suitable reference probability, we establish the comparison theorem for G-FBSDEs under weakly coupling condition.",2211.15041v1 2023-03-10,Dynamic Exchange Coupling between Magnets Mediated by Attenuating Elastic Waves,"Coupling between spatially separated magnets can be mediated by excitations such as photons and phonons, which can be characterized as coherent coupling and dissipative coupling with real and imaginary coupling rate. We theoretically predict the existence of dynamic exchange coupling in a closed magneto-elastic system mediated by attenuating elastic waves and whose coupling rate is complex in general, leading to alternating repulsive or attractive spectrum depending on thickness of the elastic media. The presence of dynamic exchange coupling and its competition with coherent coupling are numerically verified according to the generalized Hooke's law in magneto-elastic systems. The predicted mechanism provides a new strategy to synchronize precessing magnets as well as other excitations over long distance and pave the way for non-Hermitian engineering of collective modes in hybrid magnonics, phononics and photonics.",2303.05778v1 2023-03-20,Meter-scale strong coupling between magnons and photons,"We experimentally realize a meter-scale strong coupling effect between magnons and photons at room temperature, with a coherent coupling of 20 m and a dissipative coupling of 7.6 m. To this end, we integrate a saturable gain into a microwave cavity and then couple this active cavity to a magnon mode via a long coaxial cable. The gain compensates for the cavity dissipation, but preserves the cavity radiation that mediates the indirect photon-magnon coupling. It thus enables the long-range strong photon-magnon coupling. With full access to traveling waves, we demonstrate a remote control of photon-magnon coupling by modulating the phase and amplitude of traveling waves, rather than reconfiguring subsystems themselves. Our method for realizing long-range strong coupling in cavity magnonics provides a general idea for other physical systems. Our experimental achievements may promote the construction of information networks based on cavity magnonics.",2303.10925v3 2023-03-22,Synchronization of Four Non-identical Local Coupled Phase Oscillators in A Ring: Analytic Determination of The Critical Coupling and Phase Differences,"We investigate a system of four nearest neighbour bidirectional coupled phase oscillators of dissimilar initial frequencies in a ring at the changeover into a synchronizing state. There are twenty four permutations upon assigning the initial frequencies to the oscillators. The local interaction between the adjacent coupled phase oscillators introduces details to the synchronization features. Therefore, for the four unalike local coupled oscillators, we classify all possible arrangements into three classes, where each class contains eight configurations. The synchronized state appears at the distinctive coupling when the oscillators transit to synchrony having noticeable characteristics for each class. Also, the unison behaviour emerges when a well-defined phase condition is developed. We utilize this conspicuous phase condition to obtain a mathematical expression predicting the distinguishing coupling for each class once the oscillators have a common frequency. The obtained expression is given in terms of the initial frequencies, at the minute the four local coupled phase oscillators attain the same frequency. The analytic formula of the critical coupling allows us to obtain expressions usable to determine the phase differences at the swop into a synchronization stage.",2303.12591v1 2023-03-31,Self-consistent description of relaxation processes in systems with ultra- and deep-strong coupling,"An ultra-strong coupling regime takes place in a compound system when a coupling strength between the subsystems exceeds one tenth of the system eigenfrequency. It transforms into a deep-strong coupling regime when the coupling strength exceeds the system eigenfrequency. In these regimes, there are difficulties with description of relaxation processes without explicit considering of environment degrees of freedom. To correctly evaluate the relaxation rates, it is necessary to consider the interaction of the system with its environment taking into account the counter-rotating wave and diamagnetic terms. We develop a self-consistent theory for calculation of the relaxation rates in the systems, in which the coupling strength is of the order of the system eigenfrequency. We demonstrate that the increase in the coupling strength can lead to a significant decrease in the relaxation rates. In particular, we show that for frequency-independent density of states of the environment, the relaxation rates decrease exponentially with the increase in the coupling strength. This fact can be used to suppress losses by tuning the strength coupling and the environment states.",2303.18159v1 2023-04-24,Birth and death of entanglement between two accelerating Unruh-DeWitt detectors coupled with a scalar field,"We consider two accelerating Unruh-DeWitt detectors coupled linearly or quadratically with a scalar field. We show that entanglement can be created by acceleration, and is divergent only when the two detectors coincide. For linear coupling, entanglment decreases monotonically with the increase of acceleration. For quadratic coupling, entanglement behaves non-monotonically.",2304.12126v1 2023-05-11,Photo-induced Non-collinear Interlayer RKKY Coupling in Bulk Rashba Semiconductors,"The interplay between light-matter, spin-orbit, and magnetic interactions allows the investigation of light-induced magnetic phenomena that is otherwise absent without irradiation. We present our analysis of light-driving effects on the interlayer exchange coupling mediated by a bulk Rashba semiconductor in a magnetic multilayer. The collinear magnetic exchange coupling mediated by the photon-dressed spin-orbit coupled electrons of BiTeI develops light-induced oscillation periods and displays new decay powers laws, both of which are enhanced with an increasing light-matter coupling. For magnetic layers with non-collinear magnetization, we find a non-collinear magnetic exchange coupling uniquely generated by light-driving of the multilayer. As the non-collinear magnetic exchange coupling mediated by the electrons of BiTeI is unique to the irradiated system and it is enhanced with increasing light-matter coupling, this effect offers a promising platform of investigation of light-driving effects on magnetic phenomena in spin-orbit coupled systems.",2305.06861v1 2023-05-27,Hopf bifurcation and periodic solutions in a coupled Brusselator model of chemical reactions,"In this paper, we consider a coupled Brusselator model of chemical reactions, for which no symmetry for the coupling matrices is assumed. We show that the model can undergoes a Hopf bifurcation, and consequently periodic solutions can arise when the dispersal rates are large. Moreover, the effect of the coupling matrices on the Hopf bifurcation value is considered for a special case.",2305.17363v1 2023-06-27,Electro-momentum coupling tailored in piezoelectric metamaterials with resonant shunts,"Local microstructural heterogeneities of elastic metamaterials give rise to non-local macroscopic cross-coupling between stress-strain and momentum-velocity, known as Willis coupling. Recent advances have revealed that symmetry breaking in piezoelectric metamaterials introduces an additional macroscopic cross-coupling effect, termed electromomentum coupling, linking electrical stimulus and momentum and enabling the emergence of exotic wave phenomena characteristic of Willis materials. The electro-momentum coupling provides an extra degree of freedom for controlling elastic wave propagation in piezoelectric composites through external electrical stimuli. In this study, we present how to tune the electro-momentum coupling arising in 1-D periodic piezoelectric metamaterials with broken inversion symmetry through shunting the inherent capacitance of the individual piezoelectric layers with a resistor and inductor in series forming an RLC (resistor-inductor-capacitor) circuit. Guided by the effective elastodynamic theory and homogenization method for piezoelectric metamaterials, we derived a closed-form expression of the electro-momentum coupling in shunted piezoelectric metamaterials. Moreover, we demonstrate the ability to tailor the electro-momentum coupling coefficient and control the amplitudes and phases of the forward and backward propagating waves, yielding tunable asymmetric wave responses. The results of our study hold promising implications for applications involving nonreciprocal wave phenomena and programmable metamaterials.",2306.15608v1 2023-06-29,Global synchronization analysis of non-diffusively coupled networks through Contraction Theory,"Synchronization of coupled dynamical systems is a widespread phenomenon in both biological and engineered networks, and understanding this behavior is crucial for controlling such systems. Considerable research has been dedicated to identifying the conditions that promote synchronization in diffusively coupled systems, where coupling relies on the difference between the states of neighboring systems and vanishes on the synchronization manifold. In particular, contraction theory provides an elegant method for analyzing synchronization patterns in diffusively coupled networks. However, these approaches do not fully explain the emergence of synchronization behavior in non-diffusively coupled networks where the coupling does not vanish on the synchronization manifold and hence the dynamics on the synchronization manifold differ from the uncoupled systems. Inspired by neuronal networks connected via non-diffusive chemical synapses, we extend contraction theory to establish sufficient conditions for global synchronization in general non-diffusively coupled nonlinear networks. We demonstrate the theoretical results on a network of Hindmarsh-Rose oscillators connected via chemical synapses and networks of FitzHugh-Nagumo oscillators connected via chemical synapses and additive coupling.",2307.00030v1 2023-07-09,Multi-spin probes for thermometry in the strong-coupling regime,"We study the sensitivity of thermometric probes that are composed of $N$ spins coupled to a sample prepared at temperature $T$. Our analysis extends beyond the weak-coupling limit into the strong sample-probe coupling regime. In particular, sample-induced interactions between each of the spins are generated via strong coupling effects and are not fine-tuned amongst each body composing the probe. By employing the reaction-coordinate mapping to evaluate the non-canonical equilibrium state of the probe at finite coupling, we compute the thermometric sensitivity via the quantum Fisher information through the equilibrium state itself. We find that for single-spin probes $(N = 1)$, temperature sensitivity decreases in the regime of weak-to-intermediate coupling strength, however, as the coupling increases we observe much higher sensitivity of the probe in the low-temperature regime. Furthermore, as long as $N > 1$, there exist optimal values of the sample-probe interaction energy that allow one to attain enhanced thermometric sensitivity when compared to the maximum achieved precision obtained from thermal Gibbs states at weak coupling, particularly in the regime of low temperature. Finally, we show that this enhanced sensitivity may be observed from suboptimal measurements.",2307.04232v2 2023-07-11,Inflationary magnetogenesis with a self-consistent coupling function,"In this paper, we discuss the inflationary magnetogenesis scenario, in which the coupling function is introduced to break the conformal invariance of electromagnetic action. Unlike in conventional models, we deduce the Maxwell's equations under the perturbed FRW metric. We found that, the self-consistency of the action depends on the form of the coupling function when the scalar mode perturbations have been considered. Therefore, this self-consistency can be seen as a restriction on the coupling function. In this paper, we give the restrictive equation for coupling function then obtain the specific form of the coupling function in a simple model. We found that the coupling function depends on the potential of the inflaton and thus is model dependent. We obtain the power spectrum of electric field and magnetic field in large-field inflation model. We also found that the coupling function is a incresing function of time during slow-roll era as most of inflationary magnetogenesis models, it will lead to strong coupling problem. This issue is discussed qualitatively by introducing a correction function during the preheating.",2307.04987v1 2023-09-27,Multiband strong-coupling superconductors with spontaneously broken time-reversal symmetry,"We study superconducting three-band systems within strong-coupling Eliashberg theory. In particular, we search for phase-frustrated superconducting systems with spontaneous time-reversal symmetry breaking (TRSB) states. The emergence of TRSB states in multiband systems has so far been studied using microscopic weak-coupling BCS theory or more phenomenological effective field theories such as multi-component Ginzburg-Landau theories. For systems with three disjoint Fermi surfaces whose electrons experience interactions mediated by phonons, we present a microscopic analysis showing that TRSB states also exist within a strong-coupling microscopic theory. The systems we consider have sizable electron-phonon couplings, putting them into the strong-coupling regime. They are thus a fitting description for strong-coupling materials such as some of the iron pnictides. Moreover, as the TRSB states are challenging to find numerically, we calculate the free energy of multiband systems within strong-coupling theory and make explicit use of it to pin down the TRSB states' elusive nature. Since Eliashberg theory is well incorporated with first-principles calculations, our strong-coupling approach might help facilitate a more efficient search for candidate materials that can exhibit TRSB.",2309.15894v2 2023-09-29,Constructing Maximal Germ Couplings of Brownian Motions with Drift,"Consider all the possible ways of coupling together two Brownian motions with the same starting position but with different drifts onto the same probability space. It is known that there exist couplings which make these processes agree for some random, positive, maximal initial length of time. Presently, we provide an explicit, elementary construction of such couplings.",2309.16922v1 2023-10-04,Coupling strength induced BCS-BEC crossover on phase boundary of pion superfluid,"Coupling strength effect on the quark matter with finite isospin chemical potential is studied in a Pauli-Villars regularized NJL model. A BCS-BEC crossover occurs along the phase boundary of pion superfluid phase transition, as increasing coupling strength $G$. For strong coupling cases, the critical isospin chemical potential for pion superfluid phase transition $\mu_I^c$ is exactly the same as pion mass in vacuum $M_\pi$. Around the critical point $\mu_I^c$, the pion superfluid quark matter is in BEC state, associated with a fast increase of pion condensate. For weak coupling cases, we obtain $\mu_I^c0 is considered for the initial perturbation theory approximations up to four loop order. The finiteness of the analytic coupling at zero is shown to be a consequence of the asymptotic freedom property of the initial theory. The nonperturbative contributions to the analytic coupling are extracted explicitly. For all Q>Lambda they are represented in the form of an expansion in inverse powers of Euclidean momentum squared. The effective method for a precise calculation of the analytic running coupling is developed on the basis of the stated expansion. The energy scale evolution of the analytic running coupling for the one- to four-loop cases is studied and the higher loop stability and low dependence on the quark threshold matching conditions in comparison with the perturbative running coupling were found. Normalizing the analytic running coupling at the scale of the rest mass of the Z boson with the world average value of the strong coupling constant, alpha_{an}(M_Z^2)=0.1181^{+0.002}_{-0.002}, one obtains as a result of the energy scale evolution of the analytic running coupling alpha_{an}(M_tau^2)= 0.2943^{+0.0111}_{-0.0106} that is notably lower than the estimations of the coupling strength available at the scale of the mass of the tau lepton.",0211339v1 2002-12-20,Quantum Information Processing by NMR using strongly coupled spins,"The enormous theoretical potential of Quantum Information Processing (QIP) is driving the pursuit for its practical realization by various physical techniques. Currently Nuclear Magnetic Resonance (NMR) has been the forerunner by demonstrating a majority of quantum algorithms. In NMR, spin systems consisting of coupled nuclear spins are utilized as qubits. In order to carry out QIP, a spin system has to meet two major requirements: (i) qubit addressability and (ii) mutual coupling among the qubits. It has been demonstrated that the magnitude of the mutual coupling among qubits can be increased by orienting the spin-systems in a liquid crystal matrix and utilizing the residual dipolar couplings. While utilizing residual dipolar couplings may be useful to increase the number of qubits, nuclei of same species (homonuclei) might become strongly coupled. In strongly coupled spin-systems, spins loose their individual identity of being qubits. We propose that even such strongly coupled spin-systems can be used for QIP and the qubit-manipulation can be achieved by transition-selective pulses. We demonstrate experimental preparation of pseudopure states, creation of maximally entangled states, implementation logic gates and implementation of Deutsch-Jozsa (DJ) algorithm in strongly coupled 2,3 and 4 spin systems. The energy levels of the strongly coupled 3 and 4 spin systems were obtained by using a Z-COSY experiment.",0212123v2 2007-12-18,Threshold and Flavour Effects in the Renormalization Group Equations of the MSSM I: Dimensionless Couplings,"In a theory with broken supersymmetry, gaugino couplings renormalize differently from gauge couplings, as do higgsino couplings from Higgs boson couplings. As a result, we expect the gauge (Higgs boson) couplings and the corresponding gaugino (higgsino) couplings to evolve to different values under renormalization group evolution. We re-examine the renormalization group equations (RGEs) for these couplings in the Minimal Supersymmetric Standard Model (MSSM). To include threshold effects, we calculate the $\beta$-functions using a sequence of (non-supersymmetric) effective theories with heavy particles decoupled at the scale of their mass. We find that the difference between the SM couplings and their SUSY cousins that is ignored in the literature may be larger than two-loop effects which are included, and further that renormalization group evolution induces a non-trivial flavour structure in gaugino interactions. We present here the coupled set of RGEs for these dimensionless gauge and ""Yukawa""-type couplings. The RGEs for the dimensionful SSB parameters of the MSSM will be presented in a companion paper.",0712.2858v2 2009-10-12,Effects on the two-point correlation function from the coupling of quintessence to dark matter,"We investigate the effects of the nonminimal coupling between the scalar field dark energy (quintessence) and the dark matter on the two- point correlation function. It is well known that this coupling shifts the turnover scale as well as suppresses the amplitude of the matter power spectrum. However, these effects are too small to be observed when we limit the coupling strength to be consistent with observations. Since the coupling of quintessence to baryons is strongly constrained, species dependent coupling may arise. This results in a baryon bias that is dif- ferent from unity. Thus, we look over the correlation function in this coupled model. We find that even the non-coupled quintessence model gives the better fit to the correlation function compared to the cosmo- logical constant model. We are also able to observe the enhancement of the baryon acoustic oscillation (BAO) peak due to the increasing bias factor of baryon from this species dependent coupling. In order to avoid the damping effect of the BAO signature in the matter power spectrum due to nonlinear clustering, we consider the coupling effect on the BAO bump in the linear regime. This provides an alternative method to constrain the coupling of dark energy to dark matter.",0910.2175v2 2010-08-11,Interacting fermions on the honeycomb bilayer: from weak to strong coupling,"Many-body instabilities of the half-filled honeycomb bilayer are studied using weak coupling renormalization group as well as strong coupling expansion. For spinless fermions and assuming parabolic degeneracy, there are 4-independent four-fermion contact couplings. While the dominant instability depends on the microscopic values of the couplings, the broken symmetry state is typically a gapped insulator with either broken inversion symmetry or broken time reversal symmetry, with a quantized anomalous Hall effect. Under certain conditions, the dominant instability may appear in the particle-particle (pairing) channel. For some non-generic fine-tuned initial conditions, weak coupling RG trajectories flow into the non-interacting fixed point, although generally we find runaway flows which we associate with ordering tendencies. Additionally, a tight binding model with nearest neighbor hopping and nearest neighbor repulsion is studied in weak and strong couplings and in each regime a gapped phase with inversion symmetry breaking is found. In the strong coupling limit, the ground state wavefunction is constructed for vanishing in-plane hopping but finite inter-plane hopping, which explicitly displays the broken inversion symmetry and a finite difference between the number of particles on the two layers. Finally, we discuss the spin-1/2 case and use Fierz identities to show that the number of independent 4-fermion contact couplings is 9. The corresponding RG equations in the spin-1/2 case are also presented, and used to show that, just as in strong coupling, the most dominant weak coupling instability of the repulsive Hubbard model (at half-filling) is an anti-ferromagnet.",1008.1901v1 2011-05-24,Chaotic inflation in modified gravitational theories,"We study chaotic inflation in the context of modified gravitational theories. Our analysis covers models based on (i) a field coupling $\omega(\phi)$ with the kinetic energy $X$ and a nonmimimal coupling $\zeta \phi^{2} R/2$ with a Ricci scalar $R$, (ii) Brans-Dicke (BD) theories, (iii) Gauss-Bonnet (GB) gravity, and (iv) gravity with a Galileon correction. Dilatonic coupling with the kinetic energy and/or negative nonminimal coupling are shown to lead to compatibility with observations of the Cosmic Microwave Background (CMB) temperature anisotropies for the self-coupling inflaton potential $V(\phi)=\lambda \phi^{4}/4$. BD theory with a quadratic inflaton potential, which covers Starobinsky's $f(R)$ model $f(R)=R+R^{2}/(6M^{2})$ with the BD parameter $\omega_{BD}=0$, gives rise to a smaller tensor-to-scalar ratio for decreasing $\omega_{BD}$. In the presence of a GB term coupled to the field $\phi$, we express the scalar/tensor spectral indices $n_{s}$ and $n_{t}$ as well as the tensor-to-scalar ratio $r$ in terms of two slow-roll parameters and place bounds on the strength of the GB coupling from the joint data analysis of WMAP 7yr combined with other observations. We also study the Galileon-like self-interaction $\Phi(\phi) X \square\phi$ with exponential coupling $\Phi(\phi) \propto e^{\mu\phi}$. Using a CMB likelihood analysis we put bounds on the strength of the Galileon coupling and show that the self coupling potential can in fact be made compatible with observations in the presence of the exponential coupling with $\mu>0$.",1105.4685v1 2013-07-26,A comparison of structure formation in minimally and non-minimally coupled quintessence models,"We study structure formation in non-minimally coupled dark energy models, where there is a coupling in the Lagrangian between a quintessence scalar field and gravity via the Ricci scalar. We consider models with a range of different non-minimal coupling strengths and compare these to minimally coupled quintessence models with time-dependent dark energy densities. The equations of state of the latter are tuned to either reproduce the equation of state of the non-minimally coupled models or their background history. Thereby they provide a reference to study the unique imprints of coupling on structure formation. We show that the coupling between gravity and the scalar field, which effectively results in a time-varying gravitational constant G, is not negligible and its effect can be distinguished from a minimally coupled model. We extend previous work on this subject by showing that major differences appear in the determination of the mass function at high masses, where we observe differences of the order of 40% at z=0. Our new results concern effects on the non-linear matter power spectrum and on the lensing signal (differences of ~10% for both quantities), where we find that non-minimally coupled models could be distinguished from minimally coupled ones.",1307.7026v2 2013-10-21,"Towards a Mechanism of Rattler Coupling in the β-Pyrochlores AOs2O6 (A = K, Rb, Cs)","We have applied ab initio molecular dynamics (MD) simulations to study metal-metal coupling on the alkali-metal sublattice in the {\beta}-pyrochlore osmates, AOs2O6 (A = K, Rb, Cs) at 300 K. We find that the alkali-metal atoms (rattlers) couple to each other more strongly than they couple to the cage atoms, and that, at 300 K, this coupling is strongest for Cs. We show that this coupling controls the dominant dynamics in the rattling of these atoms. We provide preliminary evidence that the rattlers couple to each other primarily through the T2g mode whereas their coupling to the cage modes occurs through the T1u mode. Rattler coupling through the T2g mode provides insight into the trend in spectral broadening from Cs to K. The spectral broadening is inversely proportional to the strength of the dynamical correlations on the alkali-metal sublattice which in turn depend on the atomic size of the rattler, decreasing from Cs to K. Thus, the broadest spectrum exhibited by the K is partly a consequence of the small size of this rattler which permits a greater range of motions involving combinations of both correlated and anti-correlated dynamics. We emphasize that the identification of the somewhat distinct roles of the T1u and T2g modes in rattler coupling reported in this work is a significant step towards a complete fundamental mechanism of rattler dynamical coupling in these osmates. We believe that such a mechanism will have profound implications for a broad class of cage compounds, including clathrates and skutterudites.",1310.5416v2 2014-04-23,Renormalizability of the Dirac Equation in Torsion-Gravity with Non-Minimal Coupling,"We will consider the torsional completion of gravity for a background filled with Dirac matter fields, studying what happens when fermionic non-minimal coupling is taken into account: we will show that, although non-minimal couplings are usually disregarded because of their ill-defined behaviour in ultraviolet regimes, this is due to the fact that torsion is commonly neglected, whereas when torsion is not left aside, even non-minimal couplings behave properly. In detail, we will see that non-minimal coupling allows to renormalize the Dirac equation even when torsion is taken into consideration and that in some type of non-minimally coupled models parity-oddness might be present even in the gravitational sector. In addition, we will show that in the presence of the considered non-minimal coupling, torsion is able to evade cosmological singularities as it can happen in the minimal coupling case and in some other non--minimally coupled theory. In the course of the paper, we shall consider a specific interaction as prototype to study this fermionic non-minimal coupling, but we will try to present results that do not depend on the actual structure of the non-minimal couplings by investigating alternative types of interaction.",1404.5784v4 2014-08-07,On couplings to matter in massive (bi-)gravity,"We investigate the coupling to matter in ghost-free massive (bi-)gravity. When species in the matter sector couple covariantly to only one metric, we show that at one--loop these couplings do not spoil the special structure of the graviton potential. When the same species couples directly to both metrics we show that a ghost is present at the classical level and that loops destroy the special structure of the potential at an unacceptably low scale. We then propose a new `composite' effective metric built out of both metrics. When matter fields couple covariantly to this effective metric, the would be Boulware--Deser ghost is absent in different representative limits. At one--loop such couplings do not detune the special structure of the potential. We conjecture that matter can couple covariantly to that effective metric in all generality without introducing any Boulware--Deser ghost below a cut-off scale parametrically larger than the strong coupling scale. We also discuss alternative couplings to matter where the kinetic and potential terms of the matter field couple to different metrics. In both cases we discuss preliminary implications for cosmology.",1408.1678v3 2014-12-08,Rigidity for Markovian Maximal Couplings of Elliptic Diffusions,"Maximal couplings are (probabilistic) couplings of Markov processes such that the tail probabilities of the coupling time attain the total variation lower bound (Aldous bound) uniformly for all time. Markovian (or immersion) couplings are couplings defined by strategies where neither process is allowed to look into the future of the other before making the next transition. Markovian couplings are typically easier to construct and analyze than general couplings, and play an important role in many branches of probability and analysis. Hsu and Sturm (2013) proved that the reflection-coupling of Brownian motion is the unique Markovian maximal coupling (MMC) of Brownian motions starting from two different points. Later, Kuwada (2009) proved that the existence of a MMC for Brownian motions on a Riemannian manifold enforces existence of a reflection structure on the manifold. In this work, we investigate suitably regular elliptic diffusions on manifolds, and show how consideration of the diffusion geometry (including dimension of the isometry group and flows of isometries) is fundamental in classification of the space and the generator of the diffusion for which an MMC exists, especially when the MMC also holds under local perturbations of the starting points for the coupled diffusions. We also describe such diffusions in terms of Killing vectorfields (generators of isometry groups) and dilation vectorfields (generators of scaling symmetry groups).",1412.2647v2 2017-08-09,Two-way coupling of magnetohydrodynamic simulations with embedded particle-in-cell simulations,"We describe a method for coupling an embedded domain in a magnetohydrodynamic (MHD) simulation with a particle-in-cell (PIC) method. In this two-way coupling we follow the work of Daldorff et al. in which the PIC domain receives its initial and boundary conditions from MHD variables (MHD to PIC coupling) while the MHD simulation is updated based on the PIC variables (PIC to MHD coupling). This method can be useful for simulating large plasma systems, where kinetic effects captured by particle-in-cell simulations are localized but affect global dynamics. We describe the numerical implementation of this coupling, its time-stepping algorithm, and its parallelization strategy, emphasizing the novel aspects of it. We test the stability and energy/momentum conservation of this method by simulating a steady-state plasma. We test the dynamics of this coupling by propagating plasma waves through the embedded PIC domain. Coupling with MHD shows satisfactory results for the fast magnetosonic wave, but significant distortion for the circularly polarized Alfv\'en wave. Coupling with Hall-MHD shows excellent coupling for the whistler wave. We also apply this methodology to simulate a Geospace Environmental Modeling (GEM) challenge type of reconnection with the diffusion region simulated by PIC coupled to larger scales with MHD and Hall-MHD. In both these cases we see the expected signatures of kinetic reconnection in the PIC domain, implying that this method can be used for reconnection studies.",1708.02877v1 2018-04-04,Use of the geometric mean as a statistic for the scale of the coupled Gaussian distributions,"The geometric mean is shown to be an appropriate statistic for the scale of a heavy-tailed coupled Gaussian distribution or equivalently the Student's t distribution. The coupled Gaussian is a member of a family of distributions parameterized by the nonlinear statistical coupling which is the reciprocal of the degree of freedom and is proportional to fluctuations in the inverse scale of the Gaussian. Existing estimators of the scale of the coupled Gaussian have relied on estimates of the full distribution, and they suffer from problems related to outliers in heavy-tailed distributions. In this paper, the scale of a coupled Gaussian is proven to be equal to the product of the generalized mean and the square root of the coupling. From our numerical computations of the scales of coupled Gaussians using the generalized mean of random samples, it is indicated that only samples from a Cauchy distribution (with coupling parameter one) form an unbiased estimate with diminishing variance for large samples. Nevertheless, we also prove that the scale is a function of the geometric mean, the coupling term and a harmonic number. Numerical experiments show that this estimator is unbiased with diminishing variance for large samples for a broad range of coupling values.",1804.03989v2 2019-04-01,Spin-charge coupled transport in van der Waals systems with random tunneling,"We study the electron and spin transport in a van der Waals system formed by one layer with strong spin-orbit coupling and a second layer without spin-orbit coupling, in the regime when the interlayer tunneling is random. We find that in the layer without intrinsic spin-orbit coupling spin-charge coupled transport can be induced by two distinct mechanisms. First, the gapless diffusion modes of the two isolated layers hybridize in the presence of tunneling, which constitutes a source of spin-charge coupled transport in the second layer. Second, the random tunneling introduces spin-orbit coupling in the effective disorder-averaged single-particle Hamiltonian of the second layer. This results in non-trivial spin transport and, for sufficiently strong tunneling, in spin-charge coupling. As an example, we consider a van der Waals system formed by a two-dimensional electron gas (2DEG)--such as graphene--and the surface of a topological insulator (TI) and show that the proximity of the TI induces a coupling of the spin and charge transport in the 2DEG. In addition, we show that such coupling can be tuned by varying the doping of the TI's surface. We then obtain, for a simple geometry, the current-induced non-equilibrium spin accumulation (Edelstein effect) caused in the 2DEG by the coupling of charge and spin transport.",1904.01015v1 2019-03-27,A coupled finite-volume solver for numerical simulation of electrically-driven flows,"The accuracy and stability of implicit CFD codes are frequently impaired by the decoupling between variables, which can ultimately lead to numerical divergence. Coupled solvers, which solve all the governing equations simultaneously, have the potential to fix this problem. In this work, we report the implementation of coupled solvers for transient and steady-state electrically-driven flow simulations in the finite-volumes framework. The numerical method, developed in OpenFOAM, is generic for Newtonian and viscoelastic fluids and is formulated for the Poisson-Nernst-Planck and Poisson-Boltzmann models. The resulting coupled systems of equations are solved efficiently with PETSc library. The performance of the coupled solvers is assessed in two test cases: induced-charge electroosmosis of a Newtonian fluid around a cylinder; electroosmotic flow of a PTT viscoelastic fluid in a contraction/expansion microchannel. The coupled solvers are more accurate in transient simulations and allow the use of larger time-steps without numerical divergence. For steady-state simulations, the coupled solvers converge in fewer iterations than segregated solvers. Although coupled solvers are much slower in a per time-step basis, the overall speedup factor obtained in this study reached a maximum value of ~100, where the highest factors have been obtained with semi-coupled solvers, which drop some coupling terms between equations. While further research is needed to improve the efficiency of the matrix solving stage, coupled solvers are already superior to segregated solvers in a number of cases.",1904.02138v2 2019-04-23,Soft-gluon effective coupling and cusp anomalous dimension,"We consider the extension of the CMW soft-gluon effective coupling in the context of soft-gluon resummation for QCD hard-scattering observables beyond the next-to-leading logarithmic accuracy. We present two proposals of a soft-gluon effective coupling that extend the CMW coupling to all perturbative orders in the \ms\ coupling $\as$. Although both effective couplings are well-defined in the physical four-dimensional space time, we examine their behaviour in $d=4 -2\ep$ space time dimensions. We uncover an all-order perturbative relation with the cusp anomalous dimension: the (four dimensional) cusp anomalous dimension is equal to the $d$-dimensional soft-gluon effective coupling at the conformal point $\ep=\beta(\as)$, where the $d$-dimensional QCD $\beta$-function, $\beta(\as) - \ep$, vanishes. We present the explicit expressions of the two soft-gluon couplings up to ${\cal O}(\as^2)$ in $d$ dimensions. In the four-dimensional case we compute the two soft couplings up to ${\cal O}(\as^3)$. For one of the two couplings, we confirm the ${\cal O}(\as^3)$ result previously presented by other authors. For the other coupling, we obtain the explicit relation with the cusp anomalous dimension up to ${\cal O}(\as^4)$. We comment on Casimir scaling at ${\cal O}(\as^4)$.",1904.10365v1 2020-05-11,Analysis of the Hopfield Model with Discrete Coupling,"Growing demand for high-speed Ising-computing-specific hardware has prompted a need for determining how the accuracy depends on a hardware implementation with physically limited resources. For instance, in digital hardware such as field-programmable gate arrays, as the number of bits representing the coupling strength is reduced, the density of integrated Ising spins and the speed of computing can be increased while the calculation accuracy becomes lower. To optimize the accuracy-efficiency trade-off, we have to estimate the change in performance of the Ising computing machine depending on the number of bits representing the coupling strength. In this study, we tackle this issue by focusing on the Hopfield model with discrete coupling. The Hopfield model is a canonical Ising computing model. Previous studies have analyzed the effect of a few nonlinear functions (e.g. sign) for mapping the coupling strength on the Hopfield model with statistical mechanics methods, but not the effect of discretization of the coupling strength in detail. Here, we derived the order parameter equations of the Hopfield model with discrete coupling by using the replica method and clarified the relationship between the number of bits representing the coupling strength and the critical memory capacity. In this paper, we used the replica method for the Hopfield model with general nonlinear coupling (Sompolinsky (1986)) to analyze the model with a multi-bit discrete coupling strength, and we novelly derived the de Almeida-Thouless line of the model with general nonlinear coupling.",2005.05174v4 2020-08-23,Dynamics of coupled thermoacoustic oscillators under asymmetric forcing: Experiments and theoretical modeling,"Quenching of limit cycle oscillations (LCO), either through mutual coupling or external forcing, has attracted wide attention in several fields of science and engineering. However, the simultaneous utilization of these coupling schemes in quenching of LCO has rarely been studied despite its practical applicability. We study the dynamics of two thermoacoustic oscillators simultaneously subjected to mutual coupling and asymmetric external forcing through experiments and theoretical modeling. We investigate the forced response of both identical and non-identical thermoacoustic oscillators for two different amplitudes of LCO. Under mutual coupling alone, identical thermoacoustic oscillators display the occurrence of partial amplitude death and amplitude death, whereas under forcing alone, asynchronous quenching of LCO is observed at non-resonant conditions. When the oscillators are simultaneously subjected to mutual coupling and asymmetric forcing, we observe a larger parametric region of oscillation quenching than when the two mechanisms are utilized individually. This enhancement in the region of oscillation quenching is due to the complementary effect of amplitude death and asynchronous quenching. However, a forced response of coupled non-identical oscillators shows that the effect of forcing is insignificant on synchronization and quenching of oscillations in the oscillator which is not directly forced. Finally, we qualitatively capture the experimental results using a reduced-order theoretical model of two coupled Rijke tubes which are coupled through dissipative and time-delay coupling and asymmetrically forced. We believe that these findings offer fresh insights into the combined effects of mutual and forced synchronization in a system of coupled nonlinear oscillators.",2008.09999v3 2022-11-18,Coupled cluster theory: Towards an algebraic geometry formulation,"Coupled cluster theory produced arguably the most widely used high-accuracy computational quantum chemistry methods. Despite the approach's overall great computational success, its mathematical understanding is so far limited to results within the realm of functional analysis. The coupled cluster amplitudes, which are the targeted objects in coupled cluster theory, correspond to solutions to the coupled cluster equations, which is a system of polynomial equations of at most degree four. The high dimensionality of the electronic Schr\""odinger equation and the non-linearity of the coupled cluster ansatz have so far stalled a formal analysis of this polynomial system. In this article, we present algebraic investigations that shed light on the coupled cluster equations and the root structure of this ansatz. This is of importance for the a posteriori evaluation of coupled cluster calculations. To that end, we investigate the root structure by means of Newton polytopes. We derive a general v-description, which is subsequently turned into an h-description for explicit examples. This perspective reveals an apparent connection between Pauli's exclusion principle and the geometrical structure of the Newton polytopes. We also propose an alternative characterization of the coupled cluster equations projected onto singles and doubles as cubic polynomials on an algebraic variety with certain sparsity patterns. Moreover, we provide numerical simulations of two computationally tractable systems, namely, the two electrons in four spin-orbitals system and the three electrons in six spin-orbitals system. These simulations provide novel insight into the root structure of the coupled cluster solutions when the coupled cluster ansatz is truncated.",2211.10389v3 2023-03-26,Giant-atom entanglement in waveguide-QED systems including non-Markovian effect,"We study the generation of quantum entanglement between two giant atoms coupled to a common one-dimensional waveguide. Here each giant atom interacts with the waveguide at two separate coupling points. Within the Wigner-Weisskopf framework for single coupling points, we obtain the time-delayed quantum master equations governing the evolution of the two giant atoms for three different coupling configurations: separated, braided, and nested couplings. For each coupling configuration, we consider both the Markovian and non-Markovian entanglement dynamics of the giant atoms, which are initially in two different separable states: single- and double-excitation states. Our results show that the generated entanglement depends on the phase shift, time delay, atomic initial state, and the coupling configuration. For the single-excitation initial state, there exists the steady-state entanglement for each coupling in both the Markovian and non-Markovian regimes due to the appearance of the dark state. For the double-excitation initial state, we observe entanglement sudden birth via adjusting the phase shift in both regimes. In particular, the maximally achievable entanglement for the nested coupling is about one order of magnitude larger than those of separate and braided couplings. We also find that the maximal entanglement for these three coupling configurations can be enhanced in the case of small time delays. This work can be utilized for the generation and control of entanglement in quantum networks based on giant-atom waveguide-QED systems, which have wide potential applications in quantum information processing.",2303.14746v2 2023-03-27,Production of genuine multimode entanglement in circular waveguides with long-range interactions,"Starting with a product initial state, squeezed (squeezed coherent) state in one of the modes, and vacuum in the rest, we report that a circular waveguide comprising modes coupled with varying coupling strength is capable of producing genuine multimode entanglement (GME), quantified via the generalized geometric measure (GGM). We demonstrate that for a fixed coupling and squeezing strength, the GME content of the resulting state increases as the range of couplings between the waveguides increases, although the GGM collapses and revives with the variation of coupling strength and time. The advantage of long-range coupling can be emphasized by measuring the area under the GGM curve, which clearly illustrates the growing trends of GME with the increasing range of couplings. Moreover, long-range couplings help in generating a higher GGM for a fixed coupling strength. We analytically determine the exact expression of GGM for systems involving an arbitrary number of modes, when all the modes interact with each other equally. The entire analysis is performed in the phase-space formalism. We manifest the constructive effect of disorder in the coupling parameter, which promises a steady production of GME, independent of the coupling strength.",2303.15137v2 2023-06-20,High frequency oscillations in spin-torque nano oscillator due to bilinear coupling,"Exchange coupling in an interfacial context is crucial for spin-torque nano oscillator (STNO) that consists of a non-magnetic spacer which is alloyed with a ferromagnetic material. Currently, investigations on the dynamics of the free layer magnetization and frequency enhancement in the STNO with bilinear coupling are still being actively pursued. In the present work, we investigate the dynamics of the STNO in the presence of bilinear coupling but in the absence of an external magnetic field by analyzing the associated Landau-Lifshitz-Gilbert-Sloncewski(LLGS) equation, and consequently the impact of the bilinear coupling on the dynamics of the magnetization of the free layer is studied. It is observed that the frequency of the oscillations in the magnetization component along the direction of the pinned layer polarization can be enhanced above 300 GHz by positive bilinear coupling and up to around 30 GHz by negative bilinear coupling. We further reveal a transition from in-plane to out-of-plane precession both for positive and negative bi-linear couplings. We also analyze the switching of the magnetization for different values of current and bilinear coupling. Our detailed investigations of STNO with bilinear coupling aim at the possibilities of high-frequency devices by considering the applied current and bilinear coupling in the absence of a magnetic field.",2306.11415v1 2023-07-03,The Schwinger effect by axial coupling in natural inflation model,"We investigate the process of the Schwinger effect by axial coupling in the natural single-field inflation model in two parts. First we consider the Schwinger effect when the conformal invariance of Maxwell action should be broken by axial coupling $ I(\phi)F_{\mu\nu}\tilde{F}^{\mu\nu} $ with the inflaton field by identifying the standard horizon scale $ k=aH $ at the very beginning of inflation for additional boundary term and use several values of coupling constant $ \chi_{1} $ and estimate electric and magnetic energy densities and energy density of produced charged particles due to the Schwinger effect.We find that for both coupling functions the energy density of the produced charged particles due to the Schwinger effect is so high and spoils inflaton field.In fact the strong coupling or back-reaction occurs because the energy density of produced charged particles is exceeding of inflaton field.We use two coupling functions to break conformal invariance of maxwell action.The simplest coupling function $ I\left(\phi\right)=\chi_{1}\frac{\phi}{M_{p}} $ and a curvature based coupling function $ I\left(\phi\right)= 12\chi_{1}e^{\left(\sqrt{\frac{2}{3}}\frac{\phi}{M_{p}}\right)}\left[\frac{1}{3M_{p}^{2}}\left(4V\left(\phi\right)\right)+\frac{\sqrt{2}}{\sqrt{3}M_{p}}\left(\frac{dV}{d\phi}\right)\right] $ where $V\left(\phi\right) $ is the potential of natural inflation. In second part , in oder to avoid strong back-reaction problem we identify the horizon scale $ k_{H}=aH|\zeta| , \zeta=\frac{{I}^{\prime}\left(\phi\right)\dot{\phi}}{H} $ in which a given Fourier begins to become tachyonically unstable.The effect of this scale is reducing the value of coupling constant $ \chi_{1} $ and weakening the back-reaction problem but in both cases strong coupling or strong back-reaction exists and the Schwinger effect is impossible.",2307.00945v1 2023-07-28,Cascades of turbulent kinetic energy and multicomponent scalars in a momentum-scalar coupling turbulence driven by multiscale forces under homogeneous and isotropic hypotheses,"Momentum-scalar coupling turbulence, a phenomenon observed in both natural and engineering contexts, involves the intricate interaction between multicomponent scalars and multiscale forces (i.e. multiple coupling mechanisms), resulting in a wide array of manifestations. Despite its importance, limited research has been conducted to comprehend the influence of these multicomponent and multiple coupling mechanisms on turbulence cascades. Hence, this study aims to provide a preliminary and theoretical exploration into how these multiple coupling mechanisms govern the cascades of turbulent kinetic energy and multicomponent scalars. The key findings of this study can be summarized as follows: (1) Validation of Quad-cascade processes. (2) Examination of various cases involving single scalar components but multiple coupling mechanisms. Of particular interest is the coexistence of buoyancy-driven turbulence and electrokinetic turbulence, which introduces a new VF subrange resulting from their nonlinear interaction. Another extension considers an exponential modulation function, equivalent to the coexistence of multiple coupling mechanisms acting on a single scalar. The study identifies two new VF subranges. (3) Binary scalar components and coupling mechanisms are investigated, indicating coupling mechanisms with significantly different strengths can also induce complex interactions and new VF subranges. This highlights the challenges inherent in addressing the simultaneous presence of multiple scalar components and coupling mechanisms. This research endeavor illuminates the theoretical understanding of the diverse scaling properties observed in momentum-scalar coupling turbulence across different scenarios.",2307.15473v2 1996-03-04,Period Doublings in Coupled Parametrically Forced Damped Pendulums,"We study period doublings in $N$ $(N=2,3,4, \dots)$ coupled parametrically forced damped pendulums by varying $A$ (the amplitude of the external driving force) and $c$ (the strength of coupling). With increasing $A$, the stationary point undergoes multiple period-doubling transitions to chaos. We first investigate the two-coupled case with $N=2$. For each period-doubling transition to chaos, the critical set consists of an infinity of critical line segments and the zero-coupling critical point lying on the line $A=A^*_i$ in the $A-c$ plane, where $A^*_i$ is the $i$th transition point for the uncoupled case. We find three kinds of critical behaviors, depending on the position on the critical set. They are the same as those for the coupled one-dimensional maps. Finally, the results of the $N=2$ case are extended to many-coupled cases with $N \geq 3$, in which the critical behaviors depend on the range of coupling.",9603002v1 2005-02-01,Can Frustration Preserve a Quasi-Two-Dimensional Spin Fluid?,"Using spin-wave theory, we show that geometric frustration fails to preserve a two-dimensional spin fluid. Even though frustration can remove the interlayer coupling in the ground-state of a classical anti-ferromagnet, spin layers innevitably develop a quantum-mechanical coupling via the mechanism of ``order from disorder''. We show how the order from disorder coupling mechanism can be viewed as a result of magnon pair tunneling, a process closely analogous to pair tunneling in the Josephson effect. In the spin system, the Josephson coupling manifests itself as a a biquadratic spin coupling between layers, and for quantum spins, these coupling terms are as large as the inplane coupling. An alternative mechanism for decoupling spin layers occurs in classical XY models in which decoupled ""sliding phases"" of spin fluid can form in certain finely tuned conditions. Unfortunately, these finely tuned situations appear equally susceptible to the strong-coupling effects of quantum tunneling, forcing us to conclude that in general, geometric frustration cannot preserve a two-dimensional spin fluid.",0502003v2 2005-06-23,Spin properties of single electron states in coupled quantum dots,"Spin properties of single electron states in laterally coupled quantum dots in the presence of a perpendicular magnetic field are studied by exact numerical diagonalization. Dresselhaus (linear and cubic) and Bychkov-Rashba spin-orbit couplings are included in a realistic model of confined dots based on GaAs. Group theoretical classification of quantum states with and without spin orbit coupling is provided. Spin-orbit effects on the g-factor are rather weak. It is shown that the frequency of coherent oscillations (tunneling amplitude) in coupled dots is largely unaffected by spin-orbit effects due to symmetry requirements. The leading contributions to the frequency involves the cubic term of the Dresselhaus coupling. Spin-orbit coupling in the presence of magnetic field leads to a spin-dependent tunneling amplitude, and thus to the possibility of spin to charge conversion, namely spatial separation of spin by coherent oscillations in a uniform magnetic field. It is also shown that spin hot spots exist in coupled GaAs dots already at moderate magnetic fields, and that spin hot spots at zero magnetic field are due to the cubic Dresselhaus term only.",0506610v1 2005-11-24,Dynamics of Coupled Qubits Interacting with an Off-Resonant Cavity,"We study a model for a pair of qubits which interact with a single off-resonant cavity mode and, in addition, exhibit a direct inter-qubit coupling. Possible realizations for such a system include coupled superconducting qubits in a line resonator as well as exciton states or electron spin states of quantum dots in a cavity. The emergent dynamical phenomena are strongly dependent on the relative energy scales of the inter-qubit coupling strength, the coupling strength between qubits and cavity mode, and the cavity mode detuning. We show that the cavity mode dispersion enables a measurement of the state of the coupled-qubit system in the perturbative regime. We discuss the effect of the direct inter-qubit interaction on a cavity-mediated two-qubit gate. Further, we show that for asymmetric coupling of the two qubits to the cavity, the direct inter-qubit coupling can be controlled optically via the ac Stark effect.",0511592v2 2006-05-16,Galvanic coupling of flux qubits: simple theory and tunability,"Galvanic coupling of small-area (three-junction) flux qubits, using shared large Josephson junctions, has been shown to yield appreciable interaction strengths in a flexible design, which does not compromise the junctions' intrinsic good coherence properties. For an introduction, I recapitulate an elementary derivation of the coupling strength, which is subsequently generalized to the case of tunable coupling for a current-biased shared junction. While the ability to vary coupling constants by, say, 20% would be useful in experiments, sign-tunability (implying switchability) is highly preferable for several quantum-computing paradigms. This note sketches two ideas: a ""crossbar"" design with competing ferro- and antiferromagnetic current-biased tunable couplings, and a ""mediated"" one involving an extra loop between the qubits. The latter is a variation on proposals for tunable capacitive coupling of charge qubits, and tunable inductive coupling of large-area flux qubits.",0605398v1 1998-10-01,Vector Boson Pair Production and Trilinear Gauge Boson Couplings - Results From the Tevatron,"Direct measurements of vector boson pair production processes and trilinear gauge boson couplings have been conducted by the CDF and DO Collaborations. Preliminary results from searches for anomalous WW/WZ->muon-neutrino-jet-jet and WZ->e-e-e-neutrino production are presented. 95% CL anomalous coupling limits from previously published DO results are -0.20 < lambda < 0.20 (Delta kappa=0) and -0.30 < Delta kappa < 0.43 (lambda=0) for Lambda=2000 GeV where the WWgamma couplings are assumed to equal the WWZ couplings. Combined DO + LEP experiment anomalous coupling limits are presented for the first time. 95% CL limits are -0.16 two pseudoscalar mesons $PP$ are almost same as the coupling $A'$ for the I=0. On the other hand, the coupling constant $A$ for $I=1, I=1/2$ which represents the low mass scalar meson $N$ -> $PP$ are far from the coupling constant $A$ for I=0. We consider a resolution for this discrepancy. Coupling constant $A''$ for glueball $G$ -> $PP$ is smaller than the coupling $A'$. $\theta_P$ is $40^\circ \sim 50^\circ$.",0305296v1 1991-10-21,Complete structure of Z_n Yukawa couplings,"We give the complete twisted Yukawa couplings for all the Z_n orbifold constructions in the most general case, i.e. when orbifold deformations are considered. This includes a certain number of tasks. Namely, determination of the allowed couplings, calculation of the explicit dependence of the Yukawa couplings values on the moduli expectation values (i.e. the parameters determining the size and shape of the compactified space), etc. The final expressions are completely explicit, which allows a counting of the DIFFERENT Yukawa couplings for each orbifold (with and without deformations). This knowledge is crucial to determine the phenomenological viability of the different schemes, since it is directly related to the fermion mass hierarchy. Other facts concerning the phenomenological profile of Z_n orbifolds are also discussed, e.g. the existence of non--diagonal entries in the fermion mass matrices, which is related to a non--trivial structure of the Kobayashi--Maskawa matrix. Finally some theoretical results are given, e.g. the no--participation of (1,2) moduli in twisted Yukawa couplings. Likewise, (1,1) moduli associated with fixed tori which are involved in the Yukawa coupling, do not affect the value of the coupling.",9110060v1 2005-04-25,Coupled boundary and bulk fields in anti-de Sitter,"We investigate the dynamics of a boundary field coupled to a bulk field with a linear coupling in an anti-de Sitter bulk spacetime bounded by a Minkowski (Randall-Sundrum) brane. An instability criterion for the coupled boundary and bulk system is found. There exists a tachyonic bound state when the coupling is above a critical value, determined by the masses of the brane and bulk fields and AdS curvature scale. This bound state is normalizable and localised near the brane, and leads to a tachonic instability of the system on large scales. Below the critical coupling, there is no tachyonic state and no bound state. Instead, we find quasi-normal modes which describe stable oscillations, but with a finite decay time. Only if the coupling is tuned to the critical value does there exist a massless stable bound state, as in the case of zero coupling for massless fields. We discuss the relation to gravitational perturbations in the Randall-Sundrum brane-world.",0504201v1 2003-11-13,A New Method of Strong-Coupling Expansion,"In this paper, we propose a new method of strong-coupling expansion",0311021v1 2003-04-07,On dispersionless coupled modified KP hierarchy,"We define and study dispersionless coupled modified KP hierarchy, which incorporates two different versions of dispersionless modified KP hierarchies.",0304007v1 2003-11-24,Synchronization of globally coupled nonidentical maps with inhomogeneous delayed interactions,"We study the synchronization of a coupled map lattice consisting of a one-dimensional chain of logistic maps. We consider global coupling with a time-delay that takes into account the finite velocity of propagation of interactions. We recently showed that clustering occurs for weak coupling, while for strong coupling the array synchronizes into a global state where each element sees all other elements in its current, present state [Physica A {\bf 325} (2003) 186, Phys. Rev. E {\bf 67} (2003) 056219]. In this paper we study the effects of in-homogeneities, both in the individual maps, which are non-identical maps evolving in period-2 orbits, and in the connection links, which have non-uniform strengths. We find that the global synchronization regime occurring for strong coupling is robust to heterogeneities: for strong enough average coupling the inhomogeneous array still synchronizes in a global state in which each element sees the other elements in positions close to its current state. However, the clustering behaviour occurring for small coupling is sensitive to inhomogeneities and differs from that occurring in the homogeneous array.",0311051v1 2006-05-28,Generic N-coupled maps in Bose-Mesner algebra perspective,"By choosing a dynamical system with d different couplings, one can rearrange a system based on the graph with given vertex dependent on the dynamical system elements. The relation between the dynamical elements (coupling) is replaced by a relation between the vertexes. Based on the E_0 transverse projection operator. We addressed synchronization problem of an array of the linearly coupled map lattices of identical discrete time systems. The synchronization rate is determined by the second largest eigenvalue of the transition probability matrix. Algebraic properties of the Bose-Mesner algebra with an associated scheme with definite spectrum has been used in order to study the stability of the coupled map lattice. Associated schemes play a key role and may lead to analytical methods in studying the stability of the dynamical systems. The relation between the coupling parameters and the chaotic region is presented. It is shown that the feasible region is analytically determined by the number of couplings (i.e, by increasing the number of coupled maps the feasible region is restricted). It is very easy to apply our criteria to the system being studied and they encompass a wide range of coupling schemes including most of the popularly used ones in the literature.",0605050v1 2005-02-22,On the role of chemical synapses in coupled neurons with noise,"We examine the behavior in the presence of noise of an array of Morris-Lecar neurons coupled via chemical synapses. Special attention is devoted to comparing this behavior with the better known case of electrical coupling arising via gap junctions. In particular, our numerical simulations show that chemical synapses are more efficient than gap junctions in enhancing coherence at an optimal noise (what is known as array-enhanced coherence resonance): in the case of (nonlinear) chemical coupling, we observe a substantial increase in the stochastic coherence of the system, in comparison with (linear) electrical coupling. We interpret this qualitative difference between both types of coupling as arising from the fact that chemical synapses only act while the presynaptic neuron is spiking, whereas gap junctions connect the voltage of the two neurons at all times. This leads in the electrical coupling case to larger correlations during interspike time intervals which are detrimental to the array-enhanced coherence effect. Finally, we report on the existence of a system-size coherence resonance in this locally coupled system, exhibited by the average membrane potential of the array.",0502025v1 2005-06-29,A unified approach to realize universal quantum gates in a coupled two-qubit system with fixed always-on coupling,"We demonstrate that in a coupled two-qubit system any single-qubit gate can be decomposed into two conditional two-qubit gates and that any conditional two-qubit gate can be implemented by a manipulation analogous to that used for a controlled two-qubit gate. Based on this we present a unified approach to implement universal single-qubit and two-qubit gates in a coupled two-qubit system with fixed always-on coupling. This approach requires neither supplementary circuit or additional physical qubits to control the coupling nor extra hardware to adjust the energy level structure. The feasibility of this approach is demonstrated by numerical simulation of single-qubit gates and creation of two-qubit Bell states in rf-driven inductively coupled two SQUID flux qubits with realistic device parameters and constant always-on coupling.",0506261v2 2007-07-16,Preheating in Derivatively-Coupled Inflation Models,"We study preheating in theories where the inflaton couples derivatively to scalar and gauge fields. Such couplings may dominate in natural models of inflation, in which the flatness of the inflaton potential is related to an approximate shift symmetry of the inflaton. We compare our results with previously studied models with non-derivative couplings. For sufficiently heavy scalar matter, parametric resonance is ineffective in reheating the universe, because the couplings of the inflaton to matter are very weak. If scalar matter fields are light, derivative couplings lead to a mild long-wavelength instability that drives matter fields to non-zero expectation values. In this case however, long-wavelength fluctuations of the light scalar are produced during inflation, leading to a host of cosmological problems. In contrast, axion-like couplings of the inflaton to a gauge field do not lead to production of long-wavelength fluctuations during inflation. However, again because of the weakness of the couplings to the inflaton, parametric resonance is not effective in producing gauge field quanta.",0707.2177v2 2007-11-14,Dynamical Coupled-Channels Analysis at EBAC,"The status of dynamical coupled-channel analysis at Excited Baryon Analysis Center (EBAC) of Jefferson Laboratory is reported.",0711.2193v1 2008-02-01,Trilinear Higgs couplings in the two Higgs doublet model with CP violation,"We carry out a detailed analysis of the general two Higgs doublet model with CP violation. We describe two different parametrizations of this model, and then study the Higgs boson masses and the trilinear Higgs couplings for these two parametrizations. Within a rather general model, we find that the trilinear Higgs couplings have a significant dependence on the details of the model, even when the lightest Higgs boson mass is taken to be a fixed parameter. We include radiative corrections in the one-loop effective potential approximation in our analysis of the Higgs boson masses and the Higgs trilinear couplings. The one-loop corrections to the trilinear couplings of the two Higgs doublet model also depend significantly on the details of the model, and can be rather large. We study quantitatively the trilinear Higgs couplings, and show that these couplings are typically several times larger than the corresponding Standard Model trilinear Higgs coupling in some regions of the parameter space. We also briefly discuss the decoupling limit of the two Higgs doublet model.",0802.0060v2 2008-05-02,Josephson Effect through an isotropic magnetic molecule,"We investigate the Josephson effect through a molecular quantum dot magnet connected to superconducting leads. The molecule contains a magnetic atom, whose spin is assumed to be isotropic. It is coupled to the electron spin on the dot via exchange coupling. Using the numerical renormalization group method we calculate the Andreev levels and the supercurrent and examine intertwined effect of the exchange coupling, Kondo correlation, and superconductivity on the current. Exchange coupling typically suppresses the Kondo correlation so that the system undergoes a phase transition from 0 to $\pi$ state as the modulus of exchange coupling increases. Antiferromagnetic coupling is found to drive exotic transitions: the reentrance to the $\pi$ state for a small superconducting gap and the restoration of 0 state for large antiferromagnetic exchange coupling. We suggest that the asymmetric dependence of supercurrent on the exchange coupling could be used as to detect its sign in experiments.",0805.0301v3 2008-10-31,On semilinear elliptic equations with global coupling,"We consider nonlinear elliptic equations which contains global coupling as a nonlinear term. We classify the existence of all possible positive solutions to this problem.",0810.5646v1 2008-11-21,Phase Synchronization in Unidirectionally Coupled Ikeda Time-delay Systems,"Phase synchronization in unidirectionally coupled Ikeda time-delay systems exhibiting non-phase-coherent hyperchaotic attractors of complex topology with highly interwoven trajectories is studied. It is shown that in this set of coupled systems phase synchronization (PS) does exist in a range of the coupling strength which is preceded by a transition regime (approximate PS) and a nonsynchronous regime. However, exact generalized synchronization does not seem to occur in the coupled Ikeda systems (for the range of parameters we have studied) even for large coupling strength, in contrast to our earlier studies in coupled piecewise-linear and Mackey-Glass systems \cite{dvskml2006,dvskml2008}. The above transitions are characterized in terms of recurrence based indices, namely generalized autocorrelation function $P(t)$, correlation of probability of recurrence (CPR), joint probability of recurrence (JPR) and similarity of probability of recurrence (SPR). The existence of phase synchronization is also further confirmed by typical transitions in the Lyapunov exponents of the coupled Ikeda time-delay systems and also using the concept of localized sets.",0811.3471v1 2008-12-15,Slow-Roll Inflation in the Presence of a Dark Energy Coupling,"In models of coupled dark energy, in which a dark energy scalar field couples to other matter components, it is natural to expect a coupling to the inflaton as well. We explore the consequences of such a coupling in the context of single field slow-roll inflation. Assuming an exponential potential for the quintessence field we show that the coupling to the inflaton causes the quintessence field to be attracted towards the minimum of the effective potential. If the coupling is large enough, the field is heavy and is located at the minimum. We show how this affects the expansion rate and the slow-roll of the inflaton field, and therefore the primordial perturbations generated during inflation. We further show that the coupling has an important impact on the processes of reheating and preheating.",0812.2843v2 2009-03-17,Dissipative diamagnetism with anomalous coupling and third law,"In this work, low temperature thermodynamic behaviour in the context of dissipative diamagnetism with anomalous coupling is analyzed. We find that finite dissipation substitutes the zero-coupling result of exponential decay of entropy by a power law behaviour at low temperature. For Ohmic bath, entropy vanishes linearly with temperature, $T$, in conformity with Nernst's theorem. It is also shown that entropy decays faster in the presence of anomalous coupling than that of the usual coordinate-coordinate coupling. It is observed that velocity-velocity coupling is the most advantageous coupling scheme to ensure the third law of thermodynamics. It is also revealed that different thermodynamic functions are independent of magnetic field at very low temperature for various coupling schemes discussed in this work.",0903.2952v1 2009-06-21,Phase coupling estimation from multivariate phase statistics,"Coupled oscillators are prevalent throughout the physical world. Dynamical system formulations of weakly coupled oscillator systems have proven effective at capturing the properties of real-world systems. However, these formulations usually deal with the `forward problem': simulating a system from known coupling parameters. Here we provide a solution to the `inverse problem': determining the coupling parameters from measurements. Starting from the dynamic equations of a system of coupled phase oscillators, given by a nonlinear Langevin equation, we derive the corresponding equilibrium distribution. This formulation leads us to the maximum entropy distribution that captures pair-wise phase relationships. To solve the inverse problem for this distribution, we derive a closed form solution for estimating the phase coupling parameters from observed phase statistics. Through simulations, we show that the algorithm performs well in high dimensions (d=100) and in cases with limited data (as few as 100 samples per dimension). Because the distribution serves as the unique maximum entropy solution for pairwise phase statistics, the distribution and estimation technique can be broadly applied to phase coupling estimation in any system of phase oscillators.",0906.3844v1 2009-06-30,Rational approximations in Analytic QCD,"We consider the ``modified Minimal Analytic'' (mMA) coupling that involves an infrared cut to the standard MA coupling. The mMA coupling is a Stieltjes function and, as a consequence, the paradiagonal Pade approximants converge to the coupling in the entire $Q^2$-plane except on the time-like semiaxis below the cut. The equivalence between the narrow width approximation of the discontinuity function of the coupling, on the one hand, and this Pade (rational) approximation of the coupling, on the other hand, is shown. We approximate the analytic analogs of the higher powers of mMA coupling by rational functions in such a way that the singularity region is respected by the approximants.Several comparisons, for real and complex arguments $Q^2$, between the exact and approximate expressions are made and the speed of convergence is discussed. Motivated by the success of these approximants, an improvement of the mMA coupling is suggested, and possible uses in the reproduction of experimental data are discussed.",0907.0033v2 2009-07-29,Continuum-continuum coupling and polarization potentials for weakly bound system,"We investigate the influence of couplings among continuum states in collisions of weakly bound nuclei. For this purpose, we compare cross sections for complete fusion, breakup and elastic scattering evaluated by continuum discretized coupled channel (CDCC) calculations, including and not including these couplings. In our study, we discuss this influence in terms of the polarization potentials that reproduce the elastic wave function of the coupled coupled channel method in single channel calculations. We find that the inclusion of couplings among the continuum states renders the real part of the polarization potential more repulsive, whereas it leads to weaker apsorption to the breakup channel. We show that the non-inclusion of continuum-continuum couplings in CDCC calculations may not lead to qualitative and quantitative wrong conclusions.",0907.5167v2 2009-08-14,Optimal co-adapted coupling for a random walk on the hyper-complete-graph,"The problem of constructing an optimal co-adapted coupling for a pair of symmetric random walks on $Z_2^d$ was considered by Connor and Jacka (2008), and the existence of a coupling which is stochastically fastest in the class of all such co-adapted couplings was demonstrated. In this paper we show how to generalise this construction to an optimal co-adapted coupling for the continuous-time symmetric random walk on $K_n^d$, where $K_n$ is the complete graph with $n$ vertices. Moreover, we show that although this coupling is not maximal for any $n$ (i.e. it does not achieve equality in the coupling inequality), it does tend to a maximal coupling as $n\to\infty$.",0908.2038v2 2009-11-12,Feedback-dependent control of stochastic synchronization in coupled neural systems,"We investigate the synchronization dynamics of two coupled noise-driven FitzHugh-Nagumo systems, representing two neural populations. For certain choices of the noise intensities and coupling strength, we find cooperative stochastic dynamics such as frequency synchronization and phase synchronization, where the degree of synchronization can be quantified by the ratio of the interspike interval of the two excitable neural populations and the phase synchronization index, respectively. The stochastic synchronization can be either enhanced or suppressed by local time-delayed feedback control, depending upon the delay time and the coupling strength. The control depends crucially upon the coupling scheme of the control force, i.e., whether the control force is generated from the activator or inhibitor signal, and applied to either component. For inhibitor self-coupling, synchronization is most strongly enhanced, whereas for activator self-coupling there exist distinct values of the delay time where the synchronization is strongly suppressed even in the strong synchronization regime. For cross-coupling strongly modulated behavior is found.",0911.2334v1 2010-02-03,Tailoring Interlayer Exchange Coupling of Ferromagnetic Films Across MgO with Fe Nanoclusters,"We investigate the interlayer exchange coupling in Fe/MgO/Fe and Fe/MgO/Co systems with magnetic Fe nanoclusters embedded in the MgO spacer. Samples are grown by molecular beam epitaxy (MBE) and utilize wedged MgO films to independently vary the film thickness and the position of the Fe nanoclusters. Depending on the position of the Fe nanoclusters, the bilinear coupling (J1) exhibits strong variations in magnitude and can even switch between antiferromagnetic and ferromagnetic. This effect is explained by the magnetic coupling between the ferromagnetic films and the magnetic nanoclusters. Interestingly, the coupling of Fe nanoclusters to a Co film is 160% stronger than their coupling to a Fe film (at MgO spacing of 0.56 nm). This is much greater than the coupling difference of 20% observed in the analogous thin film systems (i.e. Fe/MgO/Co vs. Fe/MgO/Fe), identifying an interesting nano-scaling effect related to the coupling between films and nanoclusters.",1002.0627v1 2010-03-12,Dynamics of quartz tuning fork force sensors used in scanning probe microscopy,"We have performed an experimental characterization of the dynamics of oscillating quartz tuning forks which are being increasingly used in scanning probe microscopy as force sensors. We show that tuning forks can be described as a system of coupled oscillators. Nevertheless, this description requires the knowledge of the elastic coupling constant between the prongs of the tuning fork, which has not yet been measured. Therefore tuning forks have been usually described within the single oscillator or the weakly coupled oscillators approximation that neglects the coupling between the prongs. We propose three different procedures to measure the elastic coupling constant: an opto-mechanical method, a variation of the Cleveland method and a thermal noise based method. We find that the coupling between the quartz tuning fork prongs has a strong influence on the dynamics and the measured motion is in remarkable agreement with a simple model of coupled harmonic oscillators. The precise determination of the elastic coupling between the prongs of a tuning fork allows to obtain a quantitative relation between the resonance frequency shift and the force gradient acting at the free end of a tuning fork prong.",1003.2607v1 2010-04-28,Tunable Fano-Kondo resonance in side-coupled double quantum dot system,"We study the interference between the Fano and Kondo effects in a side-coupled double-quantum- dot system where one of the quantum dots couples to conduction electron bath while the other dot only side-couples to the first dot via antiferromagnetic (AF) spin exchange coupling. We apply both the perturbative renormalization group (RG) and numerical renormalization group (NRG) approaches to study the effect of AF coupling on the Fano lineshape in the conduction leads. With particle-hole symmetry, the AF exchange coupling competes with the Kondo effect and leads to a local spin-singlet ground state for arbitrary small coupling, so called ""two-stage Kondo effect"". As a result, via NRG we find the spectral properties of the Fano lineshape in the tunneling density of states (TDOS) of conduction electron leads shows double dip-peak features at the energy scale around the Kondo temperature and the one much below it, corresponding to the two-stage Kondo effect; it also shows an universal scaling behavior at very low energies. We find the qualitative agreement between the NRG and the perturbative RG approach. Relevance of our work to the experiments is discussed.",1004.4961v1 2010-07-29,Non-minimally coupled f(R) Cosmology,"We investigate the consequences of non-minimal gravitational coupling to matter and study how it differs from the case of minimal coupling by choosing certain simple forms for the nature of coupling, The values of the parameters are specified at $z=0$ (present epoch) and the equations are evolved backwards to calculate the evolution of cosmological parameters. We find that the Hubble parameter evolves more slowly in non-minimal coupling case as compared to the minimal coupling case. In both the cases, the universe accelerates around present time, and enters the decelerating regime in the past. Using the latest Union2 dataset for supernova Type Ia observations as well as the data for baryon acoustic oscillation (BAO) from SDSS observations, we constraint the parameters of Linder exponential model in the two different approaches. We find that there is a upper bound on model parameter in minimal coupling. But for non-minimal coupling case, there is range of allowed values for the model parameter.",1007.5250v1 2010-09-07,Voids in Coupled Scalar Field Cosmology,"We study the properties of voids in two different types of coupled scalar field theories. Due to the fifth force produced by the scalar field coupling, the matter particles feel stronger attraction amongst each other and cluster more quickly than they do in the standard LCDM model. Consequently voids in the coupled scalar field theories start to develop earlier and end up bigger, which is confirmed by our numerical simulations. We find that a significantly larger portion of the whole space is under-densed in the coupled scalar field theories and there are more voids whose sizes exceed given thresholds. This is more prominent in early times because at later times the under-dense regions have already been evacuated in coupled scalar field theories and there is time for the LCDM model to catch up. The coupled scalar field theories also predict a sharper transition between voids and high density regions. All in all, the qualitative behaviour is different not only from the LCDM result, but also amongst specific coupled scalar field models, making voids a potential candidate to test alternative ideas about the cosmic structure formation.",1009.1406v1 2011-02-19,Realistic Rashba and Dressehaus spin-orbit coupling for neutral atoms,"We describe a new class of atom-laser coupling schemes which lead to spin-orbit coupled Hamiltonians for ultra-cold neutral atoms. By properly setting the optical phases, a pair of degenerate pseudospin states emerge as the lowest energy states in the spectrum, and are thus immune to collisionally induced decay. These schemes use $N$ cyclically coupled ground or metastable internal states. We specialize to two situations: a three level case giving fixed Rashba coupling, and a four-level case that adds a controllable Dresselhaus contribution. We describe an implementation of the four level scheme for $\Rb87$ and analyze the sensitivity of our approach to realistic experimental limitations and imperfections. Lastly, we argue that no laser coupling scheme can give pure Rashba or Dresselhaus coupling: akin to condensed matter systems, higher order terms spoil the symmetry of these couplings. However, for sufficiently intense laser fields the continuous rotational symmetry approximately holds, making the Rashba Hamiltonian applicable for cold atoms.",1102.3945v2 2011-02-22,Synchronization of the cardiac pacemaker model with delayed pulse-coupling,"We consider the integrate-and-fire model of the cardiac pacemaker with delayed pulsatile coupling. Sufficient conditions of synchronization are obtained for identical and non-identical oscillators.",1102.4462v1 2011-07-14,Fundamental solutions for isotropic size-dependent couple stress elasticity,"Fundamental solutions for two- and three-dimensional linear isotropic size-dependent couple stress elasticity are derived, based upon the decomposition of displacement fields into dilatational and solenoidal components. While several fundamental solutions have appeared previously in the literature, the present version is for the newly developed fully determinate couple stress theory. Within this theory, the couple stress tensor is skewsymmetrical and thus possesses vectorial character. The present derivation provides solutions for infinite domains of elastic materials under the influence of unit concentrated forces and couples. Unlike all previous work, unique solutions for displacements, rotations, force-stresses and couple-stresses are established, along with the corresponding force-tractions and couple-tractions. These fundamental solutions are central in analysis methods based on Green's functions for infinite domains and are required as kernels in the corresponding boundary integral formulations for size-dependent couple stress elastic materials.",1107.2912v1 2011-07-18,Supersymmetry constraints on the R^4 multiplet in type IIB on T^2,"We consider a class of eight derivative interactions in the effective action of type IIB string theory compactified on T^2. These 1/2 BPS interactions have moduli dependent couplings. We impose the constraints of supersymmetry to show that each of these couplings satisfy a first order differential equation on moduli space which relate it to other couplings in the same supermuliplet. These equations can be iterated to give second order differential equations for the various couplings. The couplings which only depend on the SO(2)\SL(2,R) moduli satisfy Laplace equation on moduli space, and are given by modular forms of SL(2,Z). On the other hand, the ones that only depend on the SO(3)\SL(3,R) moduli satisfy Poisson equation on moduli space, where the source terms are given by other couplings in the same supermultiplet. The couplings of the interactions which are charged under SU(2) are not automorphic forms of SL(3,Z). Among the interactions we consider, the R^4 coupling depends on all the moduli.",1107.3353v2 2011-07-26,How Coupling Determines the Entrainment of Circadian Clocks,"Autonomous circadian clocks drive daily rhythms in physiology and behaviour. A network of coupled neurons, the suprachiasmatic nucleus (SCN), serves as a robust self-sustained circadian pacemaker. Synchronization of this timer to the environmental light-dark cycle is crucial for an organism's fitness. In a recent theoretical and experimental study it was shown that coupling governs the entrainment range of circadian clocks. We apply the theory of coupled oscillators to analyse how diffusive and mean-field coupling affects the entrainment range of interacting cells. Mean-field coupling leads to amplitude expansion of weak oscillators and, as a result, reduces the entrainment range. We also show that coupling determines the rigidity of the synchronized SCN network, i.e. the relaxation rates upon perturbation. %(Floquet exponents). Our simulations and analytical calculations using generic oscillator models help to elucidate how coupling determines the entrainment of the SCN. Our theoretical framework helps to interpret experimental data.",1107.5137v1 2011-09-19,Dynamics of nuclear single-particle structure in covariant theory of particle-vibration coupling: from light to superheavy nuclei,"The impact of particle-vibration coupling and polarization effects due to deformation and time-odd mean fields on single-particle spectra is studied systematically in doubly magic nuclei from low mass $^{56}$Ni up to superheavy ones. Particle-vibration coupling is treated fully self-consistently within the framework of relativistic particle-vibration coupling model. Polarization effects due to deformation and time-odd mean field induced by odd particle are computed within covariant density functional theory. It has been found that among these contributions the coupling to vibrations makes a major impact on the single-particle structure. The impact of particle-vibration coupling and polarization effects on calculated single-particle spectra, the size of the shell gaps, the spin-orbit splittings and the energy splittings in pseudospin doublets is discussed in detail; these physical observables are compared with experiment. Particle-vibration coupling has to be taken into account when model calculations are compared with experiment since this coupling is responsible for observed fragmentation of experimental levels; experimental spectroscopic factors are reasonably well described in model calculations.",1109.3969v1 2011-10-17,Optimal value functions for weakly coupled systems: a posteriori estimates,"We consider weakly coupled LQ optimal control problems and derive estimates on the sensitivity of the optimal value function in dependence of the coupling strength. In order to improve these sensitivity estimates a ""coupling adapted"" norm is proposed. Our main result is that if a weak coupling suffices to destabilize the closed loop system with the optimal feedback of the uncoupled system then the value function might change drastically with the coupling. As a consequence, it is not reasonable to expect that a weakly coupled system possesses a weakly coupled optimal value function. Also, for a known result on the connection of the separation operator and the stability radius a new and simpler proof is given.",1110.3616v2 2012-02-01,Amplitude death in systems of coupled oscillators with distributed-delay coupling,"This paper studies the effects of coupling with distributed delay on the suppression of oscillations in a system of coupled Stuart-Landau oscillators. Conditions for amplitude death are obtained in terms of strength and phase of the coupling, as well as the mean time delay and the width of the delay distribution for uniform and gamma distributions. Analytical results are confirmed by numerical computation of the eigenvalues of the corresponding characteristic equations. These results indicate that larger widths of delay distribution increase the regions of amplitude death in the parameter space. In the case of a uniformly distributed delay kernel, for sufficiently large width of the delay distribution it is possible to achieve amplitude death for an arbitrary value of the average time delay, provided that the coupling strength has a value in the appropriate range. For a gamma distribution of delay, amplitude death is also possible for an arbitrary value of the average time delay, provided that it exceeds a certain value as determined by the coupling phase and the power law of the distribution. The coupling phase has a destabilizing effect and reduces the regions of amplitude death.",1202.0226v1 2012-03-30,Critical behavior in ultra-strong-coupled oscillators,"We investigate the strong coupling regime of a linear $x$-$x$ coupled harmonic oscillator system, by performing a direct diagonalization of the hamiltonian. It is shown that the $x$-$x$ coupled hamiltonian can be equivalently described by a Mach-Zehnder-type interferometer with a quadratic unitary operation in each of its arms. We show a sharp transition of the unitary operation from an elliptical phase rotator to an elliptical squeezer as the coupling gets stronger, which leads to the continuous generation of entanglement, even for a significantly thermal state, in the ultra-strong coupled regime. It is also shown that this critical regime cannot be achieved by a classical Hookian coupling. Finally, the effect of a finite-temperature environment is analyzed, showing that entanglement can still be generated from a thermal state in the ultra-strong coupled regime, but is destroyed rapidly.",1203.6755v3 2012-09-12,Singularity problem in f(R) model with non-minimal coupling,"We consider the non-minimal coupling between matter and the geometry in the f(R) theory. In the new theory which we established, a new scalar $\psi$ has been defined and we give it a certain stability condition. We intend to take a closer look at the dark energy oscillating behavior in the de-Sitter universe and the matter era, from which we derive the oscillating frequency, and the oscillating condition. More importantly, we present the condition of coupling form that the singularity can be solved. We discuss several specific coupling forms, and find logarithmic coupling with an oscillating period $\Delta T\sim\Delta z$ in the matter era $z>4$, can improve singularity in the early universe. The result of numerical calculation verifies our theoretic calculation about the oscillating frequency. Considering two toy models, we find the cosmic evolution in the coupling model is nearly the same as that in the normal f(R) theory when $lna>4$. We also discuss the local tests of the non-minimal coupling f(R) model, and show the constraint on the coupling form.",1209.2619v3 2012-11-29,Strong-coupling effects in dissipatively coupled optomechanical systems,"In this paper we study cavity optomechanical systems in which the position of a mechanical oscillator modulates both the resonance frequency (dispersive coupling) and the linewidth (dissipative coupling) of a cavity mode. Using a quantum noise approach we calculate the optical damping and the optically-induced frequency shift. We find that dissipatively coupled systems feature two parameter regions providing amplification and two parameter regions providing cooling. To investigate the strong-coupling regime, we solve the linearized equations of motion exactly and calculate the mechanical and optical spectra. In addition to signatures of normal-mode splitting that are similar to the case of purely dispersive coupling, the spectra contain a striking feature that we trace back to the Fano line shape of the force spectrum. Finally, we show that purely dissipative coupling can lead to optomechanically-induced transparency which will provide an experimentally convenient way to observe normal-mode splitting.",1211.7029v2 2013-01-11,Spherical Couplings and Multiple Elliptic Integrals,"Various integrals over elliptic integrals are evaluated as couplings on spheres, resulting in some integral and series representations for the mathematical constants $\pi$, $G$ and $\zeta(3)$.",1301.2584v1 2013-04-04,Dynamic environment coupling induce synchronized states in coupled time-delayed electronic circuits,"We experimentally demonstrate the occurrence of various synchronized states in coupled piece-wise linear time-delayed electronic circuits using dynamic environment coupling where the environment has its own intrinsic dynamics via feedback from the circuits. We carry out these experiments in two different coupling configurations, namely mutual and subsystem coupling configurations. Depending upon the coupling strength and the nature of feedback, we observe a transition from nonsynchronization to complete synchronization via phase synchronization and from nonsynchronization to inverse synchronization via inverse-phase synchronization between the circuits in hyperchaotic regime. Snapshots of the time evolution, phase projection plots and localized sets of the circuits as observed experimentally from the oscilloscope, along with supporting numerical simulations confirm the existence of different synchronized states. Further, the transition to different synchronized states can be verified from the changes in the largest Lyapunov exponents, Correlation of Probability of Recurrence and Correlation Coefficient as a function of the coupling strength. We present a detailed linear stability analysis and obtain conditions for different synchronized states.",1304.1254v2 2013-04-07,Mirror and Synchronous Couplings of Geometric Brownian Motions,"The paper studies the question of whether the classical mirror and synchronous couplings of two Brownian motions minimise and maximise, respectively, the coupling time of the corresponding geometric Brownian motions. We establish a characterisation of the optimality of the two couplings over any finite time horizon and show that, unlike in the case of Brownian motion, the optimality fails in general even if the geometric Brownian motions are martingales. On the other hand, we prove that in the cases of the ergodic average and the infinite time horizon criteria, the mirror coupling and the synchronous coupling are always optimal for general (possibly non-martingale) geometric Brownian motions. We show that the two couplings are efficient if and only if they are optimal over a finite time horizon and give a conjectural answer for the efficient couplings when they are suboptimal.",1304.1999v2 2013-05-23,Interplay between new physics in one-loop Higgs couplings and the top-quark Yukawa coupling,"After the discovery of a 126 GeV state at the LHC it is imperative to establish whether this particle really is the Higgs boson of the standard model. The early measurements have not yet pinpointed any of the Higgs couplings to fermions, the Yukawa couplings of the standard model. In this paper we study the values of the top-quark-Higgs coupling, $g_{ht\bar{t}}$, that are still allowed by the one-loop couplings of the Higgs to two gluons or two photons. We first assume that both the gluon fusion production of the Higgs and its decay into two photons proceed through loops with standard model particles only, albeit with an arbitrary top-Higgs coupling. We find that the current Higgs data still allows for 20% deviations in $g_{ht\bar{t}}$ from its standard model value. We then investigate the effect of new particles contributing to the effective one-loop couplings. Specifically we consider a color octet electroweak doublet extension of the scalar sector and find that in this case $g_{ht\bar{t}}$ is allowed to deviate by 40% from its standard model value by the current data.",1305.5420v1 2013-10-15,Vanishing of interband light absorption in a persistent spin helix state,"Spin-orbit coupling plays an important role in various properties of very different materials. Moreover efforts are underway to control the degree and quality of spin-orbit coupling in materials with a concomitant control of transport properties. We calculate the frequency dependent optical conductivity in systems with both Rashba and Dresselhaus spin-orbit coupling. We find that when the linear Dresselhaus spin-orbit coupling is tuned to be equal to the Rashba spin-orbit coupling, the interband optical conductivity disappears. This is taken to be the signature of the recovery of SU(2) symmetry. The presence of the cubic Dresselhaus spin-orbit coupling modifies the dispersion relation of the charge carriers and the velocity operator. Thus the conductivity is modified, but the interband contribution remains suppressed at most but not all photon energies for a cubic coupling of reasonable magnitude. Hence, such a measurement can serve as a diagnostic probe of engineered spin-orbit coupling.",1310.3916v1 2013-11-15,Enhancing optomechanical coupling via the Josephson effect,"Cavity optomechanics is showing promise for studying quantum mechanics in large systems. However, smallness of the radiation-pressure coupling is a serious hindrance. Here we show how the charge tuning of the Josephson inductance in a single-Cooper-pair transistor (SCPT) can be exploited to arrange a strong radiation pressure -type coupling $g_0$ between mechanical and microwave resonators. In a certain limit of parameters, such a coupling can also be seen as a qubit-mediated coupling of two resonators. We show that this scheme allows reaching extremely high $g_0$. Contrary to the recent proposals for exploiting the non-linearity of a large radiation pressure coupling, the main non-linearity in this setup originates from a cross-Kerr type of coupling between the resonators, where the cavity refractive index depends on the phonon number. The presence of this coupling will allow accessing the individual phonon numbers via the measurement of the cavity.",1311.3802v2 2013-12-10,Rashba spin orbit coupling in the Kane-Mele-Hubbard model,"Spin-orbit (SO) coupling is the crucial parameter to drive topological insulating phases in electronic band models. In particular, the generic emergence of SO coupling involves the Rashba term which fully breaks the SU(2) spin symmetry. As soon as interactions are taken into account, however, many theoretical studies have to content themselves with the analysis of a simplified U(1) conserving SO term without Rashba coupling. We intend to fill this gap by studying the Kane-Mele-Hubbard (KMH) model in the presence of Rashba SO coupling and present the first systematic analysis of the effect of Rashba SO coupling in a correlated two-dimensional topological insulator. We apply the variational cluster approach (VCA) to determine the interacting phase diagram by computing local density of states, magnetization, single particle spectral function, and edge states. Preceded by a detailed VCA analysis of the KMH model in the presence of U(1) conserving SO coupling, we find that the additional Rashba SO coupling drives new electronic phases such as a metallic regime and a direct-gap only topological insulating phase which persist in the presence of interactions.",1312.2934v2 2014-01-02,Radiative corrections to the Yukawa coupling constants in two Higgs doublet models,"We calculate one-loop corrected Yukawa coupling constants $hf\bar{f}$ for the standard model like Higgs boson $h$ in two Higgs doublet models. We focus on the models with the softly-broken $Z_2$ symmetry, which is imposed to avoid the flavor changing neutral current. Under the $Z_2$ symmetry, there are four types of Yukawa interactions. We find that one-loop contributions from extra Higgs bosons modify the $hf\bar{f}$ couplings to be maximally about $5\%$ under the constraint from perturbative unitarity and vacuum stability. Our results show that the pattern of tree-level deviations by the mixing effect in each type of Yukawa couplings from the SM predictions does not change even including radiative corrections. Moreover, when the gauge couplings $hVV$ ($V=W,Z$) are found to be slightly (with a percent level) differ from the SM predictions, the $hf\bar{f}$ couplings also deviate but more largely. Therefore, in such a case, not only can we determine the type of Yukawa couplings but also we can obtain information on the extra Higgs bosons by comparing the predictions with precisely measured $hf\bar{f}$ and $hVV$ couplings at future electron-positron colliders.",1401.0515v2 2014-02-13,Resonance in Magnetostatically Coupled Transverse Domain Walls,"We have observed the eigenmodes of coupled transverse domain walls in a pair of ferromagnetic nanowires. Although the pair is coupled magnetostatically, its spectrum is determined by a combination of pinning by edge roughness and dipolar coupling of the two walls. Because the corresponding energy scales are comparable, the coupling can be observed only at the smallest wire separations. A model of the coupled wall dynamics reproduces the experiment quantitatively, allowing for comparisons with the estimated pinning and domain wall coupling energies. The results have significant implications for the dynamics of devices based on coupled domain walls.",1402.3202v2 2014-04-16,Spatial Coherence Properties of Organic Molecules Coupled to Plasmonic Surface Lattice Resonances in the Weak and Strong Coupling Regimes,"We study spatial coherence properties of a system composed of periodic silver nanoparticle arrays covered with a fluorescent organic molecule (DiD) film. The evolution of spatial coherence of this composite structure from the weak to the strong coupling regime is investigated by systematically varying the coupling strength between the localized DiD excitons and the collective, delocalized modes of the nanoparticle array known as surface lattice resonances. A gradual evolution of coherence from the weak to the strong coupling regime is observed, with the strong coupling features clearly visible in interference fringes. A high degree of spatial coherence is demonstrated in the strong coupling regime, even when the mode is very excitonlike (80%), in contrast to the purely localized nature of molecular excitons. We show that coherence appears in proportion to the weight of the plasmonic component of the mode throughout the weak-to-strong coupling crossover, providing evidence for the hybrid nature of the normal modes.",1404.4160v1 2014-07-22,Explanation of Lithosphere-Atmosphere-Ionosphere Coupling System Anomalous Geophysical Phenomena on the Basis of the Model of Generation of Electromagnetic Emission Detected Before Earthquake,Lithosphere-Atmosphere-Ionosphere Coupling System,1407.5979v1 2014-09-01,Stochastic switching in delay-coupled oscillators,"A delay is known to induce multistability in periodic systems. Under influence of noise, coupled oscillators can switch between coexistent orbits with different frequencies and different oscillation patterns. For coupled phase oscillators we reduce the delay system to a non-delayed Langevin equation, which allows us to analytically compute the distribution of frequencies, and their corresponding residence times. The number of stable periodic orbits scales with the roundtrip delay time and coupling strength, but the noisy system visits only a fraction of the orbits, which scales with the square root of the delay time and is independent of the coupling strength. In contrast, the residence time in the different orbits is mainly determined by the coupling strength and the number of oscillators, and only weakly dependent on the coupling delay. Finally we investigate the effect of a detuning between the oscillators. We demonstrate the generality of our results with delay-coupled FitzHugh-Nagumo oscillators.",1409.0479v1 2014-09-03,Transitions among the diverse oscillation quenching states induced by the interplay of direct and indirect coupling,"We report the transitions among different oscillation quenching states induced by the interplay of diffusive (direct) coupling and environmental (indirect) coupling in coupled identical oscillators. This coupling scheme was introduced by Resmi {\it et al}. [Phys. Rev. E, 84, 046212 (2011)] as a general scheme to induce amplitude death (AD) in nonlinear oscillators. Using a detailed bifurcation analysis we show that in addition to AD, which actually occurs only in a small region of parameter space, this coupling scheme can induce other oscillation quenching states, namely oscillation death (OD) and a novel nontrvial AD (NAD) state, which is a nonzero {\it bistable} homogeneous steady state; more importantly, this coupling mediates a transition from AD to OD state and a new transition from AD to NAD state. We identify diverse routes to the NAD state and map all the transition scenarios in the parameter space for periodic oscillators. Finally, we present the first experimental evidence of oscillation quenching states and their transitions induced by the interplay of direct and indirect coupling.",1409.1063v3 2014-11-12,Fermi Gases with Synthetic Spin-Orbit Coupling,"We briefly review recent progress on ultracold atomic Fermi gases with different types of synthetic spin-orbit coupling, including the one-dimensional (1D) equal weight Rashba-Dresselhaus and two-dimensional (2D) Rasbha spin-orbit couplings. Theoretically, we show how the single-body, two-body and many-body properties of Fermi gases are dramatically changed by spin-orbit coupling. In particular, the interplay between spin-orbit coupling and interatomic interaction may lead to several long-sought exotic superfluid phases at low temperatures, such as anisotropic superfluid, topological superfluid and inhomogeneous superfluid. Experimentally, only the first type - equal weight combination of Rasbha and Dresselhaus spin-orbit couplings - has been realized very recently using a two-photon Raman process. We show how to characterize a normal spin-orbit coupled atomic Fermi gas in both non-interacting and strongly-interacting limits, using particularly momentum-resolved radio-frequency spectroscopy. The experimental demonstration of a strongly-interacting spin-orbit coupled Fermi gas opens a promising way to observe various exotic superfluid phases in the near future.",1411.3043v1 2014-11-27,Efimov physics and universal trimer in spin-orbit coupled ultracold atomic mixtures,"We study the two-body and three-body bound states in ultracold atomic mixtures with one of the atoms subjected to an isotropic spin-orbit (SO) coupling. We consider a system of two identical fermions interacting with one SO coupled atom. It is found that there can exist two types of three-body bound states, Efimov trimers and universal trimers. The Efimov trimers are energetically less favored by the SO coupling, which will finally merge into the atom-dimer threshold as increasing the SO coupling strength. Nevertheless, these trimers exhibit a new kind of discrete scaling law incorporating the SO coupling effect. On the other hand, the universal trimers are more favored by the SO coupling. They can be induced at negative s-wave scattering lengths and with smaller mass ratios than those without SO coupling. These results are obtained by both the Born-Oppenheimer approximation and exact solutions from three-body equations.",1411.7488v1 2014-11-28,Amplitude-phase coupling drives chimera states in globally coupled laser networks,"For a globally coupled network of semiconductor lasers with delayed optical feedback, we demonstrate the existence of chimera states. The domains of coherence and incoherence that are typical for chimera states are found to exist for the amplitude, phase, and inversion of the coupled lasers. These chimera states defy several of the previously established existence criteria. While chimera states in phase oscillators generally demand nonlocal coupling, large system sizes, and specially prepared initial conditions, we find chimera states that are stable for global coupling in a network of only four coupled lasers for random initial conditions. The existence is linked to a regime of multistability between the synchronous steady state and asynchronous periodic solutions. We show that amplitude-phase coupling, a concept common in different fields, is necessary for the formation of the chimera states.",1412.0957v1 2014-12-15,Nonlinear optomechanical paddle nanocavities,"Nonlinear optomechanical coupling is the basis for many potential future experiments in quantum optomechanics (e.g., quantum non-demolition measurements, preparation of non-classical states), which to date have been difficult to realize due to small non-linearity in typical optomechanical devices. Here we introduce an optomechanical system combining strong nonlinear optomechanical coupling, low mass and large optical mode spacing. This nanoscale ""paddle nanocavity"" supports mechanical resonances with hundreds of fg mass which couple nonlinearly to optical modes with a quadratic optomechanical coupling coefficient $g^{(2)} > 2\pi\times400$ MHz/nm$^2$, and a two phonon to single photon optomechanical coupling rate $\Delta \omega_0 > 2\pi\times 16$ Hz. This coupling relies on strong phonon-photon interactions in a structure whose optical mode spectrum is highly non--degenerate. Nonlinear optomechanical readout of thermally driven motion in these devices should be observable for T $> 50 $ mK, and measurement of phonon shot noise is achievable. This shows that strong nonlinear effects can be realized without relying on coupling between nearly degenerate optical modes, thus avoiding parasitic linear coupling present in two mode systems.",1412.4431v2 2015-01-27,The Holographic Dictionary for Beta Functions of Multi-trace Coupling Constants,"Field theories with weakly coupled holographic duals, such as large N gauge theories, have a natural separation of their operators into `single-trace operators' (dual to single-particle states) and `multi-trace operators' (dual to multi-particle states). There are examples of large N gauge theories where the beta functions of single-trace coupling constants all vanish, but marginal multi-trace coupling constants have non-vanishing beta functions that spoil conformal invariance (even when all multi-trace coupling constants vanish). The holographic dual of such theories should be a classical solution in anti-de Sitter space, in which the boundary conditions that correspond to the multi-trace coupling constants depend on the cutoff scale, in a way that spoils conformal invariance. We argue that this is realized through specific bulk coupling constants that lead to a running of the multi-trace coupling constants. This fills a missing entry in the holographic dictionary.",1501.06664v3 2015-03-18,Effect of broadening in the weak coupling limit of vibrationally coupled electron transport through molecular junctions and the analogy to quantum dot circuit QED systems,"We investigate the nonequilibrium population of a vibrational mode in the steady state of a biased molecular junction, using a rate equation approach. We focus on the limit of weak electronic-vibrational coupling and show that, in the resonant transport regime and for sufficiently high bias voltages, the level of vibrational excitation increases with decreasing coupling strength, assuming a finite and non-zero value. An analytic behavior with respect to the electronic-vibrational coupling strength is only observed if the influence of environmental degrees of freedom is explicitly taken into account. We consider the influence of three different types of broadening: hybridization with the electrodes, thermal fluctuations and the coupling to a thermal heat bath. Our results apply to vibrationally coupled electron transport through molecular junctions but also to quantum dots coupled to a microwave cavity, where the photon number can be expected to exhibit a similar behavior.",1503.05574v2 2015-04-29,Dynamics of two externally driven coupled quantum oscillators interacting with separate baths based on path integrals,"The paper deals with the problem of dynamics of externally driven open quantum systems. Using the path integral methods we found an analytical expression for time-dependent density matrix of two externally driven coupled quantum oscillators interacting with different baths of oscillators. It is shown that at the zeroing of external forces the density matrix becomes identical to the previously obtained one for freely developing coupled oscillators. Mean values of observables are computed by using the Hermitian part of the matrix. All elements of the covariance matrix composed by coordinates and momenta of two driven coupled oscillators are calculated. The time-dependent mean values, dispersions and covariances of coordinates of coupled oscillators at given external forces are numerically studied. It is shown that the larger the coupling constant the larger is the disturbances of the second oscillator due to external action on the first oscillator. Coupled dynamics of forced oscillators at relatively large coupling constant is demonstrated at different thermodynamic conditions.",1504.07975v1 2015-05-24,On defocusing coupled nonlinear Schrodinger equations,"The initial value problem for some defocusing coupled nonlinear Schrodinger equations is investigated. Global well-posedness and scattering are established.",1505.07059v1 2015-06-10,Cavity-induced modifications of molecular structure in the strong coupling regime,"In most theoretical descriptions of collective strong coupling of organic molecules to a cavity mode, the molecules are modeled as simple two-level systems. This picture fails to describe the rich structure provided by their internal rovibrational (nuclear) degrees of freedom. We investigate a first-principles model that fully takes into account both electronic and nuclear degrees of freedom, allowing an exploration of the phenomenon of strong coupling from an entirely new perspective. First, we demonstrate the limitations of applicability of the Born-Oppenheimer approximation in strongly coupled molecule-cavity structures. For the case of two molecules, we also show how dark states, which within the two-level picture are effectively decoupled from the cavity, are indeed affected by the formation of collective strong coupling. Finally, we discuss ground-state modifications in the ultra-strong coupling regime and show that some molecular observables are affected by the collective coupling strength, while others only depend on the single-molecule coupling constant.",1506.03331v1 2015-06-13,General coupled mode theory in non-Hermitian waveguides,"In the presence of loss and gain, the coupled mode equation on describing the mode hybridization of various waveguides or cavities, or cavities coupled to waveguides becomes intrinsically non-Hermitian. In such non-Hermitian waveguides, the standard coupled coupled mode theory fails. We generalize the coupled mode theory with a properly defined inner product based on reaction conservation. We apply our theory to the non-Hermitian parity-time symmetric waveguides, and obtain excellent agreement with results obtained by finite element fullwave simulations. The theory presented here is typically formulated in space to study coupling between waveguides, which can be transformed into time domain by proper reformulation to study coupling between non-Hermitian resonators. Our theory has the strength of studying non-Hermitian optical systems with inclusion of the full vector fields, thus is useful to study and design non-Hermitian devices that support asymmetric and even nonreciprocal light propagations",1506.04224v3 2015-06-13,Circuit electromechanics with single photon strong coupling,"In circuit electromechanics, the coupling strength is usually very small. Here, replacing the capacitor in circuit electromechanics by a superconducting flux qubit, we show that the coupling among the qubit and the two resonators can induce effective electromechanical coupling which can attain the strong coupling regime at the single photon level with feasible experimental parameters. We use dispersive couplings among two resonators and the qubit while the qubit is also driven by an external classical field. These couplings form a three-wave mixing configuration among the three elements where the qubit degree of freedom can be adiabatically eliminated, and thus results in the enhanced coupling between the two resonators. Therefore, our work constitutes the first step towards studying quantum nonlinear effect in circuit electromechanics.",1506.04247v2 2015-06-16,Coupling the Kolmogorov Diffusion: maximality and efficiency considerations,"This is a case study concerning the rate at which probabilistic coupling occurs for nilpotent diffusions. We focus on the simplest case of Kolmogorov diffusion (Brownian motion together with its time integral, or, slightly more generally, together with a finite number of iterated time integrals). In this case there can be no Markovian maximal coupling. Indeed, Markovian couplings cannot even be efficient (extending the terminology of Burdzy and Kendall, Efficient Markovian couplings: examples and counterexamples; Annals of Applied Probability, 2000). Finally, at least in the classical case of a single time integral, it is not possible to choose a Markovian coupling that is optimal in the sense of simultaneously minimizing the probability of failing to couple by time t for all positive t. In recompense for all these negative results, we exhibit a simple efficient non-Markovian coupling.",1506.04804v3 2015-06-30,Scalar - Tensor gravity with scalar -matter direct coupling and its cosmological probe,"SNIA and CMB datasets have shown both of evolving Newton's ""constant"" and a signature of the coupling of scalar field to matter. These observations motivate the consideration of the scalar-matter coupling in Jordan frame in the framework of scalar-tensor gravity. So far, majority of the works on the coupling of scalar matter has performed in Einstein frame in the framework of minimally coupled scalar fields. In this work, we generalize the original scalar-tensor theories of gravity introducing a direct coupling of scalar to matter in the Jordan frame. The combined consideration of both evolving Newton's constant and scalar-matter coupling using the recent observation datasets, shows features different from the previous works. The analysis shows a vivid signature of the scalar-matter coupling. The variation rate of the Newton's constant is obtained rather greater than that determined in the previous works.",1506.09121v1 2015-11-12,Strong exciton-plasmon coupling in MoS2 coupled with plasmonic lattice,"We demonstrate strong exciton-plasmon coupling in silver nanodisk arrays integrated with monolayer MoS2 via angle-resolved reflectance microscopy spectra of the coupled system. Strong exciton-plasmon coupling is observed with the exciton-plasmon coupling strength up to 58 meV at 77 K, which also survives at room temperature. The strong coupling involves three types of resonances: MoS2 excitons, localized surface plasmon resonances (LSPRs) of individual silver nanodisks and plasmonic lattice resonances of the nanodisk array. We show that the exciton-plasmon coupling strength, polariton composition and dispersion can be effectively engineered by tuning the geometry of the plasmonic lattice, which makes the system promising for realizing novel two-dimensional plasmonic polaritonic devices.",1511.03750v1 2016-04-04,Hindered magnetic dipole transitions between P-wave bottomonia and coupled-channel effects,"In the hindered magnetic dipole transitions of heavy quarkonia, the coupled-channel effects originating from the coupling of quarkonia to a pair of heavy and anti-heavy mesons can play a dominant role. Here, we study the hindered magnetic dipole transitions between two $P$-wave bottomonia, $\chi_b(n P)$ and $h_b(n^\prime P)$, with $n\neq n^\prime$. In these processes the coupled-channel effects are expected to lead to partial widths much larger than the quark model predictions. We estimate these partial widths which, however, are very sensitive to unknown coupling constants related to the vertices $\chi_{b0}(nP)B\bar B$. A measurement of the hindered M1 transitions can shed light on the coupled-channel dynamics in these transitions and hence on the size of the coupling constants. We also suggest to check the coupled-channel effects by comparing results from quenched and fully dynamical lattice QCD calculations.",1604.00770v2 2016-04-27,Transition from homogeneous to inhomogeneous steady states in oscillators under cyclic coupling,"We report a transition from homogeneous steady state to inhomogeneous steady state in coupled oscillators, both limit cycle and chaotic, under cyclic coupling and diffusive coupling as well when an asymmetry is introduced in terms of a negative parameter mismatch. Such a transition appears in limit cycle systems via pitchfork bifurcation as usual. Especially, when we focus on chaotic systems, the transition follows a transcritical bifurcation for cyclic coupling while it is a pitchfork bifurcation for the conventional diffusive coupling. We use the paradigmatic Van der Pol oscillator as the limit cycle system and a Sprott system as a chaotic system. We verified our results analytically for cyclic coupling and numerically check all results including diffusive coupling for both the limit cycle and chaotic systems.",1604.07943v1 2016-06-01,Pure plate bending in couple stress theories,"In this paper, we examine the pure bending of plates within the framework of modified couple stress theory (M-CST) and consistent couple stress theory (C-CST). In this development, it is demonstrated that M-CST does not describe pure bending of a plate properly. Particularly, M-CST predicts no couple-stresses and no size effect for the pure bending of the plate into a spherical shell. This contradicts our expectation that couple stress theory should predict some size effect for such a deformation pattern. Therefore, this result clearly demonstrates another inconsistency of indeterminate symmetric modified couple stress theory (M-CST), which is based on considering the symmetric torsion tensor as the curvature tensor. On the other hand, the fully determinate skew-symmetric consistent couple stress theory (C-CST) predicts results for pure plate bending that tend to agree with mechanics intuition and experimental evidence. Particularly, C-CST predicts couple-stresses and size effects for the pure bending of the plate into a spherical shell, which represents an additional illustration of its consistency.",1606.02954v1 2016-06-16,Energy Conservation and Coupling Error Reduction in Non-Iterative Co-Simulations,"When simulators are energetically coupled in a co-simulation, residual energies alter the total energy of the full coupled system. This distorts the system dynamics, lowers the quality of the results, and can lead to instability. By using power bonds to realize simulator coupling, the Energy-Conservation-based Co-Simulation method (ECCO) [Sadjina et al. 2016] exploits these concepts to define non-iterative global error estimation and adaptive step size control relying on coupling variable data alone. Following similar argumentation, the Nearly Energy Preserving Coupling Element (NEPCE) [Benedikt et al. 2013] uses corrections to the simulator inputs to approximately ensure energy conservation. Here, we discuss a modification to NEPCE for when direct feed-through is present in one of the coupled simulators. We further demonstrate how accuracy and efficiency in non-iterative co-simulations are substantially enhanced when combining NEPCE with ECCO's adaptive step size controller. A quarter car model with linear and nonlinear damping characteristics serves as a co-simulation benchmark, and we observe reductions of the coupling errors of up to 98% utilizing the concepts discussed here.",1606.05168v1 2016-07-01,Dynamical strong coupling and parametric amplification in mechanical modes of graphene drums,"Mechanical resonators are ubiquitous in modern information technology. With the ability to couple them to electromagnetic and plasmonic modes, they hold the promise to be the key building blocks in future quantum information technology. Graphene based resonators are of interest for technological applications due to their high resonant frequencies, multiple mechanical modes, and low mass. The tension mediated non-linear coupling between various modes of the resonator can be excited in a controllable manner. Here, we engineer a graphene resonator to have large frequency tunability at low temperatures resulting in large intermodal coupling strength. We observe the emergence of new eigenmodes and amplification of the coupled modes using red and blue parametric excitation respectively. We demonstrate that the dynamical intermodal coupling is tunable. A cooperativity of 60 between two resonant modes of ~100 MHz is achieved in the strong coupling regime. The ability to dynamically control the coupling between high frequency eigenmodes of a mechanical system opens up possibility for quantum mechanical experiments at low temperatures.",1607.00229v1 2017-02-28,Linking Magnon-Cavity Strong Coupling to Magnon-Polaritons through Effective Permeability,"Strong coupling in cavity-magnon systems has shown great potential for use in spintronics and information processing technologies due to the low damping rates and long coherence times. Although such systems are conceptually similar to those coupled by magnon-polaritons (MPs), the link between magnon-cavity coupling and MPs has not been explicitly defined. In this work we establish such a connection by studying the frequency-wavevector dispersion of a strongly coupled magnon-cavity system, using a height-adjustable microwave cavity, and by modelling the observed behaviour through the system's effective permeability. A polariton gap between the upper and lower coupled modes of the magnon-cavity system is defined, and is seen to be dependent on the system's effective filling factor. This gap is equal to the MP polariton gap in the limit where filling factor = 1, corresponding to the removal of the microwave cavity. Thus, our work clarifies the connection between magnon-cavity and MP coupling, improving our understanding of magnon-photon interactions in coupled systems.",1703.00074v1 2017-03-04,"Interpolated energy densities, correlation indicators and lower bounds from approximations to the strong coupling limit of DFT","We investigate the construction of approximated exchange-correlation functionals by interpolating locally along the adiabatic connection between the weak- and the strong-coupling regimes, focussing on the effect of using approximate functionals for the strong-coupling energy densities. The gauge problem is avoided by dealing with quantities that are all locally defined in the same way. Using exact ingredients at weak coupling we are able to isolate the error coming from the approximations at strong coupling only. We find that the nonlocal radius model, which retains some of the non-locality of the exact strong-coupling regime, yields very satisfactory results. We also use interpolation models and quantities from the weak- and strong-coupling regimes to define a correlation-type indicator and a lower bound to the exact exchange-correlation energy. Open problems, related to the nature of the local and global slope of the adiabatic connection at weak coupling, are also discussed.",1703.01456v1 2017-03-08,Controlling of blow-up responses by a nonlinear $\cal{PT}$ symmetric coupling,"We investigate the dynamics of a coupled waveguide system with competing linear and nonlinear loss-gain profiles which can facilitate power saturation. We show the usefulness of the model in achieving unidirectional beam propagation. In this regard, the considered type of coupled waveguide system has two drawbacks, (i) difficulty in achieving perfect isolation of light in a waveguide and (ii) existence of blow-up type behavior for certain input power situations. We here show a nonlinear $\cal{PT}$ symmetric coupling that helps to overcome these two drawbacks. Such a nonlinear coupling has close connection with the phenomenon of stimulated Raman scattering. In particular, we have elucidated the role of this nonlinear coupling using an integrable $\cal{PT}$ symmetric situation. In particular, using the integrals of motion, we have reduced this coupled waveguide problem to the problem of dynamics of a particle in a potential. With the latter picture, we have clearly illustrated the role of the considered nonlinear coupling. The above $\cal{PT}$ symmetric case corresponds to a limiting form of a general equation describing the phenomenon of stimulated Raman scattering. We also point out the ability to transport light unidirectionally even in this general case.",1703.02752v1 2018-02-26,Cavity quantum-electrodynamical polaritonically enhanced electron-phonon coupling and its influence on superconductivity,"Laser control of solids was so far mainly discussed in the context of strong classical nonlinear light-matter coupling in a pump-probe framework. Here we propose a quantum-electrodynamical setting to address the coupling of a low-dimensional quantum material to quantized electromagnetic fields in quantum cavities. Using a protoypical model system describing FeSe/SrTiO$_3$ with electron-phonon long-range forward scattering, we study how the formation of phonon polaritons at the 2D interface of the material modifies effective couplings and superconducting properties in a Migdal-Eliashberg simulation. We find that through highly polarizable dipolar phonons, large cavity-enhanced electron-phonon couplings are possible but superconductivity is not enhanced for the forward-scattering pairing mechanism due to the interplay between coupling enhancement and mode softening. An analysis of critical temperature dependencies on couplings and mode frequencies suggests that that cavity-enhanced superconductivity is possible for more conventional short-range pairing mechanisms. Our results demonstrate that quantum cavities enable the engineering of fundamental couplings in solids paving the way to unprecedented control of material properties.",1802.09437v2 2018-04-11,Novel matter coupling in general relativity via canonical transformation,"We study canonical transformations of general relativity (GR) to provide a novel matter coupling to gravity. Although the transformed theory is equivalent to GR in vacuum, the equivalence no longer holds if a matter field minimally couples to the canonically transformed gravitational field. We find that a naive matter coupling to the transformed field leads to the appearance of an extra mode in the phase space, rendering the theory inconsistent. We then find a consistent and novel way of matter coupling: after imposing a gauge fixing condition, a matter field can minimally couple to gravity without generating an unwanted extra mode. As a result, the way matter field couples to the gravitational field determines the preferred time direction and the resultant theory has only two gravitational degrees of freedom. We also discuss the cosmological solution and linear perturbations around it, and confirm that their dynamics indeed differ from those in GR. The novel matter coupling can be used for a new framework of modified gravity theories.",1804.03902v2 2018-11-13,Stability enhancement by induced synchronization using transient uncoupling in certain coupled chaotic systems,"In this work, we report the enhanced stability of induced synchronization observed through transient uncoupling in a class of unidirectionally coupled identical chaotic systems. The phenomenon of transient uncoupling implies the clipping of the chaotic attractor of the driven system in a drive-driven scenario and making the coupling strength active over the clipped regions. The {\emph{Master Stability Function}} (MSF) is used to determine the stability of the synchronized states for a finite clipping fraction in unidirectionally coupled chaotic systems subjected to transient uncoupling for fixed values of coupling strength. The effectiveness of transient uncoupling is observed through the existence of negative regions in the MSF spectrum for larger values of coupling strength. Further the two-parameter bifurcation diagram indicating the regions of stable synchronization for different values of clipping fraction and coupling strength has been obtained. The effect of the symmetry of chaotic attractors in enhancing the stability of synchronized states of coupled chaotic systems subjected to transient uncoupling is studied.",1811.05091v1 2010-05-18,Coupled Fixed Point Theorems for Contraction Involving Rational Expressions in Partially Ordered Metric Spaces,"We establish coupled fixed point theorems for contraction involving rational expressions in partially ordered metric spaces.",1005.3142v1 2014-03-18,Optomechanical-like coupling between superconducting resonators,"We propose and analyze a circuit that implements a nonlinear coupling between two superconducting microwave resonators. The resonators are coupled through a superconducting quantum interference device (SQUID) that terminates one of the resonators. This produces a nonlinear interaction on the standard optomechanical form, where the quadrature of one resonator couples to the photon number of the other resonator. The circuit therefore allows for all-electrical realizations of analogs to optomechanical systems, with coupling that can be both strong and tunable. We estimate the coupling strengths that should be attainable with the proposed device, and we find that the device is a promising candidate for realizing the single-photon strong-coupling regime. As a potential application, we discuss implementations of networks of nonlinearly-coupled microwave resonators, which could be used in microwave-photon based quantum simulation.",1403.4341v1 2017-01-25,Suppression and Revival of Oscillations through Time-varying Interaction,"We explore the dynamical consequences of switching the coupling form in a system of coupled oscillators. We consider two types of switching, one where the coupling function changes periodically and one where it changes probabilistically. We find, through bifurcation diagrams and Basin Stability analysis, that there exists a window in coupling strength where the oscillations get suppressed. Beyond this window, the oscillations are revived again. A similar trend emerges with respect to the relative predominance of the coupling forms, with the largest window of fixed point dynamics arising where there is balance in the probability of occurrence of the coupling forms. Further, significantly, more rapid switching of coupling forms yields large regions of oscillation suppression. Lastly, we propose an effective model for the dynamics arising from switched coupling forms and demonstrate how this model captures the basic features observed in numerical simulations and also offers an accurate estimate of the fixed point region through linear stability analysis.",1701.07314v1 2017-01-31,Tunable magnon-photon coupling in a compensating ferrimagnet - from weak to strong coupling,"We experimentally study the magnon-photon coupling in a system consitsing of the compensating ferrimagnet gadolinium iron garnet (GdIG) and a three-dimensional microwave cavity. The temperature is varied in order to tune the GdIG magnetization and to observe the transition from the weak coupling regime to the strong coupling regime. By measuring and modelling the complex reflection parameter of the system the effective coupling rate g eff and the magnetization M eff of the sample are extracted. Comparing g eff with the magnon and the cavity decay rate we conclude that the strong coupling regime is easily accessible using GdIG. We show that the effective coupling strength follows the predicted square root dependence on the magnetization.",1701.08969v3 2018-05-08,Disorder effects on the coupling strength of coupled photonic crystal slab cavities,"We study the effects of disorder on the coupling strength of coupled photonic crystal slab cavities by considering fully-3D electromagnetic calculations. Specifically, we investigate two coupled L3 cavities at 30{\deg} and 60{\deg} configurations, where the coupling strength J (or photon hopping) is extracted from the simulations in the presence of disorder. We found that the relative fluctuations of the photon hopping are more sensitive to disorder effects than the corresponding fluctuations in the eigenfrequencies of the coupled cavities. Furthermore, for the typical range of disorder in state-of-the-art devices, the J fluctuations are found to increase linearly as a function of the disorder amplitude. This allows to set upper bounds to the amplitude of fabrication imperfections, for which the coupling predicted by design can still be expected, on average, in a fabricated device.",1805.03012v1 2018-05-09,Exact explosive synchronization transitions in Kuramoto oscillators with time-delayed coupling,"Synchronization commonly occurs in many natural and man-made systems, from neurons in the brain to cardiac cells to power grids to Josephson junction arrays. Transitions to or out of synchrony for coupled oscillators depend on several factors, such as individual frequencies, coupling, interaction time delays and network structure-function relation. Here, using a generalized Kuramoto model of time-delay coupled phase oscillators with frequency-weighted coupling, we study the stability of incoherent and coherent states and the transitions to or out of explosive (abrupt, first-order like) phase synchronization. We analytically derive the exact formulas for the critical coupling strengths at different time delays in both directions of increasing (forward) and decreasing (backward) coupling strengths. We find that time-delay does not affect the transition for the backward direction but shifts the transition for the forward direction of increasing coupling strength. These results provide valuable insights into our understanding of dynamical mechanisms for explosive synchronization in presence of often unavoidable time delays present in many physical and biological systems.",1805.03510v1 2018-05-10,Synchrony and Anti-Synchrony for Difference-Coupled Vector Fields on Graph Network Systems,"We define a graph network to be a coupled cell network where there are only one type of cell and one type of symmetric coupling between the cells. For a difference-coupled vector field on a graph network system, all the cells have the same internal dynamics, and the coupling between cells is identical, symmetric, and depends only on the difference of the states of the interacting cells. We define four nested sets of difference-coupled vector fields by adding further restrictions on the internal dynamics and the coupling functions. These restrictions require that these functions preserve zero or are odd or linear. We characterize the synchrony and anti-synchrony subspaces with respect to these four subsets of admissible vector fields. Synchrony and anti-synchrony subspaces are determined by partitions and matched partitions of the cells that satisfy certain balance conditions. We compute the lattice of synchrony and anti-synchrony subspaces for several graph networks. We also apply our theory to systems of coupled van der Pol oscillators.",1805.04144v2 2009-12-16,Phase locking of coupled lasers with many longitudinal modes,"Detailed experimental and theoretical investigations on two coupled fiber lasers, each with many longitudinal modes, reveal that the behavior of the longitudinal modes depends on both the coupling strength as well as the detuning between them. For low to moderate coupling strength only longitudinal modes which are common for both lasers phase-lock while those that are not common gradually disappear. For larger coupling strengths, the longitudinal modes that are not common reappear and phase-lock. When the coupling strength approaches unity the coupled lasers behave as a single long cavity with correspondingly denser longitudinal modes. Finally, we show that the gradual increase in phase-locking as a function of the coupling strength results from competition between phase-locked and non phase-locked longitudinal modes.",0912.3235v1 2013-09-04,"Excitons in quantum dot molecules: Coulomb coupling, spin-orbit effects and phonon-induced line broadening","Excitonic states and the line shape of optical transitions in coupled quantum dots (quantum dot molecules) are studied theoretically. For a pair of electrically tunable, vertically aligned quantum dots we investigate the coupling between spatially direct and indirect excitons caused by different mechanisms such as tunnel coupling, Coulomb coupling, coupling due to the spin-orbit interaction and coupling induced by a structural asymmetry. The peculiarities of the different types of couplings are reflected in the appearance of either crossings or avoided crossings between direct and indirect excitons, the latter ones being directly visible in the absorption spectrum. We analyze the influence of the phonon environment on the spectrum by calculating the line shape of the various optical transitions including contributions due to both pure dephasing and phonon-induced transitions between different exciton states. The line width enhancement due to phonon-induced transitions is particularly pronounced in the region of an anticrossing and it strongly depends on the energy splitting between the two exciton branches.",1309.1032v2 2013-09-10,Stable numerical coupling of exterior and interior problems for the wave equation,"Stable numerical coupling of exterior and interior problems for the wave equation",1309.2649v1 2013-09-12,Tunable power law in the desynchronization events of coupled chaotic electronic circuits,"We study the statistics of the amplitude of the synchronization error in chaotic electronic circuits coupled through linear feedback. Depending on the coupling strength, our system exhibits three qualitatively different regimes of synchronization: weak coupling yields independent oscillations; moderate to strong coupling produces a regime of intermittent synchronization known as attractor bubbling; and stronger coupling produces complete synchronization. In the regime of moderate coupling, the probability distribution for the sizes of desynchronization events follows a power law, with an exponent that can be adjusted by changing the coupling strength. Such power-law distributions are interesting, as they appear in many complex systems. However, most of the systems with such a behavior have a fixed value for the exponent of the power law, while here we present an example of a system where the exponent of the power law is easily tuned in real time.",1309.3240v1 2016-05-05,Constraints from growth-rate data on some coupled dark energy models mimicking a $ΛCDM$ expansion,"The $\Lambda CDM$ expansion could be mimicked by a dark energy coupled to matter. Then, the equation of state $\bar w$ and coupling $\bar Q$ of this coupled dark energy could not be constrained by observations of the Hubble function alone. Also, in this paper, we determine the constraints on two such coupled dark energy models considering some current and forecast Euclid-like growth-rate data and assuming the prior on the $\Lambda CDM$ dark matter density parameter today $\Omega_{m0}=0.295\pm 0.04$. The first model is defined by a constant equation of state. We find that at $2\sigma$, $\bar w=-1.02_{-0.22}^{+0.06}$ and the coupling function $\bar Q_0$ today is $\bar Q_0H_0^{-3}=0.057_{-0.148}^{+0.353}$ with $H_0$ the Hubble constant. The second model is defined by a varying equation of state $\bar w=\bar w_a-\bar w_b\ln(1+z)$, with $z$ the redshift and $(\bar w_a,\bar w_b)$, two constants. We find that at $2\sigma$, $\bar w_a=-0.99_{-0.90}^{+0.17}$, $\bar w_b=-0.04_{-1.17}^{+0.31}$ and $\bar Q_0H_0^{-3}=0.0002_{-0.18}^{+1.35}$. These constraints on coupled dark energy agreed with a $\Lambda CDM$ model but are too poor to discard confidently a coupled dark energy different from vacuum but mimicking a $\Lambda CDM$ expansion.",1605.01644v1 2016-05-30,Sign-Reversal Coupling in Coupled-Resonator Optical Waveguide,"Coupled-resonator optical waveguides (CROWs), which play a significant role in modern photonics, achieve waveguiding through near-field coupling between tightly localized resonators. The coupling factor, a critical parameter in CROW theory, determines the coupling strength between two resonators and the waveguiding dispersion of a CROW. However, the original CROW theory proposed by Yariv et al. only demonstrated one value of coupling factor for a multipole resonance mode. Here, by imaging the tight-binding Bloch waves on a CROW consisting of designer-surface-plasmon resonators in the microwave regime, we demonstrate that the coupling factor in the CROW theory can reverse its sign for a multipole resonance mode. This determines two different waveguiding dispersion curves in the same frequency range, experimentally confirmed by matching Bloch wavevectors and frequencies in the CROW. Our study supplements and extends the original CROW theory, and may find novel use in functional photonic systems.",1605.09163v1 2016-05-31,Chaos in the motion of a test scalar particle coupling to Einstein tensor in Schwarzschild-Melvin black hole spacetime,"We present firstly the equation of motion for a test scalar particle coupling to Einstein tensor in the Schwarzschild-Melvin black hole spacetime through the short-wave approximation. Through analysing Poincar\'{e} sections, the power spectrum, the fast Lyapunov exponent indicator and the bifurcation diagram, we investigate the effects of coupling parameter on the chaotic behavior of the particles. With the increase of the coupling strength, we find that the motion of coupled particle for the chosen parameters becomes more regular and order for the negative couple constant. While, for the positive one, the motion of coupled particles first undergoes a series of transitions between chaotic motion and regular motion and then falls into horizon or escapes to spatial infinite. Our results show that the coupling brings about richer effects for the motion of the particles.",1605.09506v3 2016-08-01,Upper Bounds for the Number of Solutions to Spatially Coupled Sudokus,"Based on combinatorics, we evaluate the upper bounds for the number of solutions to spatially coupled Sudokus, which are popular logic puzzles.",1608.00952v1 2016-08-27,Polarization-selective out-coupling of whispering gallery modes,"Whispering gallery mode (WGM) resonators are an important building block for linear, nonlinear and quantum optical experiments. In such experiments, independent control of coupling rates to different modes can lead to improved conversion efficiencies and greater flexibility in generation of non-classical states based on parametric down conversion. In this work, we introduce a scheme which enables selective out-coupling of WGMs belonging to a specific polarization family, while the orthogonally polarized modes remain largely unperturbed. Our technique utilizes material birefringence in both the resonator and coupler such that a negative (positive) birefringence allows selective coupling to TE (TM) polarized WGMs. We formulate a new coupling condition suitable for describing the case where the refractive indices of the resonator and the coupler are almost the same, from which we derive the criterion for polarization-selective coupling. We experimentally demonstrate our proposed method using a lithium niobate disk resonator coupled to a lithium niobate prism, where we show a 22dB suppression of coupling to TM modes relative to TE modes.",1608.07660v1 2017-10-25,Strong Coupling of Collection of Emitters on Hyperbolic Meta-Material,"Recently considerable effort is devoted to the realization of the strong coupling regime of the radiation matter interaction in the context of emitter at a meta surface. The strong interaction is well realized in cavity quantum electrodynamics which also shows that the strong coupling is much easier to realize using a collection of emitters. Keeping this in mind we study if emitters on a hyperbolic meta materials can yield strong coupling regime. We show that the strong coupling can be realized for densities of emitters exceeding a critical value. A way to detect the strong coupling between emitters and a hyperbolic metamaterials is to use the Kretschman-Raether configuration. The strong coupling appears as the splitting of the re ectivity dip. In the weak coupling regime the dip position shifts. The shift and splitting can be used to sense active molecules at surfaces.",1710.09210v2 2012-05-07,Leptonic anomalous gauge couplings detection on electron positron colliders,"We studied the dimension-6 leptonic anomalous gauge couplings in the formulation of linearly realized gauge symmetry effective Lagrangian and investigated the constraints on these anomalous couplings from the existed experimental data including LEP2 and $W$/$Z$ boson decay. Some bounds of $O(0.1-10){\rm TeV}^{-2}$ on four relevant anomalous couplings are given by the Z factories. We studied the sensitivity of testing the leptonic anomalous couplings via the process $e^+e^-\rightarrow W^+W^-$ at future $e^+e^-$ linear colliders. We discussed different sensitivities to anomalous couplings at polarized and unpolarized $e^+e^-$ colliders, respectively, with 500 GeV and 1 TeV collision energy. Our results show that the a 500 GeV ILC can provide a test of the anomalous couplings, with the same relative uncertainty of cross section measurement, of $O(0.1-1){\rm TeV}^{-2}$, and a 1 TeV ILC can test the anomalous couplings of $O(0.01-0.1){\rm TeV}^{-2}$.",1205.1280v2 2012-05-09,Two-component solitons under a spatially modulated linear coupling: Inverted photonic crystals and fused couplers,"We study two-component solitons and their symmetry-breaking bifurcations (SBBs) in linearly coupled photonic systems with a spatially inhomogeneous strength of the coupling. One system models an inverted virtual photonic crystal, built by periodically doping the host medium with atoms implementing the electromagnetically induced transparency (EIT). In this system, two soliton-forming probe beams with different carrier frequencies are mutually coupled by the EIT-induced effective linear interconversion. The system is described by coupled nonlinear Schr\""{o}dinger (NLS) equations for the probes, with the linear-coupling constant periodically modulated in space according to the density distribution of the active atoms. The type of the SBB changes from sub- to supercritical with the increase of the total power of the probe beams, which does not occur in systems with constant linear-coupling constants. Qualitatively similar results for the SBB of two-component solitons are obtained, in an exact analytical form, in the model of a fused dual-core waveguide, with the linear coupling concentrated at a point.",1205.1899v1 2017-05-15,A statistical physics approach to learning curves for the Inverse Ising problem,"Using methods of statistical physics, we analyse the error of learning couplings in large Ising models from independent data (the inverse Ising problem). We concentrate on learning based on local cost functions, such as the pseudo-likelihood method for which the couplings are inferred independently for each spin. Assuming that the data are generated from a true Ising model, we compute the reconstruction error of the couplings using a combination of the replica method with the cavity approach for densely connected systems. We show that an explicit estimator based on a quadratic cost function achieves minimal reconstruction error, but requires the length of the true coupling vector as prior knowledge. A simple mean field estimator of the couplings which does not need such knowledge is asymptotically optimal, i.e. when the number of observations is much large than the number of spins. Comparison of the theory with numerical simulations shows excellent agreement for data generated from two models with random couplings in the high temperature region: a model with independent couplings (Sherrington-Kirkpatrick model), and a model where the matrix of couplings has a Wishart distribution.",1705.05403v1 2017-07-19,Photoinduced vibronic coupling in two-level dissipative systems,"Interaction of an electron system with a strong electromagnetic wave leads to rearrangement both the electron and vibrational energy spectra of a dissipative system. For instance, the optically coupled electron levels become split in the conditions of the ac Stark effect that gives rise to appearance of the nonadiabatic coupling between the electron and vibrational motions. The nonadiabatic coupling exerts a substantial impact on the electron and phonon dynamics and must be taken into account to determine the system wave functions. In this paper, the vibronic coupling induced by the ac Stark effect is considered. It is shown that the interaction between the electron states dressed by an electromagnetic field and the forced vibrations of reservoir oscillators under the action of rapid changing of the electron density with the Rabi frequency is responsible for establishment of the photoinduced vibronic coupling. However, if the resonance conditions for the optical phonon frequency and the transition frequency of electrons in the dressed state basis are satisfied, the vibronic coupling is due to the electron-phonon interaction. Additionally, photoinduced vibronic coupling results in appearance of the doubly dressed states which are formed by both the electron-photon and electron-vibrational interactions.",1709.06935v1 2017-09-25,Quantum interface between a transmon qubit and spins of nitrogen-vacancy centers,"Hybrid quantum circuits combining advantages of each individual system have provided a promising platform for quantum information processing. Here we propose an experimental scheme to directly couple a transmon qubit to an individual spin in the nitrogen-vacancy (NV) center, with a coupling strength three orders of magnitude larger than that for a single spin coupled to a microwave cavity. This direct coupling between the transmon and the NV center could be utilized to make a transmon bus, leading to a coherently virtual exchange among different single spins. Furthermore, we demonstrate that, by coupling a transmon to a low-density NV ensemble, a SWAP operation between the transmon and NV ensemble is feasible and a quantum non-demolition measurement on the state of NV ensemble can be realized on the cavity-transmon-NV-ensemble hybrid system. Moreover, on this system, a virtual coupling can be achieved between the cavity and NV ensemble, which is much larger in magnitude than the direct coupling between the cavity and the NV ensemble. The photon state in cavity can be thus stored into NV spins more efficiently through this virtual coupling.",1709.08508v1 2018-03-06,Spherical collapse and cluster number counts in dark energy models disformally coupled to dark matter,"We investigate the effects of a disformal coupling between dark energy and dark matter in the predictions of the spherical collapse and its signatures in galaxy cluster number counts. We find that the disformal coupling has no significant effects on spherical collapse at high redshifts, and in particular during matter domination epoch. However, at lower redshifts, the extrapolated linear density contrast at collapse close to redshift $z \lesssim 1$ and overdensity at virialization can be strongly suppressed by a disformal coupling between dark energy and dark matter. We also find that disformal coupling can have different imprints on cluster number counts compared with conformal coupling, such that the disformal coupling can strongly suppress the predicted number of clusters per redshift interval at $z > 0.1$ while enhance the number of cluster at $z < 0.05$. Using the specifications of eROSITA survey, we find that the disformal coupling between dark energy and dark matter can be tightly constrained by cluster number counts.",1803.02299v2 2018-03-09,Spin exchange-induced spin-orbit coupling in a superuid mixture,"We investigate the ground-state properties of a dual-species spin-1/2 Bose-Einstein condensate. One of the species is subjected to a pair of Raman laser beams that induces spin-orbit (SO) coupling, whereas the other species is not coupled to the Raman laser. In certain limits, analytical results can be obtained. It is clearly shown that, through the inter-species spin-exchange interaction, the second species also exhibits SO coupling. This mixture system displays a very rich phase diagram, with many of the phases not present in an SO coupled single-species condensate. Our work provides a new way of creating SO coupling in atomic quantum gases, and opens up a new avenue of research in SO coupled superfluid mixtures. From a practical point of view, the spin exchange-induced SO coupling may overcome the heating issue for certain atomic species when subjected to the Raman beams.",1803.03387v1 2019-01-09,Optimization of linear and nonlinear interaction schemes for stable synchronization of weakly coupled limit-cycle oscillators,"Optimization of mutual synchronization between a pair of limit-cycle oscillators with weak symmetric coupling is considered in the framework of the phase reduction theory. By generalizing a previous study on the optimization of cross-diffusion coupling matrices between the oscillators, we consider optimization of mutual coupling signals to maximize the linear stability of the synchronized state, which are functionals of the past time sequences of the oscillator states. For the case of linear coupling, optimization of the delay time and linear filitering of coupling signals are considered. For the case of nonlinear coupling, general drive-response coupling is considered, and the optimal response and driving functions are derived. The theoretical results are exemplified by numerical simulations.",1901.02721v1 2019-01-29,Formulation of a Triaxial Three-Layered Earth Rotation: I. Theory and Rotational Normal Mode Solutions,"In this study, we formulated a triaxial three-layered anelastic Earth rotation theory con-sidering various core mantle couplings, including the pressure and gravitational couplings acting on the inner core by the outer core and mantle, the viscoelectromagnetic couplings between the outer core and mantle, and between the outer and inner cores. With this formulation, we provided four numerical solutions for the rotational normal modes, including the Chandler Wobble (CW), Free Core Nutation (FCN), Free Inner Core Nutation (FICN), an the Inner Core Wobble (ICW). The triaxiality led to increased periods for the CW and ICW of about 0.01 and 0.35 mean solar days (d), respectively. The mantle anelasticity and ocean tide induced dissipations were mainly responsible for the CW, but contributed little to the FCN, while the viscoelectromagnetic coupling induced dissipations were mainly responsible for the FCN, FICN, and ICW. By investigating different types of couplings, we found that pressure coupling played the dominant role in prograde FICN, while viscoelectromagnetic or gravitational couplings either alone, or together gave rise to retrograde FICN. On the other hand, the ICW period varied extensively from 130 d to 21 yr under different core mantle coupling conditions.",1901.10066v1 2019-03-01,On the Griffiths-Yukawa coupling length of some Calabi-Yau families,"We determine the Griffiths-Yukawa coupling length of the Calabi-Yau universal families coming from hyperplane arrangements.",1903.00306v1 2019-03-11,Exchange-enhanced Ultrastrong Magnon-Magnon Coupling in a Compensated Ferrimagnet,"The ultrastrong coupling of (quasi-)particles has gained considerable attention due to its application potential and richness of the underlying physics. Coupling phenomena arising due to electromagnetic interactions are well explored. In magnetically ordered systems, the quantum-mechanical exchange-interaction should furthermore enable a fundamentally different coupling mechanism. Here, we report the observation of ultrastrong intralayer exchange-enhanced magnon-magnon coupling in a compensated ferrimagnet. We experimentally study the spin dynamics in a gadolinium iron garnet single crystal using broadband ferromagnetic resonance. Close to the ferrimagnetic compensation temperature, we observe ultrastrong coupling of clockwise and anticlockwise magnon modes. The magnon-magnon coupling strength reaches more than 30% of the mode frequency and can be tuned by varying the direction of the external magnetic field. We theoretically explain the observed phenomenon in terms of an exchange-enhanced mode-coupling mediated by a weak cubic anisotropy.",1903.04330v2 2019-03-12,Electron Counting Statistics for Non-Additive Environments,"Molecular electronics is a rapidly developing field focused on using molecules as the structural basis for electronic components. It is common in such devices for the system of interest to couple simultaneously to multiple environments. Here we consider a model comprised of a double quantum dot (or molecule) coupled strongly to vibrations and weakly to two electronic leads held at arbitrary bias voltage. The strong vibrational coupling invalidates treating the bosonic and electronic environments simply as acting additively, as would be the case in the weak coupling regime or for flat leads at infinite bias. Instead, making use of the reaction coordinate framework we incorporate the dominant vibrational coupling effects within an enlarged system Hamiltonian. This allows us to derive a non-additive form for the lead couplings that accounts properly for the influence of strong and non-Markovian coupling between the double dot system and the vibrations. Applying counting statistics techniques we track electron flow between the double dot and the electronic leads, revealing both strong-coupling and non-additive effects in the electron current, noise and Fano factor.",1903.05264v2 2019-03-28,A coupled implicit-explicit time integration method for compressible unsteady flows,"This paper addresses how two time integration schemes, the Heun's scheme for explicit time integration and the second-order Crank-Nicolson scheme for implicit time integration, can be coupled spatially. This coupling is the prerequisite to perform a coupled Large Eddy Simulation / Reynolds Averaged Navier-Stokes computation in an industrial context, using the implicit time procedure for the boundary layer (RANS) and the explicit time integration procedure in the LES region. The coupling procedure is designed in order to switch from explicit to implicit time integrations as fast as possible, while maintaining stability. After introducing the different schemes, the paper presents the initial coupling procedure adapted from a published reference and shows that it can amplify some numerical waves. An alternative procedure, studied in a coupled time/space framework, is shown to be stable and with spectral properties in agreement with the requirements of industrial applications. The coupling technique is validated with standard test cases, ranging from one-dimensional to three-dimensional flows.",1903.12568v2 2019-04-26,Effects of Interface Steps on the Valley Orbit coupling in a Si/SiGe quantum dot,"Valley-orbit coupling is a key parameter for a silicon quantum dot in determining its suitability for applications in quantum information processing. In this paper we study the effect of interface steps on the magnitude and phase of valley-orbit coupling for an electron in a silicon quantum dot. Within the effective mass approximation, we find that the location of a step on the interface is important in determining both the magnitude and the phase of the valley-orbit coupling in a Si/SiGe quantum dot. Specifically, our numerical results show that the magnitude of valley orbit coupling can be suppressed up to 75\% by a step of one atomic monolayer, and its phase can change by almost $\pi$. When two steps are present, the minimum value of the valley-orbit coupling can even approach zero. We also clarify the effects of an applied external magnetic field and the higher orbital states on the valley-orbit coupling. Overall, our results illustrate how interface roughness affect the valley-orbit coupling in silicon, and how spin qubits in silicon may be affected.",1904.11944v1 2019-08-20,Quantum synchronization and correlation in bidirectionally and unidirectionally coupled optomechanical oscillators,"Optically coupled optomechanical oscillators has turned out to be a versatile experimental resource for exploring optomechanical synchronizations and correlations. In this work, we investigate the phenomena of quantum synchronization and quantum correlations in two optically coupled optomechanical oscillators with two different topologies. In one case the oscillators are coupled with optical photons in a reversible manner, termed as bidirectional coupling, while in the other photons are allowed to enter to the other oscillator but not allowed to exchanged back in the opposite direction, termed as unidirectional coupling. Our results shows that irrespective of these configurations, when synchronization builds up, the two oscillators also become quantum mechanically correlated with a finite degree of Gaussian quantum discord. However, we find that depending on these topologies, both synchronization and quantum discord behave in a very distinctive manner. For instance, in bidirectionally coupled optomechanical oscillators, we find both quantum synchronization and discord exhibit a tongue like pattern which is the quantum analogue of an Arnold tongue. Whereas, in the unidirectionally coupled oscillators, we observe a novel blockade like behavior for quantum phase synchronization, also known as the quantum synchronization blockade, while quantum discord being failed to map such an anomalous behavior.",1908.07296v1 2019-12-03,Paramagnetic molecule induced strong antiferromagnetic exchange coupling on a magnetic tunnel junction based molecular spintronics device,"This paper reports our Monte Carlo (MC) studies aiming to explain the experimentally observed paramagnetic molecule induced antiferromagnetic coupling between the ferromagnetic (FM) electrodes. Recently developed magnetic tunnel junction based molecular spintronics devices (MTJMSDs), which were prepared by chemically bonding the paramagnetic molecules between the FM electrodes along the exposed side edges of magnetic tunnel junctions, exhibited molecule induced strong antiferromagnetic coupling. Our MC studies focused on the atomic model analogous to the MTJMSD and studied the effect of molecules magnetic couplings with the two FM electrodes. Simulations show that when a molecule established ferromagnetic coupling with one electrode and antiferromagnetic coupling with the other electrode then theoretical results effectively explained the experimental findings. MC and experimental studies suggest that the strength of exchange coupling between molecule and FM electrode should be 50 percent of the interatomic exchange coupling strength of the FM electrodes.",1912.01343v1 2019-12-12,"Variational Coupling Revisited: Simpler Models, Theoretical Connections, and Novel Applications","Variational models with coupling terms are becoming increasingly popular in image analysis. They involve auxiliary variables, such that their energy minimisation splits into multiple fractional steps that can be solved easier and more efficiently. In our paper we show that coupling models offer a number of interesting properties that go far beyond their obvious numerical benefits. We demonstrate that discontinuity-preserving denoising can be achieved even with quadratic data and smoothness terms, provided that the coupling term involves the $L^1$ norm. We show that such an $L^1$ coupling term provides additional information as a powerful edge detector that has remained unexplored so far. While coupling models in the literature approximate higher order regularisation, we argue that already first order coupling models can be useful. As a specific example, we present a first order coupling model that outperforms classical TV regularisation. It also establishes a theoretical connection between TV regularisation and the Mumford-Shah segmentation approach. Unlike other Mumford-Shah algorithms, it is a strictly convex approximation, for which we can guarantee convergence of a split Bregman algorithm.",1912.05888v1 2016-12-04,Non-minimal Coupling of Torsion-matter Satisfying Null Energy Condition for Wormhole Solutions,"We explore wormhole solutions in a non-minimal torsion-matter coupled gravity by taking an explicit non-minimal coupling between the matter Lagrangian density and an arbitrary function of torsion scalar. This coupling depicts the transfer of energy and momentum between matter and torsion scalar terms. The violation of null energy condition occurred through effective energy-momentum tensor incorporating the torsion-matter non-minimal coupling while normal matter is responsible for supporting the respective wormhole geometries. We consider energy density in the form of non-monotonically decreasing function along with two types of models. First model is analogous to curvature-matter coupling scenario, that is, torsion scalar with $T$-matter coupling while the second one involves a quadratic torsion term. In both cases, we obtain wormhole solutions satisfying null energy condition. Also, we find that the increasing value of coupling constant minimizes or vanishes the violation of null energy condition through matter.",1612.02042v1 2017-07-18,The Utility of Phase Models in Studying Neural Synchronization,"Synchronized neural spiking is associated with many cognitive functions and thus, merits study for its own sake. The analysis of neural synchronization naturally leads to the study of repetitive spiking and consequently to the analysis of coupled neural oscillators. Coupled oscillator theory thus informs the synchronization of spiking neuronal networks. A crucial aspect of coupled oscillator theory is the phase response curve (PRC), which describes the impact of a perturbation to the phase of an oscillator. In neural terms, the perturbation represents an incoming synaptic potential which may either advance or retard the timing of the next spike. The phase response curves and the form of coupling between reciprocally coupled oscillators defines the phase interaction function, which in turn predicts the synchronization outcome (in-phase versus anti-phase) and the rate of convergence. We review the two classes of PRC and demonstrate the utility of the phase model in predicting synchronization in reciprocally coupled neural models. In addition, we compare the rate of convergence for all combinations of reciprocally coupled Class I and Class II oscillators. These findings predict the general synchronization outcomes of broad classes of neurons under both inhibitory and excitatory reciprocal coupling.",1707.05713v1 2017-11-15,Synchronization versus stability of the invariant distribution for a class of globally coupled maps,"We study a class of globally coupled maps in the continuum limit, where the individual maps are expanding maps of the circle. The circle maps in question are such that the uncoupled system admits a unique absolutely continuous invariant measure (acim), which is furthermore mixing. Interaction arises in the form of diffusive coupling, which involves a function that is discontinuous on the circle. We show that for sufficiently small coupling strength the coupled map system admits a unique absolutely continuous invariant distribution, which depends on the coupling strength $\varepsilon$. Furthermore, the invariant density exponentially attracts all initial distributions considered in our framework. We also show that the dependence of the invariant density on the coupling strength $\varepsilon$ is Lipschitz continuous in the BV norm. When the coupling is sufficiently strong, the limit behavior of the system is more complex. We prove that a wide class of initial measures approach a point mass with support moving chaotically on the circle. This can be interpreted as synchronization in a chaotic state.",1711.05461v2 2017-11-16,Tunable hyperbolic metamaterial cavity towards few exciton strong coupling,"We theoretically investigate coupling interaction between molecule excitons and whispering gallery modes (WGMs) that approaches the limit of single exciton strong coupling in hyperbolic metamaterial (HMM) cavity, composed of a dielectric core wrapped by several stacks of alternative layers of metal and dielectric. We demonstrate that associated with the excitation of the whispering gallery mode, the electric fields with resonance wavelengths that are much larger than the cavity size can be highly localized within a dielectric layer, leading to extremely small mode volumes. By using temporal coupled mode theory to model the interaction in the proposed WGMs-exciton system, we are able to demonstrate that the coupling between molecular excitons and hyperbolic cavity WGMs can reach the strong coupling regime. Furthermore, we also prove that changing both the thickness of inner core and outermost layer can lead to invariant resonance frequency while the threshold number of coupled excitons to fulfill the criteria for strong coupling remains ~ 4 in various sets of tunable HMM cavities.",1711.05901v1 2018-10-30,Effects of periodically modulated coupling on amplitude death in nonidentical oscillators,"The effects of periodically modulated coupling on amplitude death in two coupled nonidentical oscillators are explored. The AD domain could be significantly influenced by tuning the modulation amplitude and the modulation frequency of the modulated coupling strength. There is an optimal value of modulation amplitude for the modulated coupling with which the largest AD domain is observed in the parameter space. The AD domain is enlarged with the decrease of the modulation frequency for a given small modulation amplitude, while is shrunk with decrease of the modulation frequency for a given large modulation amplitude. The mechanism of AD in the presence of periodic modulation in the coupling is investigated via the local condition Lyapunov exponent of the coupled system. The stability of AD state can be well characterized by conditional Lyapunov exponent. The coupled system experiencing from the oscillatory state to AD is clearly indicated by the observation that the conditional Lyapunov exponent transits from positive to negative. Our results are helpful to many potential applications for the research of neuroscience and dynamical control in engineering.",1810.12548v2 2019-05-16,Modulating quantum Fisher information of qubit in dissipative cavity by coupling strength,"By using the non-Markovian master equation, we investigate the effect of the cavity and the environment on the quantum Fisher information (QFI) of an atom qubit system in a dissipation cavity. We obtain the formulae of QFI for two different initial states and analyze the effect of the atom-cavity coupling and the cavity-reservoir coupling on the QFI. The results show that the dynamic behavior of the QFI is obviously dependent on the initial atomic states, the atom-cavity coupling and the cavity-reservoir coupling. The stronger the atom-cavity coupling, the quicker the QFI oscillates and the slower the QFI reduces. Especially, the QFI will tend to a stable value not zero if the atom-cavity coupling is large enough. On the other hand, the smaller the cavity-reservoir coupling, the stronger the non-Markovian effect, the slower the QFI decay. In other words, choosing the best parameter can improve the accuracy of parameter estimation. In addition, the physical explanation of the dynamic behavior of the QFI is given by means of the QFI flow.",1905.06608v1 2019-05-19,Flavor signatures of complex anomalous $tcZ$ couplings,"In this work we study the effects of anomalous $tcZ$ couplings. Such couplings would potentially affect several neutral current decays of $K$ and $B$ mesons via $Z$-penguin diagrams. Using constraints from relevant observables in $K$ and $B$ sectors, we find that the 2$\sigma$ upper bound on the branching ratio of ${\cal B}(t \to c Z)$ is $1.47 \times 10^{-5}$ for real coupling and $1.91 \times 10^{-4}$ for complex coupling. The current experimental upper bound from ATLAS and CMS collaborations on the branching ratio of $t \to c Z$ are $2.4 \times 10^{-4}$ and $4.9\times 10^{-4}$ at $95\%$ C.L., respectively. Hence the possibility of observation of $t \to c Z$ decay at the level of $10^{-4}$ would imply the anomalous couplings to be complex. Such complex couplings should also show up its presence in other related decays. We find that an order of magnitude enhancement is possible in the branching ratio of $K_L \to \pi^0 \nu \bar{\nu}$. Further, the complex $tcZ$ coupling can also provide large enhancements in many $CP$ violating angular observables in $B \to K^* \mu^+ \mu^-$ decay.",1905.07690v2 2019-05-23,Strong Cosmic Censorship in Charged de Sitter spacetime with Scalar Field Non-minimally Coupled to Curvature,"We examine the stability and the strong cosmic censorship in the Reissner-Nordstrom-de Sitter (RN-dS) black hole by investigating the evolution of a scalar field non-minimally coupled to the curvature. We find that when the coupling parameter is negative, the RN-dS black hole experiences instability. The instability disappears when the coupling parameter becomes non-negative. With the increase of the coupling parameter, the violation of the strong cosmic censorship occurs at a larger critical charge ratio. But such an increase of the critical charge is suppressed by the increase of the cosmological constant. Different from the minimal coupling situation, it is possible to accommodate $\beta\ge1$ in the near extremal black hole when the scalar field is non-minimally coupled to curvature. The increase of the cosmological constant can allow $\beta\ge1$ to be satisfied for even smaller value of the coupling parameter. The existence of $\beta\ge1$ implies that the resulting curvature can continuously cross the Cauchy horizon.",1905.09461v1 2020-09-18,Differential molecule-cavity mode coupling in soft-cavities,"The way molecules absorb, transfer, and emit light can be dramatically modified by coupling them to optical cavities. The extent of the modification is often defined by the cavity-molecule coupling strength. Evaluating this coupling strength for different types of modes supported by a cavity is crucial in designing cavities for molecule-cavity coupling. Here we probe a unique multimode cavity, a dielectric microsphere, also called a soft-cavity, which supports two distinct types of mode, dark-field scattering (DFS) modes and whispering gallery modes (WGM). Though seemingly similar, these modes show different characteristics such as spatial electric field profile, resonance line-width etc. We investigated coupling of a mono-layer of J-aggregated dye molecules and a dielectric plastic microsphere using two techniques, far-field excitation and evanescent excitation to generate DFS modes and WGMs respectively. We found that using WGMs we observe a clear signature of strong coupling, whereas with DFS modes we do not. We compared our experimental data to a simple coupled oscillator model and performed finite-element method based numerical simulations to provide a clearer understanding of our experimental findings.",2009.08760v1 2021-02-01,Numerical study of the coupling layer between transducer and chip in acoustofluidic devices,"We study by numerical simulation in two and three dimensions the coupling layer between the transducer and the microfluidic chip in ultrasound acoustofluidic devices. The model includes the transducer with electrodes, the microfluidic chip with a liquid-filled microchannel, and the coupling layer between the transducer and the chip. We consider two commonly used coupling materials, solid epoxy glue and viscous glycerol, as well as two commonly used device types, glass capillary tubes and silicon-glass chips. We study how acoustic resonances in ideal devices without a coupling layer is either sustained or attenuated as a coupling layer of increasing thickness is inserted. We establish a simple criterion based on the phase of the acoustic wave for whether a given zero-layer resonance is sustained or attenuated by the addition of a coupling layer. Finally, we show that by controlling the thickness and the material, the coupling layer can be used as a design component for optimal and robust acoustofluidic resonances.",2102.00762v1 2021-02-03,Coupled Hypergraph Maps and Chaotic Cluster Synchronization,"Coupled map lattices (CMLs) are prototypical dynamical systems on networks/graphs. They exhibit complex patterns generated via the interplay of diffusive/Laplacian coupling and nonlinear reactions modelled by a single iterated map at each node; the maps are often taken as unimodal, e.g., logistic or tent maps. In this letter, we propose a class of higher-order coupled dynamical systems involving the hypergraph Laplacian, which we call coupled hypergraph maps (CHMs). By combining linearized (in-)stability analysis of synchronized states, hypergraph spectral theory, and numerical methods, we detect robust regions of chaotic cluster synchronization occurring in parameter space upon varying coupling strength and the main bifurcation parameter of the unimodal map. Furthermore, we find key differences between Laplacian and hypergraph Laplacian coupling and detect various other classes of periodic and quasi-periodic patterns. The results show the high complexity of coupled graph maps and indicate that they might be an excellent universal model class to understand the similarities and differences between dynamics on classical graphs and dynamics on hypergraphs.",2102.02272v2 2015-12-31,Coupling qubits in circuit-QED cavities connected by a bridge qubit,"We analyze a coupling scheme for qubits in different cavities of circuit-QED architecture. In contrast to the usual scheme where the cavities are coupled by an interface capacitance we employ a bridge qubit connecting cavities to mediate two-qubit coupling. This active coupling scheme makes it possible to switch on/off and adjust the strength of qubit-qubit coupling, which is essential for scalability of quantum circuit. By transforming the Hamiltonian we obtain an exact expression of two-qubit coupling in the rotating-wave approximation. For the general case of $n$ qubits the Hamiltonian can produce the W state as an eigenstate of the system. We calculate the decay rate of the coupled qubit-resonator system to find that it is viable in real experiments.",1512.09218v2 2016-11-11,Strong and tunable couplings in flux-mediated optomechanics,"We investigate superconducting interference device (SQUID) with two asymmetric Josephson junctions coupled to a mechanical resonator embedded in the loop of the SQUID. We quantize this system in the case when the frequency of the mechanical resonator is much lower than the cavity frequency of the SQUID and in the case when they are comparable. In the first case, the radiation pressure and cross-Kerr type interactions arise and are modified by asymmetry. Cross-Kerr type coupling is the leading term at the extremum points where radiation pressure is zero. In the second case, the main interaction is single-photon beam splitter, which exists only at finite asymmetry. Another interaction in this regime is of cross-Kerr type, which exists at all asymmetries, but generally much weaker than the beam splitter interaction. Increasing magnetic field can substantially enhance optomechanical couplings strength with the potential for the radiation pressure coupling to reach the single-photon strong coupling regime, even the ultrastrong coupling regime, in which the single-photon coupling rate exceeds the mechanical frequency.",1611.03842v1 2016-11-17,Both Inter- and Intramolecular Coupling of O-H Groups Determine the Vibrational Response of the Water/Air Interface,"Vibrational coupling is relevant not only for dissipation of excess energy after chemical reactions but also for elucidating molecular structure and dynamics. It is particularly important for OH stretch vibrational spectra of water, for which it is known that in bulk both intra- and intermolecular coupling alter the intensity and line shape of the spectra. In contrast with bulk, the unified picture of the inter/intra-molecular coupling of OH groups at the water-air interface has been lacking. Here, combining sum-frequency generation experiments and simulation for isotopically diluted water and alcohols, we unveil effects of inter- and intramolecular coupling on the vibrational spectra of interfacial water. Our results show that both inter- and intramolecular coupling contribute to the OH stretch vibrational response of the neat H2O surface, with intramolecular coupling generating a double-peak feature, while the intermolecular coupling induces a significant red shift in the OH stretch response.",1611.06243v1 2018-01-17,Synchronization of electrically coupled resonate-and-fire neurons,"Electrical coupling between neurons is broadly present across brain areas and is typically assumed to synchronize network activity. However, intrinsic properties of the coupled cells can complicate this simple picture. Many cell types with strong electrical coupling have been shown to exhibit resonant properties, and the subthreshold fluctuations arising from resonance are transmitted through electrical synapses in addition to action potentials. Using the theory of weakly coupled oscillators, we explore the effect of both subthreshold and spike-mediated coupling on synchrony in small networks of electrically coupled resonate-and-fire neurons, a hybrid neuron model with linear subthreshold dynamics and discrete post-spike reset. We calculate the phase response curve using an extension of the adjoint method that accounts for the discontinuity in the dynamics. We find that both spikes and resonant subthreshold fluctuations can jointly promote synchronization. The subthreshold contribution is strongest when the voltage exhibits a significant post-spike elevation in voltage, or plateau. Additionally, we show that the geometry of trajectories approaching the spiking threshold causes a ""reset-induced shear"" effect that can oppose synchrony in the presence of network asymmetry, despite having no effect on the phase-locking of symmetrically coupled pairs.",1801.05874v1 2018-08-09,Massive nonminimally coupled scalar field in Reissner-Nordström spacetime: Long-lived quasinormal modes and instability,"Here we show that the phenomenon of arbitrarily long-lived quasinormal modes (called quasiresonances) of a massive scalar field in the vicinity of a black hole is not an artifact of the test field approximation, but takes place also when the (derivative) coupling of a scalar field with the Einstein tensor is taken into consideration. We observe that at large coupling and high multipole numbers, the growing modes appear in the spectrum, which are responsible for the eikonal instability of the field. For small coupling, when the configuration is stable, there appear the purely imaginary quasinormal modes which are nonperturbative in the coupling constant. At the sufficiently small coupling the nonminimal scalar field is stable and the asymptotic late-time tails are not affected by the coupling term. The accurate calculations of quasinormal frequencies for a massive scalar field with the derivative coupling in the Reissner-Nordstr\""om black-hole background are performed with the help of Frobenius method, time-domain integration and WKB expansion.",1808.03346v2 2018-08-26,Core-Halo Collective Instabilities,"At strong space charge, transverse modes of the bunch core may effectively couple with those of the halo, leading to instabilities well below the core-only transverse mode-coupling threshold.",1808.08498v1 2019-06-03,Traveling kinks in an infinite array of weakly coupled pendula,"We prove the existence of heteroclinic traveling waves (kinks) in an infinite array of weakly coupled pendula. Our approach is to apply a perturbation argument from the anti-continuum limit.",1906.00527v1 2019-06-16,Density Evolution Analysis of Partially Information Coupled Turbo Codes on the Erasure Channel,"In this paper, we investigate the performance of a class of spatially coupled codes, namely partially information coupled turbo codes (PIC-TCs) over the binary erasure channel (BEC). This class of codes enjoy flexible code rate adjustment by varying the coupling ratio. Moreover, the coupling method can be directly applied to any component codes without changing the encoding and decoding architectures of the underlying component codes. However, the theoretical performance of PIC-TCs has not been fully investigated. For this work, we consider the codes that have coupling memory $m$ and study the corresponding graph model. We then derive the exact density evolution equations for these code ensembles with any given coupling ratio and coupling memory $m$ to precisely compute their belief propagation decoding thresholds for the BEC. Our simulation results verify the correctness of our theoretical analysis and also show better error performance over uncoupled turbo codes with a variety of code rates on the BEC.",1906.06649v1 2019-06-28,Ultra-Compact Coupling Structures for Heterogeneously Integrated Silicon Lasers,"Due to the inherent in-direct bandgap nature of Silicon, heterogeneous integration of semiconductor lasers on Silicon on Insulator (SOI) is crucial for next-generation on-chip optical interconnects. Compact, high-efficient and high-tolerant couplers between III-V light source and silicon chips have been the challenge for photonic integrated circuit (PIC). Here, we redesign the taper adiabatic coupler with the total coupling length of only 4 {\mu}m, and propose another two novel slot coupler and bridge-SWG coupler with both coupling length of 7 {\mu}m, to heterogeneously integrate III-V lasers and silicon chips. We study theoretically the optical mode coupling process through the redesigned taper coupler, the final coupling results match well with the simulation in 3D-FDTD. The three compact couplers represent fundamental TE mode coupling efficiencies all over 90%, even 95.7% for bridge-SWG coupler, to the best of our knowledge, are also the shortest coupling structures (7 um). Moreover, these coupling structures also possess excellent fabrication tolerance.",1906.12027v1 2019-06-28,Microscopic mechanism of level attraction,"The emerging level attraction from dissipative light-matter coupling converges the typical Rabi-splitting feature from coherent coupling and exhibits potentials in topological information processing. However, the underlying microscopic quantum mechanism of dissipative coupling still remains unclear, which brings difficulties in quantifying and manipulating coherence-dissipation competition and thereby the flexible control of level attraction. Here, by coupling magnon to a cavity supporting both standing and travelling waves, we identify the travelling-wave state to be responsible for magnon-photon dissipative coupling. By characterizing radiative broadening of magnon linewidth, we quantify the coherent and dissipative coupling strengths and their competition. The effective magnon-photon coupling strength, as a net result of competition, is analytically presented in quantum theory to show good agreement with measurements. In this manner, we extend the control dimension of level attraction by tuning field torque on magnetization or global cavity geometry. Our finding opens new routines to engineer coupled harmonic oscillator system.",1906.12142v2 2019-07-30,$a_1$ meson-baryon coupling constants in the framework of soft-wall and hard-wall AdS/QCD models,"We calculate the $a_1$ meson-nucleon coupling constant in the framework of soft-wall and hard-wall AdS/QCD models. In the bulk of AdS space were written bulk interaction Lagrangians for a minimal gauge coupling, a magnetic gauge coupling and a triple coupling. To use AdS/CFT correspondence and these bulk interaction Lagrangians we calculate the $a_1$ axial-vector meson-nucleon coupling constant in the boundary of AdS space within both models. We observe that the numerical values for the $g_{a_1 NN}$ coupling constant in the framework of both models are more close to the experimental value than results in other works. We also calculate the $g_{a_1 \Delta \Delta}$ axial-vector meson-$\Delta$-baryon coupling constant in the framework of hard-wall AdS/QCD model.",1907.13477v2 2019-10-24,Polytope duality for families of $K3$ surfaces and coupling,"We study a relation between coupling introduced by Ebeling and the polytope duality among families of $K3$ surfaces.",1910.10941v1 2019-10-24,Lattice duality for coupling pairs admitting polytope duality with trivial toric contribution,"We study a lattice duality among families of $K3$ surfaces associated to coupling pairs that admit polytope duality with trivial toric contribution.",1910.10943v1 2020-01-02,Single-photon scattering and bound states in an atom-waveguide system with two or multiple coupling points,"In this paper, we investigate the single-photon scattering and bound states in a one-dimensional coupled-resonator waveguide which couples to a single artificial giant atom with two or more coupling points. When the atom couples to the waveguide via two resonators, the single-photon reflection rate is characterized by either Breit-Wigner or Fano line shapes. When the atom couples to the waveguide via multiple resonators, we numerically show how the destructive interference effect leads to a complete single-photon reflection. We also find a phase transition phenomena for the multi-resonator coupling case, which reveals that the upper bound state only exists when the atom-waveguide coupling strength is above a critical value.",2001.00414v2 2020-01-08,Quasi-Newton Waveform Iteration for Partitioned Fluid-Structure Interaction,"We present novel coupling schemes for partitioned multi-physics simulation that combine four important aspects for strongly coupled problems: implicit coupling per time step, fast and robust acceleration of the corresponding iterative coupling, support for multi-rate time stepping, and higher-order convergence in time. To achieve this, we combine waveform relaxation -- a known method to achieve higher order in applications with split time stepping based on continuous representations of coupling variables in time -- with interface quasi-Newton coupling, which has been developed throughout the last decade and is generally accepted as a very robust iterative coupling method even for gluing together black-box simulation codes. We show convergence results (in terms of convergence of the iterative solver and in terms of approximation order in time) for two academic test cases -- a heat transfer scenario and a fluid-structure interaction simulation. We show that we achieve the expected approximation order and that our iterative method is competitive in terms of iteration counts with those designed for simpler first-order-in-time coupling.",2001.02654v2 2020-01-09,Coupling loss at the end connections of REBCO stacks: 2D modelling and measurement,"In high power density superconducting motors, superconducting tapes are usually stacked and connected together at terminals to improve the current capacity. When a parallel sinusoidal magnetic field is applied on this partially coupled stack, the coupling current is induced and causes additional coupling loss. Usually 3D modeling is needed to calculate the coupling loss but it takes too much computing resource and time. In this paper, a numerical 2D modeling by minimum electromagnetic entropy production (MEMEP) method is developed to speed up the calculation. The presented MEMEP model shows good accuracy and the capability to take the realistic resistance between tapes into account for coupling loss calculation with a high number of mesh element, which agrees to measurements.Thanks to the model, a systemic study of coupling loss on amplitude-dependence, frequency-dependence, resistance-dependence, and length-dependence, is presented and discussed. The results reveal the features of coupling loss which is very helpful devices with multi-tape conductors, such as the stator or rotor windings of motors.",2001.02866v1 2020-02-05,Instantaneous shear modulus of Yukawa fluids across coupling regimes,"The high frequency (instantaneous) shear modulus of three-dimensional Yukawa systems is evaluated in a wide parameter range, from the very weakly coupled gaseous state to the strongly coupled fluid at the crystallization point (Yukwa melt). This allows us to quantify how shear rigidity develops with increasing coupling and inter-particle correlations. The radial distribution functions (RDFs) needed to calculate the excess shear modulus have been obtained from extensive molecular dynamics (MD) simulations. MD results demonstrate that fluid RDFs appear quasi-universal on the curves parallel to the melting line of a Yukawa solid, in accordance with the isomorph theory of Roskilde-simple systems. This quasi-universality, allows to simplify considerably calculations of quantities involving integrals of the RDF (elastic moduli represent just one relevant example). The calculated reduced shear modulus grows linearly with the coupling parameter at weak coupling and approaches a quasi-constant asymptote at strong coupling. The asymptotic value at strong coupling is in reasonably good agreement with the existing theoretical approximation.",2002.01801v1 2020-04-23,Strong coupling between magnons confined in a single magnonic cavity,"Strong coupling between magnons and cavity photons was studied extensively for quantum electrodynamics in the past few years. Recently, the strong magnon-magnon coupling between adjacent layers in magnetic multilayers has been reported. However, the strongly coupled magnons confined in a single nanomagnet remains to be revealed. Here, we report the interaction between different magnon modes in a single magnonic cavity. The intermodel coupling between edge and center magnon modes in the strong coupling regime was approached with a maximum coupling strength of 0.494 GHz and cooperativity of 60.1 with a damping of 1X10-3. Furthermore, it is found that the coupling strength is highly dependent on the geometric parameters of the magnonic cavity. Our findings could greatly enrich the still evolving field of quantum magnonics.",2004.11058v1 2020-05-12,"Dissipative coupling, dispersive coupling and its combination in simplest opto-mechanical systems","We apply strategy of variational measurement to simplest variant of dissipative coupling (test mass displacement change transitivity of a single mirror) and compare it with simplest dispersive coupling (a single mirror as a test mass, which position changes the phase of reflected wave). We compare a ponderomotive squeezing in this two kinds of coupling. Also we analyze simplest variant of combined coupling, in which both dissipative and dispersive couplings are used, and show that it creates stable optical rigidity even in case of single pump. We demonstrate that variational measurement can be applied for combined coupling.",2005.06003v1 2020-10-26,An exploratory study on machine learning to couple numerical solutions of partial differential equations,"As further progress in the accurate and efficient computation of coupled partial differential equations (PDEs) becomes increasingly difficult, it has become highly desired to develop new methods for such computation. In deviation from conventional approaches, this short communication paper explores a computational paradigm that couples numerical solutions of PDEs via machine-learning (ML) based methods, together with a preliminary study on the paradigm. Particularly, it solves PDEs in subdomains as in a conventional approach but develops and trains artificial neural networks (ANN) to couple the PDEs' solutions at their interfaces, leading to solutions to the PDEs in the whole domains. The concepts and algorithms for the ML coupling are discussed using coupled Poisson equations and coupled advection-diffusion equations. Preliminary numerical examples illustrate the feasibility and performance of the ML coupling. Although preliminary, the results of this exploratory study indicate that the ML paradigm is promising and deserves further research.",2010.13917v1 2021-01-18,Synchronization of wave structures in a heterogeneous multiplex network of 2D vdP lattices with attractive and repulsive intra-layer coupling,"We explore numerically the synchronization effects in a heterogeneous two-layer network of two-dimensional (2D) lattices of van der Pol oscillators.The inter-layer coupling of the multiplex network has an attractive character. One layer of 2D lattices is characterized by attractive coupling of oscillators and demonstrates a spiral wave regime for both the local and nonlocal interaction. The oscillators in the second layer are coupled through active elements and the interaction between them has the repulsive character. We show that the lattice with the repulsive type of coupling demonstrates complex spatiotemporal cluster structures, which can be called as labyrinth-like structures. We show for the first time that this multiplex network with fundamentally different types of intra-layer coupling demonstrates the mutual synchronization and a competition between two types of structures. Our numerical study indicates that the synchronization threshold and the type of spatiotemporal patterns in both the layers strongly depend on the ratio of the intra-layer coupling strength of the two lattices. We also analyze the impact of intra-layer coupling ranges on the synchronization effects.",2101.07334v1 2021-01-22,Mass-Conserving Implicit-Explicit Methods for Coupled Compressible Navier-Stokes Equations,"Earth system models are composed of coupled components that separately model systems such as the global atmosphere, ocean, and land surface. While these components are well developed, coupling them in a single system can be a significant challenge. Computational efficiency, accuracy, and stability are principal concerns. In this study, we focus on these issues. In particular, implicit-explicit (IMEX) tight and loose coupling strategies are explored for handling different time scales. For a simplified model for the air-sea interaction problem, we consider coupled compressible Navier-Stokes equations with an interface condition. Under the rigid-lid assumption, horizontal momentum and heat flux are exchanged through the interface. Several numerical experiments are presented to demonstrate the stability of the coupling schemes. We show both numerically and theoretically that our IMEX coupling methods are mass conservative for a coupled compressible Navier-Stokes system with the rigid-lid condition.",2101.09263v3 2021-03-20,FEniCS-preCICE: Coupling FEniCS to other Simulation Software,"The new software FEniCS-preCICE is a middle software layer, sitting in between the existing finite-element library FEniCS and the coupling library preCICE. The middle layer simplifies coupling (existing) FEniCS application codes to other simulation software via preCICE. To this end, FEniCS-preCICE converts between FEniCS and preCICE mesh and data structures, provides easy-to-use coupling conditions, and manages data checkpointing for implicit coupling. The new software is a library itself and follows a FEniCS-native style. Only a few lines of additional code are necessary to prepare a FEniCS application code for coupling. We illustrate the functionality of FEniCS-preCICE by two examples: a FEniCS heat conduction code coupled to OpenFOAM and a FEniCS linear elasticity code coupled to SU2. The results of both scenarios are compared with other simulation software showing good agreement.",2103.11191v2 2021-03-19,Detection of coupling in Duffing oscillator systems,"In complex dynamical systems, the detection of coupling and its direction from observed time series is a challenging task. We study coupling in coupled Duffing oscillator systems in regular and chaotic dynamical regimes. By observing the conditional mutual information (CMI) based on the Shannon entropy, we successfully infer the direction of coupling for different system regimes. Moreover, we show that in the weak coupling limit the values of CMI can be used to infer the coupling parameters by computing the derivative of the conditional mutual information with respect to the coupling strength, called the information susceptibility. The complete numerical implementation is available at https://repo.ijs.si/mbresar/duffing-cmi.",2103.13316v2 2021-04-23,Parametrizations of local vertex corrections from weak to strong coupling: importance of the Hedin three-leg vertex,"In the study of correlated systems, approximations based on the dynamical mean-field theory (DMFT) provide a practical way to take local vertex corrections into account, which capture, respectively, particle-particle screening at weak coupling and the formation of the local moment at strong coupling. We show that in both limits the local vertex corrections can be efficiently parametrized in terms of single-boson exchange, such that the two-particle physics described by DMFT and its diagrammatic extensions is recovered to good approximation and at a reduced computational cost. Our investigation highlights the importance of the frequency-dependent fermion-boson coupling (Hedin vertex) for local vertex corrections. Namely, at weak coupling the fermion-spin-boson coupling suppresses the N\'eel temperature of the DMFT approximation compared to the static mean-field, whereas for large interaction it facilitates a huge enhancement of local spin-fluctuation exchange, giving rise to the effective-exchange energy scale $4t^2/U$. We find that parametrizations of the vertex which neglect the nontrivial part of the fermion-boson coupling fail qualitatively at strong coupling.",2104.11534v3 2021-05-08,Accurate Mode-Coupling Characterization of Low-Crosstalk Ring-Core Fibers using Integral Calculation based Swept-Wavelength Interferometry Measurement,"In this paper, to accurately characterize the low inter-mode coupling of the weakly-coupled few mode fibers (FMFs), we propose a modified inter-mode coupling characterization method based on swept-wavelength interferometry measurement, in which an integral calculation approach is used to eliminate significant sources of error that may lead to underestimation of the power coupling coefficient. Using the proposed characterization method, a low-crosstalk ring-core fiber (RCF) with low mode dependent loss (MDL) and with single span length up to 100 km is experimentally measured to have low power coupling coefficients between high-order orbital angular momentum (OAM) mode groups of below -30 dB/km over C band. The measured low coupling coefficients based on the proposed method are verified by the direct system power measurements, proving the feasibility and reliability of the proposed inter-mode coupling characterization method.",2105.03667v2 2021-05-14,Sparse optimization of mutual synchronization in collectively oscillating networks,"We consider a pair of collectively oscillating networks of dynamical elements and optimize their internetwork coupling for efficient mutual synchronization based on the phase reduction theory developed in Ref. [H. Nakao, S. Yasui, M. Ota, K. Arai, and Y. Kawamura, Chaos 28, 045103 (2018)]. The dynamical equations describing a pair of weakly coupled networks are reduced to a pair of coupled phase equations, and the linear stability of the synchronized state between the networks is represented as a function of the internetwork coupling matrix. We seek the optimal coupling by minimizing the Frobenius and L1 norms of the internetwork coupling matrix for the prescribed linear stability of the synchronized state. Depending on the norm, either a dense or sparse internetwork coupling yielding efficient mutual synchronization of the networks is obtained. In particular, a sparse yet resilient internetwork coupling is obtained by L1-norm optimization with additional constraints on the individual connection weights.",2105.06788v1 2021-06-22,The Two Scaling Regimes of the Thermodynamic Uncertainty Relation for the KPZ-Equation,"We investigate the thermodynamic uncertainty relation for the $(1+1)$ dimensional Kardar-Parisi-Zhang equation on a finite spatial interval. In particular, we extend the results for small coupling strengths obtained previously to large values of the coupling parameter. It will be shown that, due to the scaling behavior of the KPZ equation, the TUR product displays two distinct regimes which are separated by a critical value of an effective coupling parameter. The asymptotic behavior below and above the critical threshold is explored analytically. For small coupling, we determine this product perturbatively including the fourth order; for strong coupling we employ a dynamical renormalization group approach. Whereas the TUR product approaches a value of $5$ in the weak coupling limit, it asymptotically displays a linear increase with the coupling parameter for strong couplings. The analytical results are then compared to direct numerical simulations of the KPZ equation showing convincing agreement.",2106.11843v1 2021-07-02,Tunable strong coupling of mechanical resonance between spatially separated FePS$_3$ nanodrums,"Coupled nanomechanical resonators made of two-dimensional materials are promising for processing information with mechanical modes. However, the challenge for these types of systems is to control the coupling. Here, we demonstrate strong coupling of motion between two suspended membranes of the magnetic 2D material FePS$_3$. We describe a tunable electromechanical mechanism for control over both the resonance frequency and the coupling strength using a gate voltage electrode under each membrane. We show that the coupling can be utilized for transferring data from one drum to the other by amplitude modulation. Finally, we also study the temperature dependence of the coupling, and in particular how it is affected by the antiferromagnetic phase transition characteristic of this material. The presented electrical coupling of resonant magnetic 2D membranes holds promise of transferring mechanical energy over a distance at low electrical power, thus enabling novel data readout and information processing technologies.",2107.01262v1 2021-07-21,Parametric longitudinal coupling between a high-impedance superconducting resonator and a semiconductor quantum dot singlet-triplet spin qubit,"Long-distance two-qubit coupling, mediated by a superconducting resonator, is a leading paradigm for performing entangling operations in a quantum computer based on spins in semiconducting materials. Here, we demonstrate a novel, controllable spin-photon coupling based on a longitudinal interaction between a spin qubit and a resonator. We show that coupling a singlet-triplet qubit to a high-impedance superconducting resonator can produce the desired longitudinal coupling when the qubit is driven near the resonator's frequency. We measure the energy splitting of the qubit as a function of the drive amplitude and frequency of a microwave signal applied near the resonator antinode, revealing pronounced effects close to the resonator frequency due to longitudinal coupling. By tuning the amplitude of the drive, we reach a regime with longitudinal coupling exceeding $1$ MHz. This demonstrates a new mechanism for qubit-resonator coupling, and represents a stepping stone towards producing high-fidelity two-qubit gates mediated by a superconducting resonator.",2107.10269v1 2021-07-23,Robust strong coupling architecture in circuit quantum electrodynamics,"We report on a robust method to achieve strong coupling between a superconducting flux qubit and a high-quality quarter-wavelength coplanar waveguide resonator. We demonstrate the progression from the strong to ultrastrong coupling regime by varying the length of a shared inductive coupling element, ultimately achieving a qubit-resonator coupling strength of 655 MHz, $10\%$ of the resonator frequency. We derive an analytical expression for the coupling strength in terms of circuit parameters and also discuss the maximum achievable coupling within this framework. We experimentally characterize flux qubits coupled to superconducting resonators using one and two-tone spectroscopy methods, demonstrating excellent agreement with the proposed theoretical model.",2107.11135v2 2021-08-07,A potential-based construction of the increasing supermartingale coupling,"The increasing supermartingale coupling, introduced by Nutz and Stebegg (Canonical supermartingale couplings, Annals of Probability, 46(6):3351--3398, 2018) is an extreme point of the set of `supermartingale' couplings between two real probability measures in convex-decreasing order. In the present paper we provide an explicit construction of a triple of functions, on the graph of which the increasing supermartingale coupling concentrates. In particular, we show that the increasing supermartingale coupling can be identified with the left-curtain martingale coupling and the antitone coupling to the left and to the right of a uniquely determined regime-switching point, respectively. Our construction is based on the concept of the shadow measure. We show how to determine the potential of the shadow measure associated to a supermartingale, extending the recent results of Beiglb\""{o}ck et al. (The potential of the shadow measure, Electron. Commun. Probab., 27, paper no. 16, 1--12, 2022) obtained in the martingale setting.",2108.03450v3 2021-08-24,Uniform approximation of continuous couplings,"We study the approximation of non-negative multi-variate couplings in the uniform norm while matching given single-variable marginal constraints.",2108.10593v1 2021-09-17,In-Plane Plasmon Coupling in Topological Insulator Bi$_2$Se$_3$ Thin Films,"The surface states of the 3D topological insulator (TI), Bi$_2$Se$_3$, are known to host two-dimensional Dirac plasmon polaritons (DPPs) in the terahertz spectral range. In TI thin films, the DPPs excited on the top and bottom surfaces couple, leading to an acoustic and an optical plasmon mode. Vertical coupling in these materials is therefore reasonable well-understood, but in-plane coupling among localized TI DPPs has yet to be investigated. In this paper, we demonstrate in-plane DPP coupling in TI stripe arrays and show that they exhibit dipole-dipole type coupling. The coupling becomes negligible with the lattice constant is greater than approximately 2.8 times the stripe width, which is comparable to results for in-plane coupling of localized plasmons excited on metallic nanoparticles or graphene plasmon polaritons. This understanding could be leveraged for the creation of TI-based metasurfaces.",2109.08515v1 2021-09-29,All-optical control of phase singularities using strong light-matter coupling,"Strong light-matter coupling occurs when the coupling strength between a confined electromagnetic mode and a molecular resonance exceeds losses to the environment. The study of strong coupling has been motivated by applications such as lasing and the modification of chemical processes. Here we show that strong coupling can be used to create phase singularities. Many nanophotonic structures have been designed to generate phase singularities for use in sensing and optoelectronics. We utilise the concept of cavity-free strong coupling, where electromagnetic modes sustained by a material are strong enough to strongly couple to the material's own molecular resonance, to create phase singularities in a simple thin film of organic molecules. We show that the use of photochromic molecules allows for all-optical control of phase singularities. Our results suggest a new application for strong light-matter coupling and a new, simplified, more versatile pathway to singular phase optics.",2109.14487v1 2021-10-05,Effective potentials in a rotating spin-orbit-coupled spin-1 spinor condensate,"We theoretically study the stationary-state vortex lattice configurations of rotating spin-orbit- and coherently-coupled spin-1 Bose-Einstein condensates trapped in quasi-two-dimensional harmonic potentials. The combined effects of rotation, spin-orbit and coherent couplings are analyzed systematically from the single-particle perspective. Through the single-particle Hamiltonian, which is exactly solvable for one-dimensional coupling, under specific coupling and rotation strengths, we illustrate that a boson in these rotating spin-orbit- and coherently-coupled condensates are subjected to effective toroidal, symmetric double-well, or asymmetric double-well potentials. In the presence of mean-field interactions, using the coupled Gross-Pitaevskii formalism at moderate to high rotation frequencies, the analytically obtained effective potential minima and the numerically obtained coarse-grained density maxima position are in excellent agreement. On rapid rotation, we further find that the spin expectation per particle of an antiferromagnetic spin-1 Bose-Einstein condensate approaches unity indicating a similarity in the response with ferromagnetic spin-orbit-coupled condensates.",2110.02185v3 2021-10-06,Optomagnonics in dispersive media: magnon-photon coupling enhancement at the epsilon-near-zero frequency,"Reaching strong light-matter coupling in solid-state systems has been long pursued for the implementation of scalable quantum devices. Here, we put forward the concept of a platform capable of achieving strong coupling between magnetic excitations (magnons) and optics based in an epsilon-near-zero medium, that's it, a medium in which the permittivity is close to zero. We adopt a phenomenological approach to quantize the electromagnetic field inside a dispersive magnetic medium and obtain a Hamiltonian describing the interaction between photons and magnons and the frequency-dependent coupling. We predict that, in the epsilon-near-zero regime, the single-magnon photon optomagnonic coupling can be comparable to the uniform magnon's frequency for small magnetic volumes. For state-of-the-art illustrative values, this would correspond to achieving the single-magnon strong coupling regime, where the coupling rate is larger than all the decay rates. Finally, we show that the non-linear energy spectrum intrinsic to this coupling regime regime can be probed via the characteristic multiple magnon sidebands in the photon power spectrum.",2110.02984v2 2021-10-08,Nonminimally coupled ultralight axions as cold dark matter,"We consider a nonminimally coupled scalar field as a potential cold dark matter candidate. These models are natural extensions of the ultralight axion models which are based on minimally coupled scalar fields. Such ultralight scalar fields are motivated by string theory and, in particular, have been studied in the context of the axiverse scenario. For a nonminimally coupled field, the scalar-field energy density behaves as radiation at early times, which yields a bound on the coupling constant, $\xi \lesssim 10$, from the primordial nucleosynthesis theory. The first-order perturbations of the nonminimally coupled field with adiabatic initial conditions cause the gravitational potential to decay on large scales. A comparison of the cosmological data with the theoretical matter power spectrum yields the following constraint on the coupling constant: $\xi \lesssim 0.01$. We also consider isocurvature modes in our analysis. We argue that a mix of adiabatic and isocurvature initial conditions for a nonminimally coupled scalar field might allow one to obtain the usual adiabatic CDM power spectrum.",2110.04322v2 2021-10-14,Kuramoto model for populations of quadratic integrate-and-fire neurons with chemical and electrical coupling,"We derive the Kuramoto model (KM) corresponding to a population of weakly coupled, nearly identical quadratic integrate-and-fire (QIF) neurons with both electrical and chemical coupling. The ratio of chemical to electrical coupling determines the phase lag of the characteristic sine coupling function of the KM and critically determines the synchronization properties of the network. We apply our results to investigate chimera states in two coupled populations of identical QIF neurons. We find that the presence of both electrical and chemical coupling is a necessary condition for chimera states to exist. Finally, we numerically demonstrate that chimera states gradually disappear as coupling strengths cease to be weak.",2110.07665v2 2021-12-11,A Multirate Discontinuous-Galerkin-in-Time Framework for Interface-Coupled Problems,"A framework is presented to design multirate time stepping algorithms for two dissipative models with coupling across a physical interface. The coupling takes the form of boundary conditions imposed on the interface, relating the solution variables for both models to each other. The multirate aspect arises when numerical time integration is performed with different time step sizes for the component models. In this paper, we seek to identify a unified approach to develop multirate algorithms for these coupled problems. This effort is pursued though the use of discontinuous-Galerkin time stepping methods, acting as a general unified framework, with different time step sizes. The subproblems are coupled across user-defined intervals of time, called {\it coupling windows}, using polynomials that are continuous on the window. The coupling method is shown to reproduce the correct interfacial energy dissipation, discrete conservation of fluxes, and asymptotic accuracy. In principle, methods of arbitrary order are possible. As a first step, herein we focus on the presentation and analysis of monolithic methods for advection-diffusion models coupled via generalized Robin-type conditions. The monolithic methods could be computed using a Schur-complement approach. We conclude with some discussion of future developments, such as different interface conditions and partitioned methods.",2112.06099v1 2022-01-27,Superfluid transition temperature and fluctuation theory of spin-orbit and Rabi-coupled fermions with tunable interactions,"We obtain the superfluid transition temperature of equal Rashba-Dresselhaus spin-orbit and Rabi-coupled Fermi superfluids, from the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) regimes in three dimensions for tunable $s$-wave interactions. In the presence of Rabi coupling, we find that spin-orbit coupling enhances (reduces) the critical temperature in the BEC (BCS) limit. For fixed interactions, we show that spin-orbit coupling can convert a first-order (discontinuous) phase transition into a second-order (continuous) phase transition, as a function of Rabi coupling. We derive the Ginzburg-Landau free energy to sixth power in the superfluid order parameter to describe both continuous and discontinuous phase transitions as a function of spin-orbit and Rabi couplings. Lastly, we develop a time-dependent Ginzburg-Landau fluctuation theory for an arbitrary mixture of Rashba and Dresselhaus spin-orbit couplings at any interaction strength.",2201.11823v2 2022-01-28,Operator relationship between conventional coupled cluster and unitary coupled cluster,"The chemistry community has long sought the exact relationship between the conventional and the unitary coupled cluster ansatz for a single-reference system, especially given the interest in performing quantum chemistry on quantum computers. In this work, we show how one can use the operator manipulations given by the exponential disentangling identity and the Hadamard lemma to relate the factorized form of the unitary coupled-cluster approximation to a factorized form of the conventional coupled cluster approximation (the factorized form is required, because some amplitudes are operator-valued and do not commute with other terms). By employing the Trotter product formula, one can then relate the factorized form to the standard form of the unitary coupled cluster ansatz. The operator dependence of the factorized form of the coupled cluster approximation can also be removed at the expense of requiring even more higher-rank operators, finally yielding the conventional coupled cluster. The algebraic manipulations of this approach are daunting to carry out by hand, but can be automated on a computer for small enough systems.",2201.11881v1 2022-02-10,Double inflation via non-minimally coupled spectator,"We argue that double inflation may occur when a spectator field is non-minimally coupled to gravity. As a concrete example, we study a two-field inflationary model where the initial spectator field is non-minimally coupled to gravity while the initial inflaton field is minimally coupled. The non-minimal coupling results in the growth of the spectator field which, in turn, drives the second stage of inflation in a significant region of parameter space. The isocurvature fluctuations originating from the spectator field source adiabatic ones, and hence the spectator non-minimal coupling can modify the inflationary predictions for the spectral index and the tensor-to-scalar ratio even though the initial inflaton field is minimally coupled to gravity. We explicitly show that quadratic chaotic inflation can become viable by the introduction of the spectator non-minimal coupling.",2202.04869v1 2022-02-22,Maximizing the electromomentum coupling in piezoelectric laminates,"Asymmetric piezoelectric composites exhibit coupling between their macroscopic linear momentum and electric field, a coupling that does not appear at the microscopic scale. This electromomentum coupling constitutes an additional knob to tailor the dynamic response of the medium, analogously to the Willis coupling in elastic composites. Here, we employ topology- and free material optimization approaches to maximize the electromomentum coupling of periodic piezoelectric laminates in the low frequency, long-wavelength limit. We find that the coupling can be enhanced by orders of magnitude, depending on the degrees of freedom in the optimization process. The optimal compositions that we find provide guidelines for the design of metamaterials with maximum electromomentum coupling, paving the way for their integration in wave control applications.",2202.10683v1 2022-04-15,Quantum phases of spin-orbital-angular-momentum coupled bosonic gases in optical lattices,"Spin-orbit coupling plays an important role in understanding exotic quantum phases. In this work, we present a scheme to combine spin-orbital-angular-momentum (SOAM) coupling and strong correlations in ultracold atomic gases. Essential ingredients of this setting is the interplay of SOAM coupling and Raman-induced spin-flip hopping, engineered by lasers that couples different hyperfine spin states. In the presence of SOAM coupling only, we find rich quantum phases in the Mott-insulating regime, which support different types of spin defects such as spin vortex and composite vortex with antiferromagnetic core surrounded by the outer spin vortex. Based on an effective exchange model, we find that these competing spin textures are a result of the interplay of Dzyaloshinskii-Moriya and Heisenberg exchange interactions. In the presence of both SOAM coupling and Raman-induced spin-flip hopping, more many-body phases appear, including canted-antiferromagnetic and stripe phases. Our prediction suggests that SOAM coupling could induce rich exotic many-body phases in the strongly interacting regime.",2204.07323v2 2022-05-05,A BRST view of the spontaneous symmetry breaking,"After the phase transition of a Grand Unified Theory (GUT), its single coupling splits into the couplings of the basic interactions. On the other side, the measurement of the Weinberg mixing angle in the eletroweak theory determines that the couplings associated to the SU(2) and U(1) symmetries were already distinct in its symmetric phase, before the electroweak breaking. This picture is consistent as we understand that such couplings evolve independently with the energy scale, meeting a common point together with the strong interaction coupling at the GUT scale. From a BRST symmetry point of view, this implies that each independent coupling should be associated to independent cocycles defined on a cohomological basis. The problem is that, before the GUT symmetry breaking, the BRST operator associated to this symmetric phase predicts a single Yang-Mills coupling. This sets the question of what should be the BRST operator of the asymmetric phase, that would allow for the splitting of this coupling but at the same time remain compatible with the BRST operator of the symmetric phase. In this work we proceed to answer this question.",2205.02903v1 2022-05-15,A tower of hidden sectors: a general treatment and physics implications,"An analysis of a tower of hidden sectors coupled to each other, with one of these hidden sectors coupled to the visible sector, is given and the implications of such couplings on physics in the visible sector are investigated. Thus the analysis considers $n$ number of hidden sectors where the visible sector couples only to hidden sector 1, while the latter couples also to hidden sector 2, and the hidden sector 2 couples to hidden sector 3 and so on. A set of successively feeble couplings of the hidden sectors to the visible sector are generated in such a set up. In general each of these sectors live in a different heat bath. We develop a closed form set of coupled Boltzmann equations for the correlated evolution of the temperatures and number densities of each of the heat baths. We then apply the formalism to a simplified model with scalar portals between the different sectors. Predictions related to dark matter direct detection experiments and future CMB probes of dark radiation are made.",2205.07316v2 2022-07-12,Photonic heat transport from weak to strong coupling,"Superconducting circuits provide a favorable platform for quantum thermodynamic experiments. An important component for such experiments is a heat valve, i.e. a device which allows one to control the heat power flowing through the system. Here we theoretically study the heat valve based on a superconducting quantum interference device (SQUID) coupled to two heat baths via two resonators. The heat current in such system can be tuned by magnetic flux. We investigate how does the heat current modulation depend on the coupling strength g between the SQUID and the resonators. In the weak coupling regime the heat current modulation grows as g2, but, surprisingly, at the intermediate coupling it can be strongly suppressed. This effect is linked to the resonant nature of the heat transport at weak coupling, where the heat current dependence on the magnetic flux is a periodic set of narrow peaks. At the intermediate coupling, the peaks become broader and overlap, thus reducing the heat modulation. At very strong coupling the heat modulation grows again and finally saturates at a constant value.",2207.05586v1 2022-07-13,Nanoscale engineering of optical strong coupling inside metals,"Optical polaritons appear when a material excitation strongly couples to the optical mode. Such strong coupling between molecular transitions and optical cavities results in far-reaching opportunities in modifying fundamental properties of chemical matter. More recently an exciting prospect of cavity-free polaritons has emerged by matter sustaining the optical mode with its geometry. Here we show how strong coupling of the interband transition and surface plasmons can be engineered in nickel at the nanoscale to realize cavity-free optical polaritons inside metals. Using electron energy-loss spectroscopy, we demonstrate that in thin films and nanoantennas the propagation and radiation losses result in a broadening of the plasmon linewidth and a transition from strong to weak coupling. Further, higher-order plasmon resonances couple to the interband transition, and the multipolar coupled states acquire the field profile of the plasmon. Our results provide a fundamental understanding of plasmon-interband coupling in metals and establish the base for the design of unforeseen photocatalytic and magneto-optical nanosystems.",2207.05988v1 2022-07-24,Supermartingale shadow couplings: the decreasing case,"For two measures $\mu$ and $\nu$ that are in convex-decreasing order, Nutz and Stebegg (Canonical supermartingale couplings, Ann. Probab., 46(6):3351--3398, 2018) studied the optimal transport problem with supermartingale constraints and introduced two canonical couplings, namely the increasing and decreasing transport plans, that are optimal for a large class of cost functions. In the present paper we provide an explicit construction of the decreasing coupling $\pi^D$ by establishing a Brenier-type result: (a generalised version of) $\pi^D$ concentrates on the graphs of two functions. Our construction is based on the concept of the supermartingale \textit{shadow} measure and requires a suitable extension of the results by Juillet (Stability of the shadow projection and the left-curtain coupling, Ann. Inst. H. Poincar\'e Probab. Statist., 52(4):1823--1843, November 2016) and Beiglb\""ock and Juillet (Shadow couplings, Trans. Amer. Math. Soc., 374:4973--5002, 2021) established in the martingale setting. In particular, we prove the stability of the supermartingale shadow measure with respect to initial and target measures $\mu,\nu$, introduce an infinite family of lifted supermartingale couplings that arise via shadow measure, and show how to explicitly determine the `martingale points' of each such coupling.",2207.11732v1 2022-09-01,Charting the Higgs self-coupling boundaries,"Could new physics first manifest itself in Higgs self-coupling measurements? In other words, how large could deviations in the Higgs self-coupling be, if other Higgs and electroweak measurements are compatible with Standard Model predictions? Using theoretical arguments supported by concrete models we derive a bound on the ratio of self-coupling to single-Higgs coupling deviations in ultraviolet completions of the Standard Model where parameters are not fine-tuned. Broadly speaking, a one-loop hierarchy is allowed. We thus stress that self-coupling measurements at the LHC and future colliders probe uncharted parameter space, presenting discovery potential even in the absence of emerging hints in single-Higgs coupling measurements. For instance, if other observables show less than two-sigma deviations by the end of the LHC programme, the Higgs self-coupling deviations could still exceed 200% in the models discussed, without introducing fine-tuning of ultraviolet parameters.",2209.00666v3 2022-10-20,Optimal Markovian coupling for finite activity Lévy processes,"We study optimal Markovian couplings of Markov processes, where the optimality is understood in terms of minimization of concave transport costs between the time-marginal distributions of the coupled processes. We provide explicit constructions of such optimal couplings for one-dimensional finite-activity L\'evy processes (continuous-time random walks) whose jump distributions are unimodal but not necessarily symmetric. Remarkably, the optimal Markovian coupling does not depend on the specific concave transport cost. To this end, we combine McCann's results on optimal transport and Rogers' results on random walks with a novel uniformization construction that allows us to characterize all Markovian couplings of finite-activity L\'evy processes. In particular, we show that the optimal Markovian coupling for finite-activity L\'evy processes with non-symmetric unimodal L\'evy measures has to allow for non-simultaneous jumps of the two coupled processes.",2210.11251v1 2022-12-08,Electric control of spin states in frustrated triangular molecular magnets,"Frustrated triangular molecular magnets are a very important class of magnetic molecules since the absence of inversion symmetry allows an external electric field to couple directly with the spin chirality that characterizes their ground state. The spin-electric coupling in these molecular magnets leads to an efficient and fast method of manipulating spin states, making them an exciting candidate for quantum information processing. The efficiency of the spin-electric coupling depends on the electric dipole coupling between the chiral ground states of these molecules. In this paper, we report on first-principles calculations of spin-electric coupling in $\{V_3\}$ triangular magnetic molecule. We have explicitly calculated the spin-induced charge redistribution within the magnetic centers that is responsible for the spin-electric coupling. Furthermore, we have generalized the method of calculating the strength of the spin-electric coupling to calculate any triangular spin 1/2 molecule with $C_3$ symmetry and have applied it to calculate the coupling strength in $\{V_{15}\}$ molecular magnets.",2212.04066v1 2023-01-27,Electric field control of RKKY coupling through solid-state ionics,"Placing a suitable spacer layer between two magnetic layers can lead to an interaction between the magnetic layers known as Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling. Controlling RKKY coupling, particularly the ability to switch between ferromagnetic and antiferromagnetic coupling, would enable novel magnetic data storage devices. By combining solid-state Li ion battery technology with an out-of-plane magnetized Co/Pt-based stack coupled through a Ru interlayer we investigate the effects of the insertion of Li ions on the magnetic properties of the stack. The RKKY coupling and its voltage dependence is measured as a function of the Ru interlayer thickness, along with the effects of repeated voltage cycling. The Li ions both change the amplitude of the RKKY coupling and its phase, leading to the ability to switch the RKKY coupling between ferromagnetic and antiferromagnetic with applied voltages.",2301.11626v1 2023-02-07,Emergent dynamics of the generalized Winfree model]{Emerging asymptotic patterns in a Winfree ensemble with higher-order couplings,"The Winfree model is a phase-coupled synchronization model which simplifies pulse-coupled models such as the Peskin model on pacemaker cells. It is well-known that the Winfree ensemble with the first-order coupling exhibits discrete asymptotic patterns such as incoherence, locking and death depending on the coupling strength and variance of natural frequencies. In this paper, we further study higher-order couplings which makes the dynamics more close to the behaviors of the Peskin model. For this, we propose several sufficient frameworks for asymptotic patterns compared to the first-order coupling model. Our proposed conditions on the coupling strength, natural frequencies and initial data are independent of the number of oscillators so that they can be applied to the corresponding mean-field model. We also provide several numerical simulations and compare them with analytical results.",2302.03179v1 2023-02-21,The Benefit of Uncertainty Coupling in Robust and Adaptive Robust Optimization,"Despite the modeling power for problems under uncertainty, robust optimization (RO) and adaptive robust optimization (ARO) can exhibit too conservative solutions in terms of objective value degradation compared to the nominal case. One of the main reasons behind this conservatism is that, in many practical applications, uncertain constraints are directly designed as constraint-wise without taking into account couplings over multiple constraints. In this paper, we define a coupled uncertainty set as the intersection between a constraint-wise uncertainty set and a coupling set. We study the benefit of coupling in alleviating conservatism in RO and ARO. We provide theoretical tight and computable upper and lower bounds on the objective value improvement of RO and ARO problems under coupled uncertainty over constraint-wise uncertainty. In addition, we relate the power of adaptability over static solutions with the coupling of uncertainty set. Computational results demonstrate the benefit of coupling in applications.",2302.10369v1 2023-03-13,Collective synchronization of dissipatively-coupled noise-activated processes,"A system of two enzymes mechanically coupled to each other in a viscous medium was recently studied, and conditions for obtaining synchronization and an enhanced average rate of the thermally-activated catalytic reactions of the enzymes were identified. The transition to synchronization occurred as the result of a global bifurcation in the underlying dynamical system. Here, we extend and generalize this idea to an arbitrary number of noise-activated cyclic processes, or oscillators, that are all coupled to each other via a dissipative coupling. The $N$ coupled oscillators are described by $N$ phase coordinates driven in a tilted washboard potential. At low $N$ and strong coupling, we find synchronization as well as an enhancement in the average speed of the oscillators. In the large $N$ regime, we show that the collective dynamics can be described through a mean-field theory, which predicts a great enhancement in the average speed. In fact, beyond a critical value of the coupling strength, noise activation becomes irrelevant and the dynamics switch to an effectively deterministic ""running"" mode. Finally, we study the stochastic thermodynamics of the coupled oscillators, in particular their performance with regards to the thermodynamic uncertainty relation.",2303.07277v1 2023-04-10,Synchronous control study of Chua circuit system via capacitive closed-loop coupling,"Synchronous control of nonlinear circuits is of great importance in many fields. In this paper, a capacitor is used for closed-loop coupling of three dual-vortex attractor Chua circuits with the same circuit parameters and different initial conditions, and the corresponding synchronization processes and synchronization effects are investigated. It is found that, for the capacitor, the closed-loop coupling can completely synchronize the three Chua circuits. And there exists a critical coupling strength $\delta_{critical}^C$ that can be calculated, and when the coupling strength is between the critical coupling strength $\delta_{critical}^C$ and the upper coupling strength $\delta_{max}^C$, the three circuits can be completely synchronized very quickly. Moreover, the results show that the unidirectional coupling cannot make the circuit system completely synchronized. Finally, we also verify the correctness of the calculation by circuit simulation experiments.",2304.04568v1 2023-04-19,Cavity magnomechanical coupling with coupled magnon modes in a synthetic antiferromagnet,"On-chip cavity magnomechanics is an emerging field exploring acoustic and magnonic functionalities of various ferromagnetic materials and structures using strongly confined phonons. It is expected that such cavity magnomechanics can be extended to multilayer ferromagnets, especially synthetic antiferromagnets (SAFs) that exhibit zero net magnetization through interlayer exchange coupling. However, the conventional theoretical framework for a single ferromagnet cannot be used directly because of the antiferromagnetic magnetization dynamics associated with the interlayer exchange coupling. In this paper, we theoretically investigate phonon-magnon coupling with a three-layer SAF. Our formulation of the phonon-magnon coupling constants reveals that the acoustic (optical) magnon mode dominantly couples to the cavity phonon when the magnetization angles in the two ferromagnetic layers are antiparallel (orthogonal). Moreover, numerical calculations including the effects of dipole-dipole interactions and in-plane uniaxial magnetic anisotropy allow us to predict phonon frequency shifts and linewidth broadening that can be detected in experiments. These theoretical insights would greatly help us to make a strategy for bringing the system into the strong coupling regime and to devise novel control protocols in analogy to cavity quantum electrodynamics and cavity optomechanics.",2304.09458v2 2023-04-30,Non-decreasing martingale couplings,"For many examples of couples $(\mu,\nu)$ of probability measures on the real line in the convex order, we observe numerically that the Hobson and Neuberger martingale coupling, which maximizes for $\rho=1$ the integral of $|y-x|^\rho$ with respect to any martingale coupling between $\mu$ and $\nu$, is still a maximizer for $\rho\in(0,2)$ and a minimizer for $\rho>2$. We investigate the theoretical validity of this numerical observation and give rather restrictive sufficient conditions for the property to hold. We also exhibit couples $(\mu,\nu)$ such that it does not hold. The support of the Hobson and Neuberger coupling is known to satisfy some monotonicity property which we call non-decreasing. We check that the non-decreasing property is preserved for maximizers when $\rho\in(0,1]$. In general, there exist distinct non-decreasing martingale couplings, and we find some decomposition of $\nu$ which is in one-to-one correspondence with martingale couplings non-decreasing in a generalized sense.",2305.00565v1 2023-05-17,Wave Function Renormalization and Flow of Couplings in Asymptotically Safe Quantum Gravity,"The importance of the proper treatment of the wave function renormalization in the renormalization group analysis of quantum gravity is pointed out. The renormalization factor, sometimes called an inessential coupling, can be used to fix any one of the coupling constants, with the exception of the coupling constants that remain unchanged by the rescaling of the field. Choosing to fix the cosmological constant, we propose to use a new regulator to obtain the renormalization group equations for invariant couplings which tell us the flow of the Newton and $R^2$ couplings. We find that the Newton coupling reaches a nontrivial ultraviolet fixed point (FP) and becomes small in the low energy, but find only asymptotically free FP of the $R^2$ couplings for the higher-derivative gauge fixing and regulator. For the asymptotically free FP, we find that both of the two independent terms are relevant operators in the high energy. It is noted that the existence of nontrivial FPs may depend on the choice of the gauge and regulator.",2305.10591v2 2023-05-18,Optimal estimation of Dimension-8 Neutral Triple Gauge Couplings at $e^+ e^-$ Colliders,"We investigate the measurement of non-standard ZZV (V = {\gamma}, Z) couplings through Z-boson pair production at the $e^+ e^-$ colliders. We adopt Standard Model Effective Field Theory (SMEFT) approach to study these anomalous neutral triple gauge couplings. There are one CP-conserving and three CP-violating dim-8 SMEFT operators that contribute to ZZV couplings. Using optimal observable technique, the sensitivity of these NP couplings has been estimated and then we compare it with the latest experimental limits on dim-8 couplings at CERN LHC. Effect of beam polarization and correlations among CP-violating ZZV couplings are discussed. Comparison of statistical limits of new physics couplings between optimal observable technique and contemporary cut-based analysis has also been studied in detail.",2305.11266v2 2023-07-02,Effective action of heterotic string theory at order $α'^2$,"Upon examining the effective action of the heterotic string theory at order $\alpha'^2$, an inconsistency between the Chern-Simons coupling $\Omega^2$ and T-duality has been discovered. To address this issue, we introduce 60 parity-even independent geometrical couplings involving the $B$-field, metric, and dilation at the same order, each with arbitrary coefficients. To ensure the invariance of these couplings under T-duality, we consider the Miessner action for the couplings at order $\alpha'$ and rigorously determine the coefficients of the 60 couplings in terms of the Chern-Simons coupling. Notably, it is found that the coefficients of the Riemann cubed terms must be zero, which aligns with the results of S-matrix calculations. Additionally, the parity odd couplings at order $\alpha'^2$ are obtained through T-duality. Overall, our analysis successfully resolves the inconsistency between the Chern-Simons coupling and T-duality, providing a more comprehensive understanding of the behavior of the heterotic string theory at order $\alpha'^2$.",2307.00544v2 2023-08-03,Tuning of resonant doublets in coupled optical cavities,"The mode profile of a coupled optical cavity often exhibits a resonant doublet, which arises from the strong coupling between its sub-cavities. Traditional readout methods rely on setting fields of different frequencies to be resonant in either sub-cavity, which is challenging in the case of strong coupling. In this regime, the coupled cavity behaves as a single resonator, and a field must be resonant in all its parts. Consequently, specialized sensing schemes are necessary to control strongly coupled cavities. To address this issue, we propose a novel technique for the relative measurement of the degrees of freedom of a strongly coupled cavity. Our approach enables simultaneous frequency stabilization and fine-tuning of frequency splitting in the resonant doublet. Overall, our proposed technique offers a promising solution to control the properties of coupled cavities, facilitating advanced applications in the fields of gravitational-wave detection, quantum cavity optomechanics, and other related areas.",2308.02574v1 2023-08-08,Vibrational coupling to quasi-bound states in the continuum under tailored coupling conditions,"Photonic resonance modes can be spectrally coupled to the vibrational modes of molecules in the mid-infrared regime through interactions between localized electric fields and nearby molecules. According to recent studies, radiative loss engineering of coupled systems is a promising approach for tailoring coupling conditions and enhancing the molecular signals. However, this strategy has only been realized using the localized surface plasmon resonances of metal nanostructures, which suffer from increased ohmic loss in the mid-infrared region and face serious limitations in achieving high quality (Q) factors. In this study, we adopt silicon-based metasurfaces formed on silicon-on-insulator wafers to achieve high Q factors and tune the coupling conditions between the quasi-bound states in the continuum (qBICs) and molecular vibrations. The coupling between the resonance mode and polymethyl methacrylate molecules is tailored from weak to strong coupling regimes by simply changing the structural asymmetry parameter and utilizing the intrinsically high Q factors of the qBIC modes. In addition, we identify the optimal asymmetry parameter that maximizes the enhanced molecular signal, opening a route toward realizing highly sensitive surface-enhanced infrared spectroscopy using complementary metal-oxide semiconductor compatible all-dielectric materials.",2308.04630v1 2023-09-11,Topological transitions in dissipatively coupled Su-Schrieffer-Heeger models,"Non-Hermitian topological phenomena have gained much interest among physicists in recent years. In this paper, we expound on the physics of dissipatively coupled Su-Schrieffer-Heeger (SSH) lattices, specifically in systems with bosonic and electrical constituents. In the context of electrical circuits, we demonstrate that a series of resistively coupled LCR circuits mimics the topology of a dissipatively coupled SSH model. In addition, we foreground a scheme to construct dissipatively coupled SSH lattices involving a set of non-interacting bosonic oscillators weakly coupled to engineered reservoirs of modes possessing substantially small lifetimes when compared to other system timescales. Further, by activating the coherent coupling between bosonic oscillators, we elucidate the emergence of non-reciprocal dissipative coupling which can be controlled by the phase of the coherent interaction strength precipitating in phase-dependent topological transitions and skin effect. Our analyses are generic, apropos of a large class of systems involving, for instance, optical and microwave settings, while the circuit implementation represents the most straightforward of them.",2309.05479v1 2023-09-14,Coupling Constants as Conserved Charges in Black Hole Thermodynamics,"In a generic theory of gravity coupled to matter fields, the Smarr formula and the first law of thermodynamics of black holes do not work properly if the contributions of the coupling constants defining the theory are not incorporated. However, these couplings, such as the cosmological constant or the dimensionful parameters that appear in the Lagrangian, are fixed parameters defining the theory; and they cannot be varied. Here, we present a robust method, applicable to any covariant Lagrangian, that changes the role of the couplings from the constants in a theory to the free parameters in solutions. To this end, for each one of the couplings in a theory, a pair of auxiliary scalar and gauge fields is introduced. The couplings are shown to be conserved charges of the global part of the implemented gauge symmetry. Besides, their conjugate chemical potentials are defined as the electric potential of the corresponding gauge fields on the black hole horizon. Using this method, we systematically extend the first law and the Smarr formula by coupling conserved charges and their conjugate potentials. The thermodynamics of a black hole solution in a quadratic gravity theory is given as an example.",2309.07634v1 2023-10-10,Kerr black hole shadows from the axion-photon coupling,"We have investigated the motion for photons in the Kerr black hole spacetime under the axion-photon coupling. The birefringence phenomena arising from the axion-photon coupling can be negligible in the weak coupling approximation because the leading-order contributions to the equations of motion come from the square term of the coupling parameter. We find that the coupling parameter makes the size of shadows slightly increase for arbitrary spin parameter. For the rapid rotating black hole case with a larger coupling, we find that there exist a pedicel-like structure appeared in the left of the D-type like shadows.Comparing the shadow size of the Kerr black hole with the shadow size of the Sgr A* and M87* black holes, we find that there is room for such a theoretical model of the axion-photon coupling.",2310.06490v3 2023-10-24,String breaking and running coupling of $\rm Q\bar{Q}$ in a rotating media from holography,"Through gravity/gauge duality, the string breaking and running coupling constant of heavy quark-antiquark pair are investigated in the rotating background. For the meson decay mode $\rm Q\bar{Q} \rightarrow Q \bar{q}+\bar{Q} q$, we discuss the string breaking and running coupling in the parallel and transverse case. It is found that the parallel case has a more significant on string breaking and running coupling constant than the transverse case in the confined phase. The string-breaking distance and the maximum value of running coupling will decrease with the increase of angular velocity in the parallel case. Besides, we also investigate the running coupling and screening distance at finite angular velocity in the deconfined phase. It is found that the maximum values of the running coupling and screening distance are decreasing functions of angular velocity. The parallel case has a more significant influence on the running coupling and screening distance than the transverse case in the deconfined phase.",2310.15609v1 2023-11-07,Non-Hermitian skin effect and nonreciprocity induced by dissipative couplings,"We study the mechanism for realizing non-Hermitian skin effect (NHSE) via dissipative couplings, in which the left-right couplings have equal strengths but the phases do not satisfy the complex conjugation. Previous realizations of NHSE typically require unequal left-right couplings or on-site gain and loss. In this work we find that when combined with the multichannel interference provided by a periodic dissipative-coherent coupling structure, the dissipative couplings can lead to unequal left-right couplings, inducing NHSE. Moreover, we show that the non-Hermiticity induced by dissipative couplings can be fully transformed into nonreciprocity-type non-Hermiticity without bringing extra gain-loss-type non-Hermiticity. Thus, this mechanism enables unidirectional energy transmission without introducing additional insertion loss. Our work opens a new avenue for the study of non-Hermitian topological effects and the design of directional optical networks.",2311.03803v2 2023-12-07,Stiff deployable structures via coupling of thick Miura-ori tubes along creases,"Origami-based structures play an important role in the realization of deployable mechanisms and unique mechanical properties via programmable deformation by folding. Among origami-based structures, tessellation by the coupling of origami tubes enriches the variations in geometry and mechanical properties. However, thickness accommodation is a critical problem in engineering applications involving the coupling of thick origami tubes. To solve this problem, this study proposes the coupling of thick Miura-ori tubes along the creases for facile fabrication, which sustains the one-degree-of-freedom (DOF) motion of thick Miura-ori tubes owing to the local mirror symmetry around the coupling interfaces. Furthermore, the coupling method contributes to the high stiffness of the coupled Miura-ori tubes, as evidenced by the wide gap in the eigenvalues between the one-DOF mode and the elastic modes obtained by the bar-and-hinge models. Finally, meter-scale coupled Miura-ori tubes were fabricated to demonstrate one-DOF motion and high stiffness. The findings of this study enable the rapid construction of structures by one-DOF motion and enhancement of transportability via flat-foldability.",2312.04048v1 2023-12-27,Topological phase transitions induced by the variation of exchange couplings in graphene,"We consider a modified graphene model under exchange couplings. Various quantum anomalous phases are known to emerge under uniform or staggered exchange couplings. We introduce the twist between the orientations of two sublattice exchange couplings, which is useful for examining how such topologically nontrivial phases under different types of exchange couplings are connected to one another. The phase diagrams constructed by the variation of exchange coupling strengths and twist angles exhibit rich structures of successive topological transitions. We analyze the emergence of peculiar phases in terms of the evolution of the energy dispersions. Perturbation schemes applied to the energy levels turn out to reproduce well phase boundary lines up to moderate values of the twist angle. We also discover two close topological transitions under uniform exchange couplings, which is attributed to the interplay of the trigonal-warping deformation due to Rashba spin-orbit coupling and the staggered sublattice potential. Finally the implications of Berry curvature structure and topological excitations in real and pseudo spin textures are discussed.",2312.16625v2 2024-01-19,Extremely strong spin-orbit coupling effect in light element altermagnetic materials,"Spin-orbit coupling is a key to realize many novel physical effects in condensed matter physics, but the mechanism to achieve strong spin-orbit coupling effect in light element antiferromagnetic compounds has not been explored. In this work, based on symmetry analysis and the first-principles electronic structure calculations, we demonstrate that strong spin-orbit coupling effect can be realized in light element altermagnetic materials, and propose a mechanism for realizing the corresponding effective spin-orbit coupling. This mechanism reveals the cooperative effect of crystal symmetry, electron occupation, electronegativity, electron correlation, and intrinsic spin-orbit coupling. Our work not only promotes the understanding of light element compounds with strong spin-orbit coupling effect, but also provides an alternative for realizing light element compounds with an effective strong spin-orbit coupling.",2401.11065v1 2024-02-14,Sign of the $hZZ$ coupling and implication for new physics,"The magnitudes of the couplings of the scalar resonance at 125 GeV with the SM particles are found to be consistent with those of the SM Higgs boson. However, the signs are not experimentally determined in most of the cases, a prime example being that with the $Z$-boson pair. In other words, $\kappa_Z^h$, the ratio of the couplings of the actual 125 GeV resonance with $ZZ$ and that of the SM Higgs boson with the same, is consistent with both $+1$ and $-1$, the latter being the `wrong-sign'. We argue that the wrong-sign $hZZ$ coupling will necessitate the intervention of new physics below $\mathcal{O}\left(620\right)$ GeV to safeguard the underlying theory from unitarity violation. The strength of the new nonstandard couplings can be derived from the unitarity sum rules, which are comparable to the SM-Higgs couplings in magnitude. Thus the strong limits from the direct searches at the LHC can help us rule out the existence of such nonstandard particles with unusually large couplings thereby disfavoring the possibility of a wrong-sign $hZZ$ coupling.",2402.09352v1 2024-04-08,Linear and Nonlinear Coupling of Twin-Resonators with Kerr Nonlinearity,"Nonlinear effects in microresonators are efficient building blocks for all-optical computing and telecom systems. With the latest advances in microfabrication, coupled microresonators are used in a rapidly growing number of applications. In this work, we investigate the coupling between twin-resonators in the presence of Kerr-nonlinearity. We use an experimental setup with controllable coupling between two high-Q resonators and discuss the effects caused by the simultaneous presence of linear and non-linear coupling between the optical fields. Linear-coupling-induced mode splitting is observed at low input powers, with the controllable coupling leading to a tunable mode splitting. At high input powers, the hybridized resonances show spontaneous symmetry breaking (SSB) effects, in which the optical power is unevenly distributed between the resonators. Our experimental results are supported by a detailed theoretical model of nonlinear twin-resonators. With the recent interest in coupled resonator systems for neuromorphic computing, quantum systems, and optical frequency comb generation, our work provides important insights into the behavior of these systems at high circulating powers.",2404.05646v1 1999-04-09,Scaling solutions in general non-minimal coupling theories,"A class of generalized non-minimal coupling theories is investigated, in search of scaling attractors able to provide an accelerated expansion at the present time. Solutions are found in the strong coupling regime and when the coupling function and the potential verify a simple relation. In such cases, which include power law and exponential functions, the dynamics is independent of the exact form of the coupling and the potential. The constraint from the time variability of $G$, however, limits the fraction of energy in the scalar field to less than 4% of the total energy density, and excludes accelerated solutions at the present.",9904120v1 2005-02-19,Quintessence models of Dark Energy with non-minimal coupling,"We explore quintessence models of dark energy which exhibit non-minimal coupling between the dark matter and the dark energy components of the cosmic fluid. The kind of coupling chosen is inspired in scalar-tensor theories of gravity. We impose a suitable dynamics of the expansion allowing to derive exact Friedmann-Robertson-Walker solutions once the coupling function is given as input. Coupling functions that lead to self-interaction potentials of the single and double exponential types are the target of the present investigation. The stability and existence of the solutions is discussed in some detail. The models are tested against the observational evidence.",0502383v1 2005-09-02,A toy model for coupling accretion disk oscillations to the neutron star spin,"Lee, Abramowicz & Kluzniak (2004) demonstrated numerically that rotation of neutron star couples with oscillations of its accretion disk, and excites resonances. No specific coupling was assumed, but magnetic field was suggested as the most likely one. Following this idea, we show (Petri 2005) that if the neutron star is non-axially symmetric and rotating, its gravity may provide the coupling and excite resonances. Here, we return to the original suggestion that the coupling is of a magnetic origin, and demonstrate how does it work in terms of a simple, analytic toy-model.",0509047v1 1998-01-07,Driven Maps and the Emergence of Ordered Collective Behavior in Globally Coupled Maps,"A method to predict the emergence of different kinds of ordered collective behaviors in systems of globally coupled chaotic maps is proposed. The method is based on the analogy between globally coupled maps and a map subjected to an external drive. A vector field which results from this analogy appears to govern the transient evolution of the globally coupled system. General forms of global couplings are considered. Some simple applications are given.",9801005v1 1993-08-20,Phase separation and pairing in coupled chains and planes,"A generalization of the $t-J$ model in a system of two coupled chains or planes is studied by numerical diagonalization of small clusters. In particular, the effect of density fluctuations between these one- or two-dimensional coupled layerson intralayer phase separation and pairing is analyzed. The most robust signals of superconductivity are found at quarter filling for couplings just before the fully interlayer phase separated regime. The possibility of an enhancement of the intralayer superconducting pairing correlations by the interlayer couplings is investigated.",9308028v2 1994-10-10,Effective chiral-spin Hamiltonian for odd-numbered coupled Heisenberg chains,"An $L \times \infty$ system of odd number of coupled Heisenberg spin chains is studied using a degenerate perturbation theory, where $L$ is the number of coupled chains. An effective chain Hamiltonian is derived explicitly in terms of two spin half degrees of freedom of a closed chain of $L$ sites, valid in the regime the inter-chain coupling is stronger than the intra-chain coupling. The spin gap has been calculated numerically using the effective Hamiltonian for $L=3,5,7,9$ for a finite chain up to ten sites. It is suggested that the ground state of the effective Hamiltonian is correlated, by examining variational states for the effective chiral-spin chain Hamiltonian.",9410030v1 1997-03-20,Complex-Temperature Phase Diagrams of 1D Spin Models with Next-Nearest-Neighbor Couplings,"We study the dependence of complex-temperature phase diagrams on details of the Hamiltonian, focusing on the effect of non-nearest-neighbor spin-spin couplings. For this purpose, we consider a simple exactly solvable model, the 1D Ising model with nearest-neighbor (NN) and next-to-nearest-neighbor (NNN) couplings. We work out the exact phase diagrams for various values of $J_{nnn}/J_{nn}$ and compare these with the case of pure nearest-neighbor (NN) couplings. We also give some similar results for the 1D Potts model with NN and NNN couplings.",9703187v1 1998-02-13,Antiferromagnetic interlayer exchange coupling across an amorphous metallic spacer layer,"By means of magneto-optical Kerr effect we observe for the first time antiferromagnetic coupling between ferromagnetic layers across an amorphous metallic spacer layer. Biquadratic coupling occurs at the transition from a ferromagnetically to an antiferromagnetically coupled region. Scanning tunneling microscopy images of all involved layers are used to extract thickness fluctuations and to verify the amorphous state of the spacer. The observed antiferromagnetic coupling behavior is explained by RKKY interaction taking into account the amorphous structure of the spacer material.",9802148v1 1998-04-20,Crossover from Weak- to Strong-Coupling Superconductivity and to Normal State with Pseudogap,"For an electron gas with a $ \delta $-function attraction we investigate the crossover from weak-coupling to strong-coupling superconductivity as well as normal state near the temperature $T^*$, at which the strong coupling produces a pseudogap in the energy spectrum due to the binding of electron pairs. We present curves for the behavior of the superconductive transition temperature, the gap formation temperature, the gap size and several thermodynamic quantities as functions of coupling strength and temperature, both in two and three dimensions.",9804206v3 1998-10-16,Coupling of intrinsic Josephson oscillations in layered superconductors by charge fluctuations,"The coupling of Josephson oscillations in layered superconductors is studied with help of a tunneling Hamiltonian formalism. The general form of the current density across the barriers between the superconducting layers is derived. The induced charge fluctuations on the superconducting layers lead to a coupling of the Josephson oscillations in different junctions. A simplified set of equations is then used to study the non-linear dynamics of the system. In particular the influence of the coupling on the current-voltage characteristics is investigated and upper limits for the coupling strength are estimated from a comparison with experiments on cuprate superconductors.",9810192v1 1998-10-30,The Markov approximation for the atomic output coupler,"The regions of validity of the Markov approximation for the coupling of atoms out of an atomic trap are determined. We consider radio-frequency output coupling in the presence of gravity and collisional repulsion, and Raman output coupling. The Markov approximation is crucial in most theoretical descriptions of an atom laser that assume a continuous process of output coupling from a trapped Bose-Einstein condensate. In this regime many techniques proved to be useful for modeling the optical laser, such as master equations, can be used to describe the dynamics of the damping of the condensate mode undergoing output coupling.",9810413v1 1998-11-02,Transport in Double-Crossed Luttinger Liquids,"We study transport through two Luttinger liquids (one-dimensional electrons interacting through a Coulomb repulsion in a metal) coupled together at {\it two} points. External voltage biases are incorporated through boundary conditions. We include density-density couplings as well as single-particle hops at the contacts. For weak repulsive interactions, transport through the wires remains undisturbed by the inter-wire couplings, which renormalise to zero. For strong repulsive interactions, the inter-wire couplings become strong. For symmetric barriers and no external voltage bias, a single gate voltage is sufficient to tune for resonance transmission in both wires. However, for asymmetric couplings or for finite external biases, the system is insulating.",9811011v1 1999-04-15,Frictional Drag Between Coupled 2D Hole Gases in GaAs/AlGaAs Heterostructures,"We report on the first measurements of the drag effect between coupled 2D-hole gases. We investigate the coupling by changing the carrier densities in the quantum wells, the widths of the barriers between the gases and the perpendicular magnetic field. From the data we are able to attribute the frictional drag to phonon coupling, because the non-parabolicity allows to tune the Fermi wavevector and the Fermi velocity separately and, thereby, to distinguish between phonon- and plasmon-dominated coupling.",9904214v1 1999-05-11,Dynamics of a Ring of Diffusively Coupled Lorenz Oscillators,"We study the dynamics of a finite chain of diffusively coupled Lorenz oscillators with periodic boundary conditions. Such rings possess infinitely many fixed states, some of which are observed to be stable. It is shown that there exists a stable fixed state in arbitrarily large rings for a fixed coupling strength. This suggests that coherent behavior in networks of diffusively coupled systems may appear at a coupling strength that is independent of the size of the network.",9905140v1 1999-09-18,Universal Scaling of Wave Propagation Failure in Arrays of Coupled Nonlinear Cells,"We study the onset of the propagation failure of wave fronts in systems of coupled cells. We introduce a new method to analyze the scaling of the critical external field at which fronts cease to propagate, as a function of intercellular coupling. We find the universal scaling of the field throughout the range of couplings, and show that the field becomes exponentially small for large couplings. Our method is generic and applicable to a wide class of cellular dynamics in chemical, biological, and engineering systems. We confirm our results by direct numerical simulations.",9909273v1 2000-02-16,The effect of Hund's Coupling on one-dimensional Luttinger Liquids,"Two one-dimensional Luttinger liquid systems coupled by Hund's coupling are studied by the renormalization group and the non-abelian bosonization methods. It is found that the Hund's coupling is always relevant irrespective of the repulsive interaction between electrons within each chain. The properties of the resulting strong coupling fixed point are discussed.",0002231v1 2000-02-18,Many-body CPA for the Holstein-DE model,"A many-body coherent potential approximation (CPA) previously developed for the double exchange (DE) model is extended to include coupling to local quantum phonons. The Holstein-DE model studied (equal to the Holstein model for zero Hund coupling) is considered to be a simple model for the colossal magnetoresistance manganites. We concentrate on effects due to the quantisation of the phonons, such as the formation of polaron subbands. The electronic spectrum and resistivity are investigated for a range of temperature and electron-phonon coupling strengths. Good agreement with experiment is found for the Curie temperature and resistivity with intermediate electron-phonon coupling strength, but phonon quantisation is found not to have a significant effect in this coupling regime.",0002297v1 2000-02-21,New way to achieve chaotic synchronization in spatially extended systems,"We study the spatio-temporal behavior of simple coupled map lattices with periodic boundary conditions. The local dynamics is governed by two maps, namely, the sine circle map and the logistic map respectively. It is found that even though the spatial behavior is irregular for the regularly coupled (nearest neighbor coupling) system, the spatially synchronized (chaotic synchronization) as well as periodic solution may be obtained by the introduction of three long range couplings at the cost of three nearest neighbor couplings.",0002315v1 2000-03-27,Intertube coupling in ropes of single-wall carbon nanotubes,"We investigate the coupling between individual tubes in a rope of single-wall carbon nanotubes using four probe resistance measurements. By introducing defects through the controlled sputtering of the rope we generate a strong non-monotonic temperature dependence of the four terminal resistance. This behavior reflects the interplay between localization in the intentionally damaged tubes and coupling to undamaged tubes in the same rope. Using a simple model we obtain the coherence length and the coupling resistance. The coupling mechanism is argued to involve direct tunneling between tubes.",0003423v1 2000-11-02,Coherent coupling of two quantum dots embedded in an Aharonov-Bohm ring,"We define two laterally gated small quantum dots (~ 15 electrons) in an Aharonov-Bohm geometry in which the coupling between the two dots can be broadly changed. For weakly coupled quantum dots we find Aharonov-Bohm oscillations. In an intermediate coupling regime we concentrate on the molecular states of the double dot and extract the magnetic field dependence of the coherent coupling.",0011044v1 2001-06-21,Quantum field effects in coupled atomic and molecular Bose-Einstein condensates,"This paper examines the parameter regimes in which coupled atomic and molecular Bose-Einstein condensates do not obey the Gross-Pitaevskii equation. Stochastic field equations for coupled atomic and molecular condensates are derived using the functional positive-P representation. These equations describe the full quantum state of the coupled condensates and include the commonly used Gross-Pitaevskii equation as the noiseless limit. The model includes all interactions between the particles, background gas losses, two-body losses and the numerical simulations are performed in three dimensions. It is found that it is possible to differentiate the quantum and semiclassical behaviour when the particle density is sufficiently low and the coupling is sufficiently strong.",0106427v1 2001-12-04,Coupled Growing Networks,"We introduce and solve a model which considers two coupled networks growing simultaneously. The dynamics of the networks is governed by the new arrival of network elements (nodes) making preferential attachments to pre-existing nodes in both networks. The model segregates the links in the networks as intra-links, cross-links and mix-links. The corresponding degree distributions of these links are found to be power-laws with exponents having coupled parameters for intra- and cross-links. In the weak coupling case the model reduces to a simple citation network. As for the strong coupling, it mimics the mechanism of \emph{the web of human sexual contacts}.",0112052v2 2002-08-20,Soliton Fermi sea in models of Ising-coupled Kondo impurities,"We study a model of Ising-coupled Kondo impurities that can be applied to quantum dots with capacitance coupling, coupled qubits with an incoherent environment, etc. We show that this model becomes equivalent to a Anderson impurity model with a novel solitonic Fermi sea. We derive exact results at the Toulouse point, and use the flow equation method to extend this analysis away from the Toulouse point for not too large Ising couplings.",0208390v2 2002-10-17,Frustration of the interlayer coupling by mobile holes in La2-xSrxCuO4 (x<0.02),"We have studied the interlayer coupling in the antiferromagnetic (AF) phase of Sr and Zn doped La2CuO4 by analyzing the spin flip transition in the magnetization curves. We find that the interlayer coupling strongly depends on the mobility of the hole charge carriers. Samples with the same hole content as well as the same Neel temperature but a different hole mobility, which we adjusted by Zn co-doping, can have a very different interlayer coupling. Our results suggest that only mobile holes can cause a strong frustration of the interlayer coupling.",0210357v1 2003-04-07,Variable electrostatic transformer: controllable coupling of two charge qubits,"We propose and investigate a novel method for the controlled coupling of two Josephson charge qubits by means of a variable electrostatic transformer. The value of the coupling capacitance is given by the discretized curvature of the lowest energy band of a Josephson junction, which can be positive, negative, or zero. We calculate the charging diagram of the two-qubit system that reflects the transition from positive to negative through vanishing coupling. We also discuss how to construct a phase gate making use of the controllable coupling.",0304166v2 2003-08-10,Spectroscopy on two coupled flux qubits,"We have performed spectroscopy measurements on two coupled flux qubits. The qubits are coupled inductively, which results in a $\sigma_1^z\sigma_2^z$ interaction. By applying microwave radiation, we observe resonances due to transitions from the ground state to the first two excited states. From the position of these resonances as a function of the magnetic field applied we observe the coupling of the qubits. The coupling strength agrees well with calculations of the mutual inductance.",0308192v1 2003-10-01,Rashba coupling in quantum dots: exact solution,"We present an analytic solution to the problem of the Rashba spin-orbit coupling in semiconductor quantum dots. We calculate the exact energy spectrum, wave-functions, and spin--flip relaxation times. We discuss various effects inaccessible via perturbation theory. In particular, we find that the effective gyromagnetic ratio is strongly suppressed by the spin-orbit coupling. The spin-flip relaxation rate has a maximum as a function of the spin-orbit coupling and is therefore suppressed in both the weak- and strong coupling limits.",0310024v2 2004-06-27,Spin transfer and coherence in coupled quantum wells,"Spin dynamics of optically excited electrons confined in asymmetric coupled quantum wells are investigated through time resolved Faraday rotation experiments. The inter-well coupling is shown to depend on applied electric field and barrier thickness. We observe three coupling regimes: independent spin precession in isolated quantum wells, incoherent spin transfer between single-well states, and coherent spin transfer in a highly coupled system. Relative values of the inter-well tunneling time, the electron spin lifetime, and the Larmor precession period appear to govern this behavior.",0406668v1 2005-01-11,Nonlinear Coupling in Nb/NbN Superconducting Microwave Resonators,"In this experimental study we show that the coupling between Nb/NbN superconducting microwave resonators and their feedline can be made amplitude dependent. We employ this mechanism to tune the resonators into critical coupling condition, a preferable mode of operation for a wide range of applications. Moreover we examine the dependence of critical coupling state on other parameters such as temperature and magnetic field. Possible novel applications based on such nonlinear coupling are briefly discussed.",0501236v1 2005-01-20,Computing Counterion Densities at Intermediate Coupling,"By decomposing the Coulomb interaction into a long distance component appropriate for mean-field theory, and a nonmean-field short distance component, we compute the counterion density near a charged surface for all values of the counterion coupling parameter. A modified strong-coupling expansion that is manifestly finite at all coupling strengths is used to treat the short distance component. We find a nonperturbative correction related to the lateral counterion correlations that modifies the density at intermediate coupling.",0501498v1 2005-02-14,"Interlayer Exchange Coupling in (Ga,Mn)As-based Superlattices","The interlayer coupling between (Ga,Mn)As ferromagnetic layers in all-semiconductor superlattices is studied theoretically within a tight-binding model, which takes into account the crystal, band and magnetic structure of the constituent superlattice components. It is shown that the mechanism originally introduced to describe the spin correlations in antiferromagnetic EuTe/PbTe superlattices, explains the experimental results observed in ferromagnetic semiconductor structures, i.e., both the antiferromagnetic coupling between ferromagnetic layers in IV-VI (EuS/PbS and EuS/YbSe) superlattices as well as the ferromagnetic interlayer coupling in III-V ((Ga,Mn)As/GaAs) multilayer structures. The model allows also to predict (Ga,Mn)As-based structures, in which an antiferromagnetic interlayer coupling could be expected.",0502321v1 2005-02-22,Dynamics of weakly coupled random antiferromagnetic quantum spin chains,"We study the low-energy collective excitations and dynamical response functions of weakly coupled random antiferromagnetic spin-1/2 chains. The interchain coupling leads to Neel order at low temperatures. We use the real-space renormalization group technique to tackle the intrachain couplings and treat the interchain couplings within the Random Phase Approximation (RPA). We show that the system supports collective spin wave excitations, and calculate the spin wave velocity and spectra weight within RPA. Comparisons will be made with inelastic neutron scattering experiments quasi-one-dimensional disordered spin systems such as doped CuGeO$_3$",0502530v2 2005-03-03,Finite-temperature properties of frustrated classical spins coupled to the lattice,"We present extensive Monte Carlo simulations for a classical antiferromagnetic Heisenberg model with both nearest ($J_1$) and next-nearest ($J_2$) exchange couplings on the square lattice coupled to the lattice degrees of freedom. The Ising-like phase transition, that appears for $J_2/J_1>1/2$ in the pure spin model, is strengthened by the spin-lattice coupling, and is accompanied by a lattice deformation from a tetragonal symmetry to an orthorhombic one. Evidences that the universality class of the transition does not change with the inclusion of the spin-lattice coupling are reported. Implications for ${\rm Li_2VOSiO_4}$, the prototype for a layered $J_1{-}J_2$ model in the collinear regime, are also discussed.",0503080v1 2005-04-11,Superconducting qubit network with controllable nearest neighbor coupling,"We investigate the design and functionality of a network of loop-shaped charge qubits with switchable nearest-neighbor coupling. The qubit coupling is achieved by placing large Josephson junctions at the intersections of the qubit loops and selectively applying bias currents. The network is scalable and makes it possible to perform a universal set of quantum gates. The coupling scheme allows gate operation at the charge degeneracy point of each qubit, and also applies to charge-phase qubits. Additional Josephson junctions included in the qubit loops for qubit readout can also be employed for qubit coupling.",0504250v1 2005-07-29,Charge fluctuation induced dephasing of exchange coupled spin qubits,"Exchange coupled {\it spin} qubits in semiconductor nanostructures are shown to be vulnerable to dephasing caused by {\it charge noise} invariably present in the semiconductor environment. This decoherence of exchange gate by environmental charge fluctuations arises from the fundamental Coulombic nature of the Heisenberg coupling, and presents a serious challenge to the scalability of the widely studied exchange gate solid state spin quantum computer architectures. We estimate dephasing times for coupled spin qubits in a wide range (from 1 ns up to $> 1 \mu$s) depending on the exchange coupling strength and its sensitivity to charge fluctuations.",0507725v2 2005-11-10,Do current-density nonlinearities cut off the glass transition?,"Extended mode coupling theories for dense fluids predict that nonlinear current-density couplings cut off the singular `ideal glass transition', present in the standard mode coupling theory where such couplings are ignored. We suggest here that, rather than allowing for activated processes as sometimes supposed, contributions from current-density couplings are always negligible close to a glass transition. We discuss in schematic terms how activated processes can nonetheless cut off the transition, by causing the memory function to become linear in correlators at late times.",0511260v1 2005-11-16,Mode-Coupling Theory (MCT) Lecture Notes,"In this set of lecture notes we review the mode-coupling theory of the glass transition from several perspectives. First, we derive mode-coupling equations for the description of density fluctuations from microscopic considerations with the use the Mori-Zwanzig projection operator technique. We also derive schematic mode-coupling equations of a similar form from a field-theoretic perspective. We review the successes and failures of mode-coupling theory, and discuss recent advances in the applications of the theory.",0511407v1 2006-02-03,Tunable coupling of qubits: nonadiabatic corrections,"We analyze the coupling of qubits mediated by a tunable and fast element beyond the adiabatic approximation. The nonadiabatic corrections are important and even dominant in parts of the relevant parameter range. As an example, we consider the tunable capacitive coupling between two charge qubits mediated by a gated Josephson junction, as suggested by Averin and Bruder. The nonadiabatic, inductive contribution persists when the capacitive coupling is tuned to zero. On the other hand, the total coupling can be turned off (in the rotating wave approximation) if the qubits are operated at symmetry points.",0602086v2 2006-04-19,Vibronic solitons in a (nearly-) degenerate electronic system along a 1-D chain,"We consider the formation and stability of the vibronic polaron arising in a degenerate or nearly degenerate electronic system coupled to an appropriate vibrational mode. We define the electron-phonon coupling as a mixing of the electronic states by the phonon mode. Our investigation is similar to that carried out recently by Dennis Clougherty though by introducing a different coupling operator. This extends the vibronic coupling range beyond the limits set by the difference in electronic density of the progenitor bands thereby widening the applicability range of the coupled soliton.",0604462v1 2006-05-28,Generalized switchable coupling for superconducting qubits using double resonance,"We propose a method for switchable coupling between superconducting qubits using double resonance. The inter-qubit coupling is achieved by applying near-resonant oscillating fields to the two qubits. The deviation from resonance relaxes the criterion of strong driving fields while still allowing for a fully entangling two-qubit gate. This method avoids some of the shortcomings of previous proposals for switchable coupling. We discuss the possible application of our proposal to a pair of inductively coupled flux qubits, and we consider the extension to phase qubits.",0605685v2 2006-06-22,Better synchronizability predicted by a new coupling method,"In this paper, inspired by the idea that the hub nodes of a highly heterogeneous network are not only the bottlenecks, but also effective controllers in the network synchronizing process, we bring forward an asymmetrical coupling method where the coupling strength of each node depends on its neighbors' degrees. Compared with the uniform coupled method and the recently proposed Motter-Zhou-Kurth method, the synchronizability of scale-free networks can be remarkably enhanced by using the present coupled method.",0606575v2 2006-12-29,Experimental Observation of Electronic Coupling in GaAs Lateral Quantum Dot Molecules,"We report the fabrication and photoluminescence properties of laterally-coupled GaAs/AlGaAs quantum dots. The coupling in the quantum dot molecules is tuned by an external electric field. An intricate behavior, consisting of spectral line crossings and avoided crossings is observed for different molecules. Anticrossing patterns in the photoluminescence spectra provide direct evidence of the lateral coupling between two nearby quantum dots. A simple calculation suggests that the coupling is mediated by electron tunneling, through which the states of direct and indirect exciton are brought into resonance.",0612701v3 2007-01-09,Artificial molecular quantum rings: Spin density functional theory calculations,"The ground states of artificial molecules made of two vertically coupled quantum rings are studied within the spin density functional theory for systems containing up to 13 electrons. Quantum tunneling effects on the electronic structure of the coupled rings are analyzed. For small ring radius, our results recover those of coupled quantum dots. For intermediate and large ring radius, new phases are found showing the formation of new diatomic artificial ring molecules. Our results also show that the tunneling induced phase transitions in the coupled rings occur at much smaller tunneling energy as compared to those for coupled quantum dot systems.",0701185v1 2006-11-24,Coupling Methodology within the Software Platform Alliances,"CEA, ANDRA and EDF are jointly developing the software platform ALLIANCES which aim is to produce a tool for the simulation of nuclear waste storage and disposal repository. This type of simulations deals with highly coupled thermo-hydro-mechanical and chemical (T-H-M-C) processes. A key objective of Alliances is to give the capability for coupling algorithms development between existing codes. The aim of this paper is to present coupling methodology use in the context of this software platform.",0611127v1 1998-07-23,Does the non-minimal coupling of the scalar field improve or destroy inflation ?,"The non-minimal coupling of a scalar field to the Ricci curvature in a curved spacetime is unavoidable according to several authors. The coupling constant is not a free parameter: the prescriptions for the value of the coupling constant in specific scalar field and gravity theories (in particular in general relativity) are studied. The results are applied to the most popular inflationary scenarios of cosmology and their theoretical consistence is analysed. Certain observational constraints on the coupling constant are also discussed.",9807066v1 2004-09-10,A Nonlinear Coupling Network to Simulate the Development of the r-mode Instablility in Neutron Stars I. Construction,"R-modes of a rotating neutron star are unstable because of the emission of gravitational radiation. We explore the saturation amplitudes of these modes determined by nonlinear mode-mode coupling. Modelling the star as incompressible allows the analytic computation of the coupling coefficients. All couplings up to n=30 are obtained, and analytic values for the shear damping and mode normalization are presented. In a subsequent paper we perform numerical simulations of a large set of coupled modes.",0409048v1 2006-10-24,Duffin-Kemmer-Petiau equation with nonminimal coupling to curvature,"The generalized Duffin-Kemmer-Petiau equation in curved space-time is proposed for non-minimal coupling to the curvature and external fields. The corresponding scalar and vector fields equation are found. Equations are presented, which are equivalent to those of a scalar field with conformal coupling and electromagnetic field with non-minimal coupling to the curvature. The gauge-invariant Duffin-Kemmer-Petiau equation with non-minimal coupling is given.",0610115v1 2001-02-22,Measurement of the leptoquark Yukawa couplings in e+e- collisions at TESLA,"Measurement of the Yukawa couplings of the first-generation leptoquarks has been studied for e+e- collisions at TESLA, at sqrt(s)=800 GeV. By combining measurements from different production and decay channels, determination of Yukawa couplings with precision on the few per-cent level is possible. TESLA will be sensitive to very small leptoquark Yukawa couplings not accessible at LHC, down to lambda ~ 0.05 [e]. Distinction between left-handed and right-handed Yukawa couplings is feasible even for leptoquark masses very close to the pair-production kinematic limit.",0102043v1 1995-03-30,Effective Yukawa Couplings in Noncompact Lattice QED,"We investigate effective Yukawa couplings of mesons to the elementary fermions in noncompact lattice QED. The couplings are extracted from suitable fermion-antifermion-meson three-point functions calculated by Monte Carlo simulations with dynamical staggered fermions. The scaling behaviour is compatible with expectations from perturbation theory, thus indicating triviality of QED. The lines of constant Yukawa coupling are compared to flows of other quantities. Consistency is seen, at most, for weak coupling.",9503026v1 2005-10-04,Pionic couplings (g^ and g~) in the static heavy quark limit,"The couplings between the soft pion and the doublet of heavy-light mesons are basic parameters of the ChPT approach to the heavy-light systems. We compute the unquenched (Nf=2) values of two such couplings in the static heavy quark limit: (1) g^, coupling to the lowest doublet of heavy-light mesons, and (2) g~, coupling to the first orbital excitations. A brief description of the calculation together with a short discussion of the results is presented.",0510017v1 1993-06-02,Coupling Constant and Yukawa Coupling Unifications: Uncertainties and Constraints,"The status of coupling constant unification (with and without a unification of Yukawa couplings) is discussed. Uncertainties associated with the input coupling constants, $m_{b}$ and $m_{t}$, threshold corrections at the low and high scale, and possible nonrenormalizable operators are described and a discrepancy between effective and physical scales is pointed out. Theoretical uncertainties in the predictions of $\alpha_{s}(M_{Z})$, $m_{b}$, and the unification scale, $M_{G}$, are discussed and estimated. Constraints on the super-partner spectrum are found to be weak if uncertainties associated with the high-scale are included. However, requiring $h_{b} = h_{\tau}$ at $M_{G}$ excludes $3 < \tan \beta < 40$ (for $m_{t} < 200$ GeV).",9306213v1 1994-05-02,About the relevance of the Imaginary components of the effective couplings in the Asymmetry measurements,"The effect coming from imaginary parts of effective couplings in the $e^+ e^-$ asymmetries is investigated. It is shown that for the present level of experimental accuracy, in some asymmetries the imaginary parts of the effective couplings cannot be neglected and moreover that the use of different prescriptions on how to handle them in quoting just real effective couplings from the data may produce sizable differences. A definition of the real effective couplings specifying how to handle the imaginary parts is advocated.",9405201v1 1995-03-06,Threshold Behaviour in Gauge Boson Pair Production at LEP 2,"We discuss the form of the amplitude for gauge boson pair production at or near threshold.We show that in the case of W-pair production at LEP2 near threshold only one anomalous electromagnetic coupling can contribute. This anomalous coupling is CP violating and contributes to the electric dipole moment of the $W$. Since this coupling is likely to be small, it is important to look for ZZgamma couplings in Zgamma production. These couplings are not suppressed at the W-threshold.",9503243v2 1995-06-22,Gauge Coupling Unification in GUT and String Models,"The results for the running of the gauge couplings in the MSSM are up-dated by proper inclusion of all low scale effects. They are presented as predictions for the strong coupling constant in the scenario with only two parameters at the GUT scale ~ ($\alpha_{U}$ ~and ~$M_{U}$) ~and as a mismatch of the couplings at the scales ~$\sim 3 \times 10^{16}$ GeV ~and ~$4\times10^{17}$ GeV, when all three couplings are taken as the experimental input.",9506393v1 1996-10-10,Effects of Anomalous Couplings of Quarks on Prompt Photon Production,"Prompt photon production is sensitive to the anomalous couplings of gluons to quarks, because it is mainly produced by quark-gluon scattering. We will examine the effects of the anomalous chromoelectric and chromomagnetic dipole moment couplings of quarks on prompt photon production. Using the data collected by CDF and D0 at the Fermilab Tevatron we put a bound on these anomalous couplings. We also estimate the sensitivity of various future high energy collider experiments to these anomalous couplings.",9610318v1 1996-10-29,Suppression of PiNN(1535) Coupling in the QCD Sum Rule,"The \pi NN^* and \eta NN^* coupling constants are studied based on the two point functions between the vacuum and a one meson state in the soft meson limit. In terms of a suitably constructed interpolating field for the nucleon and resonances, we have found that the \pi NN^* couplings vanish, while \eta NN^* couplings remain finite. This result explains a relatively suppressed coupling of \pi NN(1535) as compared with others. We compare the present result with predictions of low energy effective models.",9610520v2 1997-01-31,"Anomalous triple gauge couplings in e+ e- -> W+ W- and ""optimal"" strategies for their measurement","We show how one can measure anomalous WWZ- and WWgamma-couplings with minimal statistical error using integrated observables, without having to assume that the anomalous couplings are small. We propose a parametrisation of these couplings which is well suited for the extraction of both single and many parameters, and which leads to a very simple form of the integrated cross section, from which additional information on the couplings can be obtained.",9702208v1 1997-04-03,Reduction of Couplings and Finiteness in Realistic Supersymmetric GUTs,"Reduction of couplings in supersymmetric GUTs is achieved by searching for renormalization group invariant (RGI) relations among couplings which hold beyond the unification scale. Finiteness is due to the fact that there exist RGI relations among couplings that guarantee the vanishing of the beta-functions of a N=1 supersymmetric GUT even to all orders in perturbation theory. Of particular interest are the relations among gauge and Yukawa couplings which lead to very interesting predictions of the top quark mass",9704218v1 1997-04-12,Chaotic inflation with running nonminimal coupling,"We have found a successful model of chaotic inflation with an inflaton coupled nonminimally with gravity. The nonminimal coupling constant $\xi$ runs with the evolution of the inflaton. The running nature of the coupling leads naturally to the situations where the coupling becomes small enough to have sufficient period of the inflation to resolve the cosmological puzzles.",9704303v2 1997-06-18,Gauge-Boson Pair Production at the LHC: Anomalous Couplings and Vector-Boson Scattering,"We compare vector boson fusion and quark antiquark annihilation production of vector boson pairs at the LHC and include the effects of anomalous couplings. Results are given for confidence intervals for anomalous couplings at the LHC assuming that measurements will be in agreement with the standard model. We consider all couplings of the general triple vector boson vertex and their correlations. In addition we consider a gauge invariant dimension-six extension of the standard model. Analytical results for the cross sections for quark antiquark annihilation and vector boson fusion with anomalous couplings are given.",9706406v1 1997-06-24,Some Remarks on the Baryon-Meson Couplings in the 1/N_c Expansion,"The original results for the baryon-pion couplings in the large $N_c$ QCD can be understood in a simpler way in the Hartree-Fock picture. The large $N_c$ relation and its $1/N_c$ correction between the heavy baryon-meson coupling and the light baryon-meson coupling are emphasized. Application to the baryon-$\rho$ meson interactions is straightforward. The implications of recent experimental result for the strong coupling constants of the heavy baryon chiral lagrangian are discussed.",9706481v1 1997-07-10,Suppression of PiNN* Coupling and Chiral Symmetry,"Meson-baryon couplings between positive and negative parity baryons are investigated using two point correlation functions in the soft meson limit. We find that the pi NN^* coupling vanishes due to chiral symmetry, while the eta NN^* coupling remains finite. We perform an analysis based on the algebraic method for SU(2) and SU(3) chiral symmetry, and find that baryon axial charges play an essential role for vanishing coupling constants.",9707307v1 1998-05-19,The Anomalous Magnetic Moment of the Muon and Higgs-Mediated Flavor Changing Neutral Currents,"In the two-Higgs doublet extension of the standard model, flavor-changing neutral couplings arise naturally. In the lepton sector, the largest such coupling is expected to be $\mu-\tau-\phi#. We consider the effects of this coupling on the anomalous magnetic moment of the muon. The resulting bound on the coupling, unlike previous bounds, is independent of the value of other unknown couplings. It will be significantly improved by the upcoming E821 experiment at Brookhaven National Lab.",9805376v1 2000-08-03,Correspondence of consistent and inconsistent spin-3/2 couplings via the equivalence theorem,"The Rarita-Schwinger theory of free massive spin-3/2 field obeys the physical degrees of freedom counting, and one can distinguish ``consistent'' couplings which maintain this property and ``inconsistent'' couplings which destroy it. We show how one can obtain consistent couplings from inconsistent ones by a redefinition of the spin-3/2 field. The field redefinition gives rise to additional ``contact terms'' which, via the equivalence theorem, can be associated with the contribution of the extra lower-spin degrees of freedom involved by the inconsistent coupling.",0008026v2 2002-11-08,Varying Couplings From Orbifold GUTs,"We discuss the variation of gauge couplings in time in the framework of orbifold constructions, due to a change of the extra compact dimension's size. Models with gauge coupling unification allow to estimate the variation of the strong coupling constant $\al_3$ and to relate it to a variation of $\alpha_{em}$. The extra-dimensional construction turns out to be crucial for the model to be compatible with data. Within the presented 5D scenarios, the tower of KK states significantly affects gauge coupling running, leads to low scale unification, and provides a suppression of the $\al_3(M_Z)$ variation.",0211122v2 2003-11-05,$H^+ W^- Z$ contribution to the static quantities of the W boson in the context of Higgs-triplet theories,"We calculate the one--loop contribution from the $H^+ W^- Z$ coupling to the static electromagnetic properties of the W boson. Although this coupling is absent at the tree--level in all Higgs--doublet models, it can be induced at this order in models including Higgs--triplet representations. It is found that the $H^+ W^- Z$ contribution can be as important as those arising from other couplings including Higgs bosons, such as the standard model coupling WWH or the two--Higgs--doublet model couplings $H^+ W^- \phi^0$ and $W W \phi^0$, with $\phi^0=h$, $H$ and $A$.",0311066v1 2004-08-24,Charges and Coupling Strengths in Gauge Theories with Direct Product Symmetry Groups,"For gauge theories with direct product internal symmetry groups, the relationship between internal quantum numbers (charges) and coupling strengths is examined. In these types of theories, the Lagrangian density may contain non-trivial factors multiplying the matter field terms, and these factors can modify the interaction coupling strengths i.e., the gauge/matter field vertex factors. Consequently, a matter field can carry a given internal charge yet couple to the associated gauge field with an apparent fractional charge. An example with $SU(3)\otimes U(2)$ symmetry is presented in which the matter fields can have integer U(2) charges but fractional U(2) coupling strengths.",0408266v2 2004-09-28,The Temperature Dependence of the QCD Running Coupling,"We study the running of the QCD coupling with the momentum squared ($Q^2$) and the temperature scales in the high temperature limit ($T > T_{c}$), using a mass dependent renormalization scheme to build the Renormalization Group Equations. The approach used guaranty gauge invariance, through the use of the Hard Thermal Loop approximation, and independence of the vertex chosen to renormalize the coupling. In general, the dependence of the coupling with the temperature is not logarithmical, although in the region $Q^2 \sim T^2$ the logarithm approximation is reasonable. Finally, as known from Debye screening, color charge is screened in the coupling. The number of flavors, however, is anti-screened.",0409329v1 2006-04-28,New Physics effects in the flavor-changing neutral couplings of the Top quark,"We survey the flavor-changing neutral couplings (FCNC) of the top quark predicted by some extensions of the Standard Model: THDM, SUSY, L-R symmetric, TC2, 331, and models with extra quarks. Since the expected sensitivity of the LHC and ILC for the tcV (V=\gamma,g,Z) and tcH couplings is of order of a few percent, we emphasize the importance of any new physics effect that gives a prediction for these FCNC couplings within this limit. We also review the constraints imposed on these couplings from low-energy precision measurements.",0605003v1 2006-10-23,Light scalars coupled to photons and non-newtonian forces,"A particle $\phi$ coupling to two photons couples also to charged particles, like protons, through a loop. If the particle is a light scalar this induced coupling to protons leads to non-newtonian forces. We show that the experimental constraints on exotic, fifth-type forces lead to stringent constraints on the $\phi\gamma\gamma$ coupling.",0610286v2 1993-04-27,The Strength of String Nonperturbative Effects and Strong-Weak Coupling Duality,"A strong-weak coupling duality symmetry of the string equations of motion has been suggested in the literature. This symmetry implies that vacua occur in pairs. Since the coupling constant is a dynamical variable in string theory, tunneling solutions between strong and weak coupling vacua may exist. Such solutions would naturally lead to nonperturbative effects with anomalous coupling dependence. A highly simplified example is given.",9304129v2 1995-03-31,"Nontrivial, Asymptotically Non-free Gauge Theories and Dynamical Unification of Couplings","An evidence for nontriviality of asymptotically non-free (ANF) Yang-Mills theories is found on the basis of optimized perturbation theory. It is argued that these theories with matter couplings can be made nontrivial by means of the reduction of couplings, leading to the idea of dynamical unification of couplings (DUC) The second-order reduction of couplings in the ANF $SU(3)$-gauged Higgs-Yukawa theory, which is assumed to be nontrivial here, is carried out to motivate independent investigations on its nontriviality and DUC.",9503221v1 1997-01-13,Strong Coupling Expansions of SU(N) Seiberg-Witten Theory,"We set up a systematic expansion of the prepotential for ${\cal N}=2$ supersymmetric Yang-Mills theories with SU(N) gauge group in the region of strong coupling where a maximal number of mutually local fields become massless. In particular, we derive the first non-trivial non-perturbative correction, which is the first term in the strong coupling expansion providing a coupling between the different U(1) factors, and which governs for example the strength of gaugino Yukawa couplings.",9701055v1 1997-06-04,Exponentially Small Couplings between Twisted Fields of Orbifold String Theories,"We investigate the natural occurence of exponentially small couplings in effective field theories deduced from higher dimensional models. We calculate the coupling between twisted fields of the Z_3 Abelian orbifold compactification of the heterotic string. Due to the propagation of massive Kaluza-Klein modes between the fixed points of the orbifold, the massless twisted fields located at these singular points become weakly coupled. The resulting small couplings have an exponential dependence on the mass of the intermediate states and the distance between the fixed points.",9706028v1 1998-12-08,Anomalous couplings for D-branes and O-planes,"We study anomalous Wess-Zumino couplings of D-branes and O-planes in a general background and derive them from a direct string computation by factorizing in the RR channel various one-loop amplitudes. In particular, we find that Op-planes present gravitational anomalous couplings involving the Hirzebruch polynomial L, similarly to the roof genus A encoding Dp-brane anomalous couplings. We determine, in each case, the precise dependence of these couplings on the curvature of the tangent and normal bundles.",9812071v1 2004-09-02,Lagrange Multipliers and Couplings in Supersymmetric Field Theory,"In hep-th/0312098 it was argued that by extending the ``$a$-maximization'' of hep-th/0304128 away from fixed points of the renormalization group, one can compute the anomalous dimensions of chiral superfields along the flow, and obtain a better understanding of the irreversibility of RG flow in four dimensional supersymmetric field theory. According to this proposal, the role of the running couplings is played by certain Lagrange multipliers that are introduced in the construction. We show that one can choose a parametrization of the space of couplings in which the Lagrange multipliers can indeed be identified with the couplings, and discuss the consequences of this for weakly coupled gauge theory.",0409029v1 2005-04-04,Scalar tensor theory of gravity carrying a conserved current,"A general scalar-tensor theory of gravity carries a conserved current for a trace free minimally coupled scalar field, under the condition that the potential $V(\phi)$ of the nonminimally coupled scalar field is proportional to the square of the parameter $f(\phi)$ that is coupled with the scalar curvature $R$. The conserved current relates the pair of arbitrary coupling parameters $f(\phi)$ and $\omega(\phi)$, where the latter is the Brans-Dicke coupling parameter. Thus fixing up the two arbitrary parameters by hand, it is possible to explore the symmetries and the form of conserved currents corresponding to standard and many different nonstandard models of gravity.",0504021v1 2007-01-12,"Anomalous U(1)'s, Chern-Simons couplings and the Standard Model","This proceeding is based on hep-th/0605225 and it shows that the most general anomaly related effective action contains Stuckelberg, axionic and Chern-Simons-like couplings. Such couplings are generically non-trivial in orientifold string vacua. A similar analysis in quantum field theories provides similar couplings. These Chern-Simons couplings generate new signals which might be visible at LHC.",0701114v2 2002-03-08,Compactification of the moduli spaces of vortices and coupled vortices,"Vortices and coupled vortices arise from Yang-Mills-Higgs theories and can be viewed as generalizations or analogues to Yang-Mills connections and, in particular, Hermitian-Yang-Mills connections. We proved an analytic compactification of the moduli spaces of vortices and coupled vortices on hermitian vector bundles over compact K\""ahler manifolds. In doing so we introduced the concept of ideal coupled vortices and characterized the singularities of ideal coupled vortices as well as Hermitian-Yang-Mills connections.",0203078v1 2004-02-23,Coupling Poisson and Jacobi structures on foliated manifolds,"Let M be a differentiable manifold endowed with a foliation F. A Poisson structure P on M is F-coupling if the image of the annihilator of TF by the sharp-morphism defined by P is a normal bundle of the foliation F. This notion extends Sternberg's coupling symplectic form of a particle in a Yang-Mills field. In the present paper we extend Vorobiev's theory of coupling Poisson structures from fiber bundles to foliations and give simpler proofs of Vorobiev's existence and equivalence theorems of coupling Poisson structures on duals of kernels of transitive Lie algebroids over symplectic manifolds. Then we discuss the extension of the coupling condition to Jacobi structures on foliated manifolds.",0402361v1 2001-01-16,An Exactly Solvable Model for the Interaction of Linear Waves with Korteweg-de Vries Solitons,"Under certain mode-matching conditions, small-amplitude waves can be trapped by coupling to solitons of nonlinear fields. We present a model for this phenomenon, consisting of a linear equation coupled to the Korteweg-de Vries equation. The model has one parameter, a coupling constant. For one value of the coupling constant the model becomes the linearized KdV equation. We solve the problem exactly for a different value of the coupling parameter, for which the solutions behave differently. We describe an application of our results to the dynamics of molecules.",0101027v1 2002-01-17,Lag time and parameter mismatches in synchronization of unidirectionally coupled chaotic external cavity semiconductor lasers,"We report an analysis of synchronization between two unidirectionally coupled chaotic external cavity master/slave semiconductor lasers with two characteristic delay times, where the delay time in the coupling is different from the delay time in the coupled systems themselves. We demonstrate for the first time that parameter mismatches in photon decay rates for the master and slave lasers can explain the experimental observation that the lag time is equal to the coupling delay time.",0201032v1 2002-08-07,Hierarchy of Chaotic maps with an invariant measure and their coupling,"Hierarchy of one-parameter families of chaotic maps with an invariant measure have been introduced, where their appropriate coupling has lead to the generation of some coupled chaotic maps with an invariant measure. It is shown that these chaotic maps (also the coupled maps) do not undergo any period doubling or period-n-tupling cascade bifurcation to chaos, but they have either single fixed point attractor at certain values of the parameters or they are ergodic in the complementary region. Using the invariant measure or Sinai-Rulle-Bowen measure the Kolmogrov-Sinai entropy of the chaotic maps (coupled maps) have been calculated analytically, where the numerical simulations support the results",0208011v1 2005-07-15,Synchronization of coupled chaotic oscillators as a phase transition,"We characterize the synchronization of an array of coupled chaotic elements as a phase transition where order parameters related to the joint probability at two sites obey power laws versus the mutual coupling strength; the phase transition corresponds to a change in the exponent of the power law. Since these studies are motivated by the behaviour of the cortical neurons in cognitive tasks, we account for the short time available to any brain decision by studying how the mutual coupling affects the transient behaviour of a synchronization transition over a fixed time interval. We present a novel feature, namely, the absence of decay of the initial defect density for small coupling.",0507030v1 2006-01-31,The Time of Synchronization of Oscillationsin Two Coupled Identical Subsystems,"The mechanism of synchronization of oscillations in two identical coupled flow systems has beenstudied. The time (past the coupling onset) during which a synchronous oscillation regime is establisheddepends on the oscillation phase difference between the subsystems. Variation of the coupling parameter leadsto a change in the character of dependence of the synchronization time on the phase difference. Several typesof synchronization processes are revealed, which are realized for various values of the coupling parameter.",0601072v1 2006-03-27,Semi-direct sums of Lie algebras and discrete integrable couplings,"A relation between semi-direct sums of Lie algebras and integrable couplings of lattice equations is established, and a practicable way to construct integrable couplings is further proposed. An application of the resulting general theory to the generalized Toda spectral problem yields two classes of integrable couplings for the generalized Toda hierarchy of lattice equations. The construction of integrable couplings using semi-direct sums of Lie algebras provides a good source of information on complete classification of integrable lattice equations.",0603064v1 2006-07-31,Bifurcation and Chaos in Coupled Periodically Forced Non-identical Duffing Oscillators,"We study the bifurcations and the chaotic behaviour of a periodically forced double-well Duffing oscillator coupled to a single-well Duffing oscillator. Using the amplitude and the frequency of the driving force as control parameters, we show that our model presents phenomena which were not observed in coupled periodically forced Duffing oscillators with identical potentials. In the regime of relatively weak coupling, bubbles of bifurcations and chains of symmetry-breaking are identified. For much stronger couplings, Hopf bifurcations born from orbits of higher periodicity and supercritical Neimark bifurcations emerge. Moreover, tori-breakdown route to a strange non-chaotic attractor is also another highlight of features found in this model.",0607074v1 2006-10-10,Isochronal synchrony and bidirectional communication with delay-coupled nonlinear oscillators,"We propose a basic mechanism for isochronal synchrony and communication with mutually delay-coupled chaotic systems. We show that two Ikeda ring oscillators (IROs), mutually coupled with a propagation delay, synchronize isochronally when both are symmetrically driven by a third Ikeda oscillator. This synchronous operation, unstable in the two delay-coupled oscillators alone, facilitates simultaneous, bidirectional communication of messages with chaotic carrier waveforms. This approach to combine both bidirectional and unidirectional coupling represents an application of generalized synchronization using a mediating drive signal for a spatially distributed and internally synchronized multi-component system.",0610024v1 1993-09-22,Symmetry properties of SU3 vector coupling coefficients,"A presentation of the problem of calculating the vector coupling coefficients for $SU3 \supset SU2 \otimes U1$ is made, in the spirit of traditional treatments of SU2 coupling. The coefficients are defined as the overlap matrix element between product states and a coupled state with good SU3 quantum numbers. A technique for resolution of the outer degeneracy problem, based upon actions of the infinitesimal generators of SU3 is developed, which automatically produces vector coupling coefficients with symmetries under exchange of state labels which parallel the familiar symmetries of the SU2 case. An algorithm for efficient computation of these coefficients is outlined, for which an ANSI C code is available.",9309023v1 1999-03-30,A program for coupled-channels calculations with all order couplings for heavy-ion fusion reactions,"A FORTRAN77 program is presented that calculates fusion cross sections and mean angular momenta of the compound nucleus under the influence of couplings between the relative motion and several nuclear collective motions. The no-Coriolis approximation is employed to reduce the dimension of coupled-channels equations. The program takes into account the effects of non-linear couplings to all orders, which have been shown to play an important role in heavy-ion fusion reactions at subbarrier energies.",9903074v1 2004-09-06,Gauge symmetric delta(1232) couplings and the radiative muon capture in hydrogen,"Using the difference between the gauge symmetric and standard pi-N-delta couplings, a contact pi-pi-N-N term, quadratic in the pi-N-delta coupling, is explicitly constructed. Besides, a contribution from the delta excitation mechanism to the photon spectrum for the radiative muon capture in hydrogen is derived from the gauge symmetric pi-N-delta and gamma-N-delta couplings. It is shown for the photon spectrum, studied recently experimentally, that the new spectrum is for the photon momentums k > 60 MeV by 4-10 % smaller than the one obtained from standardly used couplings with the on-shell deltas.",0409011v1 2004-06-18,Accurate calculations of magnetic dipole and electric quadrupole hyperfine coupling constants of 6 P_{3/2} state of Cesium atom : A Relativistic Coupled Cluster approach,"We report the magnetic dipole and electric quadrupole hyperfine coupling constants of 6 P_{3/2} state of ^{133} Cs(I= {7/2}) obtained from the relativistic coupled cluster (RCC) method. To our knowledge, no prior electric quadrupole hyperfine CC calculation is available for ^{133} Cs(6 P_{3/2}) state. Our computed magnetic dipole (A) and electric quadrupole (B) coupling constants are in excellent agreement with the experiment.",0406083v1 2004-11-26,On linear coupling of acoustic and cyclotron waves in plasma flows,"It is found that in magnetized electrostatic plasma flows the velocity shear couples ion-acoustic waves with ion-cyclotron waves and leads, under favorable conditions, to their efficient reciprocal transformations. It is shown that in a two-dimensional setup this coupling has a remarkable feature: it is governed by equations that are exactly similar to the ones describing coupling of sound waves with internal gravity waves [Rogava & Mahajan: Phys. Rev. E vol.55, 1185 (1997)] in neutral fluid flows. Using another noteworthy quantum mechanical analogy we calculate transformation coefficients and give fully analytic, quantitative description of the coupling efficiency for flows with low shearing rates.",0411235v1 2005-06-10,Coupled-mode theory for periodic side-coupled microcavity and photonic crystal structures,"We use a phenomenological Hamiltonian approach to derive a set of coupled mode equations that describe light propagation in waveguides that are periodically side-coupled to microcavities. The structure exhibits both Bragg gap and (polariton like) resonator gap in the dispersion relation. The origin and physical significance of the two types of gaps are discussed. The coupled-mode equations derived from the effective field formalism are valid deep within the Bragg gaps and resonator gaps.",0506102v1 2006-05-19,Coupled applications on distributed resources,"Coupled models are set to become increasingly important in all aspects of science and engineering as tools with which to study complex systems in an integrated manner. Such coupled, hybrid simulations typically communicate data between the component models of which they are comprised relatively infrequently, and so a Grid is expected to present an ideal architecture on which to run them. In the present paper, we describe a simple, flexible and extensible architecture for a two-component hybrid molecular-continuum coupled model (hybrid MD). We discuss its deployment on distributed resources and the extensions to the RealityGrid computational-steering system to handle coupled models.",0605171v1 1998-01-23,Transverse-mode coupling in a Kerr medium,"We analyze nonlinear transverse mode coupling in a Kerr medium placed in an optical cavity and its influence on bistability and different kinds of quantum noise reduction. Even for an input beam that is perfectly matched to a cavity mode, the nonlinear coupling produces an excess noise in the fluctuations of the output beam. Intensity squeezing seems to be particularly robust with respect to mode coupling, while quadrature squeezing is more sensitive. However, it is possible to find a mode the quadrature squeezing of which is not affected by the coupling.",9801053v1 2004-03-31,Effect of intersubsystem coupling on the geometric phase in a bipartite system,"The influence of intersubsystem coupling on the cyclic adiabatic geometric phase in bipartite systems is investigated. We examine the geometric phase effects for two uniaxially coupled spin$-{1/2}$ particles, both driven by a slowly rotating magnetic field. It is demonstrated that the relation between the geometric phase and the solid angle enclosed by the magnetic field is broken by the spin-spin coupling, in particular leading to a quenching effect on the geometric phase in the strong coupling limit.",0403231v2 2004-07-07,Quantum state transfer in imperfect artificial spin networks,"High-fidelity quantum computation and quantum state transfer are possible in short spin chains. We exploit a system based on a dispersive qubit-boson interaction to mimic XY coupling. In this model, the usually assumed nearest-neighbors coupling is no more valid: all the qubits are mutually coupled. We analyze the performances of our model for quantum state transfer showing how pre-engineered coupling rates allow for nearly optimal state transfer. We address a setup of superconducting qubits coupled to a microstrip cavity in which our analysis may be applied.",0407058v2 2005-03-08,The Partition Function for the Anharmonic Oscillator in the Strong-Coupling Regime,"We consider a single anharmonic oscillator with frequency $\omega$ and coupling constant $\lambda$ respectively, in the strong-coupling regime. We are assuming that the system is in thermal equilibrium with a reservoir at temperature $\beta^{-1}$. Using the strong-coupling perturbative expansion, we obtain the partition function for the oscillator in the regime $\lambda>>\omega$, up to the order $\frac{1}{\sqrt{\lambda}}$. To obtain this result, we use of a combination of Klauder's independent-value generating functional (Acta Phys. Austr. {\bf 41}, 237 (1975)), and the generalized zeta-function method. The free energy and the mean energy, up to the order $\frac{1}{\sqrt{\lambda}}$, are also presented. We are showing that the thermodynamics quantities are nonanalytic in the coupling constant.",0503080v1 2005-10-20,Overdamping by weakly coupled environments,"A quantum system weakly interacting with a fast environment usually undergoes a relaxation with complex frequencies whose imaginary parts are damping rates quadratic in the coupling to the environment, in accord with Fermi's ``Golden Rule''. We show for various models (spin damped by harmonic-oscillator or random-matrix baths, quantum diffusion, quantum Brownian motion) that upon increasing the coupling up to a critical value still small enough to allow for weak-coupling Markovian master equations, a new relaxation regime can occur. In that regime, complex frequencies lose their real parts such that the process becomes overdamped. Our results call into question the standard belief that overdamping is exclusively a strong coupling feature.",0510164v1 2006-05-01,Nonlinear coupling of nano mechanical resonators to Josephson quantum circuits,"We propose a technique to couple the position operator of a nano mechanical resonator to a SQUID device by modulating its magnetic flux bias. By tuning the magnetic field properly, either linear or quadratic couplings can be realized, with a discretely adjustable coupling strength. This provides a way to realize coherent nonlinear effects in a nano mechanical resonator by coupling it to a Josephson quantum circuit. As an example, we show how squeezing of the nano mechanical resonator state can be realized with this technique. We also propose a simple method to measure the uncertainty in the position of the nano mechanical resonator without quantum state tomography.",0605017v1 2007-03-22,Controlled-NOT gate design for Josephson phase qubits with tunable inductive coupling: Weyl chamber steering and area theorem,"Superconducting qubits with tunable coupling are ideally suited for fast and accurate implementation of quantum logic. Here we present a simple approach, based on Weyl chamber steering, to CNOT gate design for inductively coupled phase qubits with tunable coupling strength g. In the presence of simultaneous rf pulses on the individual qubits that appropriately track the coupling strength as it is varied, we show that an infinite family of switching sequences preserving the time integral or ""area"" of g can be used to generate CNOT logic. We demonstrate our approach by considering time-dependencies most likely to be used in actual implementations: trapezoidal, sine, and soft quartic (also known as Landau's hat).",0703208v1 1999-02-12,A critical Ising model on the Labyrinth,"A zero-field Ising model with ferromagnetic coupling constants on the so-called Labyrinth tiling is investigated. Alternatively, this can be regarded as an Ising model on a square lattice with a quasi-periodic distribution of up to eight different coupling constants. The duality transformation on this tiling is considered and the self-dual couplings are determined. Furthermore, we analyze the subclass of exactly solvable models in detail parametrizing the coupling constants in terms of four rapidity parameters. For those, the self-dual couplings correspond to the critical points which, as expected, belong to the Onsager universality class.",9902009v1 2007-05-27,Electromagnetic field quantization in an anisotropic and inhomogeneous magnetodielectric,"The electromagnetic field in an anisotropic and inhomogeneous magnetodielectric is quantized by modelling the medium with two independent quantum fields. Some coupling tensors coupling the electromagnetic field with the medium are introduced. Electric and magnetic polarizations are obtained in terms of the ladder operators of the medium and the coupling tensors explicitly. Using a minimal coupling scheme for electric and magnetic interactions, the Maxwell equations and the constitutive equations of the medium are obtained. The electric and magnetic susceptibility tensors of the medium are calculated in terms of the coupling tensors. Finally the efficiency of the approach is elucidated by some examples.",0705.3942v1 2007-06-09,Coupling of Optical Lumped Nanocircuit Elements and Effects of Substrates,"We present here a model for the coupling among small nanoparticles excited by an optical electric field in the framework of our optical lumped nanocircuit theory [N. Engheta, A. Salandrino, and A. Alu Phys. Rev. Lett. 95, 095504 (2005)]. We derive how this coupling affects the corresponding nanocircuit model by adding controlled sources that depend on the optical voltages applied on the coupled particles. With the same technique, we can model also the presence of a substrate underneath nanocircuit elements, relating its presence to the coupling with a properly modeled image nanoparticle. These results are of importance in the understanding and the design of complex optical nanocircuits at infrared and optical frequencies.",0706.1316v1 2007-06-15,Electron-acoustic-phonon scattering and electron relaxation in two-coupled quantum rings,"Electron relaxation, induced by acoustic phonons, is studied for coupled quantum rings in the presence of external fields, both electric and magnetic. We address the problem of a single electron in vertically coupled GaAs quantum rings. Electron-phonon interaction is accounted for both deformation potential and piezoelectric field coupling mechanisms. Depending on the external fields, the ring radii and the separation between the rings, we show that the two different couplings have different weights and importance. Significant oscillations are found in the scattering rates from electron excited states to the ground state, as a function of either the geometry of the system or the external fields.",0706.2352v1 2007-07-27,Zero delay synchronization of chaos in coupled map lattices,"We show that two coupled map lattices that are mutually coupled to one another with a delay can display zero delay synchronization if they are driven by a third coupled map lattice. We analytically estimate the parametric regimes that lead to synchronization and show that the presence of mutual delays enhances synchronization to some extent. The zero delay or isochronal synchronization is reasonably robust against mismatches in the internal parameters of the coupled map lattices and we analytically estimate the synchronization error bounds.",0707.4051v1 2007-08-31,Continuation of solutions of coupled dynamical systems,"Recently, the synchronization of coupled dynamical systems has been widely studied. Synchronization is referred to as a process wherein two (or many) dynamical systems are adjusted to a common behavior as time goes to infinity, due to coupling or forcing. Therefore, before discussing synchronization, a basic problem on continuation of the solution must be solved: For given initial conditions, can the solution of coupled dynamical systems be extended to the infinite interval $[0,+\infty)$? In this paper, we propose a general model of coupled dynamical systems, which includes previously studied systems as special cases, and prove that under the assumption of QUAD, the solution of the general model exists on $[0,+\infty)$.",0708.4275v1 2007-09-22,Interactions of Hermitian and non-Hermitian Hamiltonians,"The coupling of non-Hermitian PT-symmetric Hamiltonians to standard Hermitian Hamiltonians, each of which individually has a real energy spectrum, is explored by means of a number of soluble models. It is found that in all cases the energy remains real for small values of the coupling constant, but becomes complex if the coupling becomes stronger than some critical value. For a quadratic non-Hermitian PT-symmetric Hamiltonian coupled to an arbitrary real Hermitian PT-symmetric Hamiltonian, the reality of the ground-state energy for small enough coupling constant is established up to second order in perturbation theory.",0709.3605v1 2007-09-24,Environmental Dependence of Masses and Coupling Constants,"We construct a class of scalar field models coupled to matter that lead to the dependence of masses and coupling constants on the ambient matter density. Such models predict a deviation of couplings measured on the Earth from values determined in low-density astrophysical environments, but do not necessarily require the evolution of coupling constants with the redshift in the recent cosmological past. Additional laboratory and astrophysical tests of \Delta \alpha and \Delta(m_p/m_e) as functions of the ambient matter density are warranted.",0709.3825v3 2007-10-11,Optical coupling of fundamental whispering gallery modes in bi-spheres,"What will happen if two identical microspheres, with fundamental whispering gallery modes excited in each of them, become optically coupled? Conventional wisdom based on coupled-mode arguments says that two new modes, bonding and anti-bonding, with two split frequencies would be formed. In this paper we demonstrate, using exact multi-sphere Mie theory, that in reality an attempt to couple two fundamental modes of microspheres would result in a complex multi-resonance optical response with the field distribution significantly deviating from predictions of coupled-mode type theories.",0710.2276v1 2007-11-19,Critical Lattice Size Limit for Synchronized Chaotic State in 1-D and 2-D Diffusively Coupled Map Lattices,"We consider diffusively coupled map lattices with $P$ neighbors (where $P$ is arbitrary) and study the stability of synchronized state. We show that there exists a critical lattice size beyond which the synchronized state is unstable. This generalizes earlier results for nearest neighbor coupling. We confirm the analytical results by performing numerical simulations on coupled map lattices with logistic map at each node. The above analysis is also extended to 2-dimensional $P$-neighbor diffusively coupled map lattices.",0711.2851v1 2008-02-19,Coupled oscillators as models of quintom dark energy,"We investigate quintom cosmology in FRW universes using isomorphic models consisting of three coupled oscillators, one of which carries negative kinetic energy. In particular, we examine the cosmological paradigms of minimally-coupled massless quintom, of two conformally-coupled massive scalars and of conformally-coupled massive quintom, and we obtain their qualitative characteristics as well as their quantitative asymptotic behavior. For open or flat geometries, we find that, independently of the specific initial conditions, the universe is always led to an eternal expansion.",0802.2595v2 2008-03-14,Kondo effect in quantum dots coupled to ferromagnetic leads with noncollinear magnetizations: effects due to electron-phonon coupling,"Spin-polarized transport through a quantum dot strongly coupled to ferromagnetic electrodes with non-collinear magnetic moments is analyzed theoretically in terms of the non-equilibrium Green function formalism. Electrons in the dot are assumed to be coupled to a phonon bath. The influence of electron-phonon coupling on tunnelling current, linear and nonlinear conductance, and on tunnel magnetoresistance is studied in detail. Variation of the main Kondo peaks and phonon satellites with the angle between magnetic moments of the leads is analyzed.",0803.2152v1 2008-06-03,Hyperbolicity of the Trace Map for the Weakly Coupled Fibonacci Hamiltonian,"We consider the trace map associated with the Fibonacci Hamiltonian as a diffeomorphism on the invariant surface associated with a given coupling constant and prove that the non-wandering set of this map is hyperbolic if the coupling is sufficiently small. As a consequence, for these values of the coupling constant, the local and global Hausdorff dimension and the local and global box counting dimension of the spectrum of the Fibonacci Hamiltonian all coincide and are smooth functions of the coupling constant.",0806.0645v1 2008-06-10,Higher Order Periodic Solutions of Coupled phi4 Models,"We obtain several higher order exact periodic solutions of (i) a coupled symmetric phi4 model in an external field, (ii) an asymmetric coupled phi4 model, (iii) an asymmetric-symmetric coupled phi4 model, in terms of Lame polynomials of order two and obtain the corresponding hyperbolic solutions in the appropriate limit. These solutions are unusual in the sense that while they are the solutions of the coupled problems, they are not the solutions of the corresponding uncoupled problems.",0806.1564v1 2008-09-05,Time-delayed feedback in neurosystems,"The influence of time delay in systems of two coupled excitable neurons is studied in the framework of the FitzHugh-Nagumo model. Time-delay can occur in the coupling between neurons or in a self-feedback loop. The stochastic synchronization of instantaneously coupled neurons under the influence of white noise can be deliberately controlled by local time-delayed feedback. By appropriate choice of the delay time synchronization can be either enhanced or suppressed. In delay-coupled neurons, antiphase oscillations can be induced for sufficiently large delay and coupling strength. The additional application of time-delayed self-feedback leads to complex scenarios of synchronized in-phase or antiphase oscillations, bursting patterns, or amplitude death.",0809.1025v1 2008-10-17,Non-minimal coupling in inflation and inflating with the Higgs boson,"We analyse the effect of the non-minimal coupling of the form $\xi\phi^2R/2$ on the single field inflation. If the non-minimal coupling is large, it relaxes the constraint on the field self coupling, making it possible to use the Standard Model Higgs field as the inflaton. At the same time, even small non-minimal coupling constant, $\xi\gtrsim10^{-3}$, brings the usual inflaton with quartic potential in agreement with the WMAP5 observations.",0810.3165v1 2008-10-27,Analysis of Firing Behaviors in Networks of Pulse-Coupled Oscillators with Delayed Excitatory Coupling,"For networks of pulse-coupled oscillators with delayed excitatory coupling, we analyze the firing behaviors depending on coupling strength and transmission delay. The parameter space consisting of strength and delay is partitioned into two regions. For one region, we derive a low bound of interspike intervals, from which three firing properties are obtained. However, this bound and these properties would no longer hold for another region. Finally, we show the different synchronization behaviors for networks with parameters in the two regions.",0810.4798v1 2008-11-21,Conditions for synchronizability in arrays of coupled linear systems,"Synchronization control in arrays of identical output-coupled continuous-time linear systems is studied. Sufficiency of new conditions for the existence of a synchronizing feedback law are analyzed. It is shown that for neutrally stable systems that are detectable form their outputs, a linear feedback law exists under which any number of coupled systems synchronize provided that the (directed, weighted) graph describing the interconnection is fixed and connected. An algorithm generating one such feedback law is presented. It is also shown that for critically unstable systems detectability is not sufficient, whereas full-state coupling is, for the existence of a linear feedback law that is synchronizing for all connected coupling configurations.",0811.3530v1 2008-11-22,Approximation of quantum graph vertex couplings by scaled Schrödinger operators on thin branched manifolds,"We discuss approximations of vertex couplings of quantum graphs using families of thin branched manifolds. We show that if a Neumann type Laplacian on such manifolds is amended by suitable potentials, the resulting Schr\""odinger operators can approximate non-trivial vertex couplings. The latter include not only the delta-couplings but also those with wavefunctions discontinuous at the vertex. We work out the example of the symmetric delta'-couplings and conjecture that the same method can be applied to all couplings invariant with respect to the time reversal.",0811.3707v1 2008-12-09,Probe of anomalous neutrino couplings to W and Z in medium energy setup of a beta-beam facility,"Capability of medium energy setup of a beta beam experiment to probe new physics contributions to neutrino-W and neutrino-Z couplings are investigated. We employ the effective lagrangian approach of Buchmuller and Wyler and obtain 95% confidence level limits on neutrino couplings to these gauge bosons without assuming the flavor universality of the coupling of neutrinos. We show that a beta beam facility can place 3 to 20 times more restrictive limits than present ones on the deviations from the electron neutrino couplings in the Standard Model.",0812.1722v2 2009-02-18,Scalar-tensor theories with pseudoscalar couplings,"We consider the scalar-tensor theories of gravity extended by the pseudoscalar couplings to matter and gauge fields and derive constraints on the CP-odd combinations of scalar and pseudoscalar couplings from laboratory spin precession experiments and from the evolution of photon polarization over cosmological distances. We show the complimentary character of local and cosmological constraints, and derive novel bounds on the pseudoscalar couplings to photons from the laboratory experiments. It is also shown that the more accurate treatment of the spin content of nuclei used in the spin precession experiments allows to tighten bounds on Lorentz-violating backgrounds coupled to the proton spin.",0902.3217v1 2009-02-25,A parallel splitting method for weakly coupled monotone inclusions,"A parallel splitting method is proposed for solving systems of coupled monotone inclusions in Hilbert spaces. Convergence is established for a wide class of coupling schemes. Unlike classical alternating algorithms, which are limited to two variables and linear coupling, our parallel method can handle an arbitrary number of variables as well as nonlinear coupling schemes. The breadth and flexibility of the proposed framework is illustrated through applications in the areas of evolution inclusions, dynamical games, signal recovery, image decomposition, best approximation, network flows, and variational problems in Sobolev spaces.",0902.4415v1 2009-04-01,Decay of Rabi oscillations by dipolar-coupled dynamical spin environments,"We investigate the Rabi oscillations decay of a spin decohered by a spin bath whose internal dynamics is caused by dipolar coupling between the bath spins. The decay form and rate as a function of the intra-bath coupling is studied analytically, and confirmed numerically. The decay in general has neither exponential/Gaussian or power-law form, and changes non-monotonically with the intra-bath coupling, decelerating for both slow and fast baths. The form and rate of Rabi oscillations decay can be used to experimentally determine the intra-bath coupling strength for a broad class of solid-state systems.",0904.0263v1 2009-04-16,"Large $N_c$ Expansion and the Parity Violating $π, N, Δ$ Couplings","In the limit of large $N_c$ we first consider the $N_c$ ordering of the various parity violating $\pi, N, \Delta$ couplings. Then we derive the relations among these couplings and consistency relations from the stability of these couplings under the chiral loop corrections with and without the mass splitting between $N$ and $\Delta$. Especially we find that $h_\Delta =-{3\over \sqrt{5}}h_\pi$ in the large $N_c$ limit, which correctly reproduces the relative sign and magnitude of the ""DDH"" values for these PV couplings.",0904.2418v1 2009-04-27,Rigorous derivation of the Kinetic/Fluid coupling involving a Kinetic layer on a toy problem,"In this article, we investigate the kinetic/fluid coupling on a toy model. We obtain it rigorously from a hydrodynamical limit. The idea is that at the level of the full kinetic model, the coupling is obvious. We then investigate the coupling obtained when passing into the limit. We show that, especially in presence of a shock stuck on the interface, the coupling involves a kinetic layer known as the Milne problem. Due to this layer, the limit process is quite delicate and some blow-up techniques are needed to ensure its strong convergence.",0904.4199v1 2009-05-14,Relaxation of Josephson qubits due to strong coupling to two-level systems,"We investigate the energy relaxation (T1) process of a qubit coupled to a bath of dissipative two-level fluctuators (TLF). We consider the fluctuators strongly coupled to the qubit both in the limit of spectrally separated single TLF's as well as in the limit of spectrally dense TLF's. We conclude that the avoided level crossings, usually attributed to very strongly coupled single TLF's, could also be caused by many weakly coupled spectrally dense fluctuators.",0905.2332v3 2009-05-19,Hyperbolicity of the Trace Map for a Strongly Coupled Quasiperiodic Schrodinger Operator,"We consider the trace map associated with the silver ratio Schrodinger operator as a diffeomorphism on the invariant surface associated with a given coupling constant and prove that the non-wandering set of this map is hyperbolic if the coupling is sufficiently large. As a consequence, for this values of the coupling constant, the local and global Hausdorff dimension and the local and global box counting dimension of the spectrum of this operator all coincide and are smooth functions of the coupling constant.",0905.3082v1 2009-08-20,Theory of anisotropic exchange in laterally coupled quantum dots,"The effects of spin-orbit coupling on the two-electron spectra in lateral coupled quantum dots are investigated analytically and numerically. It is demonstrated that in the absence of magnetic field the exchange interaction is practically unaffected by spin-orbit coupling, for any interdot coupling, boosting prospects for spin-based quantum computing. The anisotropic exchange appears at finite magnetic fields. A numerically accurate effective spin Hamiltonian for modeling spin-orbit-induced two-electron spin dynamics in the presence of magnetic field is proposed.",0908.2961v2 2009-09-13,Co-coupled synchronization of fractional-order unified chaotic systems,"Synchronization of fractional-order chaotic systems is a hot topic in the field of nonlinear study. The co-coupled synchronization between two fractional-order chaotic systems with different initial conditions is investigated in this paper. Based on Lyapunov stability principle and Gerschgorin theorem, the co-coupled synchronization theorem of fractional-order chaotic systems is deduced, and the range of coupling coefficients is confirmed for synchronization of fractional-order unified chaotic systems. By building up the synchronization simulation model on Simulink, the co-coupled synchronization between two fractional-order unified chaotic systems with different initial value is carried out, and the synchronization performances are analyzed, and the simulation results show that this synchronization method is effective.",0909.2410v1 2009-09-15,Adaptive coupling for achieving stable synchronization of chaos,"We consider synchronization of coupled chaotic systems and propose an adaptive strategy that aims at evolving the strength of the coupling to achieve stability of the synchronized evolution. We test this idea in a simple configuration in which two chaotic systems are unidirectionally coupled (a sender and a receiver) and we study conditions for the receiver to adaptively synchronize with the sender. Numerical simulations show that, under certain conditions, our strategy is successful in dynamically evolving the coupling strength until it converges to a value that is compatible with synchronization.",0909.2896v2 2009-11-16,Exchange coupling in transition-metal nano-clusters on Cu(001) and Cu(111) surfaces,"We present results of density-functional calculations on the magnetic properties of Cr, Mn, Fe and Co nano-clusters (1 to 9 atoms large) supported on Cu(001) and Cu(111). The inter-atomic exchange coupling is found to depend on competing mechanisms, namely ferromagnetic double exchange and antiferromagnetic kinetic exchange. Hybridization-induced broadening of the resonances is shown to be important for the coupling strength. The cluster shape is found to weaken the coupling via a mechanism that comprises the different orientation of the atomic d-orbitals and the strength of nearest-neighbour hopping. Especially in Fe clusters, a correlation of binding energy and exchange coupling is also revealed.",0911.3004v1 2009-11-16,Quintessence with quadratic coupling to dark matter,"We introduce a new form of coupling between dark energy and dark matter that is quadratic in their energy densities. Then we investigate the background dynamics when dark energy is in the form of exponential quintessence. The three types of quadratic coupling all admit late-time accelerating critical points, but these are not scaling solutions. We also show that two types of coupling allow for a suitable matter era at early times and acceleration at late times, while the third type of coupling does not admit a suitable matter era.",0911.3089v1 2010-01-13,Strong and weak coupling of two coupled qubits,"I investigate the dynamics and power spectrum of two coupled qubits (two-level systems) under incoherent continuous pump and dissipation. New regimes of strong coupling are identified, that are due to additional paths of coherence flow in the system. Dressed states are reconstructed even in the regime of strong decoherence. The results are analytical and offer an exact description of strong-coupling in presence of pumping and decay in a nontrivial (nonlinear) system.",1001.2201v1 2010-02-05,An analytic Pade-motivated QCD coupling,"We consider a modification of the Minimal Analytic (MA) coupling of Shirkov and Solovtsov. This modified MA (mMA) coupling reflects the desired analytic properties of the space-like observables. We show that an approximation by Dirac deltas of its discontinuity function $\rho$ is equivalent to a Pad\'e (rational) approximation of the mMA coupling that keeps its analytic structure. We propose a modification to mMA that, as preliminary results indicate, could be an improvement in the evaluation of low-energy observables compared with other analytic couplings.",1002.1264v1 2010-03-04,Resonant coupling of a Bose-Einstein condensate to a micromechanical oscillator,"We report experiments in which the vibrations of a micromechanical oscillator are coupled to the motion of Bose-condensed atoms in a trap. The interaction relies on surface forces experienced by the atoms at about one micrometer distance from the mechanical structure. We observe resonant coupling to several well-resolved mechanical modes of the condensate. Coupling via surface forces does not require magnets, electrodes, or mirrors on the oscillator and could thus be employed to couple atoms to molecular-scale oscillators such as carbon nanotubes.",1003.1126v1 2010-04-09,Superconducting Qubits Coupled to Torsional Resonators,"We propose a scheme of strong and tunable coupling between a superconducting phase qubit and nanomechanical torsional resonator. In our scheme the torsional resonator directly modulates the largest energy scale (the Josephson coupling energy) of the phase qubit, and the coupling strength is very large. We analyze the quantum correlation effects in the torsional resonator as a result of the strong coupling to the phase qubit.",1004.1497v2 2010-07-02,Higher Derivative Brane Couplings from T-Duality,"The Wess-Zumino coupling on D-branes in string theory is known to receive higher derivative corrections which couple the Ramond-Ramond potential to terms involving the square of the spacetime curvature tensor. Consistency with T-duality implies that the branes should also have four-derivative couplings that involve the NS-NS B-field. We use T-duality to predict some of these couplings. We then confirm these results with string worldsheet computations by evaluating disc amplitudes with insertions of one R-R and two NS-NS vertex operators.",1007.0441v2 2010-09-22,Coupling Circuit Resonators Among Themselves and To Nitrogen-Vacancy Centers in Diamond,"We propose a scheme to couple NV centers in diamond through coplanar waveguide resonators. The central conductor of the resonator is split into several pieces which are coupled strongly with each other via simple capacitive junctions or superconducting Josephson junctions. The NV centers are then put at the junctions. The discontinuity at the junctions induces a large local magnetic field, with which the NV centers are strongly coupled to the circuit resonator. The coupling strength $g$ between the resonator and the NV center is of order of $g/2\pi\sim 1$--$30\unit{MHz}$.",1009.4314v2 2010-12-01,Size dependent electric voltage-controlled magnetic anisotropy in multiferroic heterostructures: Interface-charge and strain co-mediated magnetoelectric coupling,"We present a phenomenological scheme to study the size-dependent electric voltage-controlled magnetic anisotropy in ferromagnetic (FM)/ferroelectric (FE) heterostructures. The FM layers are either metallic Fe(001), Ni(001), Co(0001), or half-metallic (La, Sr)MnO3 films. Two magnetoelectric mechanisms, i.e., interface-charge and strain-mediated couplings, are considered. We show that the interface-charge mediated coupling is the main mechanism for the magnetoelectic coupling when the FM film thickness is below a certain transition thickness dtr while the strain-mediated coupling dominates above dtr.",1012.0088v1 2010-12-17,Holographic superconductor models in the non-minimal derivative coupling theory,"We study a general class of holographic superconductor models via the St\""{u}ckelberg mechanism in the non-minimal derivative coupling theory in which the charged scalar field is kinetically coupling to Einstein's tensor. We explore the effects of the coupling parameter on the critical temperature, the order of phase transitions and the critical exponents near the second-order phase transition point. Moreover, we compute the electric conductive using the probe approximation and check the ratios $\omega_g/T_c$ for the different coupling parameters.",1012.3820v1 2011-01-06,All Possible Coupling Schemes in XY Spin Chains for Perfect State Transfer,"We investigate quantum state transfer in XY spin chains and propose a recursive procedure to construct the nonuniform couplings of these chains with arbitrary length to achieve perfect state transfer(PST). We show that this method is capable of finding all possible coupling schemes for PST. These schemes, without external control fields, only involve preengineered couplings but not dynamical control of them, so they can be simply realized experimentally. The analytical solutions provide all information for coupling design.",1101.1156v1 2011-02-24,Spatially Coupled LDPC Codes for Decode-and-Forward in Erasure Relay Channel,"We consider spatially-coupled protograph-based LDPC codes for the three terminal erasure relay channel. It is observed that BP threshold value, the maximal erasure probability of the channel for which decoding error probability converges to zero, of spatially-coupled codes, in particular spatially-coupled MacKay-Neal code, is close to the theoretical limit for the relay channel. Empirical results suggest that spatially-coupled protograph-based LDPC codes have great potential to achieve theoretical limit of a general relay channel.",1102.5087v2 2011-03-17,Heat transport and thermal rectification in quasi-one-dimensional systems,"In this work we investigate heat conduction along a ladder-model conformed by two coupled one dimensional lattices with different anharmonicity. We study how the interchain coupling modifies the thermal properties of the isolated systems. For a large enough coupling strength, we demonstrate that a harmonic lattice interacting with an anharmonic one is able to support a linear thermal gradient when it is connected to two heat reservoirs at different temperatures. We estimate this critical coupling by applying the self-consistent phonon theory (SCPT) to the anharmonic counterpart. By exchanging the heat baths connections between the harmonic and the anharmonic chains, our results show that the coupled system reveals as a thermal rectifier.",1103.3443v1 2011-03-31,Emergent patterns in a spin-orbit coupled spin-2 Bose-Einstein condensate,"The ground-state phases of a spin-orbit (SO) coupled atomic spin-2 Bose-Einstein condensate (BEC) are studied. Interesting density patterns spontaneously formed are widespread due to the competition between SO coupling and spin-dependent interactions like in a SO coupled spin-1 condensate. Unlike the case of spin-1 condensates, which are characterized by either ferromagnetic or polar phase in the absence of SO, spin-2 condensates can take a cyclic phase, where we find the patterns formed due to SO are square or triangular in their spin component densities for axial symmetric SO interaction. Both patterns are found to continuously evolve into striped forms with increased asymmetry of the SO coupling.",1103.6074v1 2011-06-07,Coupling of polaritons to vibrational modes of ultracold atoms in an optical lattice,"The coupling of internal electronic excitations to vibrational modes of the external motion of ultracold atoms in an optical lattice is studied here in using a perturbation expansion in small atomic displacements. In the Mott insulator case with one atom per site, the resonance dipole-dipole coupling between neighboring sites can induce emission and absorption of vibrational quanta. Within a cavity in the strong exciton-photon coupling regime such coupling results in polariton-vibration interactions, which create a significant thermalization mechanism for polaritons toward their minimum energy, and leading to motional heating of the lattice atoms.",1106.1272v1 2011-07-23,Electroweak effective couplings for future precision experiments,"The leading hadronic effects in electroweak theory derive from vacuum polarization which are non-perturbative hadronic contributions to the running of the gauge couplings, the electromagnetic alpha_{em}(s) and the SU(2)_L coupling alpha_2(s). I will report on my recent package ""alphaQED"", which besides the effective fine structure constant alpha_{em}(s) also allows for a fairly precise calculation of the SU(2)_L gauge coupling alpha_2(s). I will briefly review the role, future requirements and possibilities. Applied together with the ""Rhad"" package by Harlander and Steinhauser, the package allows to calculate all SM running couplings as well as running sin^2 Theta versions with state-of-the-art accuracy.",1107.4683v1 2011-09-09,Covering relations for coupled map networks,"Following [6,12], we study coupled map networks over arbitrary finite graphs. An estimate from below for a topological entropy of a perturbed coupled map network via a topological entropy of an unperturbed network by making use of the covering relations for coupled map networks is obtained. The result is quite general, particularly no assumptions on hyperbolicity of a local dynamics or linearity of coupling are made.",1109.1931v1 2011-09-09,Standard Model gauge coupling unification,"We study the low energy evolution of coupling constants of the standard model and show that gauge coupling unification can be achieved at the electroweak scale with a suitable normalization. We choose the grand unification group to be the semidirect product of Spin(8) by S_3. In this case the three low energy gauge couplings and the two scalar self-couplings are determined in terms of two independent parameters. In particular, it gives a precise prediction for the mass of the Higgs boson.",1109.2052v3 2011-09-12,A note on the coupling of the techni-dilaton to the weak bosons,"In this note, we study the coupling of the techni-dilaton to the weak bosons. We consider two cases: (1) The dilaton directly couples to the weak bosons similarly to the SM. (2) The coupling in question is effectively induced only through the techni-fermion loops. In both cases, we find that the coupling is essentially determined by the mass-squared of the weak bosons over the dilaton decay constant.",1109.2554v3 2011-09-18,A Coupling Argument for the Random Transposition Walk,"This paper explores the mixing time of the random transposition walk on the symmetric group. While it has long been known that this walk mixes in order n*log(n) time, this result has not previously been attained using coupling. A coupling argument showing the correct order mixing time is presented. This is accomplished by first projecting to conjugacy classes, and then using the Bubley-Dyer path coupling construction. In order to obtain appropriate bounds on the time it takes the path coupling to meet, ideas from Schramm's paper ""Compositions of Random Transpositions"" are used.",1109.3915v1 2011-10-20,Search for anomalous Wtb couplings in single top quark production in ppbar collisions at sqrt(s) = 1.96 TeV,"We present new direct constraints on a general $Wtb$ interaction using data corresponding to an integrated luminosity of 5.4 fb$^{-1}$ collected by the D0 detector at the Tevatron $p\bar{p}$ collider. The standard model provides a purely left-handed vector coupling at the $Wtb$ vertex, while the most general, lowest dimension Lagrangian allows right-handed vector and left- or right-handed tensor couplings as well. We obtain precise limits on these anomalous couplings by comparing the data to the expectations from different assumptions on the $Wtb$ coupling.",1110.4592v2 2012-02-16,Ground state and excitation spectra of a strongly correlated lattice by the coupled cluster method,"We apply Coupled Cluster Method to a strongly correlated lattice and develop the Spectral Coupled Cluster equations by finding an approximation to the resolvent operator, that gives the spectral response for an certain class of probe operators. We apply the method to a $MnO_2$ plane model with a parameters choice which corresponds to previous experimental works and which gives a non-nominal symmetry ground state. We show that this state can be observed using our Spectral Coupled Cluster Method by probing the Coupled Cluster solution obtained from the nominal reference state. In this case one observes a negative energy resonance which corresponds to the true ground state.",1202.3537v3 2012-02-29,Dipole Coupling Effect of Holographic Fermion in Charged Dilatonic Gravity,"In this note, we study the dipole coupling effect of holographic fermion in a charged dilatonic black hole proposed by Gubser and Rocha (arXiv:0911.2898). It is found that the property of Fermi liquid is rigid under perturbation of dipole coupling, and the Fermi momentum is linearly shifted. A gap is dynamically generated as the coupling becomes large enough and the Fermi surface ceases to exist as the bulk dipole coupling further increases.",1202.6539v1 2012-03-09,Dynamical locality of the nonminimally coupled scalar field and enlarged algebra of Wick polynomials,"We discuss dynamical locality in two locally covariant quantum field theories, the nonminimally coupled scalar field and the enlarged algebra of Wick polynomials. We calculate the relative Cauchy evolution of the enlarged algebra, before demonstrating that dynamical locality holds in the nonminimally coupled scalar field theory. We also establish dynamical locality in the enlarged algebra for the minimally coupled massive case and the conformally coupled massive case.",1203.2151v1 2012-07-11,Enhancing Synchrony in Chaotic Oscillators by Dynamic Relaying,"In a chain of mutually coupled oscillators, the coupling threshold for synchronization between the outermost identical oscillators decreases when a type of impurity (in terms of parameter mismatch) is introduced in the inner oscillator(s). The outer oscillators interact indirectly via dynamic relaying, mediated by the inner oscillator(s). We confirm this enhancing of critical coupling in the chaotic regimes of R\""ossler system in absence of coupling delay and in Mackey-Glass system with delay coupling. The enhancing effect is experimentally verified in electronic circuit of R\""ossler oscillators.",1207.2563v1 2012-08-29,Radio-frequency spectroscopy of weakly bound molecules in spin-orbit coupled atomic Fermi gases,"We investigate theoretically radio-frequency spectroscopy of weakly bound molecules in an ultracold spin-orbit-coupled atomic Fermi gas. We consider two cases with either equal Rashba and Dresselhaus coupling or pure Rashba coupling. The former system has been realized very recently at Shanxi University [Wang et al., arXiv:1204.1887] and MIT [Cheuk et al., arXiv:1205.3483]. We predict realistic radio-frequency signals for revealing the unique properties of anisotropic molecules formed by spin-orbit coupling.",1208.5841v1 2012-09-12,Highly efficient coupling of photons from nanoemitters into single-mode optical fibers,"Highly efficient coupling of photons from nanoemitters into single-mode optical fibers is demonstrated using tapered fibers. 7.4 +/- 1.2 % of the total emitted photons from single CdSe/ZnS nanocrystals were coupled into a 300-nm-diameter tapered fiber. The dependence of the coupling efficiency on the taper diameter was investigated and the coupling efficiency was found to increase exponentially with decreasing diameter. This method is very promising for nanoparticle sensing and single-photon sources.",1209.2474v1 2012-10-01,Electron-phonon superconductivity and charge density wave instability in the layered titanium-based pnictide BaTi$_2$Sb$_2$O,"I present the results of first principles calculations of the phonon dispersions and electron-phonon coupling for BaTi$_2$Sb$_2$O. The phonon dispersions show a weak lattice instability near the zone corners that leads to a charge-density wave phase. The calculations of the electron-phonon coupling reveal strong coupling, especially to the in-plane Ti modes. The total coupling is large enough to readily explain the superconductivity in this compound. As the Fermi surfaces are disconnected with different orbital character weights, this compound is likely to host a multiband superconductivity.",1210.0499v2 2012-10-27,Theory of electromechanical coupling in dynamical graphene,"We study the coupling between mechanical motion and Dirac electrons in a dynamical sheet of graphene. We show that this coupling can be understood in terms of an effective gauge field acting on the electrons, which has two contributions: quasistatic and purely dynamic of the Berry-phase origin. As is well known, the static gauge potential is odd in the K and K' valley index, while we find the dynamic coupling to be even. In particular, the mechanical fluctuations can thus mediate an indirect coupling between charge and valley degrees of freedom.",1210.7384v1 2012-11-27,Bootstrap and momentum transfer dependence in small x evolution equations,"Using Monte Carlo integration techniques, we investigate running coupling effects compatible with the high energy bootstrap condition to all orders in the strong coupling in evolution equations valid at small values of Bjorken x in deep inelastic scattering. A model for the running of the coupling with analytic behavior in the infrared region and compatible with power corrections to jet observables is used. As a difference to the fixed coupling case, where the momentum transfer acts as an effective strong cut-off of the diffusion to infrared scales, in our running coupling study the dependence on the momentum transfer is much milder.",1211.6332v1 2012-12-04,Selectable linear or quadratic coupling in an optomechanical system,"There has been much interest recently in the analysis of optomechanical systems incorporating dielectric nano- or microspheres inside a cavity field. We analyse here the situation when one of the mirrors of the cavity itself is also allowed to move. We reveal that the interplay between the two oscillators yields a cross-coupling that results in, e.g., appreciable cooling and squeezing of the motion of the sphere, despite its nominal quadratic coupling. We also discuss a simple modification that would allow this cross-coupling to be removed at will, thereby yielding a purely quadratic coupling for the sphere.",1212.0641v1 2012-12-12,Coupling mechanism between microscopic two-level system and superconducting qubits,"We propose a scheme to clarify the coupling nature between superconducting Josephson qubits andmicroscopic two-level systems. Although dominant interest in studying two-level systems was in phase qubits previously, we find that the sensitivity of the generally used spectral method in phase qubits is not sufficient to evaluate the exact form of the coupling. On the contrary, our numerical calculation shows that the coupling strength changes remarkably with the flux bias for a flux qubit, providing a useful tool to investigate the coupling mechanism between the two-level systems and qubits.",1212.2687v1 2012-12-16,Sensitivity enhancement in optical micro-tube resonator sensors via mode coupling,"A liquid filled, low refractive index material inner-coated silica micro-tube has been proposed and studied as a coupled micro-resonator sensor to greatly enhance biochemical sensor sensitivity. Its unique coupling phenomenon has been analyzed and utilized to boost the refractive index sensitivity of the device to 967nm/RIU. Through optimization of the coupling strength between the two microresonators, further improvement in refractive index sensitivity up to 1100nm/RIU has been achieved. This mode coupling strategy allows us to design robust, thick-walled micro-tube sensors with ultra-high sensitivity which is useful in practical biochemical sensing applications.",1212.3851v1 2013-01-24,A Potential Theory of General Spatially-Coupled Systems via a Continuum Approximation,"This paper analyzes general spatially-coupled (SC) systems with multi-dimensional coupling. A continuum approximation is used to derive potential functions that characterize the performance of the SC systems. For any dimension of coupling, it is shown that, if the boundary of the SC systems is fixed to the unique stable solution that minimizes the potential over all stationary solutions, the systems can approach the optimal performance as the number of coupled systems tends to infinity.",1301.5728v2 2013-02-03,Invertible coupled KdV and coupled Harry Dym hierarchies,"In this paper we discuss the conditions under which the coupled KdV and coupled Harry Dym hierarchies possess inverse (negative) parts. We further investigate the structure of nonlocal parts of tensor invariants of these hierarchies, in particular, the nonlocal terms of vector fields, conserved one-forms, recursion operators, Poisson and symplectic operators. We show that the invertible cKdV hierarchies possess Poisson structures that are at most weakly nonlocal while coupled Harry Dym hierarchies have Poisson structures with nonlocalities of the third order.",1302.0526v1 2013-02-18,Controlled coupling of photonic crystal cavities using photochromic tuning,"We present a method to control the resonant coupling interaction in a coupled-cavity photonic crystal molecule by using a local and reversible photochromic tuning technique. We demonstrate the ability to tune both a two-cavity and a three-cavity photonic crystal molecule through the resonance condition by selectively tuning the individual cavities. Using this technique, we can quantitatively determine important parameters of the coupled-cavity system such as the photon tunneling rate. This method can be scaled to photonic crystal molecules with larger numbers of cavities, which provides a versatile method for studying strong interactions in coupled resonator arrays.",1302.4322v1 2013-02-27,Ferromagnetic to antiferromagnetic transition of one-dimensional spinor Bose gases with spin-orbit coupling,"We have analytically solved one-dimensional interacting two-component bosonic gases with spin-orbit (SO) coupling by the Bethe-ansatz method. Through a gauge transformation, the effect of SO coupling is incorporated into a spin-dependent twisted boundary condition. Our result shows that the SO coupling can influence the eigenenergy in a periodical pattern. The interplay between interaction and SO coupling may induce the energy level crossing for the ground state, which leads to a transition from the ferromagnetic to antiferromagnetic state.",1302.6901v2 2013-03-15,Exact black hole solution for scale dependent gravitational couplings and the corresponding coupling flow,"We study a black hole solution for the generalized Einstein Hilbert action with scale dependent couplings G(r) and Lambda(r). The form of the couplings is not imposed, but rather deduced from the existence of a non trivial symmetrical solution. A classical-like choice of the integration constants is found. Finally, the induced flow of the couplings is derived and compared to the flow that is obtained in the context of the exact renormalization group approach.",1303.3892v1 2013-04-12,Probing Anomalous HZZ Couplings at the LHeC,"We examine the sensitivity to the couplings of the Higgs boson to neutral gauge bosons in a model independent way at the Large Hadron electron Collider (LHeC). We have obtained the constraints on anomalous couplings for $HZZ$ vertex via the process $e^{-}p\rightarrow e^{-}HqX$. We find the accessible limits of the anomalous coupling $b_{Z}$ as $(-0.12,0.43)$ and $(-0.10,0.33)$, while the limits on coupling $\beta_{Z}$ as ($-0.32,0.32$) and $(-0.24,0.24)$ at the electron beam energy $E_{e}=60$ GeV and $E_{e}=140$ GeV, respectively.",1304.3616v2 2013-04-29,Coupled-channel scattering in 1+1 dimensional lattice model,"Based on the Lippmann-Schwinger equation approach, a generalized L\""uscher's formula in 1+1 dimensions for two particles scattering in both the elastic and coupled-channel cases in moving frames is derived. A 2D coupled-channel scattering lattice model is presented, the model represents a two-coupled-channel resonant scattering scalars system. The Monte Carlo simulation is performed on finite lattices and in various moving frames. The 2D generalized L\""uscher's formula is used to extract the scattering amplitudes for the coupled-channel system from the discrete finite-volume spectrum.",1304.7812v1 2013-05-08,Physics at the ILC with focus mostly on Higgs physics,"Physics at the ILC is reviewed focusing mostly on Higgs physics. It is emphasized that at the ILC it is possible to measure the $hZZ$ coupling totally model independently, which in turn allows model-independent normalization of various branching ratio measurements and consequently the absolute measurements of corresponding couplings. Combining them with the measurements of the top Yukawa coupling and the Higgs self-coupling at higher energies, the full ILC program is shown to allow a precision test of the mass-coupling relation.",1305.1692v2 2013-05-26,Nonlinearity Induced Critical Coupling,"We study a critically coupled system (Opt. Lett., \textbf{32}, 1483 (2007)) with a Kerr-nonlinear spacer layer. Nonlinearity is shown to inhibit null-scattering in a critically coupled system at low powers. However, a system detuned from critical coupling can exhibit near-complete suppression of scattering by means of nonlinearity-induced changes in refractive index. Our studies reveal clearly an important aspect of critical coupling as a delicate balance in both the amplitude and the phase relations, while a nonlinear resonance in dispersive bistability concerns only the phase.",1305.5983v1 2013-05-29,Light scattering from coupled plasmonic nanospheres on a substrate,"An efficient numerical method based on half-space Green function and spherical harmonics expansion is used to study the light scattering from coupled multiple nanospheres on a substrate. The ellipsometric spectra for various geometries of coupled Au nanospheres are calculated and analyzed to realize the effects of plasmonic coupling of closely-spaced nanospheres. With only a few parameters to describe the distribution of various coupled nanosphere clusters embedded in a random distribution of nanospheres, the calculated ellipsometric spectra can fit the experimental data very well. This illustrates that our realistic model calculations can be used for determination of the distribution of nanospheres on a substrate or embedded in multilayer structures such as biological samples.",1305.6764v1 2013-12-11,Spin-orbit coupling in quantum gases,"Spin-orbit coupling links a particle's velocity to its quantum mechanical spin, and is essential in numerous condensed matter phenomena, including topological insulators and Majorana fermions. In solid-state materials, spin-orbit coupling originates from the movement of electrons in a crystal's intrinsic electric field, which is uniquely prescribed. In contrast, for ultracold atomic systems, the engineered ""material parameters"" are tuneable: a variety of synthetic spin-orbit couplings can be engineered on demand using laser fields. Here we outline the current experimental and theoretical status of spin-orbit coupling in ultracold atomic systems, discussing unique features that enable physics impossible in any other known setting.",1312.3292v1 2014-01-10,Delay-induced patterns in a two-dimensional lattice of coupled oscillators,"We show how a variety of stable spatio-temporal periodic patterns can be created in 2D-lattices of coupled oscillators with non-homogeneous coupling delays. A ""hybrid dispersion relation"" is introduced, which allows studying the stability of time-periodic patterns analytically in the limit of large delay. The results are illustrated using the FitzHugh-Nagumo coupled neurons as well as coupled limit cycle (Stuart-Landau) oscillators.",1401.2325v1 2014-01-09,Coherent Electronic Coupling in Atomically Thin MoSe2,"We report the first direct spectroscopic evidence for coherent electronic coupling between excitons and trions in atomically thin transition metal dichalcogenides, specifically monolayer MoSe2. Signatures of coupling appear as isolated cross-peaks in two-color pump-probe spectra, and the lineshape of the peaks reveals that the coupling originates from many-body interactions. Excellent agreement between the experiment and density matrix calculations suggests the formation of a correlated exciton-trion state due to their coupling.",1401.2909v1 2014-01-24,Properties of spatial coupling in compressed sensing,"In this paper we address a series of open questions about the construction of spatially coupled measurement matrices in compressed sensing. For hardware implementations one is forced to depart from the limiting regime of parameters in which the proofs of the so-called threshold saturation work. We investigate quantitatively the behavior under finite coupling range, the dependence on the shape of the coupling interaction, and optimization of the so-called seed to minimize distance from optimality. Our analysis explains some of the properties observed empirically in previous works and provides new insight on spatially coupled compressed sensing.",1401.6380v1 2014-02-03,Coupling constants of bottom (charmed) mesons with pion from three point QCD sum rules,"In this article, the three point QCD sum rules is used to compute the strong coupling constants of vertices containing the strange bottomed ( charmed ) mesons with pion. The coupling constants are calculated, when both the bottom ( charm ) and pion states are off-shell. A comparison of the obtained results of coupling constants with the existing predictions is also made. Key words: strong coupling constant, meson, QCD sum rules, bottom, charm.",1402.0296v1 2014-02-06,Dynamics and non-equilibrium steady state in a system of coupled harmonic oscillators,"A system of two coupled oscillators, each of them coupled to an independent reservoir, is analysed. The analytical solution of the non-rotating wave master equation is obtained in the high-temperature and weak coupling limits. No thermal entanglement is found in the high-temperature limit. In the weak coupling limit the system converges to an entangled non-equilibrium steady state. A critical temperature for the appearance of quantum correlations is found.",1402.1477v1 2014-04-01,Optimal rectification by strongly coupled spins,"We study heat transport in a pair of strongly coupled spins. In particular, we present a condition for optimal rectification, i.e., flow of heat in one direction and complete isolation in the opposite direction. We show that the strong-coupling formalism is necessary for correctly describing heat flow in a wide range of parameters, including moderate to low couplings. We present a situation in which the strong-coupling formalism predicts optimal rectification whereas the phenomenological approach predicts no heat flow in any direction, for the same parameter values.",1404.0348v2 2014-04-14,From inflation to late time acceleration with a decaying vacuum coupled to radiation or matter,"We consider General Relativity with matter and radiation, one of these fluids being coupled to vacuum. We find that Universe dynamics starts by an inflation phase if the coupled fluid has a negative energy density at early time. Then, there is always a finite scale factor singularity but when vacuum and matter are coupled and matter density behaves like a negative radiation density. Moreover, the convergence to the LCDM model is clearly easier to reach when vacuum is coupled to matter rather than to radiation. Two classes of theories are studied to illustrate these results.",1404.3518v1 2014-07-15,Quantum model of coupled intersubband plasmons,"We present a quantum model to calculate the dipole-dipole coupling between electronic excitations in the conduction band of semiconductor quantum wells. We demonstrate that the coupling depends on a characteristic length, related to the overlap between microscopic current densities associated with each electronic excitation. As a result of the coupling, a macroscopic polarization is established in the quantum wells, corresponding to one or few bright collective modes of the electron gas. Our model is applied to derive a sum rule and to investigate the interplay between tunnel coupling and Coulomb interaction in the absorption spectrum of a dense electron gas.",1407.3923v1 2014-07-22,Current-driven dynamics of coupled domain walls in a synthetic antiferromagnet,"We develop the theory of magnetic domain wall motion in coupled double-layer systems where electrons can hop between the layers giving rise to an antiferromagnetic coupling. We demonstrate that the force from the interlayer coupling drives the walls and the effect of the extrinsic pinning is greatly reduced if the domain walls are initially separated. The threshold current density for metastable spin-aligned configurations is also much lower. We conclude that the interlayer coupling has a significant effect on domain wall mobility in double-layer systems.",1407.5805v1 2014-07-30,Stability of the shadow projection and the left-curtain coupling,"The (left-)curtain coupling, introduced by Beiglb\""ock and the author is an extreme element of the set of ""martingale"" couplings between two real probability measures in convex order. It enjoys remarkable properties with respect to order relations and a minimisation problem inspired by the theory of optimal transport. An explicit representation and a number of further noteworthy attributes have recently been established by Henry-Labord\`ere and Touzi. In the present paper we prove that the curtain coupling depends continuously on the prescribed marginals and quantify this with Lipschitz estimates. Moreover, we investigate the Markov composition of curtain couplings as a way of associating Markovian martingales with peacocks.",1407.8009v2 2014-09-27,Complete achromatic optical switching between two waveguides with a sign flip of the phase mismatch,"We present a two-waveguide coupler which, realizes complete achromatic all-optical switching. The coupling of the waveguides has a hyperbolic-secant shape while the phase mismatch has a sign flip at the maximum of the coupling. We derive an analytic solution for the electric field propagation using coupled mode theory and show that the light switching is robust again small-to-moderate variations in the coupling and phase mismatch. Thus, we realize an achromatic light switching between the two waveguides. We further consider the extended case of three coupled waveguides in an array and pay special attention to the case of equal achromatic light beam splitting.",1409.7757v1 2014-10-19,Monotonicity of Avoidance Coupling on $K_N$,"Answering a question by Angel, Holroyd, Martin, Wilson and Winkler, we show that the maximal number of non-colliding coupled simple random walks on the complete graph $K_N$, which take turns, moving one at a time, is monotone in $N$. We use this fact to couple $\lceil \frac N4 \rceil$ such walks on $K_N$, improving the previous $\Omega(N/\log N)$ lower bound of Angel et al. We also introduce a new generalization of simple avoidance coupling which we call partially ordered simple avoidance coupling and provide a monotonicity result for this extension as well.",1410.5032v2 2014-11-24,Boundary conditions for conformally coupled scalar in AdS$_4$,"We consider conformally coupled scalar with $\phi^4$ coupling in AdS$_4$ and study its various boundary conditions on AdS boundary. We have obtained perturbative solutions of equation of motion of the conformally coupled scalar with power expansion order by order in $\phi^4$ coupling $\lambda$ up to $\lambda^2$ order. In its dual CFT, we get 2,4 and 6 point functions by using this solution with Dirichlet and Neumann boundary conditions via AdS/CFT dictionary. We also consider marginal deformation on AdS boundary and get its on-shell and boundary effective actions.",1411.6356v2 2014-12-28,The Phase-space analysis of scalar fields with non-minimally derivative coupling,"We perform a dynamical analysis for the exponential scalar field with non-minimally derivative coupling. For the quintessence case, the stable fixed points are the same with and without the non-minimally derivative coupling. For the phantom case, the attractor with dark energy domination exists for the minimal coupling only. For the non-minimally derivative coupling without the standard canonical kinetic term, only the de-Sitter attractor exists, and the dark matter solution is unstable.",1412.8152v2 2015-01-26,Deviation of Yukawa Coupling in Gauge-Higgs Unification,"We study the deviation of yukawa coupling in the gauge-Higgs unification scenario from the Standard Model one. Taking into account the brane mass terms necessary for generating the flavor mixing and removing the exotic massless fermions, we derive an analytic formula determining the KK mass spectrum and yukawa coupling. Applying the obtained results to the tau and bottom yukawa couplings, we numerically calculate the ratio of the yukawa couplings in the gauge-Higgs unification and in the Standard Model.",1501.06230v1 2015-02-22,Inter-community resonances in multifrequency ensembles of coupled oscillators,"We generalize the Kuramoto model of globally coupled oscillators to multifrequency communities. A situation when mean frequencies of two subpopulations are close to resonance 2:1 is considered in detail. We derive uniformly rotating solutions describing synchronization inside communities and between them. Remarkably, cross-coupling between the frequency scales can promote synchrony even when ensembles are separately asynchronous. We also show that the transition to synchrony due to the cross-coupling is accompanied by a huge multiplicity of distinct synchronous solutions what is directly related to a multi-branch entrainment. On the other hand, for synchronous populations, the cross-frequency coupling can destroy a phase-locking and lead to chaos of mean fields.",1502.06193v1 2015-03-17,Multi-photon quantum communication in quantum networks,"We propose and analyze a multiphoton-state coherent transport protocol in a coupled-resonator quantum network. A multiphoton swap gate between two antipodes can be achieved with neither external modulation nor coupling strength engineering. Moreover, we extend this result to a coupled-resonator chain of arbitrary length with different coupling strengths. Effects of decoherence via quantum nondemolition interaction are studied with sources including vacuum quantum fluctuation and bath thermal excitations when the bath is in the thermal equilibrium state. These observations are helpful to understand the decoherence effects on quantum communication in quantum coupled-resonator systems.",1503.04924v1 2015-05-04,Probing $HZγ$ and $Hγγ$ Anomalous Couplings in the Process of $e^+e^- \to Hγ$,"We propose to measure the $HZ\gamma$ and $H\gamma\gamma$ anomalous couplings in the process of $e^{+}e^{-}\rightarrow H\gamma$ with the sequential decay of $H\to b{\bar b}$. The discovery potential of observing the anomalous couplings are explored in details. Our study shows that the electron-positron collider has a great potential of testing the $HZ\gamma$ and $H\gamma\gamma$ couplings. Conservative bounds on the two anomalous couplings are also derived when no new physics signal were detected on top of the SM backgrounds.",1505.00654v1 2015-05-20,A General Integrable Nonlocal Coupled Nonlinear Schrödinger Equation,"In this paper, we investigate a general integrable nonlocal coupled nonlinear schr\""odinger (NLS) system with the the parity-time (PT) symmetry, which contains not only the nonlocal self-phase modulation and the nonlocal cross-phase modulation, but also the nonlocal four-wave mixing terms. This nonlocal coupled NLS system is a nonlocal version of a coupled NLS system. The general Nth Darboux transformation for the nonlocal coupled NLS equation is constructed. By using the Darboux transformation, its soliton solutions are obtained.",1505.05311v1 2015-05-26,Higgs boson couplings as a probe of new physics,"Precise measurements of various coupling constants of the 125 GeV Higgs boson $h$ are one of the most important and solid methods to determine the structure of the Higgs sector. If we find deviations in the $h$ coupling constants from the standard model predictions, it can be an indirect evidence of the existence of additional Higgs bosons in non-minimal Higgs sectors. Furthermore, we can distinguish non-minimal Higgs sectors by measuring a pattern of deviations in various $h$ couplings. In this talk, we show patterns of the deviations in several simple non-minimal Higgs sectors, especially for the gauge $hVV$ and Yukawa $hf\bar{f}$ couplings. This talk is based on the paper [1].",1505.06886v1 2015-06-09,Identification of spin wave modes strongly coupled to a co-axial cavity,"We demonstrate, at room temperature, the strong coupling of the fundamental and non-uniform magnetostatic modes of an yttrium iron garnet (YIG) ferrimagnetic sphere to the electromagnetic modes of a co-axial cavity. The well-defined field profile within the cavity yields a specific coupling strength for each magnetostatic mode. We experimentally measure the coupling strength for the different magnetostatic modes and, by calculating the expected coupling strengths, are able to identify the modes themselves.",1506.02902v1 2015-06-19,Noise-induced synchronization in bidirectionally coupled type-I neurons,"We present here some studies on noise-induced order and synchronous firing in a system of bidirectionally coupled generic type-I neurons. We find that transitions from unsynchronized to completely synchronized states occur beyond a critical value of noise strength that has a clear functional dependence on neuronal coupling strength and input values. For an inhibitory-excitatory (IE) synaptic coupling, the approach to a partially synchronized state is shown to vary qualitatively depending on whether the input is less or more than a critical value. We find that introduction of noise can cause a delay in the bifurcation of the firing pattern of the excitatory neuron for IE coupling.",1506.06091v1 2015-09-02,Universal lineshapes at the crossover between weak and strong critical coupling in Fano-resonant coupled oscillators,"In this article we discuss a model describing key features concerning the lineshapes and the coherent absorption conditions in Fano-resonant dissipative coupled oscillators. The model treats on the same footing the weak and strong coupling regimes, and includes the critical coupling concept, which is of great relevance in numerous applications; in addition, the role of asymmetry is thoroughly analyzed. Due to the wide generality of the model, which can be adapted to various frameworks like nanophotonics, plasmonics, and optomechanics, we envisage that the analytical formulas presented here will be crucial to effectively design devices and to interpret experimental results.",1509.00593v1 2015-11-27,Long-range Synchronization of Nanomechanical Oscillators with Light,"We experimentally demonstrate mutual synchronization of two free-running nanomechanical oscillators separated by an effective distance of 30 meters and coupled through light. Due to the finite speed of light, the large separation introduces a significant coupling delay of 139 nanoseconds, approximately four and a half times the mechanical oscillation time period. We reveal multiple stable states of synchronized oscillations, enabled by delayed coupling, with distinct synchronization frequency in the coupled system. These states are accessed by tuning independently the directional coupling strengths. Our results demonstrate rich dynamics and could enable applications in reconfigurable radio-frequency networks and novel computing concepts.",1511.08536v2 2016-02-13,Coupled gyration modes and propagation in one-dimensional periodic skyrmion arrays as reliable information carrier,"We report on a micromagnetic numerical simulation study of dynamic couplings between neighboring skyrmions in narrow-width nanostrips. We explored the coupled gyration modes and their characteristic dispersions in terms of the interdistance between the neighboring skyrmions. The application of perpendicular magnetic fields, importantly, allows for control/modification of the dispersion of the coupled modes. Coupled skyrmion gyration modes provide a new type of efficient, reliable, fast, low-power-consumption information-signal propagation in narrow-width straight and curved nanostrips, as driven predominantly by the exchange interaction between individual nano-scale skyrmions.",1602.04349v1 2016-02-21,Kramers turnover: from energy diffusion to spatial diffusion using metadynamics,"We consider the rate of transition for a particle between two metastable states coupled to a thermal environment for various magnitudes of the coupling strength, using the recently proposed infrequent metadynamics approach (Tiwary and Parrinello, Phys. Rev. Lett. 111, 230602 (2013)). We are interested in understanding how this approach for obtaining rate constants performs as the dynamics regime changes from energy diffusion to spatial diffusion. Reassuringly, we find that the approach works remarkably well for various coupling strengths in the strong coupling regime, and to some extent even in the weak coupling regime.",1602.06588v1 2016-04-03,Reconstruction of chaotic neural network from observed firing rates,"Randomly coupled neural fields demonstrate chaotic variation of firing rates, if the coupling is strong enough, as has been shown by Sompolinsky et. al [Phys. Rev. Lett., v. 61, 259 (1988)]. We present a method for reconstruction of the coupling matrix from the observations of the chaotic firing rates. The approach is based on the particular property of the nonlinearity in the coupling, as the latter is determined by a sigmoidal gain function. We demonstrate that for a large enough data set, the method gives an accurate estimation of the coupling matrix and of other parameters of the system, including the gain function.",1604.00619v1 2016-06-21,Dipolar polaritons in microcavity-embedded coupled quantum wells in electric and magnetic fields,"We present a precise calculation of spatially-indirect exciton states in semiconductor coupled quantum wells and polaritons formed from their coupling to the optical mode of a microcavity. We include the presence of electric and magnetic fields applied perpendicular to the quantum well plane. Our model predicts the existence of polaritons which are in the strong coupling regime and at the same time possess a large static dipole moment. We demonstrate, in particular, that a magnetic field can compensate for the reduction in light-matter coupling that occurs when an electric field impresses a dipole moment on the polariton.",1606.06479v1 2016-07-13,Quasinonlocal coupling of nonlocal diffusions,"We developed a new self-adjoint, consistent, and stable coupling strategy for nonlocal diffusion models, inspired by the quasinonlocal atomistic-to-continuum method for crystalline solids. The proposed coupling model is coercive with respect to the energy norms induced by the nonlocal diffusion kernels as well as the $L^2$ norm, and it satisfies the maximum principle. A finite difference approximation is used to discretize the coupled system, which inherits the property from the continuous formulation. Furthermore, we design a numerical example which shows the discrepancy between the fully nonlocal and fully local diffusions, whereas the result of the coupled diffusion agrees with that of the fully nonlocal diffusion.",1607.03940v2 2017-03-05,Protecting a nuclear spin from a noisy electron spin in diamond,"Although a nuclear spin is weakly coupled to its environment, due to its small gyromagnetic ratio, its coherence time is limited by the hyperfine coupling to a nearby noisy electron. Here, we propose to utilize continuous dynamical decoupling to refocus the coupling to the electron. If the random phase accumulated by the nuclear spin through the reduced coupling terms is sufficient small, we can increase the nuclear coherence time. Initially, we demonstrate this on a simple case with a two-level electron spin, while taking all relevant hyperfine coupling terms and noise terms into account. We then extend the analysis to a nitrogen-vacancy center in diamond having a three level structure.",1703.01596v1 2017-03-30,Coupled qubits as a quantum heat switch,"We present a quantum heat switch based on coupled superconducting qubits, connected to two $LC$ resonators that are terminated by resistors providing two heat baths. To describe the system we use a standard second order master equation with respect to coupling to the baths. We find that this system can act as an efficient heat switch controlled by the applied magnetic flux. The flux influences the energy level separations of the system, and under some conditions, the finite coupling of the qubits enhances the transmitted power between the two baths, by an order of magnitude under realistic conditions. At the same time, the bandwidth at maximum power of the switch formed of the coupled qubits is narrowed.",1703.10499v1 2017-08-05,Low variance couplings for stochastic models of intracellular processes with time-dependent rate functions,"A number of coupling strategies are presented for stochastically modeled biochemical processes with time-dependent parameters. In particular, the stacked coupling is introduced and is shown via a number of examples to provide an exceptionally low variance between the generated paths. This coupling will be useful in the numerical computation of parametric sensitivities and the fast estimation of expectations via multilevel Monte Carlo methods. We provide the requisite estimators in both cases.",1708.01813v2 2017-08-10,Multifractal invariant measures in expanding piecewise linear coupled maps,"We analyze invariant measures of two coupled piecewise linear and everywhere expanding maps on the synchronization manifold. We observe that though the individual maps have simple and smooth functions as their stationary densities, they become multifractal as soon as two of them are coupled nonlinearly even with a small coupling. For some maps, the multifractal spectrum seems to be robust with the coupling or map parameters and for some other maps, there is a substantial variation. The origin of the multifractal spectrum here is intriguing as it does not seem to conform to the existing theory of multifractal functions.",1708.03125v1 2018-03-30,Effective universality in quantum gravity,"We investigate the asymptotic safety scenario for a scalar-gravity system. This system contains two avatars of the dynamical Newton coupling, a gravitational self-coupling and a scalar-graviton coupling. We uncover an effective universality for the dynamical Newton coupling on the quantum level: its momentum-dependent avatars are in remarkable quantitative agreement in the scaling regime of the UV fixed point. For the background Newton coupling, this effective universality is not present, but qualitative agreement remains.",1804.00012v2 2018-04-11,Dimensionally mixed coupled collective modes,"We develop the diagrammatic formulation of the many-body theory for the coupled collective modes in interacting electron systems of different dimensions. The formalism is then applied in detail to a two-dimensional system coupled to a three-dimensional electron gas. We find two dimensionally-mixed plasmon modes which in the long wavelength limit are respectively 3D-like and acoustic in nature, but are strongly coupled at larger wave vectors. The same formalism can be applied to any dimensional combinations, and we also present the results for 1D-2D and 1D-3D coupled systems.",1804.03835v1 2018-04-23,Low energy constituent quark and pion effective couplings to external electromagnetic field and a weak magnetic field,"In this work, a compilation of effective electromagnetic field couplings to pions and constituent quarks and their effective interactions derived previously, including corrections to the NJL model, is presented. The particular case of a weak external magnetic field along the $\hat{z}$ direction is considered shortly and effective coupling constants are redefined to incorporate the weak-$B_0$ dependence. They correspond to corrections to well known pion-constituent quark couplings and to the NJL and vector NJL effective couplings that break isospin and chiral symmetries.",1804.08673v2 2018-11-28,Gauge theories on spheres with 16 supercharges and non-constant couplings,"We construct a class of theories with 16 supersymmetries on spheres of dimension nine and less. The gauge coupling and mass terms for the scalar fields depend on the polar angle away from the north pole. Assuming finite coupling on the north pole, this leads to zero coupling at the south pole for $d>4$ and infinite coupling at the south pole for $d<4$. The underlying supersymmetry algebra of these theories is shown to be isomorphic to the Poincar\'e superalgebra in $d$-dimensions. We also give a localization procedure which leads to nontrivial results for $d=2$.",1811.11652v1 2013-08-08,Measuring extended Higgs sectors as a consistent free couplings model,"Extended Higgs sectors appear in many models for physics beyond the Standard Model. Current Higgs measurements at the LHC are starting to significantly constrain them. We study their Higgs coupling patterns at tree level as well as including quantum corrections. Our benchmarks include a dark singlet-doublet extension and several two-doublet setups. Using SFitter we translate the current Higgs coupling measurements for one light Higgs state into their respective parameter spaces. Finally, we show how two-Higgs-doublet models can serve as a consistent ultraviolet completion of an assumed single Standard-Model-like Higgs boson with free couplings.",1308.1979v1 2013-08-09,Optomechanics with Cavity Polaritons: Dissipative Coupling and Unconventional Bistability,"We study a hybrid system formed from an optomechanical resonator and a cavity mode strongly coupled to an excitonic transition inside a quantum well. We show that due to the mixing of cavity photon and exciton states, the emergent quasiparticles - polaritons - possess coupling to the mechanical mode of both dispersive and dissipative nature. We calculate the occupancies of polariton modes and reveal bistable behavior, which deviates from conventional Kerr nonlinearity or dispersive coupling cases due to the dissipative coupling. The described system serves as a good candidate for future polaritonic devices and solid state quantum information processing.",1308.2131v1 2018-05-23,Efficient side-coupling to photonic crystal nanobeam cavities via state-space overlap,"We present design guidelines for realizing side-coupled photonic crystal nanobeam (PCN) cavities with efficient coupling to low order resonances through adjusting the overlap of the PCN cavity mode and a feeding bus waveguide in both physical and k-space. We show that optimal side-coupled configurations function at a non-zero k-vector offset between the bus waveguide and PCN cavity modes. The straightforward design of side-coupled PCNs with high contrast resonances opens the door to their practical implementation in multiplexed, on-chip photonic devices.",1805.09438v2 2008-07-08,Domain Wall and Periodic Solutions of Coupled phi6 and Coupled phi6-phi4 Models,"We obtain several higher order periodic solutions of a Coupled phi6 model in terms of Lame polynomials of order one and two. These solutions are unusual in the sense that while they are the solutions of the coupled problem, they are not the solutions of the uncoupled problem. We also obtain exact solutions of coupled phi6-phi4 models, both when the phi4 potential corresponds to a first order (asymmetric double well) or a second order (symmetric double well) transition.",0807.1172v1 2008-07-12,Noether symmetry for non-minimally coupled fermion fields,"A cosmological model where a fermion field is non-minimally coupled with the gravitational field is studied. By applying Noether symmetry the possible functions for the potential density of the fermion field and for the coupling are determined. Cosmological solutions are found showing that the non-minimally coupled fermion field behaves as an inflaton describing an accelerated inflationary scenario, whereas the minimally coupled fermion field describes a decelerated period being identified as dark matter.",0807.1965v2 2008-07-15,Dynamics of dissipative coupled spins: decoherence and relaxation,"We study the reduced dynamics of interacting spins, each coupled to its own bath of bosons. We derive the solution in analytic form in the white-noise limit and analyze the rich behaviors in diverse limits ranging from weak coupling and/or low temperature to strong coupling and/or high temperature. We also view the one spin as being coupled to a spin-boson environment and consider the regimes in which it is effectively nonlinear, and in which it can be regarded as a resonant bosonic environment.",0807.2342v1 2011-11-16,Magnetic Susceptibility in Strongly Coupled Systems,"We study the magnetic susceptibility at large 't Hooft coupling by computing the correlation function of the magnetizations in the strongly coupled Maxwell theory in large-N limit with finite temperature and chemical potential, within the framework of the AdS/CFT correspondence. We show that in strong coupling limit the magnetic susceptibility is independent to the temperature and be universal, measured in the unit of magnetic permeability of the bulk space. A comparison with the weak coupling system, the Pauli paramagnetic susceptibility, is also discussed.",1111.3992v2 2011-12-30,Diffusion in infinite and semi-infinite lattices with long-range coupling,"We prove that for a one-dimensional infinite lattice, with long-range coupling among sites, the diffusion of an initial delta-like pulse in the bulk, is ballistic at all times. We obtain a closed-form expression for the mean square displacement (MSD) as a function of time, and show some cases including finite range coupling, exponentially decreasing coupling and power-law decreasing coupling. For the case of an initial excitation at the edge of the lattice, we find an approximate expression for the MSD that predicts ballistic behavior at long times, in agreement with numerical results.",1201.0133v1 2012-01-30,Cavity Quantum Electrodynamics with a Single Quantum Dot Coupled to a Photonic Molecule,"We demonstrate the effects of cavity quantum electrodynamics for a quantum dot coupled to a photonic molecule, consisting of a pair of coupled photonic crystal cavities. We show anti-crossing between the quantum dot and the two super-modes of the photonic molecule, signifying achievement of the strong coupling regime. From the anti-crossing data, we estimate the contributions of both mode-coupling and intrinsic detuning to the total detuning between the super-modes. Finally, we also show signatures of off-resonant cavity-cavity interaction in the photonic molecule.",1201.6244v1 2013-09-18,Effects of Nonlinear Coupling on Spatiotemporal Regularity,"In this work we investigate the spatiotemporal behaviour of lattices of coupled chaotic logistic maps, where the coupling between sites has a nonlinear form. We show that the stable range of the spatiotemporal fixed point state is significantly enhanced for increasingly nonlinear coupling. We demonstrate this through numerical simulations and linear stability analysis of the synchronized fixed point. Lastly, we show that these results also hold in coupled map lattices where the nodal dynamics is given by the Gauss Map, Sine Circle Map and the Tent Map.",1309.4555v1 2013-09-27,Solutions for Functional Fully Coupled Forward-Backward Stochastic Differential Equations,"In this paper, we study a functional fully coupled forward-backward stochastic differential equations (FBSDEs). Under a new type of integral Lipschitz and monotonicity conditions, the existence and uniqueness of solutions for functional fully coupled FBSDEs is proved. We also investigate the relationship between the solution of functional fully coupled FBSDE and the classical solution of the path-dependent partial differential equation (P-PDE). When the solution of the P-PDE has some smooth and regular properties, we solve the related functional fully coupled FBSDE and prove the P-PDE has a unique solution.",1309.7203v1 2013-09-29,The Statics Dielectric Function and Interaction Potential In Strong Coupling With AdS/CFT,"In this paper, we studied the static dielectric function and interaction potential in strong coupling limit with AdS/CFT correspondence. The dielectric function is depressed compared with that in weak coupling. The interaction potential then presents a weaker screening characteristics in strong coupling, which indicates a smaller Debye mass compared with weak coupling.",1309.7523v1 2014-06-07,Anisotropy in Inflation with Non-minimal Coupling,"We study a new anisotropic inflation model, with an inflaton field nonminimally coupled with the gravity and a vector field. We find that the anisotropic attractor solution exists not only in the weak curvature coupling limit, but more interestingly in the strong curvature coupling limit as well. We show that in the strong curvature coupling limit, the contribution from the anisotropy is greatly suppressed.",1406.1874v2 2014-06-24,Atomistic calculation of the thickness and temperature dependence of exchange coupling through a dilute magnetic oxide,"The exchange coupling of two magnetic layers via a diffuse oxide interlayer is studied with an atomistic spin model. We investigate the effect of magnetic concentration and oxide layer thickness on the effective exchange coupling strength and find an exponential dependence of the coupling strength on the oxide thickness without the need for magnetic pinholes. Furthermore we show that exchange coupling has a strong temperature dependence which is significant for the reversal dynamics during heat assisted magnetic recording.",1406.6214v1 2014-06-24,Positive solutions to some systems of coupled nonlinear Schrödinger equations,"We study the existence of nontrivial bound state solutions to the following system of coupled nonlinear time-independent Schr\""odinger equations $$ - \Delta u_j+ \lambda_j u_j =\mu_j u_j^3+ \sum_{k=1;k\neq j}^N\beta_{jk} u_ju_k^2,\quad u_j\in W^{1,2}(\mathbb{R}^n);\: j=1,\ldots,N $$ where $n=1,\,2,\, 3; \,\lambda_j,\, \mu_j>0$ for $j=1,\ldots,N$, the coupling parameters $\beta_{jk}=\beta_{kj}\in \mathbb{R}$ for $j,k=1,\ldots,N$, $j\neq k$. Precisely, we prove the existence of nonnegative bound state solutions for suitable conditions on the coupling factors. Additionally, with more restrictive conditions on the coupled parameters, we show that the bound states founded are positive.",1406.6237v3 2016-08-22,Coupled dynamics for superfluid $^4$He in the channel,"We study the coupled dynamics of normal and superfluid components of the superfluid $^4$He in the channel considering the counterflow turbulence with laminar normal component. In particular, we calculated profiles of the normal velocity, the mutual friction, the vortex line density and other flow properties and compared them to the case when the dynamic of the normal component is ""frozen"". We have found that the coupling between the normal and superfluid components leads to flattening of the normal velocity profile, increasingly more pronounced with temperature, as the mutual friction, and therefore coupling, becomes stronger. The commonly measured flow properties also change when the coupling between two components is taken into account.",1608.06162v1 2017-06-14,Completion of the Ablowitz-Kaup-Newell-Segur integrable coupling,"Integrable couplings are associated with non-semisimple Lie algebras. In this paper, we propose a new method to generate new integrable systems through making perturbation in matrix spectral problems for integrable couplings, which is called the `completion process of integrable couplings'. As an example, the idea of construction is applied to the Ablowitz-Kaup-Newell-Segur integrable coupling. Each equation in the resulting hierarchy has a bi-Hamiltonian structure furnished by the component-trace identity.",1706.04308v1 2018-09-14,Strong Coupling Theory of Superconductivity,"The electronic properties of correlated metals with a strong electron-phonon coupling may be understood in terms of a combination of Landau's Fermi-liquid theory and the strong-coupling theory of Migdal and Eliashberg. In these lecture notes we discuss the microscopic foundations of this phenomenological Fermi-liquid model of correlated, strong-coupling metals. We formulate the basic equations of the model, which are quasiclassical transport equations that describe both equilibrium and non-equilibrium phenomena for the normal and superconducting states of a metal. Our emphasis is on superconductors close to equilibrium, for which we derive the general linear response theory. As an application we calculate the dynamical conductivity of strong-coupling superconductors.",1809.05264v1 2018-09-24,Strong coupling of ionising transitions,"We demonstrate that a ionising transition can be strongly coupled to a photonic resonance. The strong coupling manifests itself with the appearance of a narrow optically active resonance below the ionisation threshold. Such a resonance is due to electrons transitioning into a novel bound state created by the collective coupling of the electron gas with the vacuum field of the photonic resonator. Applying our theory to the case of bound-to-continuum transitions in microcavity-embedded doped quantum wells, we show how those strong-coupling features can be exploited as a novel knob to tune both optical and electronic properties of semiconductor heterostructures.",1809.08876v1 2012-05-22,Effective couplings approach to neutralino dark matter relic density,"In this work, we analyze the electroweak loop corrections to the Neutralino dark matter relic density in the framework of effective coupling. In the first part, we comment on the generic features of the corrections and quantitative changes to the predicted relic density. We analyze the correlation between the characteristics of effective couplings to the nature of neutralino. Effective couplings, however, absorb only the most dominant one loop corrections and are not an exact calculation. In the second part, we assess the validity of effective couplings by comparing them to the full one loop calculations in various regions of parameter space.",1205.5061v1 2017-05-01,Comparison of transport coefficients for weakly coupled multi-component plasmas obtained with different formalisms,"LANL Memorandum of potentially broad interest. A direct comparison is performed between transport coefficients for weakly coupled plasmas obtained with different formalisms to demonstrate that these formalisms give identical predictions. This is what one would expect since for weakly coupled plasmas all the formalisms rely on the same physical assumptions and mathematical approximations.",1705.00712v1 2017-05-16,The infinitely many zeros of stochastic coupled oscillators driven by random forces,"In this work, previous results concerning the infinitely many zeros of single stochastic oscillators driven by random forces are extended to the general class of coupled stochastic oscillators. We focus on three main subjects: 1) the analysis of this oscillatory behavior for the case of coupled harmonic oscillators; 2) the identification of some classes of coupled nonlinear oscillators showing this oscillatory dynamics and 3) the capability of some numerical integrators - thought as discrete dynamical systems - for reproducing the infinitely many zeros of coupled harmonic oscillators driven by random forces.",1705.06598v1 2017-05-29,On stationary fractional Mean Field Games,"We provide an existence result for stationary fractional mean field game systems, with fractional exponent greater than 1/2. In the case in which the coupling is a nonlocal regularizing potential, we obtain existence of solutions under general assumptions on the Hamiltonian. In the case of local coupling, we restrict to the subcritical regime, that is the case in which the diffusion part of the operator dominates the Hamiltonian term. We consider both the case of local bounded coupling and of local unbounded coupling with power-type growth. In this second regime, we impose some conditions on the growth of the coupling and on the growth of the Hamiltonian with respect to the gradient term.",1705.10123v1 2017-09-18,Interfacial thermal transport with strong system-bath coupling: A phonon delocalization effect,"We study the effect of system-bath coupling strength on quantum thermal transport through the interface of two weakly coupled anharmonic molecular chains using quantum self-consistent phonon approach. The heat current shows a resonant to bi-resonant transition due to the variations in the interfacial coupling and temperature, which is attributed to the delocalization of phonon modes. Delocalization occurs only in the strong system-bath coupling regime and we utilize it to model a thermal rectifier whose ratio can be non-monotonically tuned not only with the intrinsic system parameters but also with the external temperature.",1709.06029v1 2018-03-28,Quantum Coupling and Strassen Theorem,"We introduce a quantum generalisation of the notion of coupling in probability theory. Several interesting examples and basic properties of quantum couplings are presented. In particular, we prove a quantum extension of Strassen theorem for probabilistic couplings, a fundamental theorem in probability theory that can be used to bound the probability of an event in a distribution by the probability of an event in another distribution coupled with the first.",1803.10393v1 2018-07-13,Eliashberg Theory in the Weak Coupling Limit,"Eliashberg theory provides a theoretical framework for understanding the phenomenon of superconductivity when pairing between two electrons is mediated by phonons, and retardation effects are fully accounted for. BCS theory is often viewed as the weak coupling limit of Eliashberg theory, in spite of a handful of papers that have pointed out that this is not so. Here we present very accurate numerical solutions in the weak coupling limit to complement the existing analytical results, and demonstrate more convincingly the validity of this limit by extending the analytical results to first order in the coupling constant.",1807.04907v2 2018-12-21,Two-level System coupled to Phonons: Full Analytical Solution,"We propose an analytical procedure to fully solve a two-level system coupled to phonons. Instead of using the common formulation in terms of linear and quadratic system-phonon couplings, we introduce different phonons depending on the system electronic level. We use this approach to recover known results for the linear-coupling limit in a simple way. More importantly, we derive results for the quadratic coupling induced by a phonon frequency change, a problem considered up to now as not analytically solvable.",1812.09043v2 2019-01-14,Quantum simulation scheme of two-dimensional xy-model Hamiltonian with controllable coupling,"We study a scheme of quantum simulator for two-dimensional xy-model Hamiltonian. Previously the quantum simulator for a coupled cavity array spin model has been explored, but the coupling strength is fixed by the system parameters. In the present scheme several cavity resonators can be coupled with each other simultaneously via an ancilla qubit. In the two-dimensional Kagome lattice of the resonators the hopping of resonator photonic modes gives rise to the tight-binding Hamiltonian which in turn can be transformed to the quantum xy-model Hamiltonian. We employ the transmon as an ancilla qubit to achieve in situ controllable xy-coupling strength.",1901.04350v1 2019-01-29,On coupled constant scalar curvature Kähler metrics,"We provide a moment map interpretation for the coupled K\""ahler-Einstein equations introduced by Hultgren and Witt Nystr\""om, and in the process introduce a more general system of equations, which we call coupled cscK equations. A differentio-geometric formulation of the corresponding Futaki invariant is obtained and a notion of K-polystability is defined for this new system. Finally, motivated by a result of Sz\'ekelyhidi, we prove that if there is a solution to our equations, then small K-polystable perturbations of the underlying complex structure and polarizations also admit coupled cscK metrics.",1901.10454v2 2019-02-07,Stability of the vacuum as constraint on $U$(1) extensions of the standard model,"In the standard model the running quartic coupling becomes negative during its renormalization group flow, which destabilizes the vacuum. We consider U(1) extensions of the standard model, with an extra complex scalar field and a Majorana-type neutrino Yukawa coupling. These additional couplings affect the renormalization group flow of the quartic couplings. We compute the beta-functions of the extended model at one-loop order in perturbation theory and study how the parameter space of the new scalar couplings can be constrained by the requirement of stable vacuum and perturbativity up to the Planck scale.",1902.02791v1 2019-02-20,Nanostructuring of LNOI for efficient edge coupling,"We present the design, fabrication and characterization of LNOI fiber-to-chip inverse tapers for efficient edge coupling. The etching characteristics of various LNOI crystal cuts are investigated for the realization of butt-coupling devices. We experimentally demonstrate that the crystal cut limits the performance of mode matching tapers. We report a butt-coupling loss of 2.5 dB/facet and 6 dB/facet by implementing 200 nm tip mode matching tapers in $+Z$-cut LNOI and $X$-cut MgO:LNOI waveguides with low propagation loss. We anticipate that these results will provide insight into the nanostructuring of LNOI and into the further development of efficient butt-coupling in this platform.",1902.07394v1 2019-02-26,Effects of orbital angular momentum on few-cycle pulse shape: Coupling between the temporal and angular momentum degrees of freedom,"We describe the coupling between orbital angular momentum (OAM) and temporal degrees of freedom in pulsed Laguerre-Gauss beams. The effects of this coupling are to increase significantly the duration of few-cycle pulses when the OAM carried by the pulse is large, and to enhance spatiotemporal couplings. Contrary to other detrimental but retrievable effects such as spatial, group velocity and topological charge dispersions in these pulses, OAM-temporal coupling effects are unavoidable, and have therefore an impact in applications such as OAM-based optical communications, or in the generation of vortex-carrying attosecond pulses.",1902.09974v2 2019-03-07,Sliding Luttinger liquid with alternating interwire couplings,"We study a phase diagram for the sliding Luttinger liquid (SLL) of coupled one-dimensional quantum wires packed in a two-dimensional array in the absence of a magnetic field. We analyze whether nearest-neighbor inter-wire interactions, stabilize the SLL phase. We construct an analogue of a Su-Schriefer-Heeger (SSH) model (allowing alternating couplings between wires). Calculating the scaling dimensions of the two most relevant perturbations, charge-density wave, and superconducting inter-wire couplings, but excluding the inter-wire single-particle hybridization, we find a finite stability region for the SLL. It emerges due to the inter-wire forward scattering interaction, and remains stable up to a significant asymmetry between alternating couplings.",1903.02920v1 2019-08-21,Random Mode Coupling Assists Kerr Beam Self-Cleaning in a Graded-Index Multimode Optical Fiber,"In this paper, we numerically investigate the process of beam self-cleaning in a graded-index multimode optical fiber, by using the coupled-mode model. We introduce various models of random linear coupling between spatial modes, including coupling between all modes, or only between degenerate ones, and investigate the effects of random mode coupling on the beam self-cleaning process. The results of numerical investigations are in complete agreement with our experimental data.",1908.07745v1 2019-11-17,Exponential Stability of a Class of Infinite Dimensional Coupled Systems,"This paper is concerned with exponential stability of a class of infinite dimensional coupled systems. It is proved that under some admissibility conditions, the considered infinite dimensional coupled system is governed by a $C_0$-semigroup. Furthermore, if both the free subsystems are governed by exponentially stable $C_0$-semigroups, then so is the coupled system. The results are applied to simplify the proof of semigroup generation and exponential stability for several coupled systems emerged in control theory literatures.",1911.07238v2 2016-03-14,Segmented strings coupled to a B-field,"In this paper we study segmented strings in AdS$_3$ coupled to a background two-form whose field strength is proportional to the volume form. By changing the coupling, the theory interpolates between the Nambu-Goto string and the $SL(2)$ Wess-Zumino-Witten model. In terms of the kink momentum vectors, the action is independent of the coupling and the classical theory reduces to a single discrete-time Toda-type theory. The WZW model is a singular point in coupling space where the map into Toda variables degenerates.",1603.04504v1 2016-10-13,Non-equilibrium quantum phase transition via entanglement decoherence dynamics,"We investigate the decoherence dynamics of continuous variable entanglement as the system-environment coupling strength varies from the weak-coupling to the strong-coupling regimes. Due to the existence of localized modes in the strong-coupling regime, the system cannot approach equilibrium with its environment, which induces a nonequilibrium quantum phase transition. We analytically solve the entanglement decoherence dynamics for an arbitrary spectral density. The nonequilibrium quantum phase transition is demonstrated as the system-environment coupling strength varies for all the Ohmic-type spectral densities. The 3-D entanglement quantum phase diagram is obtained.",1610.03919v1 2016-10-31,Gradient flow running coupling in SU(2) Nf=6 flavors,"We present preliminary results of the running of the coupling in SU(2) gauge theory with 6 massless fundamental representation fermion flavors. We measure the coupling using the gradient flow method with Schr\""odinger functional boundary conditions. The results are consistent with the perturbation theory in the weak coupling and we see an indication of an infrared fixed point at strong coupling.",1610.09989v1 2016-12-01,On the dynamics of polarons in the strong-coupling limit,"The polaron model of H. Fr\""ohlich describes an electron coupled to the quantized longitudinal optical modes of a polar crystal. In the strong-coupling limit one expects that the phonon modes may be treated classically, which leads to a coupled Schr\""odinger-Poisson system with memory. For the effective dynamics of the electron this amounts to a nonlinear and non-local Schr\""odinger equation. We use the Dirac-Frenkel variational principle to derive the Schr\""odinger-Poisson system from the Fr\""ohlich model and we present new results on the accuracy of their solutions for describing the motion of Fr\""ohlich polarons in the strong-coupling limit. Our main result extends to $N$-polaron systems.",1612.00395v1 2016-12-19,Sticky couplings of multidimensional diffusions with different drifts,"We present a novel approach of coupling two multidimensional and non-degenerate It\^o processes $(X_t)$ and $(Y_t)$ which follow dynamics with different drifts. Our coupling is sticky in the sense that there is a stochastic process $(r_t)$, which solves a one-dimensional stochastic differential equation with a sticky boundary behavior at zero, such that almost surely $|X_t-Y_t|\leq r_t$ for all $t\geq 0$. The coupling is constructed as a weak limit of Markovian couplings. We provide explicit, non-asymptotic and long-time stable bounds for the probability of the event $\{X_t=Y_t\}$.",1612.06125v1 2017-11-04,Strong coupling constant extraction from high-multiplicity Z+jets observables,"We present a strong coupling constant extraction at Next-to-Leading Order QCD accuracy using ATLAS Z+2,3,4 jets data. This is the first extraction using processes with a dependency to high powers of the coupling constant. We obtain values of the strong coupling constant at the $Z$ mass compatible with the world average and with uncertainties commensurate with other NLO extractions at hadron colliders. Our most conservative result for the strong coupling constant is $\alpha_S=0.1178 ^{+0.0051}_{- 0.0043}$.",1711.01408v2 2019-05-14,Calabi type functionals for coupled Kähler-Einstein metrics,"We introduce the coupled Ricci-Calabi functional and the coupled H-functional which measure how far from a coupled K\""ahler-Einstein metric in the sense of Hultgren-Witt Nystr\""om. We first give corresponding moment weight type inequalities which estimate each functional in terms of algebraic invariants. Secondly, we give corresponding Hessian formulas for these functionals at each critical point, which have an application to a Matsushima type obstruction theorem for the existence of a coupled K\""ahler-Einstein metric.",1905.05326v4 2019-05-28,Electroweak Baryogenesis from Temperature-Varying Couplings,"The fundamental couplings of the Standard Model are known to vary as a function of energy scale through the Renormalisation Group (RG), and have been measured at the electroweak scale at colliders. However, the variation of the couplings as a function of temperature need not be the same, raising the possibility that couplings in the early universe were not at the values predicted by RG evolution. We study how such temperature-variance of fundamental couplings can aid the production of a baryon asymmetry in the universe through electroweak baryogenesis. We do so in the context of the Standard Model augmented by higher-dimensional operators up to dimension 6.",1905.11994v1 2021-02-01,Constraining CP violating operators in charged and neutral triple gauge couplings,"We constrain $C\!P$-violating charged and neutral anomalous triple gauge couplings using LHC measurements and projections of diboson and VBF $Vjj$ production, both with subsequent leptonic decays. For triple gauge couplings involving $W$ bosons we analyse asymmetries and interpret our results in the SMEFT at dimension-six. For neutral triple gauge couplings, which are dominantly constrained by high transverse-momentum bins, we present the resulting bounds in terms of a general anomalous couplings framework.",2102.01115v2 2013-06-04,Estimating coupling directions in the cardio-respiratory system using recurrence properties,"The asymmetry of coupling between complex systems can be studied by conditional probabilities of recurrence, which can be estimated by joint recurrence plots. This approach is applied for the first time on experimental data: time series of the human cardio-respiratory system in order to investigate the couplings between heart rate, mean arterial blood pressure, and respiration. We find that the respiratory system couples towards the heart rate and the heart rate towards the mean arterial blood pressure. However, our analysis could not detect a clear coupling direction between the mean arterial blood pressure and respiration.",1306.0697v1 2013-06-27,Meron Ground State of Rashba Spin-Orbit-Coupled Dipolar Bosons,"We study the effects of dipolar interactions on a Bose-Einstein condensate with synthetically generated Rashba spin-orbit coupling. The dipolar interaction we consider includes terms that couple spin and orbital angular momentum in a way perfectly congruent with the single-particle Rashba coupling. We show that this internal spin-orbit coupling plays a crucial role in the rich ground-state phase diagram of the trapped condensate. In particular, we predict the emergence of a thermodynamically stable ground state with a meron spin configuration.",1306.6610v2 2016-11-10,Couplings of NN(nπ) n \geq 1,"Determinations of the couplings of $N N (n \pi) (n \geq 1)$ are reported. The study is based on both a quark model of nucleon and a chiral field theory of mesons. The coupling of $N N \pi$ is predicted and is in agreement with current value. It shows that the coupling $ N N 2 \pi $ is resulted in the nature that pion is a Goldstone boson. The couplings of $N N (n \pi) (n \geq 2)$ are predicted by this approach.",1611.03370v1 2016-11-11,Chimera states and the interplay between initial conditions and non-local coupling,"Chimera states are complex spatio-temporal patterns that consist of coexisting domains of coherent and incoherent dynamics. We study chimera states in a network of non-locally coupled Stuart-Landau oscillators. We investigate the impact of initial conditions in combination with non-local coupling. Based on an analytical argument, we show how the coupling phase and the coupling strength are linked to the occurrence of chimera states, flipped profiles of the mean phase velocity, and the transition from a phase- to an amplitude-mediated chimera state.",1611.03771v1 2016-11-23,Electrically Pumped Single Transverse-Mode Coupled Waveguide Lasers by Parity-time (PT) Symmetry,"We demonstrate single transverse-mode operation of broad-area coupled waveguide lasers enabled by parity-time (PT) symmetry. The PT symmetric laser operates on coupled waveguide cavities with electrically tuned gain and loss. Such counterintuitive waveguide design enables PT symmetric breaking, causing unique mode selection and ultimately enabling single mode operation. By electrically tuning the loss in the loss region of the coupled waveguide cavity, several different PT-symmetric regimes are analyzed theoretically, and the corresponding PT symmetric phase transition is demonstrated experimentally in the coupled waveguide laser.",1611.07888v3 2017-04-06,Origin of Temperature Gradient in Nonequilibrium Steady States in Weakly Coupled Quantum Spin Systems,"We study nonequilibrium steady states (NESSs) in quantum spin-1/2 chains in contact with two heat baths at different temperatures. We consider the weak-coupling limit both for spin-spin coupling in the system and for system-bath coupling. This setting allows us to treat NESSs with a nonzero temperature gradient analytically. We develop a perturbation theory for this weak-coupling situation and show a simple condition for the existence of nonzero temperature gradient. This condition is independent of the integrability of the system.",1704.01731v1 2017-12-31,Stabilization of the weakly coupled wave-plate system with one internal damping,"This paper is addressed to a stabilization problem of a system coupled by a wave and a Euler-Bernoulli plate equation. Only one equation is supposed to be damped. Under some assumption about the damping and the coupling terms, it is shown that sufficiently smooth solutions of the system decay logarithmically at infinity without any geometric conditions on the effective damping domain. The proofs of these decay results rely on the interpolation inequalities for the coupled elliptic-parabolic systems and make use of the estimate of the resolvent operator for the coupled system. The main tools to derive the desired interpolation inequalities are global Carleman estimates.",1801.00232v1 2017-12-21,Exploring cogging free magnetic gears,"The coupling of two rotating spherical magnets is investigated experimentally, with particular emphasis on those motions where the driven magnet follows the driving one with a uniform angular speed, which is a feature of the so called cogging free couplings. The experiment makes use of standard equipment and digital image processing. The theory for these couplings is based on fundamental dipole-dipole interactions with analytically accessible solutions. Technical applications of this kind of coupling are foreseeable particularly for small machines, an advantage which also comes handy for classroom demonstrations of this feature of the fundamental concept of dipole-dipole coupling.",1801.03416v2 2018-01-17,Phase-flip bifurcation and synchronous transition in unidirectionally coupled parametrically excited pendula,"Phase-flip bifurcation plays an important role in the transition to synchronization state in unidirectionally coupled parametrically excited pendula. In coupled identical system it is the cause of complete synchronization whereas in case of coupled non-identical system it causes desynchronization. In coupled identical systems negativity of conditional Lyapunov exponent is not always sufficient for complete synchronization. In complete synchronization state the largest conditional Lyapunov exponent and the second largest Lyapunov exponent are equal in magnitude and slope.",1801.05572v1 2018-08-20,CU-Net: Coupled U-Nets,"We design a new connectivity pattern for the U-Net architecture. Given several stacked U-Nets, we couple each U-Net pair through the connections of their semantic blocks, resulting in the coupled U-Nets (CU-Net). The coupling connections could make the information flow more efficiently across U-Nets. The feature reuse across U-Nets makes each U-Net very parameter efficient. We evaluate the coupled U-Nets on two benchmark datasets of human pose estimation. Both the accuracy and model parameter number are compared. The CU-Net obtains comparable accuracy as state-of-the-art methods. However, it only has at least 60% fewer parameters than other approaches.",1808.06521v1 2019-06-09,Coupled Bloch-Wave Analysis of Active PhC Waveguides and Cavities,"A coupled Bloch-wave approach is employed to analyze active photonic-crystal (PhC) waveguides and cavities. Gain couples the otherwise independent counter-propagating Bloch modes. This coupling is shown to limit the maximum attainable slow-light enhancement of gain itself and to strongly affect the mode selection in PhC lasers.",1906.03638v1 2019-07-12,Non-coupling from the past,"The method of 'coupling from the past' permits exact sampling from the invariant distribution of a Markov chain on a finite state space. The coupling is successful whenever the stochastic dynamics are such that there is coalescence of all trajectories. The issue of the coalescence or non-coalescence of trajectories of a finite state space Markov chain is investigated in this note. The notion of the 'coalescence number' $k(\mu)$ of a Markovian coupling $\mu$ is introduced, and results are presented concerning the set $K(P)$ of coalescence numbers of couplings corresponding to a given transition matrix $P$.",1907.05605v2 2020-01-09,Theoretical Prediction of Magnetic Exchange Coupling Constants from Broken-Symmetry Coupled Cluster Calculations,"Exchange coupling constants ($J$) are fundamental to the understanding of spin spectra of magnetic systems. Here we investigate the broken-symmetry (BS) approaches of Noodleman and Yamaguchi in conjunction with coupled cluster (CC) methods to obtain exchange couplings. $J$ values calculated from CC in this fashion converge smoothly towards the FCI result with increasing level of CC excitation. We compare this BS-CC scheme to the complementary EOM-CC approach on a selection of bridged molecular cases and give results from a few other methodologies for context.",2001.03226v1 2020-05-09,Synchronization of oscillators not sharing a common ground,"Networks of coupled LC oscillators that do not share a common ground node are studied. Both resistive coupling and inductive coupling are considered. For networks under resistive coupling, it is shown that the oscillator-coupler interconnection has to be bilayer if the oscillator voltages are to asymptotically synchronize. Also, for bilayer architecture (when both resistive and inductive couplers are present) a method is proposed to compute a complex-valued effective Laplacian matrix that represents the overall coupling. It is proved that the oscillators display synchronous behavior if and only if the effective Laplacian has a single eigenvalue on the imaginary axis.",2005.04403v2 2020-07-09,Splitting schemes for a Lagrange multiplier formulation of FSI with immersed thin-walled structure: stability and convergence analysis,"The numerical approximation of incompressible fluid-structure interaction problems with Lagrange multiplier is generally based on strongly coupled schemes. This delivers unconditional stability but at the expense of solving a computationally demanding coupled system at each time-step. For the case of the coupling with immersed thin-walled solids, we introduce a class of semi-implicit coupling schemes which avoids strongly coupling without compromising stability and accuracy. A priori energy and error estimates are derived. The theoretical results are illustrated through numerical experiments in an academic benchmark.",2007.04699v1 2021-03-10,Magnetic phases for two $t_{2g}$ holes with spin-orbit coupling and crystal field,"We investigate two holes in the the $t_{2g}$ levels of a square-lattice Mott insulator with strong spin-orbit coupling. Exact diagonalization of a spin-orbital model valid at strong onsite interactions, but arbitrary spin-orbit coupling and crystal field is complemented by an effective triplon model (valid for strong spin-orbit coupling) and by a semiclassical variant of the model. We provide the magnetic phase diagram depending on crystal field and spin-orbit coupling, which largely agrees for the semiclassical and quantum models, as well as excitation spectra characterizing the various phases.",2103.06033v1 2021-04-06,Husimi Functions for Coupled Optical Resonators,"Phase-space analysis has been widely used in the past for the study of optical resonant systems. While it is usually employed to analyze the far-field behaviour of resonant systems we focus here on its applicability to coupling problems. By looking at the phase-space description of both the resonant mode and the exciting source it is possible to understand the coupling mechanisms as well as to gain insights and approximate the coupling behaviour with reduced computational efforts. In this work we develop the framework for this idea and apply it to a system of an asymmetric dielectric resonator coupled to a waveguide.",2104.02368v1 2021-04-21,Universal coupled theory for metamaterial Bound states in the continuum,"In this paper, we present a novel universal coupled theory for metamaterial Bound states in the continuum (BIC) or quasi-Bound states in the continuum (quasi-BIC) which provides ultra-high Q resonance for metamaterial devices. Our theory analytically calculates the coupling of two bright modes with phase. Our method has much more accuracy for ultra-strong coupling comparing with the previous theory (the coupling of one bright mode and one dark mode). Therefore, our theory is much more suitable for BIC or quasi-BIC and we can accurately predict the transmission spectrum of metamaterial BIC or quasi-BIC for the first time.",2104.10641v1 2021-04-30,Dbar-approach to coupled nonlocal NLS equation and general nonlocal Reduction,"The coupled nonlocal NLS equation is studied by virtue of the $2\times2$ Dbar-problem. Two spectral transform matrices are introduced to define two associated Dbar-problems. The relations between the coupled nonlocal NLS potential and the solution of the Dbar-problem are constructed. The spatial transform method is extended to obtain the coupled nonlocal NLS equation and its conservation laws. The general nonlocal reduction of the coupled nonlocal NLS equation to the nonlocal NLS equation is discussed in detail. The explicit solutions are derived.",2104.14814v1 2021-05-03,Anisotropy-Exchange Resonance as a Mechanism for Entangled State Switching,"We explore the three-particle spin model of an $S_{1}=\frac{1}{2}$ particle (e.g. a stationary electron) interacting with two spin-coupled $S_{\text{2,3}}$ particles with exchange coupling and magnetic anisotropy. We find that in the case of $S_{2,3}=1$ particles, the coupled particle entanglement states can be prepared, controlled, and read by the $S_{1}$ particle. We also find that for particular resonance conditions of the magnetic anisotropy strength $D$ and exchange coupling strength $J$, the entanglement state switching behavior is maximized and is robust against a range of anisotropic application of the exchange coupling.",2105.01126v1 2021-05-23,Impact of non-Hermitian Mode interaction on Inter-cavity Light transfer,"Understanding inter-site mutual mode interaction in coupled physical systems is essential to comprehend large compound systems as this local interaction determines the successive multiple inter-site energy transfer efficiency. We demonstrate that only the non-Hermitian coupling can correctly account for the light transfer between two coupled optical cavities. We also reveal that the non-Hermitian coupling effect becomes much crucial as the system dimension gets smaller. Our results provide an important insight to deal with general coupled-devices in the quantum regime.",2105.10936v1 2021-06-30,The Performance Impact of Newton Iterations per Solver Call in Partitioned Fluid-Structure Interaction,"The cost of a partitioned fluid-structure interaction scheme is typically assessed by the number of coupling iterations required per time step, while ignoring the Newton loops within the nonlinear sub-solvers. In this work, we discuss why these single-field iterations deserve more attention when evaluating the coupling's efficiency and how to find the optimal number of Newton steps per coupling iteration.",2106.15930v1 2021-07-09,Theory of Vibrational Polariton Chemistry in the Collective Coupling Regime,"We theoretically demonstrate that chemical reaction rate constant can be significantly suppressed by coupling molecular vibrations with an optical cavity, exhibiting both the collective coupling effect and the cavity-frequency modification of the rate constant. When a reaction coordinate is strongly coupled to the solvent molecules, the reaction rate constant is reduced due to the dynamical caging effect. We demonstrate that collectively coupling the solvent to the cavity can further enhance this dynamical caging effect, leading to additional suppression of the chemical kinetics. This effect is further amplified when cavity loss is considered.",2107.04156v1 2021-08-03,Two electrons in harmonic confinement coupled to light in a cavity,"The energy and wave function of a harmonically confined two-electron system coupled to light is calculated by separating the wave functions of the relative and center of mass (CM) motions. The relative motion wave function has a known quasi-analytical solution. The light only couples to the CM variable and the coupled equation can be solved with diagonalization without approximations. The approach works for any coupling strength. Examples of wave functions of light-matter hybrid states are presented.",2108.01702v1 2021-08-13,Coupling the Higgs mode and ferromagnetic resonance in spin-split superconductors with Rashba spin-orbit coupling,"We consider the Higgs mode at nonzero momentum in superconductors and demonstrate that in the presence of Rashba spin-orbit coupling, it couples linearly with an external exchange field. The Higgs-spin coupling dramatically modifies the spin susceptibility near the superconducting critical temperature and consequently enhances the spin pumping effect in a ferromagnetic insulator/superconductor bilayer system. We show that this effect can be detected by measuring the magnon-induced voltage generated by the inverse spin Hall effect.",2108.06202v2 2021-10-05,Revisiting closed asymptotic couples,"Every discrete definable subset of a closed asymptotic couple with ordered scalar field $\boldsymbol k$ is shown to be contained in a finite-dimensional $\boldsymbol k$-linear subspace of that couple. It follows that the differential-valued field $\mathbb T$ of transseries induces more structure on its value group than what is definable in its asymptotic couple equipped with its scalar multiplication by real numbers, where this asymptotic couple is construed as a two-sorted structure with $\mathbb R$ as the underlying set for the second sort.",2110.02107v3 2021-11-12,Spin-orbit coupling matrix elements from the explicitly connected expressions of the response functions within the coupled-cluster theory,"In this work we present a coupled cluster based approach to the computation of the spin orbit coupling matrix elements. The working expressions are derived from the quadratic response function with the coupled cluster parametrization, using the auxiliary excitation operator S. Systematic approximations are proposed with the CCSD and CC3 levels of theory. The new method is tested by computing lifetimes of several electronic states of Ca, Sr and Ba atoms, with Gaussian and Slater basis sets. The results are compared with available theoretical and experimental data.",2111.06802v1 2021-12-19,Relaxation shortcuts through boundary coupling,"When a hot system cools down faster than an equivalent cold one, it exhibits the Mpemba Effect. This counterintuitive phenomenon was observed in several systems including water, magnetic alloys and polymers. In most experiments the system is coupled to the bath through its boundaries, but all theories so far assumed bulk coupling. Here we build a general framework for boundary coupling relaxation and show that the Mpemba effect persists in these cases. Surprisingly, it can survive even an arbitrarily weak couplings. An example is given in the Ising antiferromagnetic chain.",2112.10187v1 2021-12-27,Scaling limit of stationary coupled Sasamoto-Spohn models,"We introduce a family of stationary coupled Sasamoto-Spohn models and show that, in the weakly asymmetric regime, they converge to the energy solution of coupled Burgers equations. Moreover, we show that any system of coupled Burgers equations satisfying the so-called trilinear condition ensuring stationarity can be obtained as the scaling limit of a suitable system of coupled Sasamoto-Spohn models. The core of our proof, which avoids the use of spectral gap estimates, consists in a second order Boltzmann-Gibbs principle for the discrete model.",2112.13810v1 2022-02-27,Configuration Control for Physical Coupling of Heterogeneous Robot Swarms,"In this paper, we present a heterogeneous robot swarm system that can physically couple with each other to form functional structures and dynamically decouple to perform individual tasks. The connection between robots can be formed with a passive coupling mechanism, ensuring minimum energy consumption during coupling and decoupling behavior. The heterogeneity of the system enables the robots to perform structural enhancement configurations based on specific environmental requirements. We propose a connection-pair oriented configuration control algorithm to form different assemblies. We show experiments of up to nine robots performing the coupling, gap-crossing, and decoupling behaviors.",2202.13461v2 2022-03-03,Stability results of locally coupled wave equations with local Kelvin-Voigt damping: Cases when the supports of damping and coupling coefficients are disjoint,"In this paper, we study the direct/indirect stability of locally coupled wave equations with local Kelvin-Voigt dampings/damping and by assuming that the supports of the dampings and the coupling coefficients are disjoint. First, we prove the well-posedness, strong stability, and polynomial stability for some one dimensional coupled systems. Moreover, under some geometric control condition, we prove the well-posedness and strong stability in the multi-dimensional case.",2203.01632v1 2022-04-08,A no-go theorem for scalar fields with couplings from Ginzburg-Landau models,"Recently Hod proved a no-go theorem that static scalar fields cannot form spherically symmetric boson stars in the asymptotically flat background. On the other side, scalar fields can be coupled to the gradient according to next-to-leading order Ginzburg-Landau models. In the present work, we extend Hod's discussions by considering couplings between static scalar fields and the field gradient. For a non-negative coupling parameter, we show that there is no asymptotically flat spherically symmetric boson stars made of coupled static scalar fields.",2204.03833v1 2022-04-14,A note on the effects of magnetic field on holographic fermions with dipole-like coupling,"In this note, we study the effects of non-zero magnetic field on the fermion spectral function coupled with a non-minimal coupling in the background of a dyonic $AdS_4$ black hole. The system can be reduced to a non magnetic one with the momentum being quantized into Landau levels $n$. By tuning the coupling parameter, we study its effect on the Fermi level and the quasiparticle width. We found an interesting scaling relation between the decay width and the coupling parameter, with a universal scaling exponent which is independent of the levels $n$.",2204.06756v1 2022-06-10,Quantum heat engine based on a spin-orbit and Zeeman-coupled Bose-Einstein condensate,"We explore the potential of a spin-orbit coupled Bose-Einstein condensate for thermodynamic cycles. For this purpose we propose a quantum heat engine based on a condensate with spin-orbit and Zeeman coupling as a working medium. The cooling and heating are simulated by contacts of the condensate with an external magnetized media and demagnetized media. We examine the condensate ground state energy and its dependence on the strength of the synthetic spin-orbit and Zeeman couplings and interatomic interaction. Then we study the efficiency of the proposed engine. The cycle has a critical value of spin-orbit coupling related to the engine maximum efficiency.",2206.05041v1 2022-08-12,Internal energy exchanges and chaotic dynamics in an intrinsically coupled system,"Intrinsically coupled nonlinear systems present different oscillating components that exchange energy among themselves. A paradigmatic example is the spring pendulum, which displays spring, pendulum, and coupled oscillations. We analyze the energy exchanges among the oscillations, and obtain that it is enhanced for chaotic orbits. Moreover, the highest rates of energy exchange for the coupling occur along the homoclinic tangle of the primary hyperbolic point embedded in a chaotic sea. The results show a clear relation between internal energy exchanges and the dynamics of a coupled system.",2208.06390v1 2022-08-26,Schwinger-Dyson equations and mass generation for an axion theory with a PT symmetric Yukawa fermion interaction,"A nonperturbative Schwinger-Dyson analysis of mass generation is presented for a non-Hermitian PT-symmetric field theory in four dimensions of an axion coupled to a Dirac fermion.The model is motivated by phenomenological considerations.The axion has a quartic self-coupling $\lambda$ and a Yukawa coupling $g$ to the fermion. The Schwinger-Dyson equations are derived for the model with generic couplings. In the non-Hermitian case there is an additional nonperturbative contribution to the scalar mass. In a simplified rainbow analysis the solutions for the SD equations, are given for different regimes of the couplings $g$ and $\lambda$.",2208.12436v1 2022-09-08,Temporal coupled-mode theory for thermal emission from multiple arbitrarily coupled resonators,"Controlling the spectral response of thermal emitters has become increasingly important for a range of energy and sensing applications. Conventional approaches to achieving arbitrary spectrum selectivity in photonic systems have entailed combining multiple resonantly emissive elements together to achieve a range of spectral profiles through numerical optimization, with a universal theoretical framework lacking. Here, we develop a temporal coupled mode theory for thermal emission from multiple, arbtirarily-coupled resonators. We validate our theory against numerical simulations of complex two- and three-dimensional nanophotonic thermal emitters, highlighting the anomalous thermal emission spectra that can emerge when multiple resonators with arbitrary properties couple to each other with varying strengths.",2209.03951v1 2022-09-14,Nonlocal Superposed Solutions II: Coupled Nonlinear Equations,"We obtain novel periodic as well as hyperbolic solutions of an Ablowitz-Musslimani variant of the coupled nonlocal, nonlinear Schr\""odinger equation (NLS) as well as a coupled nonlocal modified Korteweg-de Vries (mKdV) equation which can be re-expressed as a linear superposition of the sum or the difference of two hyperbolic or two periodic kink or pulse solutions. Besides, we also discuss some of the other solutions admitted by these coupled equations. These results demonstrate that the notion of the superposed solutions extends to the coupled nonlocal nonlinear equations as well.",2209.06976v1 2022-10-18,Two-dimensional hydrodynamic simulation for synchronization in coupled density oscillators,"A density oscillator is a fluid system in which oscillatory flow occurs between different density fluids through the pore connecting them. We investigate the synchronization in coupled density oscillators using two-dimensional hydrodynamic simulation and analyze the stability of the synchronous state based on the phase reduction theory. Our results show that the anti-phase, three-phase, and 2-2 partial-in-phase synchronization modes spontaneously appear as stable states in two, three, and four coupled oscillators, respectively. The phase dynamics of coupled density oscillators is interpreted with their sufficiently large first Fourier components of the phase coupling function.",2210.09762v2 2022-11-20,Soliton dynamics to the coupled Higgs equation and its multi-component generalization,"In this paper, we study the coupled Higgs equation and its multi-component generalization based on the Hirota's direct method. One and two-soliton solutions of the coupled Higgs equation are derived by the perturbation approach. We express the N-soliton solutions in the form of Pfaffians and demonstrate that the N-component coupled Higgs equation turns out to be the Pfaffian identity. One and two-soliton solutions of the multi-component coupled Higgs equation are obtained from the Pfaffians. Starting from the explicit solutions, parallel solitons, periodic and nearly periodic interactions, elastic and inelastic collisions are investigated.",2211.10860v1 2023-01-10,Next nearest neighbour coupling with spinor polariton condensates,"We report on experimental observation of next-nearest-neighbour coupling between ballistically expanding spinor exciton-polariton condensates in a planar semiconductor microcavity. All-optical control over the coupling strength between neighbouring condensates is demonstrated through distance-periodic pseudospin screening of their ballistic particle outflow due to the inherent splitting of the planar cavity transverse-electric (TE) and transverse-magnetic (TM) modes. By screening the nearest-neighbour coupling we overcome the conventional spatial coupling hierarchy between condensates. This offers a promising route towards creating unconventional non-planar many-body Hamiltonians using networks of ballistically expanding spinor exciton-polariton condensates.",2301.04210v1 2023-01-30,Perturbative Quantum Gravity Induced Scalar Coupling to Electromagnetism,"Physicists working on atom interferometers are interested in scalar couplings to electromagnetism of dimensions 5 and 6 which might be induced by quantum gravity. There is a widespread belief that such couplings can only be induced by conjectured non-perturbative effects, resulting in unknown coupling strengths. In this letter we exhibit a completely perturbative mechanism through which quantum gravity induces dimension six couplings with precisely calculable coefficients.",2301.12611v2 2023-04-12,Long-range coupling between superconducting dots induced by periodic driving,"We consider a Josephson bijunction consisting of three superconducting reservoirs connected through two quantum dots. In equilibrium, the interdot coupling is sizable only for distances smaller than the superconducting coherence length. Application of commensurate dc voltages results in a time-periodic Hamiltonian and induces an interdot coupling at large distances. The basic mechanism of this long-range coupling is shown to be due to local multiple Andreev reflections on each dot, followed by quasiparticle propagation at energies larger than the superconducting gap. At large interdot distances we derive an effective non-Hermitian Hamiltonian describing two resonances coupled through a continuum.",2304.05987v1 2023-04-18,Spin-Gravity Coupling in a Rotating Universe,"The coupling of intrinsic spin with the nonlinear gravitomagnetic fields of Goedel-type spacetimes is studied. We work with Goedel-type universes in order to show that the main features of spin-gravity coupling are independent of causality problems of the Goedel universe. The connection between the spin-gravitomagnetic field coupling and Mathisson's spin-curvature force is demonstrated in the Goedel-type universe. That is, the gravitomagnetic Stern--Gerlach force due to the coupling of spin with the gravitomagnetic field reduces in the appropriate correspondence limit to the classical Mathisson spin-curvature force.",2304.08835v2 2023-04-18,Nonexistence of Solutions to the Coupled Generalized Jang Equation/Zero Divergence System,"In [5], Bray and Khuri proposed coupling the generalized Jang equation to several different auxiliary equations. The solutions to these coupled systems would then imply the Penrose inequality. One of these involves coupling the generalized Jang equation to $\overline{div}(\phi q)=0$, as this would guarantee the non-negativity of the scalar curvature in the Jang surface. This coupled system of equations has not received much attention, and we investigate it's solvability. We prove that there exists a spherically symmetric initial data set for the Einstein equations for which there do not exist smooth radial solutions to the system having the appropriate asymptotics for application to the Penrose inequality.",2304.09332v1 2023-05-12,Coupled-cluster theory for strong entanglement in nuclei,"Atomic nuclei can exhibit shape coexistence and multi-reference physics that enters in their ground states, and to accurately capture the ensuing correlations and entanglement is challenging. We address this problem by applying single-reference coupled-cluster theory based on spherical and deformed reference states and the tailored coupled-cluster method. The latter combines configuration interaction to capture static correlations with coupled-cluster theory for dynamic correlations. We compute the atomic nuclei $^{12}$C, $^{28}$Si, and $^{56}$Ni and find that the tailored coupled-cluster method and the single-reference approach based on a deformed Hartree-Fock state yield the most accurate results.",2305.07577v1 2023-08-02,Influence of band occupation on electron-phonon coupling in gold,"Electron-phonon coupling is a fundamental process that governs the energy relaxation dynamics of solids excited by ultrafast laser pulses. It has been found to strongly depend on electron temperature as well as on nonequilibrium effects. Recently, the effect of occupational nonequilibrium in noble metals, which outlasts the fully kinetic stage, has come into increased focus. In this work, we investigate the influence of nonequilibrium density distributions in gold on the electron-phonon coupling. We find a large effect on the coupling parameter which describes the energy exchange between the two subsystems. Our results challenge the conventional view that electron temperature alone is a sufficient predictor of electron-phonon coupling.",2308.01067v1 2023-08-07,Parametric excitations of coupled nanomagnets,"We demonstrate that parametrically excited eigenmodes in nearby nanomagnets can be coupled to each other. Both positive (in-phase) and negative (anti-phase) couplings can be realized by a combination of appropriately chosen geometry and excitation field frequency. The oscillations are sufficiently stable against thermal fluctuations. The phase relation between field-coupled nanomagnets shows a hysteretic behavior with the phase relation being locked over a wide frequency range. We envision that this computational study lays the groundwork to use field-coupled nanomagnets as parametrons as building blocks of logic devices, neuromorphic systems or Ising machines.",2308.03327v1 2023-08-10,A Generalized Primal-Dual Correction Method for Saddle-Point Problems with the Nonlinear Coupling Operator,"Recently, the generalized primal-dual (GPD) method was developed for saddle-point problems (SPPs) with a linear coupling operator. However, the coupling operator in many engineering applications is nonlinear. In this letter, we propose a generalized primal-dual correction method (GPD-CM) to handle SPPs with a nonlinear coupling operator. To achieve this, we customize the proximal matrix and corrective matrix by adjusting the values of regularization factors. By the unified framework, the convergence of GPD-CM is directly obtained. Numerical results on a SPP with an exponential coupling operator support theoretical analysis.",2308.05388v1 2023-08-17,Null controllability of two kinds of coupled parabolic systems with switching control,"The focus of this paper is on the null controllability of two kinds of coupled systems including both degenerate and non-degenerate equations with switching control. We first establish the observability inequality for measurable subsets in time for such coupled system, and then by the HUM method to obtain the null controllability. Next, we investigate the null controllability of such coupled system for segmented time intervals. Notably, these results are obtained through spectral inequalities rather than using the method of Carleman estimates. Such coupled systems with switching control, to the best of our knowledge, are among the first to discuss.",2308.08752v1 2023-09-27,Reconciling quantum and classical spectral theories of ultrastrong coupling: Role of cavity bath coupling and gauge corrections,"Focusing on the widely adopted Hopfield model with cavity dissipation, we show how the linear spectrum of an ultrastrongly coupled cavity and a dipole can be described either classically or quantum mechanically, but only when the quantum model includes (i) corrections to maintain gauge invariance, and (ii) a specific type of cavity bath coupling. We also show the impact of this bath model on the quantum Rabi model, which has no classical analogue in ultrastrong coupling.",2309.15788v2 2023-10-11,The Effect of Intra- and Inter-ring Couplings in Leaky Integrate-and-Fire Multiplex Networks,"We study the dynamics of identical Leaky Integrate-and-Fire (LIF) neurons on a multiplex composed of two ring networks with symmetric nonlocal coupling within each ring and one-to-one connections between rings. We investigate the impact of different intra-ring coupling strengths in the two rings for attractive and repulsive inter-ring coupling and show that they can lead to subthreshold oscillations. The corresponding parameter spaces where this phenomenon occurs are determined numerically. Moreover, we show that depending on whether the couplings between the two rings are attractive or repulsive, the interaction produces qualitatively different behavior in the synchronization patterns and the mean frequency profiles.",2310.07549v2 2023-11-10,One-loop RG Flow for Adjoint Multiscalar Gauge Theory,"We study the one-loop renormalisation of 4d SU(N) Yang-Mills theory with $M$ adjoint representation scalar multiplets. We calculate the coupled one-loop renormalization group flows for this theory by developing an algebraic description, which we find to be characterised by a non-associative algebra of marginal couplings. The 4d one-loop beta function of the gauge coupling $g^2$ vanishes for the case $M = 22$, which is intriguing for string theory. There are real fixed flows (fixed points of $\lambda/g^2$) only for $M\geq406$, rendering one-loop fixed points of the gauge coupling and scalar couplings incompatible.",2311.05993v1 2023-12-30,Dynamics of oscillator populations with disorder in the coupling phase shifts,"We study populations of oscillators, all-to-all coupled by means of quenched disordered phase shifts. While there is no traditional synchronization transition with a nonvanishing Kuramoto order parameter, the system demonstrates a specific order as the coupling strength increases. This order is characterized by partial phase locking, which is put into evidence by the introduced correlation order parameter and via frequency entrainment. Simulations with phase oscillators, Stuart-Landau oscillators, and chaotic Roessler oscillators demonstrate similar scaling of the correlation order parameter with the coupling and the system size and also similar behavior of the frequencies with maximal entrainment at some finite coupling.",2401.00281v1 2024-01-22,Weak and Strong Coupling Polarons in Binary Bose-Einstein Condensates,"The Bose polaron is a quasiparticle that arises from the interaction between impurities and Bogoliubov excitation in Bose-Einstein condensates, analogous to the polaron formed by electrons and phonons in solid-state physics. In this paper, we investigate the effect of phase separation on weakly coupled and strongly coupled Bose polarons. Our findings reveal that phase separation induces a remarkable alteration in the properties of weakly coupled Bose polarons. However, in the case of strong coupling, phase separation cannot destroy the polaron as a highly self-trapping state comes into existence.",2401.11808v1 2024-03-19,Renormalization of networks with weak geometric coupling,"The Renormalization Group is crucial for understanding systems across scales, including complex networks. Renormalizing networks via network geometry, a framework in which their topology is based on the location of nodes in a hidden metric space, is one of the foundational approaches. However, the current methods assume that the geometric coupling is strong, neglecting weak coupling in many real networks. This paper extends renormalization to weak geometric coupling, showing that geometric information is essential to preserve self-similarity. Our results underline the importance of geometric effects on network topology even when the coupling to the underlying space is weak.",2403.12663v1 2024-03-22,Stability of abstract coupled systems,"We study stability of abstract differential equations coupled by means of a general algebraic condition. Our approach is based on techniques from operator theory and systems theory, and it allows us to study coupled systems by exploiting properties of the components, which are typically much simpler to analyse. As our main results we establish resolvent estimates and decay rates for abstract boundary-coupled systems. We illustrate the power of the general results by using them to obtain rates of energy decay in coupled systems of one-dimensional wave and heat equations, and in a wave equation with an acoustic boundary condition.",2403.15253v1 1999-03-30,Gapless Singlet modes in the Kagome strips: A study through DMRG and strong coupling analysis,"Recently Azaria et al have studied strips of the Kagome-lattice in the weak-coupling limit, where they consist of two spin-half chains on the outside weakly coupled to an array of half-integer spins in the middle. Using a number of mappings they have arrived at the interesting result that in this system all spin excitations are gapped but there are gapless spinless modes. Here we study these Kagome strips in the limit where the interchain couplings are comparable to the coupling to the middle spins by density matrix renormalization group and by a strong coupling analysis. In the limit when the coupling to the middle-spin dominates, the 5-spins of the unit-cell reduce to a single S=3/2 spin, and the overall system has well known gapless spin excitations. We study the phase transition from this phase to the weak-coupling phase. We also carry out a strong coupling analysis away from the S=3/2 limit, where the five-spin blocks have four degenerate ground states with S=1/2, which can be thought of as two spin and two pseudospin degrees of freedom. A numerical study of this strong coupling model also suggests a finite spin-gap.",9903434v1 2006-08-08,Renormalization group study of the Kondo problem at a junction of several Luttinger wires,"We study a system consisting of a junction of N quantum wires, where the junction is characterized by a scalar S-matrix, and an impurity spin is coupled to the electrons close to the junction. The wires are modeled as weakly interacting Tomonaga-Luttinger liquids. We derive the renormalization group equations for the Kondo couplings of the spin to the electronic modes on different wires, and analyze the renormalization group flows and fixed points for different values of the initial Kondo couplings and of the junction S-matrix (such as the decoupled S-matrix and the Griffiths S-matrix). We generally find that the Kondo couplings flow towards large and antiferromagnetic values in one of two possible ways. For the Griffiths S-matrix, we study one of the strong coupling flows by a perturbative expansion in the inverse of the Kondo coupling; we find that at large distances, the system approaches the ferromagnetic fixed point of the decoupled S-matrix. For the decoupled S-matrix with antiferromagnetic Kondo couplings and weak inter-electron interactions, the flows are to one of two strong coupling fixed points in which all the channels are strongly coupled to each other through the impurity spin. But strong inter-electron interactions, with K_\rho < N/(N+2), stabilize a multi-channel fixed point in which the coupling between different channels goes to zero. We have also studied the temperature dependence of the conductance at the decoupled and Griffiths S-matrices.",0608187v1 2003-08-11,Understanding the Strong Coupling Limit of the ${\cal N}=4$ Supersymmetric Yang-Mills at Finite Temperature,"Recently, a number of intriguing results have been obtained for strongly coupled ${\cal N}=4$ Supersymmetric Yang-Mills theory in vacuum and matter, using the AdS/CFT correspondence. In this work, we provide a physical picture supporting and explaining most of these results within the gauge theory. The modified Coulomb's law at strong coupling forces static charges to communicate via the high frequency modes of the gauge/scalar fields. Therefore, the interaction between even relativistically moving charges can be approximated by a potential. At strong coupling, WKB arguments yield a series of deeply bound states, whereby the large Coulomb attraction is balanced by centrifugation. The result is a constant density of light bound states at {\bf any} value of the strong coupling, explaining why the thermodynamics and kinetics are coupling constant independent. In essence, at strong coupling the matter is not made of the original quasiparticles but of much lighter (binary) composites. A transition from weak to strong coupling is reminiscent to a transition from high to low $T$ in QCD. We establish novel results for screening in vacuum and matter through a dominant set of diagrams some of which are in qualitative agreement with known strong coupling results.",0308073v2 2006-07-28,Photon and dilepton production in supersymmetric Yang-Mills plasma,"By weakly gauging one of the U(1) subgroups of the R-symmetry group, N=4 super-Yang-Mills theory can be coupled to electromagnetism, thus allowing a computation of photon production and related phenomena in a QCD-like non-Abelian plasma at both weak and strong coupling. We compute photon and dilepton emission rates from finite temperature N=4 supersymmetric Yang-Mills plasma both perturbatively at weak coupling to leading order, and non-perturbatively at strong coupling using the AdS/CFT duality conjecture. Comparison of the photo-emission spectra for N=4 plasma at weak coupling, N=4 plasma at strong coupling, and QCD at weak coupling reveals several systematic trends which we discuss. We also evaluate the electric conductivity of N=4 plasma in the strong coupling limit, and to leading-log order at weak coupling. Current-current spectral functions in the strongly coupled theory exhibit hydrodynamic peaks at small frequency, but otherwise show no structure which could be interpreted as well-defined thermal resonances in the high-temperature phase.",0607237v2 2000-08-15,"CCT, a Code to Automate the Design of Coupled Cavities","The CCT (Coupled Cavity Tuning) code automates the RF calculations and sizing of RF cavities for the CCL (Coupled Cavity Linac) structures of APT. It is planned to extend the code to the CCDTL (Coupled Cavity Drift Tube Linac). The CCT code controls the CCLFISH code, a member of the Poisson Superfish series of codes [1]. CCLFISH performs RF calculations and tunes the geometry of individual cavities, including an accelerating cavity (AC) and a coupling cavity (CC). CCT also relates the AC and CC by means of equations that describe the coupling slot between cavities. These equations account for the direct coupling, the next nearest neighbor coupling between adjacent AC's, and the frequency shifts in the AC and CC caused by the slot. Given design objectives of a coupling coefficient k, the pi/2 mode frequency, and the net frequency of the CC, the CCT code iterates to solve for the geometry of the AC and CC and the separation distance between them (this controls the slot size), satisfying the design objectives. The resulting geometry is used to automate CAD drawing preparation. The code can also be used in ""as-designed"" mode to calculate the frequencies and coupling of a specified configuration. An overview of the code is presented.",0008073v1 2003-07-30,Theory of output coupling for trapped fermionic atoms,"We develop a dynamic theory of output coupling, for fermionic atoms initially confined in a magnetic trap. We consider an exactly soluble one-dimensional model, with a spatially localized delta-type coupling between the atoms in the trap and a continuum of free-particle external modes. Two important special cases are considered for the confinement potential: the infinite box and the harmonic oscillator. We establish that in both cases a bound state of the coupled system appears for any value of the coupling constant, implying that the trap population does not vanish in the infinite-time limit. For weak coupling, the energy spectrum of the outgoing beam exhibits peaks corresponding to the initially occupied energy levels in the trap; the height of these peaks increases with the energy. As the coupling gets stronger, the energy spectrum is displaced towards dressed energies of the fermions in the trap. The corresponding dressed states result from the coupling between the unperturbed fermionic states in the trap, mediated by the coupling between these states and the continuum. In the strong-coupling limit, there is a reinforcement of the lowest-energy dressed mode, which contributes to the energy spectrum of the outgoing beam more strongly than the other modes. This effect is especially pronounced for the one-dimensional box, which indicates that the efficiency of the mode-reinforcement mechanism depends on the steepness of the confinement potential. In this case, a quasi-monochromatic anti-bunched atomic beam is obtained. Results for a bosonic sample are also shown for comparison.",0307230v2 2007-09-21,Weak and strong coupling limits of the two-dimensional Fröhlich polaron with spin-orbit Rashba interaction,"The continuous progress in fabricating low-dimensional systems with large spin-orbit couplings has reached a point in which nowadays materials may display spin-orbit splitting energies ranging from a few to hundreds of meV. This situation calls for a better understanding of the interplay between the spin-orbit coupling and other interactions ubiquitously present in solids, in particular when the spin-orbit splitting is comparable in magnitude with characteristic energy scales such as the Fermi energy and the phonon frequency. In this article, the two-dimensional Fr\""ohlich electron-phonon problem is reformulated by introducing the coupling to a spin-orbit Rashba potential, allowing for a description of the spin-orbit effects on the electron-phonon interaction. The ground state of the resulting Fr\""ohlich-Rashba polaron is studied in the weak and strong coupling limits of the electron-phonon interaction for arbitrary values of the spin-orbit splitting. The weak coupling case is studied within the Rayleigh-Schr\""odinger perturbation theory, while the strong-coupling electron-phonon regime is investigated by means of variational polaron wave functions in the adiabatic limit. It is found that, for both weak and strong coupling polarons, the ground state energy is systematically lowered by the spin-orbit interaction, indicating that the polaronic character is strengthened by the Rashba coupling. It is also shown that, consistently with the lowering of the ground state, the polaron effective mass is enhanced compared to the zero spin-orbit limit. Finally, it is argued that the crossover between weakly and strongly coupled polarons can be shifted by the spin-orbit interaction.",0709.3429v2 2008-01-25,Magnetic order in coupled spin-half and spin-one Heisenberg chains in anisotropic triangular-lattice geometry,"We study spin-half and spin-one Heisenberg models in the limit where one dimensional (1-D) linear chains, with exchange constant J1, are weakly coupled in an anisotropic triangular lattice geometry. Results are obtained by means of linked-cluster series expansions at zero temperature around different magnetically ordered phases. We study the non-colinear spiral phases that arise classically in the model and the colinear antiferromagnet that has been recently proposed for the spin-half model by Starykh and Balents using a Renormalization Group approach. We find that such phases can be stabilized in the spin-half model for arbitrarily small coupling between the chains. For vanishing coupling between the chains the energy of each phase must approach that of decoupled linear chains. With increasing inter-chain coupling, the non-colinear phase appears to have a lower energy in our calculations. For the spin-one chain, we find that there is a critical interchain coupling needed to overcome the Haldane gap. When spin-one chains are coupled in an unfrustrated manner, the critical coupling is very small (~0.01J1) and agrees well with previous chain mean-field studies. When they are coupled in the frustrated triangular-lattice geometry, the critical coupling required to develop magnetic order is substantially larger (> 0.3J1). The colinear phase is not obtained for the spin-one Heisenberg model.",0801.3855v1 2008-03-07,On the running of the bare coupling in SU(N) lattice gauge theories,"Interpreting the way that the SU(3) bare lattice coupling runs with the lattice spacing is complicated by the fact that there is a smooth cross-over region in which the strong coupling expansion transforms into a weak-coupling one. For N > 4, however, there is a first order bulk transition that cleanly separates the strong and weak coupling regimes. We find that in this case the calculated string tension can be readily fitted throughout the weak coupling region by a standard 3-loop expression modified by lattice spacing corrections of the expected form. While our fits demand the presence of the latter, they do not constrain the perturbative coupling scheme enough to enable us to extract a usefully accurate value of a(beta) in units of Lambda_MSbar. To resolve this ambiguity we turn to SU(3) where we use the Schrodinger Functional coupling scheme to extract a value of r_0 x Lambda_SF as a benchmark. We then find that the Parisi mean-field improved coupling scheme closely reproduces this result. We also develop a comparison between different schemes that does not rely on the calculation of any physical quantity and which can therefore be applied much further into weak coupling. Again the Parisi scheme is favoured over the others that we compare. Using the mean-field scheme we have fitted the values of the string tension that have been calculated for N=2 to N=8, to obtain Lambda_MSbar/sqrt(sigma) = 0.503(2)(40) + 0.33(3)(3)/N^2 for N > 2, where the first error is statistical and the second is our estimate of the systematic error from all sources.",0803.1092v1 2008-03-13,Late universe dynamics with scale-independent linear couplings in the dark sector,"We explore the dynamics of cosmological models with two coupled dark components with energy densities $\rho_A$ and $\rho_B$. We assume that the coupling is of the form $Q=Hq(\rho_A,\rho_B)$, so that the dynamics of the two components turns out to be scale independent, i.e. does not depend explicitly on the Hubble scalar $H$. With this assumption, we focus on the general linear coupling $q=q_o+q_A\rho_A+q_B\rho_B$, which may be seen as arising from any $q(\rho_A,\rho_B)$ at late time and leads in general to an effective cosmological constant. In the second part of the paper we consider observational constraints on the form of the coupling from SN Ia data, assuming that one of the components is cold dark matter. We find that the constant part of the coupling function is unconstrained by SN Ia data and, among typical linear coupling functions, the one proportional to the dark energy density $\rho_{A}$ is preferred in the strong coupling regime, $|q_{A}|>1$. While phantom models favor a positive coupling function, in non-phantom models, not only a negative coupling function is allowed, but the uncoupled sub-case falls at the border of the likelihood.",0803.1976v2 2008-09-15,"Interlayer coupling in EuS/SrS, EuS/PbSe and EuS/PbTe magnetic semiconductor superlatices","Neutron reflectivity studies of EuS/SrS, EuS/PbSe, and EuS/PbTe all-semiconductor superlattices were carried out in search for exchange interlayer coupling. A relatively weak antiferromagnetic coupling was found in EuS/SrS and in EuS/PbSe systems but no interlayer coupling was detected in EuS/PbTe superlattices. In EuS/SrS, where the SrS spacer is an insulator ($E_g\approx 4$ eV), a very weak and short range interlayer coupling is in agreement with the earlier theoretical predictions that the interlayer coupling strength in EuS-based magnetic semiconductor superlattices depends strongly on the energy gap of the nonmagnetic layer and should decrease with an increase of the energy gap of the spacer material. A weak coupling in EuS/PbSe and no coupling in EuS/PbTe, where both PbSe and PbTe are narrow-gap semiconductors ($E_g\approx 0.3$ eV), is in disagreement not only with the theoretical expectations but also in a stark contrast with earlier results for another narrow-gap spacer system -- EuS/PbS, where pronounced antiferromagnetic coupling persists even in samples with PbS layer thickness as large as 200 \AA. A possible influence of the increasing lattice mismatch between EuS and the spacer materials (0.5%, 0.8%, 2.5%, and 8.2% for PbS, SrS, PbSe, and PbTe, respectively) on the magnetic in-plane ordering of EuS layer and, consequently, on the interlayer coupling was investigated by polarized neutron reflectometry in the case of EuS/PbTe.",0809.2529v1 2010-06-14,Scaling and synchronization in a ring of diffusively coupled nonlinear oscillators,"Chaos synchronization in a ring of diffusively coupled nonlinear oscillators driven by an external identical oscillator is studied. Based on numerical simulations we show that by introducing additional couplings at $(mN_c+1)$-th oscillators in the ring, where $m$ is an integer and $N_c$ is the maximum number of synchronized oscillators in the ring with a single coupling, the maximum number of oscillators that can be synchronized can be increased considerably beyond the limit restricted by size instability. We also demonstrate that there exists an exponential relation between the number of oscillators that can support stable synchronization in the ring with the external drive and the critical coupling strength $\epsilon_c$ with a scaling exponent $\gamma$. The critical coupling strength is calculated by numerically estimating the synchronization error and is also confirmed from the conditional Lyapunov exponents (CLEs) of the coupled systems. We find that the same scaling relation exists for $m$ couplings between the drive and the ring. Further, we have examined the robustness of the synchronous states against Gaussian white noise and found that the synchronization error exhibits a power-law decay as a function of the noise intensity indicating the existence of both noise-enhanced and noise-induced synchronizations depending on the value of the coupling strength $\epsilon$. In addition, we have found that $\epsilon_c$ shows an exponential decay as a function of the number of additional couplings. These results are demonstrated using the paradigmatic models of R\""ossler and Lorenz oscillators.",1006.2621v1 2011-03-17,A spin-orbit coupled Bose-Einstein condensate,"Spin-orbit (SO) coupling -- the interaction between a quantum particle's spin and its momentum -- is ubiquitous in nature, from atoms to solids. In condensed matter systems, SO coupling is crucial for the spin-Hall effect and topological insulators, which are of extensive interest; it contributes to the electronic properties of materials such as GaAs, and is important for spintronic devices. Ultracold atoms, quantum many-body systems under precise experimental control, would seem to be an ideal platform to study these fascinating SO coupled systems. While an atom's intrinsic SO coupling affects its electronic structure, it does not lead to coupling between the spin and the center-of-mass motion of the atom. Here, we engineer SO coupling (with equal Rashba and Dresselhaus strengths) in a neutral atomic Bose-Einstein condensate by dressing two atomic spin states with a pair of lasers. Not only is this the first SO coupling realized in ultracold atomic gases, it is also the first ever for bosons. Furthermore, in the presence of the laser coupling, the interactions between the two dressed atomic spin states are modified, driving a quantum phase transition from a spatially spin-mixed state (lasers off) to a phase separated state (above a critical laser intensity). The location of this transition is in quantitative agreement with our theory. This SO coupling -- equally applicable for bosons and fermions -- sets the stage to realize topological insulators in fermionic neutral atom systems.",1103.3522v1 2011-04-04,Near concavity of the growth rate for coupled LDPC chains,"Convolutional Low-Density-Parity-Check (LDPC) ensembles have excellent performance. Their iterative threshold increases with their average degree, or with the size of the coupling window in randomized constructions. In the later case, as the window size grows, the Belief Propagation (BP) threshold attains the maximum-a-posteriori (MAP) threshold of the underlying ensemble. In this contribution we show that a similar phenomenon happens for the growth rate of coupled ensembles. Loosely speaking, we observe that as the coupling strength grows, the growth rate of the coupled ensemble comes close to the concave hull of the underlying ensemble's growth rate. For ensembles randomly coupled across a window the growth rate actually tends to the concave hull of the underlying one as the window size increases. Our observations are supported by the calculations of the combinatorial growth rate, and that of the growth rate derived from the replica method. The observed concavity is a general feature of coupled mean field graphical models and is already present at the level of coupled Curie-Weiss models. There, the canonical free energy of the coupled system tends to the concave hull of the underlying one. As we explain, the behavior of the growth rate of coupled ensembles is exactly analogous.",1104.0599v1 2012-02-08,Transport through side-coupled double quantum dots: from weak to strong interdot coupling,"We report low-temperature transport measurements through a double quantum dot device in a configuration where one of the quantum dots is coupled directly to the source and drain electrodes, and a second (side-coupled) quantum dot interacts electrostatically and via tunneling to the first one. As the interdot coupling increases, a crossover from weak to strong interdot tunneling is observed in the charge stability diagrams that present a complex pattern with mergings and apparent crossings of Coulomb blockade peaks. While the weak coupling regime can be understood by considering a single level on each dot, in the intermediate and strong coupling regimes, the multi-level nature of the quantum dots needs to be taken into account. Surprisingly, both in the strong and weak coupling regimes, the double quantum dot states are mainly localized on each dot for most values of the parameters. Only in an intermediate coupling regime the device presents a single dot-like molecular behavior as the molecular wavefunctions weight is evenly distributed between the quantum dots. At temperatures larger than the interdot coupling energy scale, a loss of coherence of the molecular states is observed.",1202.1580v1 2012-06-15,Coupled motion of asymmetrical tilt grain boundaries: molecular dynamics and phase field crystal simulations,"Previous simulation and experimental studies have shown that some grain boundaries (GBs) can couple to applied shear stresses and be moved by them, producing shear deformation of the lattice traversed by their motion. While this coupling effect has been well confirmed for symmetrical tilt GBs, little is known about the coupling ability of asymmetrical boundaries. In this work we apply a combination of molecular dynamics and phase field crystal simulations to investigate stress-driven motion of asymmetrical GBs between cubic crystals over the entire range of inclination angles. Our main findings are that the coupling effect exists for most of the asymmetrical GBs and that the coupling factor exhibits a non-trivial dependence on both the misorientation and inclination angles. This dependence is characterized by a discontinuous change of sign of the coupling factor, which reflects a transition between two different coupling modes over a narrow range of angles. Importantly, the magnitude of the coupling factor becomes large or divergent within this transition region, thereby giving rise to a sliding-like behavior. Our results are interpreted in terms of a diagram presenting the domains of existence of the two coupling modes and the transition region between them in the plane of misorientation and inclination angles. The simulations reveal some of the dislocation mechanisms responsible for the motion of asymmetrical tilt GBs. The results of this study compare favorably with existing experimental measurements and provide a theoretical ground for the design of future experiments.",1206.3549v1 2012-07-20,Transition to complete synchronization and global intermittent synchronization in an array of time-delay systems,"We report the nature of transitions from nonsynchronous to complete synchronization (CS) state in arrays of time-delay systems, where the systems are coupled with instantaneous diffusive coupling. We demonstrate that the transition to CS occurs distinctly for different coupling configurations. In particular, for unidirectional coupling, locally (microscopically) synchronization transition occurs in a very narrow range of coupling strength but for a global one (macroscopically) it occurs sequentially in a broad range of coupling strength preceded by an intermittent synchronization. On the other hand, in the case of mutual coupling a very large value of coupling strength is required for local synchronization and, consequently, all the local subsystems synchronize immediately for the same value of the coupling strength and hence globally synchronization also occurs in a narrow range of the coupling strength. In the transition regime, we observe a new type of synchronization transition where long intervals of high quality synchronization which are interrupted at irregular times by intermittent chaotic bursts simultaneously in all the systems, which we designate as global intermittent synchronization (GIS). We also relate our synchronization transition results to the above specific types using unstable periodic orbit theory. The above studies are carried out in a well known piecewise linear time-delay system.",1207.4888v1 2013-01-22,Validity of single-channel model for a spin-orbit coupled atomic Fermi gas near Feshbach resonances,"We theoretically investigate a Rashba spin-orbit coupled Fermi gas near Feshbach resonances, by using mean-field theory and a two-channel model that takes into account explicitly Feshbach molecules in the close channel. In the absence of spin-orbit coupling, when the channel coupling $g$ between the closed and open channels is strong, it is widely accepted that the two-channel model is equivalent to a single-channel model that excludes Feshbach molecules. This is the so-called broad resonance limit, which is well-satisfied by ultracold atomic Fermi gases of $^{6}$Li atoms and $^{40}$K atoms in current experiments. Here, with Rashba spin-orbit coupling we find that the condition for equivalence becomes much more stringent. As a result, the single-channel model may already be insufficient to describe properly an atomic Fermi gas of $^{40}$K atoms at a moderate spin-orbit coupling. We determine a characteristic channel coupling strength $g_{c}$ as a function of the spin-orbit coupling strength, above which the single-channel and two-channel models are approximately equivalent. We also find that for narrow resonance with small channel coupling, the pairing gap and molecular fraction is strongly suppressed by SO coupling. Our results can be readily tested in $^{40}$K atoms by using optical molecular spectroscopy.",1301.5071v1 2014-11-27,Cosmological Tests of Coupled Galileons,"We investigate the cosmological properties of Galileon models with positive kinetic terms. We include both conformal and disformal couplings to matter and focus on constraints on the theory that arise because of these couplings. The disformal coupling to baryonic matter is extremely constrained by astrophysical and particle physics effects. The disformal coupling to photons induces a cosmological variation of the speed of light and therefore distortions of the Cosmic Microwave Background spectrum which are known to be very small. The conformal coupling to baryons leads to a variation of particle masses since Big Bang Nucleosynthesis which is also tightly constrained. We consider the background cosmology of Galileon models coupled to Cold Dark Matter (CDM), photons and baryons and impose that the speed of light and particle masses respect the observational bounds on cosmological time scales. We find that requiring that the equation of state for the Galileon models must be close to -1 now restricts severely their parameter space and can only be achieved with a combination of the conformal and disformal couplings. This leads to large variations of particle masses and the speed of light which are not compatible with observations. As a result, we find that cosmological Galileon models are viable dark energy theories coupled to dark matter but their couplings, both disformal and conformal, to baryons and photons must be heavily suppressed making them only sensitive to CDM.",1411.7621v1 2014-12-02,The $SU(\infty)$ twisted gradient flow running coupling,"We measure the running of the $SU(\infty)$ 't Hooft coupling by performing a step scaling analysis of the Twisted Eguchi-Kawai (TEK) model, the SU($N$) gauge theory on a single site lattice with twisted boundary conditions. The computation relies on the conjecture that finite volume effects for SU(N) gauge theories defined on a 4-dimensional twisted torus are controlled by an effective size parameter $\tilde l = l \sqrt{N}$, with $l$ the torus period. We set the scale for the running coupling in terms of $\tilde l$ and use the gradient flow to define a renormalized 't Hooft coupling $\lambda(\tilde l)$. In the TEK model, this idea allows the determination of the running of the coupling through a step scaling procedure that uses the rank of the group as a size parameter. The continuum renormalized coupling constant is extracted in the zero lattice spacing limit, which in the TEK model corresponds to the large $N$ limit taken at fixed value of $\lambda(\tilde l)$. The coupling constant is thus expected to coincide with that of the ordinary pure gauge theory at $N =\infty$. The idea is shown to work and permits us to follow the evolution of the coupling over a wide range of scales. At weak coupling we find a remarkable agreement with the perturbative two-loop formula for the running coupling.",1412.0941v1 2015-03-31,Probing Higgs couplings at LHC and beyond,"The study of the Higgs couplings following its discovery is the priority of future LHC runs. A hint of anomalous nature will be exhibited via its coupling to the Standard Model(SM) particles and open up new domain of phenomenological study of physics beyond the Standard Model. The enhanced statistics from next LHC runs will enable entry into the precision era to study the properties of Higgs with greater details. In this paper we present how one can extract Higgs couplings in future LHC runs at 14 TeV via $H \rightarrow Z Z^* \rightarrow 4 \ell$, using observables constructed from angular distributions for the Standard Model Higgs and Higgs with mixed CP configuration. We show how angular asymmetries can be used to measure the ratios of the couplings and the relative phases at LHC. We benchmark our analysis finding out the angular asymmetries and the best fit values of the ratios of the couplings for SM Higgs, CP-odd admixture, CP-even higher derivative contribution and when CP-even higher derivative contribution and CP-odd admixture are both present. In the Standard Model, $HZZ$ couplings have no momentum dependence. It is thus essential to demonstrate the momentum independence of the couplings to establish the couplings are SM like in nature. In this work we show how one can test the momentum independence of the Standard Model like coupling using angular asymmetries. We develop the necessary tools and demonstrate how to study the momentum dependence can be studied at future LHC runs.",1503.08924v1 2015-04-13,Quantum theory of light emission from quantum dots coupled to structured photonic reservoirs and acoustic phonons,"Electron-phonon coupling in semiconductor quantum dots plays a significant role in determining the optical properties of excited excitons, especially the spectral nature of emitted photons. This paper presents a comprehensive theory and analysis of emission spectra from artificial atoms or quantum dots coupled to structured photon reservoirs and acoustic phonons, when excited with incoherent pump fields. As specific examples of structured reservoirs, we chose a Lorentzian cavity and a coupled cavity waveguide, which are of current experimental interest. For the case of optical cavities, we directly compare and contrast the spectra from three distinct theoretical approaches to treat electron-phonon coupling, including a Markovian polaron master equation, a non-Markovian phonon correlation expansion technique and a semiclassical linear susceptibility approach, and we point out the limitations of these models. For the cavity-QED polaron master equation, we give closed form analytical solutions to the phonon-assisted scattering rates in the weak excitation approximation, fully accounting for temperature, cavity-exciton detuning and cavity dot coupling. We show explicitly why the semiclassical linear susceptibility approach fails to correctly account for phonon-mediated cavity feeding. For weakly coupled cavities, we calculate the optical spectra using a more general reservoir approach and explain its differences from the above approaches in the low Q limit of a Lorentzian cavity. We subsequently use this general reservoir to calculate the emission spectra from quantum dots coupled to slow-light photonic crystal waveguides, which demonstrate a number of striking photon-phonon coupling effects. Our quantum theory can be applied to a wide range of photonic structures including photonic molecules and coupled-cavity waveguide systems.",1504.03356v1 2015-06-15,Coupled intertwiner dynamics: A toy model for coupling matter to spin foam models,"The universal coupling of matter and gravity is one of the most important features of general relativity. In quantum gravity, in particular spin foams, matter couplings have been defined in the past, yet the mutual dynamics, in particular if matter and gravity are strongly coupled, are hardly explored, which is related to the definition of both matter and gravitational degrees of freedom on the discretisation. However extracting this mutual dynamics is crucial in testing the viability of the spin foam approach and also establishing connections to other discrete approaches such as lattice gauge theories. Therefore, we introduce a simple 2D toy model for Yang--Mills coupled to spin foams, namely an Ising model coupled to so--called intertwiner models defined for $\text{SU}(2)_k$. The two systems are coupled by choosing the Ising coupling constant to depend on spin labels of the background, as these are interpreted as the edge lengths of the discretisation. We coarse grain this toy model via tensor network renormalization and uncover an interesting dynamics: the Ising phase transition temperature turns out to be sensitive to the background configurations and conversely, the Ising model can induce phase transitions in the background. Moreover, we observe a strong coupling of both systems if close to both phase transitions.",1506.04749v3 2015-10-30,Polarization of the top quark as a probe of its chromomagnetic and chromoelectric couplings in single-top production at the Large Hadron Collider,"We study the sensitivity of the Large Hadron Collider (LHC) to top quark chromomagnetic (CMDM) and chromoelectric (CEDM) dipole moments and $Wtb$ effective couplings in single-top production in association with a $W^-$ boson, followed by semileptonic decay of the top. We calculate the top polarization and the effects of these anomalous couplings on it at two centre-of-mass (cm) energies, 8 TeV and 14 TeV. As a measure of top polarization, we look at decay-lepton angular distributions in the laboratory frame, without requiring reconstruction of the rest frame of the top, and study the effect of the anomalous couplings on these distributions. We construct certain asymmetries to study the sensitivity of these distributions to top-quark couplings. The Wt single-top production mode helps to isolate the anomalous $ttg$ and $Wtb$ couplings, in contrast to top-pair production and other single-top production modes, where other new-physics effects can also contribute. We determine individual limits on the dominant couplings, viz., the real part of the CMDM $Re\rho_2$, the imaginary part of the CEDM $Im\rho_3$, and the real part of the tensor Wtb coupling $Ref_{2r}$, which may be obtained by utilizing these asymmetries at the LHC. We also obtain simultaneous limits on pairs of these couplings taking two couplings to be non-zero at a time.",1510.08959v1 2016-07-04,Implications of Coupling in Quantum Thermodynamic Machines,"We study coupled quantum systems as the working media of thermodynamic machines. Under a suitable phase-space transformation, the coupled systems can be expressed as a composition of independent subsystems. We find that for the coupled systems, the figures of merit, that is the efficiency for engine and the coefficient of performance for refrigerator, are bounded (both from above and from below) by the corresponding figures of merit of the independent subsystems. We also show that the optimum work extractable from a coupled system is upper bounded by the optimum work obtained from the uncoupled system, thereby showing that the quantum correlations do not help in optimal work extraction. Further, we study two explicit examples, coupled spin-$1/2$ systems and coupled quantum oscillators with analogous interactions. Interestingly, for particular kind of interactions, the efficiency of the coupled oscillators outperforms that of the coupled spin-$1/2$ systems when they work as heat engines. However, for the same interaction, the coefficient of performance behaves in a reverse manner, while the systems work as the refrigerator. Thus the same coupling can cause opposite effects in the figures of merit of heat engine and refrigerator.",1607.00994v3 2016-07-07,Testing the running coupling $k_{T}$-factorization formula for the inclusive gluon production,"The inclusive gluon production at midrapidities is described in the Color Glass Condensate formalism using the $k_T$ - factorization formula, which was derived at fixed coupling constant considering the scattering of a dilute system of partons with a dense one. Recent analysis demonstrated that this approach provides a satisfactory description of the experimental data for the inclusive hadron production in $pp/pA/AA$ collisions. However, these studies are based on the fixed coupling $k_T$ - factorization formula, which does not take into account the running coupling corrections, which are important to set the scales present in the cross section. In this paper we consider the running coupling corrected $k_T$ - factorization formula conjectured some years ago and investigate the impact of the running coupling corrections on the observables. In particular, the pseudorapidity distributions and charged hadrons multiplicity are calculated considering $pp$, $dAu/pPb$ and $AuAu/PbPb$ collisions at RHIC and LHC energies. We compare the corrected running coupling predictions with those obtained using the original $k_T$ - factorization assuming a fixed coupling or a prescription for the inclusion of the running of the coupling. Considering the Kharzeev - Levin - Nardi unintegrated gluon distribution and a simplified model for the nuclear geometry, we demonstrate that the distinct predictions are similar for the pseudorapidity distributions in $pp/pA/AA$ collisions and for the charged hadrons multiplicity in $pp/pA$ collisions. On the other hand, the running coupling corrected $k_T$ - factorization formula predicts a smoother energy dependence for $dN/d\eta$ in $AA$ collisions.",1607.02082v1 2018-11-28,Signature of the transition to a bound state in thermoelectric quantum transport,"We study a quantum dot coupled to two semiconducting reservoirs, when the dot level and the electrochemical potential are both close to a band edge in the reservoirs. This is modelled with an exactly solvable Hamiltonian without interactions (the Fano-Anderson model). The model is known to show an abrupt transition as the dot-reservoir coupling is increased into the strong-coupling regime for a broad class of band structures. This transition involves an infinite-lifetime bound state appearing in the band gap. We find a signature of this transition in the continuum states of the model, visible as a discontinuous behaviour of the dot's transmission function. This can result in the steady-state DC electric and thermoelectric responses having a very strong dependence on coupling close to critical coupling. We give examples where the conductances and the thermoelectric power factor exhibit huge peaks at critical coupling, while the thermoelectric figure of merit ZT grows as the coupling approaches critical coupling, with a small dip at critical coupling. The critical coupling is thus a sweet spot for such thermoelectric devices, as the power output is maximal at this point without a significant change of efficiency.",1811.11550v4 2012-01-24,New insights on the matter-gravity coupling paradigm,"The coupling between matter and gravity in General Relativity is given by a proportionality relation between the stress tensor and the geometry. This is an oriented assumption driven by the fact that both the stress tensor and the Einstein tensor are divergenceless. However, General Relativity is in essence a nonlinear theory, so there is no obvious reason why the coupling to matter should be linear. On another hand, modified theories of gravity usually affect the vacuum dynamics, yet keep the coupling to matter linear. In this Letter we address the implications of consistent nonlinear gravity/matter coupling. The Eddington inspired Born-Infeld theory recently introduced by Banados and Ferreira provides an enlightening realization of such coupling modifications. We find that this theory coupled to a perfect fluid reduces to General Relativity coupled to a nonlinearly modified perfect fluid, leading to an ambiguity between modified coupling and modified equation of state. We discuss observational consequences of this degeneracy and argue that such a completion of General Relativity is viable from both an experimental and theoretical point of view through energy conditions, consistency, and singularity-avoidance perspectives. We use these results to discuss the impact of changing the coupling paradigm.",1201.4989v3 2016-08-23,Coupling ideality of integrated planar high-Q microresonators,"Chipscale microresonators with integrated planar optical waveguides are useful building blocks for linear, nonlinear and quantum optical devices. Loss reduction through improving fabrication processes has resulted in several integrated micro resonator platforms attaining quality (Q) factors of several millions. However only few studies have investigated design-dependent losses, especially with regard to the resonator coupling section. Here we investigate design-dependent parasitic losses, described by the coupling ideality, of the commonly employed microresonator design consisting of a microring resonator waveguide side-coupled to a straight bus waveguide. By systematic characterization of multi-mode high-Q silicon nitride microresonator devices, we show that this design can suffer from low coupling ideality. By performing full 3D simulations to numerically investigate the resonator to bus waveguide coupling, we identify the coupling to higher-order bus waveguide modes as the dominant origin of parasitic losses which lead to the low coupling ideality. Using suitably designed bus waveguides, parasitic losses are mitigated, and a nearly unity ideality and strong overcoupling (i.e. a ratio of external coupling to internal resonator loss rate > 9) are demonstrated. Moreover we find that different resonator modes can exchange power through the coupler, which therefore constitutes a mechanism that induces modal coupling, a phenomenon known to distort resonator dispersion properties. Our results demonstrate the potential for significant performance improvements of integrated planar microresonators, achievable by optimized coupler designs.",1608.06607v1 2017-06-25,Understanding the different exciton-plasmon coupling regimes in two-dimensional semiconductors coupled with plasmonic lattices: a combined experimental and unified equations of motion approach,"We study exciton-plasmon coupling in two-dimensional semiconductors coupled with Ag plasmonic lattices via angle-resolved reflectance spectroscopy and by solving the equations of motion (EOMs) in a coupled oscillator model accounting for all the resonances of the system. Five resonances are considered in the EOM model: semiconductor A and B excitons, localized surface plasmon resonances (LSPRs) of plasmonic nanostructures and the lattice diffraction modes of the plasmonic array. We investigated the exciton-plasmon coupling in different 2D semiconductors and plasmonic lattice geometries, including monolayer MoS2 and WS2 coupled with Ag nanodisk and bowtie arrays, and examined the dispersion and lineshape evolution in the coupled systems via the EOM model with different exciton-plasmon coupling parameters. The EOM approach provides a unified description of the exciton-plasmon interaction in the weak, intermediate and strong coupling cases with correctly explaining the dispersion and lineshapes of the complex system. This study provides a much deeper understanding of light-matter interactions in multilevel systems in general and will be useful to instruct the design of novel two-dimensional exciton-plasmonic devices for a variety of optoelectronic applications with precisely tailored responses.",1706.08024v1 2017-05-04,Relativistic quantum dynamics of scalar bosons under a full vector Coulomb interaction,"The relativistic quantum dynamics of scalar bosons in the background of a full vector coupling (minimal plus nonminimal vector couplings) is explored in the context of the Duffin-Kemmer-Petiau formalism. The Coulomb phase shift is determined for a general mixing of couplings and it is shown that the space component of the nonminimal coupling is a {\it sine qua non} condition for the exact closed-form scattering amplitude. It follows that the Rutherford cross section vanishes in the absence of the time component of the minimal coupling. Bound-state solutions obtained from the poles of the partial scattering amplitude show that the time component of the minimal coupling plays an essential role. The bound-state solutions depend on the nonminimal coupling and the spectrum consists of particles or antiparticles depending on the sign of the time component of the minimal coupling without chance for pair production even in the presence of strong couplings. It is also shown that an accidental degeneracy appears for a particular mixing of couplings.",1705.01810v1 2018-06-20,Universal method for realization of strong light-matter coupling in hierarchical microcavity-plasmon-exciton systems,"Polaritons are compositional light-matter quasiparticles that arise as a result of strong coupling between a vacuum field of a resonant optical cavity and electronic excitations in quantum emitters. Reaching such a regime is often hard, as it requires materials possessing high oscillator strengths to interact with the relevant optical mode. Two dimensional transition metal dichalcogenides (TMDs) have recently emerged as promising candidates for realization of the strong coupling regime at room temperature. However, these materials typically provide coupling strengths in the range of 10-40 meV, which may be insufficient for reaching strong coupling with low quality factor resonators. Here, we demonstrate a universal scheme that allows a straightforward realization of strong and ultra-strong coupling regime with 2D materials and beyond. By intermixing plasmonic excitations in nanoparticle arrays with excitons in a WS2 monolayer inside a resonant metallic microcavity, we fabricate a hierarchical system with the combined Rabi splitting exceeding 500 meV at room temperature. Photoluminescence measurements of the coupled systems show dominant emission from the lower polariton branch, indicating the participation of excitons in the coupling process. Strong coupling has been recently suggested to affect numerous optical- and material-related properties including chemical reactivity, exciton transport and optical nonlinearities. With the universal scheme presented here, strong coupling across a wide spectral range is within easy reach and therefore exploring these exciting phenomena can be further pursued in a much broader class of materials.",1806.07784v1 2019-03-05,Strong Vibrational Coupling in Room Temperature Plasmonic Resonators,"Strong vibrational coupling has been realized in a variety of mechanical systems from cavity optomechanics to electromechanics.$^{1, 2, 3, 4, 5}$ It is an essential requirement for enabling quantum control over the vibrational states.$^{6, 7, 8, 9, 10, 11}$ The majority of the mechanical systems that have been studied to date are vibrational resonances of dielectric or semiconductor nanomaterials coupled to optical modes.$^{12, 13, 14, 15}$ While there are fewer studies of coupling between two mechanical modes,$^{3, 9}$ particularly, there have been no experimental observation of strong coupling of the ultra-high frequency acoustic modes of plasmonic nanostructures, due to the rapid energy dissipation in these systems. Here we realized strong vibrational coupling in ultra-high frequency plasmonic nanoresonators by increasing the vibrational quality factors by an order of magnitude. This is achieved through blocking an energy dissipation pathway in the form of out-going acoustic waves. We achieved the highest frequency quality factor products of $\mathbf{f}\times\mathbf{Q}=1.0\times10^{13}$ Hz for the fundamental mechanical modes in room temperature plasmonic nanoresonators reported to date, which exceeds the value of $0.1\times10^{13}$ Hz required for ground state cooling. Avoided crossing were observed between the vibrational modes of two plasmonic nanoresonators with a coupling rate of $\mathbf{g}=7.5\pm 1.2$ GHz, an order of magnitude larger than the dissipation rates. The intermodal strong coupling was consistent with theoretical calculations using a coupled oscillator model. Our results expanded the strong coupling systems for mechanical resonators and enabled a platform for future observation and control of the quantum behavior of phonon modes in metallic nanoparticles.",1903.01670v1 2019-03-15,Simulating Anisotropic quantum Rabi model via frequency modulation,"Anisotropic quantum Rabi model is a generalization of quantum Rabi model, which allows its rotating and counter-rotating terms to have two different coupling constants. It provides us with a fundamental model to understand various physical features concerning quantum optics, solid-state physics, and mesoscopic physics. In this paper, we propose an experimental feasible scheme to implement anisotropic quantum Rabi model in a circuit quantum electrodynamics system via periodic frequency modulation. An effective Hamiltonian describing the tunable anisotropic quantum Rabi model can be derived from a qubit-resonator coupling system modulated by two periodic driving fields. All effective parameters of the simulated system can be adjusted by tuning the initial phases, the frequencies and the amplitudes of the driving fields. We show that the periodic driving is able to drive a coupled system in dispersive regime to ultrastrong coupling regime, and even deep-strong coupling regime. The derived effective Hamiltonian allows us to obtain pure rotating term and counter-rotating term. Numerical simulation shows that such effective Hamiltonian is valid in ultrastrong coupling regime, and stronger coupling regime. Moreover, our scheme can be generalized to the multi-qubit case. We also give some applications of the simulated system to the Schr\""{o}dinger cat states and quantum gate generalization. The presented proposal will pave a way to further study the stronger anisotropic Rabi model whose coupling strength is far away from ultrastrong coupling and deep-strong coupling regimes in quantum optics.",1903.06347v1 2019-04-24,Manipulating Coherent Light Matter Interaction: Continuous Transition between Strong Coupling and Weak Coupling in MoS2 Monolayer Coupled with Plasmonic Nanocavities,"Strong interactions between surface plasmons in ultra-compact nanocavities and excitons in two dimensional materials have attracted wide interests for its prospective realization of polariton devices at room temperature. Here, we propose a continuous transition from weak coupling to strong coupling between excitons in MoS2 monolayer and highly localized plasmons in ultra-compact nanoantenna. The nanoantenna is assembled by a silver nanocube positioned over a gold film and separated by a dielectric spacer layer. We observed a 1570-fold enhancement in the photoluminescence at weak coupling regime in hybrid nanocavities with thick spacer layers. The interaction between excitons and plasmons is then directly prompted to strong coupling regime by shrinking down the thickness of spacer layer. Room temperature formation of polaritons with Rabi splitting up to 190 meV was observed, which is the largest plasmon-exciton Rabi splitting reported in two dimensional materials. Numerical calculations quantified the relation between coupling strength, local density of states and spacer thickness, and revealed the transition between weak coupling and strong coupling in nanocavities. The findings in this work offer a guideline for feasible designs of plasmon-exciton interaction systems with gap plasmonic cavities.",1904.10591v3 2018-10-26,Particle-number projected Bogoliubov coupled cluster theory. Application to the pairing Hamiltonian,"While coupled cluster theory accurately models weakly correlated quantum systems, it often fails in the presence of strong correlations where the standard mean-field picture is qualitatively incorrect. In many cases, these failures can be largely ameliorated by permitting the mean-field reference to break physical symmetries. Symmetry-broken coupled cluster, e.g. Bogoliubov coupled cluster, theory can indeed provide reasonably accurate energetic predictions, but the broken symmetry can compromise the quality of the resulting wave function and predictions of observables other than the energy. Merging symmetry projection and coupled cluster theory is therefore an appealing way to describe strongly correlated systems. Independently, two different but related formalisms have been recently proposed to achieve this goal. The two formalisms are contrasted in this manuscript, with results tested on the Richardson pairing Hamiltonian. Both formalisms are based on the disentangled cluster representation of the symmetry-rotated coupled cluster wavefunction. However, they differ in the way that the disentangled clusters are solved. One approach sets up angle-dependent coupled cluster equations, while the other involves first-order ordinary differential equations. The latter approach yields energies and occupation probabilities significantly better than those of number-projected BCS and BCS coupled cluster and, when the disentangled clusters are truncated at low excitation levels, has a computational cost not too much larger than that of BCS coupled cluster. The high quality of results presented in this manuscript indicates that symmetry-projected coupled cluster is a promising method that can accurately describe both weakly and strongly correlated finite many-fermion systems.",1810.11245v2 2018-10-31,Stability of synchronous slowly oscillating periodic solutions for systems of delay differential equations with coupled nonlinearity,"We study stability of so-called synchronous slowly oscillating periodic solutions (SOPSs) for a system of identical delay differential equations (DDEs) with linear decay and nonlinear delayed negative feedback that are coupled through their nonlinear term. Under a row sum condition on the coupling matrix, existence of a unique SOPS for the corresponding scalar DDE implies existence of a unique synchronous SOPS for the coupled DDEs. However, stability of the SOPS for the scalar DDE does not generally imply stability of the synchronous SOPS for the coupled DDEs. We obtain an explicit formula, depending only on the spectrum of the coupling matrix, the strength of the linear decay and the values of the nonlinear negative feedback function near plus/minus infinity, that determines the stability of the synchronous SOPS in the asymptotic regime where the nonlinear term is heavily weighted. We also treat the special cases of so-called weakly coupled systems, near uniformly coupled systems, and doubly nonnegative coupled systems, in the aforementioned asymptotic regime. Our approach is to estimate the characteristic (Floquet) multipliers for the synchronous SOPS. We first reduce the analysis of the multidimensional variational equation to the analysis of a family of scalar variational-type equations, and then establish limits for an associated family of monodromy-type operators. We illustrate our results with examples of systems of DDEs with mean-field coupling and systems of DDEs arranged in a ring.",1810.13398v3 2020-06-30,Nonclassicality of open circuit QED systems in the deep-strong coupling regime,"We investigate theoretically how the ground state of a qubit-resonator system in the deep-strong coupling (DSC) regime is affected by the coupling to an environment. We employ as a variational ansatz for the ground state of the qubit-resonator-environment system a superposition of coherent states displaced in qubit-state-dependent directions. We show that the reduced density matrix of the qubit-resonator system strongly depends on how the system is coupled to the environment, i.e., capacitive or inductive, because of the broken rotational symmetry of the eigenstates of the DSC system in the resonator phase space. When the resonator couples to the qubit and the environment in different ways (for instance, one is inductive and the other is capacitive), the system is almost unaffected by the resonator-waveguide coupling. In contrast, when the two couplings are of the same type (for instance, both are inductive), by increasing the resonator-waveguide coupling strength, the average number of virtual photons increases and the quantum superposition realized in the qubit-resonator entangled ground state is partially degraded. Since the superposition becomes more fragile with increasing the qubit-resonator coupling, there exists an optimal coupling strength to maximize the nonclassicality of the qubit-resonator system.",2006.16769v2 2015-07-30,Polarization of top quark as a probe of its chromomagnetic and chromoelectric couplings in $tW$ production at the Large Hadron Collider,"We study the sensitivity of the Large Hadron Collider (LHC) to top quark chromomagnetic (CMDM) and chromoelectric (CEDM) dipole moments and $Wtb$ effective couplings in single-top production in association with a $W^-$ boson, followed by semileptonic decay of the top. The $Wt$ single-top production mode helps to isolate the anomalous $ttg$ and $Wtb$ couplings, in contrast to top-pair production and other single-top production modes, where other new-physics effects can also contribute. We calculate the top polarization and the effects of these anomalous couplings on it at two centre-of-mass (cm) energies, 8 TeV and 14 TeV. As a measure of top polarization, we look at decay-lepton angular distributions in the laboratory frame, without requiring reconstruction of the rest frame of the top, and study the effect of the anomalous couplings on these distributions. We construct certain asymmetries to study the sensitivity of these distributions to top-quark couplings. We determine individual limits on the dominant couplings, viz., the real part of the CMDM $\mathrm{Re}\rho_2$, the imaginary part of the CEDM $\mathrm{Im}\rho_3$, and the real part of the tensor $Wtb$ coupling $\mathrm{Ref_{2R}}$, which may be obtained by utilizing these asymmetries at the LHC. We also obtain simultaneous limits on pairs of these couplings taking two couplings to be non-zero at a time.",1507.08385v2 2017-04-13,The effect of noise fluctuation of a quantum tunneling device coupled to a substrate,"The recent experiment of Stettenheim, et al. showed that, contrary to conventional belief, the coupling of a quantum electronic device to its substrate can have important effects on the noise power spectrum, since the substrate functions as a mechanical oscillator. We carry out a theoretical analysis of this coupling in the case of a quantum point contact (QPC). First we derive the noise power spectrum from the Hamiltonian without making the Markovian approximation, and obtain numerical results that reproduce the experimental data. Next we investigate the nature of the coupling. In most previous analyses, the coupling of an electronic device to a mechanical oscillator has been modeled as a position coupling. We model it both as a position coupling and as a momentum coupling and compare the results. We find that, as long as one includes backaction between position and momentum, the assumed mode of coupling makes little difference, since the backaction transmits momentum fluctuations to position fluctuations and vice versa. Finally, we ask whether the salient features of the model persist in the Markovian approximation. We find that a Markovian analysis confirms the QPC-substrate coupling, but underestimates the noise floor and leads to excessively sharp and narrow noise peaks around the resonant frequencies.",1704.04207v1 2018-01-20,"Generalized coupled mode formalism in reciprocal waveguides with gain/loss, anisotropy or bianisotropy","In anisotropic or bianisotropic waveguides, the standard coupled mode theory fails due to the broken link between the forward and backward propagating modes, which together form the dual mode sets that are crucial in constructing couple mode equations. We generalize the coupled mode theory by treating the forward and backward propagating modes on the same footing via a generalized eigenvalue problem that is exactly equivalent to the waveguide Hamiltonian. The generalized eigenvalue problem is fully characterized by two operators, i.e., $( \bar{\bm{L}},\bar{\bm{B}})$, wherein $\bar{\bm{L}}$ is a self-adjoint differential operator, while $\bar{\bm{B}}$ is a constant antisymmetric operator. From the properties of $\bar{\bm{L}}$ and $\bar{\bm{B}}$, we establish the relation between the dual mode sets that are essential in constructing coupled mode equations in terms of forward and backward propagating modes. By perturbation, the generalized coupled mode equation can be derived in a natural way. Our generalized coupled mode formalism can be used to study the mode coupling in waveguides that may contain gain/loss, anisotropy or bianisotropy. We further illustrate how the generalized coupled theory can be used to study the modal coupling in anisotropy and bianisotropy waveguides through a few concrete examples.",1801.06673v1 2019-06-28,Non-derivative Axionic Couplings to Nucleons at large and small N,"Among the possible CP-odd couplings of the axion to ordinary matter, the most relevant ones for phenomenology are the Yukawa couplings to nucleons. We analyze such non-derivative couplings within three different approaches: standard effective field theory, the Skyrme model and holographic QCD. In all the cases, the couplings can be related to the CP-odd non-derivative couplings to nucleons of the low-lying mesons and the $\eta'$. Using the effective field theory approach we discuss how to derive the expressions for the CP-odd interaction terms as functions of the parameters of the effective Lagrangian at generic number of colors $N_c$ and flavors $N_f$. Then, we compute the CP-odd couplings to nucleons of the axion, the $\eta'$ and the pseudo-Goldstone mesons in both the Skyrme and the holographic QCD model with $N_f=2,3$. We present model-independent expressions for the coefficients of the non-derivative axion-nucleon couplings. This allows us to provide quantitative estimates of these couplings.",1906.12132v3 2019-07-18,Measurements of capacitive coupling within a quadruple quantum dot array,"We present measurements of the capacitive coupling energy and the inter-dot capacitances in a linear quadruple quantum dot array in undoped Si/SiGe. With the device tuned to a regime of strong ($>$1 GHz) intra-double dot tunnel coupling, as is typical for double dot qubits, we measure a capacitive coupling energy of $20.9 \pm 0.3$ GHz. In this regime, we demonstrate a fitting procedure to extract all the parameters in the 4D Hamiltonian for two capacitively coupled charge qubits from a 2D slice through the quadruple dot charge stability diagram. We also investigate the tunability of the capacitive coupling energy, using inter-dot barrier gate voltages to tune the inter- and intra-double dot capacitances, and change the capacitive coupling energy of the double dots over a range of 15-32 GHz. We provide a model for the capacitive coupling energy based on the electrostatics of a network of charge nodes joined by capacitors, which shows how the coupling energy should depend on inter-double dot and intra-double dot capacitances in the network, and find that the expected trends agree well with the measurements of coupling energy.",1907.08216v1 2021-03-08,Anisotropic magnon-magnon coupling in synthetic antiferromagnets,"The magnon-magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies. To induce the magnon-magnon coupling, the parity symmetry between two magnetization needs to be broken. Here we experimentally demonstrate a convenient method to break the parity symmetry by the asymmetric thickness of two magnetic layers and thus introduce a magnon-magnon coupling in Ir-based synthetic antiferromagnets CoFeB(10 nm)/Ir(tIr=0.6 nm, 1.2 nm)/CoFeB(13 nm). Remarkably, we find that the weakly uniaxial anisotropy field (~ 20 Oe) makes the magnon-magnon coupling anisotropic. The coupling strength presented by a characteristic anticrossing gap varies in the range between 0.54 GHz and 0.90 GHz for tIr =0.6 nm, and between nearly zero to 1.4 GHz for tIr = 1.2 nm, respectively. Our results demonstrate a feasible way to induce the magnon-magnon coupling by an asymmetric structure and tune the coupling strength by varying the direction of in-plane magnetic field. The magnon-magnon coupling in this highly tunable material system could open exciting perspectives for exploring quantum-mechanical coupling phenomena.",2103.04512v2 2021-09-19,The Jet-Disk Coupling of Seyfert Galaxies from a Complete Hard X-ray Sample,"We analyze the jet-disk coupling for different subsamples from a complete hard X-ray Seyfert sample to study the coupling indices and their relation to accretion rate. The results are: (1) the power-law coupling index ranges from nearly unity (linear correlation) for radio-loud Seyferts to significantly less than unity for radio-quiet ones. This declining trend of coupling index also holds from larger sources to compact ones; (2) the Seyferts with intermediate to high accretion rate (Eddington ratio $\lambda\sim$ 0.001 to 0.3) show a linear jet-disk coupling, but it shallows from near to super Eddington ($\lambda\sim$ 0.3 to 10), and the former is more radio loud than the latter; (3) the Seyfert 1s are slightly steeper than the Seyfert 2s, in the jet-disk correlation. In the linear coupling regime, the ratio of jet efficiency to radiative efficiency ($\eta/\varepsilon$) is nearly invariant, but in low accretion or super accretion regime, $\eta/\varepsilon$ varies with $\lambda$ in our model. We note that a radio-active cycle of accretion-dominated active galactic nuclei would be: from a weaker jet-disk coupling in $\lambda<0.001$ for low luminosity Seyferts, to a linear coupling in $0.001<\lambda<0.3$ for radio-loud luminous Seyferts and powerful radio galaxies/quasars, and to a weaker coupling in $0.3<\lambda<10$ ones.",2109.09102v1 2021-10-19,An ultrastrongly coupled single THz meta-atom,"Free-space coupling to strongly subwavelength individual optical elements is a central theme in quantum optics, as it allows to control and manipulate the properties of quantum systems. In this work, we show that by combining an asymmetric immersion lens setup and complementary design of metasurfaces we are able to perform THz time-domain spectroscopy of an individual, strongly subwavelength (d/{\lambda}0=1/20) meta-atom. We unravel the linewidth dependence of planar metamaterials as a function of the meta-atom number indicating quenching of the Dicke superradiance. On these grounds, we investigate ultrastrongly coupled Landau polaritons at the single resonator level, measuring a normalized coupling ratio of {\Omega}/{\omega}=0.60 resulting from coupling of the fundamental mode to a few thousand electrons. Similar measurements on a low loss, less doped two dimensional electron gas yield a coupling ratio {\Omega}/{\omega}=0.33 with a cooperativity C=4g^2/{\kappa}{\gamma}= 94. Interestingly, the coupling strength of a coupled single resonator is the same as of a coupled array. Our findings pave the way towards the control of light-matter interaction in the ultrastrong coupling regime at the single electron/single resonator level. The proposed technique is way more general and can be useful to characterize the complex conductivity of micron-sized samples in the THz and sub-THz domain.",2110.09776v1 2022-02-27,Aging transition under discrete time-dependent coupling: Restoring rhythmicity from aging,"We explore the aging transition in a network of globally coupled Stuart-Landau oscillators under a discrete time-dependent coupling. In this coupling, the connections among the oscillators are turned ON and OFF in a systematic manner, having either a symmetric or an asymmetric time interval. We discover that depending upon the time period and duty cycle of the ON-OFF intervals, the aging region shrinks drastically in the parameter space, therefore promoting restoration of oscillatory dynamics from the aging. In the case of symmetric discrete coupling (where the ON-OFF intervals are equal), the aging zone decreases significantly with the resumption of dynamism with an increasing time period of the ON-OFF intervals. On the other hand, in the case of asymmetric coupling (where the ON-OFF intervals are not equal), we find that the ratio of the ON and OFF intervals controls the aging dynamics: the aging state is revoked more effectively if the interval of the OFF state is greater than the ON state. Finally, we study the transition in aging using a discrete pulse coupling: we note that the pulse interval plays a crucial role in determining the aging region. For all the cases of discrete time-dependent couplings, the aging regions are shrinking and the rhythmicity gets enhanced in a controlled manner. Our findings suggest that this type of coupling can act as a noninvasive way to restore the oscillatory dynamics from an aging state in a network of coupled oscillators.",2202.13334v1 2022-03-28,Optimal Coupling of Jumpy Brownian Motion on the Circle,"Consider a Brownian motion on the circumference of the unit circle, which jumps to the opposite point of the circumference at incident times of an independent Poisson process of rate $\lambda$. We examine the problem of coupling two copies of this `jumpy Brownian motion' started from different locations, so as to optimise certain functions of the coupling time. We describe two intuitive co-adapted couplings (`Mirror' and `Synchronous') which differ only when the two processes are directly opposite one another, and show that the question of which strategy is best depends upon the jump rate $\lambda$ in a non-trivial way. More precisely, we use the theory of stochastic control to show that there exists a critical value $\lambda^\star = 0.083\dots$ such that the Mirror coupling minimises the mean coupling time within the class of all co-adapted couplings when $\lambda<\lambda^\star$, but for $\lambda\ge \lambda^\star$ the Synchronous coupling uniquely maximises the Laplace transform $\mathbb{E}[e^{-\gamma T}]$ of all coupling times $T$ within this class. We also provide an explicit description of a (non co-adapted) maximal coupling for any jump rate in the case that the two jumpy Brownian motions begin at antipodal points of the circle.",2203.14791v2 2022-08-27,Optomechanical-interface-induced strong spin-magnon coupling,"Strong long-distance spin-magnon coupling is essential for solid-state quantum information processing and single qubit manipulation. Here, we propose an approach to realize strong spin-magnon coupling in a hybrid optomechanical cavity-spin-magnon system, where the optomechanical system, consisting of two cavities coupled to a common high-frequency mechanical resonator, acts as quantum interface. By eliminating the mechanical mode, a position-position coupling and two-mode squeezing of two cavities are induced. In the squeezing presentation, the spin-photon, magnon-photon and photon-photon coupling strengths are exponentially amplified, thus lower- and upper-branch polaritons (LBP and UBP) are generated by strongly coupled squeezed modes of two cavities. Utilizing the critical property of the LBP, the coupling between the spin qubit (magnon) and LBP is greatly enhanced, while the coupling between the spin qubit (magnon) and UBP is fully suppressed. In the dispersive regime, strong and tunable spin-magnon coupling is induced by the virtual LBP, allowing quantum state exchange between them. Our proposal provides a promising platform to construct magnon-based hybrid systems and realize solid-state quantum information processing with optomechanical interfaces.",2208.12988v3 2023-02-03,Regularized coupling multiscale method for thermomechanical coupled problems,"The coupling effects in multiphysics processes are often neglected in designing multiscale methods. The coupling may be described by a non-positive definite operator, which in turn brings significant challenges in multiscale simulations. In the paper, we develop a regularized coupling multiscale method based on the generalized multiscale finite element method (GMsFEM) to solve coupled thermomechanical problems, and it is referred to as the coupling generalized multiscale finite element method (CGMsFEM). The method consists of defining the coupling multiscale basis functions through local regularized coupling spectral problems in each coarse-grid block, which can be implemented by a novel design of two relaxation parameters. Compared to the standard GMsFEM, the proposed method can not only accurately capture the multiscale coupling correlation effects of multiphysics problems but also greatly improve computational efficiency with fewer multiscale basis functions. In addition, the convergence analysis is also established, and the optimal error estimates are derived, where the upper bound of errors is independent of the magnitude of the relaxation coefficient. Several numerical examples for periodic, random microstructure, and random material coefficients are presented to validate the theoretical analysis. The numerical results show that the CGMsFEM shows better robustness and efficiency than uncoupled GMsFEM.",2302.01674v2 2023-02-22,Synchronization approach to achieving maximum power and thermal efficiency for weakly-coupled low-temperature-differential Stirling engines,"Low-temperature-differential (LTD) Stirling engines are heat engines that can operate autonomously with a slight temperature difference between low-temperature heat reservoirs and are thus expected to contribute to a sustainable society. A minimal dynamical-system model with only two variables has been proposed to explain the principle of autonomous rotational motion caused by temperature differences, and the maximum efficiency of the engine was formulated [Y. Izumida, Europhys. Lett. 121, 50004 (2018); Phys. Rev. E 102, 012142 (2020)]. This paper aims to clarify the coupling effects on the dynamics, power, and thermal efficiency of a pair of weakly coupled LTD Stirling engines and formulate the maximum thermal efficiency of the coupled system in the quasilinear response regime. We show that the dependence relation between the effective frequency difference and the coupling strength is characterized by a hysteresis, which comes from different kinds of bifurcations in the process of increasing and decreasing the value of the coupling strength. Then, by generalizing thermodynamic fluxes and forces and their quasilinear relations for engines under weak coupling, we show that the coupling improves the power exerted against the load torques and the thermal efficiency. We further show that their maximum values are achieved when the engines are synchronized. Since the thermal efficiency depends on the frequency difference, the dependence of thermal efficiency on the coupling strength is also characterized by a hysteresis. Finally, the load torque that achieves the maximum thermal efficiency of the coupled system is formulated.",2302.11308v4 2023-05-05,Tilt-to-length coupling in LISA Pathfinder: analytical modelling,"Tilt-to-length coupling was the limiting noise source in LISA Pathfinder between 20 and 200 mHz before subtraction in post-processing. To prevent the adding of sensing noise to the data by the subtraction process, the success of this strategy depended on a previous direct noise reduction by test mass alignment. The exact dependency of the level of tilt-to-length coupling on the set-points of LISA Pathfinder's test masses was not understood until the end of the mission. Here, we present, for the first time, an analytical tilt-to-length coupling model that describes the coupling noise changes due to the realignments. We report on the different mechanisms, namely the lever arm and piston effect as well as the coupling due to transmissive components, and how they contribute to the full coupling. Further, we show that a pure geometric model would not have been sufficient to describe the coupling in LISA Pathfinder. Therefore, we model also the non-geometric tilt-to-length noise contributions. For the resulting coupling coefficients of the full model, we compute the expected error bars based on the known individual error sources. Also, we validated the analytical model against numerical simulations. A detailed study and thorough understanding of this noise are the basis for a successful analysis of the LISA Pathfinder data with respect to tilt-to-length coupling.",2305.03667v1 2023-08-16,Generation of two-giant-atom entanglement in waveguide-QED systems,"We study the generation of quantum entanglement between two giant atoms coupled to a one-dimensional waveguide. Since each giant atom interacts with the waveguide at two separate coupling points, there exist three different coupling configurations in the two-atom waveguide system: separated, braided, and nested couplings. Within the Wigner-Weisskopf framework for single coupling points, the quantum master equations governing the evolution of the two giant atoms are obtained. For each coupling configuration, the entanglement dynamics of the two giant atoms is studied, including the cases of two different atomic initial states: single- and double-excitation states. It is shown that the generated entanglement depends on the coupling configuration, phase shift, and atomic initial state. For the single-excitation initial state, there exists steady-state entanglement for these three couplings due to the appearance of the dark state. For the double-excitation initial state, an entanglement sudden birth is observed via adjusting the phase shift. In particular, the maximal entanglement for the nested coupling is about one order of magnitude larger than those of separate and braided couplings. In addition, the influence of the atomic frequency detuning on the entanglement generation is studied. This work can be utilized for the generation and control of atomic entanglement in quantum networks based on giant-atom waveguide-QED systems, which have wide potential applications in quantum information processing.",2308.08108v2 2023-10-03,Light polarons with electron-phonon coupling,"In most cases, as the strength of electron-phonon coupling increases, the effective mass of polarons typically increases. However, in this paper, we uncover a fascinating phenomenon: the presence of light polarons even within the strong coupling regime, where electron-phonon coupling includes both Holstein and bond types (electron-phonon coupling occurring on the hopping bonds). To investigate this, we employ a novel Diagrammatic Monte Carlo method based on the path-integral formulation of the particle sector and the Fock-state representation of the phonon sector. Our study centers on analyzing the impact of bond electron-phonon coupling on the Holstein polaron's essential properties, including its effective mass, ground state energy, and the average number of phonons. We examine two distinct scenarios: one where the phonon frequency of both Holstein and bond types is the same, and another where the phonon frequency of the Holstein type is twice as large as that of the bond type. In both of these two cases, when the Holstein coupling falls within the light mass regime, we observe minimal changes in the effective mass as a function of bond coupling, compared to the case of the bare bond polaron. However, the behavior of the effective mass undergoes a significant change in the heavy mass regime. Most intriguingly, we discover a non-monotonic dependence of the effective mass on the bond coupling $g_B$ when the Holstein coupling $g_H$ falls within the heavy mass regime. This finding holds promise, particularly in the context of bipolaron, where achieving a light effective mass and a large binding energy to get the compact size, is crucial.",2310.01958v1 2024-02-29,Coupling a single spin to high-frequency motion,"Coupling a single spin to high-frequency mechanical motion is a fundamental bottleneck of applications such as quantum sensing, intermediate and long-distance spin-spin coupling, and classical and quantum information processing. Previous experiments have only shown single spin coupling to low-frequency mechanical resonators, such as diamond cantilevers. High-frequency mechanical resonators, having the ability to access the quantum regime, open a range of possibilities when coupled to single spins, including readout and storage of quantum states. Here we report the first experimental demonstration of spin-mechanical coupling to a high-frequency resonator. We achieve this all-electrically on a fully suspended carbon nanotube device. A new mechanism gives rise to this coupling, which stems from spin-orbit coupling, and it is not mediated by strain. We observe both resonant and off-resonant coupling as a shift and broadening of the electric dipole spin resonance (EDSR), respectively. We develop a complete theoretical model taking into account the tensor form of the coupling and non-linearity in the motion. Our results propel spin-mechanical platforms to an uncharted regime. The interaction we reveal provides the full toolbox for promising applications ranging from the demonstration of macroscopic superpositions, to the operation of fully quantum engines, to quantum simulators.",2402.19288v1 2024-03-08,"Contact SHIV SoS or Contact ${\bf S}$tructure ${\bf H}$olographique at ${\bf I}$ntermediate coupling and bulk ${\bf V}$iscosity, and ${\bf S}$peed ${\bf o}$f ${\bf S}$ound","Thermal QCD systems like strongly coupled QGP require not only a large 't-Hooft coupling but also a finite gauge coupling arXiv:hep-ph/0701201. Unlike almost all top-down holographic models in the literature, holographic large-$N$ thermal QCD models based on this assumption, therefore necessarily require addressing this limit from ${\cal M}$ theory. In the context of strongly coupled (very large `t-Hooft coupling), bulk viscosity $\zeta$ of the type IIA-theory dual of thermal QCD-like theories was found to vary like $\frac{1}{3} - c_s^2$ arXiv:1807.04713 ($c_s$ being the speed of sound), and the same at weak coupling using kinetic theory and finite temperature field theory, was shown in arXiv:1807.04713 to vary like $\left(\frac{1}{3} - c_s^2\right)^2$. In this paper, we not only show that at intermediate coupling, $\zeta$ varies like a linear combination of the strong and weak coupling results, but also observe that this behavior is related to the existence of Contact 3-Structures that exists only at intermediate coupling effected by the intermediate-$N$ ""MQGP"" limit arXiv:2211.13186.",2403.10541v1 2010-09-02,Intercellular Coupling Regulates the Period of the Segmentation Clock,"Coupled biological oscillators can tick with the same period. How this collective period is established is a key question in understanding biological clocks. We explore this question in the segmentation clock, a population of coupled cellular oscillators in the vertebrate embryo that sets the rhythm of somitogenesis, the morphological segmentation of the body axis. The oscillating cells of the zebrafish segmentation clock are thought to possess noisy autonomous periods, which are synchronized by intercellular coupling through the Delta-Notch pathway. Here we ask whether Delta-Notch coupling additionally influences the collective period of the segmentation clock. Using multiple-embryo time-lapse microscopy, we show that disruption of Delta-Notch intercellular coupling increases the period of zebrafish somitogenesis. Embryonic segment length and the spatial wavelength of oscillating gene expression also increase correspondingly, indicating an increase in the segmentation clock's period. Using a theory based on phase oscillators in which the collective period self-organizes because of time delays in coupling, we estimate the cell-autonomous period, the coupling strength, and the coupling delay from our data. Further supporting the role of coupling delays in the clock, we predict and experimentally confirm an instability resulting from decreased coupling delay time. Synchronization of cells by Delta-Notch coupling regulates the collective period of the segmentation clock. Our identification of the first segmentation clock period mutants is a critical step toward a molecular understanding of temporal control in this system. We propose that collective control of period via delayed coupling may be a general feature of biological clocks.",1009.0456v1 2012-10-26,Shy and Fixed-Distance Couplings of Brownian Motions on Manifolds,"In this paper we introduce three Markovian couplings of Brownian motions on smooth Riemannian manifolds without boundary which sit at the crossroad of two concepts. The first concept is the one of shy coupling put forward in \cite{Burdzy-Benjamini} and the second concept is the lower bound on the Ricci curvature and the connection with couplings made in \cite{ReSt}. The first construction is the shy coupling, the second one is a fixed-distance coupling and the third is a coupling in which the distance between the processes is a deterministic exponential function of time. The result proved here is that an arbitrary Riemannian manifold satisfying some technical conditions supports shy couplings. If in addition, the Ricci curvature is non-negative, there exist fixed-distance couplings. Furthermore, if the Ricci curvature is bounded below by a positive constant, then there exists a coupling of Brownian motions for which the distance between the processes is a decreasing exponential function of time. The constructions use the intrinsic geometry, and relies on an extension of the notion of frames which plays an important role for even dimensional manifolds. In fact, we provide a wider class of couplings in which the distance function is deterministic in Theorem \ref{t:100} and Corollary~\ref{Cor:9}. As an application of the fixed-distance coupling we derive a maximum principle for the gradient of harmonic functions on manifolds with non-negative Ricci curvature. As far as we are aware of, these constructions are new, though the existence of shy couplings on manifolds is suggested by Kendall in \cite{Kendall}.",1210.7217v7 2016-05-07,From strong to weak coupling in holographic models of thermalization,"We investigate the analytic structure of thermal energy-momentum tensor correlators at large but finite coupling in quantum field theories with gravity duals. We compute corrections to the quasinormal spectra of black branes due to the presence of higher derivative $R^2$ and $R^4$ terms in the action, focusing on the dual to $\mathcal{N}=4$ SYM theory and Gauss-Bonnet gravity. We observe the appearance of new poles in the complex frequency plane at finite coupling. The new poles interfere with hydrodynamic poles of the correlators leading to the breakdown of hydrodynamic description at a coupling-dependent critical value of the wave-vector. The dependence of the critical wave vector on the coupling implies that the range of validity of the hydrodynamic description increases monotonically with the coupling. The behavior of the quasinormal spectrum at large but finite coupling may be contrasted with the known properties of the hierarchy of relaxation times determined by the spectrum of a linearized kinetic operator at weak coupling. We find that the ratio of a transport coefficient such as viscosity to the relaxation time determined by the fundamental non-hydrodynamic quasinormal frequency changes rapidly in the vicinity of infinite coupling but flattens out for weaker coupling, suggesting an extrapolation from strong coupling to the kinetic theory result. We note that the behavior of the quasinormal spectrum is qualitatively different depending on whether the ratio of shear viscosity to entropy density is greater or less than the universal, infinite coupling value of $\hbar/4\pi k_B$. In the former case, the density of poles increases, indicating a formation of branch cuts in the weak coupling limit, and the spectral function shows the appearance of narrow peaks. We also discuss the relation of the viscosity-entropy ratio to conjectured bounds on relaxation time in quantum systems.",1605.02173v2 2017-07-16,Chimera states in two-dimensional networks of locally coupled oscillators,"Chimera state is defined as a mixed type of collective state in which synchronized and desynchronized subpopulations of a network of coupled oscillators coexist and the appearance of such anomalous behavior has strong connection to diverse neuronal developments. Most of the previous studies on chimera states are not extensively done in two-dimensional ensembles of coupled oscillators by taking neuronal systems with nonlinear coupling function into account while such ensembles of oscillators are more realistic from a neurobiological point of view. In this paper, we report the emergence and existence of chimera states by considering locally coupled two-dimensional networks of identical oscillators where each node is interacting through nonlinear coupling function. This is in contrast with the existence of chimera states in two-dimensional nonlocally coupled oscillators with rectangular kernel in the coupling function. We find that the presence of nonlinearity in the coupling function plays a key role to produce chimera states in two-dimensional locally coupled oscillators. We analytically verify explicitly in the case of a network of coupled Stuart - Landau oscillators in two dimensions that the obtained results using Ott-Antonsen approach and our analytical finding very well matches with the numerical results. Next, we consider another type of important nonlinear coupling function which exists in neuronal systems, namely chemical synaptic function, through which the nearest-neighbor (locally coupled) neurons interact with each other. In numerical simulations, we consider two paradigmatic neuronal oscillators, namely Hindmarsh-Rose neuron model and Rulkov map for each node which exhibit bursting dynamics. The existence of chimera states is confirmed by instantaneous angular frequency, order parameter and strength of incoherence.",1707.08443v2 2021-09-01,Influence of Rashba spin-orbit and Rabi couplings on the miscibility and ground state phases of binary Bose-Einstein condensates,"We study the miscibility properties and ground state phases of two-component spin-orbit (SO) coupled Bose-Einstein condensates (BECs) in a harmonic trap with strong axial confinement. By numerically solving the coupled Gross-Pitaevskii equations in the two-dimensional setting, we analyze the SO-coupled BECs for two possible permutations of the intra- and interspecies interactions, namely (i) weak intra- and weak interspecies interactions (W-W) and (ii) weak intra- and strong interspecies interactions (W-S). Considering the density overlap integral as a miscibility order parameter, we investigate the miscible-immiscible transition by varying the coupling parameters. We obtain various ground state phases, including plane wave, half quantum vortex, elongated plane wave, and different stripe wave patterns for W-W interactions. For finite Rabi coupling, an increase in SO coupling strength leads to the transition from the fully miscible to the partially miscible state. We also characterize different ground states in the coupling parameter space using the root mean square sizes of the condensate. The spin density vector for the ground state phases exhibits density, quadrupole and dipole like spin polarizations. For the W-S interaction, in addition to that observed in the W-W case, we witness semi vortex, mixed mode, and shell-like immiscible phases. We notice a wide variety of spin polarizations, such as density, dipole, quadrupole, symbiotic, necklace, and stripe-like patterns for the W-S case. A detailed investigation in the coupling parameter space indicates immiscible to miscible state phase transition upon varying the Rabi coupling for a fixed Rashba SO coupling. The critical Rabi coupling for the immiscible-miscible phase transition decreases upon increasing the SO coupling strength.",2109.00491v1 2021-10-04,Influence of Allee Effect on Extreme Events in Coupled Three Species Systems,"We consider the dynamics of two coupled three-species population patches, incorporating the Allee Effect, focussing on the onset of extreme events in the coupled system. First we show that the interplay between coupling and the Allee effect may change the nature of the dynamics, with regular periodic dynamics becoming chaotic in a range of Allee parameters and coupling strengths. Further, the growth in the vegetation population displays an explosive blow-up beyond a critical value of coupling strength and Allee parameter. Most interestingly, we observe that beyond a threshold of coupling strength and Allee parameter, the population densities of all three species exhibit non-zero probability of yielding extreme events. The emergence of extreme events in the predator populations in the patches is the most prevalent, and the probability of obtaining large deviations in the predator populations is not affected significantly by either the coupling strength or the Allee effect. In the absence of the Allee effect the prey population in the coupled system exhibits no extreme events for low coupling strengths, but yields a sharp increase in extreme events after a critical strength of coupling. The vegetation population in the patches display a small finite probability of extreme events for strong enough coupling, only in the presence of Allee effect. Lastly we consider the influence of additive noise on the continued prevalence of extreme events. Very significantly, we find that noise suppresses the unbounded vegetation growth that was induced by a combination of Allee effect and coupling. Further, we demonstrate that noise mitigates extreme events in all three populations, and beyond a noise level we do not observe any extreme events in the system at all. This finding has important bearing on the potential observability of extreme events in natural and laboratory systems.",2110.01192v1 1996-03-12,On the Problem of the Coupled Cavity Chain Characteristic Calculations,"This paper presents the results of studies in elaboration of a mathematical model of the cavity-chain slow wave structures. Considered is the problem of coupling of an infinitely long cylindrical cavity chain coupled through centerholes in the dividing walls of finite thickness without the assumption about smallness of any parameters. On the basis of a rigorous electrodynamic approach it is shown that the cavity chain can be described by a set of equations that describe the coupling of an infinite number of similar-type modes of short-circuit cavities. At the same time the coupling coefficients are determined by solving the basic sets of linear algebraic equations which describe the coupling the tangential electric fields on the right and left cylindrical hole cross-sections of the disks. The results are given of numerical simulations of the dependence of electrodynamic characteristics on the number of connections between the modes taken into account. Based on these calculations for different cavity dimensions, the number of coupling connections that give the sufficient accuracy of the description was determined.",9603001v1 2001-06-13,Cosmological magnetic fields from photon coupling to fermions and bosons in inflation,"We consider several gauge invariant higher dimensional operators that couple gravity, gauge fields and scalar or fermionic fields and thus break conformal invariance. In particular, we consider terms that break conformal invariance by the photon coupling to heavy and light fermions. While the coupling to heavy fermions typically do not induce significant magnetic fields, the coupling to light fermions may produce observable magnetic fields when there are a few hundred light fermions. Next we consider Planck scale modifications of the kinetic gauge terms of the form f(phi) F_{mu nu} F^{mu nu} and h(psi) F_{mu nu} \~F^{mu nu}, where f and h are functions of scalar and pseudoscalar fields phi, psi, and F_{mu nu}, ~F^{mu nu} are the gauge field strength and its dual, respectively. For a suitable choice of f sufficiently strong magnetic fields may be produced in inflation to be potentially observable today. The pseudoscalar coupling may lead to birefringence in inflation, but no observable magnetic field amplification. Finally, we show that the photon coupling to metric perturbations produces by far too weak fields to be of cosmological interest.",0106247v1 2003-06-13,Gauge Coupling Variation in Brane Models,"We consider the space-time variation of gauge couplings in brane-world models induced by the coupling to a bulk scalar field. A variation is generated by the running of the gauge couplings with energy and a conformal anomaly while going from the Jordan to the Einstein frame. We indicate that the one-loop corrections cancel implying that one obtains a variation of the fine structure constant by either directly coupling the gauge fields to the bulk scalar field or having bulk scalar field dependent Yukawa couplings. Taking into account the cosmological dynamics of the bulk scalar field, we constrain the strength of the gauge coupling dependence on the bulk scalar field and relate it to modifications of gravity at low energy.",0306279v2 2006-12-22,Cosmologies with dynamical and coupled Dark Energy vs. CMB data,"We compare a large set of cosmologies with WMAP data, performing a fit based on a MCMC algorithm. Besides of LCDM models, we take dynamical DE models, where DE and DM are uncoupled or coupled, both in the case of constant coupling and in the case when coupling varies with suitable laws. DE however arises from a scalar field self-interacting through a SUGRA potential. We find that the best fitting model is SUGRA dynamical DE, almost indipendently from the exponent alpha in the self-interaction potential. The main target of this work are however coupled DE models, for which we find limits on the DE-DM coupling strength. In the case of variable coupling, we also find that greater values of the Hubble constant are preferred.",0612672v1 1992-09-08,A Simple Model for Coupled Magnetic and Quadrupolar Instabilities in Uranium Heavy-Fermion Materials,"We present a mean-field calculation of the phase diagram of a simple model of localized moments, in the hexagonal uranium heavy-fermion compounds. The model considers a non-Kramers quadrupolar doublet ground state magnetically coupled with a singlet excited-state, favoring in-plane van-Vleck magnetism, as has been conjectured for UPt$_3$. The Hamiltonian which defines the model is Heisenberg like in both, magnetic and quadrupolar moments. Among our main results are: (i) for zero intersite quadrupolar coupling, the magnetic order is achieved by a first order transition above a critical intersite magnetic coupling value which becomes second order at higher coupling strengths. (ii) for finite intersite quadrupolar coupling, at temperatures below a second order quadrupolar ordering transition, the minimal magnetic coupling value is increased but (a) the magnetic ordering temperature is enhanced above this value, and (b) the ordering of first and second order transitions in the phase diagram is reversed.",9209008v1 1996-09-13,Renormalization of Fluctuating Tilted-Hexatic Membranes,"We consider the tilted-hexatic Hamiltonian on the fluctuating membranes. A renormalization-group analysis leads us to find two critical regions; one corresponds to the strong coupling regime of the gradient cross coupling, the other to the weak coupling regime. In the strong coupling regime, we find the locked tilted-hexatic to liquid phase transition when disclinations and vortices unbind simultaneously. On the other hand, in the weak coupling regime we find four phases; the unlocked tilted-hexatic phase, the hexatic phase, the tilted phase, and liquid phase. Disclinations and vortices unbind independently. The crinkled-to-crumpled transition of the fluctuating tilted-hexatic membranes is also described. The crinkled phase in the strong coupling regime is stiffer than that in the weak coupling regime.",9609125v2 1996-12-11,Competition between Hund-Rule Coupling and Kondo Effect,"We investigate a problem about the competition between the hybridization and the Hund-rule coupling by applying the Wilson numerical renormalization-group method to the extended Kondo model where the impurity spin interacts via the Hund-rule coupling, with an extra spin which is isolated from the conduction electrons. It is shown that the Hund-rule coupling is an irrelevant perturbation against the strong coupling fixed point. However, the Hund-rule coupling decreases the characteristic energy $T_K$ drastically to the lower side and the irrelevant operator, which describes the low energy physics, takes a form of ferromagnetic exchange interaction between the extra spin and the Kondo resonance states because of the existence of the Hund-rule coupling.",9612108v1 2000-03-20,Metal-insulator transitions in systems with electron-phonon and Coulomb interactions,"We consider a model which includes the electron-phonon coupling to Ag or Jahn-Teller Hg phonons, the Coulomb interaction U and an exchange integral K. We study the metal-insulator transition for the integer fillings n=3 and 4. We find that the coupling to Ag phonons increases the critical value Uc where the transition takes place, while the coupling to Hg phonons decreases Uc. Without electron-phonon coupling the Hund's rule coupling also decreases Uc. There is, however, an interesting competition between the Hund's rule coupling and the Jahn-Teller effect. Thus the reduction of Uc due to the Hg phonons becomes smaller when the Hund's rule coupling is turned on. The implications of this is discussed in the context of AnC60.",0003335v1 2000-04-16,Thermodynamic Properties of Three-Dimensional Orthogonal Dimer Model for SrCu$_2$(BO$_3$)$_2$,"Effects of the inter-layer couplings for the orthogonal dimer system SrCu$_2$(BO$_3$)$_2$ are discussed. The spin-gap $\Delta$ of the three-dimensional model is independent of the inter-layer couplings when they are small. Therefore at low temperatures ($T < \Delta$) thermodynamic properties are described well by the two-dimensional model. On the other hand at high temperatures the mean-field type scaling ansatz is useful to discuss the magnetic susceptibility for week inter-layer couplings. From fit of the magnetic susceptibility, the estimated coupling constants are J = 85 K for the nearest-neighbor couplings, $J^{'} = 54$ K for the next-nearest-neighbor couplings, and $J^{''} = 8$ K for the inter-layer couplings. These parameters are consistent with the temperature dependence of the specific heat at low temperatures.",0004260v1 2001-02-26,"Electronic properties of single and coupled anisotropic quantum dots in a magnetic field, spin interactions and switching","We determined the eigenstates of a single electron in a parabolic anisotropic 2D quantum dot in a magnetic field. Using obtained expressions for these eigenstates, we study the spin coupling J between two electrons located in two laterally coupled anisotropic quantum dots (QD). The exhange coupling J is calculated using the Heitler-London and Hund-Mulliken approaches. We found that the exhange J changes sign at certain values of parameters of the system, in particular at certain anisotropy of the QD. Therefore, we present a new method to switch on and off the spin coupling between QD: switching by means of changing shape of the QD. Switching the spin coupling is essential for quantum computation using electronic spins as qubits. We note that our calculations can be applied to the system of vertically coupled QD as well.",0102467v1 2002-02-06,Pseudogap and spectral function from superconducting fluctuations to the bosonic limit,"The crossover from weak to strong coupling for a three dimensional continuum model of fermions interacting via an attractive contact potential is studied above the superconducting critical temperature. The pair-fluctuation propagator, the one-loop self-energy, and the spectral function are investigated in a systematic way from the superconducting fluctuation regime (weak coupling) to the bosonic regime (strong coupling). Analytic and numerical results are reported. In the strong-coupling regime, where the pair fluctuation propagator has bosonic character, two quite different peaks appear in the spectral function, a broad one at negative frequencies and a narrow one at positive frequencies. By decreasing coupling, the two-peak structure evolves smoothly. In the weak-coupling regime, where the fluctuation propagator has diffusive Ginzburg-Landau character, the overall line-shape of the spectral function is more symmetric. The systematic analysis of the spectral function identifies specific features which allow one to distinguish by ARPES whether a system is in the weak- or strong-coupling regime. Connection of the results of our analysis with the phenomenology of cuprate superconductors is also attempted and rests on the recently introduced two-gap model.",0202084v1 2003-07-23,Dynamic Magnetoelectric Effects in Bulk and Layered composites of Cobalt Zinc Ferrite and Lead Zirconate Titanate,"Low frequency magnetoelectric (ME) coupling has been investigated in bulk and multilayers of cobalt zinc ferrite, Co1-xZnxFe2O4 (x=0-0.6), and lead zirconate titanate. In bulk samples, the transverse and longitudinal couplings are weak and are of equal magnitude. A substantial strengthening of ME interactions is evident in layered structures, with the ME voltage coefficient a factor of 10-30 higher than in bulk samples. Important findings of the studies in layered composites are as follows. (i) The transverse coupling is stronger than the longitudinal coupling. (ii) The strength of ME interactions is dependent on Zn substitution with a maximum for x=0.4. (iii) Analysis of volume and static magnetic field dependence of ME voltage coefficients reveal a weak coupling at the ferromagnetic-piezoelectric interface. (iv) The interface coupling k increases with Zn substitution and k versus x profile shows a maximum centered at x=0.4. (iv) The Zn-assisted enhancement is attributed to efficient magneto-mechanical coupling in the ferrite.",0307597v1 2003-09-22,Fast two-bit operations in inductively coupled flux qubits,"A central problem for implementing efficient quantum computing is how to realize fast operations (both one- and two-bit ones). However, this is difficult to achieve for a collection of qubits, especially for those separated far away, because the interbit coupling is usually much weaker than the intrabit coupling. Here we present an experimentally feasible method to effectively couple two flux qubits via a common inductance and treat both single and coupled flux qubits with more realistic models which include the loop inductance. The main advantage of our proposal is that a strong interbit coupling can be achieved using a small inductance, so that two-bit operations as fast as one-bit ones can be easily realized. We also show the flux dependence of the transitions between states for the coupled flux qubits.",0309491v3 2004-01-12,The Effects of the interfacial Pseudo-spin Coupling Fluctuation on the Dielectric Property of a Ferroelectric Superlattice,"Using effective-field theory with correlations, we investigate the effects of interfacial pseudo-spin coupling fluctuations on the susceptibility and polarization of ferroelectric superlattices within the framework of transverse Ising model. It is found that the interfacial coupling fluctuations increase the susceptibility in the low temperature region. For a strong interfacial coupling, the phase transition temperature decreases with the strength of fluctuations of the interfacial coupling. The dependence of the susceptibility on the superlattice period of $BaTiO_{3}/SrTiO_{3}$ are plotted for different interfacial coupling fluctuations strength. At room temperature, when the interfacial coupling fluctuation increases, the peak position of the susceptibility will shift to a large superlattice period.",0401168v3 2004-08-26,Collective synchronization in spatially extended systems of coupled oscillators with random frequencies,"We study collective behavior of locally coupled limit-cycle oscillators with random intrinsic frequencies, spatially extended over $d$-dimensional hypercubic lattices. Phase synchronization as well as frequency entrainment are explored analytically in the linear (strong-coupling) regime and numerically in the nonlinear (weak-coupling) regime. Our analysis shows that the oscillator phases are always desynchronized up to $d=4$, which implies the lower critical dimension $d_{l}^{P}=4$ for phase synchronization. On the other hand, the oscillators behave collectively in frequency (phase velocity) even in three dimensions ($d=3$), indicating that the lower critical dimension for frequency entrainment is $d_{l}^{F}=2$. Nonlinear effects due to periodic nature of limit-cycle oscillators are found to become significant in the weak-coupling regime: So-called {\em runaway oscillators} destroy the synchronized (ordered) phase and there emerges a fully random (disordered) phase. Critical behavior near the synchronization transition into the fully random phase is unveiled via numerical investigation. Collective behavior of globally-coupled oscillators is also examined and compared with that of locally coupled oscillators.",0408553v1 2004-10-11,Dispersion of incoherent spectral features in systems with strong electron-phonon coupling,"We study (inverse) photoemission from systems with strong coupling of doped carriers to phonons. Using an adiabatic approximation, we develop a method for calculating spectra. This method is particularly simple for systems where the electron-phonon coupling can be neglected in the initial state, e.g., the undoped t-J model. The theory then naturally explains why the electron-phonon coupling just leads to a broadening of spectra calculated without electron-phonon coupling, without changing the dispersion. This is in agreement with recent angle-resolved photoemission spectroscopy (ARPES) on undoped cuprates, and it supports the interpretation in terms of strong electron-phonon interaction. The theory also shows that for systems with strong electron-phonon coupling in the initial state, the result cannot in general be related to the spectrum obtained without electron-phonon coupling.",0410247v1 2005-01-05,Direct Josephson coupling between superconducting flux qubits,"We have demonstrated strong antiferromagnetic coupling between two three-junction flux qubits based on a shared Josephson junction, and therefore not limited by the small inductances of the qubit loops. The coupling sign and magnitude were measured by coupling the system to a high-quality superconducting tank circuit. Design modifications allowing to continuously tune the coupling strength and/or make the coupling ferromagnetic are discussed.",0501085v2 2005-03-23,Indirect exchange coupling between magnetic adatoms in carbon nanotubes,"The long range character of the exchange coupling between localized magnetic moments indirectly mediated by the conduction electrons of metallic hosts can play a significant role in determining the magnetic order of low-dimensional structures. Here we consider how this indirect coupling influences the magnetic alignment of adatoms attached to the walls of carbon nanotubes. A general expression for the indirect coupling in terms of single-particle Green functions is presented. Contrary to the general property that magnetic moments embedded in a metal display Friedel-like oscillations in their magnetic response, calculated values for the coupling across metallic zigzag nanotubes show monotonic behaviour as a function of the adatom separation. Rather than an intrinsic property, the monotonicity is shown to reflect a commensurability effect in which the coupling oscillates with periods that coincide with the lattice parameter of the nanotube host. Such a commensurability effect does not dominate the coupling across semiconducting zigzag or metallic armchair nanotubes. We argue that such a long-range character in the magnetic interaction can be used in future spintronic devices.",0503589v1 2005-05-23,Synchronizations in small-world networks of spiking neurons: Diffusive versus sigmoid couplings,"By using a semi-analytical dynamical mean-field approximation previously proposed by the author [H. Hasegawa, Phys. Rev. E, {\bf 70}, 066107 (2004)], we have studied the synchronization of stochastic, small-world (SW) networks of FitzHugh-Nagumo neurons with diffusive couplings. The difference and similarity between results for {\it diffusive} and {\it sigmoid} couplings have been discussed. It has been shown that with introducing the weak heterogeneity to regular networks, the synchronization may be slightly increased for diffusive couplings, while it is decreased for sigmoid couplings. This increase in the synchronization for diffusive couplings is shown to be due to their local, negative feedback contributions, but not due to the shorten average distance in SW networks. Synchronization of SW networks depends not only on their structure but also on the type of couplings.",0505543v3 2005-12-28,Decoherence dynamics of a qubit coupled to a quantum two-level system,"We study the decoherence dynamics of a qubit coupled to a quantum two-level system (TLS) in addition to its weak coupling to a background environment. We analyze the different regimes of behaviour that arise as the values of the different parameters are varied. We classify those regimes as two weak-coupling regimes, which differ by the relation between the qubit and TLS decoherence times, and a strong-coupling one. We also find analytic expressions describing the decoherence rates in the weak-coupling regimes, and we verify numerically that those expressions have a rather wide range of validity. Along with obtaining the above-mentioned results, we address the questions of qubit-TLS entanglement and the additivity of multiple TLS contributions. We also discuss the transition from weak to strong coupling as the parameters are varied, and we numerically determine the location of the boundary between the two regimes.",0512677v3 2006-01-17,Spin Hot Spots in vertically-coupled Few-electron Quantum Dots,"The effects of spin-orbit (SO) coupling arising from the confinement potential in single and two vertically-coupled quantum dots have been investigated. Our work indicates that a dot containing a single electron shows the lifting of the degeneracy of dipole-allowed transitions at B=0 due to the SO coupling which disappears for a dot containing two electrons. For coupled dots with one electron in each dot, the optical spectra is not affected by the coupling and is the same as the dot containing one electron. However, for the case of two coupled dots where one partner dot has two interacting electrons while the other dot has only one electron, a remarkable effect is observed where the oscillator strength of two out of four dipole-allowed transition lines disappears as the distance between the dots is decreased.",0601390v1 2006-04-25,Public-channel cryptography based on mutual chaos pass filters,"We study the mutual coupling of chaotic lasers and observe both experimentally and in numeric simulations, that there exists a regime of parameters for which two mutually coupled chaotic lasers establish isochronal synchronization, while a third laser coupled unidirectionally to one of the pair, does not synchronize. We then propose a cryptographic scheme, based on the advantage of mutual-coupling over unidirectional coupling, where all the parameters of the system are public knowledge. We numerically demonstrate that in such a scheme the two communicating lasers can add a message signal (compressed binary message) to the transmitted coupling signal, and recover the message in both directions with high fidelity by using a mutual chaos pass filter procedure. An attacker however, fails to recover an errorless message even if he amplifies the coupling signal.",0604569v1 2006-11-19,Magnetic coupling in CoCr_2O_4 and MnCr_2O_4: an LSDA+U study,"We present a first principles LSDA+U study of the magnetic coupling constants in the spinel magnets CoCr_2O_4 and MnCr_2O_4. Our calculated coupling constants highlight the possible importance of AA interactions in spinel systems with magnetic ions on both A and B sites. Furthermore, we show that a careful analysis of the dependence of the magnetic coupling constants on the LSDA+U parameters provides valuable insights in the underlying coupling mechanisms, and allows to obtain a quantitative estimate of the magnetic coupling constants. We discuss in detail the capabilities and possible pitfalls of the LSDA+U method in determining magnetic coupling constants in complex transition metal oxides.",0611502v3 2006-06-26,Coupled quintessence and curvature-assisted acceleration,"Spatially homogeneous models with a scalar field non-minimally coupled to the space-time curvature or to the ordinary matter content are analysed with respect to late-time asymptotic behaviour, in particular to accelerated expansion and isotropization. It is found that a direct coupling to the curvature leads to asymptotic de Sitter expansion in arbitrary exponential potentials, thus yielding a positive cosmological constant although none is apparent in the potential. This holds true regardless of the steepness of the potential or the smallness of the coupling constant. For matter-coupled scalar fields, the asymptotics are obtained for a large class of positive potentials, generalizing the well-known cosmic no-hair theorems for minimal coupling. In this case it is observed that the direct coupling to matter does not impact the late-time dynamics essentially.",0606113v2 2001-04-18,Measurement of Triple Gauge-Boson Couplings at LEP up to 189GeV,"The triple gauge-boson couplings involving the W are determined using data samples collected with the ALEPH detector at mean centre-of-mass energies of 183 GeV and 189 GeV, corresponding to integrated luminosities of 57 pb^-1 and 174 pb^-1, respectively. The couplings, g^Z_1, Kappa_gamma and lambda_gamma, are measured using W-pair events, single-W production and single-gamma production. Each coupling is measured individually with the other two coupling fixed at their Standard Model value. Including ALEPH results from lower energies, the 95% confidence level intervals for the deviation to the Standard Model are -0.087 < Dg^Z_1 < 0.141 -0.200 < DKappa_gamma < 0.258 -0.062 < Lambda_gamma < 0.147. Fits are also presented where two or all three couplings are allowed to vary. In addition, W-pair events are used to set limits on the C- or P-violating couplings g^V_4, g^V_5, Kappa_V, and Lambda_V, where V denotes either gamma or Z. No deviations from the Standard Model expectations are observed.",0104034v1 2003-08-27,Measurement of charged current triple gauge boson couplings using W pairs at LEP,"Triple gauge boson couplings are measured from W-pair and single photon events recorded by the OPAL detector at LEP at center-of-mass energies between 183 - 209 GeV with a total integrated luminosity of 680 inverse picobarns. Only CP-conserving couplings are considered and SU(2)xU(1) relations between the WWZ and the WWgamma couolings are used, resulting in four independent couplings. Each coupling is determined in a separate fit, assuming the other couplings to take their Standard Model values. Fits are also done allowing some of the couplings to vary simultaneously. The results are compared with the Standard Model predictions.",0308067v1 2005-11-20,Running couplings in equivariantly gauge-fixed SU(N) Yang--Mills theories,"In equivariantly gauge-fixed SU(N) Yang--Mills theories, the gauge symmetry is only partially fixed, leaving a subgroup $H\subset SU(N)$ unfixed. Such theories avoid Neuberger's nogo theorem if the subgroup $H$ contains at least the Cartan subgroup $U(1)^{N-1}$, and they are thus non-perturbatively well defined if regulated on a finite lattice. We calculate the one-loop beta function for the coupling $\tilde{g}^2=\xi g^2$, where $g$ is the gauge coupling and $\xi$ is the gauge parameter, for a class of subgroups including the cases that $H=U(1)^{N-1}$ or $H=SU(M)\times SU(N-M)\times U(1)$. The coupling $\tilde{g}$ represents the strength of the interaction of the gauge degrees of freedom associated with the coset $SU(N)/H$. We find that $\tilde{g}$, like $g$, is asymptotically free. We solve the renormalization-group equations for the running of the couplings $g$ and $\tilde{g}$, and find that dimensional transmutation takes place also for the coupling $\tilde{g}$, generating a scale $\tilde{\Lambda}$ which can be larger than or equal to the scale $\Lambda$ associated with the gauge coupling $g$, but not smaller. We speculate on the possible implications of these results.",0511042v1 1993-12-07,How Big Can Anomalous W Couplings Be?,"Conventional wisdom has it that anomalous gauge-boson self-couplings can be at most a percent or so in size. We test this wisdom by computing these couplings at one loop in a generic renormalizable model of new physics. (For technical reasons we consider the CP-violating couplings here, but our results apply more generally.) By surveying the parameter space we find that the largest couplings (several percent) are obtained when the new particles are at the weak scale. For heavy new physics we compare our findings with expectations based on an effective-lagrangian analysis. We find general patterns of induced couplings which robustly reflect the nature of the underlying physics. We build representative models for which the new physics could be first detected in the anomalous gauge couplings.",9312238v2 1994-02-18,Effects of technicolor on standard model running couplings,"We discuss the running couplings in the standard model, SU(3$)_C \times $SU(2$)_L \times $U(1$)_Y$, when the Higgs sector is replaced by SU($N_{TC})$ technicolor. Particular attention is given to the running of the couplings at momentum scales where technicolor is nonperturbative, and in this region we apply a relativistic constituent technifermion model. This model has been tested against the known running of the QED coupling due to nonperturbative QCD. An understanding of this low momentum running allows the calculation of the couplings at a higher scale, $\Lambda_{pert}$, where technicolor becomes perturbative. We provide numerical values for the changes in the three standard model couplings between $m_Z$ and $\Lambda_{pert}$ due to technicolor, assuming separately ``one doublet'' and ``one family'' technicolor models. The distinction between a running and walking technicolor coupling is also considered.",9402319v1 1997-07-25,Strong Unification,"We investigate the possibility that unification occurs at strong coupling. We show that, despite the fact the couplings pass through a strong coupling regime, accurate predictions for their low energy values are possible because the couplings of the theory flow to infrared fixed points. We determine the low-energy QCD coupling in a favoured class of strong coupling models and find it is reduced from the weak coupling predictions, lying close to the experimentally measured value. We extend the analysis to the determination of quark and lepton masses and show that (even without Grand Unification) the infra-red fixed point structure may lead to good predictions for the top mass, the bottom to tau mass ratio and $\tan \beta $. Finally we discuss the implications for the unification scale finding it to be increased from the MSSM value and closer to the heterotic string prediction.",9707462v2 1999-02-19,Infra-red stable fixed points of R-parity violating Yukawa couplings in supersymmetric models,"We investigate the infra-red stable fixed points of the Yukawa couplings in the minimal version of the supersymmetric standard model with R-parity violation. Retaining only the R-parity violating couplings of higher generations, we analytically study the solutions of the renormalization group equations of these couplings together with the top- and b-quark Yukawa couplings. We show that only the B-violating coupling $\lambda^{''}_{233}$ approaches a non-trivial infra-red stable fixed point, whereas all other non-trivial fixed point solutions are either unphysical or unstable in the infra-red region. However, this fixed point solution predicts a top-quark Yukawa coupling which is incompatible with the top quark mass for any value of $\tan\beta$.",9902405v3 1999-06-10,Gauge Coupling Unification with Extra Dimensions and Gravitational Scale Effects,"We study gauge coupling unification in the presence of extra dimensions compactified at a few TeV. Achieving unification requires a large number of gauge boson Kaluza-Klein excitations lighter than the string scale, such that the higher-dimensional gauge couplings are O(1) in string scale units. Corrections to the gauge couplings from two or more loops are about 10% or larger, hence string (or M) theory is generally expected to be strongly coupled in TeV-scale extra-dimensional scenarios. Higher-dimensional operators induced by quantum gravitational effects can shift the gauge couplings by a few percent. These effects are sufficiently large that even the minimal Standard Model, or the MSSM, allow unification at a scale in the TeV range. The strongly coupled unified theory may induce dynamical electroweak symmetry breaking.",9906327v2 1999-10-04,Preheating of the nonminimally coupled inflaton field,"We investigate preheating of an inflaton field $\phi$ coupled nonminimally to a spacetime curvature. In the case of a self-coupling inflaton potential $V(\phi)=\lambda \phi^4/4$, the dynamics of preheating changes by the effect of the negative $\xi$. We find that the nonminimal coupling works in two ways. First, since the initial value of inflaton field for reheating becomes smaller with the increase of $|\xi|$, the evolution of the inflaton quanta is delayed for fixed $\lambda$. Second, the oscillation of the inflaton field is modified and the nonadiabatic change around $\phi=0$ occurs significantly. That makes the resonant band of the fluctuation field wider. Especially for strong coupling regimes $|\xi| \gg 1$, the growth of the inflaton flutuation is dominated by the resonance due to the nonminimal coupling, which leads to the significant enhancement of low momentum modes. Although the final variance of the inflaton fluctuation does notchange significantly compared with the minimally coupled case, we have found that the energy transfer from the homogeneous inflaton to created particles efficiently occurs for $\xi<-60$.",9910214v2 2000-04-27,Higgs sector and R-parity breaking couplings in models with broken U(1)_B-L gauge symmetry,"Four different supersymmetric models based on SU(2)_L X U(1)_R X U(1)_B-L and SU(2)_L X SU(2)_R X U(1)_B-L gauge symmetry groups are studied. U(1)_B-L symmetry is broken spontaneously by a vacuum expectation value (VEV) of a sneutrino field. The right-handed gauge bosons may obtain their mass solely by sneutrino VEV. The physical charged lepton and neutrino are mixtures of gauginos, higgsinos and lepton interaction eigenstates. Explicit formulae for masses and mixings in the physical lepton fields are found. The spontaneous symmetry breaking mechanism fixes the trilinear R-parity breaking couplings. Only some special R-parity breaking trilinear couplings are allowed. There is a potentially large trilinear lepton number breaking coupling - which is unique to left-right models - that is proportional to the SU(2)_R gauge coupling g_R. The couplings are parametrized by few mixing angles, making the spontaneous R-parity breaking a natural ``unification framework'' for R-parity breaking couplings in SUSYLR models.",0004239v1 2000-11-22,Infrared Fixed Point Structure in Minimal Supersymmetric Standard Model with Baryon and Lepton Number Violation,"We study in detail the renomalization group evolution of Yukawa couplings and soft supersymmetry breaking trilinear couplings in the minimal supersymmetric standard model with baryon and lepton number violation. We obtain the exact solutions of these equations in a closed form, and then depict the infrared fixed point structure of the third generation Yukawa couplings and the highest generation baryon and lepton number violating couplings. Approximate analytical solutions for these Yukawa couplings and baryon and lepton number violating couplings, and the soft supersymmetry breaking couplings are obtained in terms of their initial values at the unification scale. We then numerically study the infrared fixed surfaces of the model, and illustrate the approach to the fixed points.",0011274v2 2001-02-10,New analytic running coupling in spacelike and timelike regions,"The new model for the QCD analytic running coupling, proposed recently, is extended to the timelike region. This running coupling naturally arises under unification of the analytic approach to QCD and the renormalization group (RG) formalism. A new method for determining the coefficients of the ""analytized"" RG equation is elaborated. It enables one to take into account the higher loop contributions to the new analytic running coupling (NARC) in a consistent way. The expression for the new analytic running coupling, independent of the normalization point, is obtained by invoking the asymptotic freedom condition. It is shown that the difference between the values of the NARC in respective spacelike and timelike regions is rather valuable for intermediate energies. This is essential for the correct extracting of the running coupling from experimental data. The new analytic running coupling is applied to the description of the inclusive $\tau$ lepton decay. The consistent estimation of the parameter $\Lambda_{QCD}$ is obtained here.",0102124v2 2003-06-25,Probing triple gauge couplings with transverse beam polarisation in e+e- -> W+W-,"The prospects of measuring triple gauge couplings in W pair production at future linear colliders with transverse beam polarisation are studied. We consider CP conserving and CP violating couplings with both real and imaginary parts. The maximum achievable sensitivity in a simultaneous measurement of all couplings is determined using optimal observables, extending an earlier analysis for longitudinal beam polarisation. We find good sensitivity to the coupling Im(g^R_1 + kappa_R), which is not measurable with longitudinal polarisation. In contrast, for the real parts (including the CP violating couplings) the sensitivity is better if both beams are longitudinally polarised. We conclude that a comprehensive measurement of all triple gauge couplings requires both transverse and longitudinal beam polarisation.",0306247v2 2004-06-29,Extracting Higgs boson couplings from LHC data,"We show how LHC Higgs boson production and decay data can be used to extract gauge and fermion couplings of Higgs bosons. We show that very mild theoretical assumptions, which are valid in general multi-Higgs doublet models, are sufficient to allow the extraction of absolute values for the couplings rather than just ratios of the couplings. For Higgs masses below 200 GeV we find accuracies of 10-40% for the Higgs boson couplings and total width after several years of LHC running. Slightly stronger assumptions on the Higgs gauge couplings even lead to a determination of couplings to fermions at the level of 10-20%. We also study the sensitivity to deviations from SM predictions in several supersymmetric benchmark scenarios as a subset of the analysis.",0406323v1 2005-12-24,Pseudoscalar Photon Mixing In A Magnetized Medium,"Axions are pseudo-scalar particles, those arise because of breaking of Peccei Queen (PQ) symmetry. Axions have a tree level coupling to two photons. As a consequence there exists a tree level coupling of axion to photon in a magnetic field. However, in an external magnetic field, there exists a new loop induced, axion photon vertex, that gives rise to axion photon coupling. The strength of the tree level axion photon coupling in magnetic field is known to be model dependent. However in a magnetic field, the new loop induced coupling has some interesting features. This note discusses the new axion photon vertex in a magnetized medium and the corrections arising from there. The magnitude of the correction to axion photon coupling, because of magnetized vacuum and matter is estimated in this note. While making this estimate we note that the form of the axion photon vertex is related to the axial polarization tensor. This vertex is shown to satisfy the Ward identity. The coupling is shown to have a momentum dependent piece in it. Astrophysical importance of this extra modification is also pointed out.",0512323v1 2007-01-17,Implications of Canonical Gauge Coupling Unification in High-Scale Supersymmetry Breaking,"We systematically construct two kinds of models with canonical gauge coupling unification and universal high-scale supersymmetry breaking. In the first we introduce standard vector-like particles while in the second we also include non-standard vector-like particles. We require that the gauge coupling unification scale is from 5 x 10^{15} GeV to the Planck scale, that the universal supersymmetry breaking scale is from 10 TeV to the unification scale, and that the masses of the vector-like particles (M_V) are universal and in the range from 200 GeV to 1 TeV. Using two-loop renormalization group equation (RGE) running for the gauge couplings and one-loop RGE running for Yukawa couplings and the Higgs quartic coupling, we calculate the supersymmetry breaking scales, the gauge coupling unification scales, and the corresponding Higgs mass ranges. When the vector-like particle masses are less than 1 TeV, these models can be tested at the LHC.",0701136v1 2007-03-19,Anomalous Quartic $WWγγ$ and $ZZγγ$ Couplings in $eγ$ Collision With Initial Beams and Final State Polarizations,"The constraints on the anomalous quartic $WW\gamma\gamma$ and $ZZ\gamma\gamma$ gauge boson couplings are investigated through the processes $e\gamma\to W^{-}\gamma\nu_{e}$ and $e\gamma\to Z\gamma e$. Considering the longitudinal and transverse polarization states of the final W or Z boson and incoming beam polarizations we find 95% confidence level limits on the anomalous coupling parameters $a_{0}$ and $a_{c}$ with an integrated luminosity of 500 $fb^{-1}$ and $\sqrt{s}$=0.5, 1 TeV energies. Assuming the $W^{+}W^{-}\gamma\gamma$ couplings are independent of the $ZZ\gamma\gamma$ couplings we show that the longitudinal polarization state of the final gauge boson improves the sensitivity to anomalous couplings by a factor of 2-3 depending on energy and coupling. An extra enhancement in sensitivity by a factor of 1.3 comes from a set of initial beam polarizations.",0703201v1 2001-09-13,Non-minimal coupling for spin 3/2 fields,"The problem of the electromagnetic coupling for spin 3/2 fields is discussed. Following supergravity and some recent works in the field of classical supersymmetric particles, we find that the electromagnetic coupling must not obey a minimal coupling in the sense that one needs to consider not only the electromagnetic potential but also the coupling of the electromagnetic field strenght. This coupling coincides with the one found by Ferrara {\it et al} by requiring that the gyromagnetic ratio be 2. Coupling with non-Abelian Yang-Mills fields is also discussed.",0109104v1 2003-02-14,Yukawa couplings in intersecting D-brane models,"We compute the Yukawa couplings among chiral fields in toroidal Type II compactifications with wrapping D6-branes intersecting at angles. Those models can yield realistic standard model spectrum living at the intersections. The Yukawa couplings depend both on the Kahler and open string moduli but not on the complex structure. They arise from worldsheet instanton corrections and are found to be given by products of complex Jacobi theta functions with characteristics. The Yukawa couplings for a particular intersecting brane configuration yielding the chiral spectrum of the MSSM are computed as an example. We also show how our methods can be extended to compute Yukawa couplings on certain classes of elliptically fibered CY manifolds which are mirror to complex cones over del Pezzo surfaces. We find that the Yukawa couplings in intersecting D6-brane models have a mathematical interpretation in the context of homological mirror symmetry. In particular, the computation of such Yukawa couplings is related to the construction of Fukaya's category in a generic symplectic manifold.",0302105v2 2005-04-04,Flavor structure and coupling selection rule from intersecting D-branes,"We study flavor structure and the coupling selection rule in intersecting D-brane configurations. We formulate the selection rule for Yukawa couplings and its extensions to generic n-point couplings. We investigate the possible flavor structure, which can appear from intersecting D-brane configuration, and it is found that their couplings are determined by discrete abelian symmetry. Our studies on the flavor structure and the coupling selection rule show that the minimal matter content of the supersymmetric standard model would have difficulty to derive realistic Yukawa matrices from stringy 3-point couplings at the tree-level. However, extended models have a richer structure, leading to non-trivial mass matrices.",0504019v1 2007-03-26,Gravitating Monopole-Antimonopole Systems at Large Scalar Coupling,"We discuss static axially symmetric solutions of SU(2) Einstein-Yang-Mills-Higgs theory for large scalar coupling. These regular asymptotically flat solutions represent monopole-antimonopole chain and vortex ring solutions, as well as new configurations, present only for larger values of the scalar coupling. When gravity is coupled to the Yang-Mills-Higgs system, branches of gravitating solutions emerge from the flat-space solutions, and extend up to critical values of the gravitational coupling constant. For small scalar coupling only two branches of gravitating solutions exist, where the second branch connects to a generalized Bartnik-McKinnon solution. For large scalar coupling, however, a plethora of gravitating branches can be present and indicate the emergence of new flat-space branches.",0703232v1 2004-08-10,Ergodic Dynamics of the Coupled Quasigeostrophic Flow-Energy Balance System,"The authors consider a mathematical model for the coupled atmosphere-ocean system, namely, the coupled quasigeostrophic flow-energy balance model. This model consists of the large scale quasigeostrophic oceanic flow model and the transport equation for oceanic temperature, coupled with an atmospheric energy balance model. After reformulating this coupled model as a random dynamical system (cocycle property), it is shown that the coupled quasigeostrophic-energy balance fluid system has a random attractor, and under further conditions on the physical data and the covariance of the noise, the system is ergodic, namely, for any observable of the coupled atmosphere-ocean flows, its time average approximates the statistical ensemble average, as long as the time interval is sufficiently long.",0408135v1 2005-11-23,Discrete vector on-site vortices,"We study discrete vortices in coupled discrete nonlinear Schrodinger equations. We focus on the vortex cross configuration that has been experimentally observed in photorefractive crystals. Stability of the single-component vortex cross in the anti-continuum limit of small coupling between lattice nodes is proved. In the vector case, we consider two coupled configurations of vortex crosses, namely the charge-one vortex in one component coupled in the other component to either the charge-one vortex (forming a double-charge vortex) or the charge-negative-one vortex (forming a, so-called, hidden-charge vortex). We show that both vortex configurations are stable in the anti-continuum limit if the parameter for the inter-component coupling is small and both of them are unstable when the coupling parameter is large. In the marginal case of the discrete two-dimensional Manakov system, the double-charge vortex is stable while the hidden-charge vortex is linearly unstable. Analytical predictions are corroborated with numerical observations that show good agreement near the anti-continuum limit but gradually deviate for larger couplings between the lattice nodes.",0511586v1 2006-11-21,Metastability in Interacting Nonlinear Stochastic Differential Equations I: From Weak Coupling to Synchronisation,"We consider the dynamics of a periodic chain of N coupled overdamped particles under the influence of noise. Each particle is subjected to a bistable local potential, to a linear coupling with its nearest neighbours, and to an independent source of white noise. We show that as the coupling strength increases, the number of equilibrium points of the system changes from 3^N to 3. While for weak coupling, the system behaves like an Ising model with spin-flip dynamics, for strong coupling (of the order N^2), it synchronises, in the sense that all oscillators assume almost the same position in their respective local potential most of the time. We derive the exponential asymptotics for the transition times, and describe the most probable transition paths between synchronised states, in particular for coupling intensities below the synchronisation threshold. Our techniques involve a centre-manifold analysis of the desynchronisation bifurcation, with a precise control of the stability of bifurcating solutions, allowing us to give a detailed description of the system's potential landscape, in which the metastable behaviour is encoded.",0611647v2 2003-07-22,Synchronized clusters in coupled map networks: Stability analysis,"We study self-organized (s-) and driven (d-) synchronization in coupled map networks for some simple networks, namely two and three node networks and their natural generalization to globally coupled and complete bipartite networks. We use both linear stability analysis and Lyapunov function approach for this study and determine stability conditions for synchronization. We see that most of the features of coupled dynamics of small networks with two or three nodes, are carried over to the larger networks of the same type. The phase diagrams for the networks studied here have features very similar to the different kinds of networks studied in Ref. \cite{sarika-REA2}. The analysis of the dynamics of the difference variable corresponding to any two nodes shows that when the two nodes are in driven synchronization, all the coupling terms cancel out whereas when they are in self-organized synchronization, the direct coupling term between the two nodes adds an extra decay term while the other couplings cancel out.",0307037v1 2006-08-09,Delayed-mutual coupling dynamics of lasers: scaling laws and resonances,"We consider a model for two lasers that are mutually coupled optoelectronically by modulating the pump of one laser with the intensity deviations of the other. Signal propagation time in the optoelectronic loop causes a significant delay leading to the onset of oscillatory output. Multiscale perturbation methods are used to describe the amplitude and period of oscillations as a function of the coupling strength and delay time. For weak coupling the oscillations have the laser's relaxation period, and the amplitude varies as the one-fourth power of the parameter deviations from the bifurcation point. For order-one coupling strength the period is determined as multiples of the delay time, and the amplitude varies with a square-root power law. Because we allow for independent control of the individual coupling constants, for certain parameter values there is an atypical amplitude-resonance phenomena. Finally, our theoretical results are consistent with recent experimental observations when the inclusion of a low-pass filter in the coupling loop is taken into account.",0608015v1 1999-04-18,$πNN$ coupling determined beyond the chiral limit,"Within the conventional QCD sum rules, we calculate the $\pi NN$ coupling constant, $g_{\pi N}$, beyond the chiral limit using two-point correlation function with a pion. We consider the Dirac structure, $i\gamma_5$, at $m_\pi^2$ order, which has clear dependence on the PS and PV coupling schemes for the pion-nucleon interactions. For a consistent treatment of the sum rule, we include the linear terms in quark mass as they constitute the same chiral order as $m_\pi^2$. Using the PS coupling scheme for the pion-nucleon interaction, we obtain $g_{\pi N}=13.3\pm 1.2$, which is very close to the empirical $\pi NN$ coupling. This demonstrates that going beyond the chiral limit is crucial in determining the coupling and the pseudoscalar coupling scheme is preferable from the QCD point of view.",9904049v2 2001-09-21,An Analysis of the $^{12}$C+$^{24}$Mg Reaction Using A New Coupling Potential,"We introduce a new coupling potential to explain the experimental data for the $^{12}$C+$^{24}$Mg system at numerous energies in the laboratory system from 16.0 MeV to 24.0 MeV. This new coupled-channels based approach involves replacing the usual first derivative coupling potential by a new, second-derivative coupling potential. This paper first shows and discusses the limitation of the standard coupled-channels theory in the case where one of the nuclei in the reaction is strongly deformed. Then, this new approach is shown to improve consistently the agreement with the experimental data and has made major improvement on all the previous coupled-channels calculations for this system.",0109064v1 2000-12-06,Perturbative treatment of intercenter coupling in Redfield theory,"The quantum dynamics of coupled subsystems connected to a thermal bath is studied. In some of the earlier work the effect of intercenter coupling on the dissipative part was neglected. This is equivalent to a zeroth-order perturbative expansion of the damping term with respect to the intercenter coupling. It is shown numerically for two coupled harmonic oscillators that this treatment can lead to artifacts and a completely wrong description, for example, of a charge transfer processes even for very weak intercenter coupling. Here we perform a first-order treatment and show that these artifacts disappear. In addition, we demonstrate that the thermodynamic equilibrium population is almost reached even for strong intercenter coupling strength.",0012012v1 2005-04-14,Coupling into the slow light mode in slab-type photonic crystal waveguides,"Coupling of external light signals into a photonic crystal waveguide becomes increasingly inefficient as the group velocity of the waveguiding mode slows down. We have systematically studied the efficiency of coupling in the slow light regime for samples with different truncations of the photonic lattice at the coupling interface. Inverse power law dependence is found to best fit the experimental scaling of the coupling loss on the group index. Coupling efficiency is found to be significantly improved up to group indices of 100 for a truncation of the lattice that favors the appearance of the photonic surface states at the coupling interface in resonance with the slow light mode.",0504102v4 2003-07-18,Entanglement production in coupled chaotic systems : Case of the Kicked Tops,"Entanglement production in coupled chaotic systems is studied with the help of kicked tops. Deriving the correct classical map, we have used the reduced Husimi function, the Husimi function of the reduced density matrix, to visualize the possible behaviors of a wavepacket. We have studied a phase space based measure of the complexity of a state and used random matrix theory (RMT) to model the strongly chaotic cases. Extensive numerical studies have been done for the entanglement production in coupled kicked tops corresponding to different underlying classical dynamics and different coupling strengths. An approximate formula, based on RMT, is derived for the entanglement production in coupled strongly chaotic systems. This formula, applicable for arbitrary coupling strengths and also valid for long time, complements and extends significantly recent perturbation theories for strongly chaotic weakly coupled systems.",0307134v2 2007-09-05,Strain dependent twist-stretch elasticity in chiral filaments,"Coupling between axial and torsional degrees of freedom often modifies the conformation and expression of natural and synthetic filamentous aggregates. Recent studies on chiral single-walled carbon nanotubes and B-DNA reveal a reversal in the sign of the twist-stretch coupling at large strains. The similarity in the response in these two distinct supramolecular assemblies and at high strains suggests a fundamental, chirality dependent non-linear elastic behaviour. Here, we seek the link between the microscopic origin of the non-linearities and the effective twist-stretch coupling using energy based theoretical frameworks and model simulations. Our analysis reveals a sensitive interplay between the deformation energetics and the sign of the coupling, highlighting robust design principles that determine both the sign and extent of these couplings. These design principles have been already exploited by Nature to dynamically engineer such couplings, and have broad implications in mechanically coupled actuation, propulsion and transport in biology and technology.",0709.0558v1 2007-10-09,Direct Detection of Non-Chiral Dark Matter,"Direct detection experiments rule out fermion dark matter that is a chiral representation of the electroweak gauge group. Non-chiral real, complex and singlet representations, however, provide viable fermion dark matter candidates. Although any one of these candidates will be virtually impossible to detect at the LHC, it is shown that they may be detected at future planned direct detection experiments. For the real case, an irreducible radiative coupling to quarks may allow a detection. The complex case in general has an experimentally ruled out tree-level coupling to quarks via Z-boson exchange. However, in the case of two SU(2)_L doublets, a higher dimensional coupling to the Higgs can suppress this coupling, and a remaining irreducible radiative coupling may allow a detection. Singlet dark matter could be detected through a coupling to quarks via Higgs exchange. Since all non-chiral dark matter can have a coupling to the Higgs, at least some of its mass can be obtained from electroweak symmetry breaking, and this mass is a useful characterization of its direct detection cross-section.",0710.1668v2 2008-04-05,Analytic QCD - a short review,"Analytic versions of QCD are those whose coupling alpha_s(Q^2) does not have the unphysical Landau singularities on the space-like axis (-q^2=Q^2 > 0). The coupling is analytic in the entire complex plane except the time-like axis (Q^2 < 0). Such couplings are thus suitable for application of perturbative methods down to energies of order GeV. We present a short review of the activity in the area which started with a seminal paper of Shirkov and Solovtsov ten years ago. Several models for analytic QCD coupling are presented. Strengths and weaknesses of some of these models are pointed out. Further, for such analytic couplings, constructions of the corresponding higher order analytic couplings (the analogs of the higher powers of the perturbative coupling) are outlined, and an approach based on the renormalization group considerations is singled out. Methods of evaluation of the leading-twist part of space-like observables in such analytic frameworks are described. Such methods are applicable also to the inclusive time-like observables. Two analytic models are outlined which respect the ITEP Operator Product Expansion philosophy, and thus allow for an evaluation of higher-twist contributions to observables.",0804.0872v2 2008-10-01,Magnetic Order Beyond RKKY in the Classical Kondo Lattice,"We study the Kondo lattice model of band electrons coupled to classical spins, in three dimensions, using a combination of variational calculation and Monte Carlo. We use the weak coupling `RKKY' window and the strong coupling regime as benchmarks, but focus on the physically relevant intermediate coupling regime. Even for modest electron-spin coupling the phase boundaries move away from the RKKY results, the non interacting Fermi surface no longer dictates magnetic order, and weak coupling `spiral' phases give way to collinear order. We use these results to revisit the classic problem of 4f magnetism and demonstrate how both electronic structure and coupling effects beyond RKKY control the magnetism in these materials.",0810.0140v2 2008-11-22,Synchronization of coupled demographic oscillators,"Demographic oscillators are individual-based systems exhibiting temporal cycles sustained by the stochastic dynamics of the microscopic interacting particles. We here use the example of coupled predator-prey oscillators to show that synchronization to a common frequency can occur between two such systems, even if they oscillate at different frequencies in the absence of coupling. The power spectra of the separate and the coupled systems are computed within a van Kampen expansion in the inverse system size, and it is found that they exhibit two peaks at separate frequencies at low coupling, but that only one peak is present at large enough coupling strength. We further make predictions on the time behaviour of the phases of the two oscillators, and their phase difference, and confirm the frequency entrainment at sufficiently large coupling. Theoretical results are verified convincingly in numerical simulations.",0811.3689v1 2009-03-06,Universality of the Nf=2 Running Coupling,"We investigate universality of the Nf=2 running coupling in the Sch\""odinger functional scheme, by calculating the step scaling function in lattice QCD with the renorm alization group (RG) improved gauge action at both weak(u=0.9796) and strong(u=3.3340) couplings, where u=\bar{g}^2_SF with \bar{g}_SF being the running coupling in this scheme. In our main calculations, we use the tree-level value for O(a) improvement coefficients of boundary gauge fields. In addition we employ the 1-loop value for them in order to see how scaling behaviours are affected by them. In the continuum limit, the step scaling function obtained from the RG improved gauge actions agrees with the previous result obtained from the plaquette action within errors at both couplings, though errors of our result are larger. Combined fits using all data with the RG improved action as well as the plaquette action reduce errors in the continuum limit by 2% at the weak coupling and 22% at the strong coupling.",0903.1154v1 2009-03-20,Semi-passivity and synchronization of diffusively coupled neuronal oscillators,"We discuss synchronization in networks of neuronal oscillators which are interconnected via diffusive coupling, i.e. linearly coupled via gap junctions. In particular, we present sufficient conditions for synchronization in these networks using the theory of semi-passive and passive systems. We show that the conductance-based neuronal models of Hodgkin-Huxley, Morris-Lecar, and the popular reduced models of FitzHugh-Nagumo and Hindmarsh-Rose all satisfy a semi-passivity property, i.e. that is the state trajectories of such a model remain oscillatory but bounded provided that the supplied (electrical) energy is bounded. As a result, for a wide range of coupling configurations, networks of these oscillators are guaranteed to possess ultimately bounded solutions. Moreover, we demonstrate that when the coupling is strong enough the oscillators become synchronized. Our theoretical conclusions are confirmed by computer simulations with coupled \HR and \ML oscillators. Finally we discuss possible ""instabilities"" in networks of oscillators induced by the diffusive coupling.",0903.3535v1 2009-03-26,Quantum Localization for Two Coupled Kicked Rotors,"We study a system of two coupled kicked rotors, both classically and quantum mechanically, for a wide range of coupling parameters. This was motivated by two published reports, one of which reported quantum localization, while the other reported diffusion. The classical systems are chaotic, and exhibit normal diffusive behavior. In the quantum systems, we found different regimes, depending on the strength of the coupling. For weak coupling, we found quantum localization similar to that exhibited by single kicked rotors. For strong coupling, we found a quasi-diffusive growth of the width of the momentum distribution, in which the apparent diffusion coefficient decreased as time increased. The behavior in this regime can be described by the scaling theory of weak localization for two-dimensional disordered lattices. The weak and strong coupling regimes are separated by a regime of complex intermediate behavior. Thus we explain the apparent contradiction in the literature as being due to qualitatively different regimes of behavior, which we call strong and weak quantum localization.",0903.4632v2 2009-04-08,The exchange fluctuation theorem in quantum mechanics,"We study the heat transfer between two finite quantum systems initially at different temperatures. We find that a recently proposed fluctuation theorem for heat exchange, namely the exchange fluctuation theorem [C. Jarzynski and D. K. Wojcik, Phys. Rev. Lett. 92, 230602 (2004)], does not generally hold in the presence of a finite heat transfer as in the original form proved for weak coupling. As the coupling is weakened, the deviation from the theorem and the heat transfer vanish in the same order of the coupling. We then discover a condition for the exchange fluctuation theorem to hold in the presence of a finite heat transfer, namely the commutable-coupling condition. We explicitly calculate the deviation from the exchange fluctuation theorem as well as the heat transfer for simple models. We confirm for the models that the deviation indeed has a finite value as far as the coupling between the two systems is finite except for the special point of the commutable-coupling condition. We also confirm analytically that the commutable-coupling condition indeed lets the exchange fluctuation theorem hold exactly under a finite heat transfer.",0904.1443v1 2009-04-15,Soliton Dynamics in Linearly Coupled Discrete Nonlinear Schrödinger Equations,"We study soliton dynamics in a system of two linearly coupled discrete nonlinear Schr\""odinger equations, which describe the dynamics of a two-component Bose gas, coupled by an electromagnetic field, and confined in a strong optical lattice. When the nonlinear coupling strengths are equal, we use a unitary transformation to remove the linear coupling terms, and show that the existing soliton solutions oscillate from one species to the other. When the nonlinear coupling strengths are different, the soliton dynamics is numerically investigated and the findings are compared to the results of an effective two-mode model. The case of two linearly coupled Ablowitz-Ladik equations is also investigated.",0904.2415v1 2009-07-30,The strong-coupling limit of a Kondo spin coupled to a mesoscopic quantum dot: effective Hamiltonian in the presence of exchange correlations,"We consider a Kondo spin that is coupled antiferromagnetically to a large chaotic quantum dot. Such a dot is described by the so-called universal Hamiltonian and its electrons are interacting via a ferromagnetic exchange interaction. We derive an effective Hamiltonian in the limit of strong Kondo coupling, where the screened Kondo spin effectively removes one electron from the dot. We find that the exchange coupling constant in this reduced dot (with one less electron) is renormalized and that new interaction terms appear beyond the conventional terms of the strong-coupling limit. The eigenenergies of this effective Hamiltonian are found to be in excellent agreement with exact numerical results of the original model in the limit of strong Kondo coupling.",0907.5297v1 2009-08-14,Probing scalar particle and unparticle couplings in e+ e- -> t tbar with transversely polarized beams,"In searching for indications of new physics scalar particle and unparticle couplings in e^+ e^- \to t\bar t, we consider the role of transversely polarized initial beams at e^+ e^- colliders. By using a general relativistic spin density matrix formalism for describing the particles spin states, we find analytical expressions for the squared amplitude of the process with t or \bar t polarization measured, including the anomalous coupling contributions. Thanks to the transversely polarized initial beams these contributions are first order anomalous coupling corrections to the Standard Model (SM) contributions. We present and analyse the main features of the SM and anomalous coupling contributions. We show how differences between SM and anomalous coupling contributions provide means to search for anomalous coupling manifestations at future e^+ e^- linear colliders.",0908.2027v2 2009-09-11,Couplings between dipole and quadrupole vibrations in tin isotopes,"We study the couplings between collective vibrations such as the isovector giant dipole and isoscalar giant quadrupole resonances in tin isotopes in the framework of the time-dependent Hartree-Fock theory with a Skyrme energy density functional. These couplings are a source of anharmonicity in the multiphonon spectrum. In particular, the residual interaction is known to couple the isovector giant dipole resonance with the isoscalar giant quadrupole resonance built on top of it, inducing a nonlinear evolution of the quadrupole moment after a dipole boost. This coupling also affects the dipole motion in a nucleus with a static or dynamical deformation induced by a quadrupole constraint or boost respectively. Three methods associated with these different manifestations of the coupling are proposed to extract the corresponding matrix elements of the residual interaction. Numerical applications of the different methods to 132Sn are in good agreement with each other. Finally, several tin isotopes are considered to investigate the role of isospin and mass number on this coupling. A simple 1/A dependence of the residual matrix elements is found with no noticeable contribution from the isospin. This result is interpreted within the Goldhaber-Teller model.",0909.2092v2 2009-09-13,Formation of Intermediate Coupling Optical Polarons and Bipolarons in Two-Dimensional Systems,"he formation of the optical polaron and bipolaron in two-dimensional (2D) systems are studied in the intermediate electron-phonon coupling regime. The total energies of 2D polaron and bipolaron are calculated by using the Buimistrov-Pekar method of canonical transformations and analyzed in the weak, intermediate and strong coupling regimes. It is shown that the electron-phonon correlation significantly reduces the total energy of 2D polaron in comparison with the energy of the strong-coupling (adiabatic) polaron. A charge carrier in polar crystals remains localized in a 2D potential well when the electron-phonon coupling constant $\alpha$ is greater than the critical value $\alpha_{c}\simeq2.94$, which is much lower than a critical value of the electron-phonon coupling constant $\alpha$ for a 3D system. The critical values of the electron-phonon coupling constant $\alpha$ and the parameter of Coulomb repulsion between two carriers $\beta=1/(1-\epsilon_{\infty}/\epsilon_{0})$ (where $\epsilon_{\infty}$ and $\epsilon_{0}$ are the high frequency and static dielectric constants, respectively), which determine the bipolaron stability region, are numerically calculated. The obtained results are compared with the ones obtained by using the Feynman path integral method and the modified Lee-Low-Pines unitary transformation method.",0909.2414v1 2009-09-15,Linear coupling of modes in 2D radially stratified astrophysical discs,"We investigate mode coupling in a two dimensional compressible disc with radial stratification and differential rotation. We employ the global radial scaling of linear perturbations and study the linear modes in the local shearing sheet approximation. We employ a three-mode formalism and study the vorticity (W), entropy (S) and compressional (P) modes and their coupling properties. The system exhibits asymmetric three-mode coupling: these include mutual coupling of S and P-modes, S and W-modes, and asymmetric coupling between the W and P-modes. P-mode perturbations are able to generate potential vorticity through indirect three-mode coupling. This process indicates that compressional perturbations can lead to the development of vortical structures and influence the dynamics of radially stratified hydrodynamic accretion and protoplanetary discs.",0909.2844v1 2009-11-01,Hierarchy of relevant couplings in perturbative renormalization group transformations,"The phase diagram for the interacting fermions in weak coupling is described by the perturbative renormalization group equations. Due to the lack of analytic solutions for these coupled non-linear differential equations, it is rather subtle to tell which couplings are relevant or irrelevant. We propose a powerful classification scheme to build up the hierarchy of the relevant couplings by a scaling Ansatz found numerically. To demonstrate its superiority over the conventional classification for the relevant couplings, we apply this scheme to a controversial phase transition in the two-leg ladder and show that it should be a non-trivial crossover instead. The scaling Ansatz we propose here can classify the relevant couplings in hierarchical order without any ambiguity and can improve significantly how we interpret the numerical outcomes in general renormalization group methods.",0911.0166v2 2009-11-23,Couplings in coupled channels versus wave functions: application to the X(3872) resonance,"We perform an analytical study of the scattering matrix and bound states in problems with many physical coupled channels. We establish the relationship of the couplings of the states to the different channels, obtained from the residues of the scattering matrix at the poles, with the wave functions for the different channels. The couplings basically reflect the value of the wave functions around the origin in coordinate space. In the concrete case of the X(3872) resonance, understood as a bound state of $\ddn$ and $\ddc$ (and $c.c.$), with the $\ddn$ loosely bound, we find that the couplings to the two channels are essentially equal leading to a state of good isospin I=0 character. This is in spite of having a probability for finding the $\ddn$ state much larger than for $\ddc$ since the loosely bound channel extends further in space. The analytical results, obtained with exact solutions of the Schr\""odinger equation for the wave functions, can be useful in general to interpret results found numerically in the study of problems with unitary coupled channels methods.",0911.4407v2 2010-02-02,Generalized Rashba spin-orbit coupling for cold atoms,"We study the possibility to generate a new type of spin-orbit coupling for the center of mass motion of cold atoms, using laser beams that resonantly couple N atomic internal ground states to an extra state. After a general analysis of the scheme, we concentrate on the tetrapod setup (N=4) where the atomic state can be described by a three-component spinor, evolving under the action of a Rashba-type spin-orbit coupling for a spin 1 particle. We illustrate a consequence of this coupling by studying the negative refraction of atoms at a potential step, and show that the amplitude of the refracted beam is significantly increased in comparison to the known case of spin 1/2 Rashba coupling. Finally we explore a possible implementation of this tetrapod setup, using stimulated Raman couplings between Zeeman sublevels of the ground state of alkali atoms.",1002.0578v2 2010-06-23,Motion of pole-dipole and quadrupole particles in non-minimally coupled theories of gravity,"We study theories of gravity with non-minimal coupling between polarized media with pole-dipole and quadrupole moments and an arbitrary function of the space-time curvature scalar $R$ and the squares of the Ricci and Riemann curvature tensors. We obtain the general form of the equation of motion and show that an induced quadrupole moment emerges as a result of the curvature tensor dependence of the function coupled to the matter. We derive the explicit forms of the equations of motion in the particular cases of coupling to a function of the curvature scalar alone, coupling to an arbitrary function of the square of the Riemann curvature tensor, and coupling to an arbitrary function of the Gauss-Bonnet invariant. We show that in these cases the extra force resulting from the non-minimal coupling can be expressed in terms of the induced moments.",1006.4415v1 2010-06-28,Imaginary Cubic Perturbation: Numerical and Analytic Study,"The analytic properties of the ground state resonance energy E(g) of the cubic potential are investigated as a function of the complex coupling parameter g. We explicitly show that it is possible to analytically continue E(g) by means of a resummed strong coupling expansion, to the second sheet of the Riemann surface, and we observe a merging of resonance and antiresonance eigenvalues at a critical point along the line arg(g) = 5 pi/4. In addition, we investigate the convergence of the resummed weak-coupling expansion in the strong coupling regime, by means of various modifications of order-dependent mappings (ODM), that take special properties of the cubic potential into account. The various ODM are adapted to different regimes of the coupling constant. We also determine a large number of terms of the strong coupling expansion by resumming the weak-coupling expansion using the ODM, demonstrating the interpolation between the two regimes made possible by this summation method.",1006.5303v2 2010-07-13,Dynamical evolution of a scalar field coupling to Einstein's tensor in the Reissner-Nordström black hole spacetime,"We study the dynamical evolution of a scalar field coupling to Einstein's tensor in the background of Reissner-Nordstr\""{o}m black hole. Our results show that the the coupling constant $\eta$ imprints in the wave dynamics of a scalar perturbation. In the weak coupling, we find that with the increase of the coupling constant $\eta$ the real parts of the fundamental quasinormal frequencies decrease and the absolute values of imaginary parts increase for fixed charge $q$ and multipole number $l$. In the strong coupling, we find that for $l\neq0$ the instability occurs when $\eta$ is larger than a certain threshold value $\eta_c$ which deceases with the multipole number $l$ and charge $q$. However, for the lowest $l=0$, we find that there does not exist such a threshold value and the scalar field always decays for arbitrary coupling constant.",1007.2019v2 2010-07-22,Equivalence condition for the canonical and microcanonical ensembles in coupled spin systems,"It is typically assumed, without justification, that a weak coupling between a system and a bath is a necessary condition for the equivalence of a canonical ensemble and a microcanonical ensemble. For instance, in a canonical ensemble, temperature emerges if the system and the bath are uncoupled or weakly coupled. We investigate the validity region of this weak coupling approximation, using a coupled composite-spin system. Our results show that the spin coupling strength can be as large as the level spacing of the system, indicating that the weak coupling approximation has a much wider region of validity than usually expected.",1007.3877v1 2010-07-22,Couplings in coupled channels versus wave functions in the case of resonances: application to the two $Λ(1405)$ states,"In this paper we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on shell approach for the scattering matrix, commonly used, is also obtained in Quantum Mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two $\Lambda(1405)$ states in the $\pi \Sigma$, $\bar{K} N$ and other coupled channels.",1007.3923v2 2010-07-26,Phase synchronization between collective rhythms of globally coupled oscillator groups: noisy identical case,"We theoretically investigate collective phase synchronization between interacting groups of globally coupled noisy identical phase oscillators exhibiting macroscopic rhythms. Using the phase reduction method, we derive coupled collective phase equations describing the macroscopic rhythms of the groups from microscopic Langevin phase equations of the individual oscillators via nonlinear Fokker-Planck equations. For sinusoidal microscopic coupling, we determine the type of the collective phase coupling function, i.e., whether the groups exhibit in-phase or anti-phase synchronization. We show that the macroscopic rhythms can exhibit effective anti-phase synchronization even if the microscopic phase coupling between the groups is in-phase, and vice versa. Moreover, near the onset of collective oscillations, we analytically obtain the collective phase coupling function using center-manifold and phase reductions of the nonlinear Fokker-Planck equations.",1007.4382v1 2010-07-29,Phase synchronization between collective rhythms of globally coupled oscillator groups: noiseless non-identical case,"Phase synchronization between collective oscillations exhibited by two weakly interacting groups of non-identical phase oscillators with internal and external global sinusoidal coupling of the groups is analyzed theoretically. Coupled amplitude equations describing the collective oscillations of the oscillator groups are obtained by using the Ott-Antonsen ansatz, and then coupled phase equations for the collective oscillations are derived by phase reduction of the amplitude equations. The collective phase coupling function, which determines the dynamics of macroscopic phase differences between the groups, is calculated analytically. It is demonstrated that the groups can exhibit effective anti-phase collective synchronization even if the microscopic external coupling between individual oscillator pairs belonging to different groups is in-phase, and similarly effective in-phase collective synchronization in spite of microscopic anti-phase external coupling between the groups.",1007.5161v1 2010-08-18,Superposition of Inductive and Capacitive Coupling in Superconducting LC Resonators,"We present an experimental investigation of lumped-element superconducting LC resonators designed to provide different types of coupling to a transmission line. We have designed four resonator geometries including dipole and quadrupole configured inductors connected in parallel with low loss SiNx dielectric parallel-plate capacitors. The design of the resonator allows a small change in the symmetry of the inductor or grounding of the capacitor to allow LC resonators with: 1) inductive coupling, 2) capacitive coupling, 3) both types of coupling, or 4) greatly reduced coupling. We measured all four designs at a temperature of 30mK at different values of power. We compare the extracted data from the four resonator types and find that both capacitive and inductive coupling can be included and that when left off, only a minor change in the circuit design is necessary. We also find a variation in the measured loss tangent of less than a few percent, which is a test of the systematic precision of the measurement technique.",1008.3130v1 2010-08-19,Synchronization transitions in coupled time-delay electronic circuits with a threshold nonlinearity,"Experimental observations of typical kinds of synchronization transitions are reported in unidirectionally coupled time-delay electronic circuits with a threshold nonlinearity and two time delays, namely feedback delay $\tau_1$ and coupling delay $\tau_2$. We have observed transitions from anticipatory to lag via complete synchronization and their inverse counterparts with excitatory and inhibitory couplings, respectively, as a function of the coupling delay $\tau_2$. The anticipating and lag times depend on the difference between the feedback and the coupling delays. A single stability condition for all the different types of synchronization is found to be valid as the stability condition is independent of both the delays. Further, the existence of different kinds of synchronizations observed experimentally is corroborated by numerical simulations, and from the changes in the Lyapunov exponents of the coupled time-delay systems.",1008.3300v1 2010-09-15,Deducing spectroscopic factors from wave-function asymptotics,"In a coupled-channel model, we explore the effects of coupling between configurations on the radial behavior of the wave function and, in particular, on the spectroscopic factor (SF) and the asymptotic normalization coefficient (ANC). We evaluate the extraction of a SF from the ratio of the ANC of the coupled-channel model to that of a single-particle approximation of the wave function. We perform this study within a core + n collective model, which includes two states of the core that connect by a rotational coupling. To get additional insights, we also use a simplified model that takes a delta function for the coupling potential. Calculations are performed for 11Be. Fair agreement is obtained between the SF inferred from the single-particle approximation and the one obtained within the coupled-channel models. Significant discrepancies are observed only for large coupling strength and/or large admixture, that is, a small SF. This suggests that reliable SFs can be deduced from the wave-function asymptotics when the structure is dominated by one configuration, that is, for a large SF.",1009.2878v3 2010-10-04,Consistent Energy-Based Atomistic/Continuum Coupling for Two-Body Potentials in One and Two Dimensions,"This paper addresses the problem of consistent energy-based coupling of atomistic and continuum models of materials, limited to zero-temperature statics of simple crystals. It has been widely recognized that the most practical coupled methods exhibit large errors on the atomistic/continuum interface (which are often attributed to spurious forces called ""ghost forces""). There are only few existing works that propose a coupling which is sufficiently accurate near the interface under certain limitations. In this paper a novel coupling that is free from ""ghost forces"" is proposed for a two-body interaction potential under the assumptions of either (i) one spatial dimension, or (ii) two spatial dimensions and piecewise affine finite elements for describing the continuum deformation. The performance of the proposed coupling is demonstrated with numerical experiments. The coupling strategy is based on judiciously defining the contributions of the atomistic bonds to the discrete and the continuum potential energy. The same method in one dimension has been independently developed and analyzed in Li and Luskin (arXiv:1007.2336).",1010.0512v3 2010-10-27,Cosmology of Chameleons with Power-Law Couplings,"In chameleon field theories a scalar field can couple to matter with gravitational strength and still evade local gravity constraints due to a combination of self-interactions and the couplings to matter. Originally, these theories were proposed with a constant coupling to matter, however, the chameleon mechanism also extends to the case where the coupling becomes field-dependent. We study the cosmology of chameleon models with power-law couplings and power-law potentials. It is found that these generalized chameleons, when viable, have a background expansion very close to LCDM, but can in some special cases enhance the growth of the linear perturbations at low redshifts. For the models we consider it is found that this region of the parameter space is ruled out by local gravity constraints. Imposing a coupling to dark matter only, the local constraints are avoided, and it is possible to have observable signatures on the linear matter perturbations.",1010.5650v2 2010-11-13,Crowd synchrony and quorum sensing in delay-coupled lasers,"Crowd synchrony and quorum sensing arise when a large number of dynamical elements communicate with each other via a common information pool. Previous evidence in different fields, including chemistry, biology and civil engineering, has shown that this type of coupling leads to synchronization, when coupling is instantaneous and the number of coupled elements is large enough. Here we consider a situation in which the transmission of information between the system components and the coupling pool is not instantaneous. To that end, we model a system of semiconductor lasers optically coupled to a central laser with a delay. Our results show that, even though the lasers are non-identical due to their distinct optical frequencies, zero-lag synchronization arises. By changing a system parameter, we can switch between two different types of synchronization transition. The dependence of the transition with respect to the delay-coupling parameters is studied.",1011.3155v2 2010-11-26,Coupling slot-waveguide cavities for large-scale quantum optical devices,"By offering effective modal volumes significantly less than a cubic wavelength, slot-waveguide cavities offer a new in-road into strong atom-photon coupling in the visible regime. Here we explore two-dimensional arrays of coupled slot cavities which underpin designs for novel quantum emulators and polaritonic quantum phase transition devices. Specifically, we investigate the lateral coupling characteristics of diamond-air and GaP-air slot waveguides using numerically-assisted coupled-mode theory, and the longitudinal coupling properties via distributed Bragg reflectors using mode-propagation simulations. We find that slot-waveguide cavities in the Fabry-Perot arrangement can be coupled and effectively treated with a tight-binding description, and are a suitable platform for realizing Jaynes-Cummings-Hubbard physics.",1011.5690v1 2010-11-29,Quantum dynamics of a dc-SQUID coupled to an asymmetric Cooper pair transistor,"We present a theoretical analysis of the quantum dynamics of a superconducting circuit based on a highly asymmetric Cooper pair transistor (ACPT) in parallel to a dc-SQUID. Starting from the full Hamiltonian we show that the circuit can be modeled as a charge qubit (ACPT) coupled to an anharmonic oscillator (dc-SQUID). Depending on the anharmonicity of the SQUID, the Hamiltonian can be reduced either to one that describes two coupled qubits or to the Jaynes-Cummings Hamiltonian. Here the dc-SQUID can be viewed as a tunable micron-size resonator. The coupling term, which is a combination of a capacitive and a Josephson coupling between the two qubits, can be tuned from the very strong- to the zero-coupling regimes. It describes very precisely the tunable coupling strength measured in this circuit and explains the 'quantronium' as well as the adiabatic quantum transfer read-out.",1011.6148v1 2011-01-04,Search for W'->tb resonances with left- and right-handed couplings to fermions,"We present a search for the production of a heavy gauge boson, W', that decays to third-generation quarks, by the D0 Collaboration in ppbar collisions at sqrt(s)= 1.96 TeV. We set 95% confidence level upper limits on the production cross section times branching fraction. For the first time, we set limits for arbitrary combinations of left- and right-handed couplings of the W' boson to fermions. For couplings with the same strength as the standard model W boson, we set the following limits for M(W') > m(nu_R): M(W')>863 GeV for purely left-handed couplings, M(W')>885 GeV for purely right-handed couplings, and M(W')>916 GeV if both left- and right-handed couplings are present. The limit for right-handed couplings improves for M(W') < m(nu_R) to M(W')>890 GeV.",1101.0806v2 2011-01-25,Quantum phase transitions for two coupled sites with dipole-coupled effective Jaynes-Cummings model,"The nature of the ground states for a system composed of two coupled cavities with each containing a pair of dipole-coupled two-level atoms are studied over a wide range of detunings and dipole coupling strengths. The cases for three limits of exact resonance, large positive and negative detunings are discussed, and four types of the ground states are revealed. Then the phase diagrams of the ground state are plotted by choosing three different ""order parameters"". We find that the phase space, determined by the combinative action of detuning and the dipole coupling strength, is divided into four regions. This is different from the general Bose-Hubbard model and more richer physics are presented in the two-site coupled cavities system. That is, the insulator region may be polaritonic or atomic and the superfluid region may be polaritonic or photonic in nature.",1101.4751v2 2011-01-25,Quantum transport of double quantum dots coupled to an oscillator in arbitrary strong coupling regime,"In this paper, we investigate the quantum transport of a double quantum dot coupled with a nanomechanical resonator at arbitrary strong electron-phonon coupling regimes. We employ the generalized quantum master equation to study full counting statistics of currents. We demonstrate the coherent phonon states method can be applied to decouple the electron-phonon interaction non-perturbatively. With the help of this non-perturbative treatment of electron-phonon couplings, we find that the phonon-assisted resonant tunneling emerges when the excess energy from the left quantum dot to the right one can excite integer number of phonons and multi-phonon excitations can enhance the transport in strong electron-phonon coupling regime. Moreover, we find that as the electron-phonon coupling increases, it first plays a constructive role to assist the transport, and then plays the role of scattering and strongly represses the transport.",1101.4864v2 2011-01-27,Next-to-leading order QCD corrections to the top quark associated with $γ$ production via model-independent flavor-changing neutral-current couplings at hadron colliders,"We present the complete next-to-leading order (NLO) QCD corrections to the top quark associated with $\gamma$ production induced by model-independent $tq\gamma$ and $tqg$ flavor-changing neutral-current (FCNC) couplings at hadron colliders, respectively. We also consider the mixing effects between the $tq\gamma$ and $tqg$ FCNC couplings for this process. Our results show that, for the $tq\gamma$ couplings, the NLO QCD corrections can enhance the total cross sections by about 50% and 40% at the Tevatron and LHC, respectively. Including the contributions from the $tq\gamma$, $tqg$ FCNC couplings and their mixing effects, the NLO QCD corrections can enhance the total cross sections by about 50% for the $tu\gamma$ and $tug$ FCNC couplings, and by about the 80% for the $tc\gamma$ and $tcg$ FCNC couplings at the LHC, respectively. Moreover, the NLO corrections reduce the dependence of the total cross section on the renormalization and factorization scale significantly. We also evaluate the NLO corrections for several important kinematic distributions.",1101.5346v1 2011-02-07,Impact of spin-orbit coupling on the Holstein polaron,"We utilize an exact variational numerical procedure to calculate the ground state properties of a polaron in the presence of a Rashba-like spin orbit interaction. Our results corroborate with previous work performed with the Momentum Average approximation and with weak coupling perturbation theory. We find that spin orbit coupling increases the effective mass in the regime with weak electron phonon coupling, and decreases the effective mass in the intermediate and strong electron phonon coupling regime. Analytical strong coupling perturbation theory results confirm our numerical results in the small polaron regime. A large amount of spin orbit coupling can lead to a significant lowering of the polaron effective mass.",1102.1421v1 2011-02-14,Spatially Coupled Codes over the Multiple Access Channel,"We consider spatially coupled code ensembles over a multiple access channel. Convolutional LDPC ensembles are one instance of spatially coupled codes. It was shown recently that, for transmission over the binary erasure channel, this coupling of individual code ensembles has the effect of increasing the belief propagation threshold of the coupled ensembles to the maximum a-posteriori threshold of the underlying ensemble. In this sense, spatially coupled codes were shown to be capacity achieving. It was observed, empirically, that these codes are universal in the sense that they achieve performance close to the Shannon threshold for any general binary-input memoryless symmetric channels. In this work we provide further evidence of the threshold saturation phenomena when transmitting over a class of multiple access channel. We show, by density evolution analysis and EXIT curves, that the belief propagation threshold of the coupled ensembles is very close to the ultimate Shannon limit.",1102.2856v1 2011-02-22,Spatially-Coupled MacKay-Neal Codes and Hsu-Anastasopoulos Codes,"Kudekar et al. recently proved that for transmission over the binary erasure channel (BEC), spatial coupling of LDPC codes increases the BP threshold of the coupled ensemble to the MAP threshold of the underlying LDPC codes. One major drawback of the capacity-achieving spatially-coupled LDPC codes is that one needs to increase the column and row weight of parity-check matrices of the underlying LDPC codes. It is proved, that Hsu-Anastasopoulos (HA) codes and MacKay-Neal (MN) codes achieve the capacity of memoryless binary-input symmetric-output channels under MAP decoding with bounded column and row weight of the parity-check matrices. The HA codes and the MN codes are dual codes each other. The aim of this paper is to present an empirical evidence that spatially-coupled MN (resp. HA) codes with bounded column and row weight achieve the capacity of the BEC. To this end, we introduce a spatial coupling scheme of MN (resp. HA) codes. By density evolution analysis, we will show that the resulting spatially-coupled MN (resp. HA) codes have the BP threshold close to the Shannon limit.",1102.4612v3 2011-03-31,Resonant energy transfer enhanced by off-diagonal exciton-phonon coupling,"Dynamics of resonant energy transfer of a single excitation in a molecular dimer system is studied in the simultaneous presence of diagonal and off-diagonal exciton-phonon coupling. It is found that the off-diagonal coupling plays an important role in the excitation energy transfer process. Coherent transfer can be found at arbitrary temperature for a non-vanishing off-diagonal coupling strength with an oscillation frequency of site populations that increases with the off-diagonal coupling strength. Furthermore, we identify a threshold of the off-diagonal coupling strength below which there exists an optimal temperature that maximizes the total population transfer from the initially excited monomer to the acceptor monomer at long times. As the off-diagonal coupling strength is increased beyond the threshold, however, the optimal temperature is found to abruptly drop to zero.",1103.6162v2 2011-06-17,Entanglement spectra of coupled S=1/2 spin chains in a ladder geometry,"We study the entanglement spectrum of spin-1/2 XXZ ladders both analytically and numerically. Our analytical approach is based on perturbation theory starting either from the limit of strong rung coupling, or from the opposite case of dominant coupling along the legs. In the former case we find to leading order that the entanglement Hamiltonian is also of nearest-neighbor XXZ form although with an in general renormalized anisotropy. For the cases of XX and isotropic Heisenberg ladders no such renormalization takes place. In the Heisenberg case the second order correction to the entanglement Hamiltonian consists of a renormalization of the nearest neighbor coupling plus an unfrustrated next nearest neighbor coupling. In the opposite regime of strong coupling along the legs, we point out an interesting connection of the entanglement spectrum to the Lehmann representation of single chain spectral functions of operators appearing in the physical Hamiltonian coupling the two chains.",1106.3419v2 2011-09-02,Half-turn symmetric FPLs with rare couplings and tilings of hexagons,"In this work, we put to light a formula that relies the number of fully packed loop configurations (FPLs) associated to a given coupling pi to the number of half-turn symmetric FPLs (HTFPLs) of even size whose coupling is a punctured version of the coupling pi. When the coupling pi is the coupling with all arches parallel pi0 (the ""rarest"" one), this formula states the equality of the number of corresponding HTFPLs to the number of cyclically-symmetric plane partition of the same size. We provide a bijective proof of this fact. In the case of HTFPLs odd size, and although there is no similar expression, we study the number of HTFPLs whose coupling is a slit version of pi_0, and put to light new puzzling enumerative coincidence involving countings of tilings of hexagons and various symmetry classes of FPLs.",1109.0366v1 2011-10-05,Molecule Induced Strong Exchange Coupling between Ferromagnetic Electrodes of a Magnetic Tunnel Junction,"Multilayer edge molecular spintronics device (MEMSD) approach can produce novel logic and memory units for the computers. MEMSD are produced by bridging the molecular channels across the insulator, in the exposed edge region(s) of a magnetic tunnel junction (MTJ). The bridged molecular channels start serving as the dominant exchange coupling medium between the two ferromagnetic electrodes of a MTJ. Present study focus on the effect of molecule enhanced exchange coupling on the magnetic properties of the MTJ. This paper shows that organometallic molecular clusters (OMCs) strongly increased the magnetic coupling between the two ferromagnetic electrodes. SQUID magnetometer showed that OMCs transformed the typical hysteresis magnetization curve of a Co/NiFe/AlOx/NiFe MTJ into linear one. Ferromagnetic resonance studies showed that OMC bridges affected the two fundamental resonance peaks of the Co/NiFe/AlOx/NiFe MTJ. According to magnetic force microscopy, OMCs caused the disappearance of magnetic contrast from the Co/NiFe/AlOx/NiFe tunnel junction area. These three independent and complimentary experiments, suggested the development of extremely strong interlayer exchange coupling. This work delineated a practical route to control the exchange coupling between ferromagnetic electrodes. Ability to tailor magnetic coupling can lead to the development of molecule based quantum computation device architecture.",1110.0885v1 2011-10-24,Oscillatory coupling between a monolithic whispering-gallery resonator and a buried bus waveguide,"We report on a combined theoretical and experimental study of the optical coupling between a microdisk resonator and a waveguide laying on different planes. While the lateral coupling between a planar resonator and a waveguide is characterized by a unique distance at which the resonant waveguide transmission vanishes because of destructive interference, the vertical coupling geometry exhibits an oscillatory behavior in the coupling amplitude as a function of the vertical gap. This effect manifests experimentally as oscillations in both the waveguide transmission and the mode quality factor. An analytical description based on coupled-mode theory and a two-port beam-splitter model of the waveguide-resonator coupling is developed, which compares successfully both to experimental data and numerical simulations.",1110.5211v1 2011-10-31,Spin-Orbit Coupled Quantum Gases,"In this review we will discuss the experimental and theoretical progresses in studying spin-orbit coupled degenerate atomic gases during the last two years. We shall first review a series of pioneering experiments in generating synthetic gauge potentials and spin-orbit coupling in atomic gases by engineering atom-light interaction. Realization of spin-orbit coupled quantum gases opens a new avenue in cold atom physics, and also brings out a lot of new physical problems. In particular, the interplay between spin-orbit coupling and inter-atomic interaction leads to many intriguing phenomena. Here, by reviewing recent theoretical studies of both interacting bosons and fermions with isotropic Rashba spin-orbit coupling, the key message delivered here is that spin-orbit coupling can enhance the interaction effects, and make the interaction effects much more dramatic even in the weakly interacting regime.",1110.6798v1 2011-12-20,Transition from spatial coherence to incoherence in coupled chaotic systems,"We investigate the spatio-temporal dynamics of coupled chaotic systems with nonlocal interactions, where each element is coupled to its nearest neighbors within a finite range. Depending upon the coupling strength and coupling radius, we find characteristic spatial patterns such as wave-like profiles and study the transition from coherence to incoherence leading to spatial chaos. We analyze the origin of this transition based on numerical simulations and support the results by theoretical derivations identifying a critical coupling strength and a scaling relation of the coherent profiles. To demonstrate the universality of our findings we consider time-discrete as well as time-continuous chaotic models realized as logistic map and R\""ossler or Lorenz system, respectively. Thereby we establish the coherence-incoherence transition in networks of coupled identical oscillators.",1112.4869v2 2012-03-06,Short-range correlations in dilute atomic Fermi gases with spin-orbit coupling,"We study the short-range correlation strength of three dimensional spin half dilute atomic Fermi gases with spin-orbit coupling. The interatomic interaction is modeled by the contact pseudopotential. In the high temperature limit, we derive the expression for the second order virial expansion of the thermodynamic potential via the ladder diagrams. We further evaluate the second order virial expansion in the limit that the spin-orbit coupling constants are small, and find that the correlation strength between the fermions increases as the forth power of the spin-orbit coupling constants. At zero temperature, we consider the cases in which there are symmetric spin-orbit couplings in two or three directions. In such cases, there is always a two-body bound state of zero net momentum. In the limit that the average interparticle distance is much larger than the dimension of the two-body bound state, the system primarily consists of condensed bosonic molecules that fermions pair to form; we find that the correlation strength also becomes bigger compared to that in the absence of spin-orbit coupling. Our results indicate that generic spin-orbit coupling enhances the short-range correlations of the Fermi gases. Measurement of such enhancement by photoassociation experiment is also discussed.",1203.1159v1 2012-06-01,Coupling techniques for nonlinear hyperbolic equations. IV. Multi-component coupling and multidimensional well-balanced schemes,"This series of papers is devoted to the formulation and the approximation of coupling problems for nonlinear hyperbolic equations. The coupling across an interface in the physical space is formulated in term of an augmented system of partial differential equations. In an earlier work, this strategy allowed us to develop a regularization method based on a thick interface model in one space variable. In the present paper, we significantly extend this framework and, in addition, encompass equations in several space variables. This new formulation includes the coupling of several distinct conservation laws and allows for a possible covering in space. Our main contributions are, on one hand, the design and analysis of a well-balanced finite volume method on general triangulations and, on the other hand, a proof of convergence of this method toward entropy solutions, extending Coquel, Cockburn, and LeFloch's theory (restricted to a single conservation law without coupling). The core of our analysis is, first, the derivation of entropy inequalities as well as a discrete entropy dissipation estimate and, second, a proof of convergence toward the entropy solution of the coupling problem.",1206.0248v1 2012-06-04,Microcavity controlled coupling of excitonic qubits,"Controlled non-local energy and coherence transfer enables light harvesting in photosynthesis and non-local logical operations in quantum computing. The most relevant mechanism of coherent coupling of distant qubits is coupling via the electromagnetic field. Here, we demonstrate the controlled coherent coupling of spatially separated excitonic qubits via the photon mode of a solid state microresonator. This is revealed by two-dimensional spectroscopy of the sample's coherent response, a sensitive and selective probe of the coherent coupling. The experimental results are quantitatively described by a rigorous theory of the cavity mediated coupling within a cluster of quantum dots excitons. Having demonstrated this mechanism, it can be used in extended coupling channels - sculptured, for instance, in photonic crystal cavities - to enable a long-range, non-local wiring up of individual emitters in solids.",1206.0592v1 2012-07-04,Superpotential de-sequestering in string models,"Non-perturbative superpotential cross-couplings between visible sector matter and K\""ahler moduli can lead to significant flavour-changing neutral currents in compactifications of type IIB string theory. Here, we compute corrections to Yukawa couplings in orbifold models with chiral matter localised on D3-branes and non-perturbative effects on distant D7-branes. By evaluating a threshold correction to the D7-brane gauge coupling, we determine conditions under which the non-perturbative corrections to the Yukawa couplings appear. The flavour structure of the induced Yukawa coupling generically fails to be aligned with the tree-flavour structure. We check our results by also evaluating a correlation function of two D7-brane gauginos and a D3-brane Yukawa coupling. Finally, by calculating a string amplitude between n hidden scalars and visible matter we show how non-vanishing vacuum expectation values of distant D7-brane scalars, if present, may correct visible Yukawa couplings with a flavour structure that differs from the tree-level flavour structure.",1207.1103v1 2012-07-10,Half--Hypers and Quivers,"We study systematically the BPS spectra of N=2 SYM coupled to half--hypermultiplets, the basic example being E_7 SYM coupled to a half--hyper in the 56 irrepr. In order to do this, we determine the BPS quivers with superpotential of such N=2 models using a new technique we introduce. The computation of the BPS spectra in the various chambers is then reduced to the Representation Theory of the resulting quivers. We use the quiver description to study the BPS spectrum at both strong and weak coupling. The following models are discussed in detail: SU(6) SYM coupled to a half 20, SO(12) SYM coupled to a half 32, and E_7 SYM coupled to a half 56. For models with gauge group SU(2) x SO(2n) and matter in the half (2,2n) we find strongly coupled chambers with a BPS spectrum consisting of just finitely many hypermultiplets.",1207.2275v1 2012-07-25,High cooperativity in coupled microwave resonator ferrimagnetic insulator hybrids,"We report the observation of strong coupling between the exchange-coupled spins in gallium-doped yttrium iron garnet and a superconducting coplanar microwave resonator made from Nb. The measured coupling rate of 450 MHz is proportional to the square-root of the number of exchange-coupled spins and well exceeds the loss rate of 50 MHz of the spin system. This demonstrates that exchange coupled systems are suitable for cavity quantum electrodynamics experiments, while allowing high integration densities due to their extraordinary high spin densities. Our results furthermore show, that experiments with multiple exchange-coupled spin systems interacting via a single resonator are within reach.",1207.6039v2 2012-08-28,Spin-orbit coupled particle in a spin bath,"We consider a spin-orbit coupled particle confined in a quantum dot in a bath of impurity spins. We investigate the consequences of spin-orbit coupling on the interactions that the particle mediates in the spin bath. We show that in the presence of spin-orbit coupling, the impurity-impurity interactions are no longer spin-conserving. We quantify the degree of this symmetry breaking and show how it relates to the spin-orbit coupling strength. We identify several ways how the impurity ensemble can in this way relax its spin by coupling to phonons. A typical resulting relaxation rate for a self-assembled Mn-doped ZnTe quantum dot populated by a hole is 1 $\mu$s. We also show that decoherence arising from nuclear spins in lateral quantum dots is still removable by a spin echo protocol, even if the confined electron is spin-orbit coupled.",1208.5606v1 2012-08-29,Modified Bethe-Peierls boundary condition for ultracold atoms with Spin-Orbit coupling,"We show that the Bethe-Peierls (BP) boundary condition should be modified for ultracold atoms with spin-orbit (SO) coupling. Moreover, we derive a general form of the modified BP boundary condition, which is applicable to a system with arbitrary kind of SO coupling. In the modified BP condition, an anisotropic term appears and the inter-atomic scattering length is normally SO-coupling dependent. For the special system in the current experiments, however, it can be proved that the scattering length is SO-coupling independent, and takes the same value as in the case without SO coupling. Our result is helpful for the study of both few-body and many-body physics in SO-coupled ultracold gases.",1208.5976v4 2012-09-22,Heat flow in InAs/InP heterostructure nanowires,"The transfer of heat between electrons and phonons plays a key role for thermal management in future nanowire-based devices, but only a few experimental measurements of electron-phonon (e-ph) coupling in nanowires are available. Here, we combine experimental temperature measurements on an InAs/InP heterostructure nanowire system with finite element modeling (FEM) to extract information on heat flow mediated by e-ph coupling. We find that the electron and phonon temperatures in our system are highly coupled even at temperatures as low as 2 K. Additionally, we find evidence that the usual power-law temperature dependence of electron-phonon coupling may not correctly describe the coupling in nanowires and show that this result is consistent with previous research on similar one-dimensional electron systems. We also compare the strength of the observed e-ph coupling to a theoretical analysis of e-ph interaction in InAs nanowires, which predicts a significantly weaker coupling strength than observed experimentally.",1209.4940v1 2012-10-16,Baryon asymmetry and dark matter from soft leptogenesis,"The framework for soft leptogenesis minimally extended with a DM sector is studied. A heavy singlet neutrino superfield acts as the source for (s)lepton asymmetry and by coupling to the singlet DM superfield it produces a DM particle density through decays. The nature of DM generated is twofold depending on whether the Yukawa and DM couplings are either small or large. With sufficiently small Yukawa and DM couplings DM annihilations into MSSM particles are slow and as a consequence all DM particles form the DM component. The solutions to Boltzmann equations are given and the dependence between the DM masses and coupling are presented in this weak coupling regime. Also, the behavior of the efficiency of producing asymmetric DM is determined with weak couplings. We note that a different outcome arises if the couplings are larger because then the ADM component is dominant due to the effectiveness of DM decays into the MSSM sector.",1210.4335v3 2012-11-11,Channel coupling effect and important role of imaginary part of coupling potential for high-energy heavy-ion scatterings,"The recent works by the present authors and their collaborator predicted that the real part of heavy-ion optical potentials changes its character from attraction to repulsion around the incident energy per nucleon $E =$ 200 -- 300 MeV/u on the basis of the complex $G$-matrix interaction and the double-folding model (DFM) and revealed that the three-body force plays an important role there. In the present paper, we have analyzed the energy dependence of the coupling effect with the Microscopic Coupled Channel (MCC) method and its relation to the elastic and inelastic-scattering angular distributions in detail in the case of the $^{12}$C + $^{12}$C system in the energy range of $E =$ 100 -- 400 MeV/u. The large channel coupling effect is clearly seen in the elastic cross section although the incident energies are enough high. The dynamical polarization potential is derived to investigate the channel coupling effect. Moreover, we analyze the effect of imaginary part of the coupling potential on elastic and inelastic cross sections.",1211.2480v2 2012-12-03,Normal state properties of spin-orbit coupled Fermi gases in the upper branch of energy spectrum,"We investigate normal state properties of spin-orbit coupled Fermi gases with repulsive s-wave interaction, in the absence of molecule formation, i.e., in the so-called ""upper branch"". Within the framework of random phase approximation, we derive analytical expressions for the quasi-particle lifetime $\tau_s$, the effective mass $m_s^*$, and the Green's function renormalization factor $Z_s$ in the presence of Rashba spin-orbit coupling. In contrast to spin-orbit coupled electron gas with Coulomb interaction, we show that the modifications are dependent on the Rashba band index s, and occur in the first order of the spin-orbit coupling strength. We also calculate experimental observable such as spectral weight, density of state and specific heat, which exhibit significant differences from their counterparts without spin-orbit coupling. We expect our microscopic calculations of these Fermi liquid parameters would have the immediate applications to the spin-orbit coupled Fermi gases in the upper branch of the energy spectrum.",1212.0420v5 2013-01-24,Overview of large N QCD with chemical potential at weak and strong coupling,"In this note we summarize the results from a longer article on obtaining the QCD phase diagram as a function of the temperature and chemical potential at large Nc and large Nf in the weak and the strong coupling limits. The weak coupling phase diagram is obtained from the Polyakov line order parameter, and the quark number, calculated using 1-loop perturbation theory for QCD formulated on S^1 x S^3. The strong coupling phase diagram is obtained from the same observables calculated at leading order in the lattice strong coupling and hopping parameter expansions. We show that the matrix models in these two limits agree at temperatures and chemical potentials which are not too high, such that observables in the strongly-coupled theory can be obtained from the observables in the weakly-coupled theory, and vice versa, using a simple transformation of variables.",1301.5750v1 2013-02-15,Going beyond the linear approximation in describing electron- phonon coupling: relevance for the Holstein model,"Using the momentum average approximation we study the importance of adding higher-than-linear terms in the electron-phonon coupling on the properties of single polarons described by a generalized Holstein model. For medium and strong linear coupling, even small quadratic electron-phonon coupling terms are found to lead to very significant quantitative changes in the properties of the polaron, which cannot be captured by a linear Holstein Hamiltonian with renormalized parameters. We argue that the bi-polaron phase diagram is equally sensitive to addition of quadratic coupling terms if the linear coupling is large. These results suggest that the linear approximation is likely to be inappropriate to model systems with strong electron-phonon coupling, at least for low carrier concentrations.",1302.3843v2 2013-03-07,Constraints on Disformal Couplings from the Properties of the Cosmic Microwave Background Radiation,"Certain modified gravity theories predict the existence of an additional, non-conformally coupled scalar field. A disformal coupling of the field to the Cosmic Microwave Background (CMB) is shown to affect the evolution of the energy density in the radiation fluid and produces a modification of the distribution function of the CMB, which vanishes if photons and baryons couple in the same way to the scalar. We find the constraints on the couplings to matter and photons coming from the measurement of the CMB temperature evolution and from current upper limits on the $\mu$--distortion of the CMB spectrum. We also point out that the measured equation of state of photons differs from $w_\gamma = 1/3$ in the presence of disformal couplings.",1303.1773v3 2013-04-05,Direct constraints on the top-Higgs coupling from the 8 TeV LHC data,"The LHC experiments have analyzed the 7 and 8 TeV LHC data in the main Higgs production and decay modes. Current analyses only loosely constrain an anomalous top-Higgs coupling in a direct way. In order to strongly constrain this coupling, the Higgs-top associated production is reanalyzed. Thanks to the strong destructive interference in the t-channel for standard model couplings, this process can be very sensitive to both the magnitude and the sign of a non-standard top-Higgs coupling. We project the sensitivity to anomalous couplings to the integrated luminosity of 50 fb^{-1}, corresponding to the data collected by the ATLAS and CMS experiments in 7 and 8 TeV collisions, as of 2012. We show that the combination of di-photon and multi-lepton signatures, originating from different combinations of the top and Higgs decay modes, can be a potential probe to constrain a large portion of the negative top-Higgs coupling space presently allowed by the ATLAS and CMS global fits.",1304.1822v2 2013-04-11,Large spin-orbit coupling in carbon nanotubes,"It has recently been recognized that the strong spin-orbit interaction present in solids can lead to new phenomena, such as materials with non-trivial topological order. Although the atomic spin-orbit coupling in carbon is weak, the spin-orbit coupling in carbon nanotubes can be significant due to their curved surface. Previous works have reported spin-orbit couplings in reasonable agreement with theory, and this coupling strength has formed the basis of a large number of theoretical proposals. Here we report a spin-orbit coupling in three carbon nanotube devices that is an order of magnitude larger than measured before. We find a zero-field spin splitting of up to 3.4 meV, corresponding to a built-in effective magnetic field of 29 T aligned along the nanotube axis. While the origin of the large spin-orbit coupling is not explained by existing theories, its strength is promising for applications of the spin-orbit interaction in carbon nanotubes devices.",1304.3234v1 2013-04-26,New constraints on Coupled Dark Energy from Planck,"We present new constraints on coupled dark energy from the recent measurements of the Cosmic Microwave Background Anisotropies from the Planck satellite mission. We found that a coupled dark energy model is fully compatible with the Planck measurements, deriving a weak bound on the dark matter-dark energy coupling parameter \xi=-0.49^{+0.19}_{-0.31} at 68% c.l.. Moreover if Planck data are fitted to a coupled dark energy scenario, the constraint on the Hubble constant is relaxed to H_0=72.1^{+3.2}_{-2.3} km/s/Mpc, solving the tension with the Hubble Space Telescope value. We show that a combined Planck+HST analysis provides significant evidence for coupled dark energy finding a non-zero value for the coupling parameter \xi, with -0.90< \xi <-0.22 at 95% c.l.. We also consider the combined constraints from the Planck data plus the BAO measurements of the 6dF Galaxy Survey, the Sloan Digital Sky Survey and the Baron Oscillation Spectroscopic Survey.",1304.7119v3 2013-05-06,Halo Coupling and Cleaning by a Space Charge Resonance in High Intensity Beams,"We show that the difference resonance driven by the space charge pseudo-octupole of high-intensity beams not only couples the beam core emittances; it can also lead to emittance exchange in the beam halo, which is of relevance for beam loss in high intensity accelerators. With reference to linear accelerators the ""main resonance"" kz/kxy =1 (corresponding to the Montague resonance 2Qx-2Qy=0 in circular accelerators) may lead to such a coupling and transfer of halo between planes. Coupling of transverse halo into the longitudinal plane - or vice versa - can occur even if the core (rms) emittances are exactly or nearly equal. This halo argument justifies additional caution in linac design including consideration of avoiding an equipartitioned design. At the same time, however, this mechanism may also qualify as active dynamical halo cleaning scheme by coupling a halo from the longitudinal plane into the transverse plane, where local scraping is accessible. We present semi-analytical emittance coupling rates and show that previously developed linac stability charts for the core can be extended - using the longitudinal to transverse halo emittance ratio - to indicate additional regions where halo coupling could be of importance.",1305.1271v2 2013-05-28,Strong coupling of optical nanoantennas and atomic systems,"An optical nanoantenna and adjacent atomic systems are strongly coupled when an excitation is repeatedly exchanged between these subsystems prior to its eventual dissipation into the environment. It remains challenging to reach the strong coupling regime but it is equally rewarding. Once being achieved, promising applications as signal processing at the nanoscale and at the single photon level would immediately come into reach. Here, we study such hybrid configuration from different perspectives. The configuration we consider consists of two identical atomic systems, described in a two-level approximation, which are strongly coupled to an optical nanoantenna. First, we investigate when this hybrid system requires a fully quantum description and provide a simple analytical criterion. Second, a design for a nanoantenna is presented that enables the strong coupling regime. Besides a vivid time evolution, the strong coupling is documented in experimentally accessible quantities, such as the extinction spectra. The latter are shown to be strongly modified if the hybrid system is weakly driven and operates in the quantum regime. We find that the extinction spectra depend sensitively on the number of atomic systems coupled to the nanoantenna.",1305.6427v2 2013-07-16,Vortex molecules in Bose-Einstein condensates,"Stable vortex dimers are known to exist in coherently coupled two component Bose-Einstein condensates (BECs). We construct stable vortex trimers in three component BECs and find that the shape can be controlled by changing the internal coherent (Rabi) couplings. Stable vortex N-omers are also constructed in coherently coupled N-component BECs. We classify all possible N-omers in terms of the mathematical graph theory. Next, we study effects of the Rabi coupling in vortex lattices in two-component BECs. We find how the vortex lattices without the Rabi coupling known before are connected to the Abrikosov lattice of integer vortices with increasing the Rabi coupling. In this process, vortex dimers change their partners in various ways at large couplings. We then find that the Abrikosov lattices are robust in three-component BECs.",1307.4312v1 2013-10-06,Sub-Ohmic spin-boson model with off-diagonal coupling: Ground state properties,"We have carried out analytical and numerical studies of the spin-boson model in the sub-ohmic regime with the influence of both the diagonal and off-diagonal coupling accounted for via the Davydov D1 variational ansatz. While a second-order phase transition is known to be exhibited by this model in the presence of diagonal coupling only, we demonstrate the emergence of a discontinuous first order phase transition upon incorporation of the off-diagonal coupling. A plot of the ground state energy versus magnetization highlights the discontinuous nature of the transition between the isotropic (zero magnetization) state and nematic (finite magnetization) phases. We have also calculated the entanglement entropy and a discontinuity found at a critical coupling strength further supports the discontinuous crossover in the spin-boson model in the presence of off-diagonal coupling. It is further revealed via a canonical transformation approach that for the special case of identical exponents for the spectral densities of the diagonal and the off-diagonal coupling, there exists a continuous crossover from a single localized phase to doubly degenerate localized phase with differing magnetizations.",1310.1548v1 2013-10-15,Complexity and asymptotic stability in the process of biochemical substance exchange in a coupled ring of cells,"We have considered the complexity and asymptotic stability in the process of biochemical substance exchange in a coupled ring of cells. We have used coupled maps to model this process. It includes the coupling parameter, cell affinity and environmental factor as master parameters of the model. We have introduced: (i) the Kolmogorov complexity spectrum and (ii) the Kolmogorov complexity spectrum highest value to analyze the dynamics of two cell model. The asymptotic stability of this dynamical system using an eigenvalue-based method has been considered. Using these complexity measures we have noticed an 'island' of low complexity in the space of the master parameters for the weak coupling. We have explored how stability of the equilibrium of the biochemical substance exchange in a multi-cell system (N=100) is influenced by the changes in the master parameters of the model for the weak and strong coupling. We have found that in highly chaotic conditions there exists space of master parameters for which the process of biochemical substance exchange in a coupled ring of cells is stable.",1310.3942v1 2013-11-11,Coupling layers regularizes wave propagation in laminar stochastic neural fields,"We study the effects of coupling between layers of stochastic neural field models with laminar structure. In particular, we focus on how the propagation of waves of neural activity in each layer is affected by the coupling. Synaptic connectivities within and between each layer are determined by integral kernels of an integrodifferential equation describing the temporal evolution of neural activity. Excitatory neural fields, with purely positive connectivities, support traveling fronts in each layer, whose speeds are increased when coupling between layers is considered. Studying the effects of noise, we find coupling also serves to reduce the variance in the position of traveling fronts, as long as the noise sources to each layer are not completely correlated. Neural fields with asymmetric connectivity support traveling pulses whose speeds are decreased by interlaminar coupling. Again, coupling reduces the variance in traveling pulse position, when noise is considered that is not totally correlated between layers. To derive our stochastic results, we employ a small-noise expansion, also assuming interlaminar connectivity scales similarly. Our asymptotic results agree reasonably with accompanying numerical simulations.",1311.2607v1 2013-11-22,Transition in coupled replicas may not imply a finite temperature ideal glass transition in glass forming systems,"A key open question in the glass transition field is whether a finite temperature thermodynamic transition to the glass state exists or not. Recent simulations of coupled replicas in atomistic models have found signatures of a static transition as a function of replica coupling. This can be viewed as evidence of an associated thermodynamic glass transition in the uncoupled system. We demonstrate here that a different interpretation is possible. We consider the triangular plaquette model, an interacting spin system which displays (East model-like) glassy dynamics in the absence of any static transition. We show that when two replicas are coupled there is a curve of equilibrium phase transitions, between phases of small and large overlap, in the temperature-coupling plane (located on the self-dual line of an exact temperature/coupling duality of the system) which ends at a critical point. Crucially, in the limit of vanishing coupling the finite temperature transition disappears, and the uncoupled system is in the disordered phase at all temperatures. We discuss interpretation of atomistic simulations in light of this result.",1311.5827v1 2013-12-08,Scalable and Quasi-Contractive Markov Coupling of Maxwell Collision,"This paper considers space homogenous Boltzmann kinetic equations in dimension $d$ with Maxwell collisions (and without Grad's cut-off). An explicit Markov coupling of the associated conservative (Nanbu) stochastic $N$-particle system is constructed, using plain parallel coupling of isotropic random walks on the sphere of two-body collisional directions. The resulting coupling is almost surely decreasing, and the $L_2$-coupling creation is computed explicitly. Some quasi-contractive and uniform in $N$ coupling / coupling creation inequalities are then proved, relying on $2+\alpha$-moments ($\alpha >0$) of velocity distributions; upon $N$-uniform propagation of moments of the particle system, it yields a $N$-scalable $\alpha$-power law trend to equilibrium. The latter are based on an original sharp inequality, which bounds from above the coupling distance of two centered and normalized random variables $(U,V)$ in $\R^d$, with the average square parallelogram area spanned by $(U-U_\ast,V-V_\ast)$, $(U_\ast,V_\ast)$ denoting an independent copy. Two counter-examples proving the necessity of the dependance on $>2$-moments and the impossibility of strict contractivity are provided. The paper, (mostly) self-contained, does not require any propagation of chaos property and uses only elementary tools.",1312.2253v3 2013-12-12,Nonlinear modes and symmetries in linearly-coupled pairs of PT-invariant dimers,"The subject of the work are pairs of linearly coupled PT-symmetric dimers. Two different settings are introduced, namely, straight-coupled dimers, where each gain site is linearly coupled to one gain and one loss site, and cross-coupled dimers, with each gain site coupled to two lossy ones. The latter pair with equal coupling coefficients represents a ""PT-hypersymmetric"" quadrimer. We find symmetric and antisymmetric solutions in these systems, chiefly in an analytical form, and explore the existence, stability and dynamical behavior of such solutions by means of numerical methods. We thus identify bifurcations occurring in the systems, including spontaneous symmetry breaking and saddle-center bifurcations. Simulations demonstrate that evolution of unstable branches typically leads to blowup. However, in some cases unstable modes rearrange into stable ones.",1312.3376v1 2014-01-02,Traffic congestion in interconnected complex networks,"Traffic congestion in isolated complex networks has been investigated extensively over the last decade. Coupled network models have recently been developed to facilitate further understanding of real complex systems. Analysis of traffic congestion in coupled complex networks, however, is still relatively unexplored. In this paper, we try to explore the effect of interconnections on traffic congestion in interconnected BA scale-free networks. We find that assortative coupling can alleviate traffic congestion more readily than disassortative and random coupling when the node processing capacity is allocated based on node usage probability. Furthermore, the optimal coupling probability can be found for assortative coupling. However, three types of coupling preferences achieve similar traffic performance if all nodes share the same processing capacity. We analyze interconnected Internet AS-level graphs of South Korea and Japan and obtain similar results. Some practical suggestions are presented to optimize such real-world interconnected networks accordingly.",1401.0412v2 2014-01-03,Generalized Coupled-line All-Pass Phasers,"Generalized coupled-line all-pass phasers, based on transversally-cascaded (TC), longitudinally-cascaded (LC) and hybrid-cascaded (HC) coupled transmission line sections, are presented and demonstrated using analytical, full-wave and experimental results. It is shown that for N commensurate coupled-line sections, LC and TC phasers exhibit N group delay peaks per coupled-line section harmonic frequency band, in contrast to the TC configuration, which exhibits only one peak within this band. It is also shown that for a given maximum achievable coupling-coefficient, the HC configuration provides the largest group delay swing. A wave-interference analysis is finally applied to the various coupled-line phasers, explaining their unique group delay characteristics based on physical wave-propagation mechanisms.",1401.0676v1 2014-01-14,Coupling spin ensembles via superconducting flux qubits,"We study a hybrid quantum system consisting of spin ensembles and superconducting flux qubits, where each spin ensemble is realized using the nitrogen-vacancy centers in a diamond crystal and the nearest-neighbor spin ensembles are effectively coupled via a flux qubit.We show that the coupling strengths between flux qubits and spin ensembles can reach the strong and even ultrastrong coupling regimes by either engineering the hybrid structure in advance or tuning the excitation frequencies of spin ensembles via external magnetic fields. When extending the hybrid structure to an array with equal coupling strengths, we find that in the strong-coupling regime, the hybrid array is reduced to a tight-binding model of a one-dimensional bosonic lattice. In the ultrastrong-coupling regime, it exhibits quasiparticle excitations separated from the ground state by an energy gap. Moreover, these quasiparticle excitations and the ground state are stable under a certain condition that is tunable via the external magnetic field. This may provide an experimentally accessible method to probe the instability of the system.",1401.3095v2 2014-01-14,Dynamics of reaction-diffusion patterns controlled by asymmetric nonlocal coupling as limiting case of differential advection,"A one-component bistable reaction-diffusion system with asymmetric nonlocal coup ling is derived as limiting case of a two-component activator-inhibitor reaction -diffusion model with differential advection. The effects of asymmetric nonlocal couplings in such a bistable reaction-diffusi on system are then compared to the previously studied case of a system with symm etric nonlocal coupling. We carry out a linear stability analysis of the spatially homogeneous steady sta tes of the model and numerical simulations of the model to show how the asymmetr ic nonlocal coupling controls and alters the steady states and the front dynamic s in the system. In a second step, a third fast reaction-diffusion equation is included which ind uces the formation of more complex patterns. A linear stability analysis predicts traveling waves for asymmetric nonlocal coupling in contrast to a stationary Turing patterns for a system with symmetric nonlocal coupling. These findings are verified by direct numerical integration of the full equations with nonlocal coupling.",1401.3111v4 2014-01-20,"Fast dynamics and spectral properties of a multilongitudinal-mode semiconductor laser: evolution of an ensemble of driven, globally coupled nonlinear modes","We analyze the fast transient dynamics of a multi-longitudinal mode semiconductor laser on the basis of a model with intensity coupling. The dynamics, coupled to the constraints of the system and the below-threshold initial conditions, imposes a faster growth of the side modes in the initial stages of the transient, thereby leading the laser through a sequence of states where the modal intensity distribution dramatically differs from the asymptotic one. A detailed analysis of the below-threshold, deterministic dynamical evolution allows us to explain the modal dynamics in the strongly coupled regime where the total intensity peak and relaxation oscillations take place, thus providing an explanation for the modal dynamics observed in the slow, hidden evolution towards the asymptotic state (cf. Phys. Rev. A 85, 043823 (2012)). The dynamics of this system can be interpreted as the transient response of a driven, globally coupled ensemble of nonlinear modes evolving towards an equilibrium state. Since the qualitative dynamics do not depend on the details of the interaction but only on the structure of the coupling, our results hold for a whole class of globally, bilinearly coupled oscillators.",1401.4947v1 2014-04-09,Mechanisms of Electromechanical Coupling in Strain Based Scanning Probe Microscopy,"Electromechanical coupling is ubiquitous in nature and underpins the functionality of materials and systems as diverse as ferroelectric and multiferroic materials, electrochemical devices, and biological systems, and strain-based scanning probe microscopy (s-SPM) techniques have emerged as a powerful tool in characterizing and manipulating electromechanical coupling at the nanoscale. Uncovering underlying mechanisms of electromechanical coupling in these diverse materials and systems, however, is a difficult outstanding problem, and questions and confusions arise from recent experiment observations of electromechanical coupling and its apparent polarity switching in some unexpected materials. We propose a series of s-SPM experiments to identify different microscopic mechanisms underpinning electromechanical coupling, and demonstrate their feasibility using three representative materials. By employing a combination of spectroscopic studies and different modes of s-SPM, we show that it is possible to distinguish electromechanical coupling arising from spontaneous polarization, induced dipole moment, and ionic Vegard strain, and this offer a clear guidance on using s-SPM to study a wide variety of functional materials and systems.",1404.2369v1 2014-04-22,Capacitative coupling of singlet-triplet qubits in different inter-qubit geometries,"In the singlet-triplet qubit architecture, the two-qubit interactions required in universal quantum computing can be implemented by capacitative coupling, by exploiting the charge distribution differences of the singlet and triplet states. The efficiency of this scheme is limited by decoherence, that can be mitigated by stronger coupling between the qubits. In this paper, we study the capacitative coupling of singlet-triplet qubits in different geometries of the two-qubit system. The effects of the qubit-qubit distance and the relative orientation of the qubits on the capacitative coupling strength are discussed using an accurate microscopic model and exact diagonalization of it. We find that the trapezoidal quantum dot formations allow strong coupling with low charge distribution differences between the singlet and triplet states. The analysis of geometry on the capacitative coupling is also extended to the many-qubit case and the creation of cluster states.",1404.5420v1 2014-07-01,Quasi-equilibrium relaxation of two identical quantum oscillators with arbitrary coupling strength,"The paper deals with the problem of open systems out of equilibrium. An analytical expression for time-dependent density matrix of two arbitrary coupled identical quantum oscillators interacting with separate reservoirs is derived using path integral methods. The temporal behavior of spatial variances and of covariance from given initial values up to stationary values is investigated. It was shown that at comparatively low coupling strengths the asymptotic variances in the long-time limit achieve steady states despite on initial conditions. Stationary values of variances differ from the case of total equilibrium due to their coupling simultaneously with thermal reservoirs of different temperatures. The larger the difference in temperatures of thermal baths, the larger is the difference of the stationary values of variances of coupled oscillators comparing with values given by the fluctuation dissipation theorem. At strong couplings the variances have divergent character. Otherwise, in the weak coupling limit the asymptotic stationary variances are always in accordance with the fluctuation dissipation theorem despite of the difference in temperatures within the whole system.",1407.0129v1 2014-08-27,Spin-orbit Coupling and Multiple Phases in Spin-triplet Superconductor Sr$_2$RuO$_4$,"We study the spin-orbit coupling in spin-triplet Cooper pairs and clarify multiple superconducting (SC) phases in Sr$_2$RuO$_4$. Based on the analysis of the three-orbital Hubbard model with atomic LS coupling, we show some selection rules of the spin-orbit coupling in Cooper pairs. The spin-orbit coupling is small when the two-dimensional $\gamma$-band is the main cause of the superconductivity, although the LS coupling is much larger than the SC gap. Considering this case, we investigate multiple SC transitions in the magnetic fields for both H // [001] and H // [100] using the Ginzburg-Landau theory and the quasi-classical theory. Rich phase diagrams are obtained because the spin degree of freedom in Cooper pairs is not quenched by the spin-orbit coupling. Experimental indications for the multiple phases in Sr$_2$RuO$_4$ are discussed.",1408.6353v1 2014-09-12,Ghosts & Matter Couplings in Massive (bi-&multi-)Gravity,"Recently, several works have investigated the coupling to matter in ghost-free massive (bi-&multi-)gravity and a new effective coupling to matter has been proposed. In this note we clarify some confusion on the existence and the implications of a ghost above the strong coupling scale. We confirm that the standard constraint which is otherwise typically present in this type of theories disappears on generic backgrounds as soon as this new coupling is considered. This implies the re-emergence of the Boulware-Deser ghost. Nevertheless the absence of ghost in the decoupling limit implies that the cut-off scale (if identified with the scale at which the ghost enters) is higher than the strong coupling scale. Therefore there is a valid interesting region of applicability for these couplings at scales below the cut-off.",1409.3834v2 2014-09-23,Exploring the Anomalous Higgs-top Couplings,"Top quark with its large Yukawa coupling is crucially important to explore TeV scale physics. Therefore, the study of Higgs-top sector is highly motivated to look for any deviations from the standard model predictions. The most general lowest order Lagrangian for the Higgs-top Yukawa coupling has scalar ($\kappa$) and pseudoscalar ($\tilde{\kappa}$) components. Currently, these couplings are constrained indirectly using the present experimental limits on the Higgs-$\gamma$-$\gamma$ and Higgs-gluon-gluon couplings. Furthermore, stronger bounds on $\kappa$ and $\tilde{\kappa}$ are obtained using the limits on the electric dipole moments (EDM). In this work, we propose an asymmetry-like observable $O_{\phi}$ in $t\bar{t}H$ production at the LHC to probe the Higgs-top coupling and to distinguish between the scalar and pseudoscalar components. We also show that the presence of the pseudoscalar component in the Higgs-top Yukawa coupling leads to a sizeable value for the top quark EDM. It is shown that a limit of $10^{-19}$ e.cm, which is achievable by the future $e^{-}e^{+}$ collider, allows us to exclude a significant region in the $(\kappa,\tilde{\kappa})$ plane.",1409.6553v2 2014-09-26,Multi-cluster dynamics in coupled phase oscillator networks,"In this paper we examine robust clustering behaviour with multiple nontrivial clusters for identically and globally coupled phase oscillators. These systems are such that the dynamics is completely determined by the number of oscillators N and a single scalar function $g(\varphi)$ (the coupling function). Previous work has shown that (a) any clustering can stably appear via choice of a suitable coupling function and (b) open sets of coupling functions can generate heteroclinic network attractors between cluster states of saddle type, though there seem to be no examples where saddles with more than two nontrivial clusters are involved. In this work we clarify the relationship between the coupling function and the dynamics. We focus on cases where the clusters are inequivalent in the sense of not being related by a temporal symmetry, and demonstrate that there are coupling functions that give robust heteroclinic networks between periodic states involving three or more nontrivial clusters. We consider an example for N=6 oscillators where the clustering is into three inequivalent clusters. We also discuss some aspects of the bifurcation structure for periodic multi-cluster states and show that the transverse stability of inequivalent clusters can, to a large extent, be varied independently of the tangential stability.",1409.7527v1 2014-10-24,Phenomenological theory of magneto-electric coupling in granular multiferroics,"We study coupling between the ferroelectric polarization and magnetization of granular ferromagnetic film using a phenomenological model of combined multiferroic system consisting of granular ferromagnetic film placed above the ferroelectric (FE) layer. The coupling is due to screening of Coulomb interaction in the granular film by the FE layer. Below the FE Curie temperature the magnetization has hysteresis as a function of electric field. Below the magnetic ordering temperature the polarization has hysteresis as a function of magnetic field. We study the magneto-electric coupling for weak and strong spatial dispersion of the FE layer. The effect of mutual influence decreases with increasing the spatial dispersion of the FE layer. For weak dispersion the strongest coupling occurs in the vicinity of the ferroelectric-paraelectric phase transition. For strong dispersion the situation is the opposite. We study the magneto-electric coupling as a function of distance between the FE layer and the granular film. For large distances the coupling decays exponentially due to the exponential decrease of electric field produced by the oscillating charges in the granular ferromagnetic film.",1410.6536v1 2014-11-06,Spin - orbital-angular-momentum coupling in Bose-Einstein condensates,"Spin-orbit coupling (SOC) plays a crucial role in many branches of physics. In this context, the recent experimental realization of the coupling between spin and linear momentum of ultracold atoms opens a completely new avenue for exploring new spin-related superfluid physics. Here we propose that another important and fundamental SOC, the coupling between spin and orbital angular momentum (SOAM), can be implemented for ultracold atoms using higher-order Laguerre-Gaussian laser beams to induce Raman coupling between two hyperfine spin states of atoms. We study the ground-state phase diagrams of SOAM-coupled Bose-Einstein condensates on a ring trap and explore their applications in gravitational force detection. Our results may provide the basis for further investigation of intriguing superfluid physics induced by SOAM coupling, such as collective excitations.",1411.1737v3 2014-12-08,Effect of Electron-Phonon Coupling on Thermal Transport across Metal-Nonmetal Interface - A Second Look,"The effect of electron-phonon (e-ph) coupling on thermal transport across metal-nonmetal interfaces is yet to be completely understood. In this paper, we use a series of molecular dynamics (MD) simulations with e-ph coupling effect included by Langevin dynamics to calculate the thermal conductance at a model metal-nonmetal interface. It is found that while e-ph coupling can present additional thermal resistance on top of the phonon-phonon thermal resistance, it can also make the phonon-phonon thermal conductance larger than the pure phonon transport case. This is because the e-ph interaction can disturb the phonon subsystem and enhance the energy communication between different phonon modes inside the metal. This facilitates redistributing phonon energy into modes that can more easily transfer energy across the interfaces. Compared to the pure phonon thermal conduction, the total thermal conductance with e-ph coupling effect can become either smaller or larger depending on the coupling factor. This result helps clarify the role of e-ph coupling in thermal transport across metal-nonmetal interface.",1412.2791v3 2014-12-30,Evolution of generalized couple-stress continuum theories: a critical analysis,"In this paper, we examine different generalized couple-stress continuum mechanics theories, including couple stress, strain gradient and micropolar theories. First, we investigate the fundamental requirements in any consistent size-dependent couple stress continuum mechanics, for which satisfying basic rules of mathematics and mechanics are crucial to establish a consistent theory. As a result, we show that continuum couple stress theory must be based on the displacement field and its corresponding macrorotation field as degrees of freedom, while an extraneous artificial microrotation cannot be a true continuum mechanical concept. Furthermore, the idea of generalized force and independent generalized degrees of freedom show that the normal component of the surface moment traction vector must vanish. Then, with these requirements in mind, various existing couple stress theories are examined critically, and we find that certain deviatoric curvature tensors create indeterminacy in the spherical part of the couple stress tensor. We also examine micropolar and micromorphic theories from this same perspective.",1501.03112v1 2015-01-29,Temperature dependence of thermal conductivities of coupled rotator lattice and the momentum diffusion in standard map,"In contrary to other 1D momentum-conserving lattices such as the Fermi-Pasta-Ulam $\beta$ (FPU-$\beta$) lattice, the 1D coupled rotator lattice is a notable exception which conserves total momentum while exhibits normal heat conduction behavior. The temperature behavior of the thermal conductivities of 1D coupled rotator lattice had been studied in previous works trying to reveal the underlying physical mechanism for normal heat conduction. However, two different temperature behaviors of thermal conductivities have been claimed for the same coupled rotator lattice. These different temperature behaviors also intrigue the debate whether there is a phase transition of thermal conductivities as the function of temperature. In this work, we will revisit the temperature dependent thermal conductivities for the 1D coupled rotator lattice. We find that the temperature dependence follows a power law behavior which is different with the previously found temperature behaviors. Our results also support the claim that there is no phase transition for 1D coupled rotator lattice. We also give some discussion about the similarity of diffusion behaviors between the 1D coupled rotator lattice and the single kicked rotator also called the Chirikov standard map.",1501.07419v1 2015-02-27,Quantum phases of Bose-Einstein condensates with synthetic spin - orbital-angular-momentum coupling,"The experimental realization of emergent spin-orbit coupling through laser-induced Raman transitions in ultracold atoms paves the way for exploring novel superfluid physics and simulating exotic many-body phenomena. A recent proposal with the use of Laguerre-Gaussian lasers enables another fundamental type of coupling between spin and orbital angular momentum (SOAM) in ultracold atoms. We hereby study quantum phases of a realistic Bose-Einstein condensate (BEC) with this synthetic SOAM coupling in a disk-shaped geometry, respecting radial inhomogeneity of the Raman coupling. We find that the experimental system naturally resides in a strongly interacting regime in which the phase diagram significantly deviates from the single-particle picture. The interplay between SOAM coupling and interaction leads to rich structures in spin-resolved position and momentum distributions, including a stripe phase and various types of immiscible states. Our results would provide a guide for an experimental investigation of SOAM-coupled BECs.",1502.08052v2 2015-03-15,Inverse Vernier Effects in Coupled Lasers,"In this report we study the Vernier effect in coupled laser systems consisting of two cavities. We show that depending on the nature of their coupling, not only can the ""supermodes"" formed at the overlapping resonances of the coupled cavities have the lowest thresholds and lase first as previously suggested, leading to a manifestation of the typical Vernier effect now in an active system; these supermodes can also have increased thresholds and are hence suppressed, which can be viewed as an inverse Vernier effect. We attribute this effect to detuning-dependent Q-spoiling, and it can lead to an increased free spectrum range and possibly single-mode lasing, which may explain the experimental findings of several previous work. We illustrate this effect using two coupled micro-ring cavities and a micro-ring cavity coupled to a slab cavity, and we discuss its relation to the existence of exceptional points in coupled lasers.",1503.04382v1 2015-04-14,Strong Coupling of Intersubband Resonance in a High Electron Mobility Transistor Structure to a THz Metamaterial by Ultrawide Electrical Tuning,"The interaction between intersubband resonances (ISRs) and metamaterial microcavities can form a strongly coupled system where new resonances form that depend on the coupling strength. Here we present experimental evidence of strong coupling between the cavity resonance of a THz metamaterial and the ISR in a high electron mobility transistor structure with a triangular confinement. The device is electrically switched from an uncoupled to a strongly coupled regime by tuning the ISR with epitaxially grown transparent gates. An asymmetric triangular potential in the heterostructure enables ultrawide electrical tuning of ISR which is an order of magnitude higher as compared to the equivalent square well. For a single triangular well, we achieve a coupling strength of 0.52 THz, with a normalized coupling ratio of 0.26.",1504.03569v1 2015-05-07,Landau pole in the Standard Model with weakly interacting scalar fields,"We consider the Standard Model with a new scalar field $X$ which is a $n_X^{}$ representation of the $SU(2)_L$ with a hypercharge $Y_X$. The renormalization group running effects on the new scalar quartic coupling constants are evaluated. Even if we set the scalar quartic coupling constants to be zero at the scale of the new scalar field, the coupling constants are induced by the one-loop effect of the weak gauge bosons. Once non-vanishing couplings are generated, the couplings rapidly increase by renormalization group effect of the quartic coupling constant itself. As a result, the Landau pole appears below Planck scale if $n_X^{}\geq 4$. We find that the scale of the obtained Landau pole is much lower than that evaluated by solving the one-loop beta function of the gauge coupling constants.",1505.01721v2 2015-05-21,Cavity-mediated coupling of mechanical oscillators limited by quantum backaction,"A complex quantum system can be constructed by coupling simple quantum elements to one another. For example, trapped-ion or superconducting quantum bits may be coupled by Coulomb interactions, mediated by the exchange of virtual photons. Alternatively quantum objects can be coupled by the exchange of real photons, particularly when driven within resonators that amplify interactions with a single electro-magnetic mode. However, in such an open system, the capacity of a coupling channel to convey quantum information or generate entanglement may be compromised. Here, we realize phase-coherent interactions between two spatially separated, near-ground-state mechanical oscillators within a driven optical cavity. We observe also the noise imparted by the optical coupling, which results in correlated mechanical fluctuations of the two oscillators. Achieving the quantum backaction dominated regime opens the door to numerous applications of cavity optomechanics with a complex mechanical system. Our results thereby illustrate the potential, and also the challenge, of coupling quantum objects with light.",1505.05850v1 2015-05-27,Position-squared coupling in a tunable photonic crystal optomechanical cavity,"We present the design, fabrication, and characterization of a planar silicon photonic crystal cavity in which large position-squared optomechanical coupling is realized. The device consists of a double-slotted photonic crystal structure in which motion of a central beam mode couples to two high-Q optical modes localized around each slot. Electrostatic tuning of the structure is used to controllably hybridize the optical modes into supermodes which couple in a quadratic fashion to the motion of the beam. From independent measurements of the anti-crossing of the optical modes and of the optical spring effect, the position-squared vacuum coupling rate is measured to be as large as 245 Hz to the fundamental in-plane mechanical resonance of the structure at 8.7MHz, which in displacement units corresponds to a coupling coefficient of 1 THz/nm$^2$. This level of position-squared coupling is approximately five orders of magnitude larger than in conventional Fabry-Perot cavity systems.",1505.07291v1 2015-06-18,Vectorlike $W^\pm$-boson coupling at TeV and third family fermion masses,"In the third fermion family and gauge symmetry of the Standard Model, we study the quark-quark, lepton-lepton and quark-lepton four-fermion operators in an effective theory at high energies. These operators have nontrivial contributions to the Schwinger-Dyson equations for fermion self-energy functions and the $W^\pm$-boson coupling vertex. As a result, the top-quark mass is generated via the spontaneous symmetry breaking of $\langle\bar t t \rangle$-condensate and the $W^\pm$-boson coupling becomes approximately vectorlike at TeV scale. The bottom-quark, tau-lepton and tau-neutrino masses are generated via the explicit symmetry breaking of $W^\pm$-contributions and quark-lepton interactions. Their masses and Yukawa couplings are functions of the top-quark mass and Yukawa coupling. We qualitatively show the hierarchy of fermion masses and Yukawa couplings of the third fermion family. We also discuss the possible collider signatures due to the vectorlike (parity-restoration) feature of $W^\pm$-boson coupling at high energies.",1506.05994v3 2015-09-02,Instanton induced Yukawa couplings from distant E3 and E(-1) instantons,"We calculate non-perturbative contributions to Yukawa couplings on D3-branes at orbifold singularities due to E3 and fractional E(-1) instantons which do not intersect the visible sector branes. While distant E3 instantons on bulk cycles typically contribute to Yukawa couplings, we find that distant fractional E(-1) can also give rise to new Yukawa couplings. However, fractional E(-1) instantons only induce Yukawa couplings if they are located at a singularity which shares a collapsed homologous two-cycle with the singularity supporting the visible sector. The non-perturbative contributions to Yukawa couplings exhibit a different flavour structure than the tree-level Yukawa couplings and, as a result, they can be sources of flavour violation. This is particularly relevant for schemes of moduli stabilisation which rely on superpotential contributions from E3 instantons, such as KKLT or the Large Volume Scenario. As a byproduct of our analysis, we shed some new light on the properties of annulus diagrams with matter field insertions in stringy instanton calculus.",1509.00852v2 2015-09-21,Nature of Valance Band Splitting on Multilayer MoS2,"Understanding the origin of splitting of valance band is important since it governs the unique spin and valley physics in few-layer MoS2. With first principle methods, we explore the effects of spin-orbit coupling and layer's coupling on few-layer MoS2. It is found that intra-layer spin-orbit coupling has a major contribution to the splitting of valance band at K. In double-layer MoS2, the layer's coupling results in the widening of energy gap of splitted states induced by intra-layer spin-orbit coupling. The valance band splitting of bulk MoS_2 in K can follow this model. We also find the effect of inter-layer spin-orbit coupling in triple-layer MoS2. In addition, the inter-layer spin-orbit coupling is found to become to be stronger under the pressure and results in the decrease of main energy gap in the splitting valance bands at K.",1509.06118v1 2015-09-23,Plasmon-enhanced electron-phonon coupling in Dirac surface states of the thin-film topological insulator Bi2Se3,"Raman measurements of a Fano-type surface phonon mode associated with Dirac surface states (SS) in Bi2Se3 topological insulator thin films allowed an unambiguous determination of the electron-phonon coupling strength in Dirac SS as a function of film thickness ranging from 2 to 40 nm. A non-monotonic enhancement of the electron-phonon coupling strength with maximum for the 8 - 10 nm thick films was observed. The non-monotonicity is suggested to originate from plasmon-phonon coupling which enhances electron-phonon coupling when free carrier density in Dirac SS increases with decreasing film thickness and becomes suppressed for thinnest films when anharmonic coupling between in-plane and out-of-plane phonon modes occurs. The observed about four-fold enhancement of electron-phonon coupling in Dirac SS of the 8 - 10 nm thick Bi2Se3 films with respect to the bulk samples may provide new insights into the origin of superconductivity in this-type materials and their applications.",1509.07182v1 2015-11-03,Spin-Orbit Coupling Induced Back-action Cooling in Cavity-Optomechanics with a Bose-Einstein Condensate,"We report a spin-orbit coupling induced back-action cooling in an optomechanical system, composed of a spin-orbit coupled Bose-Einstein condensate trapped in an optical cavity with one movable end mirror, by suppressing heating effects of quantum noises. The collective density excitations of the spin-orbit coupling mediated hyperfine states - serving as atomic oscillators equally coupled to the cavity field - trigger strongly driven atomic back-action. We find that the back-action not only revamps low-temperature dynamics of its own but also provides an opportunity to cool the mechanical mirror to its quantum mechanical ground state. Further, we demonstrate that the strength of spin-orbit coupling also superintends dynamic structure factor and squeezes nonlinear quantum noises, like thermo-mechanical and photon shot noise, which enhances optomechanical features of hybrid cavity beyond the previous investigations. Our findings are testable in a realistic setup and enhance the functionality of cavity-optomechanics with spin-orbit coupled hyperfine states in the field of quantum optics and quantum computation.",1511.01109v2 2015-11-04,Enhanced strain coupling of nitrogen vacancy spins to nanoscale diamond cantilevers,"Nitrogen vacancy (NV) centers can couple to confined phonons in diamond mechanical resonators via the effect of lattice strain on their energy levels. Access to the strong spin-phonon coupling regime with this system requires resonators with nanoscale dimensions in order to overcome the weak strain response of the NV ground state spin sublevels. In this work, we study NVs in diamond cantilevers with lateral dimensions of a few hundred nm. Coupling of the NV ground state spin to the mechanical mode is detected in electron spin resonance (ESR), and its temporal dynamics are measured via spin echo. Our small mechanical mode volume leads to a 10-100X enhancement in spin-phonon coupling strength over previous NV-strain coupling demonstrations. This is an important step towards strong spin-phonon coupling, which can enable phonon-mediated quantum information processing and quantum metrology.",1511.01548v1 2015-11-15,Mode coupling in solar spicule oscillations,"In a real medium which has oscillations, the perturbations can cause the energy transfer between different modes. The perturbation interpreted as an interaction between the modes is inferred as mode coupling. Mode coupling process in an inhomogeneous medium such as solar spicules may lead to the coupling of kink waves to local Alfven waves. This coupling occurs practically in any conditions when there is smooth variation in density in the radial direction. This process is seen as the decay of transverse kink waves in the medium. To study the damping of kink waves due to mode coupling, a 2.5-dimensional numerical simulation of the initial wave is considered in spicules. The initial perturbation is assumed to be in a plane perpendicular to the spicule axis. The considered kink wave is a standing wave which shows an exponential damping in the inhomogeneous layer after occurrence of the mode coupling.",1511.05135v1 2016-01-25,Master Stability Islands for Amplitude Death in Networks of Delay-Coupled Oscillators,"This paper presents a master stability function (MSF) approach for analyzing the stability of amplitude death (AD) in networks of delay-coupled oscillators. Unlike the familiar MSFs for instantaneously coupled networks, which typically have a single input encoding for the effects of the eigenvalues of the network Laplacian matrix, for delay-coupled networks we show that such MSFs generally require two additional inputs: the time delay and the coupling strength. To utilize the MSF for predicting the stability of AD of arbitrary networks for a chosen nonlinear system (node dynamics) and coupling function, we introduce the concept of master stability islands (MSIs), which are two-dimensional stability islands of the delay-coupling space together with a third dimension (""altitude"") encoding for eigenvalues that result in stable AD. We compute the MSFs and show the corresponding MSIs for several common chaotic systems including the Rossler, the Lorenz, and Chen's system, and found that it is generally possible to achieve AD and that a nonzero time delay is necessary for the stabilization of the AD states.",1601.06758v2 2016-02-13,Perturbative unification of gauge couplings in supersymmetric $E_6$ models,"We study gauge coupling unification in supersymmetric $E_6$ models where an additional $\mathrm{U}(1)'$ gauge symmetry is broken near the TeV scale and a number of exotic matter fields from the $\bm{27}$ representations have $O(\mathrm{TeV})$ mass. Solving the 2-loop renormalization group equations of gauge couplings and a kinetic mixing coupling between the $\mathrm{U}(1)'$ and $\mathrm{U}(1)_Y$ gauge fields, we find that the gauge couplings fall into the non-perturbative regime below the GUT scale. We examine threshold corrections on the running of gauge couplings from both light and heavy ($\sim$ GUT scale) particles and show constraints on the size of corrections to achieve the perturbative unification of gauge couplings.",1602.04271v2 2016-04-22,Coherent Coupling of WS_2 Monolayers with Metallic Photonic Nanostructures at Room Temperature,"Room temperature strong coupling of WS_2 monolayer exciton transitions to metallic Fabry-Perot and plasmonic optical cavities is demonstrated. A Rabi splitting of 101 meV is observed for the Fabry-Perot cavity, more than double those reported to date in other 2D materials. The enhanced magnitude and visibility of WS_2 monolayer strong coupling is attributed to the larger absorption coefficient, the narrower linewidth of the A exciton transition, and greater spin-orbit coupling. For WS_2 coupled to plasmonic arrays, the Rabi splitting still reaches 60 meV despite the less favorable coupling conditions, and displays interesting photoluminescence features. The unambiguous signature of WS_2 monolayer strong coupling in easily fabricated metallic resonators at room temperature suggests many possibilities for combining light-matter hybridization with spin and valleytronics.",1604.06656v1 2016-06-10,Indirect Coupling between Two Cavity Photon Systems via Ferromagnetic Resonance,"We experimentally realize indirect coupling between two cavity modes via strong coupling with the ferromagnetic resonance in Yttrium Iron Garnet (YIG). We find that some indirectly coupled modes of our system can have a higher microwave transmission than the individual uncoupled modes. Using a coupled harmonic oscillator model, the influence of the oscillation phase difference between the two cavity modes on the nature of the indirect coupling is revealed. These indirectly coupled microwave modes can be controlled using an external magnetic field or by tuning the cavity height. This work has potential for use in controllable optical devices and information processing technologies.",1606.03469v1 2016-06-22,Electro-hydrodynamic synchronization of piezoelectric flags,"Hydrodynamic coupling of flexible flags in axial flows may profoundly influence their flapping dynamics, in particular driving their synchronization. This work investigates the effect of such coupling on the harvesting efficiency of coupled piezoelectric flags, that convert their periodic deformation into an electrical current. Considering two flags connected to a single output circuit, we investigate using numerical simulations the relative importance of hydrodynamic coupling to electrodynamic coupling of the flags through the output circuit due to the inverse piezoelectric effect. It is shown that electrodynamic coupling is dominant beyond a critical distance, and induces a synchronization of the flags' motion resulting in enhanced energy harvesting performance. We further show that this electrodynamic coupling can be strengthened using resonant harvesting circuits.",1606.06936v1 2016-06-24,The impact of non-minimally coupled gravity on vacuum stability,"We consider vacuum decay in the presence of a non-minimal coupling to gravity. We extend the usual thin-wall solution to include the non-minimal coupling. We also perform a full numerical study and discuss the validity of the new thin-wall approximation. Implications of a large cosmological constant, whose influence on the geometry boosts the tunnelling rate, are discussed. Our results show that the influence of the non-minimal coupling differs significantly between the cases of Minkowski and deSitter backgrounds. In the latter the decay probability quickly decreases when the coupling grows and in fact the vacuum can be made absolutely stable simply due to introduction of the non-minimal coupling. In the case of Minkowski background the effect is much weaker and the decay rate even increases for small values of the non-minimal coupling.",1606.07808v1 2016-07-07,Synchronization Detection in Networks of Coupled Oscillators for Pattern Recognition,"Coupled oscillator-based networks are an attractive approach for implementing hardware neural networks based on emerging nanotechnologies. However, the readout of the state of a coupled oscillator network is a difficult challenge in hardware implementations, as it necessitates complex signal processing to evaluate the degree of synchronization between oscillators, possibly more complicated than the coupled oscillator network itself. In this work, we focus on a coupled oscillator network particularly adapted to emerging technologies, and evaluate two schemes for reading synchronization patterns that can be readily implemented with basic CMOS circuits. Through simulation of a simple generic coupled oscillator network, we compare the operation of these readout techniques with a previously proposed full statistics evaluation scheme. Our approaches provide results nearly identical to the mathematical method, but also show better resilience to moderate noise, which is a major concern for hardware implementations. These results open the door to widespread realization of hardware coupled oscillator-based neural systems.",1607.01983v1 2016-07-24,Oscillation quenching in third order Phase Locked Loop coupled by mean field diffusive coupling,"We explore analytically the oscillation quenching phenomena (amplitude death and oscillation death) in a coupled third order phase locked loop (PLL) both in periodic and chaotic mode. The phase locked loops are coupled through mean field diffusive coupling. The lower and upper limits of the quenched state are identified in the parameter space of the coupled PLL using Routh-Hurwitz technique. We further observe that the ability of convergence to the quenched state of coupled PLLs depends on the design parameters. For identical system both the system converges to homogeneous steady state whereas for non-identical parameter values they converge to inhomogeneous steady state. It is also observed that for identical systems the quenched state is wider than non-identical case. When the systems parameters are so chosen that each isolated loops are chaotic in nature, in that case we observe the quenched state is relatively narrow. All these phenomena are also demonstrated through numerical simulations.",1607.06990v1 2016-07-26,Mode Modification of Plasmonic Gap Resonances induced by Strong Coupling with Molecular Excitons,"Plasmonic cavities can be used to control the atom-photon coupling process at the nanoscale, since they provide ultrahigh density of optical states in an exceptionally small mode volume. Here we demonstrate strong coupling between molecular excitons and plasmonic resonances (so-called plexcitonic coupling) in a film-coupled nanocube cavity, which can induce profound and significant spectral and spatial modifications to the plasmonic gap modes. Within the spectral span of a single gap mode in the nanotube-film cavity with a 3-nm wide gap, the introduction of narrow-band J-aggregate dye molecules not only enables an anti-crossing behavior in the spectral response, but also splits the single spatial mode into two distinct modes that are easily identified by their far-field scattering profiles. Simulation results confirm the experimental findings and the sensitivity of the plexcitonic coupling is explored using digital control of the gap spacing. Our work opens up a new perspective to study the strong coupling process, greatly extending the functionality of nanophotonic systems, with the potential to be applied in cavity quantum electrodynamic systems.",1607.07620v1 2017-02-15,Topological Properties of a Coupled Spin-Photon System Induced by Damping,"We experimentally examine the topological nature of a strongly coupled spin-photon system induced by damping. The presence of both spin and photonic losses results in a non-Hermitian system with a variety of exotic phenomena dictated by the topological structure of the eigenvalue spectra and the presence of an exceptional point (EP), where the coupled spin-photon eigenvectors coalesce. By controlling both the spin resonance frequency and the spin-photon coupling strength we observe a resonance crossing for cooperativities above one, suggesting that the boundary between weak and strong coupling should be based on the EP location rather than the cooperativity. Furthermore we observe dynamic mode switching when encircling the EP and identify the potential to engineer the topological structure of coupled spin-photon systems with additional modes. Our work therefore further highlights the role of damping within the strong coupling regime, and demonstrates the potential and great flexibility of spin-photon systems for studies of non-Hermitian physics.",1702.04797v2 2017-02-17,Control of amplitude chimeras by time delay in dynamical networks,"We investigate the influence of time-delayed coupling in a ring network of non-locally coupled Stuart-Landau oscillators upon chimera states, i.e., space-time patterns with coexisting partially coherent and partially incoherent domains. We focus on amplitude chimeras which exhibit incoherent behavior with respect to the amplitude rather than the phase and are transient patterns, and show that their lifetime can be significantly enhanced by coupling delay. To characterize their transition to phase-lag synchronization (coherent traveling waves) and other coherent structures, we generalize the Kuramoto order parameter. Contrasting the results for instantaneous coupling with those for constant coupling delay, for time-varying delay, and for distributed-delay coupling, we demonstrate that the lifetime of amplitude chimera states and related partially incoherent states can be controlled, i.e., deliberately reduced or increased, depending upon the type of coupling delay.",1702.05326v2 2017-02-26,Magnon-photon coupling in antiferromagnets,"Magnon-photon coupling in antiferromagnets has many attractive features that do not exist in ferro- or ferrimagnets. We show quantum-mechanically that, in the absence of an external field, one of the two degenerated spin wave bands couples with photons while the other does not. The photon mode anticrosses with the coupled spin waves when their frequencies are close to each other. Similar to its ferromagnetic counterpart, the magnon-photon coupling strength is proportional to the square root of number of spins $\sqrt{N}$ in antiferromagnets. An external field removes the spin wave degeneracy and both spin wave bands couple to the photons, resulting in two anticrossings between the magnons and photons. Two transmission peaks were observed near the anticrossing frequency. The maximum damping that allows clear discrimination of the two transmission peaks is proportional to $\sqrt{N}$ and it's well below the damping of antiferromagnetic insulators. Therefore the strong magnon-photon coupling can be realized in antiferromagnets and the coherent information transfer between the photons and magnons is possible.",1702.07977v1 2017-03-06,Cosmological Dynamics of D-BIonic and DBI Scalar Field and Coincidence Problem of Dark Energy,"We study the cosmological dynamics of D-BIonic and DBI scalar field, which is coupled to matter fluid. For the exponential potential and the exponential couplings, we find a new analytic scaling solution yielding the accelerated expansion of the Universe. Since it is shown to be an attractor for some range of the coupling parameters, the density parameter of matter fluid can be the observed value, as in the coupled quintessence with a canonical scalar field. Contrary to the usual coupled quintessence, where the value of matter couple giving observed density parameter is too large to satisfy observational constraint from CMB, we show that the D-BIonic theory can give similar solution with much smaller value of matter coupling. As a result, together with the fact that the D-BIonic theory has a screening mechanism, the D-BIonic theory can solve the so-called coincidence problem as well as the dark energy problem.",1703.01745v1 2017-03-13,Multiple-point principle realized with strong dynamics,"We present a novel extension of the Standard Model which fulfills the multiple-point principle without contradicting the Higgs particle mass measurement. In the model, the scalar potential has two minima where the scalar field has vacuum expectation values of 246 GeV and the Planck mass $\simeq 2.44\times 10^{18}$ GeV, the latter of which is realized by considering a classically scale invariant setup and requiring that the scalar quartic coupling and its beta function vanish at the Planck scale. The Standard Model Higgs field is a mixture of an elementary scalar and composite scalars in a new strongly-coupled gauge theory, and the strong dynamics gives rise to the negative mass for the SM Higgs field, and at the same time, causes separation of the SM Higgs quartic coupling and the quartic coupling for the elementary scalar, which leads to the vanshing of the latter quartic coupling and its beta function at the Planck scale. The model predicts new scalar particles with about 300 GeV mass possessing electroweak charges and Yukawa-type couplings with Standard Model fermions, and a new light gauge boson that couples to Standard Model fermions.",1703.04235v2 2017-03-16,AdS/CFT predictions for azimuthal and momentum correlations of $b\bar{b}$ pairs in heavy ion collisions,"We use an energy loss model sensitive to thermal fluctuations to compute the azimuthal and momentum correlations of $b\bar{b}$ pairs traversing a strongly coupled plasma from Pb+Pb collisions at LHC ($\sqrt{s}=2.76\text{TeV}$). The azimuthal correlations are compared with those from perturbative QCD based simulations. When restricted to leading order production processes, we find that the strongly coupled correlations of high transverse momentum pairs ($>4\text{GeV}$) are broadened less efficiently than the corresponding weak coupling based correlations, while low transverse momentum pairs (1-4GeV) are broadened with similar efficiency, but with an order of magnitude more particles ending up in this momentum class. The strong coupling momentum correlations we compute account for initial correlations and reveal that the particle pairs suppressed from initially high momenta to the low momentum domain do not suffice to explain the stark difference to the weak coupling results in momentum correlations for 1-4GeV. From this, we conclude that $b\bar{b}$ pairs are more likely to stay correlated in momentum when propagating through a strongly coupled plasma than a weakly coupled one.",1703.05845v1 2017-03-27,Asymptotic safety of higher derivative quantum gravity non-minimally coupled with a matter system,"We study asymptotic safety of models of the higher derivative quantum gravity with and without matter. The beta functions are derived by utilizing the functional renormalization group, and non-trivial fixed points are found. It turns out that all couplings in gravity sector, namely the cosmological constant, the Newton constant, and the $R^2$ and $R_{\mu\nu}^2$ coupling constants, are relevant in case of higher derivative pure gravity. For the Higgs-Yukawa model non-minimal coupled with higher derivative gravity, we find a stable fixed point at which the scalar-quartic and the Yukawa coupling constants become relevant. The relevant Yukawa coupling is crucial to realize the finite value of the Yukawa coupling constants in the standard model.",1703.09033v3 2017-08-05,Precise measurement of coupling strength and high temperature quantum effect in a nonlinearly coupled qubit-oscillator system,"We study the coherence dynamics of a qubit coupled to a harmonic oscillator with both linear and quadratic interactions. As long as the linear coupling strength is much smaller than the oscillator frequency, the long time behavior of the coherence is dominated by the quadratic coupling strength $g_2$. The coherence decays and revives at a period $2\pi/g_2$, with the width of coherence peak decreases as the temperature increases, hence providing a way to measure $g_2$ precisely without cooling. Unlike the case of linear coupling, here the coherence dynamics never reduces to the classical limit in which the oscillator is classical. Finally, the validity of linear coupling approximation is discussed and the coherence under Hahn-echo is evaluated",1708.01737v4 2017-08-21,Interparticle Coupling Effects of Two Quantum Dots System on the Transport Properties of a Single Plasmon,"Transport properties of a single plasmon interacting with two quantum dots (QDs) system coupled to one-dimensional surface plasmonic waveguide are investigated theoretically via the real-space approach. We mainly focus on the coupling effects of the two QDs on the transmission properties of a single incident plasmon. We demonstrated that switching of a single plasmon can be achieved by controlling the interparticle distance, the interparticle coupling strength, and the QD-waveguide coupling strength, as well as spectral detuning. We also showed that the coupling between the continuum excitations and the discrete excitations results in the Fano-type transmission spectrum. The transport properties of a single plasmon interacting with such a two direct coupled QDs system could find the applications in the design of plasmonic nanodevices, such as single photon switching and nanomirrors, and in quantum information processing.",1708.06635v1 2018-02-27,Accurate measurement of a 96% input coupling into a cavity using polarization tomography,"Pillar microcavities are excellent light-matter interfaces providing an electromagnetic confinement in small mode volumes with high quality factors. They also allow the efficient injection and extraction of photons, into and from the cavity, with potentially near-unity input and output-coupling efficiencies. Optimizing the input and output coupling is essential, in particular, in the development of solid-state quantum networks where artificial atoms are manipulated with single incoming photons. Here we propose a technique to accurately measure input and output coupling efficiencies using polarization tomography of the light reflected by the cavity. We use the residual birefringence of pillar microcavities to distinguish the light coupled to the cavity from the uncoupled light: the former participates to rotating the polarization of the reflected beam, while the latter decreases the polarization purity. Applying this technique to a micropillar cavity, we measure a $53 \pm2 \% $ output coupling and a $96 \pm 1\%$ input coupling with unprecedented precision.",1802.09862v4 2018-04-02,Sequential escapes: onset of slow domino regime via a saddle connection,"We explore sequential escape behaviour of coupled bistable systems under the influence of stochastic perturbations. We consider transient escapes from a marginally stable ""quiescent"" equilibrium to a more stable ""active"" equilibrium. The presence of coupling introduces dependence between the escape processes: for diffusive coupling there is a strongly coupled limit (fast domino regime) where the escapes are strongly synchronised while for intermediate coupling (slow domino regime) without partially escaped stable states, there is still a delayed effect. These regimes can be associated with bifurcations of equilibria in the low-noise limit. In this paper we consider a localized form of non-diffusive (i.e pulse-like) coupling and find similar changes in the distribution of escape times with coupling strength. However we find transition to a slow domino regime that is not associated with any bifurcations of equilibria. We show that this transition can be understood as a codimension-one saddle connection bifurcation for the low-noise limit. At transition, the most likely escape path from one attractor hits the escape saddle from the basin of another partially escaped attractor. After this bifurcation we find increasing coefficient of variation of the subsequent escape times.",1804.00550v1 2018-04-12,Ghost-free completion of an effective matter coupling in bimetric theory,"We consider a particular set of ghost-free interactions for three spin-2 fields in which we freeze out the dynamics of the metric tensor that couples to the matter sector. Integrating out the non-dynamical degrees of freedom in vacuum results in a ghost-free bimetric theory. In the presence of the matter source, which we treat as a small perturbation, the equations for the non-dynamical field can be solved perturbatively for its vierbein. This results in ghost-free bimetric theory in vierbein formulation with a modified matter coupling. To lowest order in matter perturbations, we precisely obtain an effective matter coupling that has been suggested earlier in the literature. This coupling contains a linear combination of the two vierbeine whose corresponding metric fluctuation coincides with the massless spin-2 mode. In the past, bimetric theory with this symmetric coupling has been treated as an effective theory valid at low energies without a ghost-free completion. Our results demonstrate that the effective matter coupling can be rendered entirely ghost-free by including the higher-order corrections obtained from the trimetric setup.",1804.04671v2 2018-11-05,Revealing Strong Plasmon-Exciton Coupling Between Nano-gap Resonators and Two-Dimensional Semiconductors at Ambient Conditions,"Strong coupling of two-dimensional semiconductor excitons with plasmonic resonators enables control of light-matter interaction at the subwavelength scale. Here we develop strong coupling in plasmonic nano-gap resonators that allow modification of exciton number contributing to the coupling. Using this system, we not only demonstrate a large vacuum Rabi splitting up to 163 meV and splitting features in photoluminescence spectra, but also reveal that the exciton number can be reduced down to single-digit level (N<10), which is an order lower than that of traditional systems, close to single-exciton based strong coupling. In addition, we prove that the strong coupling process is not affected by the large exciton coherence size that was previously believed to be detrimental to the formation of plasmon-exciton interaction. Our work provides a deeper understanding of storng coupling in two-dimensional semiconductors, paving the way for room temperature quantum optics applications.",1811.01598v1 2018-11-19,Squared quadratic Wasserstein distance : optimal couplings and Lions differentiability,"In this paper, we remark that any optimal coupling for the quadratic Wasserstein distance $W^2_2(\mu,\nu)$ between two probability measures $\mu$ and $\nu$ with finite second order moments on $\mathbb{R}^d$ is the composition of a martingale coupling with an optimal transport map ${\mathcal T}$. We check the existence of an optimal coupling in which this map gives the unique optimal coupling between $\mu$ and ${\mathcal T}\#\mu$. Next, we give a direct proof that $\sigma\mapsto W_2^2(\sigma,\nu)$ is differentiable at $\mu$ in the Lions sense iff there is a unique optimal coupling between $\mu$ and $\nu$ and this coupling is given by a map. It was known combining results by Ambrosio, Gigli and Savar\'e and Ambrosio and Gangbo that, under the latter condition, geometric differentiability holds. Moreover, the two notions of differentiability are equivalent according to the recent paper of Gangbo and Tudorascu. Besides, we give a self-contained probabilistic proof that mere Fr\'echet differentiability of a law invariant function $F$ on $L^2(\Omega,\mathbb{P};\mathbb{R}^d)$ is enough for the Fr\'echet differential at $X$ to be a measurable function of $X$.",1811.07787v3 2018-11-24,Collective dipole oscillations of a spin-orbit coupled Fermi gas,"The collective dipole mode is induced and measured in a spin-orbit (SO) coupled degenerate Fermi gas of $^{173}$Yb atoms. Using a differential optical Stark shift, we split the degeneracy of three hyperfine states in the ground manifold, and independently couple consecutive spin states with the equal Raman transitions. A relatively long-lived spin-orbit-coupled Fermi gas, readily being realized with a narrow optical transition, allows to explore a single-minimum dispersion where three minima of spin-1 system merge into and to monitor collective dipole modes of fermions in the strong coupling regime. The measured oscillation frequency of the dipole mode is compared with the semi-classical calculation in the single-particle regime. Our work should pave the way towards the characterization of spin-orbit-coupled fermions with large spin $s>\frac{1}{2}$ in the strong coupling regime.",1811.09846v1 2010-05-24,EPW: A program for calculating the electron-phonon coupling using maximally localized Wannier functions,"EPW (Electron-Phonon coupling using Wannier functions) is a program written in FORTRAN90 for calculating the electron-phonon coupling in periodic systems using density-functional perturbation theory and maximally-localized Wannier functions. EPW can calculate electron-phonon interaction self-energies, electron-phonon spectral functions, and total as well as mode-resolved electron-phonon coupling strengths. The calculation of the electron-phonon coupling requires a very accurate sampling of electron-phonon scattering processes throughout the Brillouin zone, hence reliable calculations can be prohibitively time-consuming. EPW combines the Kohn-Sham electronic eigenstates and the vibrational eigenmodes provided by the Quantum-ESPRESSO package [1] with the maximally localized Wannier functions provided by the wannier90 package [2] in order to generate electron-phonon matrix elements on arbitrarily dense Brillouin zone grids using a generalized Fourier interpolation. This feature of EPW leads to fast and accurate calculations of the electron-phonon coupling, and enables the study of the electron-phonon coupling in large and complex systems.",1005.4418v1 2014-03-26,Bipolarons and multi-polarons consisting of impurity atoms in a Bose-Einstein condensate,"The variational Feynman formalism for the polaron, extended to an all-coupling treatment of bipolarons, is applied for two impurity atoms in a Bose-Einstein condensate. This shows that if the polaronic coupling strength is large enough the impurities will form a bound state (the bipolaron). As a function of the mutual repulsion between the impurities two types of bipolaron are distinguished: a tightly bound bipolaron at weak repulsion and a dumbbell bipolaron at strong repulsion. Apart from the binding energy, also the evolution of the bipolaron radius and its effective mass are examined as a function of the strength of the repulsive interaction between the impurities and of the polaronic cupling strength. We then apply the strong-coupling formalism to multiple impuritiy atoms in a condensate which leads to the prediction of multi-polaron formation in the strong coupling regime. The results of the two formalisms are compared for two impurities in a condensate which results in a general qualitative agreement and a quantitative agreement at strong coupling. Typically the system of impurity atoms in a Bose-Einstein condensate is expected to exhibit the polaronic weak coupling regime. However, the polaronic coupling strength is in principle tunable with a Feshbach resonance.",1403.6588v1 2014-03-31,Degenerate Quantum Gases with Spin-Orbit Coupling,"This review focuses on recent developments on studying synthetic spin-orbit (SO) coupling in ultracold atomic gases. Two types of SO coupling are discussed. One is Raman process induced coupling between spin and motion along one of the spatial directions, and the other is Rashba SO coupling. We emphasize their common features in both single-particle and two-body physics and their consequences in many-body physics. For instance, single particle ground state degeneracy leads to novel features of superfluidity and richer phase diagram; increased low-energy density-of-state enhances interaction effects; the absence of Galilean invariance and spin-momentum locking give rise to intriguing behaviors of superfluid critical velocity and novel quantum dynamics; and mixing of two-body singlet and triplet states yields novel fermion pairing structure and topological superfluids. With these examples, we show that investigating SO coupling in cold atom systems can enrich our understanding of basic phenomena such as superfluidity, provide a good platform for simulating condensed matter states such as topological superfluids, and more importantly, result in novel quantum systems such as SO coupled unitary Fermi gas or high spin quantum gases. Finally we also point out major challenges and possible future directions.",1403.8021v2 2017-01-02,Chimera patterns in two-dimensional networks of coupled neurons,"We discuss synchronization patterns in networks of FitzHugh-Nagumo and Leaky Integrate-and-Fire oscillators coupled in a two-dimensional toroidal geometry. Common feature between the two models is the presence of fast and slow dynamics, a typical characteristic of neurons. Earlier studies have demonstrated that both models when coupled nonlocally in one-dimensional ring networks produce chimera states for a large range of parameter values. In this study, we give evidence of a plethora of two-dimensional chimera patterns of various shapes including spots, rings, stripes, and grids, observed in both models, as well as additional patterns found mainly in the FitzHugh-Nagumo system. Both systems exhibit multistability: For the same parameter values, different initial conditions give rise to different dynamical states. Transitions occur between various patterns when the parameters (coupling range, coupling strength, refractory period, and coupling phase) are varied. Many patterns observe in the two models follow similar rules. For example the diameter of the rings grows linearly with the coupling radius.",1701.00342v1 2017-01-17,BTZ black hole assuming running couplings,"In the present work a generalization of the BTZ black hole is studied, for the case of scale dependent couplings. One starts by using the effective action for scale dependence couplings to get a generalization of the Einstein field equations. Self consistent solutions for lapse function, cosmological coupling and Newtons coupling are found. The effect of scale dependent couplings with respect to the classical solution is shown. Moreover, asymptotic behavior as well as thermodynamic properties were investigated. Finally, an alternative way to get the scale dependent Newton coupling, from the so-called ""Null Energy Condition"" is presented.",1701.04531v1 2018-05-06,Quantum evolution speed in the finite-temperature bosonic environment,"We investigate the quantum evolution speed of a qubit in two kinds of finite-temperature environments. The first environment is a bosonic bath with Ohmic-like spectrum. It is found that the high temperature not only leads to the speed-up but also speed-down processes in the weak-coupling regime, which is different from the strong-coupling case where only exhibits speed-up process, and the effects of Ohmicity parameter of the bath on the quantum evolution speed are also different in the strong-coupling and weak-coupling regimes. Furthermore, we realize the controllable and stationary quantum evolution speed by applying the bang-bang pulse. For the second nonlinear bath, we study the quantum evolution speed of a qubit by resorting to the hierarchical equations of motion method beyond the Born-Markov approximation. It is shown that the performances of quantum evolution speed in weak-coupling and strong-coupling regimes are also different. In particular, the quantum evolution speed can be decelerated by the rise of temperature in the strong-coupling regime which is an anomalous phenomenon and contrary to the common recognition that quantum evolution speed always increases with the temperature.",1805.02145v1 2018-05-12,Occasional uncoupling overcomes measure desynchronization,"Owing to the absence of the phase space attractors in the Hamiltonian dynamical systems, the concept of the identical synchronization between the dissipative systems is inapplicable to the Hamiltonian systems for which, thus, one defines a related generalized phenomenon known as the measure synchronization. A coupled pair of Hamiltonian systems---the full coupled system also being Hamiltonian---can possibly be in two types of measure synchronized states: quasiperiodic and chaotic. In this paper, we take representative systems belonging to each such class of the coupled systems and highlight that, as the coupling strengths are varied, there may exist intervals in the ranges of the coupling parameters at which the systems are measure desynchronized. Subsequently, we illustrate that as a coupled system evolves in time, occasionally switching off the coupling when the system is in the measure desynchronized state can bring the system back in measure synchrony. Further, for the case of the occasional uncoupling being employed periodically and the corresponding time-period being small, we analytically find the values of the on-fraction of the time-period using which measure synchronization is effected on the corresponding desynchronized state.",1805.04761v2 2018-05-15,Spin-orbit-coupled Bose-Einstein condensates of rotating polar molecules,"An experimental proposal for realizing spin-orbit (SO) coupling of pseudospin-1 in the ground manifold $^1\Sigma(\upsilon=0)$ of (bosonic) bialkali polar molecules is presented. The three spin components are composed of the ground rotational state and two substates from the first excited rotational level. Using hyperfine resolved Raman processes through two select excited states resonantly coupled by a microwave, an effective coupling between the spin tensor and linear momentum is realized. The properties of Bose-Einstein condensates for such SO-coupled molecules exhibiting dipolar interactions are further explored. In addition to the SO-coupling-induced stripe structures, the singly and doubly quantized vortex phases are found to appear, implicating exciting opportunities for exploring novel quantum physics using SO-coupled rotating polar molecules with dipolar interactions.",1805.05524v1 2018-05-20,Network synchronization with periodic coupling,"The synchronization behavior of networked chaotic oscillators with periodic coupling is investigated. It is observed in simulations that the network synchronizability could be significantly influenced by tuning the coupling frequency, even making the network alternated between the synchronous and non-synchronous states. By the method of master stability function, we conduct a detailed analysis on the influence of coupling frequency on network synchronizability, and find that the network synchronizability is maximized at some characteristic frequencies comparable to the intrinsic frequency of the local dynamics. Moremore, it is found that as the amplitude of the coupling increases, the characteristic frequencies are gradually decreased. By the technique of finite-time Lyapunov exponent, we investigate further the mechanism for the maximized synchronizability, and find that at the characteristic frequencies the power spectrum of the finite-time Lyapunov exponent is abruptly changed from the localized to broad distributions. When this feature is absent or not prominent, the network synchronizability is less influenced by the periodic coupling. Our study shows the efficiency of finite-time Lyapunov exponent in exploring the synchronization behavior of temporally coupled oscillators, and sheds lights on the interplay between the system dynamics and structure in the general temporal networks.",1805.07699v1 2018-05-22,Stability of phase difference trajectories of networks of Kuramoto oscillators with time-varying couplings and intrinsic frequencies,"We study dynamics of phase-differences (PDs) of coupled oscillators where both the intrinsic frequencies and the couplings vary in time. In case the coupling coefficients are all nonnegative, we prove that the PDs are asymptotically stable if there exists T>0 such that the aggregation of the time-varying graphs across any time interval of length $T$ has a spanning tree. We also consider the situation that the coupling coefficients may be negative and provide sufficient conditions for the asymptotic stability of the PD dynamics. Due to time-variations, the PDs are asymptotic to time-varying patterns rather than constant values. Hence, the PD dynamics can be regarded as a generalisation of the well-known phase-locking phenomena. We explicitly investigate several particular cases of time-varying graph structures, including asymptotically periodic PDs due to periodic coupling coefficients and intrinsic frequencies, small perturbations, and fast-switching near constant coupling and frequencies, which lead to PD dynamics close to a phase-locked one. Numerical examples are provided to illustrate the theoretical results.",1805.08457v1 2018-05-23,Dynamics of Kuramoto oscillators with time-delayed positive and negative couplings,"Many real-world examples of distributed oscillators involve not only time delays but also attractive (positive) and repulsive (negative) influences in their network interactions. Here, considering such examples, we generalize the Kuramoto model of globally coupled oscillators with time-delayed positive and negative couplings to explore the effects of such couplings in collective phase synchronization. We analytically derive the exact solutions for stable incoherent and coherent states in terms of the system parameters allowing us to precisely understand the interplay of time delays and couplings in collective synchronization. Dependent on these parameters, fully coherent, incoherent states and mixed states are possible. Time-delays especially in the negative coupling seem to facilitate collective synchronization. In case of a stronger negative coupling than positive one, a stable synchronized state cannot be achieved without time delays. We discuss the implications of the model and the results for natural systems, particularly neuronal network systems in the brain.",1805.08967v1 2008-07-10,Search for anomalous $\boldmath{Wtb}$ couplings in single top quark production,"In 0.9 fb$^{-1}$ of $p \bar p$ collisions, D0 has observed an excess of events with an isolated lepton, missing transve rse momentum, and two to four jets. This excess is consistent with single top quark production. We examine these data to study the Lorentz structure of the $Wtb$ coupling. The standard model predicts a left-handed vector coupling at the $Wt b$ vertex. The most general lowest dimension, CP-conserving Lagrangian admits right-handed vector and left- or right-h anded tensor couplings as well. We find that the data prefer the left-handed vector coupling and set upper limits on the anomalous couplings. These are the first direct constraints on a general $Wtb$ interaction and the first direct limits on left- and right-handed tensor couplings.",0807.1692v1 2009-12-07,Interplay of vacuum-mediated inter- and intraatomic couplings in a pair of atoms,"The resonance fluorescence emitted by a system of two dipole-dipole interacting nearby four-level atoms in J=1/2 - J=1/2 configuration is studied. This setup is the simplest realistic model system which provides a complete description of the (interatomic) dipole-dipole interaction for arbitrary orientation of the interatomic distance vector, and at the same time allows for intraatomic spontaneously generated coherences. We discuss different methods to analyze the contribution of the various vacuum-induced coupling constants to the total resonance fluorescence spectrum. These allow us to find a dressed state interpretation of the contribution of the different interatomic dipole-dipole couplings to the total spectrum. We further study the role of the spontaneously generated coherences, and identify two different contributions to the single-particle vacuum-induced couplings. We show that they have a noticeable impact on the total resonance fluorescence spectrum down to small interatomic distances, even though the dipole-dipole couplings constants then are much larger in magnitude than the the single-particle coupling constants. Interestingly, we find that the interatomic couplings can induce an effect of the intraatomic spontaneously generated coherences on the observed spectra which is not present in single-atom systems.",0912.1300v1 2009-12-07,Fixing the Pole in the Pyramid,"We revisit the problem of the hidden sector Landau pole in the Pyramid Scheme. There is a fixed line in the plane of hidden sector gauge coupling and a Yukawa coupling between the trianon fields. We postulate that the couplings flow to this line, at a point where the hidden sector gauge coupling is close to the strong coupling edge of its perturbative regime. Below the masses of the heavier trianons, the model quickly flows to a confining N_F=N_C=3 supersymmetric gauge theory, as required by phenomenological considerations. We study possible discrete R-symmetries, which guarantee, among other things, that the basin of attraction of the fixed line has full co-dimension in the space of R-allowed couplings. The Yukawa couplings required to get the fixed line violate the pyrma-baryon symmetries we invoked in previous work to find a dark matter candidate. Omitting one of them, we have a dark matter candidate, and an acceptable RG flow down from the unification scale, if the confinement scale of the hidden sector group is lowered from 5 to 2 TeV.",0912.1313v1 2009-12-30,Dressed Counterions: Strong Electrostatic Coupling in the Presence of Salt,"We reformulate the theory of strong electrostatic coupling in order to describe an asymmetric electrolyte solution of monovalent salt ions and polyvalent counterions using field-theoretical techniques and Monte-Carlo simulations. The theory is based on an asymmetric treatment of the different components of the electrolyte solution. The weak coupling Debye-Huckel approach is used in order to describe the monovalent salt ions while a strong coupling approach is used to tackle the polyvalent counterions. This combined weak-strong coupling approach effectively leads to dressed interactions between polyvalent counterions and thus directly affects the correlation attraction mediated by polyvalent counterions between like-charged objects. The general theory is specifically applied to a system composed of two uniformly charged plane-parallel surfaces in the presence of salt and polyvalent counterions. In the strong coupling limit for polyvalent counterions the comparison with Monte-Carlo simulations shows good agreement for large enough values of the electrostatic coupling parameter. We delineate two limiting laws that in fact encompass all the Monte-Carlo data.",0912.5460v2 2012-04-01,Reconstruction of a Nonminimal Coupling Theory with Scale-invariant Power Spectrum,"A nonminimal coupling single scalar field theory, when transformed from Jordan frame to Einstein frame, can act like a minimal coupling one. Making use of this property, we investigate how a nonminimal coupling theory with scale-invariant power spectrum could be reconstructed from its minimal coupling counterpart, which can be applied in the early universe. Thanks to the coupling to gravity, the equation of state of our universe for a scale-invariant power spectrum can be relaxed, and the relation between the parameters in the action can be obtained. This approach also provides a means to address the Big-Bang puzzles and anisotropy problem in the nonminimal coupling model within Jordan frame. Due to the equivalence between the two frames, one may be able to find models that are free of the horizon, flatness, singularity as well as anisotropy problems.",1204.0189v2 2012-04-18,Reentrant enhancement of quantum fluctuations for symmetric environmental coupling,"The `system-plus-reservoir' (SPR) model is the most common and effective approach to study quantum dissipative effects. Indeed, it makes quantization possible by considering the whole energy-conserving system, while the reservoir's degrees of freedom, assumed to be harmonic, can be `traced out' by the path-integral technique, leading to a formulation that only includes the system of interest. In the standard SPR model the environment is only coupled with the system's coordinate and turns out to quench its quantum fluctuations. However, there are physical systems coupled with an environment whose `coordinates' and `momenta' can be completely interchangeable (e.g., magnets), so an SPR coupling must symmetrically affect both canonical variables. In this paper such a general environmental coupling is studied in the case of a harmonic oscillator. It is found that quantum fluctuations are generally enhanced by environmental coupling, with an unexpected nonmonotonic behavior. This leads one to speculate about the possibility that spin-lattice coupling could drive the 2D Heisenberg antiferromagnet to reach its quantum-critical point.",1204.4132v1 2013-09-26,$ttH$ Anomalous Coupling in Double Higgs Production,"We study the effects of top-Higgs anomalous coupling in the production of a pair of Higgs boson via gluon fusion at the Large Hadron Collider (LHC). The introduction of anomalous $ttH$ coupling can alter the hadronic double Higgs boson cross section and can lead to characteristic changes in certain kinematic distributions. We perform a global analysis based on available LHC data on the Higgs to constrain the parameters of $ttH$ anomalous coupling. Possible overlap of the predictions due to anomalous $ttH$ coupling with those due to anomalous trilinear Higgs coupling is also studied. We briefly discuss the effect of the anomalous $ttH$ coupling on the $HZ$ production via gluon fusion which is one of the main backgrounds in the $HH \to \gamma\gamma b {\bar b}$ channel.",1309.6907v2 2014-06-09,A unified operator splitting approach for multi-scale fluid-particle coupling in the lattice Boltzmann method,"A unified framework to derive discrete time-marching schemes for coupling of immersed solid and elastic objects to the lattice Boltzmann method is presented. Based on operator splitting for the discrete Boltzmann equation, second-order time-accurate schemes for the immersed boundary method, viscous force coupling and external boundary force are derived. Furthermore, a modified formulation of the external boundary force is introduced that leads to a more accurate no-slip boundary condition. The derivation also reveals that the coupling methods can be cast into a unified form, and that the immersed boundary method can be interpreted as the limit of force coupling for vanishing particle mass. In practice, the ratio between fluid and particle mass determines the strength of the force transfer in the coupling. The integration schemes formally improve the accuracy of first-order algorithms that are commonly employed when coupling immersed objects to a lattice Boltzmann fluid. It is anticipated that they will also lead to superior long-time stability in simulations of complex fluids with multiple scales.",1406.2211v1 2014-06-18,Charge and spin polarized currents in mesoscopic rings with Rashba spin-orbit interactions coupled to an electron reservoir,"The electronic states of a mesoscopic ring are assessed in the presence of Rashba Spin Orbit coupling and a $U(1)$ gauge field. Spin symmetric coupling to an ideal lead is implemented following B\""uttiker's voltage probe. The exact density of states is derived using the reservoir uncoupled eigenstates as basis functions mixed by the reservoir coupling. The decay time of uncoupled electron eigenstates is derived by fitting the broadening profiles. The spin and charge persistent currents are computed in the presence of the SO interaction and the reservoir coupling for two distinct scenarios of the electron filling fraction. The degradation of the persistent currents depends uniformly on the reservoir coupling but nonuniformly in temperature, the latter due to the fact that currents emerge from different depths of the Fermi sea, and thus for some regimes of flux, they are provided with a protective gap. Such flux regimes can be tailored by the SO coupling for both charge and spin currents.",1406.4659v1 2014-06-27,Spin-phonon coupling in BaFe12O19 M-type hexaferrite,"The spin-phonon coupling in magnetic materials is due to the modulation of the exchange integral by lattice vibrations. BaFe12O19 M-type hexaferrite, which is the most used magnetic material as permanent magnet, transforms into ferromagnet at high temperatures, but no spin-phonon coupling was previously observed at this transition. In this letter, we investigated the temperature-dependent Raman spectra of polycrystalline BaFe12O19 M-type hexaferrite from room temperature up to 780 K to probe spin-phonon coupling at the ferrimagnetic transition. An anomaly was observed in the position of the phonon attributed to the Fe(4)O6 octahedra, evidencing the presence of a spin-phonon coupling in BaM in the ferrimagnetic transition at 720 K. The results also confirmed the spin-phonon coupling is different for each phonon even when they couple with the same spin configuration.",1406.7334v2 2016-05-13,Chimera patterns induced by distance-dependent power-law coupling in ecological networks,"This paper reports the occurrence of several chimera patterns and the associated transitions among them in a network of coupled oscillators, which are connected by a long range interaction that obeys a distance-dependent power law. This type of interaction is common in physics and biology and constitutes a general form of coupling scheme, where by tuning the power-law exponent of the long range interaction the coupling topology can be varied from local via nonlocal to global coupling. To explore the effect of the power-law coupling on collective dynamics, we consider a network consisting of a realistic ecological model of oscillating populations, namely the Rosenzweig--MacArthur model, and show that the variation of the power-law exponent mediates transitions between spatial synchrony and various chimera patterns. We map the possible spatiotemporal states and their scenarios that arise due to the interplay between the coupling strength and the power-law exponent.",1605.04120v2 2016-08-29,When polarons meet polaritons: Exciton-vibration interactions in organic molecules strongly coupled to confined light fields,"We present a microscopic semi-analytical theory for the description of organic molecules interacting strongly with a cavity mode. Exciton-vibration coupling within the molecule and exciton-cavity interaction are treated on an equal footing by employing a temperature-dependent variational approach. The interplay between strong exciton-vibration coupling and strong exciton-cavity coupling gives rise to a hybrid ground state, which we refer to as the lower polaron polariton. Explicit expressions for the ground-state wave function, the zero-temperature quasiparticle weight of the lower polaron polariton, the photoluminescence line strength, and the mean number of vibrational quanta are obtained in terms of the optimal variational parameters. The dependence of these quantities upon the exciton-cavity coupling strength reveals that strong cavity coupling leads to an enhanced vibrational dressing of the cavity mode, and at the same time a vibrational decoupling of the dark excitons, which in turn results in a lower polaron polariton resembling a single-mode dressed bare lower polariton in the strong-coupling regime. Thermal effects on several observables are briefly discussed.",1608.08019v2 2017-06-27,Bound pulse trains in arrays of coupled spatially extended dynamical systems,"We study the dynamics of an array of nearest-neighbor coupled spatially distributed systems each generating a periodic sequence of short pulses. We demonstrate that unlike a solitary system generating a train of equidistant pulses, an array of such systems can produce a sequence of clusters of closely packed pulses, with the distance between individual pulses depending on the coupling phase. This regime associated with the formation of locally coupled pulse trains bounded due to a balance of attraction and repulsion between them is different from the pulse bound states reported earlier in different laser, plasma, chemical, and biological systems. We propose a simplified analytical description of the observed phenomenon, which is in a good agreement with the results of direct numerical simulations of a model system describing an array of coupled mode-locked lasers.",1706.08802v1 2017-06-27,Exact functionals for correlated electron-photon systems,"For certain correlated electron-photon systems we construct the exact density-to-potential maps, which are the basic ingredients of a density-functional reformulation of coupled matter-photon problems. We do so for numerically exactly solvable models consisting of up to four fermionic sites coupled to a single photon mode. We show that the recently introduced concept of the intra-system steepening (T.Dimitrov et al., 18, 083004 NJP (2016)) can be generalized to coupled fermion-boson systems and that the intra-system steepening indicates strong exchange-correlation (xc) effects due to the coupling between electrons and photons. The reliability of the mean-field approximation to the electron-photon interaction is investigated and its failure in the strong coupling regime analyzed. We highlight how the intra-system steepening of the exact density-to-potential maps becomes apparent also in observables such as the photon number or the polarizability of the electronic subsystem. We finally show that a change in functional variables can make these observables behave more smoothly and exemplify that the density-to-potential maps can give us physical insights into the behavior of coupled electron-photon systems by identifying a very large polarizability due to ultra-strong electron-photon coupling.",1706.08852v1 2017-10-06,Input-output theory for spin-photon coupling in Si double quantum dots,"The interaction of qubits via microwave frequency photons enables long-distance qubit-qubit coupling and facilitates the realization of a large-scale quantum processor. However, qubits based on electron spins in semiconductor quantum dots have proven challenging to couple to microwave photons. In this theoretical work we show that a sizable coupling for a single electron spin is possible via spin-charge hybridization using a magnetic field gradient in a silicon double quantum dot. Based on parameters already shown in recent experiments, we predict optimal working points to achieve a coherent spin-photon coupling, an essential ingredient for the generation of long-range entanglement. Furthermore, we employ input-output theory to identify observable signatures of spin-photon coupling in the cavity output field, which may provide guidance to the experimental search for strong coupling in such spin-photon systems and opens the way to cavity-based readout of the spin qubit.",1710.02508v1 2017-10-18,Dynamical analysis for a scalar-tensor model with kinetic and non-minimal couplings,"We study the autonomous system for a scalar-tensor model of dark energy with non-minimal coupling to curvature and non-minimal kinetic coupling to the Einstein tensor. The critical points describe important stable asymptotic scenarios including quintessence, phantom and de Sitter attractor solutions. Two functional forms for the coupling functions and the scalar potential were considered: power-law and exponential functions of the scalar field. For power-law couplings, the restrictions on stable quintessence and phantom solutions lead to asymptotic freedom regime for the gravitational interaction. The model with dimensionless kinetic coupling constant gives stable de Sitter solutions. For the exponential functions the stable quintessence, phantom or de Sitter solutions, allow asymptotic behaviors where the effective Newtonian coupling can reach either the asymptotic freedom regime or constant value. The phantom solutions could be realized without appealing to ghost degrees of freedom. Transient inflationary and radiation dominated phases can also be described.",1710.07273v1 2017-10-27,"Coupled Coincidence Point of $φ$-Contraction Type $T$-Coupling and $(φ,ψ)$-Contraction Type Coupling in Metric Spaces","In this research article, we discuss two topics. Firstly, we introduce SCC-Map and $\phi$-contraction type $T$-coupling. By using these two definitions, we generalize $\phi$-contraction type coupling given by H. Aydi et al. [3] to $\phi$-contraction type $T$-coupling and proved the existence theorem of coupled coincidence point for metric spaces which are not complete. Secondly, we attempt to give an answer to an open problem presented by choudhury et al. [7] concerning the investigation of fixed point and related properties for couplings satisfying other type of inequalities. In this direction we prove the existence and uniqueness theorem of strong coupled fixed point for $(\phi,\psi)$-contraction type coupling. We give examples to illustrate our main results.",1710.10054v1 2017-12-22,Backstepping Control of Coupled Linear Parabolic PIDEs with Spatially-Varying Coefficients,"This paper considers the backstepping design of state feedback controllers for coupled linear parabolic partial integro-differential equations (PIDEs) of Volterra-type with distinct diffusion coefficients, spatially-varying parameters and mixed boundary conditions. The corresponding target system is a cascade of parabolic PDEs with local couplings allowing a direct specification of the closed-loop stability margin. The determination of the state feedback controller leads to kernel equations, which are a system of coupled linear second-order hyperbolic PIDEs with spatially-varying coefficients and rather unusual boundary conditions. By extending the method of successive approximations for the scalar case to the considered system class, the well-posedness of these kernel equations is verified by providing a constructive solution procedure. This results in a systematic method for the backstepping control of coupled parabolic PIDEs as well as PDEs. The applicability of the new backstepping design method is confirmed by the stabilization of two coupled parabolic PIDEs with Dirichlet/Robin unactuated boundaries and a coupled Neumann/Dirichlet actuation.",1712.08406v1 2017-12-22,Geometric Analysis of Synchronization in Neuronal Networks with Global Inhibition and Coupling Delays,"We study synaptically coupled neuronal networks to identify the role of coupling delays in network's synchronized behaviors. We consider a network of excitable, relaxation oscillator neurons where two distinct populations, one excitatory and one inhibitory, are coupled and interact with each other. The excitatory population is uncoupled, while the inhibitory population is tightly coupled. A geometric singular perturbation analysis yields existence and stability conditions for synchronization states under different firing patterns between the two populations, along with formulas for the periods of such synchronous solutions. Our results demonstrate that the presence of coupling delays in the network promotes synchronization. Numerical simulations are conducted to supplement and validate analytical results. We show the results carry over to a model for spindle sleep rhythms in thalamocortical networks, one of the biological systems which motivated our study. The analysis helps to explain how coupling delays in either excitatory or inhibitory synapses contribute to producing synchronized rhythms.",1712.08547v2 2017-12-28,Eikonal Scattering and Asymptotic Superluminality of Massless Higher Spin Fields,"We consider scattering of massless higher-spin particles in the eikonal regime in four dimensions. By demanding the absence of asymptotic superluminality, corresponding to positivity of the eikonal phase, we place constraints on the possible cubic couplings which can appear in the theory. The cubic couplings come in two types: lower-derivative non-abelian vertices, and higher-derivative abelian vertices made out of gauge-invariant curvature tensors. We find that the abelian couplings between massless higher spins lead to an asymptotic time advance for certain choices of polarizations, indicating that these couplings should be absent unless new states come in at the scale suppressing the derivatives in these couplings. A subset of non-abelian cubic couplings are consistent with eikonal positivity, but are ruled out by consistency of the four-particle amplitude away from the eikonal limit. The eikonal constraints are therefore complementary to the four-particle test, ruling out even trivial cubic curvature couplings in any theory with a finite number of massless higher spins and no new physics at the scale suppressing derivatives in these vertices.",1712.10021v2 2018-09-07,Observation of ultra-strong spin-motion coupling for cold atoms in optical microtraps,"We realize a mechanical analogue of the Dicke model, achieved by coupling the spin of individual neutral atoms to their quantized motion in an optical trapping potential. The atomic spin states play the role of the electronic states of the atomic ensemble considered in the Dicke model, and the in-trap motional states of the atoms correspond to the states of the electromagnetic field mode. The coupling between spin and motion is induced by an inherent polarization gradient of the trapping light fields, which leads to a spatially varying vector light shift. We experimentally show that our system reaches the ultra-strong coupling regime, i.e., we obtain a coupling strength which is a significant fraction of the trap frequency. Moreover, with the help of an additional light field, we demonstrate the in-situ tuning of the coupling strength. Beyond its fundamental interest, the demonstrated one-to-one mapping between the physics of optically trapped cold atoms and the Dicke model paves the way for implementing protocols and applications that exploit extreme coupling strengths.",1809.02488v1 2019-09-03,Stability Analysis of Interface Conditions for Ocean-Atmosphere Coupling,"In this paper we analyze the stability of different coupling strategies for multidomain PDEs that arise in general circulation models used in climate simulations. We focus on fully coupled ocean-atmosphere models that are needed to represent and understand the complicated interactions of these two systems, becoming increasingly important in climate change assessment in recent years. Numerical stability issues typically arise because of different time-stepping strategies applied to the coupled PDE system. In particular, the contributing factors include using large time steps, lack of accurate interface flux, and singe-iteration coupling. We investigate the stability of the coupled ocean-atmosphere models for various interface conditions such as the Dirichlet-Neumann condition and the bulk interface condition, which is unique to climate modeling. By analyzing a simplified model, we demonstrate how the parameterization of the bulk condition and other numerical and physical parameters affect the coupling stability.",1909.00916v2 2020-12-07,Graphene plasmon-phonon coupled modes at the exceptional point,"Properties of graphene plasmons are greatly affected by their coupling to phonons. While such coupling has been routinely observed in both near-field and far-field graphene spectroscopy, the interplay between coupling strength and mode losses, and its exceptional point physics has not been discussed. By applying a non-Hermitian framework, we identify the transition point between strong and weak coupling as the exceptional point. Enhanced sensitivity to perturbations near the exceptional point is observed by varying the coupling strength and through gate modulation of the graphene Fermi level. Finally, we also show that the transition from strong to weak coupling is observable by changing the incident angle of radiation.",2012.03875v1 2020-12-10,Crossover between Strongly-coupled and Weakly-coupled Exciton Superfluids,"In fermionic systems, superconductivity and superfluidity are enabled through the condensation of fermion pairs. The nature of this condensate can be tuned by varying the pairing strength, with weak coupling yielding a BCS-like condensate and strong coupling resulting in a BEC-like process. However, demonstration of this cross-over has remained elusive in electronic systems. Here we study graphene double-layers separated by an atomically thin insulator. Under applied magnetic field, electrons and holes couple across the barrier to form bound magneto-excitons whose pairing strength can be continuously tuned by varying the effective layer separation. Using temperature-dependent Coulomb drag and counter-flow current measurements, we demonstrate the capability to tune the magneto-exciton condensate through the entire weak-coupling to strong-coupling phase diagram. Our results establish magneto-exciton condensates in graphene as a model platform to study the crossover between two Bosonic quantum condensate phases in a solid state system.",2012.05916v1 2020-12-12,Dilemma in strongly correlated materials: Hund's metal vs relativistic Mott insulator,"We point out the generic competition between the Hund's coupling and the spin-orbit coupling in correlated materials, and this competition leads to an electronic dilemma between the Hund's metal and the relativistic insulators. Hund's metals refer to the fate of the would-be insulators where the Hund's coupling suppresses the correlation and drives the systems into correlated metals. Relativistic Mott insulators refer to the fate of the would-be metals where the relativistic spin-orbit coupling enhances the correlation and drives the systems into Mott insulators. These contradictory trends are naturally present in many correlated materials. We study the competition between Hund's coupling and spin-orbit coupling in correlated materials and explore the interplay and the balance from these two contradictory trends. The system can become a spin-orbit-coupled Hund's metal or a Hund's assisted relativistic Mott insulator. Our observation could find a broad application and relevance to many correlated materials with multiple orbitals.",2012.06752v1 2020-12-21,Exciton-phonon coupling strength in single-layer MoSe2 at room temperature,"Single-layer transition metal dichalcogenides are at the center of an ever increasing research effort both in terms of fundamental physics and applications. Exciton-phonon coupling plays a key role in determining the (opto)electronic properties of these materials. However, the exciton-phonon coupling strength has not been measured at room temperature. Here, we develop two-dimensional micro-spectroscopy to determine exciton-phonon coupling of single-layer MoSe2. We detect beating signals as a function of waiting time T, induced by the coupling between the A exciton and the A'1 optical phonon. Analysis of two-dimensional beating maps combined with simulations provides the exciton-phonon coupling. The Huang-Rhys factor of ~1 is larger than in most other inorganic semiconductor nanostructures. Our technique offers a unique tool to measure exciton-phonon coupling also in other heterogeneous semiconducting systems with a spatial resolution ~260 nm, and will provide design-relevant parameters for the development of optoelectronic devices.",2012.11492v1 2012-05-12,Transport on coupled spatial networks,"Transport processes on spatial networks are representative of a broad class of real world systems which, rather than being independent, are typically interdependent. We propose a measure of utility to capture key features that arise when such systems are coupled together. The coupling is defined in a way that is not solely topological, relying on both the distribution of sources and sinks, and the method of route assignment. Using a toy model, we explore relevant cases by simulation. For certain parameter values, a picture emerges of two regimes. The first occurs when the flows go from many sources to a small number of sinks. In this case, network utility is largest when the coupling is at its maximum and the average shortest path is minimized. The second regime arises when many sources correspond to many sinks. Here, the optimal coupling no longer corresponds to the minimum average shortest path, as the congestion of traffic must also be taken into account. More generally, results indicate that coupled spatial systems can give rise to behavior that relies subtly on the interplay between the coupling and randomness in the source-sink distribution.",1205.2776v2 2017-05-03,From collective oscillation to chimera state in a nonlocally excitable system,"Chimera states, which consist of coexisting domains of spatially coherent and incoherent dynamics, have been widely found in nonlocally coupled oscillatory systems. We demonstrate for the first time that chimera states can emerge from excitable systems under nonlocal coupling in which isolated units only allow for the equilibrium. We theoretically reveal that nonlocal coupling induced collective oscillation is behind the occurrence of the chimera states. We find two different types of chimera states, phase-chimera state and excitability-chimera states, depending on the coupling strength. At weak coupling strength where collective oscillation is localized around the unstable homogeneous equilibrium, the chimera states are similar to the ones in nonlocally coupled phase oscillators. For the chimera states at strong coupling strength, the dynamics of both coherent units and incoherent units shift back and forth between low amplitude oscillation induced by collective oscillation and high amplitude oscillation induced by excitability of local units.",1705.01339v1 2017-05-18,Chimera states: Effects of different coupling topologies,"Collective behavior among coupled dynamical units can emerge in various forms as a result of different coupling topologies as well as different types of coupling functions. Chimera states have recently received ample attention as a fascinating manifestation of collective behavior, in particular describing a symmetry breaking spatiotemporal pattern where synchronized and desynchronized states coexist in a network of coupled oscillators. In this perspective, we review the emergence of different chimera states, focusing on the effects of different coupling topologies that describe the interaction network connecting the oscillators. We cover chimera states that emerge in local, nonlocal and global coupling topologies, as well as in modular, temporal and multilayer networks. We also provide an outline of challenges and directions for future research.",1705.06786v1 2017-05-19,On the coupling time of the heat-bath process for the Fortuin-Kasteleyn random-cluster model,"We consider the coupling from the past implementation of the random-cluster heat-bath process, and study its random running time, or coupling time. We focus on hypercubic lattices embedded on tori, in dimensions one to three, with cluster fugacity at least one. We make a number of conjectures regarding the asymptotic behaviour of the coupling time, motivated by rigorous results in one dimension and Monte Carlo simulations in dimensions two and three. Amongst our findings, we observe that, for generic parameter values, the distribution of the appropriately standardized coupling time converges to a Gumbel distribution, and that the standard deviation of the coupling time is asymptotic to an explicit universal constant multiple of the relaxation time. Perhaps surprisingly, we observe these results to hold both off criticality, where the coupling time closely mimics the coupon collector's problem, and also at the critical point, provided the cluster fugacity is below the value at which the transition becomes discontinuous. Finally, we consider analogous questions for the single-spin Ising heat-bath process.",1705.07189v1 2017-05-24,Dynamics of an ultra-strongly-coupled system interacting with a driven nonlinear resonator,"In the ultra-strong coupling regime of a light-matter system, the ground state exhibits non-trivial entanglement between the atom and photons. For the purposes of exploring the measurement and control of this ground state, here we analyze the dynamics of such an ultra-strongly-coupled system interacting with a driven nonlinear resonator acting as a measurement apparatus. Interestingly, although the coupling between the atom and the nonlinear resonator is much smaller than the typical energy scales of the ultra-strongly-coupled system, we show that we can generate a strong correlation between the nonlinear resonator and the light-matter system. A subsequent coarse- grained measurement on the nonlinear resonator significantly affects the light-matter system, and the phase of the light changes depending on the measurement results. Also, we investigate the conditions for when the nonlinear resonator can be entangled with the ultra-strongly coupled system, which is the mechanism that allows us to project the ground state of the ultra-strongly coupled system into a non-energy eigenstate.",1705.08688v2 2017-09-07,Rotational strain in Weyl semimetals: A continuum approach,"The coupling of lattice deformations to the low energy electronic excitations of Dirac matter involve novel types of electron--phonon couplings as the celebrated elastic gauge fields first analyzed in graphene. In the continuum low energy approach, lattice deformations coupling to the electronic degrees of freedom are characterized by the (symmetric) strain tensor defined in elasticity theory. We review these couplings in Weyl semimetals and examine the coupling of electronic excitations to the antisymmetric part of the deformation gradient tensor associated to rotational strain. The new couplings, absent in the two dimensional materials, have important physical implications: they give rise to new elastic gauge fields, contribute to the deformation potential, tilt the cones and generate new pseudo--Zeeman couplings.",1709.02394v2 2017-09-29,The effect on Kerr comb generation in a clockwise and counter-clockwise mode coupled microcavity,"We study the impact of inherent mode coupling between clockwise (CW) and counter-clockwise (CCW) modes on Kerr comb generation in a small whispering-gallery mode microcavity. Our numerical analysis using a coupled Lugiato-Lefever equation reveals the range of the coupling strength in which a soliton pulse can be obtained in the CW direction. It also showed that CCW comb power depends on the coupling strength between the CW and CCW modes. In addition to the simulation, we conducted an experiment to confirm that the power ratio between the CW and CCW comb modes depends on the coupling strength, and the experimental results agree well with the simulation results. This study helps us to understand the relationship between CW and CCW mode coupling and Kerr comb generation, and the effect on soliton formation.",1709.10226v1 2018-03-06,Refrigeration beyond weak internal coupling,"We investigate the performance of a three-spin quantum absorption refrigerator using a refined open quantum system model valid across all inter-spin coupling strengths. It describes the transition between previous approximate models for the weak and the ultrastrong coupling limit, and it predicts optimal refrigeration for moderately strong coupling, where both approximations are inaccurate. Two effects impede a more effective cooling: the coupling between the spins no longer reduces to a simple resonant energy exchange (the rotating wave approximation fails), and the interactions with the thermal baths become sensitive to the level splitting, thus opening additional heat channels between the reservoirs. We identify the modified conditions of refrigeration as a function of the inter-spin coupling strength, and we show that, contrary to intuition, a high-temperature work reservoir thwarts refrigeration in the strong coupling regime.",1803.02002v2 2018-03-13,Cross-correlation between photons and phonons in quadratically coupled optomechanical systems,"We study photon, phonon statistics and the cross-correlation between photons and phonons in a quadratically coupled optomechanical system. Photon blockade, phonon blockade and strongly anticorrelated photons and phonons can be observed in the same parameter regime with the effective nonlinear coupling between the optical and mechanical modes, enhanced by a strong optical driving field. Interestingly, an optimal value of the effective nonlinear coupling strength for the photon blockade is not within the strong nonlinear coupling regime. This abnormal phenomenon results from the destructive interference between different paths for two-photon excitation in the optical mode with a moderate effective nonlinear coupling strength. Further more, we show that phonon (photon) pairs and correlated photons and phonons can be generated in the strong nonlinear coupling regime with a proper detuning between the weak mechanical driving field and mechanical mode. Our results open up a way to generate anticorrelated and correlated photons and phonons, which may have important applications in quantum information processing.",1803.04671v2 2018-03-17,Two-color electromagnetically induced transparency via modulated coupling between a mechanical resonator and a qubit,"We discuss level splitting and sideband transitions induced by a modulated coupling between a superconducting quantum circuit and a nanomechanical resonator. First, we show how to achieve an unconventional time-dependent longitudinal coupling between a flux (transmon) qubit and the resonator. Considering a sinusoidal modulation of the coupling strength, we find that a first-order sideband transition can be split into two. Moreover, under the driving of a red-detuned field, we discuss the optical response of the qubit for a resonant probe field. We show that level splitting induced by modulating this longitudinal coupling can enable two-color electromagnetically induced transparency (EIT), in addition to single-color EIT. In contrast to standard predictions of two-color EIT in atomic systems, we apply here only a single drive (control) field. The monochromatic modulation of the coupling strength is equivalent to employing two eigenfrequency-tunable mechanical resonators. Both drive-probe detuning for single-color EIT and the distance between transparent windows for two-color EIT, can be adjusted by tuning the modulation frequency of the coupling.",1803.06513v2 2018-03-24,Controllable nonlinearity in a dual-coupling optomechanical system under a weak-coupling regime,"Strong quantum nonlinearity gives rise to many interesting quantum effects and has wide applications in quantum physics. Herewe investigate the quantum nonlinear effect of an optomechanical system (OMS) consisting of both linear and quadratic coupling. Interestingly, a controllable optomechanical nonlinearity is obtained by applying a driving laser into the cavity. This controllable optomechanical nonlinearity can be enhanced into a strong coupling regime, even if the system is initially in the weak-coupling regime. Moreover, the system dissipation can be suppressed effectively, which allows the appearance of phonon sideband and photon blockade effects in the weak-coupling regime. This work may inspire the exploration of a dual-coupling optomechanical system as well as its applications in modern quantum science.",1803.09048v1 2018-06-09,Sparse Bayesian Learning-Based Direction Finding Method With Unknown Mutual Coupling Effect,"The imperfect array degrades the direction finding performance. In this paper, we investigate the direction finding problem in uniform linear array (ULA) system with unknown mutual coupling effect between antennas. By exploiting the target sparsity in the spatial domain, sparse Bayesian learning (SBL)-based model is proposed and converts the direction finding problem into a sparse reconstruction problem. In the sparse-based model, the \emph{off-grid} errors are introduced by discretizing the direction area into grids. Therefore, an off-grid SBL model with mutual coupling vector is proposed to overcome both the mutual coupling and the off-grid effect. With the distribution assumptions of unknown parameters including the noise variance, the off-grid vector, the received signals and the mutual coupling vector, a novel direction finding method based on SBL with unknown mutual coupling effect named DFSMC is proposed, where an expectation-maximum (EM)-based step is adopted by deriving the estimation expressions for all the unknown parameters theoretically. Simulation results show that the proposed DFSMC method can outperform state-of-the-art direction finding methods significantly in the array system with unknown mutual coupling effect.",1806.03409v2 2018-06-11,Effects of quark-matter symmetry energy on hadron-quark coexistence in neutron-star matter,"We examine the effects of the isovector-vector coupling and hypercharge-vector coupling in quark matter on hadron-quark coexistence in neutron-star matter. The relativistic mean field theory with the TM1 parameter set and an extended TM1 parameter set are used to describe hadronic matter, and the Nambu-Jona-Lasinio model with scalar, isoscalar-vector, isovector-vector and hypercharge-vector couplings is used to describe deconfined quark matter. The hadron-quark phase transition is constructed via the Gibbs conditions for phase equilibrium. The isovector-vector and hypercharge-vector couplings in quark matter enhance the symmetry energy and hypercharge symmetry energy in neutron-star matter, while their effects are found to be suppressed at high densities by the strange quarks. As a result, the hadron-quark mixed phase shrinks with only isovector-vector coupling and moves to higher density with isovector-vector and hypercharge-vector couplings. The maximum mass of neutron-star increases slightly with isovector-vector and hypercharge-vector couplings.",1806.03760v2 2018-06-21,Is the Vlasov equation valid for Yukawa plasmas?,"We analyze the Vlasov dispersion relation for Yukawa plasmas in three dimensions for the purpose of identifying coupling parameter domains where the Vlasov approach is justified and the existence of a well-developed RPA type collective excitation is allowed. We establish a rigorous lower bound for the coupling parameter, below which there can be no real solution to the Vlasov dispersion relation. In the coupling domain, where weakly damped solutions do exist, we have focused on the long-wavelength acoustic regime where we establish more restrictive estimates for the lower bound of the coupling parameter. We also derive a general formula for the corresponding acoustic phase velocity, valid over a wide range of coupling parameter/screening parameter ratios above the lower bound. We conclude that the Vlasov approach is tenable only above a critical coupling value. Comparison with Molecular Dynamics simulation results further highlights the limitations of the Vlasov approximation for weakly coupled Yukawa plasmas.",1806.08431v1 2018-06-23,Coupling Quantum Emitters in WSe2 Monolayers to a Metal-Insulator-Metal Waveguide,"Coupling single photon emitters to surface plasmons provides a versatile ground for on chip quantum photonics. However, achieving good coupling efficiency requires precise alignment of both the position and dipole orientation of the emitter relative to the plasmonic mode. We demonstrate coupling of single emitters in the 2-D semiconductor, WSe2 self-aligned with propagating surface plasmon polaritons in silver-air-silver, metal-insulator-metal waveguides. The waveguide produces strain induced defects in the monolayer which are close to the surface plasmon mode with favorable dipole orientations for optimal coupling. We measure an average enhancement in the rate of spontaneous emission by a factor of 1.89 for coupling the single defects to the plasmonic waveguide. This architecture provides an efficient way of coupling single photon emitters to propagating plasmons which is an important step towards realizing active plasmonic circuits on chip.",1806.08973v2 2018-07-04,Quantum correlations in two-level atomic system over Herring-Flicker coupling,"We study the thermal quantum correlations in tripartite atomic system under the existence of Herring-Flicker (HF) coupling among the atoms. We explore two topologically distinct configurations of three coupled two-level atoms, viz., loop and line, differing in their coupling pattern. Further, the systems having asymmetric arrangement of atoms are quantum mechanically correlated more strongly than systems having symmetric arrangements. The variable nature of HF coupling leads to the increase of both concurrence and discord from zero to a saturation value from where they decrease to zero as a function of inter-atomic distance. Further separation leads to both the quantities attaining another saturation value. This controlled correlations play an important role in the design of quantum data buses that can transfer quantum states to establish quantum communication. The systems coupled via HF coupling will be efficient for this task as they are maximally entangled in parametrically controlled manner. Thus, these systems will be propitious for various quantum protocols such as secure communication, quantum cryptography, quantum key distribution etc.",1807.01805v4 2018-07-12,Investigation of a Multiple-Timescale Turbulence-Transport Coupling Method in the Presence of Random Fluctuations,"One route to improved predictive modeling of magnetically confined fusion reactors is to couple transport solvers with direct numerical simulations (DNS) of turbulence, rather than with surrogate models. An additional challenge presented by coupling directly with DNS is that the inherent fluctuations in the turbulence, which limit the convergence achievable in the transport solver. In this article, we investigate the performance of one numerical coupling method in the presence of turbulent fluctuations. To test a particular numerical coupling method for the transport solver, we use an autoregressive-moving-average model to efficiently generate stochastic fluctuations with statistical properties resembling those of a gyrokinetic simulation. These fluctuations are then added to a simple, solvable problem, and we examine the behavior of the coupling method. We find that monitoring the residual as a proxy for the error can be misleading. From a pragmatic point of view, this study aids us in the full problem of transport coupled to DNS by predicting the amount of averaging required to reduce the fluctuation error and obtain a specific level of accuracy.",1807.04779v1 2018-07-13,Quansinormal modes of static and spherically symmetric black holes with the derivative coupling,"We investigate the quasinormal modes of a class of static and spherically symmetric black holes with the derivative coupling. The derivative coupling has rarely been paid attention to the study of black hole quasinormal modes. Specifically, we study the effect of derivative coupling on the quasinormal modes for four kinds of black holes. They are Reissner-Nordstrom black holes, Bardeen black holes, noncommunicative geometry inspired black holes and dilaton black holes. These black holes are not the solutions of vacuum Einstein equations which guarantees the effect of derivative coupling is not trivial. We find the influence of derivative coupling on the quasinormal modes roughly mimics the overtone numbers. In other words, there is a qualitative similarity in the trend of quasinormal modes frequencies due to increasing either the coupling constant and the overtone number.",1807.05024v2 2018-07-17,Effects of spin-orbit coupling on the optical response of a material,"We investigate the effects of spin-orbit coupling on the optical response of materials. In particular, we study the effects of the commutator between the spin-orbit coupling part of the potential and the position operator on the optical matrix elements. Using a formalism that separates a fullyrelativistic Kleinman-Bylander pseudopotential into the scalar-relativistic and spin-orbit-coupling parts, we calculate the contribution of the commutator arising from spin-orbit coupling to the squared optical matrix elements of isolated atoms, monolayer transition metal dichalcogenides, and topological insulators. In the case of isolated atoms from H ($Z = 1$) to Bi ($Z = 83$), the contribution of spin-orbit coupling to the squared matrix elements can be as large as 14 %. On the other hand, in the cases of monolayer transition metal dichalcogenides and topological insulators, we find that this contribution is less than 1 % and that it is sufficient to calculate the optical matrix elements and subsequent physical quantities without considering the commutator arising from spin-orbit coupling.",1807.06669v1 2018-07-25,Strong microwave photon-magnon coupling in multiresonant dielectric antennas (Perspective),"Achieving quantum-level control over electromagnetic waves, magnetisation dynamics, vibrations and heat is invaluable for many practical application and possible by exploiting the strong radiation-matter coupling. Most of the modern strong microwave photon-magnon coupling developments rely on the integration of metal-based microwave resonators with a magnetic material. However, it has recently been realised that all-dielectric resonators made of or containing magneto-insulating materials can operate as a standalone strongly-coupled system characterised by low dissipation losses and strong local microwave field enhancement. Here, after a brief overview of recent developments in the field, I discuss examples of such dielectric resonant systems and demonstrate their ability to operate as multiresonant antennas for light, microwaves, magnons, sound, vibrations and heat. This multiphysics behaviour opens up novel opportunities for the realisation of multiresonant coupling such as, for example, photon-magnon-phonon coupling. I also propose several novel systems in which strong photon-magnon coupling in dielectric antennas and similar structures is expected to extend the capability of existing devices or may provide an entirely new functionality. Examples of such systems include novel magnetofluidic devices, high-power microwave power generators, and hybrid devices exploiting the unique properties of electrical solitons.",1807.09827v1 2018-07-31,Ultrastrong coupling between light and matter,"Ultrastrong coupling between light and matter has, in the past decade, transitioned from theoretical idea to experimental reality. It is a new regime of quantum light-matter interaction, going beyond weak and strong coupling to make the coupling strength comparable to the transition frequencies in the system. The achievement of weak and strong coupling has led to increased control of quantum systems and applications like lasers, quantum sensing, and quantum information processing. Here we review the theory of quantum systems with ultrastrong coupling, which includes entangled ground states with virtual excitations, new avenues for nonlinear optics, and connections to several important physical models. We also review the multitude of experimental setups, including superconducting circuits, organic molecules, semiconductor polaritons, and optomechanics, that now have achieved ultrastrong coupling. We then discuss the many potential applications that these achievements enable in physics and chemistry.",1807.11636v1 2018-12-07,Dual $Z_2$ Lattice Gauge Theory of the 3D Ising Model with both Nearest- and Next-Nearest-Neighbor Couplings,"It is known that the normal three-dimensional (3D) Ising model on a cubic lattice is dual to the Wegner's 3D $Z_2$ lattice gauge theory. Here we find an unusual $Z_2$ lattice gauge theory which is dual to the 3D Ising model with not only nearest-neighbor (nn) coupling, but also next-nearest-neighbor (nnn) coupling. Our gauge theory has on each edge four $Z_2$ variables that have product $+1$, each located on a vector perpendicular to the edge. The nn coupling in the Ising model maps to the plaquette term in the gauge theory where the four variables multiplied have their vectors pointing inward, while the nnn coupling maps to the coupling between the $Z_2$ variables on nearby vectors on each edge in the gauge theory. A Wilson loop observable in the gauge theory depends on a framing of a loop, and maps to a surface of flipped-sign nn and nnn couplings in the Ising model. Further numerical simulations could be made to explore the universality at the phase transition.",1812.02938v1 2019-01-01,Normal-mode splitting of four-level atom-cavity system under collective strong coupling,"We investigate the transmission spectrum of an optical cavity coupled with four-level atoms. Multiple normal-mode splitting peaks of the strongly coupled atom-cavity system are obtained as single cavity mode couples three separated atomic transitions simultaneously. We employ a confocal optical cavity and an ensemble of cold Rb-85 atoms for cavity quantum electrodynamics. We observe four normal-mode splitting peaks of the cavity transmission in the strong coupling regime due to collective enhancement of the atom-cavity coupling strength by ensemble of cold atoms. The experimental observations are consistent with the theoretical analysis. The multiple normal-mode excitation in the strongly coupled multi-level atom-cavity system may lead to practical application for realizing multi-channel all-optical devices.",1901.00127v1 2019-01-17,Hawking radiation for scalar fields by Einstein-Gauss-Bonnet-de Sitter black holes,"We study the greybody factor and power spectra of Hawking radiation for the minimally or nonminimally coupled scalar field with exact numerical method in spherically symmetric Einstein-Gauss-Bonnet-de Sitter black hole spacetime. The effects of scalar coupling constant, angular momentum number of scalar, spacetime dimension, cosmological constant and Gauss-Bonnet coupling constant on the Hawking radiation are studied in detail. Specifically, the Gauss-Bonnet coupling constant always increases the greybody factor in the entire energy regime. Different from the case of Schwarzschild-de Sitter black hole, the effects of the scalar coupling constant on the greybody factor are not monotonic but relevant to the values of Gauss-Bonnet coupling constant. Moreover, both these two coupling constants always suppress the power spectra of Hawking radiation in the whole energy regime.",1901.05749v1 2019-01-21,Non-collinear coupling across RuCo and RuFe alloys,"Spintronic applications, which rely on spin torques for operation, would greatly benefit from a non-collinear alignment between magnetizations of adjacent ferromagnetic layers for maximum performance and reliability. We demonstrate that such an alignment can be created and controlled by coupling two ferromagnetic layers across magnetic coupling layers. These coupling layers consist of a non-magnetic material, Ru, alloyed with ferromagnetic elements of Co or Fe. Changing the composition and thickness of the coupling layer enables control of the relative angle between the magnetizations of ferromagnetic layers between 0 and 180 degrees. The onset of the non-collinear alignment between ferromagnetic layers coincide with the advent of magnetic order in the coupling layer. This study will map the range of concentrations and thicknesses of RuCo and RuFe coupling layers that give rise to non-collinearity between Co layers.",1901.07055v1 2019-01-29,U(1)' coupling constant at low energies from heterotic orbifolds,"Additional Abelian gauge interactions are generic to string compactifications. In heterotic string models, gauge coupling unification of such forces and other gauge interactions is natural due to their common origin. In this letter we study systematically the 1-loop running of the coupling constants in effective vacua emerging from Z8 heterotic orbifold compactifications that provide the matter spectrum of the MSSM plus some vectorlike exotics, restricting to vacua that yield a non-anomalous U(1)' symmetry, gauge coupling unification and the observed values of known gauge couplings. We determine the low-energy value of the U(1)' coupling constant for different scales of supersymmetry breakdown. We find that the U(1)' coupling constant is quite restricted in string models to lie in the range 0.46-0.7 for low-scale supersymmetry or 0.44-0.6 in other cases. We argue that the phenomenology of these string vacua should be further explored to solve some extant issues, such as the stability of the Higgs vacuum.",1901.10102v2 2019-01-30,Analytical Approach to Study the Impacts of Mutual Coupling on Transmission Lines Protection Systems,"While there are numerous literatures that have addressed the impact of mutual coupling on the reliability and security of protection schemes and have provided possible mitigation solutions, there has not been adequate research and documentation presenting a comprehensive analytical approach to 1) estimate the magnitude of mutual coupling and 2) quantify the adverse impact of mutual coupling in real-life scenarios under several system faults across various types of protective elements. This should be considered as the first stage of any mutual coupling related study preceding the second stage in which the mitigation against mutual coupling is to be developed. The proposed methodology can be used to study the impact of mutual coupling on ground overcurrent relays, ground and phase distance as well as pilot protection schemes. As part of the proposed approach, EMT simulation is utilized to quantify the extent of sub-transient overshoot and current reversal that may have adverse impact on the performance of studied relays. A real-life case study within the ERCOT network has been used to demonstrate the proposed study approach.",1901.10675v1 2019-03-05,On the Global Synchronization of Pulse-coupled Oscillators Interacting on Chain and Directed Tree Graphs,"Driven by increased applications in biological networks and wireless sensor networks, synchronization of pulse-coupled oscillators (PCOs) has gained increased popularity. However, most existing results address the local synchronization of PCOs with initial phases constrained in a half cycle, and results on global synchronization from any initial condition are very sparse. In this paper, we address global PCO synchronization from an arbitrary phase distribution under chain or directed tree graphs. Our results differ from existing global synchronization studies on decentralized PCO networks in two key aspects: first, our work allows heterogeneous coupling functions, and we analyze the behavior of oscillators with perturbations on their natural frequencies; secondly, rather than requiring a large enough coupling strength, our results hold under any coupling strength between zero and one, which is crucial because a large coupling strength has been shown to be detrimental to the robustness of PCO synchronization to disturbances.",1903.01651v3 2019-04-30,Dynamics of strongly coupled disordered dissipative spin-boson systems,"Spin-boson Hamiltonians are an effective description for numerous quantum many-body systems such as atoms coupled to cavity modes, quantum electrodynamics in circuits and trapped ion systems. While reaching the limit of strong coupling is possible in current experiments, the understanding of the physics in this parameter regime remains a challenge, especially when disorder and dissipation are taken into account. Here we investigate a regime where the many-body spin dynamics can be related to a Ising energy function defined in terms of the spin-boson couplings. While in the coherent weak coupling regime it is known that an effective description in terms of spin Hamiltonian is possible, we show that a similar viewpoint can be adopted in the presence of dissipation and strong couplings. The resulting many-body dynamics features approximately thermal regimes, separated by out-of-equilibrium ones in which detailed balance is broken. Moreover, we show that under appropriately chosen conditions one can even achieve cooling of the spin degrees of freedom. This points towards the possibility of using strongly coupled dissipative spin-boson systems for engineering complex energy landscapes together with an appropriate cooling dynamics.",1904.13181v1 2019-11-18,Photoluminescence spectroscopy of hybridized exciton-polariton coupling in silicon nanodisks with nonradiative anapole radiations,"Semiconductor nanoparticles and nanostructures in the strong coupling regime exhibit an intriguing energy scale in the optical frequencies, which is specified by the Rabi splitting between the upper and lower exciton-polariton states. Technically, exciton-polaritons are part-light, part-matter quasiparticles that arise from the strong interaction of excitonic substances and photonic platforms. In this work, using full-wave numerical and theoretical studies, we showed the emergence of strong light-matter coupling between the nonradiating anapole states from an individual semiconductor nanodisk coupled to a J-aggregate fluorescent dye molecule resonating in the visible spectrum. By demonstrating the physical mechanism behind the observed energy splitting for various Lorentzian linewidth of excitonic material, we theoretically confirmed the obtained spectral responses by conducting photoluminescence spectroscopy analysis. The coupling of anapole resonances in semiconductor nanoparticles with excitonic levels can propose interesting possibilities for the control of directional light scattering in the strong coupling limit, and the dynamic tuning of deep-subwavelength light-matter coupled states by external stimuli.",1911.07740v1 2019-11-25,Strongly correlated Fermions strongly coupled to light,"Strong quantum correlations in matter are responsible for some of the most extraordinary properties of material, from magnetism to high-temperature superconductivity, but their integration in quantum devices requires a strong, coherent coupling with photons, which still represents a formidable technical challenge in solid state systems. In cavity quantum electrodynamics, quantum gases such as Bose-Einstein condensates or lattice gases have been strongly coupled with light. However, neither Fermionic quantum matter, comparable to electrons in solids, nor atomic systems with controlled interactions, have thus far been strongly coupled with photons. Here we report on the strong coupling of a quantum-degenerate unitary Fermi gas with light in a high finesse cavity. We map out the spectrum of the coupled system and observe well resolved dressed states, resulting from the strong coupling of cavity photons with each spin component of the gas. We investigate spin-balanced and spin-polarized gases and find quantitative agreement with ab-initio calculation describing light-matter interaction. Our system offers complete and simultaneous control of atom-atom and atom-photon interactions in the quantum degenerate regime, opening a wide range of perspectives for quantum simulation.",1911.11151v2 2019-12-03,Nanoscale Tantalum Layer Controlling the Magnetic Coupling between Two Ferromagnetic Electrodes via Insulator of a Magnetic Tunnel Junction,"Ability to tailor the nature of the magnetic coupling between two ferromagnetic electrodes can enable the realization of new spintronics device systems. This paper discusses our finding that deposition of an ultrathin tantalum (Ta) on the NiFe top electrode reversed the nature of inter-ferromagnetic electrode coupling. We observed that the deposition of ~ 5 nm Ta on the top of a magnetic tunnel junction with Ta( 2 nm)/Co(5 nm)/NiFe (5 nm)/AlOx( 2 nm)/NiFe (10-15 nm) configuration changed the magnetic coupling between two ferromagnetic electrodes from antiferromagnetic to ferromagnetic. We investigated Ta effect using multiple magnetic characterizations like ferromagnetic resonance, magnetometry, and polarized neutron reflectometry. Ferromagnetic resonance characterization was very sensitive for detecting the changes in magnetic coupling via the insulating spacer. This simple approach of adding Ta film to alter the magnetic coupling can impact the other burgeoning areas like molecular spintronics. We found that preexisting magnetic coupling between two ferromagnetic electrodes impacted the resultant magnetic properties of magnetic tunnel junctions based molecular spintronics devices.",1912.01331v1 2019-12-04,Improving the Spatial Resolution of Silicon Pixel Detectors through Sub-pixel Cross-coupling,"We present a concept to improve the spatial resolution of silicon pixel-detectors via the implementation of a sub-pixel cross-coupling, which introduces directional charge sharing between pixels. The charge-collection electrode is segmented into sub-pixels and each sub-pixel is coupled to the closest sub-pixel of the neighboring pixel. Such coupling schema is evaluated for a model sensor design with $50 \mu m \times 50 \mu m$ pixels and AC-coupled sub-pixels. A first-order SPICE simulation is used, to determine feasible coupling strengths and assess the influence on the charge-collection efficiency. The impact of the coupling strength on spatial resolution is studied with a dedicated simulation, taking into account charge-cloud evolution, energy-loss straggling, electronic noise, and the charge detection-threshold. Using simplifying assumptions, such as perpendicular tracks and no gaps between charge-collection electrodes, an improvement of the spatial resolution by up to approximately $30\%$ is obtained in comparison to the standard planar pixel layout.",1912.01902v3 2019-12-11,Single-photon cooling in microwave magneto-mechanics,"Cavity optomechanics, where photons are coupled to mechanical motion, provides the tools to control mechanical motion near the fundamental quantum limits. Reaching single-photon strong coupling would allow to prepare the mechanical resonator in non-Gaussian quantum states. Preparing massive mechanical resonators in such states is of particular interest for testing the boundaries of quantum mechanics. This goal remains however challenging due to the small optomechanical couplings usually achieved with massive devices. Here we demonstrate a novel approach where a mechanical resonator is magnetically coupled to a microwave cavity. We measure a single-photon coupling of $g_0/2 \pi \sim 3$ kHz, an improvement of one order of magnitude over current microwave optomechanical systems. At this coupling we measure a large single-photon cooperativity with $C_0 \gtrsim 10$, an important step to reach single-photon strong coupling. Such a strong interaction allows us to cool the massive mechanical resonator to a third of its steady state phonon population with less than two photons in the microwave cavity. Beyond tests for quantum foundations, our approach is also well suited as a quantum sensor or a microwave to optical transducer.",1912.05489v2 2019-12-20,First-order and continuous quantum phase transitions in the anisotropic quantum Rabi-Stark model,"Various quantum phase transitions in the anisotropic Rabi-Stark model with both the nonlinear Stark coupling and the linear dipole coupling between a two-level system and a single-mode cavity are studied in this work. The first-order quantum phase transitions are detected by the level crossing of the ground-state and the first-excited state with the help of the pole structure of the transcendental functions derived by the Bogoliubov operators approach. As the nonlinear Stark coupling is the same as the cavity frequency, this model can be solved by mapping to an effective quantum oscillator. All energy levels close at the critical coupling in this case, indicating continuous quantum phase transitions. The critical gap exponent is independent of the anisotropy as long as the counter-rotating wave coupling is present, but essentially changed if the counter-rotating wave coupling disappears completely. It is suggested that the gapless Goldstone mode excitations could appear above a critical coupling in the present model in the rotating-wave approximation.",1912.10042v2 2016-03-02,T-dual RR couplings on D-branes from S-matrix elements,"Using the linear T-dual ward identity associated with the NSNS gauge transformations, some RR couplings on D$_p$-branes have been found at order $O(\alpha'^2)$. We examine the $C^{(p-1)}$ couplings with the S-matrix elements of one RR, one graviton and one antisymmetric B-field vertex operators. We find the consistency of T-dual S-matrix elements and explicit results of scattering string amplitude and show that the string amplitude reproduces these couplings as well as some other couplings. This illustration is found for $C^{(p-3)}$ couplings in the literature which is extended to the $C^{(p-1)}$ couplings in this paper.",1603.00678v2 2016-03-18,Entanglement Entropy of the N=4 SYM spin chain,"We present a detailed study of the Entanglement Entropy (EE) of excited states in all closed rank one subsectors of N=4 SYM, namely SU(2), SU(1|1) and SL(2). Exploiting the techniques of the Coordinate and the Algebraic Bethe Ansatz we obtain the EE for spin chains with up to seven magnons, at leading order in the coupling expansion but exact in the length of the spin chain and of the part of it that we cut. Focusing on the superconformal primary operator with two magnons in the BMN limit, we derive analytic and exact, in the coupling $\lambda'$, expressions for the Renyi and the EE. The interpolating functions for the Renyi and the EE monotonically increase as the coupling increases from the weak coupling $\lambda' \rightarrow 0$ regime to the strong coupling $\lambda' \rightarrow \infty$ regime. This results to a violation of a certain bound for the EE that is present at weak coupling and confirms the physical intuition that entanglement increases when the coupling increases.",1603.05929v2 2016-10-07,The Role of Interaction in the Pairing of Two Spin-orbit Coupled Fermions,"We investigate the role of a repulsive s-wave interaction in the two-body problem in the presence of spin orbit couplings, motivated by current interests in exploring exotic superfluid phases in spin-orbit coupled Fermi gases. For weak spin orbit coupling where the density of states is not significantly altered, we analytically show that the high-energy states become more important in determining the binding energy when the interaction strength decreases. Consequently, tuning the interaction gives rise to a rich ground state behavior, including a zigzag of the ground state momentum or inducing transitions among the meta-stable states. By exactly solving the two-body problem for a spin-orbit coupled Fermi mixture, we demonstrate that our analysis can also apply to the case when the density of states is significantly modified by the spin-orbit coupling. Our findings pave the way for understanding and controlling the paring of fermions in the presence of spin orbit couplings.",1610.02927v2 2016-10-17,Coherent Atom-Phonon Interaction through Mode Field Coupling in Hybrid Optomechanical Systems,"We propose a novel type of optomechanical coupling which enables a tripartite interaction between a quantum emitter, an optical mode and a macroscopic mechanical oscillator. The interaction uses a mechanism we term mode field coupling: mechanical displacement modifies the spatial distribution of the optical mode field, which in turn modulates the atom-photon coupling rate. In properly designed multimode optomechanical systems, we can achieve situations in which mode field coupling is the only possible interaction pathway for the system. This enables, for example, swapping of a single excitation between emitter and phonon, creation of nonclassical states of motion and mechanical ground-state cooling in the bad-cavity regime. Importantly, the emitter-phonon coupling rate can be enhanced through an optical drive field, allowing active control of strong atom-phonon coupling for realistic experimental parameters.",1610.05153v1 2016-10-19,Boundary Causality vs Hyperbolicity for Spherical Black Holes in Gauss-Bonnet,"We explore the constraints boundary causality places on the allowable Gauss-Bonnet gravitational couplings in asymptotically AdS spaces, specifically considering spherical black hole solutions. We additionally consider the hyperbolicity properties of these solutions, positing that hyperbolicity-violating solutions are sick solutions whose causality properties provide no information about the theory they reside in. For both signs of the Gauss-Bonnet coupling, spherical black holes violate boundary causality at smaller absolute values of the coupling than planar black holes do. For negative coupling, as we tune the Gauss-Bonnet coupling away from zero, both spherical and planar black holes violate hyperbolicity before they violate boundary causality. For positive coupling, the only hyperbolicity-respecting spherical black holes which violate boundary causality do not do so appreciably far from the planar bound. Consequently, eliminating hyperbolicity-violating solutions means the bound on Gauss-Bonnet couplings from the boundary causality of spherical black holes is no tighter than that from planar black holes.",1610.06078v1 2016-12-02,Novel Propagation Model of Degenerate Band Edge Modes Using Dual Non-identical Pair of Coupled Transmission Lines,"We present a novel propagation medium using a pair of non-identical coupled transmission lines. The medium is referred to as `butterfly' structure and is composed of four coupled transmission lines. These four coupled transmission lines generate higher-order dispersion modes by coupling the modes supported on each of the transmission lines. When these transmission line pairs are placed inside a circular waveguide, they support a strong TM01-like Degenerate Band Edge mode. This property can be used to enhance coupling of the electron beams to RF waves for high-power Traveling Wave Tubes. In this paper, we present the slow wave characteristics and Degenerate Band Edge mode formation using the coupled pair of transmission lines.",1612.00844v1 2017-07-06,Stability of entrainment of a continuum of coupled oscillators,"We examine the design of the entrainment process for an uncountably infinite collection of coupled phase oscillators that are all subject to the same periodic driving signal. In the absence of coupling, an appropriately designed input can result in each oscillator attaining the frequency of the driving signal, with a phase offset determined by its natural frequency. We consider a special case of interacting oscillators in which the coupling tends to destabilize the phase configuration to which the driving signal would send the collection in the absence of coupling. In this setting we derive stability results that characterize the trade-off between the effects of driving and coupling, and compare these results to the well-known Kuramoto model of a collection of free-running coupled oscillators.",1707.01599v3 2017-11-13,Multiple Couplings and Renormalization Scheme Ambiguities,"The ambiguities inherent in renormalization are considered when using mass-independent renormalization in massless theories that involve two coupling coupling constants. We review how there is no renormalization scheme in which the beta-functions can be chosen to vanish beyond a certain order in perturbation theory, but that the beta-functions always contain ambiguities beyond first order. We examine how the coupling constants depend on the coefficients of the beta-function beyond one loop order. A way of characterizing renormalization schemes that doesn't use coefficients of the beta-function is considered for models with either one or two couplings. The renormalization scheme ambiguities of physical quantities computed to finite order in perturbation theory are also examined. We demonstrate how summation of the logarithms that have explicit dependence on the renormalization scale parameter mu in a physical quantity R leads to a cancellation with the implicit dependence of R on mu through the running couplings. It is also shown that there exists a renormalization scheme in which all radiative effects beyond lowest order are incorporated into the behaviour of the running couplings.",1711.04758v4 2018-10-05,Revisiting Electroweak Phase Transition with Varying Yukawa Coupling Constants,"We revisited the scenario of electroweak baryogenesis in the presence of large Yukawa couplings, in which it was found previously that a strongly first order electroweak phase transition can occur with the Higgs mass at its observed value of 125 GeV. Given the sensitivity of the running of the Higgs quartic coupling on the Yukawa coupling constants, we find that the addition of order one Yukawa couplings beyond the top quark drastically lowers the scale at which the Higgs potential becomes unstable. Specifically, even with only one additional order one Yukawa coupling, the scalar potential becomes unstable already at the TeV scale, assuming the Standard Model values for the Higgs sector parameters at the electroweak scale. Furthermore, by assuming the Standard Model values for the Higgs sector parameters at the TeV scale, the quartic coupling constant is driven to be larger than its Standard Model value at the electroweak scale. This in turn predicts a much lighter Higgs mass than the measured value of 125 GeV. In this scenario, the strength of the electroweak phase transition is also significantly weakened.",1810.02522v1 2018-10-15,Ferromagnetic and Antiferromagnetic Coupling of Spin Molecular Interfaces with High Thermal Stability,"We report an advanced organic spin-interface architecture with magnetic remanence at room temperature, constituted by metal phthalocyanine molecules magnetically coupled with Co layer(s), mediated by graphene. Fe- and Cu-phthalocyanines assembled on graphene/Co have identical structural configurations, but FePc couples antiferromagnetically with Co up to room temperature, while CuPc couples ferromagnetically with weaker coupling and thermal stability, as deduced by element-selective X-ray magnetic circular dichroic signals. The robust antiferromagnetic coupling is stabilized by a superexchange interaction, driven by the out-of-plane molecular orbitals responsible of the magnetic ground state and electronically decoupled from the underlying metal via the graphene layer, as confirmed by ab initio theoretical predictions. These archetypal spin interfaces can be prototypes to demonstrate how antiferromagnetic and/or ferromagnetic coupling can be optimized by selecting the molecular orbital symmetry.",1810.06317v1 2018-10-31,Demonstration of resonant inelastic X-ray scattering as a probe of exciton-phonon coupling,"Resonant inelastic X-ray scattering (RIXS) is a promising technique for obtaining electron-phonon coupling constants. However, the ability to extract these coupling constants throughout the Brillouin zone for crystalline materials remains limited. To address this need, we developed a Green's function formalism to capture electron-phonon contributions to core-level spectroscopies without explicitly solving the full vibronic problem. Our approach is based on the cumulant expansion of the Green's function combined with many-body theory calculated vibrational coupling constants. The methodology is applied to X-ray photoemission spectroscopy, X-ray absorption spectroscopy (XAS), and RIXS. In the case of the XAS and RIXS, we use a 2-particle exciton Green's function, which accounts implicitly for particle-hole interference effects that have previously proved difficult. To demonstrate the methodology and gain a deeper understanding of the experimental technique, we apply our formalism to small molecules, for which unambiguous experimental data exist. This comparison reveals that the vibronic coupling constant probed by RIXS is in fact related to exciton-phonon coupling rather than electron-phonon coupling, challenging the conventional interpretation of the experiment.",1810.13405v1 2020-06-22,Partially Information Coupled Duo-Binary Turbo Codes,"Partially information coupled turbo codes (PIC-TCs) is a class of spatially coupled turbo codes that can approach the BEC capacity while keeping the encoding and decoding architectures of the underlying component codes unchanged. However, PIC-TCs have significant rate loss compared to its component rate-1/3 turbo code, and the rate loss increases with the coupling ratio. To absorb the rate loss, in this paper, we propose the partially information coupled duo-binary turbo codes (PIC-dTCs). Given a rate-1/3 turbo code as the benchmark, we construct a duo-binary turbo code by introducing one extra input to the benchmark code. Then, parts of the information sequence from the original input are coupled to the extra input of the succeeding code blocks. By looking into the graph model of PIC-dTC ensembles, we derive the exact density evolution equations of the PIC-dTC ensembles, and compute their belief propagation decoding thresholds on the binary erasure channel. Simulation results verify the correctness of our theoretical analysis, and also show significant error performance improvement over the uncoupled rate-1/3 turbo codes and existing designs of spatially coupled turbo codes.",2006.11998v1 2020-06-30,Disformal couplings in a $Λ$CDM background cosmology,"The coupled quintessence model with disformal couplings is treated here to mimic the $\Lambda$CDM background. Using this approach, the quintessence potential does not have to be specified. The model considers a generic fluid coupled to the quintessence, which is specified to be either dark matter or a relativistic fluid. The background consists of a cosmological constant and another uncoupled generic fluid, to cater for three studied scenarios. The cosmological dynamics is investigated for the coupled quintessence model, whose disformal couplings depend on the equation of state of both generic fluids. The scenario, whereby both generic fluids are dark matter, was further analyzed for an expansion history of the mimicking model. The analysis confirms that the mass scale of the quintessence influences the disformal characteristics of the dynamical system, which is portrayed by the evolution of an effective conformal coupling.",2006.16962v3 2020-09-21,Dynamics of a 2D lattice of van der Pol oscillators with nonlinear repulsive coupling,"We describe spatiotemporal patterns in a network of identical van der Pol oscillators coupled in a two-dimensional geometry. In this study, we show that the system under study demonstrates a plethora of different spatiotemporal structures including chimera states when the coupling parameters are varied. Spiral wave chimeras are formed in the network when the coupling strength is rather large and the coupling range is short enough. Another type of chimeras is a target wave chimera. It is shown that solitary states play a crucial role in forming an incoherence cluster of this chimera state. They can also spread within the coherence cluster. Furthermore, when the coupling range increases, the target wave chimera evolves to the regime of solitary states which are randomly distributed in space. Growing the coupling strength leads to the attraction of solitary states to a certain spatial region, while the synchronous regime is set in the other part of the system. This spatiotemporal pattern represents a solitary state chimera, which is firstly found in the system of continuous-time oscillators. We offer the explanation of these phenomena and describe the evolution of the regimes in detail.",2009.09584v1 2020-09-24,Evolution of Spin-Orbital Entanglement with Increasing Ising Spin-Orbit Coupling,"Several realistic spin-orbital models for transition metal oxides go beyond the classical expectations and could be understood only by employing the quantum entanglement. Experiments on these materials confirm that spin-orbital entanglement has measurable consequences. Here, we capture the essential features of spin-orbital entanglement in complex quantum matter utilizing 1D spin-orbital model which accommodates SU(2)xSU(2) symmetric Kugel-Khomskii superexchange as well as the Ising on-site spin-orbit coupling. Building on the results obtained for full and effective models in the regime of strong spin-orbit coupling, we address the question whether the entanglement found on superexchange bonds always increases when the Ising spin-orbit coupling is added. We show that (i) quantum entanglement is amplified by strong spin-orbit coupling and, surprisingly, (ii) almost classical disentangled states are possible. We complete the latter case by analyzing how the entanglement existing for intermediate values of spin-orbit coupling can disappear for higher values of this coupling.",2009.11773v1 2021-02-01,Strong coupling of Fe-Co alloy with ultralow damping to superconducting co-planar waveguide resonators,"We report on the strong coupling between a metallic ferromagnetic Fe75Co25 thin film patterned element and a range of superconducting Nb half-wavelength co-planar waveguide (CPW) resonators. By varying the volume of the ferromagnet we demonstrate that the coupling rate scales linearly with the square root of the number of spins and achieve a coupling rate over 700 MHz, approaching the ultrastrong coupling regime. Experiments varying the center conductor width while maintaining constant magnetic volume verify that decreasing the center conductor width increases coupling and cooperativity. Our results show that the frequency dependence of the coupling rate is linear with the fundamental and higher order odd harmonics of the CPW, but with differing efficiencies. The results show promise for scaling planar superconducting resonator/magnetic hybrid systems to smaller dimensions.",2102.01129v1 2013-06-10,A recipe for Hamiltonian of system-environment coupling applicable to ultrastrong light-matter interaction regime,"When the light interacts with matters in a lossy cavity, in the standard cavity quantum electrodynamics, the dissipation of cavity fields is characterized simply by the strengths of the two couplings: the light-matter interaction and the system-environment coupling through the cavity mirror. However, in the ultrastrong light-matter interaction regime, the dissipation depends also on whether the two couplings are mediated by the electric field or the magnetic one (capacitive or inductive in superconducting circuits). Even if we know correctly the microscopic mechanism (Lagrangian) of the system-environment coupling, the coupling Hamiltonian itself is in principle modified due to the ultrastrong interaction in the cavity. In this paper, we show a recipe for deriving a general expression of the Hamiltonian of the system-environment coupling, which is applicable even in the ultrastrong light-matter interaction regime in the good-cavity and independent-transition limit.",1306.2099v3 2015-07-07,Stable and transient multi-cluster oscillation death in nonlocally coupled networks,"In a network of nonlocally coupled Stuart-Landau oscillators with symmetry-breaking coupling, we study numerically, and explain analytically, a family of inhomogeneous steady states (oscillation death). They exhibit multi-cluster patterns, depending on the cluster distribution prescribed by the initial conditions. Besides stable oscillation death, we also find a regime of long transients asymptotically approaching synchronized oscillations. To explain these phenomena analytically in dependence on the coupling range and the coupling strength, we first use a mean-field approximation which works well for large coupling ranges but fails for coupling ranges which are small compared to the cluster size. Going beyond standard mean-field theory, we predict the boundaries of the different stability regimes as well as the transient times analytically in excellent agreement with numerical results.",1507.01918v2 2015-07-13,Radiative corrections to the Triple Higgs Coupling in the Inert Higgs Doublet Model,"We investigate the implication of the recent discovery of a Higgs-like particle in the first phase of the LHC Run 1 on the Inert Higgs Doublet Model (IHDM). The determination of the Higgs couplings to SM particles and its intrinsic properties will get improved during the new LHC Run 2 starting this year. The new LHC Run 2 would also shade some light on the triple Higgs coupling. Such measurement is very important in order to establish the details of the electroweak symmetry breaking mechanism. Given the importance of the Higgs couplings both at the LHC and $e^+e^-$ Linear Collider machines, accurate theoretical predictions are required. We study the radiative corrections to the triple Higgs coupling $hhh$ and to $hZZ$, $hWW$ couplings in the context of the IHDM. By combining several theoretical and experimental constraints on parameter space, we show that extra particles might modify the triple Higgs coupling near threshold regions. Finally, we discuss the effect of these corrections on the double Higgs production signal at the $e^+e^-$ LC and show that they can be rather important.",1507.03630v1 2015-07-30,Spectral effects of dispersive mode coupling in driven mesoscopic systems,"Nanomechanical and other mesoscopic vibrational systems typically have several nonlinearly coupled modes with different frequencies and with long lifetime. We consider the power spectrum of one of these modes. Thermal fluctuations of the modes nonlinearly coupled to it lead to fluctuations of the mode frequency and thus to the broadening of its spectrum. However, the coupling-induced broadening is partly masked by the spectral broadening due to the mode decay. We show that the mode coupling can be identified and characterized using the change of the spectrum by weak resonant driving. We develop a path-integral method of averaging over the non-Gaussian frequency fluctuations from nonresonant (dispersive) mode coupling. The shape of the driving-induced power spectrum depends on the interrelation between the coupling strength and the decay rates of the modes involved. The characteristic features of the spectrum are analyzed in the limiting cases. We also find the power spectrum of a driven mode where the mode has internal nonlinearity. Unexpectedly, the power spectra induced by the intra- and inter-mode nonlinearities are qualitatively different. The analytical results are in excellent agreement with the numerical simulations.",1507.08683v1 2015-12-07,The modified indeterminate couple stress model: Why Yang et al.'s arguments motivating a symmetric couple stress tensor contain a gap and why the couple stress tensor may be chosen symmetric nevertheless,"We show that the reasoning in favor of a symmetric couple stress tensor in Yang et al.'s introduction of the modified couple stress theory contains a gap, but we present a reasonable physical hypothesis, implying that the couple stress tensor is traceless and may be symmetric anyway. To this aim, the origin of couple stress is discussed on the basis of certain properties of the total stress itself. In contrast to classical continuum mechanics, the balance of linear momentum and the balance of angular momentum are formulated at an infinitesimal cube considering the total stress as linear and quadratic approximation of a spatial Taylor series expansion.",1512.02053v2 2016-09-07,The allostery landscape: quantifying thermodynamic couplings in biomolecular systems,"Allostery plays a fundament role in most biological processes. However, little theory is available to describe it outside of two-state models. Here we use a statistical mechanical approach to show that the allosteric coupling between two collective variables is not a single number, but instead a two-dimensional thermodynamic coupling function that is directly related to the mutual information from information theory and the copula density function from probability theory. On this basis, we demonstrate how to quantify the contribution of specific energy terms to this thermodynamic coupling function, enabling a decomposition that reveals the mechanism of allostery. We illustrate the thermodynamic coupling function and its use by showing how allosteric coupling in the alanine dipeptide molecule contributes to the overall shape of the {\Phi}/{\Psi} free energy surface, and by identifying the interactions that are necessary for this coupling.",1609.02059v1 2016-09-10,The polaron paradigm: a dual coupling effective band model,"Non-diagonal couplings to a bosonic bath completely change polaronic dynamics, from the usual diagonally-coupled paradigm of smoothly-varying properties. We study, using analytic and numerical methods, a model having both diagonal Holstein and non-diagonal Su-Schrieffer-Heeger (SSH) couplings. The critical coupling found previously in the pure SSH model, at which the $k=0$ effective mass diverges, now becomes a transition line in the coupling constant plane - the form of the line depends on the adiabaticity parameter. Detailed results are given for the quasiparticle and ground state properties, over a wide range of couplings and adiabaticity ratios. The new paradigm involves a destabilization, at the transition line, of the simple Holstein polaron to one with a finite ground-state momentum, but with everywhere a continuously evolving band shape. No 'self-trapping transition' exists in any of these models. The physics may be understood entirely in terms of competition between different hopping terms in a simple renormalized effective band theory. The possibility of further transitions is suggested by the results.",1609.03096v1 2016-09-11,Spin-Orbit Coupling Induced Spin Squeezing in Three-Component Bose Gases,"We observe spin squeezing in three-component Bose gases where all three hyperfine states are coupled by synthetic spin-orbit coupling. This phenomenon is a direct consequence of spin-orbit coupling, as can be seen clearly from an effective spin Hamiltonian. By solving this effective model analytically with the aid of a Holstein-Primakoff transformation for spin-1 system in the low excitation limit, we conclude that the spin-nematic squeezing, a novel category of spin squeezing existing exclusively in large spin systems, is enhanced with increasing spin-orbit intensity and effective Zeeman field, which correspond to Rabi frequency and two-photon detuning within the Raman scheme for synthetic spin-orbit coupling, respectively. These trends of dependence are in clear contrast to spin-orbit coupling induced spin squeezing in spin-1/2 systems. We also analyze the effects of harmonic trap and interaction with realistic experimental parameters numerically, and find that a strong harmonic trap favors spin-nematic squeezing. We further show spin-nematic squeezing can be interpreted as two-mode entanglement or two-spin squeezing at low excitation. Our findings can be observed in ^{87}Rb gases with existing techniques of synthetic spin-orbit coupling and spin-selectively imaging.",1609.03141v1 2016-09-14,Universal Distribution of Would-be Topological Zero Modes in Coupled Chiral Systems,"We consider two quenched, chiral ensembles which are coupled in such a way that a combined chiral symmetry is preserved. The coupling also links the topology of the two systems such that the number of exact zero modes in the coupled system equals the sum of the number of zero modes in the two uncoupled systems counted with sign. The canceled modes that turn non-topological due to the coupling become near-zero modes at small coupling. We analyze the distribution of these would-be zero modes using effective field theory. The distribution is universal and, in the limit of small coupling, the would-be zero modes are distributed according to a finite size chiral Gaussian ensemble, where the width of the distribution scales as the inverse square root of the volume.",1609.04252v2 2016-09-27,Novel phases in strongly coupled four-fermion theories,"We study a lattice model comprising four massless reduced staggered fermions in four dimensions coupled through an $SU(4)$-invariant four-fermion interaction. We present both theoretical arguments and numerical evidence that no bilinear fermion condensates are present for any value of the four-fermi coupling, in contrast to earlier studies of Higgs--Yukawa models with different exact lattice symmetries. At strong coupling we observe the formation of a four-fermion condensate and a mass gap in spite of the absence of bilinear condensates. Unlike those previously studied systems we do not find a ferromagnetic phase separating this strong-coupling phase from the massless weak-coupling phase. Instead we observe long-range correlations in a narrow region of the coupling, still with vanishing bilinear condensates. While our numerical results come from relatively small lattice volumes that call for caution in drawing conclusions, if this novel phase structure is verified by future investigations employing larger volumes it may offer the possibility for new continuum limits for strongly interacting fermions in four dimensions.",1609.08541v3 2016-09-30,Event-triggered stabilization of coupled dynamical systems with fast Markovian switching,"In this paper, stability of linearly coupled dynamical systems with feedback pinning is studied. Event-triggered rules are employed on both diffusion coupling and feedback pinning to reduce the updating load of the coupled system. Here, both the coupling matrix and the set of pinned-nodes vary with time are induced by a homogeneous Markov chain. For each node, the diffusion coupling and feedback pinning are set up from the observation of its neighbors' and target's (if pinned) information at the latest event time and the next event time is triggered by some specified criteria. Two event-triggering rules are proposed and it is proved that if the system with time-average coupling and pinning gains are stable, the event-triggered strategies can stabilize the system if the switching is sufficiently fast. Moreover, Zeno behaviors are excluded in some cases. Finally, numerical examples are presented to illustrate the theoretical results.",1609.09605v1 2016-10-31,Photon echo in exciton-plasmon nanomaterials: a time-dependent signature of strong coupling,"We investigate the dynamics of photon echo exhibited by exciton-plasmon systems under strong coupling conditions. Using a self-consistent model based on coupled Maxwell-Bloch equations we investigate femtosecond time dynamics of ensembles of interacting molecules optically coupled to surface plasmon supporting materials. It is shown that observed photon echoes under two pulse pump-probe sequence are highly dependent on various material parameters such as molecular concentration and periodicity. Simulations of photon echoes in exciton-plasmon materials reveal a unique signature of the strong exciton-plasmon coupling, namely a double-peak structure in spectra of recorded echo signals. This phenomenon is shown to be related to hybrid states (upper and lower polaritons) in exciton-plasmon systems under strong coupling conditions. It is also demonstrated that the double-peak echo is highly sensitive to mild deviations of the coupling from resonant conditions making it a great tool for ultrafast probes.",1611.00053v2 2016-11-14,Generalized Analytical Solutions and Synchronization Dynamics of Coupled Simple Nonlinear Electronic Circuits,"In this paper we present a generalized analytical solution to the generalized state equations of coupled second-order non-autonomous circuit systems. The analytical solutions thus obtained are used to study the synchronization dynamics of two different types of circuit systems, differing only by their constituting nonlinear element. The synchronization dynamics of the coupled systems are studied through two-parameter bifurcation diagrams, phase portraits and time-series plots obtained from the explicit analytical solutions. The mechanism of synchronization is realized through the bifurcation of the eigenvalues as functions of the control parameter in each of the coupled piecewise linear regions of the drive and response systems. The stability of the synchronized state for coupled identical chaotic states are studeid through the {\emph{master stability function}}. Further, {\emph{conditional Lyapunov exponents}} and {\emph{Kaplan-Yorke dimension}} are obtained to confirm the synchronized states of both coupled identical and non-identical chaotic states. The synchronization dynamics of coupled chaotic systems studied through two-parameter bifurcation diagrams obtained from explicit analytical solutions is reported in the literature for the first time.",1611.04289v1 2016-11-15,Constraints on generalized non-standard $tbW$ couplings,"General non-standard $tbW$ couplings are studied as model independently as possible based on the effective Lagrangian consisting of the dimension-6 operators, which is an extension of the standard-model Lagrangian. The $tbW$-interaction Lagrangian in this framework includes four kinds of couplings, which could be complex. Constraints on those non-standard $tbW$ couplings are obtained by comparing the experimental data related to the $t\to b W$ process with the corresponding theoretical formulas derived from the effective Lagrangian. The constraints on some sets of the non-standard couplings are shown not to be so strong because those couplings balance out each other as we treat all the non-standard couplings as complex numbers at the same time.",1611.04679v1 2016-11-16,Ferromagnetic order induced on graphene by Ni/Co proximity effects,"We build a tight-binding Hamiltonian describing Co/Ni over graphene, contemplating ATOP (a Co/Ni atom on top of each Carbon atom of one graphene sublattice) and HCP (one Co/Ni atom per Graphene plaquette) configurations. For the ATOP configuration the orbitals involved, for the Co/Ni, are the $d_{z^2-r^2}$ which most strongly couple to one graphene sublattice and the $d_{xz}$, $d_{yz}$ orbitals that couple directly to the second sublattice site. Such configuration is diagonal in pseudo-spin and spin space, yielding electron doping of the graphene and antiferro-magnetic ordering in the primitive cell in agreement with DFT calculations. The second, HCP configuration is symmetric in the graphene sublattices and only involves coupling to the $d_{xz}$, $d_{yz}$ orbitals. The register of the lattices in this case allows for a new coupling between nearest neighbour sites, generating non-diagonal terms in the pseudo-spin space and novel spin-kinetic couplings mimicking a spin-orbit coupling generated by a magnetic coupling. The resulting proximity effect in this case yields ferromagnetic order in the graphene substrate. We derive the band structure in the vicinity of the K points for both configurations, the Bloch wavefunctions and their spin polarization.",1611.05464v1 2016-11-30,Integrating out resonances in strongly-coupled electroweak scenarios,"Accepting that there is a mass gap above the electroweak scale, the Electroweak Effective Theory (EWET) is an appropriate tool to describe this situation. Since the EWET couplings contain information on the unknown high-energy dynamics, we consider a generic strongly-coupled scenario of electroweak symmetry breaking, where the known particle fields are coupled to heavier states. Then, and by integrating out these heavy fields, we study the tracks of the lightest resonances into the couplings. The determination of the low-energy couplings (LECs) in terms of resonance parameters can be made more precise by considering a proper short-distance behaviour on the Lagrangian with heavy states, since the number of resonance couplings is then reduced. Notice that we adopt a generic non-linear realization of the electroweak symmetry breaking with a singlet Higgs.",1611.10295v1 2017-04-02,A quasinonlocal coupling method for nonlocal and local diffusion models,"In this paper, we extend the idea of ""geometric reconstruction"" to couple a nonlocal diffusion model directly with the classical local diffusion in one dimensional space. This new coupling framework removes interfacial inconsistency, ensures the flux balance, and satisfies energy conservation as well as the maximum principle, whereas none of existing coupling methods for nonlocal-to-local coupling satisfies all of these properties. We establish the well-posedness and provide the stability analysis of the coupling method. We investigate the difference to the local limiting problem in terms of the nonlocal interaction range. Furthermore, we propose a first order finite difference numerical discretization and perform several numerical tests to confirm the theoretical findings. In particular, we show that the resulting numerical result is free of artifacts near the boundary of the domain where a classical local boundary condition is used, together with a coupled fully nonlocal model in the interior of the domain.",1704.00348v2 2018-01-16,Harmonically trapped attractive and repulsive spin-orbit and Rabi coupled Bose-Einstein condensates,"Numerically we investigate the ground state of effective one-dimensional spin-orbit (SO) and Rabi coupled two pseudo-spinor Bose-Einstein condensates (BECs) under the effect of harmonic traps. For both signs of the interaction, density profiles of SO and Rabi coupled BECs in harmonic potentials, which simulate a real experimental situation are obtained. The harmonic trap causes a strong reduction of the multi-peak nature of the condensate and it increases its density. For repulsive interactions, the increase of SO coupling results in an uncompressed less dense condensate and with increased multi-peak nature of the density. The increase of Rabi coupling leads to a density increase with an almost constant number of multi-peaks. For both signs of the interaction and negative values of Rabi coupling, the condensate develops a notch in the central point and it seems to a dark-in-bright soliton. In the case of the attractive nonlinearity, an interesting result is the increase of the collapse threshold under the action of the SO and Rabi couplings.",1801.05321v1 2018-01-26,Strong indirect coupling between graphene-based mechanical resonators via a phonon cavity,"Mechanical resonators are promising systems for storing and manipulating information. To transfer information between mechanical modes, either direct coupling or an interface between these modes is needed. In previous works, strong coupling between different modes in a single mechanical resonator and direct interaction between neighboring mechanical resonators have been demonstrated. However, coupling between distant mechanical resonators, which is a crucial request for long-distance classical and quantum information processing using mechanical devices, remains an experimental challenge. Here, we report the experimental observation of strong indirect coupling between separated mechanical resonators in a graphene-based electromechanical system. The coupling is mediated by a far-off-resonant phonon cavity through virtual excitations via a Raman-like process. By controlling the resonant frequency of the phonon cavity, the indirect coupling can be tuned in a wide range. Our results may lead to the development of gate-controlled all-mechanical devices and open up the possibility of long-distance quantum mechanical experiments.",1801.08752v1 2018-08-13,Strong coupling of a single ion to an optical cavity,"Strong coupling between an atom and an electromagnetic resonator is an important condition in cavity quantum electrodynamics (QED). While strong coupling in various physical systems has been achieved so far, it remained elusive for single atomic ions. In this paper we demonstrate for the first time the coupling of a single ion to an optical cavity with a coupling strength exceeding both atomic and cavity decay rates. We use cavity assisted Raman spectroscopy to precisely characterize the ion-cavity coupling strength and observe a spectrum featuring the normal mode splitting in the cavity transmission due to the ion-cavity interaction. Our work paves the way towards new applications of cavity QED utilizing single trapped ions in the strong coupling regime for quantum optics and quantum technologies.",1808.04031v1 2018-08-30,Revisiting Supernova 1987A Limits on Axion-Like-Particles,"Using recent supernova models, I revisit the Supernova 1987a constraints on scalar/pseudoscalar Axion-Like-Particles (ALPs). On the basis of the neutrino detections, the luminosity of ALPs must be $\lesssim 5\times10^{52} \,\mathrm{erg}/s$ after the core-bounce, and this bound limits ALPs couplings. Contrary to the QCD axion models where all couplings are $\sim 1/f_a$, it has been shown recently that a radion/dilaton could have far different coupling strength to photons and to nucleons. This fact has raised a need to establish the limits on each coupling independently. The bounds from ALPs emission by nucleon-nucleon bremsstrahlung through a two-nucleon coupling and by the Primakoff process through a two-photon coupling are updated considering the total volume emission. I find the bounds on the two-photon coupling from the Primakoff process differ from previous bounds by an order of magnitude. Through the volume emission study, trapping regimes for $m_a\gtrsim10\,\mathrm{MeV}$ are also alleviated, which need to be probed by future experiments.",1808.10136v1 2019-06-03,Non-Hermitian phase transition and eigenstate localization induced by asymmetric coupling,"We investigate a uniformly coupled non-Hermitian system with asymmetric coupling amplitude. The asymmetric coupling equals to a symmetric coupling threaded by an imaginary gauge field. In a closed configuration, the imaginary gauge field leads to an imaginary magnetic flux, which induces a non-Hermitian phase transition. For an open boundary, the imaginary gauge field results in an eigenstate localization. The eigenstates under Dirac and biorthogonal norms and the scaling laws are quantitatively investigated to show the affect of asymmetric coupling induced one-way amplification. However, the imaginary magnetic flux does not inevitably induce the non-Hermitian phase transition for systems without translation invariance, this is elucidated from the non-Hermitian phase transition in the non-Hermitian ring with a single coupling defect. Our findings provide insights into the non-Hermitian phase transition and one-way localization.",1906.00610v1 2019-06-24,Universal mechanism of low-frequency brain rhythm formation through nonlinear coupling of high-frequency spiking-like activity,"A universal mechanism of emergence of synchronized low frequency brain wave field activity is presented as a result of nonlinear coupling with flat frequency neuronal forcing. The mechanism utilizes a unique dispersion properties of weakly-evanescent wave--like brain surface modes that are predicted to exist within a inhomogeneous and anisotropic physical brain tissue model. These surface modes are able to propagate in thin inhomogeneous layers with frequencies that are inverse proportional to wave numbers. The resonant and non-resonant terms of nonlinear coupling between multiple modes produce both synchronous spiking-like high frequency wave activity as well as low frequency wave rhythms. The relatively narrow localized frequency response of the non-resonant coupling can be expressed by terms similar to phase coupling in oscillatory systems. Numerical simulation of forced multiple mode dynamics shows as forcing increases a transition from damped to oscillatory regime that is then silenced off as over excitation is reached. The resonant nonlinear coupling results in emergence of low frequency rhythms with frequencies that are several orders of magnitude below the linear frequencies of modes taking part in the coupling.",1906.09716v1 2019-07-25,Squeezing enhanced atom-cavity interaction in coupled cavities with high dissipation rates,"The realization of the strong coupling regime is requisite for implementing quantum information tasks. Here, a method for enhancing the atom-field coupling in highly dissipative coupled cavities is proposed. By introducing parametric squeezing into the primary cavity which is only virtually excited under specific parametric conditions, coupling enhancement between atom and auxiliary cavity is realized for proper squeezing parameters. This enables the system to be robust against large cavity decay and atomic spontaneous emission. The observation of vacuum Rabi oscillations show that the originally weak-coupled system can be enhanced into effective strong coupling regime.",1907.10849v1 2019-10-10,Probing light Yukawa couplings in Higgs pair production,"One of the puzzles of the SM is the large hierarchy between the Yukawa couplings of different flavours. Yukawa couplings of the first and the second generation are constrained only very weakly so far. However, one can obtain large deviations in the Yukawa couplings in several New Physics (NP) models, such as e.g. models with new vector-like quarks, or new Higgs bosons that couple naturally to individual fermion families. In this work, we investigate the potential bounds on the NP Higgs Yukawa couplings modification $ \kappa_f$ for light quarks from double-Higgs at the LHC, starting from a model independent formalism. We have looked at the two Higgs boson final state $ b \bar b \gamma \gamma $, and the relevant experimental cuts to reduce backgrounds and estimated the potential exclusion bounds for $ \kappa_f$. We have considered both linear and non-linear effective field theory for the Higgs light quark coupling modifications.",1910.04546v1 2019-10-14,Synchronization in networks of coupled hyperchaotic CO$_2$ lasers,"A non-autonomous dynamical system is proposed to study the synchronization in networks of mutually coupled optically modulated hyperchaotic CO$_2$ lasers. By the method of master stability function (MSF) it is shown that the stable synchronous state can be reached for both the ring of diffusively coupled (RDC) and star-coupled (SC) networks of at most $24$ nodes or oscillators. A numerical simulation of the coupled $24$ hyperchaotic CO$_2$ lasers is also performed to show that the corresponding synchronization error $\lesssim10^{-6}$. Furthermore, the chimera states of the networks are found to coexist in some intervals of time and the coupling strengths where the networks are not synchronized, implying that the synchronization occurs only in some specific ranges of values of the coupling strengths.",1910.06852v2 2020-01-03,Dissipative couplings in cavity magnonics,"Cavity Magnonics is an emerging field that studies the strong coupling between cavity photons and collective spin excitations such as magnons. This rapidly developing field connects some of the most exciting branches of modern physics, such as quantum information and quantum optics, with one of the oldest science on the earth, the magnetism. The past few years have seen a steady stream of exciting experiments that demonstrate novel magnon-based transducers and memories. Most of such cavity magnonic devices rely on coherent coupling that stems from direct dipole-dipole interaction. Recently, a distinct dissipative magnon-photon coupling was discovered. In contrast to coherent coupling that leads to level repulsion between hybridized modes, dissipative coupling results in level attraction. It opens an avenue for engineering and harnessing losses in hybrid systems. This article gives a brief review of this new frontier. Experimental observations of level attraction are reviewed. Different microscopic mechanisms are compared. Based on such experimental and theoretical reviews, we present an outlook for developing open cavity systems by engineering and harnessing dissipative couplings.",2001.00978v2 2020-01-09,A Unified Framework for Coupled Tensor Completion,"Coupled tensor decomposition reveals the joint data structure by incorporating priori knowledge that come from the latent coupled factors. The tensor ring (TR) decomposition is invariant under the permutation of tensors with different mode properties, which ensures the uniformity of decomposed factors and mode attributes. The TR has powerful expression ability and achieves success in some multi-dimensional data processing applications. To let coupled tensors help each other for missing component estimation, in this paper we utilize TR for coupled completion by sharing parts of the latent factors. The optimization model for coupled TR completion is developed with a novel Frobenius norm. It is solved by the block coordinate descent algorithm which efficiently solves a series of quadratic problems resulted from sampling pattern. The excess risk bound for this optimization model shows the theoretical performance enhancement in comparison with other coupled nuclear norm based methods. The proposed method is validated on numerical experiments on synthetic data, and experimental results on real-world data demonstrate its superiority over the state-of-the-art methods in terms of recovery accuracy.",2001.02810v4 2020-01-16,Single-photon transport in one-dimensional coupled-resonator waveguide with second order nonlinearity coupling to a nanocavity containing a two-level atom and Kerr nonlinearity,"We study controllable single photon scattering in a one-dimensional waveguide coupling with an additional cavity by second order nonlinear materials in a non-cascading configuration, where the additional cavity is embedded with two-level atom and filled with Kerr-nonlinear materials. Considering the second order nonlinear coupling, we analyze the transmission properties of the three different coupling forms as follows: (i) The two-level atom is excited without the Kerr-nonlinearity. (ii)The Kerr-nonlinearity is excited without the two-level atom. (iii) Both of the two-level atom and Kerr-nonlinearity are excited. The transmission and reflection amplitudes are obtained by the discrete coordinates approach for the three cases. The results showed that the transmission properties can be adjusted by the above three different coupling forms, which indicate our scheme can be used as a single photon switch to control the transmission and reflection of the single photon in the one-dimensional coupled resonant waveguide. We compared the results with [Phys. Rev. A 85, 053840(2012)] and find the advantages.",2001.05827v1 2020-01-30,Avoidance couplings on non-complete graphs,"A coupling of random walkers on the same finite graph, who take turns sequentially, is said to be an avoidance coupling if the walkers never collide. Previous studies of these processes have focused almost exclusively on complete graphs, in particular how many walkers an avoidance coupling can include. For other graphs, apart from special cases, it has been unsettled whether even two non-colliding simple random walkers can be coupled. In this article, we construct such a coupling on (i) any $d$-regular graph avoiding a fixed subgraph depending on $d$; and (ii) any square-free graph with minimum degree at least three. A corollary of the first result is that a uniformly random regular graph on $n$ vertices admits an avoidance coupling with high probability.",2001.11524v2 2020-02-02,Virtual Critical Coupling,"Electromagnetic resonators are a versatile platform to harvest, filter and trap electromagnetic energy, at the basis of many applications from microwaves to optics. Resonators with a large intrinsic quality factor (Q) are highly desirable since they can store a large amount of energy, leading to sharp filtering and low loss. Exciting high-Q cavities with monochromatic signals, however, suffers from poor excitation efficiency, i.e., most of the impinging energy is lost in the form of reflection, since high-Q resonators are weakly coupled to external radiation. Although critical coupling eliminates reflections in steady-state by matching the intrinsic and coupling decay rates, this approach requires the introduction of loss in the resonator, causing dissipation and lowering the overall Q-factor. Here, we extend the notion of critical coupling to high-Q lossless resonators based on tailoring the temporal profile of the excitation wave. Utilizing coupled-mode theory, we demonstrate an effect analogous to critical coupling by mimicking loss with non-monochromatic excitations at complex frequencies. Remarkably, we show that this approach enables unitary excitation efficiency in open systems, even in the limit of extreme quality factors in the regime of quasi-bound states in the continuum.",2002.00487v1 2020-02-24,Exceptional coupling in extreme skin-depth waveguides for extremely low waveguide crosstalk,"Photonic chips can miniaturize complicate optical systems very tiny and portable, providing versatile functionalities for many optical applications. Increasing the photonic chip integration density is highly desired as it provides more functionalities, low cost, and lower power consumption. However, photonic chip integration density is limited by the waveguide crosstalk, which is caused by the evanescent waves in the cladding. Here we show that the waveguide crosstalk can be suppressed completely with the exceptional coupling in extreme skin-depth (eskid) waveguides. The anisotropic dielectric perturbations in the coupled eskid waveguides cause such an exceptional coupling, resulting in infinitely long coupling length. We demonstrate the extreme suppression of waveguide crosstalk via exceptional coupling on a silicon-on-insulator (SOI) platform, which is compatible with a complementary metal-oxide-semiconductor (CMOS) process. The idea of exceptional coupling in eskid waveguides can be applied to many other photonic devices as well, significantly reducing entire chip footprints.",2002.10579v1 2020-03-02,Split-Gate Cavity Coupler for Silicon Circuit Quantum Electrodynamics,"Coherent charge-photon and spin-photon coupling has recently been achieved in silicon double quantum dots (DQD). Here we demonstrate a versatile split-gate cavity-coupler that allows more than one DQD to be coupled to the same microwave cavity. Measurements of the cavity transmission as a function of level detuning yield a charge cavity coupling rate $g_c/2\pi$ = 58 MHz, charge decoherence rate $\gamma_c/2\pi$ = 36 MHz, and cavity decay rate $\kappa/2\pi$ = 1.2 MHz. The charge cavity coupling rate is in good agreement with device simulations. Our coupling technique can be extended to enable simultaneous coupling of multiple DQDs to the same cavity mode, opening the door to long-range coupling of semiconductor qubits using microwave frequency photons.",2003.01088v1 2020-04-09,Coupling between waveguides and microresonators: the local approach,"Coupling between optical microresonators and waveguides is a critical characteristic of resonant photonic devices with complex behavior that is not well understood. When the characteristic variation length of the microresonator modes is much larger than the waveguide width, local coupling parameters emerge that are independent of the resonator mode distributions and offer a simplified description of coupling behavior. We develop a robust numerical-fitting-based methodology for experimental determination of the local coupling parameters in all coupling regimes and demonstrate their characterization along a microfiber waveguide coupled to an elongated bottle microresonator.",2004.04661v3 2020-04-13,Moment map for coupled equations of Kähler forms and curvature,"In this paper we introduce two new systems of equations in K\""ahler geometry: The coupled p equation and the generalized coupled cscK equation. We motivate the equations from the moment map pictures, prove the uniqueness of solutions and find out the obstructions to the solutions for the second equation. We also point out the connections between the coupled cscK equation, the coupled K\""{a}hler Yang-Mills equations and the deformed Hermitian Yang-Mills equation. Moreover, using this moment map, we can show the Mabuchi functional for the generalized coupled cscK equation, and a special case of the coupled K\""ahler Yang-Mills equations and the deformed Hermitian Yang-Mills equation are convex along the smooth geodesic, which is different from the one using the moment map picture from the gauge group. In our case, the geodesic is given by the natural metric on the product of smooth K\""{a}hler potential $\mathcal{K}(X,\omega_0)\times \cdots \times \mathcal{K}(X,\omega_k)$.",2004.06023v6 2020-04-16,Matter coupling in Minimal Massive 3D Gravity and spinor-matter interactions in exterior algebra formalism,"In this work, by employing the exterior algebra formalism, we study the matter coupling in Minimal Massive 3D Gravity (MMG) by first considering that the matter Lagrangian is connection-independent and then considering that the matter coupling is connection-dependent. The matter coupling in MMG has been previously investigated in the work Arvanitakis {\it et al} (2014 {\it Class. Quantum Grav.} {\bf 31} 235012) in tensorial notation where the matter Lagrangian is considered to be connection-independent. In the first part of the present paper, we revisit the connection-independent matter coupling by using the language of differential forms. We derive the MMG field equation and construct the related source 2-form. We also obtain the consistency relation within this formalism. Next, we examine the case where the matter Lagrangian is connection-dependent. In particular, we concentrate on the spinor-matter coupling and obtain the MMG field equation by explicitly constructing the source term. We also get the consistency relation that the source term should satisfy in order that spinor-matter coupled MMG equation be consistent.",2004.07476v3 2020-04-18,Switchable next-nearest-neighbor coupling for controlled two-qubit operations,"In a superconducting quantum processor with nearest neighbor coupling, the dispersive interaction between adjacent qubits can result in an effective next-nearest-neighbor coupling whose strength depends on the state of the intermediary qubit. Here, we theoretically explore the possibility of engineering this next-nearest-neighbor coupling to implement controlled two-qubit operations where the intermediary qubit controls the operation on the next-nearest neighbor pair of qubits. In particular, in a system comprising two types of superconducting qubits with anharmonicities of opposite-sign arranged in an -A-B-A- pattern, where the unwanted static ZZ coupling between adjacent qubits could be heavily suppressed, a switchable coupling between the next-nearest-neighbor qubits can be achieved via the intermediary qubit, the qubit state of which functions as an on/off switch for this coupling. Therefore, depending on the adopted activating scheme, various controlled two-qubit operations such as controlled-iSWAP gate can be realized, potentially enabling circuit depth reductions as to a standard decomposition approach for implementing generic quantum algorithms.",2004.08639v2 2020-04-28,A new signature for strong light-matter coupling using spectroscopic ellipsometry,"Light-matter interactions can occur when an ensemble of molecular resonators is placed in a confined electromagnetic field. In the strong coupling regime the rapid exchange of energy between the molecules and the electromagnetic field results in the emergence of hybrid light-matter states called polaritons. Multiple criteria exist to define the strong coupling regime, usually by comparing the splitting of the polariton bands with the linewidths of the uncoupled modes. Here we highlight the limitations of these criteria and study strong coupling using spectroscopic ellipsometry, a commonly used optical characterisation technique. We identify a new signature of strong coupling in ellipsometric phase spectra. Combining ellipsometric amplitude and phase spectra yields a distinct topological feature that we suggest could serve as a new criterion for strong coupling. Our results introduce the idea of ellipsometric topology and could provide further insight into the transition from the weak to strong coupling regime.",2004.13434v2 2020-04-29,Light-mediated strong coupling between a mechanical oscillator and atomic spins one meter apart,"Engineering strong interactions between quantum systems is essential for many phenomena of quantum physics and technology. Typically, strong coupling relies on short-range forces or on placing the systems in high-quality electromagnetic resonators, restricting the range of the coupling to small distances. We use a free-space laser beam to strongly couple a collective atomic spin and a micromechanical membrane over a distance of one meter in a room-temperature environment. The coupling is highly tunable and allows the observation of normal-mode splitting, coherent energy exchange oscillations, two-mode thermal noise squeezing and dissipative coupling. Our approach to engineer coherent long-distance interactions with light makes it possible to couple very different systems in a modular way, opening up a range of opportunities for quantum control and coherent feedback networks.",2004.14424v1 2020-04-30,Potential-driven Inflation with Disformal Coupling to Gravity,"In this paper, we investigate the potential-driven inflation models with a disformal coupling to Einstein Gravity, to find out the effects of such a coupling on these models. We consider a simple coupling form which introduces only one parameter, and three inflation models, namely the chaotic inflation, the Higgs inflation, and the monodromy inflation. We find that the disformal coupling can have some modifications to the observational variables of these models such as the power spectrum, the spectral index as well as the tensor/scalar ratio, although not too large due to the constraints on the disformal coupling parameter. With these modifications, one has the opportunity of improving models that lie on the edge of the favorable regions of Planck observational data, such as monodromy inflation. Moreover, the non-trivial sound speed of tensor perturbations (gravitational waves) may come out, due to the coupling of gravity and kinetic terms of the field.",2004.14712v1 2020-05-11,Tunable coupling of two mechanical resonators by a graphene membrane,"Coupled nanomechanical resonators are interesting for both fundamental studies and practical applications as they offer rich and tunable oscillation dynamics. At present, the mechanical coupling in such systems is often mediated by a fixed geometry, such as a joint clamping point of the resonators or a displacement-dependent force. Here we show a graphene-integrated electromechanical system consisting of two physically separated mechanical resonators -- a comb-drive actuator and a suspended silicon beam -- that are tunably coupled by a graphene membrane. The graphene membrane, moreover, provides a sensitive electrical read-out for the two resonating systems silicon structures showing 16 different modes in the frequency range from 0.4~to 24~MHz. In addition, by pulling on the graphene membrane with an electrostatic potential applied to one of the silicon resonators, we control the mechanical coupling, quantified by the $g$-factor, from 20 kHz to 100 kHz. Our results pave the way for coupled nanoelectromechanical systems requiring controllable mechanically coupled resonators.",2005.05358v2 2020-05-13,Turing's Children: Representation of Sexual Minorities in STEM,"We provide the first nationally representative estimates of sexual minority representation in STEM fields by studying 142,641 men and women in same-sex couples from the 2009-2018 American Community Surveys. These data indicate that men in same-sex couples are 12 percentage points less likely to have completed a bachelor's degree in a STEM field compared to men in different-sex couples; there is no gap observed for women in same-sex couples compared to women in different-sex couples. The STEM gap between men in same-sex and different-sex couples is larger than the STEM gap between white and black men but is smaller than the gender STEM gap. We also document a gap in STEM occupations between men in same-sex and different-sex couples, and we replicate this finding using independently drawn data from the 2013-2018 National Health Interview Surveys. These differences persist after controlling for demographic characteristics, location, and fertility. Our findings further the call for interventions designed at increasing representation of sexual minorities in STEM.",2005.06664v1 2020-05-18,Pseudospin-electric coupling for holes beyond the envelope-function approximation,"In the envelope-function approximation, interband transitions produced by electric fields are neglected. However, electric fields may lead to a spatially local ($k$-independent) coupling of band (internal, pseudospin) degrees of freedom. Such a coupling exists between heavy-hole and light-hole (pseudo-)spin states for holes in III-V semiconductors, such as GaAs, or in group IV semiconductors (germanium, silicon, ...) with broken inversion symmetry. Here, we calculate the electric-dipole (pseudospin-electric) coupling for holes in GaAs from first principles. We find a transition dipole of $0.5$ debye, a significant fraction of that for the hydrogen-atom $1s\to2p$ transition. In addition, we derive the Dresselhaus spin-orbit coupling that is generated by this transition dipole for heavy holes in a triangular quantum well. A quantitative microscopic description of this pseudospin-electric coupling may be important for understanding the origin of spin splitting in quantum wells, spin coherence/relaxation ($T_2^*/T_1$) times, spin-electric coupling for cavity-QED, electric-dipole spin resonance, and spin non-conserving tunneling in double quantum dot systems.",2005.08821v2 2020-05-20,Strong Optomechanical Coupling at Room Temperature by Coherent Scattering,"Quantum control of a system requires the manipulation of quantum states faster than any decoherence rate. For mesoscopic systems, this has so far only been reached by few cryogenic systems. An important milestone towards quantum control is the so-called strong coupling regime, which in cavity optomechanics corresponds to an optomechanical coupling strength larger than cavity decay rate and mechanical damping. Here, we demonstrate the strong coupling regime at room temperature between a levitated silica particle and a high finesse optical cavity. Normal mode splitting is achieved by employing coherent scattering, instead of directly driving the cavity. The coupling strength achieved here approaches three times the cavity linewidth, crossing deep into the strong coupling regime. Entering the strong coupling regime is an essential step towards quantum control with mesoscopic objects at room temperature.",2005.10201v2 2020-07-03,Rigorous Quantum Formulation of Parity-Time Symmetric Coupled Resonators,"Rigorous quantum formulation of the Parity-Time (PT) symmetry phenomenon in the RF/microwave regime for a coupled coil resonators with lump elements has been presented. The coil resonator is described by the lump-element model that consists of an inductor (L), a resistor (R) and a capacitor (C). Rigorous quantum Hamiltonian for the coupled LRC coil resonators system has been derived through twice basis transforms of the original basis. The first basis transform rotates the original basis such that off-diagonal terms of the governing matrix of the equation system of the coupled coil resonators reduces to constants. Then a second basis transform obtains the quantum Hamiltonian, including the diagonal effective complex frequencies and the off-diagonal coupling terms, together with the transformed basis. With the obtain quantum Hamiltonian, the eigenvalues and eigenvectors of the coupled coil resonators can be obtained as usual as the quantum Hamiltonian. Finally, numerical simulation verifies the correctness of the theory. The quantum formulation of the coupled coil resonators can provide better guideline to design a better PT-symmetric system.",2007.01462v1 2020-07-10,Role of solitary states in forming spatiotemporal patterns in a 2D lattice of van der Pol oscillators,"The behavior of the ensemble of coupled van der Pol oscillators is abundant when coupling parameters are changed. Incoherent and chimera-like regimes are observed at small values of the coupling strength parameter. Synchronization takes place with an increase in the coupling strength and coupling range parameters. Various chimera and solitary states are realised when the coupling strength parameter is sufficiently large. The single van der Pol oscillator is taken in the regime of relaxation oscillations. Therefore, the lattice may realise spiral wave and spiral wave chimera regimes. Besides, target wave and solitary state regimes are observed in the ensemble. Finally, the solitary state and solitary state chimera regimes are firstly shown for the lattice of coupled van der Pol oscillators.",2007.05174v1 2020-08-10,Solution to the Sudakov suppressed Balitsky-Kovchegov equation and its application to the HERA data,"We analytically solve the Sudakov suppressed Balitsky-Kovchegov evolution equation with the fixed and running coupling constants in the saturation region. The analytic solution of the $S$-matrix shows the $\exp(\mathcal{O}(\eta^2))$ rapidity dependence of the solution with the fixed coupling constant is replaced by $\exp(\mathcal{O}(\eta^{3/2}))$ dependence in the smallest dipole running coupling case rather than obeying the law found in our previous publication, in which all the solutions of the next-to-leading order evolution equations comply with $\exp(\mathcal{O}(\eta))$ rapidity dependence once the QCD coupling is switched from the fixed coupling to the smallest dipole running coupling prescription. This finding indicates that the corrections of the sub-leading double logarithms in the Sudakov suppressed evolution equation are significant, which compensate part of the evolution decrease of the dipole amplitude made by running coupling effect. To test the analytic findings, we calculate the numerical solutions of the Sudakov suppressed evolution equation, the numerical results confirm the analytic outcomes. Moreover, we use the numerical solutions of the evolution equation to fit the HERA data. It shows that the Sudakove suppressed evolution equation can give good quality fit to the data.",2008.04235v1 2020-10-20,Engineering Purely Nonlinear Coupling with the Quarton,"Strong nonlinear coupling of superconducting qubits and/or photons is a critical building block for quantum information processing. Due to the perturbative nature of the Josephson nonlinearity, linear coupling is often used in the dispersive regime to approximate nonlinear coupling. However, this dispersive coupling is weak and the underlying linear coupling mixes the local modes which, for example, distributes unwanted self-Kerr to photon modes. Here, we use the quarton to yield purely nonlinear coupling between two linearly decoupled transmon qubits. The quarton's zero $\phi^2$ potential enables a giant gigahertz-level cross-Kerr which is an order of magnitude stronger compared to existing schemes, and the quarton's positive $\phi^4$ potential can cancel the negative self-Kerr of qubits to linearize them into resonators. This giant cross-Kerr between bare modes of qubit-qubit, qubit-photon, and even photon-photon is ideal for applications such as single microwave photon detection and implementation of bosonic codes.",2010.09959v2 2020-11-05,Effective action of type II superstring theories at order $α'^3$: NS-NS couplings,"Recently, it has been shown that the minimum number of gauge invariant couplings for $B$-field, metric and dilaton at order $\alpha'^3$ is 872. These couplings, in a particular scheme, appear in 55 different structures. In this paper, up to an overall factor, we fix all parameters in type II supertirng theories by requiring the reduction of the couplings on a circle to be invariant under T-duality transformations. We find that there are 445 non-zero couplings which appear in 15 different structures. The couplings are fully consistent with the partial couplings that have been found in the literature by the four-point S-matrix element and by the non-linear Sigma model methods.",2011.02753v2 2020-11-19,Fast Cooling of Trapped Ion in Strong Sideband Coupling Regime,"Trapped ion in the Lamb-Dicke regime with the Lamb-Dicke parameter $\eta\ll1$ can be cooled down to its motional ground state using sideband cooling. Standard sideband cooling works in the weak sideband coupling limit, where the sideband coupling strength is small compared to the natural linewidth $\gamma$ of the internal excited state, with a cooling rate much less than $\gamma$. Here we consider cooling schemes in the strong sideband coupling regime, where the sideband coupling strength is comparable or even greater than $\gamma$. We derive analytic expressions for the cooling rate and the average occupation of the motional steady state in this regime, based on which we show that one can reach a cooling rate which is proportional to $\gamma$, while at the same time the steady state occupation increases by a correction term proportional to $\eta^{2}$ compared to the weak sideband coupling limit. We demonstrate with numerical simulations that our analytic expressions faithfully recover the exact dynamics in the strong sideband coupling regime.",2011.09613v1 2021-01-10,Asymptotic interplay of states and adapted coupling gains in the Lohe hermitian sphere model,"We study emergent dynamics of the Lohe hermitian sphere (LHS) model with the same free flows under the dynamic interplay between state evolution and adaptive couplings. The LHS model is a complex counterpart of the Lohe sphere (LS) model on the unit sphere in Euclidean space, and when particles lie in the Euclidean unit sphere embedded in $\bbc^{d+1}$, it reduces to the Lohe sphere model. In the absence of interactions between states and coupling gains, emergent dynamics have been addressed in [22]. In this paper, we further extend earlier results in the aforementioned work to the setting in which the state and coupling gains are dynamically interrelated via two types of coupling laws, namely anti-Hebbian and Hebbian coupling laws. In each case, we present two sufficient frameworks leading to complete aggregation depending on the coupling laws, when the corresponding free flow is the same for all particles.",2101.03450v1 2021-01-21,Polaritonic non-locality in ultrastrong light-matter coupling,"Sub-wavelength electromagnetic field localization has been central in photonic research in the last decade, allowing to enhance sensing capabilities as well as increasing the coupling between photons and material excitations. The ultrastrong light-matter coupling regime in the THz range with split-ring resonators coupled to magnetoplasmons has been widely investigated, achieving successive world-records for the largest light-matter coupling ever achieved. Ever shrinking resonators have allowed to approach the regime of few electrons strong coupling, in which single-dipole properties can be modified by the vacuum field. Here we demonstrate, theoretically and experimentally, the existence of a limit to the possibility of arbitrarily increasing electromagnetic confinement in polaritonic systems. Strongly sub-wavelength fields can excite a continuum of high-momenta propagative magnetoplasmons. This leads to peculiar nonlocal polaritonic effects, as certain polaritonic features disappear and the system enters in the regime of bound-to-continuum strong coupling. Emerging nonlinearities due to the local breaking of Kohn's theorem are also reported.",2101.08709v1 2021-03-09,Strong Magnon-Magnon Coupling in Synthetic Antiferromagnets,"Synthetic antiferromagnet, comprised of two ferromagnetic layers separated by a non-magnetic layer, possesses two uniform precession resonance modes: in-phase acoustic mode and out-of-phase optic mode. In this work, we theoretically and numerically demonstrated the strong coupling between acoustic and optic magnon modes. The strong coupling is attributed to the symmetry breaking of the system, which can be realized by tilting the bias field or constructing an asymmetrical synthetic antiferromagnet. It is found that the coupling strength can be highly adjusted by tuning the tilting angle of bias field, the magnitude of antiferromagnetic interlayer exchange coupling, and the thicknesses of ferromagnetic layers. Furthermore, the coupling between acoustic and optic magnon modes can even reach the ultrastrong coupling regime. Our findings show high promise for investigating quantum phenomenon with a magnonic platform.",2103.05153v1 2021-03-09,Strong coupling effects in quantum thermal transport with the reaction coordinate method,"We present a semi-analytical approach for studying quantum thermal energy transport beyond the weak system-bath coupling regime. Our treatment, which results in a renormalized, effective Hamiltonian model is based on the reaction coordinate method. In our technique, applied to the nonequilibrium spin-boson model, a collective coordinate is extracted from each environment and added into the system to construct an enlarged system. After performing additional Hamiltonian's truncation and transformation, we attain an effective two-level system with renormalized parameters, which is weakly coupled to its environments, thus can be simulated using a perturbative Markovian quantum master equation approach. We compare the heat current characteristics in our method to other techniques, and demonstrate that we properly capture strong system-bath signatures such as the turnover behavior of the heat current as a function of system-bath coupling strength. We further investigate the thermal diode effect and demonstrate that strong couplings moderately improve the rectification ratio relative to the weak coupling limit. The effective Hamiltonian method that we developed here offers fundamental insight into the strong coupling behavior, and is computationally economic. Applications of the method towards studying quantum thermal machines are anticipated.",2103.05670v1 2021-03-17,All-optical quantum simulation of ultrastrong optomechanics,"The observation of single-photon optomechanical effects is a desired task in cavity optomechanics. However, the realization of ultrastrong optomechanical interaction remains a big challenge. Here, we present an all-optical scheme to simulate ultrastrong optomechanical coupling based on a Fredkin-type interaction, which consists of two exchange-coupled modes with the coupling strength depending on the photon number in another controller mode. This coupling enhancement is assisted by the displacement amplification according to the physical idea of the Bogoliubov approximation, which is realized by utilizing a strong driving to pump one of the two exchanging modes. Our numerical simulations demonstrate that the enhanced optomechanical coupling can enter the single-photon strong-coupling and even ultrastrong-coupling regimes. We also show the creation of macroscopic quantum superposed states and the implementation of a weak-to-strong transition for quantum measurement in this system. This work will pave the way to quantum simulation of single-photon optomechanical effects with current experimental platforms.",2103.09462v3 2021-03-18,Hierarchical structure of physical Yukawa couplings from matter field Kähler metric,"We study the impacts of matter field K\""ahler metric on physical Yukawa couplings in string compactifications. Since the K\""ahler metric is non-trivial in general, the kinetic mixing of matter fields opens a new avenue for realizing a hierarchical structure of physical Yukawa couplings, even when holomorphic Yukawa couplings have the trivial structure. The hierarchical Yukawa couplings are demonstrated by couplings of pure untwisted modes on toroidal orbifolds and their resolutions in the context of heterotic string theory with standard embedding. Also, we study the hierarchical couplings among untwisted and twisted modes on resolved orbifolds.",2103.10240v2 2021-03-31,"Vector fields, RG flows and emergent gauge symmetry","We consider the most general perturbatively renormalizable theory of vector fields in four dimensions with a global SU(N) symmetry and massless couplings. The Lagrangian contains 1 quadratic, 2 cubic and 4 quartic couplings. The RG flow among this set of 7 couplings is computed to 1-loop and a rich phase diagram is mapped out; in particular it is shown that a finite number of asymptotically free RG-flows exist corresponding to non-trivial fixed points for the ratios of the couplings. None of these are gauge theories, i.e. possess only global SU(N) invariance but not a local one. We also include the most general ghost couplings, still with global SU(N) invariance, and compute the RG flow to 1-loop for all 9 resulting couplings. Again asymptotically free RG flows exist with non-trivial fixed points for the ratios of couplings. It is shown that Yang-Mills theory emerges at a particular fixed point. The theories at the other fixed points are marginally relevant gauge symmetry violating perturbations of Yang-Mills theory. The large-N limit is also investigated in detail.",2103.17136v2 2021-04-06,Supersolid-like states in a two-dimensional trapped spin-orbit-coupled spin-1 condensate,"We study supersolid-like states in a quasi-two-dimensional trapped Rashba and Dresselhaus spin-orbit (SO) coupled spin-1 condensate. For small strengths of SO coupling $\gamma$ ($\gamma \lessapprox 0.75$), in the ferromagnetic phase, circularly-symmetric $(0,\pm 1, \pm 2)$- and $(\mp 1, 0,\pm 1)$-type states are formed where the numbers in the parentheses denote the angular momentum of the vortex at the center of the components and where the upper (lower) sign correspond to Rashba (Dresselhaus) coupling; in the antiferromagnetic phase, only $(\mp 1, 0,\pm 1)$-type states are formed. For large strengths of SO coupling, supersolid-like superlattice and superstripe states are formed in the ferromagnetic phase. In the antiferromagnetic phase, for large strengths of SO coupling, supersolid-like superstripe and multi-ring states are formed. For an equal mixture of Rashba and Dresselhaus SO couplings, only a superstripe state is found. All these states are found to be dynamically stable and hence accessible in an experiment and will enhance the fundamental understanding of crystallization onto spatially periodic states in solids.",2104.02197v1 2021-04-10,Q-balls Formation and the Production of Gravitational Waves With Non-minimal Gravitational Coupling,"We propose to introduce non-minimal couplings of Affleck-Dine (AD) field to gravity by adding the coupling of AD field to the Ricci scalar curvature. As the Jordan frame supergravity always predict $|\Phi|^2 {\cal R}/6$ type coupling for scalars with canonical kinetic terms, we propose a way to realize the required $c_0|\Phi|^2 {\cal R}$-type couplings with generic $c_0$ for canonical complex scalar fields after SUSY breaking. The impacts of such non-minimal gravitational couplings for AD field is shown, especially on the Q-balls formation and the associated gravitational wave (GW) productions. New form of scalar potential for AD field in the Einstein frame is obtained. By numerical simulations, we find that, with non-minimal gravitational coupling to AD field, Q-balls can successfully form even with the choice of non-negative $K$ parameter for $\xi>0$. The associated GW productions as well as their dependences on the $\xi$ parameter are also discussed.",2104.04682v3 2021-04-20,Computing Arlequin coupling coefficient for concurrent FE-MD approaches,"Arlequin coupling coefficient is essential for concurrent FE-MD models with overlapping domains, but the calculation of its value is quite difficult when the geometry of the coupling region is complicated. In this work, we introduce a general procedure for the preprocessing of a concurrent FE-MD model, given that the mesh and atoms have already been created. The procedure is independent of the geometry of the coupling region and can be used for both 2D and 3D problems. The procedure includes steps of determining the relative positions of atoms inside the FE elements in the coupling region, as well as computing the Arlequin coupling coefficient for an arbitrary point inside the coupling region or on its boundary. Two approaches are provided for determining the coefficient: the direct approach and the temperature approach.",2104.09746v1 2021-04-20,A large modulation of electron-phonon coupling and an emergent superconducting dome in doped strong ferroelectrics,"We use first-principles methods to study doped strong ferroelectrics (taking BaTiO$_3$ as a prototype). Here we find a strong coupling between itinerant electrons and soft polar phonons in doped BaTiO$_3$, contrary to Anderson/Blount's weakly coupled electron mechanism for ""ferroelectric-like metals"". As a consequence, across a polar-to-centrosymmetric phase transition in doped BaTiO$_3$, the total electron-phonon coupling is increased to about 0.6 around the critical concentration, which is sufficient to induce phonon-mediated superconductivity of about 2 K. Lowering the crystal symmetry of doped BaTiO$_3$ by imposing epitaxial strain can further increase the superconducting temperature via a sizable coupling between itinerant electrons and acoustic phonons. Our work demonstrates a viable approach to modulating electron-phonon coupling and inducing phonon-mediated superconductivity in doped strong ferroelectrics and potentially in polar metals. Our results also show that the weakly coupled electron mechanism for ""ferroelectric-like metals"" is not necessarily present in doped strong ferroelectrics.",2104.09904v1 2021-05-07,CMB Mode Coupling with Isotropic Polarization Rotation,"We provide a new analysis technique to measure the effect of the isotropic polarization rotation, induced by e.g. the isotropic cosmic birefringence from axion-like particles and a miscalibration of CMB polarization angle, via mode coupling in the cosmic microwave background (CMB). Several secondary effects such as gravitational lensing and CMB optical-depth anisotropies lead to mode coupling in observed CMB anisotropies, i.e., non-zero off-diagonal elements in the observed CMB covariance. To derive the mode coupling, however, we usually assume no parity violation in the observed CMB anisotropies. We first derive a new contribution to the CMB mode coupling arising from parity violation in observed CMB. Since the isotropic polarization rotation leads to parity violation in the observed CMB anisotropies, we then discuss the use of the new mode coupling for constraining the isotropic polarization angle. We find that constraints on the isotropic polarization angle by measuring the new mode-coupling contribution are comparable to that using the $EB$ cross-power spectrum in future high-sensitivity polarization experiments such as CMB-S4 and LiteBIRD. Thus, this technique can be used to cross-check results obtained by the use of the $EB$ cross-power spectrum.",2105.03367v1 2021-05-11,Vibronic coupling in energy transfer dynamics and two-dimensional electronic-vibrational spectra,"We introduce a heterodimer model in which multiple mechanisms of vibronic coupling and their impact on energy transfer can be explicitly studied. We consider vibronic coupling that arises through either Franck-Condon activity in which each site in the heterodimer has a local electron-phonon coupling and as Herzberg-Teller activity in which the transition dipole moment coupling the sites has an explicit vibrational mode-dependence. We have computed two-dimensional electronic-vibrational (2DEV) spectra for this model while varying the magnitude of these two effects and find that 2DEV spectra contain static and dynamic signatures of both types of vibronic coupling. Franck-Condon activity emerges through a change in the observed excitonic structure while Herzberg-Teller activity is evident in the appearance of significant side-band transitions that mimic the lower-energy excitonic structure. A comparison of quantum beating patterns obtained from analysis of the simulated 2DEV spectra shows that this technique can report on the mechanism of energy transfer, elucidating a means of experimentally determining the role of specific vibronic coupling mechanisms in such processes.",2105.04724v1 2021-05-12,Strong single-photon optomechanical coupling in a hybrid quantum system,"Engineering strong single-photon optomechanical couplings is crucial for optomechanical systems. Here, we propose a hybrid quantum system consisting of a nanobeam (phonons) coupled to a spin ensemble and a cavity (photons) to overcome it. Utilizing the critical property of the lower-branch polariton (LBP) formed by the ensemble-phonon interaction, the LBP-cavity coupling can be greatly enhanced by three orders magnitude of the original one, while the upper-branch polariton (UBP)-cavity coupling is fully suppressed. Our proposal breaks through the condition of the coupling strength less than the critical value in previous schemes using two harmonic oscillators. Also, strong Kerr effect can be induced in our proposal. This shows our proposed approach can be used to study quantum nonlinear and nonclassical effects in weakly coupled optomechanical systems.",2105.05379v3 2021-05-24,Partial synchronization in the Kuramoto model with attractive and repulsive interactions via the Bellerophon state,"We study two groups of nonidentical Kuramoto oscillators with differing frequency distributions. Coupling between the groups is repulsive, while coupling between oscillators of the same group is attractive. This asymmetry of interactions leads to an interesting synchronization behavior. For small coupling strength, the mean-fields of both groups resemble a more weakly coupled Kuramoto model. After increasing the coupling strength beyond a threshold, they reach the Bellerophon state of multiple clusters of averagely entrained oscillators. A further increase in the coupling strength then asymptotically transitions from the Bellerophon state to a single synchronized cluster. During this transition, the order parameters of both groups increase and resemble an equally strongly coupled Kuramoto model. Our analysis is based on the Ott-Antonsen mean-field theory.",2105.11117v1 2021-06-09,Chiral control of quantum states in non-Hermitian spin-orbit-coupled fermions,"Spin-orbit coupling is an essential mechanism underlying quantum phenomena such as the spin Hall effect and topological insulators. It has been widely studied in well-isolated Hermitian systems, but much less is known about the role dissipation plays in spin-orbit-coupled systems. Here, we implement dissipative spin-orbit-coupled bands filled with ultracold fermions, and observe parity-time symmetry breaking as a result of the competition between the spin-orbit coupling and dissipation. Tunable dissipation, introduced by state-selective atom loss, enables us to tune the energy gap and close it at the critical dissipation value, the so-called exceptional point. In the vicinity of the critical point, the state evolution exhibits a chiral response, which enables us to tune the spin-orbit coupling and dissipation dynamically, revealing topologically robust chiral spin transfer when the quantum state encircles the exceptional point. This demonstrates that we can explore non-Hermitian topological states with spin-orbit coupling.",2106.04874v2 2021-06-14,Semi-Implicit finite-difference methods to study the spin-orbit and coherently coupled spinor Bose-Einstein condensates,"We develop time-splitting finite difference methods, using implicit Backward-Euler and semi-implicit Crank-Nicolson discretization schemes, to study the spin-orbit coupled spinor Bose Einstein condensates with coherent coupling in quasi-one and quasi-two-dimensional traps. The split equations involving kinetic energy and spin-orbit coupling operators are solved using either time-implicit Backward-Euler or semi-implicit Crank-Nicolson methods. We explicitly develop the method for pseudospin-1/2, spin-1, and spin-2 condensates. The results for ground states obtained with time-splitting Backward-Euler and Crank-Nicolson methods are in excellent agreement with time-splitting Fourier spectral method which is one of the popular methods to solve the mean-field models for spin-orbit coupled spinor condensates. We confirm the emergence of different phases in spin-orbit coupled pseudospin-1/2, spin-1, and spin-2 condensates with coherent coupling.",2106.07762v1 2021-06-19,Approaching to the deep-strong photon-to-magnon coupling,"In this work, the ultra-strong photon-to-magnon coupling is demonstrated for on-chip multilayered superconductor/ferromagnet/insulator hybrid thin film structures reaching the coupling strength above 6 GHz, the coupling ratio about 0.6, the single-spin coupling strength about 350 Hz, and cooperativity about 10^4. High characteristics of coupling are achieved owing to a radical suppression of the photon phase velocity in electromagnetic resonator. With achieved coupling the spectrum reveals inapplicability of the Dicke model, and evidences contribution of the diamagnetic A^2 interaction term in the Hamiltonian of the system, which satisfies the Thomas-Reiche-Kuhn sum rule. The contribution of the A^2 term denotes validity of the Hopfield quantum model and manifests observation of a different hybrid polariton quasi-particle, namely, the plasmon-magnon polariton.",2106.10450v1 2021-06-23,Dynamics of dipolar Atom-Molecular BEC in a double well potential: Effect of atom-molecular coherent coupling,"In the present work we have studied the dynamics of dipolar atom-molecular Bose Einstein Condensates coupled via Feshbach Resonance in a double well potential. We have numerically solved four coupled GP like equations, two for left well and two for right well for this atom molecular coupled system. Our numerical results show that both the long-range dipole-dipole interaction (chosen to be positive) and the coherent coupling interaction (which is positive for bosons) facilitate the transmission of atoms and molecules from left well to the right well when the population in the right well dominates over that in the left well and is trapped for a period of time. Whereas in absence of any one of these interactions probability of transient transmission decreases. However in absence of both the interactions (dipole-dipole and coherent coupling) i.e. when only the repulsive contact interaction is present, it leads to self trapping in the left well for a period of time. It is also shown that the signature of coherent coupling between atoms and molecules on the density distribution of atoms in the double well potential is present both in absence and presence of dipole-dipole interaction.",2106.12274v1 2021-07-16,Influence of inter-sublattice coupling on the terahertz nutation spin dynamics in antiferromagnets,"Spin nutation resonance has been well-explored in one-sublattice ferromagnets. Here, we investigate the spin nutation in two-sublattice antiferromagnets as well as, for comparison, ferrimagnets with inter-and intra-sublattice nutation coupling. In particular, we derive the susceptibility of the two-sublattice magnetic system in response to an applied external magnetic field. To this end, the antiferromagnetic and ferrimagnetic (sub-THz) precession and THz nutation resonance frequencies are calculated. Our results show that the precession resonance frequencies and effective damping decrease with intra-sublattice nutation coupling, while they increase with inter -sublattice nutation in an antiferromagnet. However, we find that the THz nutation resonance frequencies decrease with both the intra-and inter-sublattice nutation couplings. For ferrimagnets, conversely, we calculate two nutation modes with distinct frequencies, unlike antiferromagnets. The exchange-like precession resonance frequency of ferrimagnets decreases with intra-sublattice nutation coupling and increases with inter-sublattice nutation coupling, like antiferromagnets, but the ferromagnetic-like precession frequency of ferrimagnets is practically invariant to the intra and inter-sublattice nutation couplings.",2107.07939v2 2021-07-21,Interfacial anisotropic exciton-polariton manifolds in ReS$_2$,"Light-matter coupling in van der Waal's materials holds significant promise in realizing Bosonic condensation and superfluidity. The underlying semiconductor's crystal asymmetry, if any, can be utilized to form anisotropic half-light half-matter quasiparticles. We demonstrate generation of such highly anisotropic exciton-polaritons at the interface of a biaxial layered semiconductor, stacked on top of a distributed Bragg reflector. The spatially confined photonic mode in this geometry couples with polarized excitons and their Rydberg states, creating a system of highly anisotropic polariton manifolds, displaying Rabi splitting of up to 68 meV. Rotation of the incident beam polarization is used to tune coupling strength and smoothly switch regimes from weak to strong coupling, while also enabling transition from one three-body coupled oscillator system to another. Light-matter coupling is further tunable by varying the number of weakly coupled optically active layers. Our work provides a versatile method of engineering devices for applications in polarization-controlled polaritonics and optoelectronics.",2107.09920v2 2021-08-23,Quantum dissipation with nonlinear environment couplings: Stochastic fields dressed dissipaton equation of motion approach,"Accurate and efficient simulation on quantum dissipation with nonlinear environment couplings remains nowadays a challenging task. In this work, we propose to incorporate the stochastic fields, which resolve just the nonlinear environment coupling terms, into the dissipaton-equation-of-motion (DEOM) construction. The stochastic fields are introduced via the Hubbard-Stratonovich transformation. After the transformation, the resulted stochastic-fields-dressed total Hamiltonian contains only linear environment coupling terms. On basis of that, a stochastic-fields-dressed DEOM (SFD-DEOM) can then be constructed. The resultant SFD-DEOM, together with the ensemble average over the stochastic fields, constitutes an exact and nonperturbative approach to quantum dissipation under nonlinear environment couplings. It is also of relatively high efficiency and stability due to the fact that only nonlinear environment coupling terms are dealt with stochastic fields while linear couplings are still treated as the usual DEOM. Numerical demonstrations are carried out on a two-state model system.",2108.10013v2 2021-08-16,Coherently Coupled Mixtures of Bose-Einstein Condensed Gases,"This paper summarizes some of the relevant features exhibited by bi-nary mixtures of Bose-Einstein condensates in the presence of coherent coupling at zero temperature. The coupling, which is experimentally produced by proper photon transitions, can either involve negligible momentum transfer from the electromagnetic radiation (Rabi coupling) or large momentum transfer (Raman coupling) associated with spin-orbit effects.The nature of the quantum phases exhibited by coherently coupled mixtures is discussed in detail, including their paramagnetic, ferromagnetic, and, in the case of spin-orbit coupling, supersolid phases.The behavior of the corresponding elementary excitations is discussed, with explicit emphasis on the novel features caused by the spin-like degree of freedom. Focus is further given to the topological excitations (solitons, vortices) as well as to the superfluid properties. The paper also points out relevant open questions which deserve more systematic theoretical and experimental investigations.",2108.10159v1 2021-08-31,Coupling disorder in a population of swarmalators,"We consider a population of two-dimensional oscillators with random couplings, and explore the collective states. The coupling strength between oscillators is randomly quenched with two values one of which is positive while the other is negative, and the oscillators can spatially {\it{move}} depending on the state variables for phase and position. We find that the system shows the phase transition from the incoherent state to the fully synchronized one at a proper ratio of the number of positive couplings to the total. The threshold is numerically measured, and analytically predicted by the linear stability analysis of the fully synchronized state. It is found that the random couplings induces the long-term state patterns appearing for constant strength. The oscillators move to the places where the randomly quenched couplings work as if annealed. We further observe that the system with mixed randomnesses for quenched couplings shows the combination of the deformed patterns understandable with each annealed averages.",2108.13613v2 2021-09-16,Strong Coupling between Propagating Magnons and High-order Gyrotropic Skyrmion Modes,"Inspired by the recent achievements of the strong magnons- and spin textures-photons coupling via dipolar interaction, the coupling between magnons and the local resonances of spin textures through direct exchange interaction is expected but not realized yet. In this work, we demonstrated the coherent coupling between propagating magnons and local skyrmion resonances. Besides the Rabbi coupling gap (RCG) in the frequency field dispersion, a magnonic analog of polariton gap, polaragnonic band gap (PBG), is also observed in the frequency-wavenumber dispersion. The realization of coupling requires the gyrotropic skyrmion modes to satisfy not only their quantum number larger than one but also their chirality opposite to that of magnons. The observed PBG and RCG can be controlled to exist within different Brillouin zones (BZs) as well as at BZ boundaries. The coupling strength can approach the strong regime by selecting the wavenumber of propagating magnons. Our findings could provide a pure magnonic platform for investigating quantum optics phenomena in quantum information technology.",2109.07671v1 2021-09-20,Dynamical States and Bifurcations in Coupled Thermoacoustic Oscillators,"The emergence of rich dynamical phenomena in coupled self-sustained oscillators, primarily synchronization and amplitude death, has attracted considerable interest in several fields of science and engineering. Here, we present a comprehensive theoretical study on the manifestation of these exquisite phenomena in a reduced-order model of two coupled Rijke tube oscillators, which are prototypical thermoacoustic oscillators. We characterize the dynamical behaviors of two such identical and non-identical oscillators by varying both system parameters (such as the uncoupled amplitudes and the natural frequencies of the oscillators) and coupling parameters (such as coupling strength and coupling delay). The present model captures all the dynamical phenomena -- namely synchronization, phase-flip bifurcation, amplitude death, and partial amplitude death -- observed previously in experiments on coupled Rijke tubes. By performing numerical simulations and deriving approximate analytical solutions, we systematically decipher the conditions and the bifurcations underlying the aforementioned phenomena. The insights provided by this study can be used to understand the interactions between multiple cans in gas turbines combustors and develop suitable control strategies to avert undesirable thermoacoustic oscillations in them.",2109.09600v2 2021-09-29,Magnetic interlayer coupling between ferromagnetic SrRuO$_3$ layers through a SrIrO$_3$ spacer,"A key element to tailor the properties of magnetic multilayers is the coupling between the individual magnetic layers. In case of skyrmion hosting multilayers, coupling of skyrmions across the magnetic layers is highly desirable. Here the magnetic interlayer coupling was studied in epitaxial all-oxide heterostructures of ferromagnetic perovskite SrRuO$_3$ layers separated by spacers of the strong spin-orbit coupling oxide SrIrO$_3$. This combination of oxide layers is being discussed as a potential candidate system to host N\'{e}el skyrmions. First order reversal curve (FORC) measurements were performed in order to distinguish between magnetic switching processes of the individual layers and to disentangle the signal of soft magnetic impurities from the samples$'$ signal. Additionally, FORC investigations enabled to determine whether the coupling between the magnetic layers is ferromagnetic or antiferromagnetic. The observed interlayer coupling strength was weak for all the heterostructures, with SrIrO$_3$ spacers between 2 monolayers and 12 monolayers thick.",2109.14292v2 2021-10-14,Thermalization in a Spin-Orbit coupled Bose gas by enhanced spin Coulomb drag,"An important component of the structure of the atom, the effects of spin-orbit coupling are present in many sub-fields of physics. Most of these effects are present continuously. We present a detailed study of the dynamics of changing the spin-orbit coupling in an ultra-cold Bose gas, coupling the motion of the atoms to their spin. We find that the spin-orbit coupling greatly increases the damping towards equilibrium. We interpret this damping as spin drag, which is enhanced by spin-orbit coupling rate, scaled by a remarkable factor of $8.9(6)$~s. We also find that spin-orbit coupling lowers the final temperature of the Bose gas after thermalization.",2110.07094v3 2021-10-31,Coupling-induced nonunitary and unitary scattering in anti-PT-symmetric non-Hermitian systems,"We investigate the properties of two anti-parity-time (anti-PT )-symmetric four-site scattering centers. The anti-PT -symmetric scattering center may have imaginary couplings, real couplings, and real on-site potentials. The only difference between the two scattering centers is the coupling between two central sites of the scattering center, which plays a crucial role in determining the parity of anti-PT symmetry and significantly affects the scattering properties. For the imaginary coupling, the even-parity anti-PT -symmetric scattering center possesses nonunitary scattering and the difference between the reflection and transmission is unity; for the real coupling, the odd-parity anti-PT -symmetric scattering center possesses unitary scattering and the sum of the reflection and transmission is unity. The coupling-induced different scattering behaviors are verified in the numerical simulations. Our findings reveal that a significant difference in the dynamics can be caused by a slight difference between two similar anti-PT -symmetric non-Hermitian scattering centers.",2111.00378v1 2021-11-04,Spiral wave chimeras in populations of oscillators coupled to a slowly varying diffusive environment,"Chimera states are firstly discovered in nonlocally coupled oscillator systems. Such a nonlocal coupling arises typically as oscillators are coupled via an external environment whose characteristic time scale $\tau$ is so small (i.e., $\tau \rightarrow 0$) that it could be eliminated adiabatically. Nevertheless, whether the chimera states still exist in the opposite situation (i.e., $\tau \gg 1$) is unknown. Here, by coupling large populations of Stuart-Landau oscillators to a diffusive environment, we demonstrate that spiral wave chimeras do exist in this oscillator-environment coupling system even when $\tau$ is very large. Various transitions such as from spiral wave chimeras to spiral waves or unstable spiral wave chimeras as functions of the system parameters are explored. A physical picture for explaining the formation of spiral wave chimeras is also provided. The existence of spiral wave chimeras is further confirmed in ensembles of FitzHugh-Nagumo oscillators with the similar oscillator-environment coupling mechanism. Our results provide an affirmative answer to the observation of spiral wave chimeras in populations of oscillators mediated via a slowly changing environment and give important hints to generate chimera patterns in both laboratory and realistic chemical or biological systems.",2111.02616v2 2021-11-09,Strong system-bath coupling reshapes characteristics of quantum thermal machines,"We study the performance of quantum absorption refrigerators, paradigmatic autonomous quantum thermal machines, and reveal central impacts of strong couplings between the working system and the thermal baths. Using the reaction coordinate quantum master equation method, which treats system-bath interactions beyond weak coupling, we discover that reshaping of the window of performance is a central outcome of strong system-bath couplings. This alteration of the cooling window stems from the dominant role of parameter renormalization at strong couplings. We further show that strong coupling admits direct transport pathways between the thermal reservoirs. Such beyond-second-order transport mechanisms are typically detrimental to the performance of quantum thermal machines. Our study reveals that it is inadequate to claim for either a suppression or an enhancement of the cooling performance at strong coupling when analyzed against a single parameter and in a limited domain. Rather, a comprehensive approach should be adopted so as to uncover the reshaping of the operation window.",2111.05302v1 2021-11-09,Three-Josephson Junctions Flux Qubit Couplings,"We analyze the coupling of two flux qubits with a general many-body projector into the low-energy subspace. Specifically, we extract the effective Hamiltonians that controls the dynamics of two qubits when they are coupled via a capacitor and/or via a Josephson junction. While the capacitor induces a static charge coupling tunable by design, the Josephson junction produces a magnetic-like interaction easily tunable by replacing the junction with a SQUID. Those two elements allow to engineer qubits Hamiltonians with $XX$, $YY$ and $ZZ$ interactions, including ultra-strongly coupled ones. We present an exhaustive numerical study for two three-Josephson junctions flux qubit that can be directly used in experimental work. The method developed here, namely the numerical tool to extract qubit effective Hamiltonians at strong coupling, can be applied to replicate our analysis for general systems of many qubits and any type of coupling.",2111.05373v1 2021-12-07,Convergence rate bounds for iterative random functions using one-shot coupling,"One-shot coupling is a method of bounding the convergence rate between two copies of a Markov chain in total variation distance, which was first introduced by Roberts and Rosenthal and generalized by Madras and Sezer. The method is divided into two parts: the contraction phase, when the chains converge in expected distance and the coalescing phase, which occurs at the last iteration, when there is an attempt to couple. One-shot coupling does not require the use of any exogenous variables like a drift function or a minorization constant. In this paper, we summarize the one-shot coupling method into the One-Shot Coupling Theorem. We then apply the theorem to two families of Markov chains: the random functional autoregressive process and the autoregressive conditional heteroscedastic (ARCH) process. We provide multiple examples of how the theorem can be used on various models including ones in high dimensions. These examples illustrate how the theorem's conditions can be verified in a straightforward way. The one-shot coupling method appears to generate tight geometric convergence rate bounds.",2112.03982v2 2021-12-08,Critical gravitational collapse of a non-minimally coupled scalar field,"We study the critical gravitational collapse of a massless scalar field non-minimally coupled to gravity, using a quadratic coupling function with a strength parameter $\xi$. We concentrate on critical phenomena of type II, and determine with an accuracy of at least $10^{-12}$ the value of the critical amplitude for collapse to a black hole, as well as the values of the critical and echoing exponents. Obtaining such high accuracy in the critical amplitude requires us to do a coordinate radial transformation that effectively increases resolution near the central regions by a factor of at least $10^3$. As expected, we find that for the case of small coupling the critical behaviour is very similar to that of a minimally coupled scalar field. On the other hand, for high coupling the dynamics become so violent that we need to introduce a special slicing condition, known as the shock-avoiding slicing condition, in order to avoid gauge pathologies that would otherwise cause our simulations to fail. With this new gauge condition we are able to perform high accuracy simulations even in the strong coupling regime, where we find that the critical and echoing exponents become significantly smaller, and that the echoing behavior is richer and can not be modelled by a single harmonic.",2112.04065v1 2021-12-09,Weakly coupled Hamilton-Jacobi systems without monotonicity condition: A first step,"In this paper, we mainly focus on the existence of the viscosity solutions of stationary weakly coupled Hamilton-Jacobi systems \begin{equation*} \left\{ \begin{aligned} &H_1(x,Du_1(x),u_1(x),u_2(x))=0,\\ &H_2(x,Du_2(x),u_2(x),u_1(x))=0. \end{aligned} \right.\ \end{equation*} An important quantity denoted by $\chi$ is proposed, which measures the strength of coupling. The condition for the existence result is $\chi<1$ with certain monotone assumptions, which can handle many situations that the classical monotonicity condition can not handle. Then we turn to consider the linear coupling case. We assume the coupling matrix $(\lambda_{ij}(x))_{i,j\in\{1,2\}}$ satisfies $\lambda_{ii}(x)>0$ and $\lambda_{ij}(x)<0$ for $i\neq j$ and $i,j\in\{1,2\}$. The existence of viscosity solutions is considered for the critical case $\chi=1$. This result can be thought as a weak KAM theorem for weakly coupled systems. In the appendix, the large time convergence of the viscosity solution of evolutionary weakly coupled systems is proved when $\chi<1$.",2112.04885v4 2021-12-11,Complete Synchronization of Coupled Oscillators Based on the Contraction Theory,"In this paper, the contraction theory is introduced and applied to the complete synchronization of complex networks of coupled oscillators. Based on the contraction theory, the conditions that make the virtual systems of the coupled-oscillator networks in three different constructions, including all-to-all topology, star topology, and ring topology, contracting are given, under which the coupled-oscillator networks are completely synchronized regardless of the initial conditions. As concrete examples, the conditions that the networks consisting of linearly coupled van der Pol and Duffing van der Pol oscillators are completely synchronized in any initial conditions are obtained. It is found that the virtual system of the network of linearly coupled Rayleigh van der Pol oscillators cannot be contracting for any coefficients, but its contraction region can be found. Using the trapping region method, the conditions for the networks of linearly coupled Rayleigh van der Pol oscillators with different coefficients that start in some specific regions to be completely synchronized are obtained.",2112.05912v1 2021-12-14,Strong coupling in a Au plasmonic antenna-SiO$_{2}$ layer system: a hybrid mode analysis,"A detailed analysis of the optical response of a system accommodating several coupled modes is needed for the complete understanding of the strong coupling effect. In this paper, we report on the analysis of scattering cross section spectra of Au antennas on a SiO$_{2}$ layer on a Si substrate in the IR region. A classical model of coupled oscillators is used for determining the resonant energies, damping rates and coupling strengths of four phonon polariton modes in the SiO$_{2}$ layer coupled to a localized surface plasmon mode in a Au antenna. The calculated Hopfield mixing coefficients then show the contribution of the individual uncoupled modes to the hybrid modes of the coupled system.",2112.07767v1 2021-12-16,Dynamic Transport Characteristics of Side-Coupled Double Quantum-Impurity Systems,"A systematic study is made on the time-dependent dynamic transport characteristics of the side-coupled double quantum-impurity system based on the hierarchical equations of motion. It is found that the transport current behaves like a single quantum dot when the coupling strength is low during tunneling or coulomb coupling. The dynamic current oscillates due to the temporal coherence of the electron tunneling device only when the tunneling transition is coupled. The oscillation frequency of the transport current is related to the step voltage applied by the lead, while the $T$, e-e interaction $U$ and the bandwidth $W$ have little influence. The amplitude of the current oscillation exists in positive correlation with $W$ and negative correlation with $U$. With the increase in coupling $t_{12}$ between impurities, the ground state of the system changes from a Kondo singlet of one impurity to a spin-singlet of two impurities. Moreover, lowering the temperature could promote the Kondo effect to intensify the oscillation of the dynamic current. When only the coulomb transition is coupled, it is found that the two split-off Hubbard peaks move upward and have different interference effects on the Kondo peak at the Fermi surface with the increase in $U_{12}$, from the dynamics point of view.",2112.08591v1 2021-12-21,Strong Coupling of Multimolecular Species to Soft Microcavities,"Can we couple multiple molecular species to soft-cavities? The answer to this question has relevance in designing open cavities for polaritonic chemistry applications. Due to the differences in adhesiveness it is difficult to couple multiple molecular species to open cavities in a controlled and precise manner. In this letter, we discuss the procedure to coat multiple dyes, TDBC and S2275, using a layer-by-layer deposition technique onto a dielectric microsphere so as to facilitate the multi molecule coupling. We observed the formation of a middle polariton branch due to the inter-molecular mixing facilitated by the whispering gallery modes. The coupling strength,2g, of the TDBC molecules were found to be 98 meV while that of S2275 molecules was 78 meV. The coupling strength was found to be greater than the cavity linewidth and the molecular absorption linewidth showing the system is in the strong coupling regime.",2112.11229v1 2021-12-22,Polaritonic Critical Coupling in a Hybrid Quasi-Bound States in the Continuum Cavity-WS$_2$ Monolayer System,"We theoretically propose and numerically demonstrate that perfect feeding of a polaritonic system with full electromagnetic energy under one-port beam incidence, referred to as polaritonic critical coupling, can be achieved in a hybrid dielectric metasurface-WS$_2$ monolayer structure. Polaritonic critical coupling, where the critical coupling and strong coupling are simultaneously attained, is determined by the relative damping rates of the cavity resonance, $\rm \gamma_Q$, provided by a symmetry-protected quasi-bound states in the continuum, and excitonic resonance of WS$_2$ monolayer, $\rm \gamma_X$. We reveal that the population of the polariton states can be tuned by the asymmetric parameter of the quasi-bound states in the continuum. Furthermore, polaritonic critical coupling is achieved in the designed system while $\rm \gamma_Q=\gamma_X$ and only strong coupling is achieved while $\rm \gamma_Q\neq\gamma_X$. This work enriches the study of polaritonic physics with controlled absorbance and may guide the design and application of efficient polariton-based light-emitting or lasing devices.",2112.11724v2 2021-12-27,The Scale of New Physics from the Higgs Couplings to $γγ$ and $γZ$,"Measuring the Higgs couplings accurately at colliders is one of the best routes for finding physics Beyond the Standard Model (BSM). If the measured couplings deviate from the SM predictions, then this would give rise to energy-growing processes that violate tree-level unitarity at some energy scale, indicating new physics. In this paper, we extend previous work on unitarity bounds from the Higgs potential and the Higgs couplings to vector bosons and the top quark; to the Higgs couplings to $\gamma\gamma$ and $\gamma Z$. We find that while the HL-LHC might be able to find new physics in the $\gamma Z$ sector, the scale of new physics in both sectors is mostly beyond its reach. However, accurate measurements of the leading couplings of the two sectors in the HL-LHC can place stringent limits on both the scale of new physics and on other Higgs couplings that are difficult to measure. In addition, the scale of new physics is mostly within the reach of the $100$ TeV collider.",2112.13529v5 2022-01-05,Probing of nonlinear hybrid optomechanical systems via partial accessibility,"Hybrid optomechanical systems are emerging as a fruitful architecture for quantum technologies. Hence, determining the relevant atom-light and light-mechanics couplings is an essential task in such systems. The fingerprint of these couplings is left in the global state of the system during non-equilibrium dynamics. However, in practice, performing measurements on the entire system is not feasible, and thus, one has to rely on partial access to one of the subsystems, namely the atom, the light, or the mechanics. Here, we perform a comprehensive analysis to determine the optimal subsystem for probing the couplings. We find that if the light-mechanics coupling is known or irrelevant, depending on the range of the qubit-light coupling, then the optimal subsystem can be either light or the qubit. In other scenarios, e.g., simultaneous estimation of the couplings, the light is usually the optimal subsystem. This can be explained as light is the mediator between the other two subsystems. Finally, we show that the widely used homodyne detection can extract a fair fraction of the information about the couplings from the light degrees of freedom.",2201.01784v1 2022-01-21,On the origin of noncollinear magnetization coupling across RuX layers,"We present a simple atomistic model for the description of noncollinear coupling in magnetic multilayers with hybrid spacer layers made of Ru alloyed to ferromagnetic atoms such as Fe. In contrast to previous analytical and micromagnetic models that explain the noncollinear coupling by means of lateral fluctuations in the coupling constant, the presented model accounts for atom-atom coupling in all three spatial dimensions within the spacer layer. The new model is able to accurately predict the dependence of the macroscopic bilinear and biquadratic coupling constants on the spacer-layer composition and thickness, showing much better quantitative agreement than lateral-fluctuation models. Moreover, it predicts noncollinear coupling even for infinitely stiff ferromagnetic layers which goes beyond the predictions of previous models.",2201.08624v1 2022-01-24,Coupled-channels calculations for nuclear reactions: from exotic nuclei to superheavy elements,"Atomic nuclei are composite systems, and they may be dynamically excited during nuclear reactions. Such excitations are not only relevant to inelastic scattering but they also affect other reaction processes such as elastic scattering and fusion. The coupled-channels approach is a framework which can describe these reaction processes in a unified manner. It expands the total wave function of the system in terms of the ground and excited states of the colliding nuclei, and solves the coupled Shr\""odinger equations to obtain the $S$-matrix, from which several cross sections can be constructed. This approach has been a standard tool to analyze experimental data for nuclear reactions. In this paper, we review the present status and the recent developments of the coupled-channels approach. This includes the microscopic coupled-channels method and its application to cluster physics, the continuum discretized coupled-channels (CDCC) method for breakup reactions, the semi-microscopic approach to heavy-ion subbarrier fusion reactions, the channel coupling effects on nuclear astrophysics and syntheses of superheavy elements, and inclusive breakup and incomplete fusion reactions of weakly-bound nuclei.",2201.09512v2 2022-02-01,Chaos in Coupled Heteroclinic Cycles and its Piecewise-Constant Representation,"We consider two stable heteroclinic cycles rotating in opposite directions, coupled via diffusive terms. A complete synchronization in this system is impossible, and numerical exploration shows that chaos is abundant at low levels of coupling. With increase of coupling strength, several symmetry-changing transitions are observed, and finally a stable periodic orbit appears via an inverse period-doubling cascade. To reveal the behavior at extremely small couplings, a piecewise-constant model for the dynamics is suggested. Within this model we construct a Poincar\'e map for a chaotic state numerically, it appears to be an expanding non-invertable circle map thus confirming abundance of chaos in the small coupling limit. We also show that within the piecewise-constant description, there is a set of periodic solutions with different phase shifts between subsystems, due to dead zones in the coupling.",2202.00288v1 2022-02-01,Proposal for a cavity-induced measurement of the exchange coupling in quantum dots,"In spin qubit arrays the exchange coupling can be harnessed to implement two-qubit gates and to realize intermediate-range qubit connectivity along a spin bus. In this work, we propose a scheme to characterize the exchange coupling between electrons in adjacent quantum dots. We investigate theoretically the transmission of a microwave resonator coupled to a triple quantum dot (TQD) occupied by two electrons. We assume that the right quantum dot (QD) is always occupied by one electron while the second electron can tunnel between the left and center QD. If the two electrons are in adjacent dots they interact via the exchange coupling. By means of analytical calculations we show that the transmission profile of the resonator directly reveals the value of the exchange coupling strength between two electrons. From perturbation theory up to second order we conclude that the exchange can still be identified in the presence of magnetic gradients. A valley splitting comparable to the inter-dot tunnel coupling will lead to further modifications of the cavity transmission dips that also depend on the valley phases.",2202.00797v1 2022-02-08,Electric and Magnetic Properties of Higher-Spin Kondo-Heisenberg Models at Strong Coupling,"We study higher-spin ($S \geq 1$) generalization of the one-dimensional Kondo-Heisenberg model, in which the local spin-$S$ moments of the Kondo lattice model interact with each other via the antiferromagnetic Heisenberg interaction ($J_{\text{H}}$), by analytical and numerical methods. The strong-coupling (i.e., large Kondo-coupling) expansion maps out an insulating phase at half-filling whose magnetic correlation depends on the parity of $2S$ as well as a ferromagnetic metallic phase which dominates the strong-coupling region at generic fillings. Then, we carried out the Density-Matrix Renormalization Group (DMRG) simulations for $S=1$ to closely investigate the phase structure at large but finite Kondo coupling. At half-filling, the Kondo coupling and $J_{\text{H}}$ do not compete and the insulating spin-gapless phase is stable, while the competition of the two leads to a stepwise collapse of the strong-coupling ferromagnetism via an intervening dimerized insulating phase with power-law spin correlation at quarter-filling.",2202.03708v2 2022-02-11,"""Stairway to Heaven"" -- Spectroscopy of Particle Couplings with Gravitational Waves","We discuss the possibility to measure particle couplings with stochastic gravitational wave backgrounds (SGWBs). Under certain circumstances a sequence of peaks of different amplitude and frequency -- a $stairway$ -- emerges in a SGWB spectrum, with each peak probing a different coupling. The detection of such signature opens the possibility to reconstruct couplings (spectroscopy) of particle species involved in high energy phenomena generating SGWBs. Stairway-like signatures may arise in causally produced backgrounds in the early Universe, e.g. from preheating or first order phase transitions. As a proof of principle we study a preheating scenario with an inflaton $\phi$ coupled to multiple $daughter$ fields $\lbrace \chi_j \rbrace$ with different coupling strengths. As a clear stairway signature is imprinted in the SGWB spectrum, we reconstruct the relevant couplings with various detectors.",2202.05805v1 2022-02-19,Numerical optimization of single-mode fiber-coupled single-photon sources based on semiconductor quantum dots,"We perform extended numerical studies to maximize the overall photon coupling efficiency of fiber-coupled quantum dot single-photon sources emitting in the near-infrared and telecom regime. Using the finite element method, we optimize the photon extraction and fiber-coupling efficiency of quantum dot single-photon sources based on micromesas, microlenses, circular Bragg grating cavities and micropillars. The numerical simulations which consider the entire system consisting of the quantum dot source itself, the coupling lens, and the single-mode fiber yield overall photon coupling efficiencies of up to 83%. Our work provides objectified comparability of different fiber-coupled single-photon sources and proposes optimized geometries for the realization of practical and highly efficient quantum dot single-photon sources.",2202.09562v1 2022-03-01,Tunable Nonlinearity and Efficient Harmonic Generation from a Strongly Coupled Light-Matter System,"Strong light-matter coupling within electromagnetic environments provides a promising path to modify and control chemical and physical processes. The origin of the enhancement of nonlinear optical processes such as second-harmonic and third-harmonic generation (SHG and THG) due to strong light-matter coupling is attributed to distinct physical effects which questions the relevance of strong coupling in these processes. In this work, we leverage a first-principles approach to investigate the origins of the experimentally observed enhancement of resonant SHG and THG under strong light-matter coupling. We find that the enhancement of the nonlinear conversion efficiency has its origins in a modification of the associated nonlinear optical susceptibilities as polaritonic resonances emerge in the nonlinear spectrum. Further, we find that the nonlinear conversion efficiency can be tuned by increasing the light-matter coupling strength. Finally, we provide a general framework to compute the harmonic generation spectra from the displacement field as opposed to the standard approach which computes the harmonic spectrum from the matter-only induced polarization. Our results address a key debate in the field, and pave the way for predicting and understanding quantum nonlinear optical phenomena in strongly coupled light-matter systems.",2203.00691v1 2022-03-30,Quantitative determination of interlayer electronic coupling at various critical points in bilayer MoS2,"Tailoring interlayer coupling has emerged as a powerful tool to tune the electronic structure of van der Waals (vdW) bilayers. One example is the usage of the moire pattern to create controllable two-dimensional electronic superlattices through the configurational dependence of interlayer electronic couplings. This approach has led to some remarkable discoveries in twisted graphene bilayers, and transition metal dichalcogenide (TMD) homo- and hetero-bilayers. However, a largely unexplored factor is the interlayer distance, d, which can impact the interlayer coupling strength exponentially. In this letter, we quantitatively determine the coupling strengths as a function of interlayer spacing at various critical points of the Brillouin zone in bilayer MoS2. The exponential dependence of the coupling parameter on the gap distance is demonstrated. Most significantly, we achieved a 280% enhancement of K-valley coupling strength with an 8% reduction of the vdW gap, pointing to a new strategy in designing a novel electronic system in vdW bilayers.",2203.16189v1 2022-04-20,Role of long-range coupling on the properties of single polarons in models with dual electron-phonon couplings,"We use the Variational Exact Diagonalization to investigate the single polaron properties for four different dual models, combining a short-range off-diagonal (Peierls) plus a longer-range diagonal (Holstein or breathing-mode) coupling. This allows us to investigate the sensitivity of various polaron properties both to the range of the diagonal coupling and to the specific diagonal coupling chosen. We find strong sensitivity to the range for all duals models as the adiabatic limit is approached, however considerable sensitivity is observed for some quantities even for large phonon frequencies. Also, the strong dependence of the results on the specific form of the diagonal coupling is observed everywhere in the parameter space. Taken together, these results suggest that careful consideration must be given to the specific coupling and its proper range when quantitative comparisons with experiments are sought.",2204.09199v1 2022-04-22,Coherent interaction of a-few-electron quantum dot with a terahertz optical resonator,"We have investigated light-matter hybrid excitations in a quantum dot (QD)-terahertz (THz) optical resonator coupled system. We fabricate a gate-defined QD in the vicinity of a THz split-ring resonator (SRR) by using a AlGaAs/GaAs two-dimensional electron system (2DES). By illuminating the system with THz radiation, the QD shows a current change whose spectrum exhibits coherent coupling between the electrons in the QD and the SRR as well as coupling between the 2DES and the SRR. The latter coupling enters the ultrastrong coupling regime and the coupling between the QD and the SRR is also very close to the ultrastrong coupling regime, despite the fact that only a few electrons reside in the QD.",2204.10522v2 2022-04-22,One-transmitter Multiple-receiver Wireless Power Transfer System Using an Exceptional Point of Degeneracy,"Robust transfer efficiency against the various operating conditions in a wireless power transfer system remains a fundamentally important challenge. This challenge becomes even more critical when transferring power to groups of inductively coupled receivers. We propose a method for efficient wireless power transfer to multiple receivers exploiting the concept of exceptional points of degeneracy (EPD). In previous studies based on PT symmetry, a receiver's operation has been divided into two strong and weak coupling regimes, and the power transfer efficiency is constant in the strong coupling regime when varying the coupling factor.Here the concept of strong and weak coupling and constant power efficiency is extended to a system of multiple receivers that do not follow PT symmetry. We show that the important feature to have a roughly constant power efficiency, independently of the positions of the receivers, is the existence of an EPD that separates the weak and strong regimes. Our proposed method demonstrates a system with less sensitivity to the coupling change than a conventional system without EPD when the receivers and their couplings to the transmitter are not necessarily identical.",2204.10928v1 2022-06-10,System size dependent topological zero modes in coupled topolectrical chains,"In this paper, we demonstrate the emergence and disappearance of topological zero modes (TZMs) in a coupled topolectrical (TE) circuit lattice. Specifically, we consider non-Hermitian TE chains in which TZMs do not occur in the individual uncoupled chains, but emerge when these chains are coupled by inter-chain capacitors. The coupled system hosts TZMs which show size-dependent behaviours and vanish beyond a certain critical size. In addition, the emergence or disappearance of the TZMs in the open boundary condition (OBC) spectra for a given size of the coupled system can be controlled by modulating the signs of its inverse decay length. Analytically, trivial and non-trivial phases of the coupled system can be distinguished by the differing ranks of their corresponding Laplacian matrix. The TE circuit framework enables the physical detection of the TZMs via electrical impedance measurements. Our work establishes the conditions for inducing TZMs and modulating their behavior in coupled TE chains.",2206.05298v1 2022-06-14,Axion Couplings in Grand Unified Theories,"We show that the couplings of axions to gauge bosons are highly restricted in Grand Unified Theories where the standard model is embedded in a simple 4D gauge group. The topological nature of these couplings allows them to be matched from the UV to the IR, and the ratio of the anomaly with photons and gluons for any axion is fixed by unification. This implies that there is a single axion, the QCD axion, with an anomalous coupling to photons. Other light axion-like particles can couple to photons by mixing through the QCD axion portal and lie to the right of the QCD line in the mass-coupling plane. Axions which break the unification relation between gluon and photon couplings are necessarily charged under the GUT gauge group and become heavy from perturbative mass contributions. A discovery of an axion to the left of the QCD line can rule out simple Grand Unified models. Axion searches are therefore tabletop and astrophysical probes of Grand Unification.",2206.07053v2 2022-06-26,Maximum Electro-Momentum Coupling in Piezoelectric Metamaterial Scatterers,"Analogous to electromagnetic bianisotropy, engineered piezoelectric metamaterials can possess electro-momentum coupling between the macroscopic momentum and electric stimuli. This indicates the applicability of piezoelectric metamaterials for wave scattering with an extra design degree of freedom, in the same way as acoustic materials with Willis coupling between the macroscopic momentum and strain. To fully utilize this novel bianisotropy, we derive for the first time tight theoretical bounds on the effect of electro-momentum coupling on scatterers based on energy conservation and combining two acoustic and electromagnetic polarizability tensors to analyze passive bianisotropic scatterers under both acoustic and electromagnetic waves. Our derived bounds are verified by comparing them with analytical scattering solutions. Results show that the bianisotropic scattering performance can be of the same order as the non-bianisotropic terms via the aid of electro-momentum coupling, even for simple designs with small Willis coupling. We further reveal the possibility of utilizing electro-momentum coupling for tunable scattering-cloaking applications of the subwavelength-sized scatterers. This sheds light on the promising potential of piezoelectric metamaterials for tunable scattering devices in which bianisotropy can be modulated by external electric stimuli.",2206.12789v1 2022-07-10,Absorption and photoluminescence properties of coupled plasmon-exciton (plexciton) systems,"Plexciton is the formation of new hybridized energy states originated from the coupling between plasmon and exciton. To reveal the optical properties of both exciton and plexciton, we develop a classic oscillator model to describe the behavior of them. Particularly, the coupling case, i.e., plexciton, is investigated theoretically in detail. In strong coupling, the electromagnetically induced transparency is achieved for the absorption spectra; the splitting behaviors of the modes are carefully analyzed, and the splitting largely depends on the effective number of the electrons and the resonance coupling; the photoluminescence spectra show that the spectral shapes remain almost unchanged for weak coupling and change a lot for strong coupling; the emission intensity of the exciton is strongly enhanced by the plasmon and can reach to the order of $10^{10}$ for a general case. We also show the comparisons between our model and the published experiments to validate its validity. This work may be useful for understanding the mechanism of the plexciton and for the development of new applications.",2207.04382v1 2022-07-20,Couplings of order six in the gauge field strength and the second fundamental form on a D$_p$-brane at order $α'^2$,"Using the assumption that the independent gauge invariant couplings on the world-volume of the non-perturbative objects in the string theory are independent of the background, we find the four and the six gauge field strength and/or the second fundamental form couplings on the world volume of a D$_p$-brane in the superstring theory at order $\alpha'^2$ in the normalization that $F$ is dimensionless. We have found them by considering the particular background which has one circle and by imposing the corresponding T-duality constraint on the independent couplings. In particular, we find that there are 12+146 independent gauge invariant couplings at this order, and the T-duality constraint can fix 150 of them. We show that these couplings are fully consistent with the partial results in the literature. This comparison also fixes the remaining 8 couplings.",2207.09834v2 2022-08-23,Anisotropic inflation in non-minimal kinetic coupling model,"We study anisotropic inflation in non-minimal derivative coupling model where the scalar field non-minimally coupled to the $U(1)$ gauge fields and derivative of the scalar field non-minimally coupled to the Einstein tensor. Within the framework we find power-law anisotropic solutions in this model when both the inflaton potential and the gauge kinetic function are power-law type in the high friction regime. We show the ratio of anisotropy to the expansion rate is nearly constant, small and proportional to the slow-roll parameters of the theory. As a demonstration, we consider numerically calculation of the model to show that the behavior of anisotropy by changing the parameters of the model for quadratic inflationary potential. There is anisotropic attractor solution for a wide range of values of the model parameters. We show both numerically and analytically that there are two phases of inflation, similar to those an anisotropic inflation in minimal coupling model, isotropic and anisotropic phase. We can change the number of e-folds corresponding to each phase of slow roll inflation by changing the gauge coupling constant or non-minimal derivative coupling constant. There are the best agreement with the numerically solutions and analytically solutions in this investigation.",2208.10757v2 2022-08-26,Superradiant Phase Transition in the Strong Coupling Regime,"The Dicke model can exhibit quantum phase transition between the normal and the superradiant phases when the strength of the light-matter coupling exceeds the ultrastrong coupling regime. However, it is challenging to observe this phase transition in practical systems due to limited coupling strength or finite two-photon $A^{2}$ terms. Here we show that by applying a periodic modulation to the frequency of the two-level systems in a standard Dicke model in the strong coupling regime, an anisotropic Dicke model with tunable rotating and counter-rotating terms in the ultrastrong coupling regime can be achieved. We calculate the ground state and the excitation spectrum of this model in terms of the modulation parameters. Our result shows that the superradiant phases can be observed in cavity- or circuit-quantum electrodynamics systems with strong coupling.",2208.12524v1 2022-09-01,Strong coupling between excitons and quasi-Bound states in the continuum in the bulk transition metal dichalcogenides,"We investigate the strong coupling between the excitons and quasi-bound states in the continuum (BIC) resonance in a bulk WS$_2$ metasurface. Here we employ the bulk WS$_2$ to construct an ultrathin nanodisk metasurface, supporting the symmetry-protected magnetic dipole (MD) quasi-BIC resonance, which can self-hybridize with the excitons and lead to a strong light-matter interaction enhancement within the structure without the necessity for an external cavity. This strong coupling can be charactered by the considerable Rabi splitting of 159 meV and the clearly anti-crossing behavior appeared in the absorption spectrum. Furthermore, we analyze such light-matter coupling by constructing a Hamiltonian model including the surplus excitons, and tune the interaction from weak coupling to strong coupling regimes via the tunability radiation loss of the quasi-BIC resonance. Our results have great potential for manipulating the exciton-polaritons at room temperature, and provide a promising prospect for photonic devices that exploit strong coupling in applications.",2209.00416v1 2022-09-03,Berry Phase and Topology in Ultrastrongly Coupled Quantum Light-Matter Systems,"Strong coupling between matter and quantized electromagnetic fields in a cavity has emerged as a possible route toward controlling the phase of matter in the absence of an external drive. We develop a faithful and efficient theoretical framework to analyze quantum geometry and topology in materials ultrastrongly coupled to cavity electromagnetic fields in two dimensions. The formalism allows us to accurately evaluate geometrical and topological quantities, such as Berry phase and Chern number, in ultrastrong and deep strong coupling regimes. We apply our general framework to analyze a concrete model of massive Dirac fermions coupled to a circularly polarized cavity mode. Surprisingly, in addition to an ordinary transition to the topological phase, our analysis reveals a qualitatively new feature in deep strong coupling regimes, namely, the emergence of reentrant transition to the topologically trivial phase. We also present its intuitive understanding by showing the unitary mapping between the low-energy effective theory of strongly coupled light-matter systems and the Haldane honeycomb model.",2209.01363v2 2022-09-06,Quantum Electrodynamical Metamaterials,"Recent experiments have revealed ultrastrong coupling between light and matter as a promising avenue for modifying material properties, such as electrical transport, chemical reaction rates, and even superconductivity. Here, we explore (ultra)strong coupling as a means for manipulating the optical response of metamaterials based on ensembles of constituent units individually in the ultrastrong coupling regime. We develop a framework based on linear response for quantum electrodynamical systems to study how light-matter coupling affects the optical response. We begin by applying this framework to find the optical response of a two-level emitter coupled to a single cavity mode, which could be seen as a ""meta-atom"" of a metamaterial built from repeated units of this system. We find optical behaviors ranging from that of a simple two-level system (Lorentz-oscillator) to effectively transparent, as the coupling goes from the weak to deep strong coupling regimes. We explore a one-dimensional chain of these meta-atoms, demonstrating the tunability of its optical behavior. Our scheme may ultimately provide a framework for designing new metamaterials with low-loss, highly-confined modes, as well as tunable (single-photon) nonlinearities.",2209.02656v1 2022-09-07,Quantum reservoir neural network implementation on coherently coupled quantum oscillators,"Quantum reservoir computing is a promising approach for quantum neural networks, capable of solving hard learning tasks on both classical and quantum input data. However, current approaches with qubits suffer from limited connectivity. We propose an implementation for quantum reservoir that obtains a large number of densely connected neurons by using parametrically coupled quantum oscillators instead of physically coupled qubits. We analyse a specific hardware implementation based on superconducting circuits: with just two coupled quantum oscillators, we create a quantum reservoir comprising up to 81 neurons. We obtain state-of-the-art accuracy of 99 % on benchmark tasks that otherwise require at least 24 classical oscillators to be solved. Our results give the coupling and dissipation requirements in the system and show how they affect the performance of the quantum reservoir. Beyond quantum reservoir computing, the use of parametrically coupled bosonic modes holds promise for realizing large quantum neural network architectures, with billions of neurons implemented with only 10 coupled quantum oscillators.",2209.03221v3 2022-09-08,Inflationary magnetogenesis of primordial magnetic fields with multiple vector fields,"In this paper, we discussed the multiple vector fields during the inflation era and the inflationary magnetogenesis with multiple vector fields. Instead of a single coupling function in single vector field models, the coupling matrix between vector fields and scalar field which drive the inflation is introduced. The dynamical equations for multiple vector fields are obtained and applied to the inflation era. We discussed three cases for the double-field model. In no mutual-coupling case, one can find that both electric and magnetic spectrum can be scale-invariant at the end of inflation, meanwhile, the strong coupling problem can be avoided. The effect of mutual-coupling between different vector fields is also discussed. We found that weak mutual-coupling can lead to the slightly blue spectrum of the magnetic field. On the other hand, in the strong mutual-coupling case, the scale-invariant magnetic spectrum can also be obtained but the energy density of electromagnetic fields either lead to the backreaction problem or is diluted by inflation.",2209.03545v3 2022-09-13,Explosive transitions in interacting star networks,"We study transition to phase synchronization in an ensemble of Stuart-Landau oscillators interacting on a star network. We observe that by introducing frequency weighted coupling and time scale variations in the dynamics of nodes, system exhibits a first order explosive transition to phase synchrony. Further, we extend this study to understand the nature of synchronization in case of two coupled star networks. In presence of symmetry preserving (direct) coupling between the hubs of the two stars, we observe that hysteresis width first increases and then saturates for increasing inter-star coupling strength. For symmetry breaking (conjugate) coupling, the hysteresis width first increases and then decreases with increasing inter-star coupling. As we increase the inter-star coupling further, the transition gradually becomes a second order.",2209.06048v1 2022-09-15,Strong photon antibunching effect in a double cavity optomechanical system with intracavity squeezed light,"We study the behaviour of the second-order correlation function in a double cavity optomechanical system and a degenerate optical parametric amplifier (OPA) is placed in each cavity. The first cavity is additionally driven by a weak classical laser field. The occurrence of strong photon antibunching effect in these two coupled cavities is observed. For suitable values of optomechanical coupling strength as well as photon hopping process, the system can exhibit a very strong photon antibunching effect. Our study also shows that the unconventional photon blockade occurs in both coupling, i.e. the weak coupling as well as in the strong coupling regimes as compared to the conventional photon blockade which occurs only in the strong coupling regime. We get a very strong photon antibunching effect under the unconventional photon blockade mechanism than the conventional photon blockade mechanism. Our study can be also used for the generation of single photon in coupled nonlinear optomechanical systems.",2209.07401v2 2022-09-30,Thermal quantum coherence of two-qutrit Heisenberg XXZ model with Herring-Flicker coupling and Dzyaloshinskii-Moriya interaction under magnetic field,"In this study, we use the concept of $l_1$-norm coherence to characterize the entanglement of a two--qutrit Heisenberg XXZ model for subject to a uniform magnetic field and z--axis Dzyaloshinskii--Moriya interaction with Herring-Flicker coupling. We show the temperature, magnetic field, DM interaction, and distance of Herring-Flicker coupling all can control the entanglement. However, the state system becomes less entangled at high temperatures or strong magnetic fields and vice versa. Our findings also suggest that entanglement rises when the z--axis DM interaction increases. Moreover, by setting the strengths coupling of the spin, we quickly recover the isotropic XY and XXX Heisenberg models. Finally, Herring-Flicker coupling affects the degree of entanglement. In fact, when Herring-Flicker coupling and temperature are at small values, the degree of entanglement is at its highest. Still, when Herring-Flicker coupling is at substantial values, the degree of entanglement tends to stabilize.",2209.15311v3 2022-10-31,Higher-derivative couplings and torsional Riemann curvature,"Using the most general higher-derivative field redefinition for the closed spacetime manifolds, we show that the tree-level couplings of the metric, $B$-field and dilaton at orders $\alpha'^2$ and $\alpha'^3$ that have been recently found by the T-duality, can be written in a particular scheme in terms of the torsional Riemann curvature ${\cal R}$ and the torsion tensor $H$. The couplings at order $\alpha'^2$ have structures ${\cal R}^3, H^2 {\cal R}^2$, $H^6$, and the couplings at order $\alpha'^3$ have only structures ${\cal R}^4$, $H^2{\cal R}^3$. Replacing ${\cal R}$ with the ordinary Riemann curvature, the couplings in the structure $H^2{\cal R}^3$ reproduce the couplings found in the literature by the S-matrix method.",2210.17069v3 2022-12-11,Manifestation of the coupling phase in microwave cavity magnonics,"The interaction between microwave photons and magnons is well understood and originates from the Zeeman coupling between spins and a magnetic field. Interestingly, the magnon/photon interaction is accompanied by a phase factor which can usually be neglected. However, under the rotating wave approximation, if two magnon modes simultaneously couple with two cavity resonances, this phase cannot be ignored as it changes the physics of the system. We consider two such systems, each differing by the sign of one of the magnon/photon coupling strengths. This simple difference, originating from the various coupling phases in the system, is shown to preserve, or destroy, two potential applications of hybrid photon/magnon systems, namely dark mode memories and cavity-mediated coupling. The observable consequences of the coupling phase in this system is akin to the manifestation of a discrete Pancharatnam-Berry phase, which may be useful for quantum information processing.",2212.05389v1 2022-12-21,Top Yukawa Coupling at the Muon Collider,"We have presented a detailed study about the prospects for the measurement of the top Yukawa coupling in the vector boson fusion (VBF) production of a top quark pair at high energy muon colliders. By employing the effective $W$ approximation and the high energy limit for the helicity amplitudes of the subprocess $W^+ W^- \rightarrow t \bar t$, we have derived the energy scaling of the statistical signal significance in the presence of the anomalous couplings. The sensitivity on the top Yukawa coupling decreases as the bin energy increases. For the anomalous triple gauge boson couplings and the gauge-boson-fermion couplings with $E^2$ energy growing behavior for the interference term, the signal significance has mild increase at the beginning and start to decrease for $\hat s_{t \bar t} \sim 0.2 \, s_{\mu^+ \mu^-} $. The 95\% C.L. on the anomalous top Yukawa coupling is projected to be 5.6\% (1.7\%) at a 10 (30) TeV muon collider, which is comparable to the sensitivity of 2\% at the 100 TeV collider.",2212.11067v1 2023-01-27,Quantum Langevin theory for two coupled phase-conjugated electromagnetic waves,"While loss-gain-induced Langevin noises have been intensively studied in quantum optics, the effect of a complex-valued nonlinear coupling coefficient on the noises of two coupled phase-conjugated optical fields has never been questioned before. Here, we provide a general macroscopic phenomenological formula of quantum Langevin equations for two coupled phase-conjugated fields with linear loss (gain) and complex nonlinear coupling coefficient. The macroscopic phenomenological formula is obtained from the coupling matrix to preserve the field commutation relations and correlations, which does not require knowing the microscopic details of light-matter interaction and internal atomic structures. To validate this phenomenological formula, we take spontaneous four-wave mixing in a double-$\Lambda$ four-level atomic system as an example to numerically confirm that our macroscopic phenomenological result is consistent with that obtained from the microscopic Heisenberg-Langevin theory. Finally, we apply the quantum Langevin equations to study the effects of linear gain and loss, complex phase mismatching, as well as complex nonlinear coupling coefficient in entangled photon pair (biphoton) generation, particularly to their temporal quantum correlations.",2301.11993v1 2023-02-17,Resonance fluorescence of two asymmetrically pumped and coupled two-level systems,"We study a driven-dissipative duo of two-level systems in an open quantum systems approach, modelling a pair of atoms or (more generally) meta-atoms. Allowing for complex-valued couplings in the setup, which are of both a coherent and incoherent character, gives rise to a diverse coupling landscape. We consider several points on this landscape, for example where the coupling between the two coupled two-level systems is dominated by coherent, incoherent, unsymmetrical and even unidirectional interactions. Traversing the coupling terrain leads to remarkable features in the populations of the pair, correlations and optical spectra. Most notably, the famous Mollow triplet spectrum for a single atom may be superseded for a pair by a Mollow quintuplet (or even by a spectral singlet) and the setup allows for population trapping to arise, all depending upon the precise nature of the coupling between the two-level systems.",2302.09020v1 2023-03-02,Measuring spatio-temporal couplings using modal spatio-spectral wavefront retrieval,"Knowledge of spatio-temporal couplings such as pulse-front tilt or curvature is important to determine the focused intensity of high-power lasers. Common techniques to diagnose these couplings are either qualitative or require hundreds of measurements. Here we present both a new algorithm for retrieving spatio-temporal couplings, as well as novel experimental implementations. Our method is based on the expression of the spatio-spectral phase in terms of a Zernike-Taylor basis, allowing us to directly quantify the coefficients for common spatio-temporal couplings. We take advantage of this method to perform quantitative measurements using a simple experimental setup, consisting of different bandpass filters in front of a Shack-Hartmann wavefront sensor. This fast acquisition of laser couplings using narrowband filters, abbreviated FALCON, is easy and cheap to implement in existing facilities. To this end, we present a measurement of spatio-temporal couplings at the ATLAS-3000 petawatt laser using our technique.",2303.01360v1 2023-03-02,Multi player Parrondo games with rigid coupling,"In the original Parrondo game, a single player combines two losing strategies to a winning strategy. In this paper we investigate the question what happens, if two or more players play Parrondo games in a coordinated way. We introduce a strong coupling between the player such that the gain or loss of all players in one round is the same. We investigate two possible realizations of such a coupling. For both we show that the coupling increases the gain per player. The dependency of the gain on the various parameters of the games is determined. The coupling can not only lead to a larger gain, but it can also dominate the driving mechanism of the uncoupled games. Which driving mechanism dominates, depends on the type of coupling. Both couplings are set side by side and the main similarities and differences are emphasised.",2303.01361v2 2023-03-04,Coupled Multiwavelet Neural Operator Learning for Coupled Partial Differential Equations,"Coupled partial differential equations (PDEs) are key tasks in modeling the complex dynamics of many physical processes. Recently, neural operators have shown the ability to solve PDEs by learning the integral kernel directly in Fourier/Wavelet space, so the difficulty for solving the coupled PDEs depends on dealing with the coupled mappings between the functions. Towards this end, we propose a \textit{coupled multiwavelets neural operator} (CMWNO) learning scheme by decoupling the coupled integral kernels during the multiwavelet decomposition and reconstruction procedures in the Wavelet space. The proposed model achieves significantly higher accuracy compared to previous learning-based solvers in solving the coupled PDEs including Gray-Scott (GS) equations and the non-local mean field game (MFG) problem. According to our experimental results, the proposed model exhibits a $2\times \sim 4\times$ improvement relative $L$2 error compared to the best results from the state-of-the-art models.",2303.02304v4 2023-03-15,On the number of subproblem iterations per coupling step in partitioned fluid-structure interaction simulations,"In literature, the cost of a partitioned fluid-structure interaction scheme is typically assessed by the number of coupling iterations required per time step, while ignoring the internal iterations within the nonlinear subproblems. In this work, we demonstrate that these internal iterations have a significant influence on the computational cost of the coupled simulation. Particular attention is paid to how limiting the number of iterations within each solver call can shorten the overall run time, as it avoids polishing the subproblem solution using unconverged coupling data. Based on systematic parameter studies, we investigate the optimal number of subproblem iterations per coupling step. Lastly, this work proposes a new convergence criterion for coupled systems that is based on the residuals of the subproblems and therefore does not require any additional convergence tolerance for the coupling loop.",2303.08513v1 2023-03-24,One-loop algebras and fixed flow trajectories in adjoint multi-scalar gauge theory,"We study the one loop renormalisation of 4d $SU(N)$ Yang-Mills theory with $M$ adjoint representation scalar multiplets related by $O(M)$ symmetry. General $M$ are of field theoretic interest, and the 4d one loop beta function of the gauge coupling $g^2$ vanishes for the case $M=22$, which is intriguing for string theory. This case is related to D3 branes of critical bosonic string theory in $D=22+4=26$. An RG fixed point could have provided a definition for a purely bosonic AdS/CFT, but we show that scalar self-couplings $\lambda$ ruin one-loop conformal invariance in the large $N$ limit. There are real fixed flows (fixed points of $\lambda/g^2$) only for $M\ge 406$, rendering one-loop fixed points of the gauge coupling and scalar couplings incompatible. We develop and check an algebraic approach to the one-loop renormalisation group which we find to be characterised by a non-associative algebra of marginal couplings. In the large $N$ limit, the resulting RG flows typically suffer from strong coupling in both the ultraviolet and the infrared. Only for $M\ge 406$ fine-tuned solutions exist which are weakly coupled in the infrared.",2303.13884v1 2023-03-26,Strong lateral exchange coupling and current-induced switching in single-layer ferrimagnetic films with patterned compensation temperature,"Strong, adjustable magnetic couplings are of great importance to all devices based on magnetic materials. Controlling the coupling between adjacent regions of a single magnetic layer, however, is challenging. In this work, we demonstrate strong exchange-based coupling between arbitrarily shaped regions of a single ferrimagnetic layer. This is achieved by spatially patterning the compensation temperature of the ferrimagnet by either oxidation or He+ irradiation. The coupling originates at the lateral interface between regions with different compensation temperature and scales inversely with their width. We show that this coupling generates large lateral exchange coupling fields and we demonstrate its application to control the switching of magnetically compensated dots with an electric current.",2303.14809v1 2023-04-10,Raman-probing the local ultrastrong coupling of vibrational plasmon-polaritons on metallic gratings,"Strong coupling of molecular vibrations with light creates polariton states, enabling control over many optical and chemical properties. However, the near-field signatures of strong coupling are difficult to map as most cavities are closed systems. Surface-enhanced Raman microscopy of open metallic gratings under vibrational strong coupling enables the observation of spatial polariton localization in the grating near-field, without the need for scanning probe microscopies. The lower polariton is localized at the grating slots, displays a strongly asymmetric lineshape, and gives greater plasmon-vibration coupling strength than measured in the far-field. Within these slots, the local field strength pushes the system into the ultrastrong coupling regime. Models of strong coupling which explicitly include the spatial distribution of emitters can account for these effects. Such gratings form a new system for exploring the rich physics of polaritons and the interplay between their near- and far-field properties through polariton-enhanced Raman scattering (PERS).",2304.04834v1 2023-05-02,Localization and spectrum of quasiparticles in a disordered fermionic Dicke model,"We study a fermionic two-band model with the interband transition resonantly coupled to a cavity. This model was recently proposed to explain cavity-enhanced charge transport, but a thorough characterization of the closed system, in particular localization of various excitations, is lacking. In this work, using exact diagonalization, we characterize the system by its spectrum under various filling factors and variable disorder. As in the Dicke model, the effective light-matter coupling scales with the square root of the system size. However, there is an additional factor that decreases with increasing doping density. The transition from the weak-coupling regime to the strong-coupling regime occurs when the effective light-matter coupling is larger than the electronic bandwidth. Here, the formation of exciton-polaritons is accompanied by the formation of bound excitons. Photon spectral functions exhibit significant weights on the in-gap states between the polaritons, even without disorder. Finally, while the localization of electron-hole excitations in a disordered system is lifted by strong coupling, the same is not true for free charges, which remain localized at strong and even ultrastrong coupling. Based on this finding, we discuss scenarios for charge transport.",2305.01664v1 2023-05-07,Quantum synchronization and entanglement of indirectly coupled mechanical oscillators in cavity optomechanics: a numerical study,"It is often conjectured that quantum synchronisation and entanglement are two independent properties which two coupled quantum systems may not exhibit at the same time. However, as both these properties can be understood in terms of the second order moments of a set of conjugate quadratures, there may exist specific conditions for simultaneous existence of entanglement and quantum synchronization. Here we present a theoretical scheme to achieve the same between two mechanical oscillators, which are indirectly coupled with each other via a coupling between two cavities. We show that in the presence of the cavity-oscillator coupling, quadratically varying with their displacements, these oscillators can be synchronized in the quantum sense and entangled as well, at times much longer than the decay time-scale of the cavity modes. Precisely speaking, we show that in the presence of quadratic coupling, entanglement criterion and quantum synchronization measure are simultaneously satisfied in steady state. This behaviour can be observed for a range of quadratic coupling, temperature, and frequency difference of the two oscillators.",2305.04197v1 2023-06-12,Constraints on the non-minimally coupled Witten-O'Raifeartaigh inflation,"We investigate the impact of a non-minimal coupling of the scalar field with gravity in inflationary models, where a small coupling is allowed. As a concrete example, we consider the Witten-O'Raifeartaigh model, where, in line with other models, the presence of a coupling strength $\xi$ can recover concordance of the inflationary parameters with cosmic microwave background (CMB) constraints, provided by the Planck collaboration. We go beyond the slow-roll regime and investigate the impact in the description of CMB anisotropies by performing a statistical analysis of the model with the most recent Planck + Baryon Acoustic Oscillations (BAO) data to seek for any indication of a non-zero coupling by data within the model. We find that not only the presence of a non-minimal coupling is seen, but the model has a slight statistical preference when compared with the standard $\Lambda$CDM one. We also discuss the results on the minimally-coupled model, which in general, favours the simple setting where the associated mass scale is equal to the reduced Planck mass $M_p$ while being, in general, disfavored concerning the standard model.",2306.07260v1 2023-06-20,Search for the anomalous quartic gauge couplings through $Zγ$ production at $e^{-} e^{+}$ colliders,"Spontaneous breaking of the $SU(2)_{L}\times U(1)_{Y}$ electroweak symmetry of the Standard Model (SM) sets the constraints on triple gauge couplings and quartic gauge couplings. Therefore, the measurement of multiboson production in $e^{-} e^{+}$ collisions allows us to directly examine the SM predictions and perform indirect investigations of new physics beyond the SM. In this paper, we concentrate the process $e^{-} e^{+} \to e^{-} Z\gamma e^{+}$ with $Z$ boson decaying to neutrinos to investigate the anomalous quartic gauge couplings using the effective Lagrangian approach at the Compact Linear Collider (CLIC). We obtain the sensitivities on the anomalous $ f_ {Ti}/\Lambda^4$ ($i=0,2,5,6,7,8,9$) couplings taking into account the systematic uncertainties of $3, 5 \%$ at $95\%$ Confidence Level for the CLIC with $\sqrt{s}=3$ TeV. Our results show that the sensitivities on some anomalous couplings without systematic errors are up to two orders of magnitude better than the current experimental limits. Considering a realistic systematic uncertainty such as $5 \%$ from possible experimental sources, the sensitivity of all anomalous quartic couplings gets worse by about $10\%$ compared to those without systematic uncertainty for the CLIC.",2306.11894v1 2023-07-01,Integrable coupled bosonic massive Thirring model and its nonlocal reductions,"A coupled bosonic massive Thirring model (BMTM), involving an interaction between the two independent spinors, is introduced and shown to be integrable. By incorporating suitable reductions between the field components of the coupled BMTM, five novel integrable models with various type of nonlocal interactions are constructed. Lax pairs satisfying the zero curvature condition are obtained for the coupled BMTM and for each of the related nonlocal models. An infinite number of conserved quantities are derived for each of these models which confirms the integrability of the systems. It is shown that the coupled BMTM respects important symmetries of the original BMTM such as parity, time reversal, global $U(1)$-gauge and the proper Lorentz transformations. Similarly, all the nonlocal models obtained from the coupled BMTM remain invariant under combined operation of parity and time reversal transformations. However, it is found that only one of the nonlocal models is invariant under proper Lorentz transformation and two other models are invariant under global $U(1)$-gauge transformation. By using ultralocal Poisson bracket relations among the elements of the Lax operator, it is shown that the coupled BMTM and one of the nonlocal models are completely integrable in the Liouville sense.",2307.00351v1 2023-07-24,Dynamics of oscillator populations globally coupled with distributed phase shifts,"We consider a population of globally coupled oscillators in which phase shifts in the coupling are random. We show that in the maximally disordered case, where the pairwise shifts are i.i.d. random variables, the dynamics of a large population reduces to one without randomness in the shifts but with an effective coupling function, which is a convolution of the original coupling function with the distribution of the phase shifts. This result is valid for noisy oscillators and/or in presence of a distribution of natural frequencies. We argue also, using the property of global asymptotic stability, that this reduction is valid in a partially disordered case, where random phase shifts are attributed to the forced units only. However, the reduction to an effective coupling in the partially disordered noise-free situation may fail if the coupling function is complex enough to ensure the multistability of locked states.",2307.12563v2 2023-07-28,Strong tunable coupling between two distant superconducting spin qubits,"Superconducting (or Andreev) spin qubits have recently emerged as an alternative qubit platform with realizations in semiconductor-superconductor hybrid nanowires. In these qubits, the spin degree of freedom is intrinsically coupled to the supercurrent across a Josephson junction via the spin-orbit interaction, which facilitates fast, high-fidelity spin readout using circuit quantum electrodynamics techniques. Moreover, this spin-supercurrent coupling has been predicted to facilitate inductive multi-qubit coupling. In this work, we demonstrate a strong supercurrent-mediated coupling between two distant Andreev spin qubits. This qubit-qubit interaction is of the longitudinal type and we show that it is both gate- and flux-tunable up to a coupling strength of 178 MHz. Finally, we find that the coupling can be switched off in-situ using a magnetic flux. Our results demonstrate that integrating microscopic spin states into a superconducting qubit architecture can combine the advantages of both semiconductors and superconducting circuits and pave the way to fast two-qubit gates between remote spins.",2307.15654v1 2023-08-10,Practical guide to the statistical mechanics of molecular polaritons,"A theoretical approach aimed at the quantum statistical mechanics of a molecular ensemble coupled to a lossless cavity mode is presented. A canonical ensemble is considered and an approximate formula is devised for the Helmholtz free energy correction due to cavity-molecule coupling, which enables the derivation of experimentally measurable thermodynamic quantities. The frequency of the cavity mode is assumed to lie in the infrared range. Therefore, the cavity couples to molecular vibrations and our treatment is restricted to the electronic ground state of the molecule. The method is tested for an analytically solvable model system of one-dimensional harmonic oscillators coupled to the cavity. The performance of the approximation and its range of validity are discussed in detail. It is shown that the leading-order correction to the Helmholtz free energy is proportional to the square of the collective coupling strength. We also demonstrate that the cavity mode does not have a significant impact on the thermodynamic properties of the system in the collective ultrastrong coupling regime (the collective coupling strength is comparable to the frequency of the cavity mode).",2308.05610v2 2023-08-23,Ultrastrong photon-photon coupling,"Recent studies have shown that matter can ultrastrongly couple with the quantum vacuum field inside a photonic cavity, producing a nonclassical ground state that contains a finite number of photons. Here, we present a novel matter-vacuum hybrid in a multimode photonic cavity whose ground state contains ultrastrongly coupled photons. This unique photon-photon coupling was realized in a three-dimensional terahertz photonic-crystal cavity, where two adjacent cavity modes mixed together through simultaneous coupling with the cyclotron resonance of a two-dimensional electron gas with a coupling strength exceeding the intermode frequency. Our microscopic theory successfully explains the salient features of our experimental observations, highlighting the spatial overlap of mode profiles as a key enabler of photon-photon ultrastrong coupling. Our findings provide guidelines for harnessing photon-photon correlations for furthering the physics of vacuum-dressed matter as well as for developing vacuum-enabled quantum technology.",2308.12427v2 2023-08-24,The disordered Dicke model,"We introduce and study the disordered Dicke model in which the spin-boson couplings are drawn from a random distribution with some finite width. Regarding the quantum phase transition we show that when the standard deviation $\sigma$ of the coupling strength gradually increases, the critical value of the mean coupling strength $\mu$ gradually decreases and after a certain $\sigma$ there is no quantum phase transition at all; the system always lies in the super-radiant phase. We derive an approximate expression for the quantum phase transition in the presence of disorder in terms of $\mu$ and $\sigma$, which we numerically verify. Studying the thermal phase transition in the disordered Dicke model, we obtain an analytical expression for the critical temperature in terms of the mean and standard deviation of the coupling strength. We observe that even when the mean of the coupling strength is zero, there is a finite temperature transition if the standard deviation of the coupling is sufficiently high. Disordered couplings in the Dicke model will exist in quantum dot superlattices, and we also sketch how they can be engineered and controlled with ultracold atoms or molecules in a cavity.",2308.12996v1 2023-09-06,Terahertz-Band Direction Finding With Beam-Split and Mutual Coupling Calibration,"Terahertz (THz) band is currently envisioned as the key building block to achieving the future sixth generation (6G) wireless systems. The ultra-wide bandwidth and very narrow beamwidth of THz systems offer the next order of magnitude in user densities and multi-functional behavior. However, wide bandwidth results in a frequency-dependent beampattern causing the beams generated at different subcarriers split and point to different directions. Furthermore, mutual coupling degrades the system's performance. This paper studies the compensation of both beam-split and mutual coupling for direction-of-arrival (DoA) estimation by modeling the beam-split and mutual coupling as an array imperfection. We propose a subspace-based approach using multiple signal classification with CalibRated for bEAam-split and Mutual coupling (CREAM-MUSIC) algorithm for this purpose. Via numerical simulations, we show the proposed CREAM-MUSIC approach accurately estimates the DoAs in the presence of beam-split and mutual coupling.",2309.03195v2 2023-09-21,Designing Loving-Kindness Meditation in Virtual Reality for Long-Distance Romantic Relationships,"Loving-kindness meditation (LKM) is used in clinical psychology for couples' relationship therapy, but physical isolation can make the relationship more strained and inaccessible to LKM. Virtual reality (VR) can provide immersive LKM activities for long-distance couples. However, no suitable commercial VR applications for couples exist to engage in LKM activities of long-distance. This paper organized a series of workshops with couples to build a prototype of a couple-preferred LKM app. Through analysis of participants' design works and semi-structured interviews, we derived design considerations for such VR apps and created a prototype for couples to experience. We conducted a study with couples to understand their experiences of performing LKM using the VR prototype and a traditional video conferencing tool. Results show that LKM session utilizing both tools has a positive effect on the intimate relationship and the VR prototype is a more preferable tool for long-term use. We believe our experience can inform future researchers.",2309.11816v1 2023-10-02,Hybrid light-matter states in topological superconductors coupled to cavity photons,"We consider a one-dimensional topological superconductor hosting Majorana bound states at its ends coupled to a single mode cavity. In the strong light-matter coupling regime, electronic and photonic degrees of freedom hybridize resulting in the formation of polaritons. We find the polariton spectrum by calculating the cavity photon spectral function of the coupled electron-photon system. In the topological phase the lower in energy polariton modes are formed by the bulk-Majorana transitions coupled to cavity photons and are also sensitive to the Majorana parity. In the trivial phase the lower polariton modes emerge due to the coupling of the bulk-bulk transitions across the gap to photons. Our work demonstrates the formation of polaritons in topological superconductors coupled to photons that contain information on the features of the Majorana bound states.",2310.01296v2 2023-10-27,First-principles molecular quantum electrodynamics theory at all coupling strengths,"The ever-growing intersection of quantum electrodynamics (QED) and molecular processes has shown remarkable and unanticipated advancements in altering molecular properties and reactivity by exploiting light-matter couplings. In recent years, multiple ab initio methods have been developed to compute the eigenstates of molecular systems strongly coupled to cavities, ranging from the mean-field to quantum many-body methods. The quantum many-body methods, such as coupled-cluster theories, usually rely on the quality of mean-field reference wavefunctions. Hence, developing efficient and physically reliable mean-filed approaches for molecular quantum electrodynamics problems is crucial. The current widely used methods, such as QED Hartree-Fock and the self-consistent counterpart, are limited to specific coupling regimes. In this work, we developed a variational transformation-based molecular quantum electrodynamics mean-field method, namely VT-QEDHF, for light-matter interaction at arbitrary coupling strength. The numerical benchmark demonstrates that the VT-QEDHF method naturally connects both QEDHF and self-consistent QEDHF methods at the two limits, showcasing the advantage of VT-QEHDF across all coupling strengths.",2310.18228v2 2023-10-29,Exploring the impact of vibrational cavity coupling strength on ultrafast CN + $c$-C$_6$H$_{12}$ reaction dynamics,"Molecular polaritons, hybrid light-matter states resulting from strong cavity coupling of optical transitions, may provide a new route to guide chemical reactions. However, demonstrations of cavity-modified reactivity in clean benchmark systems are still needed to clarify the mechanisms and scope of polariton chemistry. Here, we use transient absorption to observe the ultrafast dynamics of CN radicals interacting with a cyclohexane ($c$-C$_6$H$_{12}$) and chloroform (CHCl$_3$) solvent mixture under vibrational strong coupling of the brightest C$-$H stretching mode of $c$-C$_6$H$_{12}$. By modulating the $c$-C$_6$H$_{12}$:CHCl$_3$ ratio, we explore how solvent complexation and hydrogen (H)-abstraction processes proceed under collective cavity coupling strengths ranging from 55$-$85 cm$^{-1}$. Reaction rates remain unchanged for all extracavity, on resonance, and off-resonance cavity coupling conditions, regardless of coupling strength. These results suggest that insufficient vibrational cavity coupling strength may not be the determining factor for the negligible cavity effects observed previously in H-abstraction reactions of CN with CHCl$_3$.",2310.19133v2 2023-11-05,Analytic solution of Balitsky-Kovchegov equation with running coupling constant using homogeneous balance method,"In this study, we employ the homogeneous balance method to obtain an analytical solution to the Balitsky-Kovchegov equation with running coupling. We utilize two distinct prescriptions of the running coupling scale, namely the saturation scale dependent running coupling and the dipole momentum dependent running coupling. By fitting the proton structure function experimental data, we determine the free parameters in the analytical solution. The resulting $\chi^{2}/d.o.f$ values are determined to be $1.07$ and $1.43$, respectively. With these definitive solutions, we are able to predict exclusive $J/\psi$ production, and demonstrate that analytical solutions with running coupling are in excellent agreement with $J/\psi$ differential and total cross section. Furthermore, our numerical results indicate that the analytical solution of the BK equation with running coupling can provide a reliable description for both the proton structure function and exclusive vector meson production.",2311.02672v2 2023-11-13,Fibroblast mediated dynamics in diffusively uncoupled myocytes -- a simulation study using 2-cell motifs,"In healthy hearts myocytes are typically coupled to nearest neighbours through gap junctions. Under pathological conditions such as fibrosis, or in scar tissue, or across ablation lines myocytes can uncouple from their neighbours. Electrical conduction may still occur via fibroblasts that not only couple proximal myocytes but can also couple otherwise unconnected regions. We hypothesise that such coupling can alter conduction between myocytes via introduction of delays or by initiation of premature stimuli that can potentially result in reentry or conduction blocks. To test this hypothesis we have developed several $2$-cell motifs and investigated the effect of fibroblast mediated electrical coupling between uncoupled myocytes. We have identified various regimes of myocyte behaviour that depend on the strength of gap-junctional conductance, connection topology, and parameters of the myocyte and fibroblast models. These motifs are useful in developing a mechanistic understanding of long-distance coupling on myocyte dynamics and enable the characterisation of interaction between different features such as myocyte and fibroblast properties, coupling strengths and pacing period. They are computationally inexpensive and allow for incorporation of spatial effects such as conduction velocity. They provide a framework for constructing scar tissue boundaries and enable linking of cellular level interactions with scar induced arrhythmia.",2311.07313v1 2023-11-20,Sensitivity of polarizations and spin correlations of Z boson to anomalous neutral triple gauge couplings at lepton collider with polarized beams,"We investigate the effects of anomalous neutral triple gauge couplings in $ZZ$ and $Z\gamma$ production processes, followed by the leptonic decay of the $Z$ boson, at a lepton collider with center-of-mass energy $\sqrt{s}=250$~GeV and polarized beams. We use an effective Lagrangian formalism to parameterize the anomalous couplings in terms of dimension-8 operators $c_{\widetilde{B}W}$, $c_{BW}$, $c_{WW}$, and $c_{BB}$, and study the sensitivity of observables such as cross~section, polarization, and spin correlation as functions of these couplings. We perform a Bayesian statistical analysis using Markov Chain Monte Carlo methods to determine simultaneous limits on the anomalous couplings, taking into account various luminosities $\mathcal{L} \in \{0.1~\text{ab}^{-1}, 0.3~\text{ab}^{-1}, 1~\text{ab}^{-1}, 3~\text{ab}^{-1}, 10~\text{ab}^{-1}\}$ and systematic uncertainties. We find that polarization and spin correlation observables significantly enhance the sensitivity to anomalous couplings, providing stringent constraints on these couplings.",2311.12170v2 2023-11-24,Revisiting the Physics of Strong Coupling on Dusty Plasma System,"Dusty plasma can exist in a wide range, from the laboratory to Saturn's rings. The coupling parameter plays a very important role in diagnosing dusty plasma. There are two ways to deal analytically with the effect of coupling in plasma. First, where the coupling parameter is represented with the help of viscoelastic relaxation time, and the second where the electrostatic temperature represents the coupling parameters, in this work, we have used both techniques in a strongly coupled four-component plasma in which we have considered the dynamics of negatively charged dust grains and q- nonextensive distribution for electrons, ions, and positrons. The main focus of this particular work is to find out the operational regions and validity of these two techniques. The result of this paper will give future researchers an idea of how coupling would be encountered in a dusty plasma system.",2311.14507v2 2023-12-09,Intrinsic Grain Boundary Shear Coupling Tensor,"Grain boundary (GB) migration stands as a linchpin process governing microstructural evolution in polycrystalline materials. Over the past decade, the concept of shear coupling, quantified through the shear coupling factor, has transformed our understanding and driven the development of theoretical frameworks for unifying GB behaviors. In this study, we unveil a critical shortcoming in the definition of shear coupling factor and introduce a mathematically redefined descriptor - shear coupling strength - along with its corresponding tensor. This innovation accurately characterizes intrinsic shear coupling properties across diverse GBs and reveals complex dynamics within the GB mobility tensor, with a mathematical proof affirming its symmetry that is assumed in previous studies. Additionally, an efficient methodology has been developed for streamlined extraction of both shear coupling and GB mobility tensors from atomistic simulations. This advancement holds the potential to sample GB behavior across extensive datasets, significantly enhancing our ability to predict structure-property relationships within the expansive 5-parameter space of GBs.",2312.05702v1 2023-12-14,"Tripartite Phonon-Magnon-Plasmon Coupling, Parametric Amplification, and Formation of a Phonon-Magnon-Plasmon Polariton in a Two-Dimensional Periodic Array of Magnetostrictive/Plasmonic Bilayered Nanodots","Coupling between spin waves (SWs) and other types of waves in nanostructured magnetic media has garnered increased attention in recent years because of the rich physics and the potential to produce disruptive technologies. Among this family of intriguing phenomena, we recently reported a new one: coupling between SWs and hybridized phonon-plasmon waves, resulting in tripartite coupling of magnons, phonons, and plasmons. Here, this acousto-plasmo-magnonic phenomenon is studied in a two-dimensional periodic array of bilayered [Co/Al] nanodots on a silicon substrate, where the Co is a magnetostrictive constituent responsive to magneto-elastic coupling and the Al acts as a source of surface plasmons. Time-resolved magneto-optical-Kerr-effect microscopy revealed parametric amplification and strong coupling between two spin wave modes mediated by a hybrid phonon-plasmon wave. The strong coupling forms a new quasi-particle: the phonon-plasmonmagnon polariton.",2312.09343v1 2023-12-19,Effects of cavity-mediated processes on the polarization entanglement of photon pairs emitted from quantum dots,"Semiconductor quantum dots are among the best sources of on-demand entangled photon pairs. The degree of entanglement, however, is generally limited by the fine structure splitting of exciton states. In this paper, we theoretically investigate the generation of polarisation-entangled photon pairs under two-photon excitation and cavity-assisted two-photon emission, both in the weak and strong cavity coupling regimes. We demonstrate and clarify that cavity coupling together with an excitation pulse reduces the degree of entanglement in three different ways. Firstly, in a strong coupling regime, cavity introduces the unequal ac-Stark shift of horizontally and vertically polarised exciton states, which results in the effective splitting of exciton states. Secondly, it induces the cross-coupling between the exciton states even in the weak coupling regime, causing the creation of unfavorable two-photon states. Finally, higher excited states of the cavity modes also contribute to the reduction of entanglement. Therefore, in the setting considered here, cavity coupling, which is generally required for the efficient collection of emitted photons, degrades the entanglement both in weak and strong coupling regimes.",2312.12054v2 2024-01-10,Migdal-Eliashberg superconductivity in a Kondo lattice,"We apply the Migdal-Eliashberg theory of superconductivity to heavy-fermion and mixed valence materials. Specifically, we extend the Anderson lattice model to a case when there exists a strong coupling between itinerant electrons and lattice vibrations. Using the saddle-point approximation, we derive a set of coupled nonlinear equations which describe competition between the crossover to a heavy-fermion or mixed-valence regimes and conventional superconductivity. We find that superconductivity at strong coupling emerges on par with the development of the many-body coherence in a Kondo lattice. Superconductivity is gradually suppressed with the onset of the Kondo screening and for strong electron-phonon coupling the Kondo screening exhibits a characteristic re-entrant behavior. Even though for both weak and strong coupling limits the suppression of superconductivity is weaker in the mixed-valence regime compared to the local moment one, superconducting critical temperature still remains nonzero. In the weak coupling limit the onset of the many body coherence develops gradually, in the strong coupling limit it emerges abruptly in the mixed valence regime while in the local moment regime the $f$-electrons remain effectively decoupled from the conduction electrons. Possibility of experimental realization of these effects in Ce-based compounds is also discussed.",2401.05486v1 2024-01-19,Photonic Supercoupling in Silicon Topological Waveguides,"Electromagnetic wave coupling between photonic systems relies on the evanescent field typically confined within a single wavelength. Extending evanescent coupling distance requires low refractive index contrast and perfect momentum matching for achieving a large coupling ratio. Here, we report the discovery of photonic supercoupling in a topological valley Hall pair of waveguides, showing a substantial improvement in coupling efficiency across multiple wavelengths. Experimentally, we realize ultra-high coupling ratios between waveguides through valley-conserved vortex flow of electromagnetic energy, attaining 95% coupling efficiency for separations of up to three wavelengths. This demonstration of photonic supercoupling in topological systems significantly extends the coupling distance between on-chip waveguides and components, paving the path for the development of supercoupled photonic integrated devices, optical sensing, and telecommunications.",2401.10508v1 2024-02-05,Controlling magnon-photon coupling in a planar geometry,"The tunability of magnons enables their interaction with various other quantum excitations, including photons, paving the route for novel hybrid quantum systems. Here, we study magnon-photon coupling using a high-quality factor split-ring resonator and single-crystal yttrium iron garnet (YIG) spheres at room temperature. We investigate the dependence of the coupling strength on the size of the sphere and find that the coupling is stronger for spheres with a larger diameter as predicted by theory. Furthermore, we demonstrate strong magnon-photon coupling by varying the position of the YIG sphere within the resonator. Our experimental results reveal the expected correlation between the coupling strength and the rf magnetic field. These findings demonstrate the control of coherent magnon-photon coupling through the theoretically predicted square-root dependence on the spin density in the ferromagnetic medium and the magnetic dipolar interaction in a planar resonator.",2402.03071v1 2024-02-23,Controlling Markovianity with Chiral Giant Atoms,"A recent experimental work has demonstrated the chiral behavior of a giant artificial atom coupled to a microwave photonic waveguide. This is made possible through the engineering of complex phases in the two non-local couplings of the artificial atom to the waveguide. When the phase difference between the couplings and the accumulated optical phase between the coupling points are judiciously tuned, maximal chirality is achieved. In parell, giant atoms coupled to a waveguide are paradigmatic setups to observe non-Markovian dynamics due to self-interference effects. Here we report on a novel effect in giant atom physics that solely depends on the complex phases of the couplings. We show that, by adjusting the couplings' phases, a giant atom can, counterintuitively, enter the Markovian regime irrespectively of any inherent time delay.",2402.15556v1 2024-02-26,Long-range molecular energy transfer mediated by strong coupling to plasmonic topological edge states,"Strong coupling between light and molecular matter is currently attracting interest both in chemistry and physics, in the fast-growing field of molecular polaritonics. The large near-field enhancement of the electric field of plasmonic surfaces and their high tunability make arrays of metallic nanoparticles an interesting platform to achieve and control strong coupling. Two dimensional plasmonic arrays with several nanoparticles per unit cell and crystalline symmetries can host topological edge and corner states. Here we explore the coupling of molecular materials to these edge states using a coupled-dipole framework including long-range interactions. We study both the weak and strong coupling regimes and demonstrate that coupling to topological edge states can be employed to enhance highly-directional long-range energy transfer between molecules.",2402.16666v1 2024-02-27,"Flavor-Violating ALPs, Electron g-2, and the Electron-Ion Collider","We revisit the possibility that light axion-like particles (ALPs) with lepton flavor violating couplings could give significant contributions to the electron's anomalous magnetic moment $g_e-2$. Unlike flavor diagonal lepton-ALP couplings, which are exclusively axial, lepton flavor violating couplings can have arbitrary chirality. Focusing on the $e$-$\tau$ ALP coupling, we find that the size of the contribution to $g_e-2$ depends strongly on the chirality of the coupling. A significant part of the parameter space for which such a coupling can explain experimental anomalies in $g_e-2$ can be probed at the Electron-Ion Collider, which is uniquely sensitive to the chirality of the coupling using the polarization of the electron beam.",2402.17821v1 2024-03-18,Effect of photoinduced screening on the spectroscopic signature of exciton-phonon coupling,"The light-mediated interaction of fermionic and bosonic excitations governs the optoelectronic properties of condensed matter systems. In photoexcited semiconductors, the coupling of electron-hole pairs (excitons) to coherent optical phonons enables a modulation of the excitonic resonance that is phase-locked to the frequency of the coupled vibrational mode. Moreover, due to the Coulombic nature of excitons, their dynamics are sensitive to transient changes in the screening by the photoexcited carriers. Interestingly, the effect of photoinduced screening on the transient optical signal originating from the exciton dynamics coupled to phonons is not yet established. By means of broadband transient reflectance spectroscopy, we disclose how exciton-phonon coupling manifests in either presence or absence of dynamical screening in a layered semiconductor. Further, we unveil the promoting role of photoinduced screening on these exciton-phonon coupled dynamics as opposed to the case in which the unscreened exciton-exciton repulsion likely dominates the nonequilibrium optical response. These findings set a protocol to look at an excitonic resonance and its fundamental many-body interactions on the ultrafast timescale, and provide new perspectives on the access to nonequilibrium coupled dynamics.",2403.11884v1 2003-09-24,N-body simulations for coupled dark energy: halo mass function and density profiles,"We present the results of a series of N-body simulations in cosmologies where dark matter (DM) is coupled to dark energy (DE), so easing the cosmic coincidence problem. The dark-dark coupling introduces two novel effects in N-body dynamics: (i) DM particle masses vary with time; (ii) gravity between DM particles is ruled by a constant $G^{*}$, greater than Newton's constant $G$, holding in other 2-body interactions. As a consequence, baryons and DM particle distributions develop a large scale bias. Here we investigate DE models with Ratra-Peebles (RP) potentials; the dark-dark coupling is set in a parametric range compatible with observations, for as concern background and linear perturbation properties. We study the halo mass function, the halo density profile and the behavior of the non-linear bias. We find that non-linear dynamics puts additional constraints to the coupling parameter. They mostly arise from density profiles, that we find to yield higher concentrations, in coupled RP models, with respect to (uncoupled) dynamical DE cosmologies. Such enhancement, although being a strong effect in some coupling parameter range, is just a minor change for smaller but significant values of the coupling parameter. With these further restrictions, coupled DE models with RP potential are consistent with non-linear observables.",0309671v2 2001-08-01,The Rashba Effect within the Coherent Scattering Formalism,"The influence of spin-orbit coupling in two-dimensional systems is investigated within the framework of the Landauer-Buettiker coherent scattering formalism. This formalism usually deals with spin-independent stationary states and, therefore, it does not include a spin-orbit contribution to the current. In this article, we will rederive the coherent scattering formalism, accounting for the changes brought about by the spin-orbit coupling. After a short review of the features of spin-orbit coupling in two-dimensional electron gases, we define the creation/annihilaton operators in the stationary states of the spin-orbit coupling Hamiltonian and use them to calculate the current operator within the Landauer-Buettiker formalism. The current is expressed as it is in the standard spin-independent case, but with the spin label replaced by a new label which we call the spin-orbit coupling label. The spin-orbit coupling effects can then be represented in a scattering matrix which relates the spin-orbit coupling stationary states in different leads. This scattering matrix is calculated in the case of a four-port beamsplitter, and it is shown to mix states with different spin-orbit coupling labels in a manner that depends on the angle between the leads. The formalism is then used to calculate the effect of spin-orbit coupling on the current and noise in two examples of electron collision.",0108021v1 2006-06-22,"Spin-orbit coupling in curved graphene, fullerenes, nanotubes, and nanotube caps","A continuum model for the effective spin orbit interaction in graphene is derived from a tight-binding model which includes the $\pi$ and $\sigma$ bands. We analyze the combined effects of the intra-atomic spin-orbit coupling, curvature, and applied electric field, using perturbation theory. We recover the effective spin-orbit Hamiltonian derived recently from group theoretical arguments by Kane and Mele. We find, for flat graphene, that the intrinsic spin-orbit coupling $\Hi \propto \Delta^ 2$ and the Rashba coupling due to a perpendicular electric field ${\cal E}$, $\Delta_{\cal E} \propto \Delta$, where $\Delta$ is the intra-atomic spin-orbit coupling constant for carbon. Moreover we show that local curvature of the graphene sheet induces an extra spin-orbit coupling term $\Delta_{\rm curv} \propto \Delta$. For the values of $\cal E$ and curvature profile reported in actual samples of graphene, we find that $\Hi < \Delta_{\cal E} \lesssim \Delta_{\rm curv}$. The effect of spin-orbit coupling on derived materials of graphene, like fullerenes, nanotubes, and nanotube caps, is also studied. For fullerenes, only $\Hi$ is important. Both for nanotubes and nanotube caps $\Delta_{\rm curv}$ is in the order of a few Kelvins. We reproduce the known appearance of a gap and spin-splitting in the energy spectrum of nanotubes due to the spin-orbit coupling. For nanotube caps, spin-orbit coupling causes spin-splitting of the localized states at the cap, which could allow spin-dependent field-effect emission.",0606580v3 1997-05-19,Inflaton Decay and Heavy Particle Production with Negative Coupling,"We study the decay of the inflaton in a renormalizable two scalar theory. Since the dynamics of the system is dominated by states with large occupation numbers which admit a semiclassical description, the decay can be studied by solving the classical equations of motion on the lattice. Of particular interest is the case when the cross-coupling between the inflaton and the second scalar field is negative, which is naturally allowed in many realistic models. While the inflaton decays via parametric resonance in the positive coupling case we find that for negative coupling there is a new mechanism of particle production which we call negative coupling instability. Due to this new mechanism the variances of the fields grow significantly larger before the production is shut off by the backreaction of the created particles. We also find that heavy particles are produced much more efficiently with negative coupling, which is of prime importance for GUT baryogenesis. Using a simple toy model for baryogenesis and the results of our lattice simulations we show that for natural values of the cross-coupling enough 10^{14}GeV bosons are created to produce a baryon to entropy ratio consistent with observation. For positive coupling the value of the cross-coupling required to produce such massive particles is unnaturally large. In addition to our numerical results we obtain analytical estimates for the maximum variances of the fields in an expanding universe for all cases of interest in our model.",9705357v1 2001-07-17,The Applicability of PQCD and NLO Power Corrections for Pion Form Factor,"In many years ago, Isgur and Llewellyn Smith addressed that PQCD is inapplicable to exclusive processes, such as the pion form factor.The main problem is that the asymptotic of PQCD is only about one fourth of the experimental value. We reexamine this PQCD deep problem. By including NLO power corrections to the pion form factor, we may arrive at a perturbative explanation for the data. The key realization is that we need to interprete that the strong interaction coupling constant involved in the PQCD result should be taken as an effective coupling constant under nonperturbative QCD vaccum. This implies that one can equally identify the relevant scale for the effective coupling constant as the factorization scale about 1 GeV. We also find that the average momentum fraction variable locates about 0.5, which is in favor of the asymptotic pion wave function. By employing photon-pion form factor with NLO power corrections to factorize out the nonperturbative effects involved in the effective coupling constant, we can extract an effective running coupling constant, which represents an effective coupling involving in the hard scattering subprocesses. The difference between the effective running coupling constant and the usual perturbative running coupling constant ($\Lambda_{QCD}=0.3$ GeV) is very small for $Q^2> 1 GeV^2$. The effective running coupling constant $\alpha_s/\pi$ is smaller than 0.2 for $Q^2>1 GeV^2$. This directly showes that PQCD is applicable to exclusive processes at energy $Q^2> 1 GeV^2$. In summary, with NLO power corrections, PQCD can completely explain the $Q^2$ spectrum of pion form factor.",0107192v3 2004-04-01,Anomalous gauge-boson couplings and the Higgs-boson mass,"We study anomalous gauge-boson couplings induced by a locally SU(2) x U(1) invariant effective Lagrangian containing ten operators of dimension six built from the boson fields of the Standard Model (SM) before spontaneous symmetry breaking (SSB). After SSB some operators lead to new three- and four-gauge-boson interactions, some contribute to the diagonal and off-diagonal kinetic terms of the gauge bosons and to the mass terms of the W and Z bosons. This requires a renormalisation of the gauge-boson fields, which, in turn, modifies the charged- and neutral-current interactions, although none of the additional operators contain fermion fields. Bounds on the anomalous couplings from electroweak precision measurements at LEP and SLD are correlated with the Higgs-boson mass m_H. Rather moderate values of anomalous couplings allow m_H up to 500 GeV. At a future linear collider the triple-gauge-boson couplings gammaWW and ZWW can be measured in the reaction e+e- --> WW. We compare three approaches to anomalous gauge-boson couplings: the form-factor approach, the addition of anomalous coupling terms to the SM Lagrangian after and, as outlined above, before SSB. The translation of the bounds on the couplings from one approach to another is not straightforward. We show that it can be done for the process e+e- --> WW by defining new effective ZWW couplings.",0404006v2 2007-01-18,Exact One Loop Running Couplings in the Standard Model,"Taking the dominant couplings in the standard model to be the quartic scalar coupling, the Yukawa coupling of the top quark, and the SU(3) gauge coupling, we consider their associated running couplings to one loop order. Despite the non-linear nature of the differential equations governing these functions, we show that they can be solved exactly. The nature of these solutions is discussed and their singularity structure is examined. It is shown that for a sufficiently small Higgs mass, the quartic scalar coupling decreases with increasing energy scale and becomes negative, indicative of vacuum instability. This behavior changes for a Higgs mass greater than 168 GeV, beyond which this couplant increases with increasing energy scales and becomes singular prior to the ultraviolet (UV) pole of the Yukawa coupling. Upper and lower bounds on the Higgs mass corresponding to new physics at the TeV scale are obtained and compare favourably with the numerical results of the one-loop and two-loop analyses with inclusion of electroweak couplings.",0701148v3 2005-05-30,Multiprocess parallel antithetic coupling for backward and forward Markov Chain Monte Carlo,"Antithetic coupling is a general stratification strategy for reducing Monte Carlo variance without increasing the simulation size. The use of the antithetic principle in the Monte Carlo literature typically employs two strata via antithetic quantile coupling. We demonstrate here that further stratification, obtained by using k>2 (e.g., k=3-10) antithetically coupled variates, can offer substantial additional gain in Monte Carlo efficiency, in terms of both variance and bias. The reason for reduced bias is that antithetically coupled chains can provide a more dispersed search of the state space than multiple independent chains. The emerging area of perfect simulation provides a perfect setting for implementing the k-process parallel antithetic coupling for MCMC because, without antithetic coupling, this class of methods delivers genuine independent draws. Furthermore, antithetic backward coupling provides a very convenient theoretical tool for investigating antithetic forward coupling. However, the generation of k>2 antithetic variates that are negatively associated, that is, they preserve negative correlation under monotone transformations, and extremely antithetic, that is, they are as negatively correlated as possible, is more complicated compared to the case with k=2. In this paper, we establish a theoretical framework for investigating such issues. Among the generating methods that we compare, Latin hypercube sampling and its iterative extension appear to be general-purpose choices, making another direct link between Monte Carlo and quasi Monte Carlo.",0505631v1 2003-07-28,Perturbation of coupling matrices and its effect on the synchronizability in arrays of coupled chaotic systems,"In a recent paper, wavelet analysis was used to perturb the coupling matrix in an array of identical chaotic systems in order to improve its synchronization. As the synchronization criterion is determined by the second smallest eigenvalue $\lambda_2$ of the coupling matrix, the problem is equivalent to studying how $\lambda_2$ of the coupling matrix changes with perturbation. In the aforementioned paper, a small percentage of the wavelet coefficients are modified. However, this result in a perturbed matrix where every element is modified and nonzero. The purpose of this paper is to present some results on the change of $\lambda_2$ due to perturbation. In particular, we show that as the number of systems $n \to \infty$, perturbations which only add local coupling will not change $\lambda_2$. On the other hand, we show that there exists perturbations which affect an arbitrarily small percentage of matrix elements, each of which is changed by an arbitrarily small amount and yet can make $\lambda_2$ arbitrarily large. These results give conditions on what the perturbation should be in order to improve the synchronizability in an array of coupled chaotic systems. This analysis allows us to prove and explain some of the synchronization phenomena observed in a recently studied network where random coupling are added to a locally connected array. Finally we classify various classes of coupling matrices such as small world networks and scale free networks according to their synchronizability in the limit.",0307052v1 2007-09-27,Evidence for a J/psi-ppbar Pauli Strong Coupling ?,"The couplings of charmonia and charmonium hybrids (generically Psi) to ppbar are of great interest in view of future plans to study these states using an antiproton storage ring at GSI. These low to moderate energy Psi-ppbar couplings are not well understood theoretically, and currently must be determined from experiment. In this letter we note that the two independent Dirac (gamma_mu) and Pauli (sigma_munu) ppbar couplings of the J/psi and psi' can be constrained by the angular distribution of e+e- -> (J/psi, psi') -> ppbar on resonance. A comparison of our theoretical results to recent unpolarized data allows estimates of the ppbar couplings; in the better determined J/psi case the data is inconsistent with a pure Dirac (gamma_mu) coupling, and can be explained by the presence of a sigma_munu term. This Pauli coupling may significantly affect the cross section of the PANDA process p pbar -> pi0 J/psi near threshold. There is a phase ambiguity that makes it impossible to uniquely determine the magnitudes and relative phase of the Dirac and Pauli couplings from the unpolarized angular distributions alone; we show in detail how this can be resolved through a study of the polarized reactions.",0709.4491v2 2007-11-05,Zero Lag Synchronization of Mutually Coupled Lasers in the Presence of Delays,"We consider a line of three mutually coupled lasers with time delays and study chaotic synchronization of the outer lasers. Two different systems are presented: optoelectronically coupled semiconductor lasers and optically coupled fiber lasers. While the dynamics of the two systems are very different, robust synchronization of end lasers is obtained in both cases over a range of parameters. Here, we present analysis and numerical simulation to explain some of the observed synchronization phenomena. First, we introduce the system of three coupled semiconductor lasers and discuss the onset of oscillations that occurs via a bifurcation as the coupling strength increases. Next, we analyze the synchronization of the end lasers by examining the dynamics transverse to synchronized state. We prove that chaotic synchronization of the outer semiconductor lasers will occur for sufficiently long delays, and we make a comparison to generalized synchronization in driven dissipative systems. It is shown that the stability of synchronous state (as indicated by negative Lyupunov exponents transverse to the synchronization manifold) depends on the internal dissipation of the outer lasers. We next present numerical simulations for three coupled fiber lasers, highlighting some of the differences between the semiconductor and fiber laser systems. Due to the large number of coupled modes in fiber lasers, this is a good system for investigating spatio-temporal chaos. Stochastic noise is included in the fiber laser model, and synchrony of the outer lasers is observed even at very small coupling strengths.",0711.0761v1 2008-04-02,Charged oscillator in a heat bath in the presence of a magnetic field & third law of thermodynamics,"The quantum thermodynamic behaviour of a charged oscillator in the presence of a magnetic field and coupled to a heat bath through different coupling schemes is obtained analytically. It is shown that finite dissipation substitutes the zero-coupling result of exponential decay of entropy by a power law behaviour at low temperature. For the coordinate-coordinates coupling scheme the low temperature explicit results for the case of Ohmic, exponentially correlated and more generalized heat bath models are derived. In all the above mentioned cases free energy and entropy vanish linearly with temperature ($T$) as $T\to 0$ in conformity with Nernst's theorem. It is seen that coordinate (velocity)-velocities (coordinates) coupling is much more beneficial than the coordinate-coordinates coupling to ensure third law of thermodynamics. The case of radiation heat bath shows $T^3$ decay behaviour for entropy as $T\to 0$. It is observed that at low temperature free energy and entropy decay faster for the velocity-velocities scheme than any other coupling schemes. This implies velocity-velocities coupling scheme is the most advantageous coupling scheme in restoring the third law of thermodynamics. It is shown that the low temperature thermodynamic functions are independent of magnetic field for all the above mentioned cases except the without dissipation case.",0804.0290v1 2010-01-22,Josephson effect through a multilevel dot near a singlet-triplet transition,"We investigate the Josephson effect through a two-level quantum dot with an exchange coupling between two dot electrons. We compute the superconducting phase relationship and construct the phase diagram in the superconducting gap--exchange coupling plane in the regime of the singlet-triplet transition driven by the exchange coupling. In our study two configurations for the dot-lead coupling are considered: one where effectively only one channel couples to the dot, and the other where the two dot orbitals have opposite parities. Perturbative analysis in the weak-coupling limit reveals that the system experiences transitions from 0 to $\pi$ (negative critical current) behavior, depending on the parity of the orbitals and the spin correlation between dot electrons. The strong coupling regime is tackled with the numerical renormalization group method, which first characterizes the Kondo correlations due to the dot-lead coupling and the exchange coupling in the absence of superconductivity. In the presence of superconductivity, many-body correlations such as two-stage Kondo effect compete with the superconductivity and the comparison between the gap and the relevant Kondo temperature scales allows to predict a rich variety of phase diagrams for the ground state of the system and for the Josephson current. Numerical calculations predicts that our system can exhibit Kondo-driven 0-$\pi$-0 or $\pi$-0-$\pi$ double transitions and, more interestingly, that if proper conditions are met a Kondo-assisted $\pi$-junction can arise, which is contrary to a common belief that the Kondo effect opens a resonant level and makes the 0-junction. Our predictions could be probed experimentally for a buckminster fullerene sandwiched between two superconductors.",1001.3914v1 2010-03-08,Coexistence of multi-photon processes and longitudinal couplings in superconducting flux qubits,"In contrast to natural atoms, the potential energies for superconducting flux qubit (SFQ) circuits can be artificially controlled. When the inversion symmetry of the potential energy is broken, we find that the multi-photon processes can coexist in the multi-level SFQ circuits. Moreover, there are not only transverse but also longitudinal couplings between the external magnetic fields and the SFQs when the inversion symmetry of potential energy is broken. The longitudinal coupling would induce some new phenomena in the SFQs. Here we will show how the longitudinal coupling can result in the coexistence of multi-photon processes in a two-level system formed by a SFQ circuit. We also show that the SFQs can become transparent to the transverse coupling fields when the longitudinal coupling fields satisfy the certain conditions. We further show that the quantum Zeno effect can also be induced by the longitudinal coupling in the SFQs. Finally we clarify why the longitudinal coupling can induce coexistence and disappearance of single- and two-photon processes for a driven SFQ, which is coupled to a single-mode quantized field.",1003.1671v3 2011-01-04,Hybridization effect in coupled metamaterials,"Although the invention of the metamaterials has stimulated the interest of many researchers and possesses many important applications, the basic design idea is very simple: composing effective media from many small structured elements and controlling its artificial EM properties. According to the effective-media model, the coupling interactions between the elements in metamaterials are somewhat ignored; therefore, the effective properties of metamaterials can be viewed as the ""averaged effect"" of the resonance property of the individual elements. However, the coupling interaction between elements should always exist when they are arranged into metamaterials. Sometimes, especially when the elements are very close, this coupling effect is not negligible and will have a substantial effect on the metamaterials' properties. In recent years, it has been shown that the interaction between resonance elements in metamaterials could lead to some novel phenomena and interesting applications that do not exist in conventional uncoupled metamaterials. In this paper, we will give a review of these recent developments in coupled metamaterials. For the ""meta-molecule"" composed of several identical resonators, the coupling between these units produces multiple discrete resonance modes due to hybridization. In the case of a ""meta-crystal"" comprising an infinite number of resonators, these multiple discrete resonances can be extended to form a continuous frequency band by strong coupling. This kind of broadband and tunable coupled metamaterial may have interesting applications. Many novel metamaterials and nanophotonic devices could be developed from coupled resonator systems in the future.",1101.0732v1 2011-07-22,Multicomponent coherently coupled and incoherently coupled solitons and their collisions,"We consider the integrable multicomponent coherently coupled nonlinear Schr\""odinger (CCNLS) equations describing simultaneous propagation of multiple fields in Kerr type nonlinear media. The correct bilinear equations of $m$-CCNLS equations are obtained by using a non-standard type of Hirota's bilinearization method and the more general bright one solitons with single hump and double hump profiles including special flat-top profiles are obtained. The solitons are classified as coherently coupled solitons and incoherently coupled solitons depending upon the presence and absence of coherent nonlinearity arising due to the existence of the co-propagating modes/components. Further, by obtaining the more general two-soliton solutions using this non-standard bilinearization approach we demonstrate that the collision among coherently coupled soliton and incoherently coupled soliton displays a non-trivial collision behaviour in which the former always undergoes energy switching accompanied by an amplitude dependent phase-shift and change in the relative separation distance, leaving the latter unaltered. But the collision between coherently coupled solitons alone is found to be standard elastic collision. Our study also reveals the important fact that the collision between incoherently coupled solitons arising in the $m$-CCNLS system with $m=2$ is always elastic, whereas for $m>2$ the collision becomes intricate and for this case the $m$-CCNLS system exhibits interesting energy sharing collision of solitons characterized by intensity redistribution, amplitude dependent phase-shift and change in relative separation distance which is similar to that of the multicomponent Manakov soliton collisions. This suggests that the $m$-CCNLS system can also be a suitable candidate for soliton collision based optical computing in addition to the Manakov system.",1107.4603v1 2012-06-14,Magnetic ordering phenomena of interacting quantum spin Hall models,"The two-dimensional Hubbard model defined for topological band structures exhibiting a quantum spin Hall effect poses fundamental challenges in terms of phenomenological characterization and microscopic classification. In the limit of infinite coupling U at half filling, the spin model Hamiltonians resulting from a strong coupling expansion show various forms of magnetic ordering phenomena depending on the underlying spin-orbit coupling terms. We investigate the infinite U limit of the Kane-Mele Hubbard model with z-axis intrinsic spin-orbit coupling as well as its generalization to a generically multi-directional spin orbit term which has been claimed to account for the physical scenario in monolayer Na2IrO3. We find that the axial spin symmetry which is kept in the former but broken in the latter has a fundamental impact on the magnetic phase diagram as we vary the spin orbit coupling strength. While the Kane-Mele spin model shows a continuous evolution from conventional honeycomb Neel to XY antiferromagnetism which avoids the frustration imposed by the increased spin-orbit coupling, the multi-directional spin-orbit term induces a commensurate to incommensurate transition at intermediate coupling strength, and yields a complex spiral state with a 72 site unit cell in the limit of infinite spin-orbit coupling. From our findings, we conjecture that in the case of broken axial spin symmetry there is a large propensity for an additional phase at sufficiently large spin-orbit coupling and intermediate U.",1206.3103v2 2012-08-31,Transfer/Breakup Channel Couplings in Sub-barrier Fusion Reactions,"With the recent availability of state-of-the-art radioactive ion beams, there has been a renew interest in the investigation of nuclear reactions with heavy ions near the Coulomb barrier. The role of inelastic and transfer channel couplings in fusion reactions induced by stable heavy ions can be revisited. Detailed Analysis of recent experimental fusion cross sections by using standard coupled-channel calculations is first discussed. Multi-neutron transfer effects are introduced in the fusion process below the Coulomb barrier by analyzing 32S+90,96Zr as benchmark reactions. The enhancement of fusion cross sections for 32S+96Zr is well reproduced at sub-barrier energies by NTFus code calculations including the coupling of the neutron-transfer channels following the Zagrebaev semi-classical model. Similar effects for 40Ca+90Zr and 40Ca+96Zr fusion excitation functions are found. The breakup coupling in both the elastic scattering and in the fusion process induced by weakly bound stable projectiles is also shown to be crucial. In the second part of this work, full coupled-channel calculations of the fusion excitation functions are performed by using the breakup coupling for the more neutron-rich reaction and for the more weakly bound projectiles. we clearly demonstrate that Continuum-Discretized Coupled-Channel calculations are capable to reproduce the fusion enhancement from the breakup coupling in 6Li+59Co.",1208.6435v2 2013-04-08,Cosmological effects of coupled dark matter,"Many models have been studied that contain more than one species of dark matter and some of these couple the Cold Dark Matter (CDM) to a light scalar field. In doing this we introduce additional long range forces, which in turn can significantly affect our estimates of cosmological parameters if not properly accounted for. It is, therefore, important to study these models and their resulting cosmological implications. We present a model in which a fraction of the total cold dark matter density is coupled to a scalar field. We study the background and perturbation evolution and calculate the resulting Cosmic Microwave Background anisotropy spectra. The greater the fraction of dark matter coupled to the scalar field and the stronger the coupling strength, the greater the deviation of the background evolution from LCDM. Previous work, with a single coupled dark matter species, has found an upper limit on the coupling strength of order O(0.1). We find that with a coupling of this magnitude more than half the dark matter can be coupled to a scalar field without producing any significant deviations from LCDM.",1304.2196v2 2013-07-01,Two-component Bose gases with one-body and two-body couplings,"We study the competition between one-body and two-body couplings in weakly-interacting two-component Bose gases, in particular as regards field correlations. We derive the meanfield theory for both ground state and low-energy pair excitations in the general case where both one-body and two-body couplings are position-dependent and the fluid is subjected to a state-dependent trapping potential. General formulas for phase and density correlations are also derived. Focusing on the case of homogeneous systems, we discuss the pair-excitation spectrum and the corresponding excitation modes, and use them to calculate correlation functions, including both quantum and thermal fluctuation terms. We show that the relative phase of the two components is imposed by that of the one-body coupling, while its fluctuations are determined by the modulus of the one-body coupling and by the two-body coupling. One-body coupling and repulsive two-body coupling cooperate to suppress relative-phase fluctuations, while attractive two-body coupling tends to enhance them. Further applications of the formalism presented here and extensions of our work are also discussed.",1307.0488v3 2013-07-10,Collective Effects in Linear Spectroscopy of Dipole-Coupled Molecular Arrays,"We present a consistent analysis of linear spectroscopy for arrays of nearest neighbor dipole-coupled two-level molecules that reveals distinct signatures of weak and strong coupling regimes separated for infinite size arrays by a quantum critical point. In the weak coupling regime, the ground state of the molecular array is disordered, but in the strong coupling regime it has (anti)ferroelectric ordering. We show that multiple molecular excitations (odd/even in weak/strong coupling regime) can be accessed directly from the ground state. We analyze the scaling of absorption and emission with system size and find that the oscillator strengths show enhanced superradiant behavior in both ordered and disordered phases. As the coupling increases, the single excitation oscillator strength rapidly exceeds the well known Heitler-London value. In the strong coupling regime we show the existence of a unique spectral transition with excitation energy that can be tuned by varying the system size and that asymptotically approaches zero for large systems. The oscillator strength for this transition scales quadratically with system size, showing an anomalous one-photon superradiance. For systems of infinite size, we find a novel, singular spectroscopic signature of the quantum phase transition between disordered and ordered ground states. We outline how arrays of ultra cold dipolar molecules trapped in an optical lattice can be used to access the strong coupling regime and observe the anomalous superradiant effects associated with this regime.",1307.2913v2 2013-10-18,Weyl spin-orbit-coupling-induced interactions in uniform and trapped atomic quantum fluids,"We establish through analytical and numerical studies of thermodynamic quantities for noninteracting atomic gases that the isotropic three-dimensional spin-orbit coupling, the Weyl coupling, induces interaction which counters ""effective"" attraction (repulsion) of the exchange symmetry present in zero-coupling Bose (Fermi) gas. The exact analytical expressions for the grand potential and hence for several thermodynamic quantities have been obtained for this purpose in both uniform and trapped cases. It is enunciated that many interesting features of spin-orbit coupled systems revealed theoretically can be understood in terms of coupling-induced modifications in statistical interparticle potential. The temperature-dependence of the chemical potential, specific heat and isothermal compressibility for a uniform Bose gas is found to have signature of the incipient Bose-Einstein condensation in very weak coupling regime although the system does not really go in the Bose-condensed phase. The transition temperature in harmonically trapped case decreases with increase of coupling strength consistent with the weakening of the statistical attractive interaction. Anomalous behavior of some thermodynamic quantities, partly akin to that in dimensions less than two, appears for uniform fermions as soon as the Fermi level goes down the Dirac point on increasing the coupling strength. It is suggested that the fluctuation-dissipation theorem can be utilized to verify anomalous behaviors from studies of long-wavelength fluctuations in bunching and antibunching effects.",1310.5180v1 2013-12-18,Aharonov-Bohm interferometry with a tunnel-coupled wire,"Recent experiments [M. Yamamoto et al., Nature Nanotechnology 7, 247 (2012)] used the transport of electrons through an Aharonov-Bohm interferometer and two coupled channels (at both ends of the interferometer) to demonstrate a manipulable flying qubit. Results included in-phase and anti-phase Aharonov-Bohm (AB) oscillations of the two outgoing currents as a function of the magnetic flux, for strong and weak inter-channel coupling, respectively. Here we present new experimental results for a three terminal interferometer, with a tunnel coupling between the two outgoing wires. We show that in some limits, this system is an even simpler realization of the ""two-slit"" experiment. We also present a simple tight- binding theoretical model which imitates the experimental setup. For weak inter-channel coupling, the AB oscillations in the current which is reflected from the device are very small, and therefore the oscillations in the two outgoing currents must cancel each other, yielding the anti-phase behavior, independent of the length of the coupling regime. For strong inter-channel coupling, whose range depends on the asymmetry between the channels, and for a relatively long coupling distance, all except two of the waves in the coupled channels become evanescent. For the remaining running waves one has a very weak dependence of the ratio between the currents in the two channels on the magnetic flux, implying that these currents are in phase with each other.",1312.5177v1 2014-04-05,Model Predictive Control (MPC) Applied To Coupled Tank Liquid Level System,"Coupled Tank system used for liquid level control is a model of plant that has usually been used in industries especially chemical process industries. Level control is also very important for mixing reactant process. This survey paper tries to presents in a systemic way an approach predictive control strategy for a system that is similar to the process and is represented by two liquid tanks. This system of coupled Tank is one of the most commonly available systems representing a coupled Multiple Input Multiple Output (MIMO) system. With 2 inputs and 2 outputs, it is the most primitive form of a coupled multivariable system. Therefor the basic concept of how the coupled tanks system works is by using a numerical system which it operates with a flow control valve FCV as main control of the level of liquid in one tank or both tanks. For this paper, MPC algorithm control is used which will be developed below. And it is focuses on the design and modelling for coupled tanks system. The steps followed for the design of the controller are: Developing a state space system model for the coupled tank system then design an MPC controller for the developed system model. And study the effect of the disturbance on measured level output. Note that the implementation Model Predictive Controller on flow controller valve in a Coupled Tank liquid level system is one of the new methods of controlling liquid level.",1404.1498v1 2014-07-02,Spin Waves in Ferromagnetic Insulators Coupled via a Normal Metal,"Herein, we study the spin-wave dispersion and dissipation in a ferromagnetic insulator--normal metal--ferromagnetic insulator system. Long-range dynamic coupling because of spin pumping and spin transfer lead to collective magnetic excitations in the two thin-film ferromagnets. In addition, the dynamic dipolar field contributes to the interlayer coupling. By solving the Landau-Lifshitz-Gilbert-Slonczewski equation for macrospin excitations and the exchange-dipole volume as well as surface spin waves, we compute the effect of the dynamic coupling on the resonance frequencies and linewidths of the various modes. The long-wavelength modes may couple acoustically or optically. In the absence of spin-memory loss in the normal metal, the spin-pumping-induced Gilbert damping enhancement of the acoustic mode vanishes, whereas the optical mode acquires a significant Gilbert damping enhancement, comparable to that of a system attached to a perfect spin sink. The dynamic coupling is reduced for short-wavelength spin waves, and there is no synchronization. For intermediate wavelengths, the coupling can be increased by the dipolar field such that the modes in the two ferromagnetic insulators can couple despite possible small frequency asymmetries. The surface waves induced by an easy-axis surface anisotropy exhibit much greater Gilbert damping enhancement. These modes also may acoustically or optically couple, but they are unaffected by thickness asymmetries.",1407.0635v1 2014-09-24,Rotomagnetic couplings influence on the magnetic properties of antiferrodistortive antiferromagnets,"Within the framework of Landau-Ginzburg-Devonshire (LGD) phenomenological theory we consider the possibility to control properties of paraelectric antiferromagnets via biquadratic rotomagnetic coupling with and without external magnetic and electric field application. We use EuTiO3 as a prototype with relatively well-known material parameters. Surprisingly strong influence of this coupling practically on all the properties without external fields was obtained in the temperature region with coexistence of antiferromagnetic and antiferrodistorted phases i.e. in multiferroic state. In particular, the observed Neel temperature TN (5.5 K) was shown to be defined by rotomagnetic coupling, while without this coupling TN appeared to be much higher (26 K). For small or high enough rotomagnetic coupling constant value the antiferromagnetic phase transition order appeared to be the second or the first order respectively. The essential influence of rotomagnetic coupling on the form and value of magnetic and dielectric permittivity was also forecasted. The rotomagnetic coupling along with rotoelectric one opens the additional way to control the form of the phase diagrams by application of external magnetic or electric field. The critical value of the electric field (for antiferromagnetic to ferromagnetic phase transition) appeared essentially smaller than the one calculated without rotomagnetic coupling that can be important for applications.",1409.7108v1 2015-01-12,On the strong coupling scale in Higgs G-inflation,"Higgs G-inflation is an inflation model that takes advantage of a Galileon-like derivative coupling. It is a non-renormalizable operator and is strongly coupled at high energy scales. Perturbative analysis does not have a predictive power any longer there. In general, when the Lagrangian is expanded around the vacuum, the strong coupling scale is identified as the mass scale that appears in non-renormalizable operators. In inflationary models, however, the identification of the strong coupling scale is subtle, since the structures of the kinetic term as well as the interaction itself can be modified by the background inflationary dynamics. Therefore, the strong coupling scale depends on the background. In this letter, we evaluate the strong coupling scale of the fluctuations around the background in the Higgs G-inflation including the Nambu-Goldstone modes associated with the symmetry breaking. We find that the system is sufficiently weakly coupled when the scales which we now observe exit the horizon during inflation and the observational predictions with the semiclassical treatment are valid. However, we also find that the inflaton field value at which the strong coupling scale and the Hubble scale meet is less than the Planck scale. Therefore, we cannot describe the model from the Planck scale, or the chaotic initial condition.",1501.02816v2 2015-03-16,Experimental constraints on the coupling of the Higgs boson to electrons,"In the standard model (SM), the coupling of the Higgs boson to electrons is real and very small, proportional to the electron mass. New physics could significantly modify both real and imaginary parts of this coupling. We discuss experiments which are sensitive to the Higgs-electron coupling and derive the current bounds on new physics contributing to this coupling. The strongest constraint follows from the ACME bound on the electron electric dipole moment (EDM). We calculate the full analytic two-loop result for the electron EDM and show that it bounds the imaginary part of the Higgs-electron coupling to be less than 1.7 x 10^-2 times the SM electron Yukawa coupling. Deviations of the real part are much less constrained. We discuss bounds from Higgs decays, resonant Higgs production at electron colliders, Higgs mediated B -> e^+ e^- decays, and the anomalous magnetic moment of the electron. Currently, the strongest constraint comes from h -> e^+ e^- at the LHC, bounding the coupling to be less than ~600 times the SM Yukawa coupling. Important improvements can be expected from future EDM measurements as well as from resonant Higgs production at a next-generation high-luminosity e^+ e^- collider.",1503.04830v1 2015-04-27,Effects of Coupled Dark Energy on the Milky Way and its Satellites,"We present the first numerical simulations in coupled dark energy cosmologies with high enough resolution to investigate the effects of the coupling on galactic and sub-galactic scales. We choose two constant couplings and a time-varying coupling function and we run simulations of three Milky-Way-size halos ($\sim$10$^{12}$M$_{\odot}$), a lower mass halo (6$\times$10$^{11}$M$_{\odot}$) and a dwarf galaxy halo (5$\times$10$^{9}$M$_{\odot}$). We resolve each halo with several millions dark matter particles. On all scales the coupling causes lower halo concentrations and a reduced number of substructures with respect to LCDM. We show that the reduced concentrations are not due to different formation times, but they are related to the extra terms that appear in the equations describing the gravitational dynamics. On the scale of the Milky Way satellites, we show that the lower concentrations can help in reconciling observed and simulated rotation curves, but the coupling values necessary to have a significant difference from LCDM are outside the current observational constraints. On the other hand, if other modifications to the standard model allowing a higher coupling (e.g. massive neutrinos) are considered, coupled dark energy can become an interesting scenario to alleviate the small-scale issues of the LCDM model.",1504.07243v1 2016-02-08,Collective couplings: rectification and supertransmittance,"We investigate heat transport between two thermal reservoirs that are coupled via a large spin composed of N identical two level systems. One coupling implements the dissipative Dicke super- radiance. The other coupling is locally of the pure-dephasing type and requires to go beyond the standard weak-coupling limit by employing a Bogoliubov mapping in the corresponding reservoir. After the mapping, the large spin is coupled to a collective mode with the original pure-dephasing interaction, but the collective mode is dissipatively coupled to the residual oscillators. Treating the large spin and the collective mode as the system, a standard master equation approach is now able to capture the energy transfer between the two reservoirs. Assuming fast relaxation of the collective mode, we derive a coarse-grained rate equation for the large spin only and discuss how the original Dicke superradiance is affected by the presence of the additional reservoir. Our main finding is a cooperatively enhanced rectification effect due to the interplay of supertransmittant heat currents (scaling quadratically with $N$) and the asymmetric coupling to both reservoirs. For large $N$, the system can thus significantly amplify current asymmetries under bias reversal, functioning as a heat diode. We also briefly discuss the case when the couplings of the collective spin are locally dissipative, showing that the heat-diode effect is still present.",1602.02502v2 2016-06-15,Coupling a single electron spin to a microwave resonator: Controlling transverse and longitudinal couplings,"Microwave-frequency superconducting resonators are ideally suited to perform dispersive qubit readout, to mediate two-qubit gates, and to shuttle states between distant quantum systems. A prerequisite for these applications is a strong qubit-resonator coupling. Strong coupling between an electron-spin qubit and a microwave resonator can be achieved by correlating spin- and orbital degrees of freedom. This correlation can be achieved through the Zeeman coupling of a single electron in a double quantum dot to a spatially inhomogeneous magnetic field generated by a nearby nanomagnet. In this paper, we consider such a device and estimate spin-resonator couplings of order ~ 1 MHz with realistic parameters. Further, through realistic simulations, we show that precise placement of the double dot relative to the nanomagnet allows to select between a purely longitudinal coupling (commuting with the bare spin Hamiltonian) and a purely transverse (spin non-conserving) coupling. Additionally, we suggest methods to mitigate dephasing and relaxation channels that are introduced in this coupling scheme. This analysis gives a clear route toward the realization of coherent state transfer between a microwave resonator and a single electron spin in a GaAs double quantum dot with a fidelity above 90%. Improved dynamical decoupling sequences, low-noise environments, and longer-lived microwave cavity modes may lead to substantially higher fidelities in the near future.",1606.04736v3 2016-07-19,Transportation dynamics on coupled networks with limited bandwidth,"The communication networks in real world often couple with each other to save costs, which results in any network does not have a stand-alone function and efficiency. To investigate this, in this paper we propose a transportation model on two coupled networks with bandwidth sharing. We find that the free-flow state and the congestion state can coexist in the two coupled networks, and the free-flow path and congestion path can coexist in each network. Considering three bandwidth-sharing mechanisms, random, assortative and disassortative couplings, we also find that the transportation capacity of the network only depends on the coupling mechanism, and the fraction of coupled links only affects the performance of the system in the congestion state, such as the traveling time. In addition, with assortative coupling, the transportation capacity of the system will decrease significantly. However, the disassortative coupling has little influence on the transportation capacity of the system, which provides a good strategy to save bandwidth. Furthermore, a theoretical method is developed to obtain the bandwidth usage of each link, based on which we can obtain the congestion transition point exactly.",1607.05382v2 2017-03-16,Spontaneous symmetry breaking due to the trade-off between attractive and repulsive couplings,"Spontaneous symmetry breaking (SSB) is an important phenomenon observed in various fields including physics and biology. In this connection, we here show that the trade-off between attractive and repulsive couplings can induce spontaneous symmetry breaking in a homogeneous system of coupled oscillators. With a simple model of a system of two coupled Stuart-Landau oscillators, we demonstrate how the tendency of attractive coupling in inducing in-phase synchronized (IPS) oscillations and the tendency of repulsive coupling in inducing out-of-phase synchronized (OPS) oscillations compete with each other and give rise to symmetry breaking oscillatory (SBO) states and interesting multistabilities. Further, we provide explicit expressions for synchronized and anti-synchronized oscillatory states as well as the so called oscillation death (OD) state and study their stability. If the Hopf bifurcation parameter (${\lambda}$) is greater than the natural frequency ($\omega$) of the system, the attractive coupling favours the emergence of an anti-symmetric OD state via a Hopf bifurcation whereas the repulsive coupling favours the emergence of a similar state through a saddle-node bifurcation. We show that an increase in the repulsive coupling not only destabilizes the IPS state but also facilitates the re-entrance of the IPS state.",1703.05718v1 2017-08-07,Coupling and stability of interfacial waves in liquid metal batteries,"We investigate the interfacial wave coupling dynamics in liquid metal batteries and their effects to the battery's operation safety. Similar to aluminum reduction cells, liquid metal batteries can be highly susceptible to magnetohydrodynamical instabilities that excite undesired interfacial waves capable to provoke short-circuits. However, in liquid metal batteries the wave dynamics is far more complex since two metal-electrolyte interfaces are present that may step into resonance. In the first part of this paper, we present a Potential analysis of coupled gravity-capillary interfacial waves in a three-layer battery model of cylindrical shape. Analytical expressions for the amplitude ratio and the wave frequencies are derived and it is shown that the wave coupling can be completely described by two independent dimensionless parameters. We provide a decoupling criterion clarifying that wave coupling will be present in most future liquid metal batteries. In the second part, the theory is validated by comparing it with multiphase direct numerical simulations. An accompanying parameter study is conducted to analyze the system stability for differently strongly coupled interfaces. Three different coupling regimes are identified involving characteristic coupling dynamics. For strongly coupled interfaces we observe novel instabilities that may have beneficial effects on the operational safety.",1708.02159v2 2017-01-25,The quantum Zeno and anti-Zeno effects with strong system-environment coupling,"The fact that repeated projective measurements can slow down (the Zeno effect) or speed up (the anti-Zeno effect) quantum evolution is well-known. However, to date, studies of these effects focus on quantum systems that are weakly interacting with their environment. In this paper, we investigate what happens to a quantum system under the action of repeated measurements if the quantum system is strongly interacting with its environment. We consider as the quantum system a single two-level system coupled strongly to a collection of harmonic oscillators. A so-called polaron transformation is then used to make the problem in the strong system-environment coupling regime tractable. We find that the strong coupling case exhibits quantitative and qualitative differences as compared with the weak coupling case. In particular, the effective decay rate does not depend linearly on the spectral density of the environment. This then means that, in the strong coupling regime that we investigate, increasing the system-environment coupling strength can actually decrease the effective decay rate. We also consider a collection of two-level atoms coupled strongly with a common environment. In this case, we find that there are further differences between the weak and strong coupling cases since the two-level atoms can now indirectly interact with one another due to the common environment.",1701.07283v1 2011-11-11,Ground states of a mixture of two species of spin-1 Bose gases with interspecies spin exchange in a magnetic field,"We consider a mixture of two species of spin-1 atoms with both interspecies and intraspecies spin exchanges in a weak magnetic field. Under the usual single mode approximation, it can be reduced to a model of coupled giant spins. We find most of its ground states. This is a complicated problem of energy minimization, with three quantum variables under constraints, i.e. the total spin of each species and the total spin of the whole mixture, as well as four parameters, including intraspecies and interspecies spin coupling strengths and the magnetic field. The quantum phase diagram is very rich. Compared with the case without a magnetic field, the ground states are modified by a magnetic field, which also modifies the ground state boundaries or introduces new crossover regimes on the phase diagram. Without interspecies spin coupling, the quantum phase transitions existing in absence of a magnetic field disappear when a magnetic field is applied, which leads to crossover regimes in the phase diagram. Under ferromagnetic interspecies spin coupling, the ground states remain disentangled no matter whether there is a magnetic field. For antiferromagnetic interspecies spin coupling, a magnetic field entangles the ground states in some parameter regimes. When the intraspecies spin couplings are both ferromagnetic, the quantum phase transition between antiferromagnetic and zero interspecies spin couplings survives the magnetic field. When the intraspecies spin couplings are both antiferromagnetic, a magnetic field induces new quantum phase transitions between antiferromagnetic and zero interspecies spin couplings.",1111.2644v1 2017-06-05,Coupling functions: Universal insights into dynamical interaction mechanisms,"The dynamical systems found in Nature are rarely isolated. Instead they interact and influence each other. The coupling functions that connect them contain detailed information about the functional mechanisms underlying the interactions and prescribe the physical rule specifying how an interaction occurs. Here, we aim to present a coherent and comprehensive review encompassing the rapid progress made recently in the analysis, understanding and applications of coupling functions. The basic concepts and characteristics of coupling functions are presented through demonstrative examples of different domains, revealing the mechanisms and emphasizing their multivariate nature. The theory of coupling functions is discussed through gradually increasing complexity from strong and weak interactions to globally-coupled systems and networks. A variety of methods that have been developed for the detection and reconstruction of coupling functions from measured data is described. These methods are based on different statistical techniques for dynamical inference. Stemming from physics, such methods are being applied in diverse areas of science and technology, including chemistry, biology, physiology, neuroscience, social sciences, mechanics and secure communications. This breadth of application illustrates the universality of coupling functions for studying the interaction mechanisms of coupled dynamical systems.",1706.01810v3 2017-06-21,Exact Coupling of Random Walks on Polish Groups,"Exact coupling of random walks is studied. Conditions for admitting a successful exact coupling are given that are necessary and in the Abelian case also sufficient. In the Abelian case, it is shown that a random walk $S$ with step-length distribution $\mu$ started at $0$ admits a successful exact coupling with a version $S^x$ started at $x$ if and only if there is $n\geq 1$ with $\mu^{n} \wedge \mu^{n}(x+\cdot) \neq 0$. Moreover, when a successful exact coupling exists, the total variation distance between $S_n$ and $S^x_n$ is determined to be $O(n^{-1/2})$ if $x$ has infinite order, or $O(\rho^n)$ for some $\rho \in (0,1)$ if $x$ has finite order. In particular, this paper solves a problem posed by H. Thorisson on successful exact coupling of random walks on $\mathbb{R}$. It is also noted that the set of such $x$ for which a successful exact coupling can be constructed is a Borel measurable group. Lastly, the weaker notion of possible exact coupling and its relationship to successful exact coupling are studied.",1706.06968v4 2017-09-30,Multiple critical coupling and sensing in a microresonator-waveguide system,"We study the optical transmission of a waveguide that is side-coupled to a high-$Q$ circular microresonator. The coupling is critical if the intrinsic resonator losses equate the coupling losses to the waveguide. When this happens, the transmittance of the waveguide displays resonance dips with maximal depth as the frequency is swept through the resonators resonances. We show that multiple configurations, parameterised by the minimal distance between the resonator and the waveguide, can lead to critical coupling. Indeed, for a sufficiently large resonator radius, the flow of power between the waveguide and the resonator can change sign several times within a single pass. This leads to an oscillatory coupling parameter as a function of the separation distance. As a result, multiple geometrical configurations can lead to critical coupling, even if the waveguide lies in the equatorial plane of the resonator. These results are explained using coupled-mode theory and full wave numerical simulations. In the vicinity of secondary or higher-order critical coupling, the depth of the transmittance dip is very sensitive to the environment. We discuss how this effect can be exploited for sensing purpose. Alternatively, by actively controlling the environment in the secondary critical configuration, the waveguide/resonator system can be driven as an optical switch.",1710.00178v1 2017-12-10,Mass scale of vectorlike matter and superpartners from IR fixed point predictions of gauge and top Yukawa couplings,"We use the IR fixed point predictions for gauge couplings and the top Yukawa coupling in the MSSM extended with vectorlike families to infer the scale of vectorlike matter and superpartners. We quote results for several extensions of the MSSM and present results in detail for the MSSM extended with one complete vectorlike family. We find that for a unified gauge coupling $\alpha_G > 0.3$ vectorlike matter or superpartners are expected within 1.7 TeV (2.5 TeV) based on all three gauge couplings being simultaneously within 1.5\% (5\%) from observed values. This range extends to about 4 TeV for $\alpha_G > 0.2$. We also find that in the scenario with two additional large Yukawa couplings of vectorlike quarks the IR fixed point value of the top Yukawa coupling independently points to a multi-TeV range for vectorlike matter and superpartners. Assuming a universal value for all large Yukawa couplings at the GUT scale, the measured top quark mass can be obtained from the IR fixed point for $\tan \beta \simeq 4$. The range expands to any $\tan \beta > 3$ for significant departures from the universality assumption. Considering that the Higgs boson mass also points to a multi-TeV range for superpartners in the MSSM, adding a complete vectorlike family at the same scale provides a compelling scenario where the values of gauge couplings and the top quark mass are understood as a consequence of the particle content of the model.",1712.03527v4 2017-12-15,Large spin relaxation anisotropy and valley-Zeeman spin-orbit coupling in WSe2/Gr/hBN heterostructures,"Large spin-orbital proximity effects have been predicted in graphene interfaced with a transition metal dichalcogenide layer. Whereas clear evidence for an enhanced spin-orbit coupling has been found at large carrier densities, the type of spin-orbit coupling and its relaxation mechanism remained unknown. We show for the first time an increased spin-orbit coupling close to the charge neutrality point in graphene, where topological states are expected to appear. Single layer graphene encapsulated between the transition metal dichalcogenide WSe$_2$ and hBN is found to exhibit exceptional quality with mobilities as high as 100000 cm^2/V/s. At the same time clear weak anti-localization indicates strong spin-orbit coupling and a large spin relaxation anisotropy due to the presence of a dominating symmetric spin-orbit coupling is found. Doping dependent measurements show that the spin relaxation of the in-plane spins is largely dominated by a valley-Zeeman spin-orbit coupling and that the intrinsic spin-orbit coupling plays a minor role in spin relaxation. The strong spin-valley coupling opens new possibilities in exploring spin and valley degree of freedom in graphene with the realization of new concepts in spin manipulation.",1712.05678v2 2020-12-24,Analysis and Design of Partially Information- and Partially Parity-Coupled Turbo Codes,"In this paper, we study a class of spatially coupled turbo codes, namely partially information- and partially parity-coupled turbo codes. This class of codes enjoy several advantages such as flexible code rate adjustment by varying the coupling ratio and the encoding and decoding architectures of the underlying component codes can remain unchanged. For this work, we first provide the construction methods for partially coupled turbo codes with coupling memory $m$ and study the corresponding graph models. We then derive the density evolution equations for the corresponding ensembles on the binary erasure channel to precisely compute their iterative decoding thresholds. Rate-compatible designs and their decoding thresholds are also provided, where the coupling and puncturing ratios are jointly optimized to achieve the largest decoding threshold for a given target code rate. Our results show that for a wide range of code rates, the proposed codes attain close-to-capacity performance and the decoding performance improves with increasing the coupling memory. In particular, the proposed partially parity-coupled turbo codes have thresholds within 0.0002 of the BEC capacity for rates ranging from $1/3$ to $9/10$, yielding an attractive way for constructing rate-compatible capacity-approaching channel codes.",2012.13082v1 2020-12-29,Synchronization with prescribed transient behavior: Heterogeneous multi-agent systems under funnel coupling Extended arXiv version,"In this paper, we introduce a nonlinear time-varying coupling law, which can be designed in a fully decentralized manner and achieves approximate synchronization with arbitrary precision, under only mild assumptions on the individual vector fields and the underlying (undirected) graph structure. The proposed coupling law is motivated by the so-called funnel control method studied in adaptive control under the observation that arbitrary precision synchronization can be achieved for heterogeneous multi-agent systems by a high-gain coupling; consequently we call our novel synchronization method `(node-wise) funnel coupling.' By adjusting the conventional proof technique in the funnel control study, we are even able to obtain asymptotic synchronization with the same funnel coupling law. Moreover, the emergent collective behavior that arises for a heterogeneous multi-agent system when enforcing arbitrary precision synchronization by the proposed funnel coupling law, is analyzed in this paper. In particular, we introduce a single scalar dynamics called `emergent dynamics' which describes the emergent synchronized behavior of the multi-agent system under funnel coupling. Characterization of the emergent dynamics is important because, for instance, one can design the emergent dynamics first such that the solution trajectory behaves as desired, and then, provide a design guideline to each agent so that the constructed vector fields yield the desired emergent dynamics. We illustrate this idea via the example of a distributed median solver based on funnel coupling.",2012.14580v3 2020-12-31,"Zeroth Law in Quantum Thermodynamics at Strong Coupling: `in Equilibrium', not `Equal Temperature'","The zeroth law of thermodynamics involves a transitivity relation (pairwise between three objects) expressed either in terms of `equal temperature' (ET), or `in equilibrium' (EQ) conditions. In conventional thermodynamics conditional on vanishingly weak system-bath coupling these two conditions are commonly regarded as equivalent. In this work we show that for thermodynamics at strong coupling they are inequivalent: namely, two systems can be in equilibrium and yet have different effective temperatures. A recent result \cite{NEqFE} for Gaussian quantum systems shows that an effective temperature $T^{*}$ can be defined at all times during a system's nonequilibrium evolution, but because of the inclusion of interaction energy, after equilibration the system's $T^*$ is slightly higher than the bath temperature $T_{\textsc{b}}$, with the deviation depending on the coupling. A second object coupled with a different strength with an identical bath at temperature $T_{\textsc{b}}$ will not have the same equilibrated temperature as the first object. Thus $ET \neq EQ $ for strong coupling thermodynamics. We then investigate the conditions for dynamical equilibration for two objects 1 and 2 strongly coupled with a common bath $B$, each with a different equilibrated effective temperature. We show this is possible, and prove the existence of a generalized fluctuation-dissipation relation under this configuration. This affirms that `in equilibrium' is a valid and perhaps more fundamental notion which the zeroth law for quantum thermodynamics at strong coupling should be based on. Only when the system-bath coupling becomes vanishingly weak that `temperature' appearing in thermodynamic relations becomes universally defined and makes better physical sense.",2012.15607v1 2012-05-21,Coupled-Channel Effects in Collisions between Heavy Ions near the Coulomb Barrier,"With the recent availability of state-of-the-art heavy-ion stable and radioactive beams, there has been a renew interest in the investigation of nuclear reactions with heavy ions. I first present the role of inelastic and transfer channel couplings in fusion reactions induced by stable heavy ions. Analysis of experimental fusion cross sections by using standard coupled-channel calculations is discussed. The role of multi-neutron transfer is investigated in the fusion process below the Coulomb barrier by analyzing $^{32}$S+$^{90,96}$Zr as benchmark reactions. The enhancement of fusion cross sections for $^{32}$S+$^{96}$Zr is well reproduced at sub-barrier energies by NTFus code calculations including the coupling of the neutron-transfer channels following the Zagrebaev semi-classical model. Similar effects for $^{40}$Ca+$^{90}$Zr and $^{40}$Ca+$^{96}$Zr fusion excitation functions are found. The breakup coupling in both the elastic scattering and in the fusion process induced by weakly bound stable projectiles is also shown to be crucial. In this lecture, full coupled-channel calculations of the fusion excitation functions are performed by using the breakup coupling for the more neutron-rich reaction and for the more weakly bound projectiles. I clearly demonstrate that Continuum-Discretized Coupled-Channel calculations are capable to reproduce the fusion enhancement from the breakup coupling in $^{6}$Li+$^{59}$Co.",1205.4630v1 2017-05-30,Interplay between short-range correlated disorder and Coulomb interaction in nodal-line semimetals,"In nodal-line semimetals, Coulomb interactions and short-range correlated disorder are both marginal perturbations to the clean non-interacting Hamiltonian. We analyze their interplay using a weak-coupling renormalization group approach. In the clean case, the Coulomb interaction has been found to be marginally irrelevant, leading to Fermi liquid behavior. We extend the analysis to incorporate the effects of disorder. The nodal line structure gives rise to kinematical constraints similar to that for a two-dimensional Fermi surface, which plays a crucial role in the one-loop renor- malization of the disorder couplings. For a two-fold degenerate nodal loop (Weyl loop), we show that disorder flows to strong coupling along a unique fixed trajectory in the space of symmetry inequiv- alent disorder couplings. Along this fixed trajectory, all symmetry inequivalent disorder strengths become equal. For a four-fold degenerate nodal loop (Dirac loop), disorder also flows to strong coupling, however the strengths of symmetry inequivalent disorder couplings remain different. We show that feedback from disorder reverses the sign of the beta function for the Coulomb interaction, causing the Coulomb interaction to flow to strong coupling as well. However, the Coulomb interac- tion flows to strong coupling asymptotically more slowly than disorder. Extrapolating our results to strong coupling, we conjecture that at low energies nodal line semimetals should be described by a noninteracting nonlinear sigma model. We discuss the relation of our results with possible many-body localization at zero temperatures in such materials.",1705.10809v2 2018-06-27,Temperature Dependence of Paramagnetic Critical Magnetic Field in Disordered Attractive Hubbard Model,"Within the generalized DMFT+$\Sigma$ approach we study disorder effects in the temperature dependence of paramagnetic critical magnetic field $H_{cp}(T)$ for Hubbard model with attractive interaction. We consider the wide range of attraction potentials $U$ - from the weak coupling limit, when superconductivity is described by BCS model, up to the limit of very strong coupling, when superconducting transition is related to Bose - Einstein condensation (BEC) of compact Cooper pairs. The growth of the coupling strength leads to the rapid growth of $H_{cp}(T)$ at all temperatures. However, at low temperatures paramagnetic critical magnetic field $H_{cp}$ grows with $U$ much slower, than the orbital critical field, and in BCS limit the main contribution to the upper critical magnetic filed is of paramagnetic origin. The growth of the coupling strength also leads to the disappearance of the low temperature region of instability towards type I phase transition and Fulde - Ferrell - Larkin - Ovchinnikov (FFLO) phase, characteristic for BCS weak coupling limit. Disordering leads to the rapid drop of $H_{cp}(T)$ in BCS weak coupling limit, while in BCS - BEC crossover region and BEC limit $H_{cp}(T\to 0)$ dependence on disorder is rather weak. Within DMFT+$\Sigma$ approach disorder influence on $H_{cp}(T)$ is of universal nature at any coupling strength and related only to disorder widening of the conduction band. In particular, this leads to the drop of the effective coupling strength with disorder, so that disordering restores the region of type I transition in the intermediate coupling region.",1806.10440v1 2019-04-17,Information Based Centralization of Locomotion in Animals and Robots,"Movement in biology is often achieved with distributed control of coupled subcomponents, e.g. muscles and limbs. Coupling could range from weak and local, i.e. decentralized, to strong and global, i.e. centralized. We developed a model-free measure of centralization that compares information shared between control signals and both global and local states. A second measure, called co-information, quantifies the net redundant information the control signal shares with both states. We first validate our measures through simulations of coupled oscillators and show that it successfully reconstructs the shift from low to high coupling strengths. We then measure centralization in freely running cockroaches. Surprisingly, extensor muscle activity in the middle leg is more informative of movements of all legs combined than the movements of that particular leg. Cockroach centralization successfully recapitulates a specific model of a strongly coupled oscillator network previously used to model cockroach leg kinematics. When segregated by stride frequency, slower cockroach strides exhibit more shared information per stride between control and output states than faster strides, indicative of an information bandwidth limitation. However, centralization remains consistent between the two groups. We then used a robotic model to show that centralization can be affected by mechanical coupling independent of neural coupling. The mechanically coupled bounding gait is decentralized and becomes more decentralized as mechanical coupling decreases while internal parameters of control remain constant. The results of these systems span a design space of centralization and co-information that can be used to test biological hypotheses and advise the design of robotic control.",1904.10498v1 2019-11-15,High energy asymptotic behavior of the $S$-matrix in the saturation region with the smallest dipole running coupling prescription,"We present results from analytic solutions to the running coupling, full next-to-leading order, and collinearly improved next-to-leading order Balitsky-Kovchegov equations in the saturation region with the smallest dipole size QCD running coupling prescription. The analytic results of the $S$-matrix of the latter two equations show that the $\exp(-\mathcal{O}(Y^{3/2}))$ rapidity dependence of the solutions are replaced by $\exp(-\mathcal{O}(Y))$ dependence once the running coupling prescription is switched from parent dipole to the smallest dipole prescription, which indicate that the $S$-matrix has a strong dependence on the choice of running coupling prescription. We compute the numerical solutions of these Balitsky-Kovchegov equations with the smallest and parent dipole running coupling prescriptions, the numerical results confirm the analytic outcomes. The rare fluctuations of the $S$-matrix on top of next-to-leading order corrections are also studied under the smallest dipole running coupling prescription in the center of mass frame. It shows that the rare fluctuations are strongly suppressed and less important in the smallest dipole running coupling prescription case as compared to the parent dipole running coupling prescription case.",1911.06744v1 2019-11-27,How spin-orbital entanglement depends on the spin-orbit coupling in a Mott insulator,"The concept of the entanglement between spin and orbital degrees of freedom plays a crucial role in understanding various phases and exotic ground states in a broad class of materials, including orbitally ordered materials and spin liquids. We investigate how the spin-orbital entanglement in a Mott insulator depends on the value of the spin-orbit coupling of the relativistic origin. To this end, we numerically diagonalize a 1D spin-orbital model with the 'Kugel-Khomskii' exchange interactions between spins and orbitals on different sites supplemented by the on-site spin-orbit coupling. In the regime of small spin-orbit coupling w.r.t. the spin-orbital exchange, the ground state to a large extent resembles the one obtained in the limit of vanishing spin-orbit coupling. On the other hand, for large spin-orbit coupling the ground state can, depending on the model parameters, either still show negligible spin-orbital entanglement, or can evolve to a highly spin-orbitally entangled phase with completely distinct properties that are described by an effective XXZ model. The presented results suggest that: (i) the spin-orbital entanglement may be induced by large on-site spin-orbit coupling, as found in the 5d transition metal oxides, such as the iridates; (ii) for Mott insulators with weak spin-orbit coupling of Ising-type, such as e.g. the alkali hyperoxides, the effects of the spin-orbit coupling on the ground state can, in the first order of perturbation theory, be neglected.",1911.12180v2 2016-12-09,Spectral Classification of Coupling Regimes in the Quantum Rabi Model,"The quantum Rabi model is in the scientific spotlight due to the recent theoretical and experimental progress. Nevertheless, a full-fledged classification of its coupling regimes remains as a relevant open question. We propose a spectral classification dividing the coupling regimes into three regions based on the validity of perturbative criteria on the quantum Rabi model, which allows us the use of exactly solvable effective Hamiltonians. These coupling regimes are i) the perturbative ultrastrong coupling regime which comprises the Jaynes-Cummings model, ii) a region where non-perturbative ultrastrong and non-perturbative deep strong coupling regimes coexist, and iii) the perturbative deep strong coupling regime. We show that this spectral classification depends not only on the ratio between the coupling strength and the natural frequencies of the unperturbed parts, but also on the energy to which the system can access. These regimes additionally discriminate the completely different behaviors of several static physical properties, namely the total number of excitations, the photon statistics of the field, and the cavity-qubit entanglement. Finally, we explain the dynamical properties which are traditionally associated to the deep strong coupling regime, such as the collapses and revivals of the state population, in the frame of the proposed spectral classification.",1612.03090v1 2017-07-06,Antisymmetric Spin-Orbit Coupling Effect on Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot,"We study the local antisymmetric spin-orbit (ASO) coupling effect on spin, orbital, and charge degrees of freedom for the Kondo effect in a triangular triple quantum dot (TTQD). Here, one of the three QDs is coupled to a metallic lead through electron tunneling, and a local electric polarization is induced by the Kondo effect. The ASO interaction is introduced in the other two coupled QDs on the opposite side of the lead. Generally, the ASO coupling effect is very weak and not easily detectable, but it essentially causes spin and charge reconfigurations in the TTQD through the Kondo effect. Using an extended Anderson model for the TTQD Kondo system, we elucidate that the ASO coupling gives rise to a considerable reduction of the emergent electric polarization, as a consequence of the parity mixing of molecular orbitals in the triangular loop as well as the spin-up and spin-down coupling of local electrons. The latter leads to a local diamagnetic susceptibility owing to the ASO coupled spins. We also show that the Kondo-induced electric polarization can be controlled by the ASO coupling as well as by the magnetic flux penetrating through the TTQD.",1707.01676v1 2017-07-18,"Inflationary magneto-(non)genesis, increasing kinetic couplings, and the strong coupling problem","We study the generation of magnetic fields during inflation making use of a coupling of the inflaton and moduli fields to electromagnetism via the photon kinetic term, and assuming that the coupling is an increasing function of time. We demonstrate that the strong coupling problem of inflationary magnetogenesis can be avoided by incorporating the destabilization of moduli fields after inflation. The magnetic field always dominates over the electric one, and thus the severe constraints on the latter from backreaction, which are the demanding obstacles in the case of a decreasing coupling function, do not apply to the current scenario. However, we show that this loophole to the strong coupling problem comes at a price: the normalization of the amplitude of magnetic fields is determined by this coupling term and is therefore suppressed by a large factor after the moduli destabilization completes. From this we conclude that there is no self-consistent and generic realization of primordial magnetogenesis producing scale-invariant fields in the case of an increasing kinetic coupling.",1707.05820v3 2018-10-22,The Linear Stability of Symmetric Spike Patterns for a Bulk-Membrane Coupled Gierer-Meinhardt Model,"We analyze a coupled bulk-membrane PDE model in which a scalar linear 2-D bulk diffusion process is coupled through a linear Robin boundary condition to a two-component 1-D reaction-diffusion (RD) system with Gierer-Meinhardt (nonlinear) reaction kinetics defined on the domain boundary. For this coupled model, in the singularly perturbed limit of a long-range inhibition and short-range activation for the membrane-bound species, asymptotic methods are used to analyze the existence of localized steady-state multi-spike membrane-bound patterns, and to derive a nonlocal eigenvalue problem (NLEP) characterizing $\mathcal{O}(1)$ time-scale instabilities of these patterns. A central, and novel, feature of this NLEP is that it involves a membrane Green's function that is coupled nonlocally to a bulk Green's function. When the domain is a disk, or in the well-mixed shadow-system limit corresponding to an infinite bulk diffusivity, this Green's function problem is analytically tractable, and as a result we will use a hybrid analytical-numerical approach to determine unstable spectra of this NLEP. This analysis characterizes how the 2-D bulk diffusion process and the bulk-membrane coupling modifies the well-known linear stability properties of steady-state spike patterns for the 1-D Gierer-Meinhardt model in the absence of coupling. In particular, phase diagrams in parameter space for our coupled model characterizing either oscillatory instabilities due to Hopf bifurcations, or competition instabilities due to zero-eigenvalue crossings are constructed. Finally, linear stability predictions from the NLEP analysis are confirmed with full numerical finite-element simulations of the coupled PDE system.",1810.09588v1 2019-05-05,Dipole coupling of a tunable hole double quantum dot in germanium hut wire to a microwave resonator,"The germanium (Ge) hut wire system has strong spin-orbit coupling, a long coherence time due to a very large heavy-light hole splitting, and the advantage of site-controlled large-scale hut wire positioning. These properties make the Ge hut wire a promising candidate for the realization of strong coupling of spin to superconducting resonators and scalability for multiple qubit coupling. We have coupled a reflection line resonator to a hole double quantum dot (DQD) formed in Ge hut wire. The amplitude and phase responses of the microwave resonator revealed that the charge stability diagrams of the DQD are in good agreement with those obtained from transport measurements. The DQD interdot tunneling rate is shown to be tunable from 6.2 GHz to 8.5 GHz, which demonstrates the ability to adjust the frequency detuning between the qubit and the resonator. Furthermore, we achieved a hole-resonator coupling strength of up to 15 MHz, with a charge qubit decoherence rate of 0.28 GHz. Meanwhile the hole spin-resonator coupling rate was estimated to be 3 MHz. These results suggest that holes of a DQD in a Ge hut wire are dipole coupled to microwave photons, potentially enabling tunable hole spin-photon interactions in Ge with an inherent spin-orbit coupling.",1905.01586v2 2020-06-15,Derivative couplings in gravitational production in the early universe,"Gravitational particle production in the early universe is due to the coupling of matter fields to curvature. This coupling may include derivative terms that modify the kinetic term. The most general first order action contains derivative couplings to the curvature scalar and to the traceless Ricci tensor, which can be dominant in the case of (pseudo-)Nambu-Goldstone bosons or disformal scalars, such as branons. In the presence of these derivative couplings, the density of produced particles for the adiabatic regime in the de Sitter phase (which mimics inflation) is constant in time and decays with the inverse effective mass (which in turn depends on the coupling to the curvature scalar). In the reheating phase following inflation, the presence of derivative couplings to the background curvature modifies in a nontrivial way the gravitational production even in the perturbative regime. We also show that the two couplings -- to the curvature scalar and to the traceless Ricci tensor -- are drastically different, specially for large masses. In this regime, the production becomes highly sensitive to the former coupling while it becomes independent of the latter.",2006.08546v1 2021-02-24,Theory of the $sp-d$ coupling of transition metal impurities with free carriers in ZnO,"The $s,p-d$ exchange coupling between the spins of band carriers and of transition metal (TM) dopants ranging from Ti to Cu in ZnO is studied within the density functional theory. The $+U$ corrections are included to reproduce the experimental ZnO band gap and the dopant levels. The $p-d$ coupling reveals unexpectedly complex features. In particular, (i) the $p-d$ coupling constants $N_0\beta$ vary about 10 times when going from V to Cu, (ii) not only the value but also the sign of $N_0\beta$ depends on the charge state of the dopant, (iii) the $p-d$ coupling with the heavy holes and the light holes is not the same; in the case of Fe, Co and Ni, $N_0\beta$s for the two subbands can differ twice, and for Cu the opposite sign of the coupling is found for light and heavy holes. The main features of the $p-d$ coupling are determined by the $p-d$ hybridization between the $d$(TM) and $p$(O) orbitals. In contrast, the $s-d$ coupling constant $N_0\alpha$ is almost the same for all TM ions, and does not depend on the charge state of the dopant. The TM-induced spin polarization of the $p$(O) orbitals contributes to the $s-d$ coupling, enhancing $N_0\alpha$.",2102.12338v1 2016-11-25,An Electromagnetic Induced Transparency-like Scheme for Wireless Power Transfer Using Dielectric Resonators,"Similar to the hybridization of three atoms, three coupled resonators interact to form bonding, anti-bonding and non-bonding modes. The non-bonding mode enables an electromagnetic induced transparency like transfer of energy. Here the non-bonding mode, resulting from the strong electric coupling of two dielectric resonators and an enclosure, is exploited to show that it is feasible to transfer power over a distance comparable to the operating wavelength. In this scheme, the enclosure acts as a mediator. The strong coupling permits the excitation of the non-bonding mode with high purity. This approach is different from resonant inductive coupling which works in the sub-wavelength regime. Optimal loads and the corresponding maximum efficiency are determined using two independent methods: Coupled Mode Theory and Circuit modelling. It is shown that, unlike resonant inductive coupling, the figure of merit depends on the enclosure quality and not on the load, which emphasizes the role of the enclosure as a mediator. Briefly after the input excitation is turned on, the energy in the receiver builds up via all coupled and spurious modes. As time elapses, all modes except the non-bonding cease to sustain. Due to the strong coupling between the dielectrics and the enclosure, such systems have unique properties such as high and uniform efficiency over large distances; and minimal fringing fields. These properties suggest that electromagnetic induced transparency like schemes which rely on the use of dielectric resonators can be used to power autonomous systems inside an enclosure or find applications when exposure to the fields needs to be minimal. Finite Element computations are used to verify the theoretical predictions by determining the transfer efficiency, fields profile and coupling coefficients for two different systems.",1611.09647v1 2017-04-14,Energy Distribution in Intrinsically Coupled Systems: The Spring Pendulum Paradigm,"Intrinsically nonlinear coupled systems present different oscillating components that exchange energy among themselves. We present a new approach to deal with such energy exchanges and to investigate how it depends on the system control parameters. The method consists in writing the total energy of the system, and properly identifying the energy terms for each component and, especially, their coupling. To illustrate the proposed approach, we work with the bi-dimensional spring pendulum, which is a paradigm to study nonlinear coupled systems, and is used as a model for several systems. For the spring pendulum, we identify three energy components, resembling the spring and pendulum like motions, and the coupling between them. With these analytical expressions, we analyze the energy exchange for individual trajectories, and we also obtain global characteristics of the spring pendulum energy distribution by calculating spatial and time average energy components for a great number of trajectories (periodic, quasi-periodic and chaotic) throughout the phase space. Considering an energy term due to the nonlinear coupling, we identify regions in the parameter space that correspond to strong and weak coupling. The presented procedure can be applied to nonlinear coupled systems to reveal how the coupling mediates internal energy exchanges, and how the energy distribution varies according to the system parameters.",1704.04532v4 2019-06-03,Dispersive readout of a weakly coupled qubit via the parity-time-symmetric phase transition,"For some cavity-quantum-electrodynamics systems, such as a single electron spin coupled to a passive cavity, it is challenging to reach the strong-coupling regime. In such a weak-coupling regime, the conventional dispersive readout technique cannot be used to resolve the quantum states of the spin. Here we propose an improved dispersive readout method to measure the quantum states of a weakly coupled qubit by harnessing either one or two auxiliary cavities linearly coupled to the passive cavity containing the qubit. With appropriate parameters in both cases, the system excluding the qubit can exhibit a parity-time-symmetric phase transition at the exceptional point (EP). Because the EP can amplify the perturbation induced by the qubit and the parity-time symmetry can narrow the linewidths of the peaks in the transmission spectrum of the passive cavity, we can measure the quantum states of the weakly coupled qubit via this transmission spectrum. Owing to the weak coupling between the qubit and the passive cavity, the backaction due to the measurement of the qubit can also be reduced in comparison with the conventional dispersive readout technique in the strong-coupling regime.",1906.00765v1 2019-07-22,On the nature of the resonant drag instability of dust streaming in protoplanetary disc,"The recently discovered resonant drag instability (RDI) of dust streaming in protoplanetary disc is considered as the mode coupling of subsonic gas-dust mixture perturbations. This mode coupling is coalescence of two modes with nearly equal phase velocities: inertial wave (IW) having positive energy and a streaming dust wave (SDW) having negative energy as measured in the frame of gas environment being at rest in vertical hydrostatic equilibrium. SDW is a trivial mode produced by the bulk streaming of dust, which transports perturbations of dust density. In this way, settling combined with radial drift of the dust makes possible coupling of SDW with IW and the onset of the instability. In accordance with the concept of the mode coupling, RDI growth rate is proportional to the square root of the coupling term of the dispersion equation, which itself is proportional to mass fraction of dust, $f\ll 1$. This clarifies why RDI growth rate $\propto f^{1/2}$. When SDW has positive energy, its resonance with IW provides an avoided crossing instead of the mode coupling. In the high wavenumber limit RDI with unbounded growth rate $\propto f^{1/3}$ is explained by the triple mode coupling, which is coupling of SDW with two IW. It coexists with a new quasi-resonant instability accompanied by bonding of two oppositely propagating low-frequency IW. The mode coupling does not exist for dust streaming only radially in a disc. In this case RDI is provided by the obscured mechanism associated with the inertia of solids.",1907.09626v1 2020-03-02,Octagon at finite coupling,"We study a special class of four-point correlation functions of infinitely heavy half-BPS operators in planar N=4 SYM which admit factorization into a product of two octagon form factors. We demonstrate that these functions satisfy a system of nonlinear integro-differential equations which are powerful enough to fully determine their dependence on the 't Hooft coupling and two cross ratios. At weak coupling, solution to these equations yields a known series representation of the octagon in terms of ladder integrals. At strong coupling, we develop a systematic expansion of the octagon in the inverse powers of the coupling constant and calculate accompanying expansion coefficients analytically. We examine the strong coupling expansion of the correlation function in various kinematical regions and observe a perfect agreement both with the expected asymptotic behavior dictated by the OPE and with results of numerical evaluation. We find that, surprisingly enough, the strong coupling expansion is Borel summable. Applying the Borel-Pade summation method, we show that the strong coupling expansion correctly describes the correlation function over a wide region of the 't Hooft coupling.",2003.01121v4 2020-03-16,Efficient Statistical Model for Predicting Electromagnetic Wave Distribution in Coupled Enclosures,"The Random Coupling Model (RCM) has been successfully applied to predicting the statistics of currents and voltages at ports in complex electromagnetic (EM) enclosures operating in the short wavelength limit. Recent studies have extended the RCM to systems of multi-mode aperture-coupled enclosures. However, as the size (as measured in wavelengths) of a coupling aperture grows, the coupling matrix used in the RCM increases as well, and the computation becomes more complex and time-consuming. A simple Power Balance Model (PWB) can provide fast predictions for the \textit{averaged} power density of waves inside electrically-large systems for a wide range of cavity and coupling scenarios. However, the important interference induced fluctuations of the wavefield retained in the RCM is absent in PWB. Here we aim to combine the best aspects of each model to create a hybrid treatment and study the EM fields in coupled enclosure systems. The proposed hybrid approach provides both mean and fluctuation information of the EM fields without the full computational complexity of coupled-cavity RCM. We compare the hybrid model predictions with experiments on linear cascades of over-moded cavities. We find good agreement over a set of different loss parameters and for different coupling strengths between cavities. The range of validity and applicability of the hybrid method are tested and discussed.",2003.07942v3 2020-08-27,Electroweak Couplings of the Higgs Boson at a Multi-TeV Muon Collider,"We estimate the expected precision at a multi-TeV muon collider for measuring the Higgs boson couplings with electroweak gauge bosons, $HVV$ and $HHVV\ (V=W^\pm,Z)$, as well as the trilinear Higgs self-coupling $HHH$. At very high energies both single and double Higgs productions rely on the vector-boson fusion (VBF) topology. The outgoing remnant particles have a strong tendency to stay in the very forward region, leading to the configuration of the ""inclusive process"" and making it difficult to isolate $ZZ$ fusion events from the $WW$ fusion. In the single Higgs channel, we perform a maximum likelihood analysis on $HWW$ and $HZZ$ couplings using two categories: the inclusive Higgs production and the 1-muon exclusive signal. In the double Higgs channel, we consider the inclusive production and study the interplay of the trilinear $HHH$ and the quartic $VVHH$ couplings, by utilizing kinematic information in the invariant mass spectrum. We find that at a centre-of-mass energy of 10 TeV (30 TeV) with an integrated luminosity of 10 ab$^{-1}$ (90 ab$^{-1}$), one may reach a 95\% confidence level sensitivity of 0.073\% (0.023\%) for $WWH$ coupling, 0.61\% (0.21\%) for $ZZH$ coupling, 0.62\% (0.20\%) for $WWHH$ coupling, and 5.6\% (2.0\%) for $HHH$ coupling. For dim-6 operators contributing to the processes, these sensitivities could probe the new physics scale $\Lambda$ in the order of $1-10$ ($2-20$) TeV at a 10 TeV (30 TeV) muon collider.",2008.12204v1 2020-08-28,Double Happiness: Enhancing the Coupled Gains of L-lag Coupling via Control Variates,"The recently proposed L-lag coupling for unbiased Markov chain Monte Carlo (MCMC) calls for a joint celebration by MCMC practitioners and theoreticians. For practitioners, it circumvents the thorny issue of deciding the burn-in period or when to terminate an MCMC sampling process, and opens the door for safe parallel implementation. For theoreticians, it provides a powerful tool to establish elegant and easily estimable bounds on the exact error of an MCMC approximation at any finite number of iterates. A serendipitous observation about the bias-correcting term leads us to introduce naturally available control variates into the L-lag coupling estimators. In turn, this extension enhances the coupled gains of L-lag coupling, because it results in more efficient unbiased estimators, as well as a better bound on the total variation error of MCMC iterations, albeit the gains diminish as L increases. Specifically, the new upper bound is theoretically guaranteed to never exceed the one given previously. We also argue that L-lag coupling represents a coupling for the future, breaking from the coupling-from-the-past type of perfect sampling, by reducing the generally unachievable requirement of being perfect to one of being unbiased, a worthwhile trade-off for ease of implementation in most practical situations. The theoretical analysis is supported by numerical experiments that show tighter bounds and a gain in efficiency when control variates are introduced.",2008.12662v4 2020-10-11,Measurement of Higgs-boson self-coupling with single-Higgs and double-Higgs production channels,"The trilinear self-coupling can be measured directly using the Higgs-boson-pair production cross section, or indirectly through the measurement of single-Higgs-boson production and decay modes. In fact, at next-to-leading order in electroweak interaction, the Higgs-decay partial widths and the cross sections of the main single-Higgs production processes depend on the Higgs-boson self-coupling via weak loops. Measurements of $\kappa_\lambda$, i.e. the rescaling of the trilinear Higgs self-coupling, are presented in this dissertation. Results are obtained exploiting proton-proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector in 2015, 2016 and 2017, corresponding to a luminosity of up to 79.8 fb$^{-1}$. Constraints on the Higgs self-coupling are presented considering the most sensitive double-Higgs channels (HH), $b\bar{b}\tau^+\tau^-$, $b\bar{b}\gamma\gamma$ and $b\bar{b}b\bar{b}$, considering single-Higgs (H) production modes, $ggF$, $VBF$, $ZH$, $WH$ and $t\bar{t}H$, together with $WW^*$, $ZZ^*$, $\tau^+\tau^-$, $\gamma \gamma$ and $b\bar{b}$ decay channels, and combining the aforementioned analyses (H+HH) to improve the sensitivity on $\kappa_\lambda$. Under the assumption that new physics affects only the Higgs-boson self-coupling, the combined H+HH best-fit value of the coupling modifier is: $\kappa_\lambda = 4.6^{+3.2}_{-3.8}$, excluding values outside the interval $-2.3<\kappa_\lambda<10.3$ at 95% confidence level. Results with less stringent assumptions are also provided, decoupling the Higgs-boson self-coupling and the other Standard Model couplings. The final results of this thesis provide the most stringent constraint on $\kappa_\lambda$ from experimental measurements to date.",2010.05252v1 2020-10-14,Weakly coupled alternating $S=1/2$ chains in the distorted honeycomb lattice compound Na$_2$Cu$_2$TeO$_6$,"Spin-1/2 chains with alternating antiferromagnetic (AF) and ferromagnetic (FM) couplings exhibit quantum entanglement like the integer-spin Haldane chains and might be similarly utilized for quantum computations. Such alternating AF-FM chains have been proposed to be realized in the distorted honeycomb-lattice compound Na$_2$Cu$_2$TeO$_6$, but to confirm this picture a comprehensive understanding of the exchange interactions including terms outside of the idealized model is required. Here we employ neutron scattering to study the spin dynamics in Na$_2$Cu$_2$TeO$_6$ and accurately determine the coupling strengths through the random phase approximation and density functional theory (DFT) approaches. We find the AF and FM intrachain couplings are the dominant terms in the spin Hamiltonian, while the interchain couplings are AF but perturbative. This hierarchy in the coupling strengths and the alternating signs of the intrachain couplings can be understood through their different exchange paths. Our results establish Na$_2$Cu$_2$TeO$_6$ as a weakly-coupled alternating AF-FM chain compound and reveal the robustness of the gapped ground state in alternating chains under weak interchain couplings.",2010.06745v2 2020-10-30,Emulating the local Kuramoto model with an injection-locked photonic crystal laser array,"The Kuramoto model is a mathematical model for describing the collective synchronization phenomena of coupled oscillators. We theoretically demonstrate that an array of coupled photonic crystal lasers emulates the Kuramoto model with non-delayed nearest-neighbor coupling (the local Kuramoto model). Our novel strategy employs indirect coupling between lasers via additional cold cavities. By installing cold cavities between laser cavities, we avoid the strong coupling of lasers and realize ideal mutual injection-locking with effective non-delayed dissipative coupling. First, after discussing the limit cycle interpretation of laser oscillation, we demonstrate the synchronization of two indirectly coupled lasers by numerically simulating coupled-mode equations. Second, by performing a phase reduction analysis, we show that laser dynamics in the proposed device can be mapped to the local Kuramoto model. Finally, we briefly demonstrate that a chain of indirectly coupled photonic crystal lasers actually emulates the one-dimensional local Kuramoto chain. We also argue that our proposed structure, which consists of periodically aligned cold cavities and laser cavities, will best be realized by using state-of-the-art buried multiple quantum well photonic crystals.",2010.16236v3 2020-11-10,Alignment of Yukawa couplings in two Higgs doublet models,"We study the alignment of Yukawa couplings in the framework of general two Higgs doublet models (2HDMs) considering a scenario in which the lightest neutral Higgs boson is purely CP even while the two heavier neutral Higgs bosons are allowed to mix in the presence of nontrivial CP-violating phases in the Higgs potential. Identifying the lightest neutral Higgs boson as the 125 GeV one discovered at the LHC, we find that the alignment of Yukawa couplings without decoupling could be easily achieved in the type-I 2HDM with no much conflict with the current LHC Higgs precision data. Otherwise, we observe that the Yukawa couplings of the lightest Higgs boson could decouple much slowly compared to the Higgs coupling to a pair of massive vector bosons and they significantly deviate from the corresponding SM values even when the deviation of the Higgs to vector boson coupling is below the percent level. On the other hand, independently of 2HDM type and regardless of decoupling, we find a wrong-sign alignment limit of the Yukawa couplings in which the Yukawa couplings to the down-type quarks and/or those to the charged leptons are equal in strength but opposite in sign to the corresponding SM ones. The magnitude and sign of the up-type quark Yukawa couplings remain the same as in the SM. Accordingly, in this limit, all four types of 2HDMs are viable against the LHC Higgs precision data.",2011.04978v1 2020-11-18,How important are the residual nonadiabatic couplings for an accurate simulation of nonadiabatic quantum dynamics in a quasidiabatic representation?,"Diabatization of the molecular Hamiltonian is a standard approach to removing the singularities of nonadiabatic couplings at conical intersections of adiabatic potential energy surfaces. In general, it is impossible to eliminate the nonadiabatic couplings entirely -- the resulting ""quasidiabatic"" states are still coupled by smaller but nonvanishing residual nonadiabatic couplings, which are typically neglected. Here, we propose a general method for assessing the validity of this potentially drastic approximation by comparing quantum dynamics simulated either with or without the residual couplings. To make the numerical errors negligible to the errors due to neglecting the residual couplings, we use the highly accurate and general eighth-order composition of the implicit midpoint method. The usefulness of the proposed method is demonstrated on nonadiabatic simulations in the cubic Jahn--Teller model of nitrogen trioxide and in the induced Renner--Teller model of hydrogen cyanide. We find that, depending on the system, initial state, and employed quasidiabatization scheme, neglecting the residual couplings can result in wrong dynamics. In contrast, simulations with the exact quasidiabatic Hamiltonian, which contains the residual couplings, always yield accurate results.",2011.09191v3 2021-03-22,Dipole Radiation and Beyond from Axion Stars in Electromagnetic Fields,"We investigate the production of photons from coherently oscillating, spatially localized clumps of axionic fields (oscillons and axion stars) in the presence of external electromagnetic fields. We delineate different qualitative behaviour of the photon luminosity in terms of an effective dimensionless coupling parameter constructed out of the axion-photon coupling, and field amplitude, oscillation frequency and radius of the axion star. For small values of this dimensionless coupling, we provide a general analytic formula for the dipole radiation field and the photon luminosity per solid angle, including a strong dependence on the radius of the configuration. For moderate to large coupling, we report on a non-monotonic behavior of the luminosity with the coupling strength in the presence of external magnetic fields. After an initial rise in luminosity with the coupling strength, we see a suppression (by an order of magnitude or more compared to the dipole radiation approximation) at moderately large coupling. At sufficiently large coupling, we find a transition to a regime of exponential growth of the luminosity due to parametric resonance. We carry out 3+1 dimensional lattice simulations of axion electrodynamics, at small and large coupling, including non-perturbative effects of parametric resonance as well as backreaction effects when necessary. We also discuss medium (plasma) effects that lead to resonant axion to photon conversion, relevance of the coherence of the soliton, and implications of our results in astrophysical and cosmological settings.",2103.12082v1 2021-04-20,Artificial out-of-plane Ising antiferromagnet on the kagome lattice with very small further neighbour couplings,"Despite their simple formulation, short range classical antiferromagnetic Ising models on frustrated lattices give rise to exotic phases of matter, in particular due to their macroscopic ground state degeneracy. Recent experiments on artificial spin systems comprising arrays of chirally coupled nanomagnets provide a significant strengthening of the nearest neighbour couplings compared to systems with dipolar-coupled nanomagnets. This opens the way to design artificial spin systems emulating Ising models with nearest neighbour couplings. In this paper, we compare the results of an extensive investigation with tensor network and Monte Carlo simulations of the nearest- and further-neighbour ($J_1-J_2-J_{3||}$) kagome Ising antiferromagnet with the experimental spin-spin correlations of a kagome lattice of chirally coupled nanomagnets. Even though the ratios between the further neighbour couplings and the nearest neighbour coupling estimated from micromagnetic simulations are much smaller than for dipolar-coupled nanomagnets, we show that they still play an essential role in the selection of the correlations.",2104.09927v3 2021-07-14,Exciton-photon complexes and dynamics in the concurrent strong-weak coupling regime of singular site-controlled cavity quantum electrodynamics,"We investigate the exciton complexes photoluminescence, dynamics and photon statistics in the concurrent strong weak coupling regime in our unique site controlled singular inverted pyramidal InGaAs/GaAs quantum dots photonic crystal cavities platform. Different from a clear boundary between strong and weak QD cavity coupling, we demonstrate the strong and weak coupling can coexist dynamically, as a form of intermediate regime mediated by phonon scattering. The detuning dependent microphotoluminescence spectrum reveals concurrence of exciton cavity polariton mode avoided crossing, as a signature of Rabi doublet of the strong coupled system, the blue shifting of coupled exciton cavity mode energy near zero detuning ascribed to the formation of collective states mediated by phonon assisted coupling, and their partial out of synchronization linewidth narrowing linked to their mixed behavior. By detailing the optical features of strongly confined exciton-photon complexes and the quantum statistics of coupled cavity photons, we reveal the dynamics and antibunching/bunching photon statistical signatures of the concurrent strong weak intermediate coupled system at near zero-detuning. This study suggests our device has potential for new and subtle cavity quantum electrodynamical phenomena, cavity enhanced indistinguishable single photon generation, and cluster state generation via the exciton-photon complexes for quantum networks.",2107.06515v1 2021-07-16,A Two-Frequency-Two-Coupling model of coupled oscillators,"We considered the phase coherence dynamics in a Two-Frequency and Two-Coupling (TFTC) model of coupled oscillators, where coupling strength and natural oscillator frequencies for individual oscillators may assume one of two values (positive/negative). The bimodal distributions for the coupling strengths and frequencies are either correlated or uncorrelated. To study how correlation affects phase coherence, we analyzed the TFTC model by means of numerical simulations and exact dimensional reduction methods allowing to study the collective dynamics in terms of local order parameters. The competition resulting from distributed coupling strengths and natural frequencies produces nontrivial dynamic states. For correlated disorder in frequencies and coupling strengths, we found that the entire oscillator population splits into two subpopulations, both phase-locked (Lock-Lock) or one phase-locked, and the other drifting (Lock-Drift), where the mean-fields of the sub-populations maintain a constant non-zero phase difference. For uncorrelated disorder, we found that the oscillator population may split into four phase-locked subpopulations, forming phase-locked pairs which are either mutually frequency-locked (Stable Lock-Lock-Lock-Lock) or drifting (Breathing Lock-Lock-Lock-Lock), thus resulting in a periodic motion of the global synchronization level. Finally, we found for both types of disorder that a state of Incoherence exists; however, for correlated coupling strengths and frequencies, incoherence is always unstable, whereas it is only neutrally stable for the uncorrelated case. Numerical simulations performed on the model show good agreement with the analytic predictions. The simplicity of the model promises that real-world systems can be found which display the dynamics induced by correlated/uncorrelated disorder.",2107.07897v2 2021-08-26,Ab initio linear-response approach to vibro-polaritons in the cavity Born-Oppenheimer approximation,"Recent years have seen significant developments in the study of strong light-matter coupling including the control of chemical reactions by altering the vibrational normal modes of molecules. In the vibrational strong coupling regime the normal modes of the system become hybrid modes which mix nuclear, electronic, and photonic degrees of freedom. First principles methods capable of treating light and matter degrees of freedom on the same level of theory are an important tool in understanding such systems. In this work, we develop and apply a generalized force constant matrix approach to the study of mixed vibration-photon (vibro-polariton) states of molecules based on the cavity Born-Oppenheimer approximation and quantum-electrodynamical density-functional theory. With this method vibro-polariton modes and infrared spectra can be computed via linear response techniques analogous to those widely used for conventional vibrations and phonons. We also develop an accurate model that highlights the consistent treatment of cavity coupled electrons in the vibrational strong coupling regime. These electronic effects appear as new terms previously disregarded by simpler models. This effective model also allows for an accurate extrapolation of single and two molecule calculations to the collective strong coupling limit of hundreds of molecules. We benchmark these approaches for single and many CO$_2$ molecules coupled to a single photon mode and the iron-pentacarbonyl Fe(CO)$_5$ molecule coupled to a few photon modes. Our results are the first ab-initio results for collective vibrational strong coupling effects. This framework for efficient computations of vibro-polaritons paves the way to a systematic description and improved understanding of the behavior of chemical systems in vibrational strong coupling.",2108.11564v1 2021-08-30,Partitioned Coupling vs. Monolithic Block-Preconditioning Approaches for Solving Stokes-Darcy Systems,"We consider the time-dependent Stokes-Darcy problem as a model case for the challenges involved in solving coupled systems. Keeping the model, its discretization, and the underlying numerics for the subproblems in the free-flow domain and the porous medium constant, we focus on different solver approaches for the coupled problem. We compare a partitioned coupling approach using the coupling library preCICE with a monolithic block-preconditioned one that is tailored to different formulations of the problem. Both approaches enable the reuse of already available iterative solvers and preconditioners, in our case, from the DuMux framework. Our results indicate that the approaches can yield performance and scalability improvements compared to using direct solvers: Partitioned coupling is able to solve large problems faster if iterative solvers with suitable preconditioners are applied for the subproblems. The monolithic approach shows even stronger requirements on preconditioning, as standard simple solvers fail to converge. Our monolithic block preconditioning yields the fastest runtimes for large systems, but they vary strongly with the preconditioner configuration. Interestingly, using a specialized Uzawa preconditioner for the Stokes subsystem leads to overall increased runtimes compared to block preconditioners utilizing a more general algebraic multigrid. This highlights that optimizing for the non-coupled cases does not always pay off.",2108.13229v1 2021-09-18,Quantum transfer through small networks coupled to phonons: effects of topology vs phonons,"Particle or energy transfer through quantum networks is determined by network topology and couplings to environments. This study examines the combined effect of topology and external couplings on the efficiency of directional quantum transfer through quantum networks. We consider a microscopic model of qubit networks coupled to external vibrations by Holstein and Peierls couplings. By treating the positions of the network sites and the site-dependent phonon frequencies as independent variables, we determine the Hamiltonian parameters corresponding to minimum transfer time by Bayesian optimization. The results show that Holstein couplings may accelerate transfer through sub-optimal network configurations but cannot accelerate quantum dynamics beyond the limit of the transfer time in an optimal phonon-free configuration. By contrast, Peierls couplings distort the optimal networks to accelerate quantum transfer through configurations with less than six sites. However, the speed-up offered by Peierls couplings decreases with the network size and disappears for networks with more than seven sites. For networks with seven sites or more, Peierls couplings distort the optimal network configurations and change the mechanism of quantum transfer but do not affect the lower limit of the transfer time. The machine-learning approach demonstrated here can be applied to determine quantum speed limits in other applications.",2109.08851v1 2022-01-21,Frequency-dependent Sternheimer linear-response formalism for strongly coupled light-matter systems,"The rapid progress in quantum-optical experiments especially in the field of cavity quantum electrodynamics and nanoplasmonics, allows to substantially modify and control chemical and physical properties of atoms, molecules and solids by strongly coupling to the quantized field. Alongside such experimental advances has been the recent development of ab-initio approaches such as quantum electrodynamical density-functional theory (QEDFT) that is capable of describing these strongly coupled systems from first-principles. To investigate response properties of relatively large systems coupled to a wide range of photon modes, ab-initio methods that scale well with system size become relevant. In light of this, we extend the linear-response Sternheimer approach within the framework of QEDFT to efficiently compute excited-state properties of strongly coupled light-matter systems. Using this method, we capture features of strong light-matter coupling both in the dispersion and absorption properties of a molecular system strongly coupled to the modes of a cavity. We exemplify the efficiency of the Sternheimer approach by coupling the matter system to the continuum of an electromagnetic field. We observe changes in the spectral features of the coupled system as Lorentzian line shapes turn into Fano resonances when the molecule interacts strongly with the continuum of modes. This work provides an alternative approach for computing efficiently excited-state properties of large molecular systems interacting with the quantized electromagnetic field.",2201.08734v1 2022-02-24,Engineering symmetry-selective couplings of a superconducting artificial molecule to microwave waveguides,"Tailoring the decay rate of structured quantum emitters into their environment opens new avenues for nonlinear quantum optics, collective phenomena, and quantum communications. Here we demonstrate a novel coupling scheme between an artificial molecule comprising two identical, strongly coupled transmon qubits, and two microwave waveguides. In our scheme, the coupling is engineered so that transitions between states of the same (opposite) symmetry, with respect to the permutation operator, are predominantly coupled to one (the other) waveguide. The symmetry-based coupling selectivity, as quantified by the ratio of the coupling strengths, exceeds a factor of 30 for both the waveguides in our device. In addition, we implement a two-photon Raman process activated by simultaneously driving both waveguides, and show that it can be used to coherently couple states of different symmetry in the single-excitation manifold of the molecule. Using that process, we implement frequency conversion across the waveguides, mediated by the molecule, with efficiency of about 95%. Finally, we show that this coupling arrangement makes it possible to straightforwardly generate spatially-separated Bell states propagating across the waveguides. We envisage further applications to quantum thermodynamics, microwave photodetection, and photon-photon gates.",2202.12209v1 2022-06-03,Quantum coherent feedback control with photons,"The purpose of this paper is to study two-photon dynamics induced by the coherent feedback control of a cavity quantum electrodynamics (cavity-QED) system coupled to a waveguide. In this set-up, the two-level system in the cavity can work as a photon source, and the photon emitted into the waveguide can re-interact with the cavity-QED system many times after the transmission and reflection in the waveguide, during which the feedback can tune the number of the photons in and out of the cavity. We analyze the dynamics of two-photon processes in this coherent feedback network in two scenarios: the continuous mode coupling scheme and the discrete periodic mode coupling scheme between the waveguide and cavity. The difference of these coupling schemes is due to their relative scales and the number of semi-transparent mirrors for coupling. Specifically, in the continuous mode coupling scheme, the generation of two-photon states is influenced by the length of the feedback loop by the waveguide and the coupling strength between the waveguide and the cavity-QED system. By tuning the length of the waveguide and the coupling strength, we are able to generate two-photon states efficiently. In the discrete periodic mode coupling scheme, the Rabi oscillation in the cavity can be stabilized and there are no notable two-photon states in the waveguide.",2206.01445v2 2022-07-08,"Probing non-standard $HVV (V=W, Z)$ couplings in single Higgs production at future electron-proton collider","The couplings of the Higgs boson ($H$) with massive gauge bosons of weak interaction ($V= W, Z$), can be probed in single Higgs boson production at the proposed future Large Hadron-Electron Collider (LHeC). In the collision of an electron with a proton, single Higgs production takes place via so-called charged-current ($e^-p \to \nu_e H j$) and neutral-current ($e^-p \to e^-H j$) processes. We explore the potential of the azimuthal angle correlation between the forward jet and scattered neutrino or electron in probing the non-standard $HVV$ couplings at the collider center-of-mass energy of $\sqrt{s} \approx 1.3$~TeV. We choose the most general modifications (of $CP$-even and $CP$-odd nature) to these couplings due to new physics effects beyond the standard model. We derive exclusion limits on new physics parameters of $HVV$ couplings as a function of integrated luminosity at $95\%$ C.L. using the azimuthal angular correlations in charged- and neutral-current processes. We find that using 1000 $fb^{-1}$ data, the standard model-like new physics parameters in $HWW$ and $HZZ$ couplings can be constrained with accuracies of $4\%$ and $15\%$, respectively. The least constrained $CP$-even parameters of $HWW$ coupling can be as large as 0.04, while those of $HZZ$ coupling can have values around 0.31. Allowed values of $CP$-odd parameters in $HWW$ and $HZZ$ couplings are found to be around 0.14 and 0.34, respectively. We also study changes in the allowed values of non-trivial new physics parameters in the presence of other parameters.",2207.03862v1 2022-07-11,Quantum topology in the ultrastrong coupling regime,"The coupling between two or more objects can generally be categorized as strong or weak. In cavity quantum electrodynamics for example, when the coupling strength is larger than the loss rate the coupling is termed strong, and otherwise it is dubbed weak. Ultrastrong coupling, where the interaction energy is of the same order of magnitude as the bare energies of the uncoupled objects, presents a new paradigm for quantum physics and beyond. As a consequence profound changes to well established phenomena occur, for instance the ground state in an ultrastrongly coupled system is not empty but hosts virtual excitations due to the existence of processes which do not conserve the total number of excitations. The implications of ultrastrong coupling for quantum topological systems, where the number of excitations are typically conserved, remain largely unknown despite the great utility of topological matter. Here we reveal how the delicate interplay between ultrastrong coupling and topological states manifests in a one-dimensional array. We study theoretically a dimerized chain of twolevel systems within the ultrastrong coupling regime, where the combined saturation and counter-rotating terms in the Hamiltonian are shown to play pivotal roles in the rich, multi-excitation effective bandstructure. In particular, we uncover unusual topological edge states, we introduce a flavour of topological state which we call an anti-edge state, and we reveal the remarkable geometric-dependent renormalizations of the quantum vaccum. Taken together, our results provide a route map for experimentalists to characterize and explore a prototypical system in the emerging field of ultrastrong quantum topology.",2207.04952v1 2022-08-18,Dynamics of quantum soliton in Lee-Huang-Yang spin-orbit coupled Bose-Einstein condensates,"We present the numerical results of the structure and dynamics of the self-bound ground state arising solely because of the presence of beyond mean field quantum fluctuation in spin-orbit coupled binary Bose-Einstein condensates in one dimension. Depending upon spin-obit (SO) and Rabi couplings, we observe that the ground state exhibits either quantum-bright (plane) or quantum-stripe soliton nature. We find an analytical soliton solution for non-zero SO coupling that matches quite well with the numerical results. Further, we investigate the dynamical stability of these solitons by adopting three protocols, such as (i) adding initial velocity to each component, (ii) quenching the SO and Rabi coupling parameters at initial and finite time, and (iii) allowing collision between the two spin-components by giving equal and opposite direction velocity to them. Many interesting dynamical features of the solitons, like, multi-fragmented, repelling, and breathing in time and space-time, are observed. For given Rabi coupling frequency, the breathing frequency of the soliton increases upon the increase in SO coupling, attaining a maximum at the critical SO coupling where the phase transition from the bright to stripe soliton occurs. We observe that the maximum breathing frequency exhibits power law dependence on the Rabi coupling frequency with an exponent $\sim 0.16$.",2208.08777v2 2022-09-03,Homogenization of discrete mesoscale model of concrete for coupled mass transport and mechanics by asymptotic expansion,"Mass transport phenomenon in concrete structures is strongly coupled with their mechanical behavior. The first coupling fabric is the Biot's theory according to which fluid pressure interacts with solid stress state and volumetric deformation rate of the solid induces changes in fluid pressure. Another coupling mechanism emerges with cracks which serve as channels for the fluid to flow through them and provide volume for fluid storage. Especially the second coupling mechanism presents a challenge for numerical modeling as it requires detailed knowledge about cracking process. Discrete mesoscale mechanical models coupled with mass transport offer simple and robust way to solve the problem. On the other hand, however, they are computationally demanding. In order to reduce this computational burden, the present paper applies the asymptotic expansion homogenization technique to the coupled problem to deliver (i) continuous and homogeneous description of the macroscopic problem which can be easily solved by the finite element method, (ii) discrete and heterogeneous mesoscale problem in the periodic setup attached to each integration point of the macroscale along with (iii) equations providing communication between these two scales. The transient terms appear at the macroscale only, as well as the Biot's coupling terms. The coupling through cracking is treated at the mesoscale by changing conductivity of the conduit elements according to the mechanical solution, otherwise the two mesoscale steady state problems are decoupled and can be therefore solved in a sequence. This paper presents verification studies showing performance of the homogenized solution.",2209.01419v1 2022-09-30,Generation and transfer of entangled states between two connected microtoroidal cavities: analysis of different types of coupling,"We investigate the generation and transfer of entangled states between two coupled microtoroidal cavities considering two different types of couplings, namely i) via a bridge qubit and ii) via evanescent fields. The cavities support two counter-propagating whispering-gallery modes (WGMs) that may also interact with each other. We firstly show that it is possible to transfer, with high fidelity, a maximally entangled state between the two modes of the first cavity (cavity 1) to the two modes of the second cavity (cavity 2), independently of the type of coupling. Interesting differences, though, arise concerning the generation of entangled states from initial product states; if the cavities are coupled via a bridge qubit, we show that it is possible to generate a 4-partite entangled state involving all four cavity modes. On the other hand, contrarily to what happens in the qubit coupling case, it is possible to generate bipartite maximally entangled states between modes of different cavities from initial separable states for cavities coupled by evanescent waves. Besides, we show that different entangled states between the propagating and counter-propagating modes of distinct cavities may be generated by tuning the interaction between modes belonging to the same cavity (intra-cavity couplings). Again, this is possible only for the couplings via evanescent waves. For the completion of our work, we discuss the effects of losses on the dynamics of the system.",2209.15638v2 2022-12-26,Upper bounds on collective light-matter coupling strength with plasmonic meta-atoms,"Ultrastrong coupling between optical and material excitations is a distinct regime of electromagnetic interaction that enables a variety of intriguing physical phenomena. Traditional ways to ultrastrong light-matter coupling involve the use of some sorts of quantum emitters, such as organic dyes, quantum wells, superconducting artificial atoms, or transitions of two-dimensional electron gases. Often, reaching the ultrastrong coupling domain requires special conditions, including high vacuum, strong magnetic fields, and extremely low temperatures. Recent report indicate that a high degree of light-matter coupling can be attained at ambient conditions with plasmonic meta-atoms -- artificial metallic nanostructures that replace quantum emitters. Yet, the fundamental limits on the coupling strength imposed on such systems have not been identified. Here, using a Hamiltonian approach we theoretically analyze the formation of polaritonic states and examine the upper limits of the collective plasmon-photon coupling strength in a number of dense assemblies of plasmonic meta-atoms. Starting off with spheres, we identify the universal upper bounds on the normalized collective coupling strength $g/\omega_0$ between ensembles of plasmonic meta-atoms and free-space photons. Next, we examine spheroidal metallic meta-atoms and show that a strongly elongated meta-atom is the optimal geometry for attaining the highest value of the collective coupling strength in the array of meta-atoms. The results could be valuable for the field of polaritonics studies, quantum technology, and modifying material properties.",2212.13192v1 2023-02-15,Magnetically-dressed CrSBr exciton-polaritons in ultrastrong coupling regime,"The strong coupling between photons and matter excitations such as excitons, phonons, and magnons is of central importance in the study of light-matter interactions. Bridging the flying and stationary quantum states, the strong light-matter coupling enables the coherent transmission, storage, and processing of quantum information, which is essential for building photonic quantum networks. Over the past few decades, exciton-polaritons have attracted substantial research interest due to their half-light-half-matter bosonic nature. Coupling exciton-polaritons with magnetic orders grants access to rich many-body phenomena, but has been limited by the availability of material systems that exhibit simultaneous exciton resonances and magnetic ordering. Here we report magnetically-dressed microcavity exciton-polaritons in the van der Waals antiferromagnetic (AFM) semiconductor CrSBr coupled to a Tamm plasmon microcavity. Angle-resolved spectroscopy reveals an exceptionally high exciton-polariton coupling strength attaining 169 meV, demonstrating ultrastrong coupling that persists up to room temperature. Temperature-dependent exciton-polariton spectroscopy senses the magnetic order change from AFM to paramagnetism in CrSBr, confirming its magnetic nature. By applying an out-of-plane magnetic field, an effective tuning of the polariton energy is further achieved while maintaining the ultrastrong exciton-photon coupling strength, which is attributed to the spin canting process that modulates the interlayer exciton interaction. Our work proposes a hybrid quantum platform enabled by robust opto-electronic-magnetic coupling, promising for quantum interconnects and transducers.",2302.07616v1 2023-02-16,A Superdirective Beamforming Approach with Impedance Coupling and Field Coupling for Compact Antenna Arrays,"In most multiple-input multiple-output (MIMO) communication systems, the antenna spacing is generally no less than half a wavelength. It helps to reduce the mutual coupling and therefore facilitate the system design. The maximum array gain equals the number of antennas in this settings. However, when the antenna spacing is made very small, the array gain of a compact array can be proportional to the square of the number of antennas - a value much larger than the traditional array. To achieve this so-called ``superdirectivity"" however, the calculation of the excitation coefficients (beamforming vector) is known to be a challenging problem. In this paper, we address this problem with a novel double coupling-based superdirective beamforming method. In particular, we categorize the antenna coupling effects to impedance coupling and field coupling. By characterizing these two coupling in model, we derive the beamforming vector for superdirective arrays. In order to obtain the field coupling matrix, we propose a spherical wave expansion approach, which is effective in both simulations and realistic scenarios. Moreover, a prototype of the independently controlled superdirective antenna array is developed. Full-wave electromagnetic simulations and real-world experiments validate the effectiveness of our proposed approaches, and superdirectivity is achieved in reality by a compact array with 4 and 5 dipole antennas.",2302.08203v1 2023-04-06,Cyclic quantum engines enhanced by strong bath coupling,"While strong system-bath coupling produces rich and interesting phenomena, applications to quantum thermal engines have been so far pointing mainly at detrimental effects. The delicate trade-off between efficiency loss due to strong coupling and power increase due to faster equilibration, while acknowledged, remained largely unexplored owing to the challenge of assessing precisely the equilibration time. Here, we overcome this obstacle by exploiting exact numerical simulations based on the hierarchical equations of motion (HEOM) formalism. We show that a quantum Otto cycle can perform better at strong (but not ultrastrong) coupling in that the product of the efficiency times the output power is maximized in this regime. In particular, we show that strong coupling allows one to obtain engines with larger efficiency than their weakly coupled counterparts, while sharing the same output power. Conversely, one can design strongly coupled engines with larger power than their weakly coupled counterparts, while sharing the same efficiency. Overall, our results provide situations where strong coupling can directly enhance the performance of thermodynamic operations, re-enforcing the importance of studying quantum thermal engines beyond standard configurations.",2304.03267v3 2023-06-20,Spin-orbit interaction enabled electronic Raman scattering from charge collective modes,"Electronic Raman scattering in the fully symmetric channel couples to the charge excitations in the system, including the plasmons. However, the plasmon response has a spectral weight of $\sim q^2$, where $q$, the momentum transferred by light, is small. In this work, we show that in inversion symmetry broken systems where Rashba type spin-orbit coupling affects the states at the Fermi energy (which is a known low energy effect) as well as the transition elements to other states (a high energy effect), there is an additional coupling of the plasmons to the Raman vertex, even at zero momentum transfer, that results in a spectral weight that is proportional to the spin-orbit coupling. The high energy effect is due to the breaking of SU(2) spin invariance in the spin-flip transitions to the intermediate state. We present a theory for this coupling near the resonant regime of Raman scattering and show that in giant Rashba systems it can dominate over the conventional $q^2$ weighted coupling. We also provide experimental support along with a symmetry based justification for this spin-mediated coupling by identifying a prominent c-axis plasmon peak in the fully symmetric channel of the resonant Raman spectrum of the giant Rashba material BiTeI. This new coupling could lead to novel ways of manipulating coherent charge excitations in inversion-broken systems. This process is also relevant for spectroscopic studies in ultrafast spectroscopies, certain driven Floquet systems and topologically non-trivial phases of matter where strong inversion-breaking spin-orbit coupling plays a role.",2306.11240v2 2023-09-20,Soft-gluon effective coupling: perturbative results and the large-nF limit to all orders,"We consider extensions of the soft-gluon effective coupling that generalize the Catani--Marchesini--Webber (CMW) coupling in the context of soft-gluon resummation beyond the next-to-leading logarithmic accuracy. Starting from the probability density of correlated soft emission in d dimensions we introduce a class of soft couplings relevant for resummed QCD calculations of hard-scattering observables. We show that at the conformal point, where the d-dimensional QCD $\beta$ function vanishes, all these effective couplings are equal and they are also equal to the cusp anomalous dimension. We present explicit results in d dimensions for the soft-emission probability density and the soft couplings at the second-order in the QCD coupling $\alpha_s$. In d=4 dimensions we obtain the explicit relation between the soft couplings at ${\cal O}(\alpha_s^3).$ Finally, we study the structure of the soft coupling in the large-$n_F$ limit and we present explicit expressions to all orders in perturbation theory. We also check that, at the conformal point, our large-$n_F$ results agree with the known result of the cusp anomalous dimension.",2309.11584v1 2023-11-01,Cubic and higher-order supergravity couplings for AdS vacua using Exceptional Field Theory,"We show how to use Exceptional Field Theory to efficiently compute $n$-point couplings of all Kaluza-Klein modes for vacua that can be uplifted from maximal gauged supergravities to 10/11 dimensions via a consistent truncation. Via the AdS/CFT correspondence, these couplings encode the $n$-point functions of holographic conformal fields theories. Our methods show that these $n$-point couplings are controlled by the $n$-point invariant of scalar harmonics of the maximally symmetric point of the truncation, allowing us to show that infinitely-many $n$-point couplings vanish for any vacua of the truncation, even though they may be allowed by the remnant symmetry group of the vacua. This gives new results even for the maximally supersymmetric AdS$_5 \times S^5$, AdS$_4 \times S^7$ and AdS$_7 \times S^4$ vacua of string and M-theory, where we prove old conjectures about the vanishing of $n$-point extremal and near-extremal couplings. Focusing in particular on cubic couplings for vacua of 5-dimensional gauged supergravity, we derive explicit universal formulae encoding these couplings for any vacuum within a consistent truncation. We use this to compute known and new couplings involving spin-0, spin-1, spin-2 for the AdS$_5 \times S^5$ vacuum of IIB string theory.",2311.00742v1 2023-11-21,The effective field theory approach to the strong coupling issue in $f(T)$ gravity with a non-minimally coupled scalar field,"The Hamiltonian analysis for $f(T)$ gravity implies the existence of at least one scalar-type degree of freedom (DoF). However, this scalar DoF of $f(T)$ gravity does not manifest in linear perturbations around a cosmological background, which indicates an underlying strong coupling problem. In this work we expand the scope by introducing an extra scalar field non-minimally coupled to $f(T)$ gravity, aiming to address or alleviate the aforementioned strong coupling problem. Employing the effective field theory (EFT) approach, we provide a class of torsional EFT forms up to second order operators, avoiding the Ostrogradsky ghost. To illustrate this phenomenon, we study a simple model and perform a detailed analysis of its linear scalar perturbations. The results demonstrate that the coupling terms in this toy model are necessary to avoid the initial degenerate situation. The complete avoidance of new constraints requires more coupling terms. Once this vanishing scalar DoF starts propagating in cosmological background at linear level, this phenomenon will demand a revisit of the strong coupling issue that arises in $f(T)$ gravity, particularly in the presence of matter coupling.",2311.12645v2 2023-11-27,Quantum Carnot thermal machines re-examined: Definition of efficiency and the effects of strong coupling,"Whether the strong coupling to thermal baths can improve the performance of quantum thermal machines remains an open issue under active debate. Here, we revisit quantum thermal machines operating with the quasi-static Carnot cycle and aim to unveil the role of strong coupling in maximum efficiency. Our analysis builds upon definitions of excess work and heat derived from an exact formulation of the first law of thermodynamics for the working substance, which captures the non-Gibbsian thermal equilibrium state that emerges at strong couplings during quasi-static isothermal processes. These excess definitions differ from conventional ones by an energetic cost for maintaining the non-Gibbsian characteristics. With this distinction, we point out that one can introduce two different yet thermodynamically allowed definitions for efficiency of both the heat engine and refrigerator modes. We dub them excess and hybrid definitions which differ in the way of defining the gain for the thermal machines at strong couplings by either just analyzing the energetics of the working substance or instead evaluating the performance from an external system upon which the thermal machine acts, respectively. We analytically demonstrate that the excess definition predicts that the Carnot limit remains the upper bound for both operation modes at strong couplings, whereas the hybrid one reveals that strong coupling can suppress the maximum efficiency rendering the Carnot limit unattainable. These seemingly incompatible predictions thus indicate that it is imperative to first gauge the definition for efficiency before elucidating the exact role of strong coupling, thereby shedding light on the on-going investigation on strong-coupling quantum thermal machines.",2311.15465v2 2023-12-08,Engineering synthetic gauge fields through the coupling phases in cavity magnonics,"Cavity magnonics, which studies the interaction of light with magnetic systems in a cavity, is a promising platform for quantum transducers, quantum memories, and devices with non-reciprocal behaviour. At microwave frequencies, the coupling between a cavity photon and a magnon, the quasi-particle of a spin wave excitation, is a consequence of the Zeeman interaction between the cavity's magnetic field and the magnet's macroscopic spin. For each photon/magnon interaction, a coupling phase factor exists, but is often neglected in simple systems. However, in ""loop-coupled"" systems, where there are at least as many couplings as modes, the coupling phases become relevant for the physics and lead to synthetic gauge fields. We present experimental evidence of the existence of such coupling phases by considering two spheres made of Yttrium-Iron-Garnet and two different re-entrant cavities. We predict numerically the values of the coupling phases, and we find good agreement between theory and the experimental data. Theses results show that in cavity magnonics, one can engineer synthetic gauge fields, which can be useful for cavity-mediated coupling, dark mode memories, and building nonreciprocal devices.",2312.04915v3 2024-01-07,The role of resonator neuron in the dynamics of two coupled integrator and resonator neurons of different types of excitability,"In this manuscript, a silent resonator neuron is coupled with a spiking integrator neuron through the gap junction, when the coupled neurons are of different types of excitability and none of the coupled neurons exhibit mixed mode oscillations and bursting oscillations intrinsically. By using dynamical systems theory (e.g. the bifurcation theory), all the observed oscillation patterns and the transition mechanisms between them are investigated, when one of the coupling strengths is fixed and the other is varied. It is noticeable that, there is an interval in the parameter space, for the parameter values within which the coupled system is multi-stable. This multistability corresponds to the coexistence of mixed mode oscillations, bursting oscillations and subthreshold oscillations of the resonator neuron. In addition, some interval in the parameter space is introduced such that, for the values of the coupling strength within which the resonator neuron is in tonic spiking mode, while for the values of the coupling strength outside which the resonator neuron exhibits subthreshold oscillations. It is also verified that the final synchronization of the coupled neurons actually corresponds to the synchronization of tonic spiking oscillations of the integrator neuron and one-bursting oscillations of the resonator neuron.",2401.03419v1 2024-01-09,Determining the structure of $Hqt$ couplings at the LHC,"Experiments at the Large Hadron Collider (LHC) have found that the Higgs boson discovered in 2012 has properties largely consistent with predictions from the standard model (SM). However, the determination of the couplings of the Higgs boson to various other SM particles is not very precise, and it is possible that future experiments with enhanced accuracy may be able to detect deviations from the SM if any. One category of couplings studied at the LHC is Higgs flavour-changing couplings to a top-quark and a light-quark ($u$ or $c$) combination, which vanishes at tree level in the SM, but could be induced by interactions beyond the SM. Experiments have put a limit on the magnitude of these couplings, only one coupling assumed nonzero at a time. We investigate here to what extent the relative magnitudes of the $Hut$ and $Hct$ couplings and their chirality structure can be determined by means of more detailed kinematics at a future higher-luminosity version of the LHC in the process of $tH$ production. In particular, we find that the top-quark polar-angle distribution in $tH$ production could reveal the relative magnitudes of the $Hut$ and $Hct$ couplings, while the azimuthal distribution of the charged leptons arising from top decay can be used for a determination of the chiral structure of the $Hut$ coupling.",2401.04551v1 1994-05-19,A Coupling of Pseudo Nambu Goldstone Bosons to Other Scalars and Role in Double Field Inflation,"We find a coupling of Pseudo Nambu Goldstone bosons (PNGBs) to other (ordinary) scalars, and consider its importance in various contexts. Our original motivation was the model of Double Field inflation [1]. We also briefly consider the role of this coupling for the case of the QCD axion.",9405045v1 2002-05-14,Loop Corrections to Scalar Quintessence Potentials,"The stability of scalar quintessence potentials under quantum fluctuations is investigated both for uncoupled models and models with a coupling to fermions. We find that uncoupled models are usually stable in the late universe. However, a coupling to fermions is severely restricted. We check whether a graviton induced fermion-quintessence coupling is compatible with this restriction.",0205206v1 2006-01-23,"Bulk viscosity of a gas of neutrinos and coupled scalar particles, in the era of recombination","Bulk viscosity may serve to damp sound waves in a system of neutrinos coupled to very light scalar particles, in the era after normal neutrino decoupling but before recombination. We calculate the bulk viscosity parameter in a minimal scheme involving the coupling of the two systems. We add some remarks on the bulk viscosity of a system of fully ionized hydrogen plus photons.",0601525v1 1993-06-09,"Synchronization of coupled maps and stable, dissipative windows","Synchronization among globally coupled, chaotic map lattices can be related to stable periodic windows in isolated chaotic maps. This relation provides a simple predictive tool for the understanding of complicated behavior in coupled physical, chemical and biological systems.",9306004v1 1997-01-13,Designing coupling that guarantees synchronization between identical chaotic systems,"We examine synchronization between identical chaotic systems. A rigorous criteria is presented which, if satisfied, guarantees that the coupling produces linearly stable synchronous motion. The criteria can also be used to design couplings that lead to stable synchronous motion. Analytical results from a dynamical system are presented.",9701011v1 1997-09-12,Fuzzy phase transition in a 1D coupled stable-map lattice,"A coupled-map lattice showing complex behavior in presence of a fully negative Lyapunov spectrum is considered. A phase transition from ordered to disordered evolution upon changing diffusive coupling is studied in detail. Various indicators provide a coherent description of the scenario: the existence of an intermediate transition region characterized by an irregular alternancy of periodic and chaotic evolution.",9709016v1 1999-12-22,Large Global Coupled Maps with Multiple Attractors,"A system of N unidimensional global coupled maps (GCM), which support multiattractors is studied. We analize the phase diagram and some special features of the transitions (volume ratios and characteristic exponents), by controlling the number of elements of the initial partition that are in each basin of attraction. It was found important difference with widely known coupled systems with a single attractor.",9912037v1 1994-10-07,Crossover from Spin-Density-Wave to Neel-like Ground state,"The characterization and evolution of a Spin Density Wave into the Quantum Neel ground state is considered in the context of a weak coupling theory of the half-filled Hubbard model. Magnetic properties obtained from this weak coupling approach in one dimension compare favorably with exact results from Bethe ansatz (BA). A study of the evolution of several length scales from weak to strong coupling is also presented.",9410019v1 1996-03-07,Intensity Fluctuations in Closed and Open Systems,"We consider the intensity pattern, generated by a monochromatic source, in a disordered cavity coupled to the environment. For weak coupling, and when the source frequency is tuned to a resonance, the intensity distribution is close to Porter-Thomas distribution. When the coupling increases, gradually crosses over to the Rayleigh distribution. The joint probability distribution for intensities at two different points is also discussed.",9603057v1 1997-05-28,Coupled Critical Models: Applications to Ising-Potts Models,"We discuss the critical behaviour of 2D Ising and q-states Potts models coupled by their energy density. We found new tricritical points. The procedure employed is the renormalisation approach of the perturbations series around conformal field theories representing pure models as already used for disordered spins models. This analysis could be useful to understand the physics of coupled critical models like the fully frustrated XY model.",9705292v1 1997-08-20,Some properties of a class of coupled Langevin equations,"We present a set of coupled continuum equationswith a specific coupling between mobile grains $\rho$ and clusters $h$ on the surface of a sandpile. The equations are analysed self-consistently; we demonstrate that Edwards' infrared divergence is responsible for the unexpected critical exponents we find, which are verified by simulations.",9708155v1 1997-09-13,Spin-density Wave in Ising-coupled Antiferromagnetic Chains,"The effect of anisotropy in the nearest-neighbor spin interactions that couple $N\geq 2$ consecutive spin-1/2 antiferromagnetic chains is studied theoretically by considering the limit where the coupling is purely of the Ising type. An analysis based on the equivalent Luttinger model reveals that the groundstate is an Ising antiferromagnet in general.",9709153v1 1998-03-03,Theoretical analysis of the resistively-coupled single-electron transistor,"The operation of resistively-coupled single-electron transistor (R-SET) is studied quantitatively. Due to the Nyquist noise of the coupling resistance, degradation of the R-SET performance is considerable at temperatures $T$ as small as $10^{-3} e^2/C$ (where $C$ is the junction capacitance) while the voltage gain becomes impossible at $T\agt 10^{-2}e^2/C$.",9803038v1 1999-08-20,Ising cubes with enhanced surface couplings,"Using Monte Carlo techniques, Ising cubes with ferromagnetic nearest-neighbor interactions and enhanced couplings between surface spins are studied. In particular, at the surface transition, the corner magnetization shows non-universal, coupling-dependent critical behavior in the thermodynamic limit. Results on the critical exponent of the corner magnetization are compared to previous findings on two-dimensional Ising models with three intersecting defect lines.",9908291v1 2001-03-05,Parametric phase transition in one dimension,"We calculate analytically the phase boundary for a nonequilibrium phase transition in a one-dimensional array of coupled, overdamped parametric harmonic oscillators in the limit of strong and weak spatial coupling. Our results show that the transition is reentrant with respect to the spatial coupling in agreement with the prediction of the mean field theory.",0103104v1 2001-12-03,Magnetic coupling between mesoscopic superconducting rings,"Using the nonlinear Ginzburg-Landau theory we investigated the dependence of the magnetic coupling between two concentric mesoscopic superconducting rings on their thickness. The size of this magnetic coupling increases with the thickness of the rings.",0112027v1 2002-07-25,Four-wave mixing in coupled semiconductor quantum dots,"We present a theoretical analysis of four-wave mixing in coupled quantum dots subject to inhomogeneous broadening. For the biexciton transitions a clear signature of interdot-coupling appears in the spectra. The possibility of experimental observation is discussed.",0207596v1 2002-09-12,Tetramerisation of a frustrated spin-1/2 chain,"We investigate a model of a frustrated spin-1/2 Heisenberg chain coupled to adiabatic phonons with a general form of magnetoelastic coupling. For large enough frustration and lattice coupling a new tetramerised phase with three different bond lengths is found. We argue that the zig-zag spin-1/2 chain LiV$_2$O$_5$ might be a good candidate to observe such a phase.",0209278v1 2003-10-21,Microscopic Derivation of Magnetic Coupling in Ca3Co2O6,"For cobalt atoms placed along chain structures in Ca3Co2O6, we investigate the spin exchange coupling between atoms in high spin states. Consistent with experimental findings, the coupling is weakly ferromagnetic.",0310500v1 2004-05-20,An asymptotic formula for marginal running coupling constants and universality of loglog corrections,"Given a two-loop beta function for multiple marginal coupling constants, we derive an asymptotic formula for the running coupling constants driven to an infrared fixed point. It can play an important role in universal loglog corrections to physical quantities.",0405466v2 2004-07-02,Dielectric anomaly in coupled rotor systems,"The correlated dynamics of coupled quantum rotors carrying electric dipole moment is theoretically investigated. The energy spectra of coupled rotors as a function of dipolar interaction energy is analytically solved. The calculated dielectric susceptibilities of the system show the peculiar temperature dependence different from that of isolated rotors.",0407050v1 2005-03-27,Duality in the Kondo model and perturbative approach to strong coupling theory,"We investigate the duality in the Kondo model. Starting from the s-d model with the coupling constant $J$, the strong coupling model with the constant of 1/J is identified. The model shows the unitary limit of the conductance, $G=2 e^{2}/h$ at zero temperature. The perturbation theory of the model gives qualitative agreement with the results of numerical renormalization group and Bethe ansatz near $T=T_{K}$.",0503633v1 2005-08-19,Influence of spin-orbit interaction on quantum cascade transitions,"We have investigated the effect of spin-orbit (SO) coupling on the emission spectra of a quantum cascade laser. In an externally applied magnetic field parallel to the electron plane, the SO coupling would result in a double-peak structure of the optical spectra. This structure can be observed within some interval of magnetic fields and only for diagonal optical transitions when the SO coupling is different in different quantum wells.",0508473v1 2005-09-09,Synchronization in large directed networks of coupled phase oscillators,"We extend recent theoretical approximations describing the transition to synchronization in large undirected networks of coupled phase oscillators to the case of directed networks. We also consider extensions to networks with mixed positive/negative coupling strengths. We compare our theory with numerical simulations and find good agreement.",0509255v1 2006-03-20,Enhanced Shot Noise in Tunneling through a Stack of Coupled Quantum Dots,"We have investigated the noise properties of the tunneling current through vertically coupled self-assembled InAs quantum dots. We observe super-Poissonian shot noise at low temperatures. For increased temperature this effect is suppressed. The super-Poissonian noise is explained by capacitive coupling between different stacks of quantum dots.",0603512v1 2006-10-26,Coupled Breathing Oscillations of Two-Component Fermion Condensates in Deformed Traps,"We investigate collective excitations coupled with monopole and quadrupole oscillations in two-component fermion condensates in deformed traps. The frequencies of monopole and dipole modes are calculated using Thomas-Fermi theory and the scaling approximation. When the trap is largely deformed, these collective motions are decoupled to the transverse and longitudinal breathing oscillation modes. As the trap approaches becoming spherical, however, they are coupled and show complicated behaviors.",0610727v1 2007-01-11,Some exact identities connecting one- and two-particle Green's functions in spin-orbit coupling systems,"Some exact identities connecting the one- and two-particle Green's functions in the presence of spin-orbit coupling have been derived. These identities is similar to the usual Ward identity in the particle or charge transport theory and a satisfying spin transport theory in spin-orbit coupling system should also preserve these identities.",0701227v1 1995-10-11,Dilaton Gravity with a Non-Minimally Coupled Scalar Field,"We discuss the two-dimensional dilaton gravity with a scalar field as the source matter. The coupling between the gravity and the scalar, massless, field is presented in an unusual form. We work out two examples of these couplings, and solutions with black-hole behaviour are discussed and compared with those found in the literature.",9510021v1 1996-10-10,Slow Roll Inflation in Non-Minimally Coupled Theories: Hyperextended Gravity Approach,"The slow roll approximation is studied for cosmological models in Hyperextended Scalar-Tensor Theories of Gravity. A procedure to obtain slow roll solutions in non-minimally coupled gravity is outlined and some examples are provided. An integral condition over the functional form of the non-minimal coupling is imposed in order to obtain intermediate inflationary behavior.",9610021v1 1996-11-22,Conformal Couplings in Induced Gravity,"It is found that the induced gravity with conformal couplings requires the conformal invariance in both classical and quantum levels for consistency. This is also true for the induced gravity with an extended conformal coupling interacting with torsion.",9611053v1 1999-04-07,Conformally Coupled Induced Gravity with Gradient Torsion,"It is found that conformally coupled induced gravity with gradient torsion gives a dilaton gravity in Riemann geometry. In the Einstein frame of the dilaton gravity the conformal symmetry is hidden and a non-vanishing cosmological constant is not plausible due to the constraint of the conformal coupling.",9904018v1 2000-06-10,Self-similar spherically symmetric wave maps coupled to gravity,"We investigate spherically symmetric continuously self-similar (CSS) solutions in the SU(2) sigma model coupled to gravity. Using mixed numerical and analytical methods, we provide evidence for the existence (for small coupling) of a countable family of regular CSS solutions. This fact is argued to have important implications for the ongoing studies of black hole formation in the model.",0006034v1 2003-10-08,Chaotic self-similar wave maps coupled to gravity,"We continue our studies of spherically symmetric self-similar solutions in the SU(2) sigma model coupled to gravity. For some values of the coupling constant we present numerical evidence for the chaotic solution and the fractal threshold behavior. We explain this phenomenon in terms of horseshoe-like dynamics and heteroclinic intersections.",0310050v2 2005-02-10,Feynman diagams coupled to three-dimensional quantum gravity,"A framework for quantum field theory coupled to three-dimensional quantum gravity is proposed. The coupling with quantum gravity regulates the Feynman diagrams. One recovers the usual Feynman amplitudes in the limit as the cosmological constant tends to zero.",0502048v2 1999-11-02,Tau Electroweak Couplings,"We review world-average measurements of the tau lepton electroweak couplings, in both decay (including Michel parameters) and in production ($Z^0\to \tau^+\tau^-$ and $W^-\to\tau^-\nubar_\tau$). We review the searches for anomalous weak and EM dipole couplings. Finally, we present the status of several other tau lepton studies: searches for lepton flavor violating decays, neutrino oscillations, and tau neutrino mass limits.",9911002v1 2000-05-15,Search for Anomalous ZZgamma and Zgammagamma couplings in the process e+e- -> Zgamma at LEP,"We search for anomalous trilinear gauge couplings in the ZZgamma and Zgammagamma vertices using data collected with the L3 detector at LEP at a centre-of-mass energy \sqrt{s}=189 GeV. No evidence is found and limits on these couplings and on new physics scales are derived from the analysis of the process e+e- -> Zgamma.",0005024v1 1994-12-23,Asymptotic scaling from strong coupling in 2-d lattice chiral models,"Two dimensional $N=\infty$ lattice chiral models are investigate by a strong coupling analysis. Strong coupling expansion turns out to be predictive for the evaluation of continuum physical quantities, to the point of showing asymptotic scaling (within 5\%).",9412097v1 1995-11-13,Lattice Investigations of the Running Coupling,"A review of investigations of running couplings using lattice techniques is given. This includes i) studies of the running of particular non-perturbatively defined renormalized couplings in pure gauge theories over a range of energies, and ii) how estimates of $\alpha_{\overline{MS}}(m_Z)$ in lattice QCD are presently obtained.",9511017v1 1997-10-02,A Note on the Action in d>4 Dynamical Triangulations,"For dynamical triangulations in dimensions d<=4 the most general action has two couplings. We note that the most general action for d=5 has three couplings. We explore this larger coupling space using Monte Carlo simulations. Initial results indicate evidence for non-trivial phase structure.",9710014v1 1997-12-03,Monte Carlo Simulation Calculation of Critical Coupling Constant for Continuum φ^4_2,"We perform a Monte Carlo simulation calculation of the critical coupling constant for the continuum {\lambda \over 4} \phi^4_2 theory. The critical coupling constant we obtain is [{\lambda \over \mu^2}]_crit=10.24(3).",9712008v1 1999-09-04,Strongly coupled 't Hooft model on the lattice,"A lattice strong coupling calculation of the spectrum and chiral condensate of the 't Hooft model is presented. The agreement with the results of the continuum theory is strikingly good even at the fourth order in the strong coupling expansion.",9909027v1 1999-09-14,N=1 Super Yang-Mills on the Lattice in the Strong Coupling Limit,"We study the N=1 supersymmetric SU(N) Yang-Mills theory on the lattice at strong coupling. We analyse and discuss the recent results obtained at strong coupling and large N for the mesonic and fermionic propagators and spectrum.",9909113v1 2001-10-31,Schrödinger functional at N_f=-2,"We study the Schr\""odinger functional coupling for lattice Yang-Mills theory coupled to an improved bosonic spinor field, which corresponds to QCD with minus two light flavors. This theory serves as a less costly testcase than QCD for the scaling of the coupling.",0110224v1 2002-08-27,Strongly coupled N=1 SYM theory on the lattice,"We propose a strong coupling expansion as a possible tool to obtain qualitative and quantitative informations about N=1 SYM theory. We point out the existence of a mapping between strongly coupled lattice N=1 SYM theory and a generalized SO(4) antiferromagnetic spin system.",0208061v1 2005-12-25,The behavior of the sextic coupling for the the three-dimensional $φ^4 $ theory,"In this work we use the lattice regularization method to study the behavior of the six point renormalized coupling constant defined at zero momentum for the three-dimensional $\phi^4 $ theory in the intermediate and strong coupling domain. The result is in good agreement with the corresponding study in the Ising limit.",0512037v1 1992-09-15,Anomalous Gauge-Boson Couplings at Hadron Supercolliders,"We discuss anomalous gauge boson couplings at hadron supercolliders. We review the usual description of these couplings, as well as the studies of a strongly interacting electroweak symmetry breaking sector. We present an effective field theory formulation of the problem that relates the two subjects, and that allows a consistent and systematic analysis. We end with some phenomenology.",9209237v1 1994-12-01,High-colour pomerons with a running coupling constant in the Hartree-Fock approximation,"The Hartree-Fock approximation is applied to study the ""high-colour pomerons"" in the system of many reggeized gluons with a running QCD coupling constant. It is shown that, contrary to the fixed coupling case, the high-colour pomerons result supercritical, although with a smaller intercept than the multipomeron states.",9412202v1 1995-01-09,TESTING THE $WWγ$ COUPLING AT $e^+e^-$ COLLIDERS,"The production of single photons plus missing energy at future $e^{+}e^{-}$ colliders can provide a testing ground for non-standard $WW\gamma$ couplings. We show that even with conservative estimates of systematic errors there is still considerable sensitivity to anomalous couplings.",9501237v1 1995-04-24,Selection Rules for Nonrenormalizable Couplings in Superstring Theories,"We study nonrenormalizable coupling terms in $Z_N$ orbifold models. Nontrivial selection rules of couplings are provided and cannot be understood in terms of a simple symmetry of effective field theories. We also discuss phenomenological implications of theses selection rules for the quark mass matrices.",9504371v1 1995-10-11,Self-Couplings of Electroweak Bosons: Theoretical Aspects and Tests at Hadron Colliders,"The current theoretical understanding of anomalous gauge boson couplings is reviewed, and the direct measurement of these couplings in present and future hadron collider experiments is briefly discussed.",9510265v1 1995-11-21,Structure of Pomeron Couplings and Single-Spin Asymmetry in Diffractive $Q \bar Q$ Production,"Transverse single spin asymmetry in polarized diffractive $Q \bar Q$ production is calculated. It is shown that this asymmetry depends strongly on the spin structure of the pomeron coupling, which permits one to study the pomeron couplings properties in future polarized experiments.",9511382v1 1996-02-14,"Proton lifetime, Yukawa couplings and dynamical SUSY breaking in SU(5) GUT","We study the influence of messenger Yukawa couplings and top, bottom and $\tau$ Yukawa couplings on the proton lifetime in SU(5) Supersymmetric GUT with dynamical supersymmetry breaking mechanism due to Dine and Nelson.",9602310v1 1997-09-11,Non-decoupling effects due to a dimensionful coupling,"We show that the dimensionful scalar cubic coupling in 3+1 dimensions gives rise to non-decoupling effects and analyze the behavior of these effects. In the process, we clarify how it is perturbatively consistent to construct theories in which the cubic coupling is dominant. We use the scalar sector of the Supersymmetric Standard Model as an example. We discuss how the non-decoupling effects may be analyzed systematically.",9709309v1 1997-11-18,Quark-Gluon Coupling in the Global Colour Model of QCD,"The Global Colour Model of QCD is used in conjunction with a pure-gluon lattice correlator (by Marenzoni et al.) to extract from meson data a momentum-dependent quark-gluon coupling down to $s \approx 0.3 GeV^2$. This is compared with a lattice calculation (by Skullerud) of the quark-gluon coupling.",9711359v1 1999-02-25,g_{K LAMBDA N} and g_{K SIGMA N} coupling constants in light cone QCD sum rules,"The strong coupling constants g_{K LAMBDA N} and g_{K SIGMA N} for the structure (sigma_{mu,nu} gamma_5) are calculated within light cone QCD sum rules. A comparison of our results on these couplings with predictions from traditional QCD sum rules is presented.",9902466v1 1999-04-11,Pion--baryon coupling constants in light cone QCD sum rules,"We calculate the ""pi Sigma Lambda"" and ""pi Sigma Sigma"" coupling constants in light cone QCD sum rules for the structure ""sigma_{alpha beta} gamma_5 p^alpha q^beta"". A comparison of our results on these coupling constants with prediction of the SU(3) symmetry is presented.",9904296v2 1999-04-20,Proton Spin Based On Chiral Dynamics,"Chiral spin fraction models agree with the proton spin data only when the chiral quark-Goldstone boson couplings are pure spinflip. For axial-vector coupling from soft-pion physics this is true for massless quarks but not for constituent quarks. Axial-vector quark-Goldstone boson couplings with {\bf constituent} quarks are found to be inconsistent with the proton spin data.",9904405v1 1999-11-24,Diffractive hadron production and pomeron coupling structure,"Large-distance effects, which lead to the spin-flip part of the hadron -pomeron coupling in QCD -models, are discussed. We study spin asymmetries in exclusive reactions and in diffractive $Q \bar Q$ and vector meson production which are sensitive to the spin-dependent part of the pomeron coupling.",9911469v1 2000-06-22,A Calculation of Higgs Mass in the Standard Model,"The assumption that the ratio of the Higgs self-coupling to the square of its yukawa coupling to the top is (almost) independent of the renormalization scale fixes the Higgs mass within narrow limits at m=160 GeV using only the values of gauge couplings and top mass.",0006258v1 2004-03-05,Calculation of coupling constant g_phi-pi-gamma in QCD sum rules,"The coupling constant of g_phi-pi-gamma decay is calculated in the method of QCD sum rules. A comparison of our prediction on the coupling constant with the result obtained from analysis of the experimental data is performed.",0403060v1 2004-09-27,Quartic gauge couplings from e+e- -> WWZ,"Effective anomalous quartic gauge couplings on tree level appear, e.g., in a strong interacting Higgs scenario. We present a status report on our study on triple boson production sensitive to these couplings. The study is done for parameters of a future linear collider.",0409305v1 2004-10-14,Gauge boson couplings at LEP,"A review is given of the measurements of triple and quartic couplings among the electroweak gauge bosons performed at LEP by the four experiments ALEPH, DELPHI, L3 and OPAL. Emphasis is placed on recently published results and on combinations of results performed by the LEP electroweak gauge-couplings group. All measurements presented are consistent with the Standard Model expectations.",0410208v1 2005-01-20,A Charge-Conjugation-Invariance Constrained Pomeron-Quark Coupling,"The commonly used $\gamma_{\mu}} Pomeron-quark coupling changes its sign under charge conjugation, in contradiction to the property of Pomeron. I show that the Pomeron-quark coupling is tensorial and is invariant under the charge conjugation.",0501195v1 2005-03-14,Coupling constants g_a0-omega-gamma as derived from light cone QCD sum rules,"We investigate the a0-omega-gamma vertex and estimate the coupling constant in the framework of the light cone QCD sum rules. We compare our result with the value of the coupling constant was calculated in the QCD sum rules.",0503128v2 2005-07-28,The Quartic Higgs Coupling at Hadron Colliders,"The quartic Higgs self-coupling is the final measurement in the Higgs potential needed to fully understand electroweak symmetry breaking. None of the present or future colliders are known to be able to determine this parameter. We study the chances of measuring the quartic self-coupling at hadron colliders in general and at the VLHC in particular. We find the prospects challenging.",0507321v1 2006-01-16,Running coupling and screening in the (s)QGP,"Emphasizing the importance of renormalization in the context of thermal field theory in general, it is pointed out that the Debye mass in the hot quark gluon plasma is determined by the coupling at the scale $m_D$, not $T$ as commonly presumed. The mended result agrees quantitatively with lattice QCD calculations in the strong coupling regime almost down to $T_c$.",0601119v2 2006-03-06,g_a0-rho-gamma and g_f0-rho-gamma coupling constants in three point QCD sum rules,"The coupling constant of a0-->rho-gamma and f0-->rho-gamma decays are calculated using 3-point sum rule. We estimate the coupling constant g_a0-rho-gamma and g_f0-rho-gamma which are an essential ingredient in the analysis of physical processes involving isoscalar f0(980) and isovector a0(980) mesons.",0603045v1 1993-06-23,Exact Solution for the Most General Minimally Coupled One Dimensional Lattice Gauge Theory,"We consider one dimensional lattice gauge theories constructed by the minimal coupling prescription. It is shown that these theories are exactly solvable in the thermodynamic limit. After considering the most general case, we discuss some special cases on finite lattices, and also work out some examples. There is no phase transition in these minimally coupled theories.",9306121v1 1994-01-12,Nonrenormalization Theorem for Gauge Coupling in 2+1D,"We prove that $\be$-function of the gauge coupling in $2+1D$ gauge theory coupled to any renormalizable system of spinor and scalar fields is zero. This result holds both when the gauge field action is the Chern-Simons action and when it is the topologically massive action.",9401053v1 1994-03-15,Strong Coupling Phase of Chiral Gross Neveu Model,"We perform the numerical simulation of the two dimensional chiral Gross Neveu model using the Kogut-Susskind(KS) fermion. In the case of SU(4), the Kosterlitz-Thouless phase transition happens at some critical value of the coupling constant. In the case of one flavour, there exists the strong coupling phase in which the correlation functions vanish and the general covariance is realized in the quantum field thoery through the dynamical process.",9403078v1 1996-01-22,CP^{N-1} models and the Quantized 2D Black Holes,"We have examined the coupled system of the dilaton gravity and the $CP^{N-1}$ theory known as a model of the confinement of massive scalar quarks. After the quantization of the system, we could see the quantum effect of the gravitation on the coupling constant of $CP^{N-1}$ model and how the coupling constant of dynamically induced gauge field changes near the black hole configuration.",9601110v1 1996-03-22,Coupling supergravity to non-supersymmetric matter,"By introducing a nonlinearly transforming goldstino field non-super\-sym\-metric matter can be coupled to supergravity. This implies the possibility of coupling a standard model with one Higgs to supergravity.",9603148v2 1996-05-06,I-Brane Inflow and Anomalous Couplings on D-Branes,"We show that the anomalous couplings of $D$-brane gauge and gravitational fields to Ramond-Ramond tensor potentials can be deduced by a simple anomaly inflow argument applied to intersecting $D$-branes and use this to determine the eight-form gravitational coupling.",9605033v1 1996-11-07,Relativistic QFTH - Couplings on the Worldline,"In the framework of the worldline path integral approach to QFTH we discuss spin and relativistic couplings, in particular Yukawa and axial couplings to spin 1/2, and the case of spin 1 in the loop.",9611044v1 1997-07-24,Singular Yukawa and gauge couplings in d=4 Heterotic String Vacua,"In this paper we discuss the singularities in the Yukawa and gauge couplings of N=1 compactifications of the SO(32) heterotic string in four space-time dimensions. Such singularities can arise from the strong coupling dynamics of a confined non-perturbative gauge group.",9707212v1 1997-12-17,"Tensor Multiplets in Six-Dimensional (2,0) Supergravity","We construct the complete coupling of $(2,0)$ supergravity in six dimensions to $n$ tensor multiplets, extending previous results to all orders in the fermi fields. The truncation to $(1,0)$ supergravity coupled to tensor multiplets exactly reproduces the complete couplings recently obtained.",9712176v1 1998-12-17,(Non-)Anomalous D-brane and O-plane couplings: the normal bundle,"The direct string computation of anomalous D-brane and orientifold plane couplings is extended to include the curvature of the normal bundle. The normalization of these terms is fixed unambiguously. New, non-anomalous gravitational couplings are found.",9812149v2 1999-04-23,Pauli's Term and Fractional Spin,"In this work we consider an Abelian Chern-Simons-Higgs model coupled non-minimally to matter fields. This coupling is implemented by means of a Pauli-type coupling. We show that the Pauli term is sufficient to gives rise to fractional spin.",9904159v1 1999-04-29,Finiteness of 2D Topological BF-Theory with Matter Coupling,"We study the ultraviolet and the infrared behavior of 2D topological BF-Theory coupled to vector and scalar fields. This model is equivalent to 2D gravity coupled to topological matter. Using techniques of the algebraic renormalization program we show that this model is anomaly free and ultraviolet as well as infrared finite at all orders of perturbation theory.",9904204v1 1999-05-21,Ramond-Ramond couplings of non-BPS D-branes,"We study how non-BPS type II D-branes couple to R-R potentials. Upon tachyon condensation the couplings we find give rise to the Wess-Zumino action of BPS D-branes.",9905157v2 2000-03-06,Quantisation of Extended Objects,"The `strong-coupling' perturbation theory over the inverse interaction constant $1/g$ near the nontrivial solution of Lagrange equation is formulated. The ordinary `week-coupling' perturbation theory over $g$ is described also to compare both perturbation theories. The `strong-coupling' perturbation theory is developed by unitary mapping of the quantum dynamics into the space with local coordinates of (action, angle)-type.",0003039v1 2001-07-17,Gauge Couplings and Group Dimensions in the Standard Model,"The gauge field term in the Standard Model Lagrangian is slightly rewritten, suggesting that the three gauge couplings have absorbed factors which depend on the dimensions of the corresponding gauge groups. The ratios of the physical couplings may turn out to be dominated by these factors, with deviations due to quantum corrections.",0107144v1 2002-09-18,Vanishing of the Bare Coupling in Four Dimensions,"We examine two restructurings of the series relationship between the bare and renormalized coupling constant in dimensional regularization. In one of these restructurings, we are able to demonstrate via all-orders summation of leading and successive epsilon = 0 (dimensionality = 4) poles that the bare coupling vanishes in the dimension-4 limit.",0209151v2 2003-03-03,Heterotic Yukawa couplings and continuous Wilson lines,"Realistic heterotic string models require the presence of the Wilson lines. We study the effect of continuous Wilson lines on the heterotic Yukawa couplings and find that the presence of continuous Wilson lines affects the magnitude of the twisted Yukawa couplings resulting in their stronger hierarchy.",0303009v2 2003-09-25,Modulus stabilization via non-minimal coupling,"We propose a massless nonminimally coupled scalar field as a mechanism for stabilizing the size of the extradimension in the Randall-Sundrum I scenario. Without needing to introduce self interactions terms we obtain a potential for the modulus field that sets the size of the fifth dimension. The minumum of this potential yields appropriate values of the compactification scale for small values of the coupling $\xi$.",0309235v1 2005-01-28,Nonperturbative Newtonian coupling in Einstein gravity with Dirac fields,"We investigate the exact renormalization group (RG) in Einstein gravity coupled to N-component spinor field, working in the effective average action formalism and background field method. The truncated evolution equation is obtained for the Newtonian and cosmological constants. We have shown that screening or antiscreening behaviour of the gravitational coupling depends crucially on the number of spinor components",0501239v1 2005-07-21,Confinement of spinless particles by Coulomb potentials in two-dimensional space-time,"The problem of confinement of spinless particles in 1+1 dimensions is approached with a linear potential by considering a mixing of Lorentz vector and scalar couplings. Analytical bound-states solutions are obtained when the scalar coupling is of sufficient intensity compared to the vector coupling.",0507218v1 2005-06-01,Coupled nonlinear Schrodinger systems with potentials,"Coupled nonlinear Schrodinger systems describe some physical phenomena such as the propagation in birefringent optical fibers, Kerr-like photorefractive media in optics and Bose-Einstein condensates. In this paper, we study the existence of concentrating solutions of a singularly perturbed coupled nonlinear Schrodinger system, in presence of potentials. We show how the location of the concentration points depends strictly on the potentials.",0506010v1 2005-09-15,Robust Routing and Cross-Entropy Estimation,"In the following article, we present a novel way to etimate the amounts of traffic on the Origin-Destination couples (OD couples). This new approach combines together a routing algorithm based on the principle of the shortest path and a recent technique of stochastic optimization called Cross-Entropy. In a final part, we adapt a particular filtering algorithm in order to be able to dynamically estimate the evolution of the traffic on the OD couples.",0509352v1 2005-11-17,"A Coupling, and the Darling-Erdos Conjectures","We derive a new coupling of the running maximum of an Ornstein-Uhlenbeck process and the running maximum of an explicit i.i.d. sequence. We use this coupling to verify a conjecture of Darling and Erdos (1956).",0511429v1 2007-03-15,A New Version of the Menages Problem,"The probleme des menages (married couples problem) introduced by E.Lucas in 1891 is a classical problem that asks the number of ways to arrange n married couples around a circular table, so that husbands and wives are in alternate places but no couple is seated together. In this paper we present a new version of the Menage Problem that carries the constraints consistent with the Muslim culture.",0703444v2 2002-05-10,Long-time Behavior for the Stochastic Ising Model with Unbounded Random Couplings,"We consider the ferromagnetic Ising model with Glauber spin flip dynamics in one dimension. The external magnetic field vanishes and the couplings are i.i.d. random variables. If their distribution has compact support, the disorder averaged spin auto-correlation function has an exponential decay in time. We prove that, if the couplings are unbounded, the decay switches to either a power law or a stretched exponential, in general.",0205014v1 1995-08-01,Interlayer Coupling in Magnetic/Pd Multilayers,"The Anderson model of local-state conduction electron mixing is applied to the p roblem of interlayer magnetic coupling in metallic multilayered structures with palladium (Pd) spacer layers. An oscillation period of $5$ spacer monolayers and the tendency towards ferromag netic bias of the interlayer magnetic coupling that we obtain are consistent with the experimental data.",9508002v1 2000-12-10,Asymptotic Liapunov exponents spectrum for an extended chaotic coupled map lattice,"The scaling hypothesis for the coupled chotic map lattices (CML) is formulated. Scaling properties of the CML in the regime of extensive chaos observed numerically before is justified analytically. The asymptotic Liapunov exponents spectrum for coupled piece-wise linear chaotic maps lattice is found.",0012018v1 2002-03-01,Interaction of Coupled Higher Order Nonlinear SCHRÖdinger Equation Solitons,"The novel inelastic collision properties of two-soliton interaction for an $n$-component coupled higher order nonlinear Schr\""odinger equation are studied. Some interesting features of three soliton interactions, related to the integrability of the $n$-component coupled higher order nonlinear Schr\""odinger equation are also discussed.",0203001v1 2007-03-01,Localized Asymmetric Atomic Matter Waves in Two-Component Bose-Einstein Condensates Coupled with Two Photon Microwave Field,"We investigate localized atomic matter waves in two-component Bose-Einstein condensates coupled by the two photon microwave field. Interestingly, the oscillations of localized atomic matter waves will gradually decay and finally become non-oscillating behavior even if existing coupling field. In particular, atom numbers occupied in two different hyperfine spin states will appear asymmetric occupations after some time evolution.",0703001v1 1995-11-28,Quantum Solitons Lead to Yukawa Coupling,"Recently, it was shown that zero modes in semiclassical soliton models do not lead to Yukawa couplings. We show that taking into account the contributions of the quantum soliton into the renormalization scheme, which cannot be done in semiclassical treatments, leads to a Yukawa coupling. A similar analysis should be possible for the Skyrmion, renewing the hope, that this model will lead to a correct description of hadron physics.",9511034v1 1998-12-01,Modeling Nonperturbative QCD for Mesons and Couplings,"We discuss aspects of a covariant QCD modeling of meson physics by illustrating applications to several coupling constants and form factors. In particular, we cover the $\rho\pi\pi$ and $\pi^0 \gamma \gamma$ interactions, the $\rho$ contribution to the pion charge radius, and $\pi NN$ coupling.",9812005v1 1999-12-20,Pion-Baryon Couplings,"We have extended and applied a general QCD parameterization method to the emission of pions from baryons. We use it to calculate the strength and sign of the coupling of pions to the octet and decuplet of baryons. Certain relations between octet and decuplet couplings are pointed out.",9912044v1 2003-08-29,Coupled cluster approach to nuclear physics,"Using many-body perturbation theory and coupled-cluster theory, we calculate the ground-state energy of He-4 and O-16. We perform these calculations using a no-core G-matrix interaction derived from a realistic nucleon-nucleon potential. Our calculations employ up to two-particle-two-hole coupled-cluster amplitudes.",0308088v1 2006-04-03,Channel coupling effects in $ρ$-meson photoproduction,"We investigate $\rho$-meson photoproduction in a coupled-channels formulation. It is shown that channel coupling effects are large and account for discrepancies observed in several single-channel treatments.",0604009v2 1998-10-01,Localized Structures in Pattern-Forming Systems,"A number of mechanisms that lead to the confinement of patterns to a small part of a translationally symmetric pattern-forming system are reviewed: nonadiabatic locking of fronts, global coupling and conservation laws, dispersion, and coupling to additional slow modes $via$ gradients. Various connections with experimental results are made.",9810002v1 1999-05-07,Calculation of ionization within the close-coupling formalism,"An adaptation of the convergent close-coupling method (CCC) to calculation of differential ionization cross sections is analyzed in the context of the Temkin-Poet model. The asymptotic scattering wave functions and the unitarity relation are given for the model. It is concluded the use of ""distinguishable"" electrons as proposed in the CCC model is not essential in the close-coupling formulation of ionization.",9905020v1 1999-06-08,Electromagnetic modes in cold magnetized strongly coupled plasmas,"The spectrum of electromagnetic waves propagating in a strongly coupled magnetized fully ionized hydrogen plasma is found. The ion motion and damping being neglected, the influence of the Coulomb coupling on the electromagnetic spectrum is analyzed.",9906016v1 2000-12-18,Parametric Processes in a Strong-Coupling Planar Microcavity,"I present a theoretical treatment of parametric scattering in strong coupling semiconductor microcavities to model experiments in which parametric oscillator behaviour has been observed. The model consists of a non-linear excitonic oscillator coupled to a cavity mode which is driven by the external fields, and predicts the output power, below threshold gain and spectral blue shifts of the parametric oscillator. The predictions are found to be in excellent agreement with the experimental data.",0012043v1 2004-05-17,Optimal classification of HCI spectra,"Energy levels of highly charged ions as a rule cannot be classified using LS coupling due to rapid increase of relativistic effects. It is suggested, for optimal classification of energy spectra, to calculate them in LS coupling and to transform the weights of the wave functions, obtained after diagonalization of the energy matrix, to the other coupling schemes. F-like ions are considered as an example.",0405087v1 2006-01-11,Non-linear charge reduction effect in strongly-coupled plasmas,"The charge reduction effect, produced by the nonlinear Debye screening of high-Z charges occuring in strongly-coupled plasmas, is investigated. An analytic asymptotic expression is obtained for the charge reduction factor which determines the Debye-Hueckel potential generated by a charged test particle. Its relevant parametric dependencies are analyzed and shown to predict a strong charge reduction effect in strongly-coupled plasmas.",0601077v1 2006-02-28,Instability of synchronized motion in nonlocally coupled neural oscillators,"We study nonlocally coupled Hodgkin-Huxley equations with excitatory and inhibitory synaptic coupling. We investigate the linear stability of the synchronized solution, and find numerically various nonuniform oscillatory states such as chimera states, wavy states, clustering states, and spatiotemporal chaos as a result of the instability.",0602026v1 2002-08-02,Intrinsic decoherence and classical-quantum correspondence in two coupled delta-kicked rotors,"We show that classical-quantum correspondence of center of mass motion in two coupled delta-kicked rotors can be obtained from intrinsic decoherence of the system itself which occurs due to the entanglement of the center of mass motion to the internal degree of freedom without coupling to external environment.",0208013v1 2002-11-11,Recursive Weak- and Strong Coupling Expansions in a Cosine Potential,"For the Cos(2x)-Potential the coefficients of the weak- and strong coupling perturbation series of the ground state energy are constructed recursively. They match the well-known expansion coefficients of the Mathieu equation's characteristic values. However presently there is no physically intuitive method to extract the coefficients of the strong coupling series from those of the weak one. The standard rule while giving exellent results for the anharmonic oscillator fails completely in this case.",0211057v1 2003-10-09,Interfacing quantum optical and solid state qubits,"We present a generic model of coupling quantum optical and solid state qubits, and the corresponding transfer protocols. The example discussed is a trapped ion coupled to a charge qubit (e.g. Cooper pair box). To enhance the coupling, and achieve compatibility between the different experimental setups we introduce a superconducting cavity as the connecting element.",0310057v1 2004-07-15,Efficient fiber coupling of down-conversion photon pairs,"We develop and apply an effective analytic theory of a non-collinear, broadband type-I parametric down-conversion to study a coupling efficiency of the generated photon pairs into single mode optical fibers. We derive conditions necessary for highly efficient coupling for single and double type-I crystal producing polarization entangled states of light. We compare the obtained approximate analytic expressions with the exact numerical solutions and discuss the results for a case of BBO crystals.",0407113v1 2004-12-08,Optimal coupling of entangled photons into single-mode optical fibers,"We present a consistent multimode theory that describes the coupling of single photons generated by collinear Type-I parametric down-conversion into single-mode optical fibers. We have calculated an analytic expression for the fiber diameter which maximizes the pair photon count rate. For a given focal length and wavelength, a lower limit of the fiber diameter for satisfactory coupling is obtained.",0412065v1 2005-07-20,A minimal coupling method for dissipative quantum systems,"Quantum dynamics of a general dissipative system investigated by its coupling to a Klein-Gordon type field as the environment by introducing a minimal coupling method. As an example, the quantum dynamics of a damped three dimensional harmonic oscillator investigated and some transition probabilities indicating the way energy flows between the subsystems obtained. The quantum dynamics of a dissipative two level system considered.",0507195v1 2006-05-01,Nature of quantum recurrences in coupled higher dimensional systems,"We investigate recurrence phenomena in coupled two degrees of freedom systems. It is shown that an initial well localized wave packet displays recurrences even in the presence of coupling in these systems. We discuss the interdependence of these time scales namely, classical period and quantum revival time, and explain significance of initial conditions.",0605019v1 1999-09-22,Dressing method and the coupled KP hierarchy,"The coupled KP hierarchy, introduced by Hirota and Ohta, are investigated by using the dressing method. It is shown that the coupled KP hierarchy can be reformulated as a reduced case of the 2-component KP hierarchy.",9909024v1 2007-05-02,The mass and the coupling of the Dark Particle,"We argue that Dark Matter can be described by an interacting field theory with a mass parameter of the order of the proton mass and an interaction coupling of the order of the QED coupling.",0705.0268v1 2007-07-17,Pinning Complex Networks by a Single Controller,"In this paper, without assuming symmetry, irreducibility, or linearity of the couplings, we prove that a single controller can pin a coupled complex network to a homogenous solution. Sufficient conditions are presented to guarantee the convergence of the pinning process locally and globally. An effective approach to adapt the coupling strength is proposed. Several numerical simulations are given to verify our theoretical analysis.",0707.2411v1 2007-08-28,Extending BCCNR flavored geometry to the negative coupling constant region,"We extend BCCNR's flavored KW and KS geometries into the negative coupling constant region and try giving physical explanations from the dual gauge theory side. We show that, in the extended region, except the coupling constant being negative, all other fields of the super-gravity theory having good properties which can be described by the dual gauge theory.",0708.3814v1 2007-08-31,Unparticle Physics And Gauge Coupling Unification,"Unparticle physics from a hidden conformal sector can alter the evolution of the Standard Model (SM) gauge couplings via TeV scale threshold corrections. We discuss how this may lead to gauge coupling unification at M_{GUT}\approx 2 \times 10^{15} GeV -- 5 \times 10^{17} GeV without introducing new particles in the SM sector.",0708.4405v1 2007-09-04,Suppression of Meszaros' Effect in coupled DE,"A phaenomenological DM-DE coupling could indicate their common origin. Various constraint however exist to such coupling; here we outline that it can suppress Meszaros' effect, yielding transfered spectra with a softer bending above k_{hor,eq}. It could be therefore hard to reconcile these models with both CMB and deep sample data, using a constant spectral index.",0709.0315v1 2007-09-06,Spin-gravity coupling and gravity-induced quantum phases,"External gravitational fields induce phase factors in the wave functions of particles. The phases are exact to first order in the background gravitational field, are manifestly covariant and gauge invariant and provide a useful tool for the study of spin-gravity coupling and of the optics of particles in gravitational or inertial fields. We discuss the role that spin-gravity coupling plays in particular problems.",0709.0819v1 2007-09-11,Global phase-locking in finite populations of phase-coupled oscillators,"We present new necessary and sufficient conditions for the existence of fixed points in a finite system of coupled phase oscillators on a complete graph. We use these conditions to derive bounds on the critical coupling.",0709.1558v1 2008-02-22,Synchronized and desynchronized phases of coupled non-equilibrium exciton-polariton condensates,"We theoretically analyze the synchronized and desynchronized phases of coupled non-equilibrium polariton condensates within mean field theory. An analytical condition for the existence of a synchronized phase is derived for two coupled wells. The case of many wells in a 2D disordered geometry is studied numerically. The relation to recent experiments on polariton condensation in CdTe microcavities is discussed.",0802.3339v1 2008-03-06,Girard couples of quantales,"We introduce the concept of a Girard couple, which consists of two (not necessarily unital) quantales linked by a strong form of duality. The two basic examples of Girard couples arise in the study of endomorphism quantales and of the spectra of operator algebras. We construct, for an arbitrary sup-lattice $S$, a Girard quantale whose right-sided part is isomorphic to $S$.",0803.0853v1 2008-03-16,Dynamics of delay-coupled excitable neural systems,"We study the nonlinear dynamics of two delay-coupled neural systems each modelled by excitable dynamics of FitzHugh-Nagumo type and demonstrate that bistability between the stable fixed point and limit cycle oscillations occurs for sufficiently large delay times and coupling strength. As the mechanism for these delay-induced oscillations we identify a saddle-node bifurcation of limit cycles.",0803.2352v1 2008-04-21,Coupled-Resonator Optical Near-Field Lithography,"The problem of pattern formation in resonantly-enhanced near-field lithography by the use of dielectric or plasmonic planar resonators is investigated. Sub-diffraction-limited bright or dark spots can be produced by taking advantage of the rotational invariance of planar resonators. To increase the spatial bandwidth of the resonant enhancement, an array of coupled planar resonators can open up a band of Bloch resonances, analogous to coupled-resonator optical waveguides.",0804.3374v1 2008-05-22,Testing Chameleon models in the laboratory,"We review some recent developments in chameleon models. In particular we discuss the possibility of chameleons coupling both to photons and baryonic matter with different coupling strengths. We will discuss the possibility of probing the chameleon-photon coupling with quantum vacuum experiments in the laboratory.",0805.3461v1 2008-05-23,A practical approach to solve coupled systems of nonlinear partial differential equations,"In this paper we present the tanh method to obtain exact solutions to coupled MkDV system. This method may be applied to a variety of coupled systems of nonlinear ordinary and partial differential equations.",0805.3670v1 2008-06-04,Relaxation time of a CFT plasma at finite coupling,"Following recent formulation of second order relativistic viscous hydrodynamics for conformal fluids, we compute finite coupling corrections to the relaxation time of N=4 supersymmetric Yang-Mills plasma. The result is expected to be universal for any strongly coupled conformal gauge theory plasma in four dimensions.",0806.0788v1 2009-01-06,Phase locking between two singing wineglasses,"Coupling between two singing wineglasses was obtained and investigated. Rubbing the rim of one wineglass produce a tone and due to the coupling induces oscillations on the other wineglasses. The needed coupling strength between the wineglasses to induce oscillations as a function of the detuning was investigated.",0901.0656v2 2009-01-20,Asynchronous entanglement from coherently coupled nonlinear cavities,"The output fields of a pair of coherently coupled nonlinear optical cavities are found to exhibit strong optical entanglement. For sufficiently strong coupling the quantum correlations become asynchronous providing a resource for quantum information protocols such as all-optical quantum memories. A straightforward experimental implementation applicable to whispering gallery mode resonators such as microtoroids is proposed.",0901.3072v1 2009-01-21,Quantum Mechanics of Successive Measurements with Arbitrary Meter Coupling,"We study successive measurements of two observables using von Neumann's measurement model. The two-pointer correlation for arbitrary coupling strength allows retrieving the initial system state. We recover Luders rule, the Wigner formula and the Kirkwood-Dirac distribution in the appropriate limits of the coupling strength.",0901.3265v1 2009-02-12,The Relationship between Bare and Renormalized Couplings in Scalar Electrodynamics,"When using dimensional regularization, the bare couplings are expressed as a power series in (2 - n/2)^{-1} where n is the number of dimensions. It is shown how the renormalization group can be used to sum the leading pole, next to leading pole etc. contributions to these sums in scalar electrodynamics (or any theory with multiple couplings.)",0902.2205v1 2009-03-22,Time Delays in the Synchronization of Chaotic Coupled Systems with Feedback,"The synchronized excitable behavior of two coupled chaotic diode lasers with feedback was experimental and numerically studied. We determine the relation between the observed delay times in synchronized Low Frequency Fluctuation spikes and the coupling and the feedback times in the lasers.",0903.3764v1 2009-04-19,Invariant Gibbs Measures and a.s. Global Well-Posedness for Coupled KdV Systems,"We continue our study of the well-posedness theory of a one-parameter family of coupled KdV-type systems in the periodic setting. When the value of a coupling parameter \alpha \in (0, 4) \setminus 1, we show that the Gibbs measure is invariant under the flow and the system is globally well-posed almost surely on the statistical ensemble, provided that certain Diophantine conditions are satisfied.",0904.2816v1 2009-10-01,CP violating anomalous top-quark couplings at the Large Hadron Collider,"In this talk, I review the T-odd correlations induced by CP violating anomalous top-quark couplings at both production and decay level in the process gg --> t t_bar --> (b mu+ nu_mu) (b_bar mu-nu_mu_bar). In addition I will also focus on experimental sensitivities corresponding to the anomalous couplings at the LHC.",0910.0068v1 2009-10-03,Holographic dark energy with non-minimal coupling,"We study a scalar field non-minimally coupled to the curvature, in the framework of holographic dark energy. We obtain a relation between the coupling of the scalar field and the holographic DE parameters. In the model without potential we found the EOS parameter in different regions of the parameters, giving rise to accelerated expansion. For some restrictions on the parameters, the model presents quintom behavior.",0910.0515v1 2009-11-18,"Multi-soliton, multi-positon, multi-negaton, and multi-periodic solutions of the coupled Volterra lattice equation","This paper aims to find new explicit solutions including multi-soliton, multi-positon, multi-negaton, and multi-periodic for a coupled Volterra lattice system which is an integrable discrete version of the coupled KdV equation. The dynamical properties of these new solutions are discussed in detail.",0911.3458v1 2010-01-18,Nearest-neighbor coupling asymmetry in the generation of cluster states,"We demonstrate that charge-qubit cluster state generation by capacitive coupling is anisotropic. Specifically, horizontal vs vertical nearest-neighbor inter-qubit coupling differs in a rectangular lattice. We show how to ameliorate this anisotropy by applying potential biases to the array of double dots.",1001.2877v2 2010-07-11,On the coupling of two quantum dots through a cavity mode,"The effective coupling of two distant quantum dots through virtual photon exchange in a semiconductor microcavity is studied. The experimental conditions for strong coupling and its manifestation in the spectra of emission are analyzed.",1007.1784v1 2010-09-14,Pseudo-gap and vertex correction of electron-phonon interaction,"The strong-coupling Eliashberg theory plus vertex correction is used to calculate the maps of transition temperature (Tc) in parameter-space characterizing superconductivity. Based on these Tc maps, complex crossover behaviors are found when electron-phonon interaction increases from weak-coupling region to strong-coupling region. The doping-dependent Tc of cuprate superconductors and most importantly the pseudo-gap can be explained as the effects of vertex correction.",1009.2552v1 2010-09-28,Constructions of Coupling Processes for Lévy Processes,"We construct optimal Markov couplings of L\'{e}vy processes, whose L\'evy (jump) measure has an absolutely continuous component. The construction is based on properties of subordinate Brownian motions and the coupling of Brownian motions by reflection.",1009.5511v2 2010-10-20,Parton Energy Loss in Strongly Coupled AdS/CFT,"This is a brief review of the theory and phenomenology of parton energy loss in strongly coupled field theories with a gravity dual and its comparison with parton energy loss in QCD at weak coupling.",1010.4258v2 2010-11-24,Soliton solutions for coupled Schrodinger systems with sign-changing potential,"In this paper, a class of coupled systems of nonlinear Schrodinger equations with sign-changing potential, including the linearly coupled case, is considered. The existence of non-trivial bound state solutions via linking methods for cones in Banach spaces is proved.",1011.5280v1 2010-12-02,Coincidence Problem in $f(R)$ Gravity Models,"The $f(R)$ gravity models formulated in Einstein conformal frame are equivalent to Einstein gravity together with a minimally coupled scalar field. The scalar field couples with the matter sector and the coupling term is given by the conformal factor. We use this interacting model to derive a necessary condition for alleviating the coincidence problem.",1012.0405v1 2010-12-16,Parton branching and medium-induced radiation in a strongly coupled plasma,"I review the parton picture at strong coupling emerging from the gauge/gravity duality together with its consequences for the energy loss and momentum broadening of a heavy quark moving through a strongly coupled plasma.",1012.3527v1 2011-01-23,The Full Two-Loop R-parity Violating Renormalization Group Equations for All Minimal Supersymmetric Standard Model Couplings,"We present the full two-loop $\beta$-functions for the minimal supersymmetric standard model couplings, extended to include R-parity violating couplings through explicit R-parity violation.",1101.4358v3 2011-05-30,Experimental realization of mixed-synchronization in counter-rotating coupled oscillators,"Recently, a novel mixed-synchronization phenomenon is observed in counter-rotating nonlinear coupled oscillators. In mixed-synchronization state: some variables are synchronized in-phase, while others are out-of-phase. We have experimentally verified the occurrence of mixed-synchronization states in coupled counter-rotating chaotic piecewise Rossler oscillator. Analytical discussion on approximate stability analysis and numerical confirmation on the experimentally observed behavior is also given.",1105.5856v1 2011-09-29,Controllability of cascade coupled systems of multi-dimensional evolution PDE's by a reduced number of controls,"We prove controllability results for abstract systems of weakly coupled $N$ evolution equations in cascade by a reduced number of boundary or locally distributed controls ranging from a single up to $N-1$ controls. We give applications to cascade coupled systems of $N$ multi-dimensional-hyperbolic, parabolic and diffusive equations.",1109.6645v2 2011-10-27,Running coupling from gluon exchange in the Schrodinger functional,"I propose a new method to determine the running coupling in a Schrodinger-functional setup. The method utilizes the scattering amplitude of massless fermions propagating between the time boundaries. Preliminary tests show the statistical fluctuations of the new observable to be about half those of the standard Schrodinger-functional running coupling.",1110.6046v1 2011-12-12,Running Coupling Corrections to Nonlinear Evolution for Diffractive Dissociation,"We determine running coupling corrections to the kernel of the non-linear evolution equation for the cross section of single diffractive dissociation in high energy DIS. The running coupling kernel for diffractive evolution is found to be exactly the same as the kernel of the rcBK evolution equation.",1112.2598v1 2012-03-18,Statistical properties of coupled expanding maps on a lattice with general infinite range couplings and Hölder densities,"We continue the development of transfer operator techniques for expanding maps on a lattice coupled by general interaction functions. We obtain a spectral gap for an appropriately defined transfer operator, and, as corollaries, the existence of an invariant conformal probability measure for the system, exponential decay of correlations, the central limit theorem and the almost sure invariance principle.",1203.3992v1 2013-02-05,$L^p$ estimates for fully coupled FBSDEs with jumps,"In this paper we study useful estimates, in particular $L^p$-estimates, for fully coupled forward-backward stochastic differential equations (FBSDEs) with jumps. These estimates are proved at one hand for fully coupled FBSDEs with jumps under the monotonicity assumption for arbitrary time intervals and on the other hand for such equations on small time intervals. Moreover, the well-posedness of this kind of equation is studied and regularity results are obtained.",1302.0936v1 2013-04-04,Heat transport through a quantum Brownian harmonic chain beyond the weak-coupling regime: An exact treatment,"We consider a linear chain of quantum harmonic oscillators, in which the number of the individual oscillators is given by an arbitrary number N, and each oscillator is coupled at an arbitrary strength kappa to its nearest neighbors (""intra-coupling""), as well as the two end oscillators of the chain are coupled at an arbitrary strength c_nu to two separate baths at arbitrarily different temperatures, respectively. We derive an exact closed expression for the steady-state heat current flowing from a hot bath through the chain to a cold bath, in the Drude-Ullersma damping model going beyond the Markovian damping. This allows us to explore the behavior of heat current relative to the intra-coupling strength as a control parameter, especially in pursuit of the heat power amplification. Then it turns out that in the weak-coupling regime (kappa, c_nu << 1), the heat current is small, as expected, and almost independent of chain length N, hence violating Fourier's law of heat conduction; this is consistent to the earlier results obtained within the rotating wave approximation for the intra-coupling as well as in the Born-Markov approximation for the chain-bath coupling. Beyond the weak-coupling regime, on the other hand, we typically observe that with increase of the intra-coupling strength the heat current is gradually amplified, and reaches its maximum value at some specific coupling strength kappa_R ""resonant"" to a given chain-bath coupling strength. Also, the behavior of heat current versus chain length appears typically in such a way that the magnitude of current reaches its maximum with N=1 and then gradually decreases with increase of the chain length, being in fact almost N-independent in the range of N large enough. As a result, Fourier's law proves violated also in this regime.",1304.1283v4 2013-04-30,Derivation of conditions for a Brans-Dicke coupling constant of order unity be consistent with solar system bounds,"We provide proofs of some assumptions recently made by F. O. Minotti to conclude on the possibility that an additional scalar field minimally coupled to gravity may help to reconcile a Brans-Dicke coupling constant $\omega$ of the order unity with solar system bounds.",1304.8124v1 2013-05-02,Leptonic contributions to the effective electromagnetic coupling at four-loop order in QED,"The running of the effective electromagnetic coupling is for many electroweak observables the dominant correction. It plays an important role for deriving constraints on the Standard Model in the context of electroweak precision measurements. We compute the four-loop QED corrections to the running of the effective electromagnetic coupling and perform a numerical evaluation of the different gauge invariant subsets.",1305.0581v1 2013-07-22,Exciton-Plasmon Coupling Effects on the Nonlinear Optical Susceptibility of Hybrid Quantum Dot-Metallic Nanoparticle System,"We have studied theoretically the exciton-plasmon coupling effects on the third-order optical nonlinearity of a coherently coupled hybrid system of a metal nanoparticle and a semiconductor quantum dot in the presence of a strong control field with a weak probe field.",1307.5648v1 2013-07-25,Shock Waves in Falling Coupled Harmonic Oscillators,"Shock waves propagate in falling coupled harmonic oscillators. The bottom end of coupled harmonic oscillators does not fall downwards until a shock wave reaches the bottom end. The exact solution can be expressed by the Fourier series expansion, and an approximate solution can be expressed by the integral of the Airy function. The width of the shock wave increases slowly in accordance with a power law.",1307.6686v1 2013-07-27,Global weak solution for a coupled compressible Navier-Stokes and Q-tensor system,"In this paper, we study a coupled compressible Navier-Stokes/Q-tensor system modeling the nematic liquid crystal flow in a three-dimensional bounded spatial domain. The existence and long time dynamics of globally defined weak solutions for the coupled system are established, using weak convergence methods, compactness and interpolation arguments. The symmetry and traceless properties of the Q-tensor play key roles in this process.",1307.7316v1 2013-12-23,Cosmology with non-minimally coupled Yang--Mills field,"We discuss cosmological model with homogeneous and isotropic Yang-Mills field non-minimally coupled to gravity through an effective mass term. In this model conformal symmetry is violated which leads to possibility of inflationary expansion. Parameters of non-minimal coupling have relatively ``natural'' values in the regime of sufficiently long acceleration stage.",1312.6559v1 2013-12-24,Energy-Based Atomistic-to-Continuum Coupling Without Ghost Forces,"We present a practical implementation of an energy-based atomistic-to-continuum (a/c) coupling scheme without ghost forces, and numerical tests evaluating its accuracy relative to other types of a/c coupling schemes.",1312.6814v1 2014-01-14,Hybrid-cascade Coupled-Line Phasers for High-resolution Radio-Analog Signal Processing,"A hybrid-cascade (HC) coupled-line phaser configuration is presented to synthesize enhanced group delay responses for high-resolution Radio-Analog Signal Processing (R-ASP). Using exact analytical transfer functions, the superiority of HC coupled-line phasers over conventional transversally cascaded C-section phasers is demonstrated and verified using full-wave simulations.",1401.6046v1 2014-04-29,Rayleigh scattering in coupled microcavities: Theory,"In this paper we theoretically study how structural disorder in coupled semiconductor heterostructures influences single-particle scattering events that would otherwise be forbidden by symmetry. We extend the model of V. Savona to describe Rayleigh scattering in coupled planar microcavity structures, and answer the question, whether effective filter theories can be ruled out. They can.",1404.7394v1 2014-07-12,Coupled Grain Boundary Motion with Triple Junctions,"Coupled grain boundary (GB) motion has been studied in a two-dimensional tricrystal where a cylindrical grain is embedded at the center of the planar GB of a large bicrystal. Kinetic relations for GB dynamics, grain orientations, and junctions have been derived within the framework of Gibbs thermodynamics. These are solved numerically to investigate the shrinkage of the embedded grain while emphasizing the role of coupled motion as well as junction mobility in the shape evolution.",1407.3350v1 2015-01-15,Nonlocal symmetries and conservation laws of the coupled Hirota equation,"Using the lax pair, nonlocal symmetry of the coupled Hirota equation is obtained. By introducing an appropriate auxiliary dependent variable the nonlocal symmetry is successfully localized to a Lie point symmetry. For the closed prolongation, one-dimensional optimal systems and nonlocal conservation laws of the coupled Hirota equation are studied.",1501.03580v1 2015-05-05,Reciprocal link for a coupled Camassa-Holm type equation,"A coupled Camassa-Holm type equation is linked to the first negative flow of a modified Drinfeld-Sokolov III hierarchy by a transformation of reciprocal type. Meanwhile the Lax pair and bi-Hamiltonian structure behaviors of this coupled Camassa-Holm type equation under change of variables are analyzed.",1505.00961v1 2015-05-05,Numerical and analytical studies on the complete synchronization of the variant of Murali-Lakshmanan-Chua circuits,"In this paper we present numerical and analytical studies on the complete synchronization phenomena exhibited by unidirectionally coupled two variant of Murali-Lakshmanan-Chua circuits. The transition of the coupled system from an unsynchronized state to a state of complete synchronization under the influence of the coupling parameter is observed through phase portraits obtained numerically and analytically.",1505.01090v1 2015-05-07,Coupled SU(3)-structures and Supersymmetry,"We review coupled ${\rm SU}(3)$-structures, also known in the literature as restricted half-flat structures, in relation to supersymmetry. In particular, we study special classes of examples admitting such structures and the behaviour of flows of ${\rm SU}(3)$-structures with respect to the coupled condition.",1505.01655v1 2015-05-29,A coupled-channel formalism for three-body final state interaction,"From dispersion relation approach, a formalism that describes final state interaction among three particles in a coupled-channel system is presented in this work. Different representations of coupled-channel three-body formalism with only spinless particles in both initial and final states are derived.",1506.00042v2 2015-10-19,Transient dynamics of pulse-coupled oscillators with nonlinear charging curves,"We consider the transient behavior of globally coupled systems of identical pulse coupled oscillators. Synchrony develops through an aggregation phenomenon, with clusters of synchronized oscillators forming and growing larger in time. Previous work derived expressions for these time dependent clusters, when each oscillator obeyed a linear charging curve. We generalize these results to cases where the charging curves have nonlinearities",1510.05341v2 2015-10-28,Triple Higgs coupling in the most general 2HDM at SM-like scenario,"We consider the triple Higgs coupling for $h(125)$ Higgs boson within the most general 2HDM. At moderate values of parameters of model, allowing by modern data, noticeable deviation of this coupling from its SM value is improbable. This deviation can be sizable only if some measurable parameters of the model are exotic.",1510.08270v3 2015-10-31,Deep-subwavelength magnetic-coupling-dominant stereometamaterials,"Here, we experimentally demonstrate that a stack of metallic spiral structures (MSSs) can have dominant magnetic coupling in both of its two configurations. This allows magnetic-coupling-dominant energy transport along a one-dimensional stack of MSSs at a deep-subwavlength scale, as demonstrated with near-field transmission measurement.",1511.00072v1 2015-11-13,Cluster synchronization of starlike networks with normalized Laplacian coupling: master stability function approach,"A generalized model of starlike network is suggested that takes into account non-additive coupling and nonlinear transformation of coupling variables. For this model a method of analysis of synchronized cluster stability is developed. Using this method three starlike networks based on Ikeda, predator-prey and H\'enon maps are studied.",1511.04465v1 2016-02-12,Scalar field conformally coupled to a charged BTZ black hole,"We study the Klein-Gordon equation of a scalar field conformally coupled to a charged BTZ black hole. The background metric is obtained by coupling a non-linear and conformal invariant Maxwell field to (2+1) gravity. We show that the radial part is generally solved by a Heun function and, in the pure gravity limit, by a hypergeometric function.",1602.04021v1 2016-03-22,FG-coupled fixed point theorems for contractive and generalized quasi-contractive mappings,"In this paper we prove FG-coupled fixed point theorems for different contractive mappings and generalized quasi- contractive mappings in partially ordered complete metric spaces. We prove the existence of FG-coupled fixed points of continuous as well as discontinuous mappings. We give some examples to illustrate the results.",1604.02669v1 2016-07-07,Hamiltonian Coupling of Electromagnetic Field and Matter,"Reversible part of evolution equations of physical systems is often generated by a Poisson bracket. We discuss geometric means of construction of Poisson brackets and their mutual coupling (direct, semidirect and matched-pair products) as well as projections of Poisson brackets to less detailed Poisson brackets. This way the Hamiltonian coupling between transport of mixtures and electrodynamics is elucidated.",1607.02023v2 2016-07-27,Darboux transformations and exact soliton solutions of integrable coupled spin systems related with the Manakov system,"We construct a Darboux transformation of a general $su(3)$-valued spin system called the $\Gamma$-spin system. Using this Darboux transformation we derive a recursive formula for the soliton solutions of this spin system. Then using these results we present explicit expressions for the 1-soliton solution of the coupled $su(2)$-valued spin systems, namely, of the coupled M-LIII equation.",1607.08151v1 2017-02-02,Exponential stability for a coupled system of damped-undamped plate equations,"We consider the transmission problem for a coupled system of undamped and structurally damped plate equations in two sufficiently smooth and bounded subdomains. It is shown that, independently of the size of the damped part, the damping is strong enough to produce uniform exponential decay of the energy of the coupled system.",1702.00637v1 2010-05-17,Noise-Induced Synchronization of a Large Population of Globally Coupled Nonidentical Oscillators,"We study a large population of globally coupled phase oscillators subject to common white Gaussian noise and find analytically that the critical coupling strength between oscillators for synchronization transition decreases with an increase in the intensity of common noise. Thus, common noise promotes the onset of synchronization. Our prediction is confirmed by numerical simulations of the phase oscillators as well as of limit-cycle oscillators.",1005.2833v1 2013-08-09,Probing the nature of the Higgs-gluon coupling,"One and two-jet observables of dimension-7 Higgs-gluon coupling operators are studied as probes of possible deviations from the top-loop induced gluon-Higgs coupling. We discuss the case of both a scalar as well as a pseudo-scalar Higgs boson and show that higher order operators can give visible deviations from Standard Model distribution shapes.",1308.2225v1 2014-03-10,New Physics Contributions to the Muon Anomalous Magnetic Moment: A Numerical Code,"We consider the contributions of individual new particles to the anomalous magnetic moment of the muon, utilizing the generic framework of simplified models. We also present analytic results for all possible one-loop contributions, allowing easy application of these results for more complete models which predict more than one particle capable of correcting the muon magnetic moment. Additionally, we provide a Mathematica code to allow the reader straightforwardly compute any 1-loop contribution. Furthermore, we derive bounds on each new particle considered, assuming either the absence of other significant contributions to $a_\mu$ or that the anomaly has been resolved by some other mechanism. The simplified models we consider are constructed without the requirement of $SU(2)_L$ invariance, but appropriate chiral coupling choices are also considered. In summary, we found the following particles capable of explaining the current discrepancy, assuming unit couplings: $2$~TeV ($0.3$~TeV) neutral scalar with pure scalar (chiral) couplings, $4$~TeV doubly charged scalar with pure pseudoscalar coupling, $0.3-1$~TeV neutral vector boson depending on what couplings are used (vector, axial, or mixed), $0.5-1$~TeV singly-charged vector boson depending on which couplings are chosen, and $3$~TeV doubly-charged vector-coupled bosons. We also derive the following $1\sigma$ lower bounds on new particle masses assuming unit couplings and that the experimental anomaly has been otherwise resolved: a doubly charged pseudo-scalar must be heavier than $7$~TeV, a neutral scalar than $3$~TeV, a vector-coupled new neutral boson $600$~GeV, an axial-coupled neutral boson $1.5$~TeV, a singly-charged vector-coupled $W^\prime$ $1$~TeV, a doubly-charged vector-coupled boson $5$~TeV, scalar leptoquarks $10$~TeV, and vector leptoquarks $10$~TeV.",1403.2309v2 2014-03-25,Comment on `Self-organized cooperative criticality in coupled complex systems',"In a recent Letter (EPL 105, 40006; arXiv:1309.7107), Liu and Hu presented a model of toppling-coupled sandpiles, where they found that the avalanche exponents for two toppling-coupled sandpiles are the same as those for a single uncoupled sandpile. In this Comment we provide a proof of this observation for the case when there is conservation of grains in the bulk.",1403.6424v1 2017-01-21,Optomechanical Microwave Quantum Illumination in Weak Coupling Regime,"We propose to realize microwave quantum illumination in weak coupling regime based on multimode optomechanical systems. In our proposal the multimode together with a frequency-mismatch process could reduce mechanical thermal noise. Therefore, we achieve a significant reduction of error probability than conventional detector in weak coupling regime. Moreover, we optimize the signal-to-noise ratio for limited bandwidth by tuning the delay time of entangled wave-packets.",1701.05995v1 2018-05-03,Nonlinear systems coupled through multi-marginal transport problems,"In this paper, we introduce a dynamical urban planning model. This leads us to study a system of nonlinear equations coupled through multi-marginal optimal transport problems. A simple case consists in solving two equations coupled through the solution to the Monge-Amp{\`e}re equation. We show that the Wasserstein gradient flow theory provides a very good framework to solve this highly nonlinear system. At the end, an uniqueness result is presented in dimension one based on convexity arguments.",1805.01331v1 2008-07-01,Bouncing Universe with Non-minimally Coupled Quintom Matter,"In this letter, we study the condition for a generalized DBI action providing a quintom scenario of dark energy. We consider a development of string-inspired quintom by introducing non-minimal coupling. Then we show that the bouncing solution can appear in the universe dominated by the non-minimally coupled quintom matter.",0807.0077v1 2009-12-06,From massive gravity to modified general relativity II,"We continue our investigation of massive gravity in the massless limit of vanishing graviton mass. From gauge invariance we derive the most general coupling between scalar matter and gravity. We get further couplings beside the standard coupling to the energy-momentum tensor. On the classical level this leads to a further modification of general relativity.",0912.1112v1 2013-09-02,Running Couplings in Quantum Theory of Gravity Coupled with Gauge Fields,"In this paper we study the coupled system of non-abelian gauge fields with higher-derivative gravity. Charge renormalization is investigated in this coupled system. It is found that the leading term in the gauge coupling beta function comes due to interaction of gauge fields with gravitons. This is shown to be a universal quantity in the sense that it doesn't depend on the gauge coupling and the gauge group, but may depend on the other couplings of the action (gravitational and matter). The coupled system is studied at one-loop. It is found that the leading term of gauge beta function is zero at one-loop in four dimensions. The effect of gauge fields on the running of gravitational couplings is investigated. The coupled system of gauge field with higher-derivative gravity is shown to satisfy unitarity when quantum corrections are taken in to account. Moreover, it is found that Newton constant goes to zero at short distances. In this renormalizable and unitary theory of gauge field coupled with higher-derivative gravity, the leading term of the gauge beta function, found to be universal for all gauge groups, is further studied in more detail by isolating it in the context of abelian gauge theories coupled with gravity in four dimensions. Using self-duality of abelian gauge theories in four dimensions, this term of the gauge beta function is shown to be zero to all loops. This is found to be independent of the gravity action, regularization scheme and gauge fixing condition. An explicit one-loop computation for arbitrary gravity action further demonstrates the vanishing of this term in the gauge beta function in four dimensions, independent of the regularization scheme and gauge fixing condition. Consequences of this are discussed.",1309.0473v1 2016-05-02,Gauge coupling unification with extra Higgs doublets,"Gauge coupling unification is studied within the framework where there are extra Higgs doublets and $E_6$ exotic fields. Supersymmetric models and nonsupersymmetric models are investigated, and a catalog of models with gauge coupling unification is presented.",1605.00921v1 2017-06-25,Nucleon scattering on actinides using a dispersive optical model with extended couplings,"Tamura coupling model has been extended to consider the coupling of additional low-lying rotational bands to the ground state band. Rotational bands are built on vibrational bandheads (even-even targets) or single particle bandheads (odd-$A$ targets) including both axial and non-axial deformations. These additional excitations are introduced as a perturbation to the underlying axially-symmetric rigid rotor structure of the ground state rotational band. Coupling matrix elements of the generalized optical model are derived for extended multi-band transitions in even-even and odd-$A$ nuclei. Isospin symmetric formulation of the optical model is employed. A coupled-channels optical model potential (OMP) containing a dispersive contribution is used to fit simultaneously all available optical experimental databases including neutron strength functions for nucleon scattering on $^{232}$Th, $^{233,235,238}$U and $^{239}$Pu nuclei and quasi-elastic ($p$,$n$) scattering data on $^{232}$Th and $^{238}$U. Lane consistent OMP is derived for all actinides if corresponding multi-band coupling schemes are defined. Calculations using the derived OMP potential reproduce measured total cross-section differences between several actinide pairs within experimental uncertainty for incident neutron energies from 50 keV up to 150MeV. Multi-band coupling is stronger in even-even targets due to the collective nature of the coupling; the impact of extended coupling on predicted compound-nucleus formation cross section reaches 5% below 3 MeV of incident neutron energy. Coupling of ground-state rotational band levels in odd-$A$ nuclei is sufficient for a good description of the compound-nucleus formation cross sections as long as the coupling is saturated (a minimum of 7 coupled levels are typically needed).",1706.08086v1 2019-09-09,Octagons II: Strong Coupling,"The octagon function is the fundamental building block yielding correlation functions of four large BPS operators in N=4 super Yang-Mills theory at any value of the 't Hooft coupling and at any genus order. Here we compute the octagon at strong coupling, and discuss various interesting limits and implications, both at the planar and non-planar level.",1909.04077v1 2019-09-21,Absence of Disorder Chaos for Ising Spin Glasses on $\mathbb Z^d$,"We identify simple mechanisms that prevents the onset of disorder chaos for the Ising spin glass model on $\mathbb Z^d$. This was first shown by Chatterjee in the case of Gaussian couplings. We present three proofs of the theorem for general couplings with continuous distribution based on the presence in the coupling realization of stabilizing features of positive density.",1909.09860v1 2012-05-16,Enhanced coupling design of a detuned damped structure for clic,"The key feature of the improved coupling design in the Damped Detuned Structure (DDS) is focused on the four manifolds. Rectangular geometry slots and rectangular manifolds are used. This results in a significantly stronger coupling to the manifolds compared to the previous design. We describe the new design together with its wakefield damping properties.",1205.3590v1 2012-05-16,Contraction of monotone phase-coupled oscillators,"This paper establishes a global contraction property for networks of phase-coupled oscillators characterized by a monotone coupling function. The contraction measure is a total variation distance. The contraction property determines the asymptotic behavior of the network, which is either finite-time synchronization or asymptotic convergence to a splay state.",1205.3826v3 2017-09-28,Amplitude death by delay induced position coupling in a system of two coupled Van der Pol Oscillators,"We consider a system of two interacting identical Van der Pol Oscillators in a simple harmonic potential well. The position coupling term between the oscillators is such that there is a finite delay, i.e; each system takes a finite time to react to the other one. We investigate the amplitude death in the presence of such interaction and we find out the amplitude death regions in the corresponding parameter space.",1709.09909v1 2018-06-11,Discontinuous Galerkin method for coupling hydrostatic free surface flows to saturated subsurface systems,"We formulate a coupled surface/subsurface flow model that relies on hydrostatic equations with free surface in the free flow domain and on the Darcy model in the subsurface part. The model is discretized using the local discontinuous Galerkin method, and a statement of discrete energy stability is proved for the fully non-linear coupled system.",1806.03909v1 2019-01-29,Spontaneous Long-range Vortex-antivortex Pair in the Two-band 2D Superconductor,"The relaxation iterative method is used to minimize Ginzburg-Landau model for the two-band superconductor with Josephson-coupling. A stable spontaneous vortex-antivortex pair with long range order has been revealed. Our result appears due to the Josephson-coupling effect, which leads to a linearly-dependence of total free energy on the distance between vortex-antivortex pair, hence accounts for this phenomenon.",1901.10149v1 2019-02-22,The Kalman condition for the boundary controllability of coupled 1-d wave equations,"This paper is devoted to prove the exact controllability of a system of N one-dimensional coupled wave equations when the control is exerted on a part of the boundary by means of one control. We consider the case where the coupling matrix A has distinct eigenvalues. We give a Kalman condition (necessary and sufficient) and give a description, non-optimal in general, of the attainable set.",1902.08682v1 2019-03-06,High coupling efficiency grating couplers on lithium niobate on insulator,"We demonstrate monolithically defined grating couplers in $Z$-cut lithium niobate on insulator for efficient vertical coupling between an optical fiber and a single mode waveguide. The grating couplers exhibit $\sim 44.6\%$/coupler and $\sim 19.4\%$/coupler coupling efficiency for TE and TM polarized light respectively. Taperless grating couplers are investigated to realize a more compact design.",1903.02190v1 2019-12-19,Coupling of stationary fields with application to arithmetic waves,"In this paper we obtain a range of quantitative results of the following type: given two centered Gaussian fields with close covariance kernels we construct a coupling such that the fields are uniformly close on some compact with probability very close to one. As an application, we show that it is possible to couple arithmetic random waves so that they converge locally uniformly to the random plane wave and estimate the rate of convergence.",1912.09470v1 2019-12-27,Structural analysis of synchronization in networks of linear oscillators,"In networks of identical linear oscillators (e.g. pendulums undergoing small vibrations) coupled through both dissipative connectors (e.g. dampers) and restorative connectors (e.g. springs) the relation between asymptotic synchronization and coupling structure is studied. Conditions on the interconnection under which synchronization can be achieved for some selection of coupling strengths are established. How to strengthen those conditions so that synchronization is guaranteed for all admissible parameter values is also presented.",1912.12078v1 2015-08-11,Four-loop strong coupling beta-function in the Standard Model,"In this letter we present our results for the four-loop beta-function of the strong coupling in the Standard Model of fundamental interactions. We take top-Yukawa and self-Higgs interactions into account, but neglect electroweak gauge couplings.",1508.02680v2 2015-08-20,Tweezers controlled resonator,"We experimentally demonstrate trapping a microdroplet with an optical tweezer and then enabling it as a microresonator by bringing it close to a tapered fiber coupler. Our tweezers facilitated the tuning of the coupling from the under-coupled to the critically coupled regime with an optical Q of 12 million and microresonator size at the 85 mirons scale.",1508.04881v1 2016-12-02,Top and bottom tensor couplings from a color octet scalar,"We compute the one-loop contributions from a color octet scalar to the tensor anomalous couplings of top and bottom quarks to gluons, photons and W bosons. We use known constraints on the parameters of the model to compare the predicted size of these couplings with existing phenomenological constraints.",1612.00561v2 2017-11-22,Dynamics of quantum collapse in coupled quantum dots,"In this letter, we have considered an electron in a coupled quantum dot system interacting with a detector represented by a point contact. We present a dynamical model for wave function collapse in the strong coupling to the detector limit. In our model, the electron in the double quantum dot makes a fast transition minimizing the emission of electromagnetic radiation. In this way, a principle of leats emitted radiation can provide a possible description of wave function collapse.",1711.08259v1 2018-09-28,Nonlinearly charged black hole in the theory with nonminimal derivative coupling and its thermodynamics,"We have obtained an exact solution for a static black hole in the theory with nonminimal derivative coupling of a scalar field and gravity with a power-law Maxwell field minimally coupled to gravity. Supposing that the black hole might be topological we examined the obtained solution. We also investigated black hole thermodynamics using Wald procedure for calculation of entropy of the black hole.",1810.00061v1 2020-06-29,On monotonicity and couplings of random currents and the loop-$\mathrm{O}(1)$-model,"Using recent couplings we provide counterexamples to monotonicity properties of percolation models related to graphical representations of the Ising model. We further prove a new coupling of the double random current model to the loop-$\mathrm{O}(1)$-model.",2006.15897v2 2013-06-06,Far from standard Higgs couplings,"In this short note we consider a permitted region in the space of couplings of the 126 GeV boson that extends far away from the standard model Higgs couplings. This region is of interest for more natural models of electroweak symmetry breaking. Stronger evidence of vector boson fusion and/or associated production is needed to eliminate this possibility.",1306.1564v1 2013-06-15,Thresholds of Spatially Coupled Systems via Lyapunov's Method,"The threshold, or saturation phenomenon of spatially coupled systems is revisited in the light of Lyapunov's theory of dynamical systems. It is shown that an application of Lyapunov's direct method can be used to quantitatively describe the threshold phenomenon, prove convergence, and compute threshold values. This provides a general proof methodology for the various systems recently studied. Examples of spatially coupled systems are given and their thresholds are computed.",1306.3610v1 2015-12-17,Gauge Coupling Unification in Gauge-Higgs Grand Unification,"We discuss renormalization group equations for gauge coupling constants in gauge-Higgs grand unification on five-dimensional Randall-Sundrum warped space. We show that all the four-dimensional Standard Model gauge coupling constants are asymptotically free and are effectively unified in $SO(11)$ gauge-Higgs grand unified theories on 5D Randall-Sundrum warped space.",1512.05559v1 2016-09-07,Gravitational Couplings on D-brane Revisited,"Gravitational couplings in bulk space-time include those terms which are fixed by scattering amplitude of strings and ambiguous terms that are coming from the field redefinitions. These field redefinitions can be fixed in the bulk by ghost-free condition. In this paper we have revised the effective gravitational couplings on D-branes by including the field redefinitions. We find the gravitational effective action up to $\alpha'^2$-order.",1609.01943v1 2017-04-06,On Well-Posedness for a Piezo-Electromagnetic Coupling Model with Boundary Dynamics,"We consider a coupled system of Maxwell's equations and the equations of elasticity, which is commonly used to model piezo-electric material behavior. The boundary influence is encoded as a separate dynamics on the boundary data spaces coupled to the partial differential equations. Evolutionary well-posedness, i.e. Hadamard well-posedness and causal dependence on the data, is shown for the resulting model system.",1704.01816v1 2018-08-10,The Local Existence and Blowup Criterion for Strong Solutions to the Kinetic Cucker--Smale Model Coupled with the Compressible Navier--Stokes Equation,"In this paper, we establish the existence and uniqueness of local strong solutions to the kinetic Cucker--Smale model coupled with the isentropic compressible Navier--Stokes equation in the whole space. Moreover, the blowup mechanism for strong solutions to the coupled system is also investigated.",1808.03403v1 2019-06-28,Steady-state squeezing and entanglement in a dissipatively coupled NOPO network,"We investigate the steady-state photon-number squeezing and quantum entanglement in a network of nondegenerate optical parametric oscillators (NOPOs). We treat each NOPO with Shen's Raman laser model, whose lasing mode provides a photon-number-squeezed state. Two dissipatively coupled NOPOs satisfy Hillery-Zubairy's $HZ1$ entanglement criterion if they are pumped far above the threshold and the dissipative coupling is sufficiently larger than the NOPO cavity loss.",1906.12044v1 2019-07-05,Fermionic duality,"Duality transformations play a very important role in theoretical physics. In this paper I propose new duality transformations for fermionic theories. They map the strong coupling regime of one theory to the weak coupling regime of another theory. These transformations are based on the functional integral representation of the fermionic theories in terms of Grassmann variables and rely heavily on the properties of Grassmann variables. Potential applications include the study of the strong coupling phase of the two dimensional Hubbard model.",1907.02767v1 2019-10-08,Coupling for features of random walks,"We use coupling to study the time taken until the distribution of a statistic on a Markov chain is close to its stationary distribution. Coupling is a common technique used to obtain upper bounds on mixing times of Markov chains, and we explore how this technique may be used to obtain bounds on the mixing of a statistic instead.",1910.03265v1 2019-10-13,Residue formula for an obstruction to Coupled Kähler-Einstein metrics,"We obtain a residue formula for an obstruction to the existence of coupled K\""ahler-Einstein metrics described by Futaki-Zhang. We apply it to an example studied separately by Futaki and Hultgren which is a toric Fano manifold with reductive automorphism, does not admit a K\""ahler-Einstein metric but still admits coupled K\""ahler-Einstein metrics.",1910.05706v1 2019-10-16,Global Existence of Strong Solutions to the Kinetic Cucker--Smale Model Coupled with the Stokes Equations,"In this paper, we investigate existence of global-in-time strong solutions to the kinetic Cucker--Smale model coupled with the Stokes equations in the whole space. By introducing a weighted Sobolev space and using space-time estimates for the linear non-stationary Stokes equations, we present a complete analysis on existence of global-in-time strong solutions to the coupled model, without any smallness requirements on initial data.",1910.07170v1 2019-10-29,A New Model of Coupled Hindmarsh-Rose Neurons,"A new model of two coupled neurons is presented by the partly diffusive Hindmarsh-Rose equations. The solution semiflow exhibits globally absorbing characteristics. As the main result, the self-synchronization of the coupled neurons at a uniform rate is proved, which can be extended to complex neuronal networks.",1910.13864v1 2020-01-08,Logarithmic Stability for Coefficients Inverse Problem of Coupled Wave Equations,"This paper investigates the identification of two coefficients in a coupled hyperbolic system with an observation on one component of the solution. Based on the the Carleman estimate for coupled wave equations a logarithmic type stability result is obtained by measurement data only in a suitably chosen subdomain under the assumption that the coefficients are given in a neighborhood of some subboundary.",2001.02379v2 2020-02-09,Kirchhoff divergence and diffusions associated to transport probability measures,"Taking as starting point the approach to the divergence operator on weighted graphs, we give a notion of divergence associated to transport coupling and coupled measures on locally compact Hausdorff spaces. We consider the induced Laplacian operator and the corresponding heat diffusion operators in some particular instances.",2002.03357v2 2020-04-06,Model to study interplay between Beamstrahlung and coupling impedance in future lepton colliders,"A semi-analytical model has been developed to study a combined effect of Beamstrahlung due to beam-beam interaction and beam coupling impedance in the future lepton colliders CEPC and FCCee. This model allows evaluating an impact of the coupling impedance on the bunch length and energy spread in collision. The model is benchmarked against numerical simulations. Analytical estimates for the supercolliders are presented.",2004.02553v1 2020-07-15,Study of anomalous gauge boson self-couplings and the role of spin-$1$ polarizations,"The prime goal of this thesis is to study anomalous gauge boson self couplings, triple gauge boson couplings in particular, with the help of spin polarization observables of the gauge bosons $Z$ and $W^\pm$ in the presence of beam polarizations where ever possible. The neutral triple gauge boson couplings, i.e., $ZZZ$, $ZZ\gamma$, $Z\gamma\gamma$, are studied in $ZZ/Z\gamma$ ($2lq\bar{q}/2l\gamma$) production at an $e^+e^-$ collider with and without beam polarization. Some of these anomalous couplings are also studied in $ZZ$ ($4l$) production at the LHC. In the charge sector the anomalous gauge boson couplings, i.e., $WWZ$, $WW\gamma$ have been studied at an $e^+e^-$ collider in $W^+W^-$ ($l^-\bar{\nu_l}q^\prime\bar{q}$) production. The $WWZ$ anomalous couplings are also studied in $ZW^\pm$ production at LHC in $3l$ + missing $E_T$ channel. All the analyses at an $e^+$-$e^-$ collider have been performed for center-of-mass (CM) energy of $500$ GeV and integrated luminosity of $100$ fb$^{-1}$. The analyses at the LHC are performed at $13$ TeV CM energy of $pp$ collisions. The cross sections and polarization asymmetries, along with other asymmetries (forward-backward, azimuthal), are used to obtain simultaneous limits on the anomalous couplings using Markov-Chain--Monte-Carlo (MCMC) method in each process. The polarization asymmetries can distinguish between $CP$-even and $CP$-odd couplings and help to put tighter constraints on the couplings. The polarization of the initial $e^-$ and $e^+$ beam, in case of $e^+e^-$ collider, are used to increase the signal to background ratio, putting tighter constraints on the anomalous couplings. The polarization asymmetries are instrumental in the measurement of anomalous couplings should a deviation from the SM be observed.",2007.07649v2 2020-10-23,Hubbard model vs. Kondo model: Strong coupling limit,"The Hubbard model and the lattice Kondo model are shown to become identical in the strong-coupling limit. A departure from the strong-coupling regime produces distinct theories, however: the relevant perturbation terms give rise to either short-range spin exchange $(t-J$ model) or short-range charge exchange ($t-V$ model), respectively.",2010.12255v1 2020-10-24,Gravitons in the Strong-Coupling Regime,"In the context of gravity in the strong-coupling regime, the propagation amplitude of gravity coupled to relativistic particles undergoing geodesic separation is calculated exactly. Geodesic separation gives rise to boundary terms associated with the h_\times and h_+ graviton components. At low temperatures the propagation amplitude vanishes, implying no graviton propagation in this regime.",2010.12966v1 2021-06-14,Convergence of ASEP to KPZ with basic coupling of the dynamics,"We prove an extension of a seminal result of Bertini and Giacomin. Namely we consider weakly asymmetric exclusion processes with several distinct initial data simultaneously, then run according to the basic coupling, and we show joint convergence to the solution of the KPZ equation with the same driving noise in the limiting equation. Along the way, we analyze fine properties of nontrivially coupled solutions-in-law of KPZ-type equations.",2106.07727v1 2021-08-02,Efficient simulation of coupled gas and power networks under uncertain demands,"We introduce an approach and a software tool, Grazer, for solving coupled energy networks composed of gas and electric power networks. Those networks are coupled to stochastic fluctuations to address possibly fluctuating demand due to fluctuating demands and supplies. Through computational results the presented approach is tested on networks of realistic size.",2108.00687v2 2021-08-29,A note on the energy transfer in coupled differential systems,"We study the energy transfer in the linear system $$ \begin{cases} \ddot u+u+\dot u=b\dot v\\ \ddot v+v-\epsilon \dot v=-b\dot u \end{cases} $$ made by two coupled differential equations, the first one dissipative and the second one antidissipative. We see how the competition between the damping and the antidamping mechanisms affect the whole system, depending on the coupling parameter $b$.",2108.12776v1 2022-03-21,Topological Expansion of Oscillatory BGW and HCIZ Integrals at Strong Coupling,"We prove that the BGW and HCIZ integrals admit large N topological expansions for complex coupling and complex external fields, provided the coupling is sufficiently strong. The expansion coefficients are holomorphic functions which are genus-specific generating functions for the monotone single and double Hurwitz numbers, respectively.",2203.10746v1 2022-05-02,Virtual Element Method for the Navier--Stokes Equation coupled with the Heat Equation,"We consider the Virtual Element discretization of the Navier-Stokes equations coupled with the heat equation where the viscosity depends on the temperature. We present the Virtual Element discretization of the coupled problem, show its well-posedness, and prove optimal error estimates. Numerical experiments which confirm the theoretical error bounds are also presented.",2205.00954v1 2022-06-20,Continuous boundary condition at the interface for two coupled fluids,"We consider two laminar incompressible flows coupled by the continuous law at a fixed interface. We approach the system by one that satisfies a friction Navier law, and we show that when the friction coefficient goes to infinity, the solutions converges to a solution of the initial system. We then write a numerical Schwarz-like coupling algorithm and run 2D-simulations, that yields same convergence result.",2206.09625v1 2022-07-10,Stability of neutron stars in Horndeski theories with Gauss-Bonnet couplings,"In Horndeski theories containing a scalar coupling with the Gauss-Bonnet (GB) curvature invariant $R_{\rm GB}^2$, we study the existence and linear stability of neutron star (NS) solutions on a static and spherically symmetric background. For a scalar-GB coupling of the form $\alpha \xi(\phi) R_{\rm GB}^2$, where $\xi$ is a function of the scalar field $\phi$, the existence of linearly stable stars with a nontrivial scalar profile without instabilities puts an upper bound on the strength of the dimensionless coupling constant $|\alpha|$. To realize maximum masses of NSs for a linear (or dilatonic) GB coupling $\alpha_{\rm GB}\phi R_{\rm GB}^2$ with typical nuclear equations of state, we obtain the theoretical upper limit $\sqrt{|\alpha_{\rm GB}|}<0.7~{\rm km}$. This is tighter than those obtained by the observations of gravitational waves emitted from binaries containing NSs. We also incorporate cubic-order scalar derivative interactions, quartic derivative couplings with nonminimal couplings to a Ricci scalar besides the scalar-GB coupling and show that NS solutions with a nontrivial scalar profile satisfying all the linear stability conditions are present for certain ranges of the coupling constants. In regularized 4-dimensional Einstein-GB gravity obtained from a Kaluza-Klein reduction with an appropriate rescaling of the GB coupling constant, we find that NSs in this theory suffer from a strong coupling problem as well as Laplacian instability of even-parity perturbations. We also study NS solutions with a nontrivial scalar profile in power-law $F(R_{\rm GB}^2)$ models, and show that they are pathological in the interior of stars and plagued by ghost instability together with the asymptotic strong coupling problem in the exterior of stars.",2207.04461v1 2022-11-24,Constraining constant and tomographic coupled dark energy with low-redshift and high-redshift probes,"We consider coupled dark energy (CDE) cosmologies, where dark matter particles feel a force stronger than gravity, due to the fifth force mediated by a scalar field which plays the role of dark energy. We perform for the first time a tomographic analysis of coupled dark energy, where the coupling strength is parametrized and constrained in different redshift bins. This allows us to verify which data can better constrain the strength of the coupling and how large the coupling can be at different epochs. First, we employ cosmic microwave background data from Planck, the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT), showing the impact of different choices that can be done in combining these datasets. Then, we use a range of low redshift probes to test CDE cosmologies, both for a constant and for a tomographic coupling. In particular, we use for the first time data from weak lensing (the KiDS-1000 survey), galaxy clustering (BOSS survey), and their combination, including 3x2pt galaxy-galaxy lensing cross-correlation data. We do not find evidence for nonzero coupling, either for a constant or tomographic case. A nonzero coupling is however still in agreement with current data. For CMB and background datasets, a tomographic coupling allows for $\beta$ values up to one order of magnitude larger than in previous works, in particular at $z<1$. The use of 3x2pt analysis then becomes important to constrain $\beta$ at low redshifts, even when coupling is allowed to vary: for 3x2pt we find, at $0.5 < z < 1$, $\beta=0.0180_{-0.011}^{+0.007}$, comparable to what CMB and background datasets would give for a constant coupling. This makes upcoming galaxy surveys potentially powerful probes to test CDE models at low redshifts. (abridged)",2211.13588v2 2023-03-02,Localization for random coupled harmonic oscillators on $\mathbb{Z}^d$,"In this paper we consider the localization properties of coupled harmonic oscillators in random media. Each of these oscillators is restricted to the lattice $\mathbb{Z}^d$. We show that for most states and an arbitrary choice of the random media, the long time localization for the coupled system holds in a time scale larger than the polynomial one.",2303.01077v1 2023-03-09,Statistical aspects of mean field coupled intermittent maps,"We study infinite systems of mean field weakly coupled intermittent maps in the Pomeau-Manneville scenario. We prove that the coupled system admits a unique ``physical'' stationary state, to which all absolutely continuous states converge. Moreover, we show that suitably regular states converge polynomially.",2303.05311v2 2023-02-21,Symmetry-Preserving Coupling Method for Topological Acoustic Metamaterials,"In this paper we investigate different types of couplings used in acoustic metamaterials requiring preservation of symmetries. For testing we use the SSH model to test whether topologically edge and interface modes are supported with the different types of connection. We observed that a modular platform where the resonators are coupled through the bottom is the simplest method that is accurate and flexible.",2303.06065v1 2023-07-11,Multisolitons in a gauged Skyrme-Maxwell model,"We construct new solutions of a $U(1)$ gauged Skyrme-Maxwell model of topological degrees $Q\leq 5$, which represent Skyrmions coupled to magnetic fluxes. It is found that, generically, in the strong coupling limit, coupling to the magnetic field results in transformation of the configuration to the toroidally shaped Skyrmions bounded to the local magnetic flux.",2307.05756v2 2023-08-20,Synchronization via impulsive deadbeat coupling,"For linear networks, where the coupling between the agents takes place through periodic impulses, a simple method is proposed for synchronization. It is shown that closing the loop by (normalized) deadbeat feedback gain produces synchronous behavior if the coupling strength $\mu$ is large enough. With such choice of control law, in the limiting case ($\mu\to\infty$) exact synchronization is achieved after $n$ periods, where $n$ is the order of individual agent dynamics.",2308.10237v1 2023-11-08,Validation of tight-binding model in system of two semiconductor single-electron lines coupled capacitively by Schroedinger formalism,"Validation of tight-binding model is given basing on two single-electron lines coupled perturbatively electrostatically in Schroedinger formalism. Scheme for conversion of quantum information from eigenenergy qubits to position based qubits is given. The procedure for determination of system ground is presented. Additional extension schemes of two coupled single-electron lines in case of Rabi oscillations occurring in each position based qubits are given.",2311.04411v1 2024-01-10,On the Martingale Schrödinger Bridge between Two Distributions,"We study a martingale Schr\""odinger bridge problem: given two probability distributions, find their martingale coupling with minimal relative entropy. Our main result provides Schr\""odinger potentials for this coupling. Namely, under certain conditions, the log-density of the optimal coupling is given by a triplet of real functions representing the marginal and martingale constraints. The potentials are also described as the solution of a dual problem.",2401.05209v1 1996-03-12,On Two-cavity Coupling,"This work presents research results on a novel analytical model of electromagnetic systems coupling through small size holes. The key problem regarding coupling of two cavities through an aperture in separating screen of finite thickness without making assumption on smallness of any parameters is considered. We are the first to calculate on the base of rigorous electromagnetic approach the coupling coefficients of the cylindrical cavities within the limit of small aperture and infinitely thin separating screen. The numeric results of electromagnetic characteristic dependencies that have been impossible to perform on the base of previous models are given.",9603002v1 2001-04-17,On the variation of the gauge couplings during inflation,"It is shown that the evolution of the (Abelian) gauge coupling during an inflationary phase of de Sitter type drives the growth of the two-point function of the magnetic inhomogeneities. After examining the constraints on the variation of the gauge coupling arising in a standard model of inflationary and post-inflationary evolution, magnetohydrodynamical equations are generalized to the case of time evolving gauge coupling. It is argued that large scale magnetic fields can be copiously generated. Other possible implications of the model are outlined.",0104290v1 2005-04-08,Varying Electromagnetic Coupling and Primordial Magnetic Fields,"We study the effect of variations of the electromagnetic coupling on the process of generation of primordial magnetic fields. We find that only through a significant growth of the electromagnetic coupling minimum seed fields can be produced. We also show that, if through some process in the early Universe the photon acquires a mass that leads, thanks to inflation, to the generation of primordial magnetic fields, then the influence of variations of the electromagnetic coupling amounts essentially to the results due to the photon effective mass alone.",0504211v1 2007-03-13,Limits on coupling between dark components,"DM--DE coupling can be a phenomenological indication of a common origin of the dark cosmic components. In this work we outline a new constraint to coupled--DE models: the coupling can partially or totally suppress the Meszaros effect, yielding transfered spectra with quite a soft bending above $k_{hor,eq}$. Models affected by this anomaly do not show major variation in the CMB anisotropy spectrum and it is herefore hard to reconcile them with both CMB and deep sample data, through the same value of the primeval spectral index.",0703303v2 1994-05-15,Bifurcations in Globally Coupled Map Lattices,"The dynamics of globally coupled map lattices can be described in terms of a nonlinear Frobenius--Perron equation in the limit of large system size. This approach allows for an analytical computation of stationary states and their stability. The complete bifurcation behaviour of coupled tent maps near the chaotic band merging point is presented. Furthermore the time independent states of coupled logistic equations are analyzed. The bifurcation diagram of the uncoupled map carries over to the map lattice. The analytical results are supplemented with numerical simulations.",9405009v1 1996-09-09,Disturbance propagation in chaotic extended systems with long-range coupling,"Propagation of initially localized perturbations is investigated in chaotic coupled map lattices with long-range couplings decaying as a power of the distance. The initial perturbation propagates exponentially fast along the lattice, with a rate given by the ratio of the maximal Lyapunov exponent and the power of the coupling. A complementary description in terms of a suitable comoving Lyapunov exponent is also given.",9609003v1 1998-05-14,Globally coupled maps with asynchronous updating,"We analyze a system of globally coupled logistic maps with asynchronous updating. We show that its dynamics differs considerably from that of the synchronous case. For growing values of the coupling intensity, an inverse bifurcation cascade replaces the structure of clusters and ordering in the phase diagram. We present numerical simulations and an analytical description based on an effective single-element dynamics affected by internal fluctuations. Both of them show how global coupling is able to suppress the complexity of the single-element evolution. We find that, in contrast to systems with synchronous update, internal fluctuations satisfy the law of large numbers.",9805015v1 1998-05-28,Time Delay Induced Death in Coupled Limit Cycle Oscillators,"We investigate the dynamical behaviour of two limit cycle oscillators that interact with each other via time delayed coupling and find that time delay can lead to amplitude death of the oscillators even if they have the same frequency. We demonstrate that this novel regime of amplitude ""death"" also exists for large collections of coupled identical oscillators and provide quantitative measures of this death region in the parameter space of coupling strength and time delay. Its implication for certain biological and physical applications is also pointed out.",9805029v1 1998-08-07,Cluster dynamics in systems with constant mean field coupling,"A procedure to predict the occurrence of periodic clusters in a system of globally coupled maps displaying a constant mean field is presented. The method employs the analogy between a system of globally coupled maps and a single map driven by a constant force. By obtaining the asymptotic orbits of the driven map, an associated coupling function can be constructed. This function allows to establish a direct connection between both systems. Some applications are shown.",9808009v1 1998-10-31,Phase slips and phase synchronization of coupled oscillators,"The behaviors of coupled oscillators, each of which has periodic motion with random natural frequency in the absence of coupling, are investigated. Some novel collective phenomena are revealed. At the onset of instability of the phase-locking state, simultaneous phase slips of all oscillators and quantized phase shifts in these phase slips are observed. By incresing the coupling, a bifurcation tree from high-dimensional quasiperiodicity to chaos to quasiperiodicity and periodicity is found. Different orders of phase synchronizations of chaotic oscillators and chaotic clusters play the key role for constructing this tree structure.",9811005v2 1998-11-05,Synchronous Behavior of Two Coupled Biological Neurons,"We report experimental studies of synchronization phenomena in a pair of biological neurons that interact through naturally occurring, electrical coupling. When these neurons generate irregular bursts of spikes, the natural coupling synchronizes slow oscillations of membrane potential, but not the fast spikes. By adding artificial electrical coupling we studied transitions between synchrony and asynchrony in both slow oscillations and fast spikes. We discuss the dynamics of bursting and synchronization in living neurons with distributed functional morphology.",9811010v1 1993-04-29,Impurity systems fluctuating between two magnetic configurations: candidates for non Fermi-liquid behavior,"The appropriate generalization of the isotropic impurity Anderson model for valence fluctuations between two magnetic multiplets $l^n$ and $l^{n+1}$ is solved in the strong-coupling limit of Wilson's renormalization group for $l\leq$ 3. Except in the extreme case of $j-j$ coupling, the ground state is degenerate, the impurity magnetic moment is very small and is overscreened by the conduction electrons. The strong-coupling fixed point turns out to be unstable. Thus, at low enough temperatures the physics of the systems should be governed by an intermediate coupling fixed point and non Fermi-liquid behavior is expected.",9304050v1 1994-01-29,Strong-Coupling Behavior of Two $t-J$ Chains with Interchain Single Electron Hopping,"Using the fermion-spin transformation to implement spin-charge separation of constrained electrons, a model of two $t-J$ chains with interchain single-electron hopping is studied by abelian bosonization. After spin-charge decoupling the charge dynamics can be trivially solved, while the spin dynamics is determined by a strong-coupling fixed point where the correlation functions can be calculated explicitly. This is a generalization of the Luther-Emery line for two-coupled $t-J$ chains. The interchain single-electron hopping changes the asymptotic behavior of the interchain spin-spin correlation functions and the electron Green function, but their exponents are independent of the coupling strength.",9401070v1 1994-02-15,Mode-Locking Hysteresis in the Globally Coupled Model of Charge-Density Waves,"We study the response of a recently proposed global coupling model of charge-density waves to a joint ac+dc drive. The model is the standard Fukuyama-Lee-Rice model with an additional global coupling term to account for interaction with (uncondensed) quasi-particles. We find that traditional mode-locking is accompanied by hysteresis on mode-locked steps. The experimentally observed asymmetry in the size of hysteresis is reproduced and explained by drawing attention to the importance of the pinning force. For large values of global coupling, increased rigidity leads to vanishing of subharmonic steps consistent with experiments.",9402057v1 1994-08-26,Phase Diagram for a Luttinger Liquid coupled to Phonons in one dimension,"The Green function and the ordering correlation functions of a system of electrons coupled to acoustic phonons are calculated explicitly. The sensitivity of the correlation function exponents to the Wentzel-Bardeen singularity is discussed. A phase diagram is established for the Hubbard model coupled to phonons, using the integral equations of Lieb and Wu. By increasing the filling factor towards half filling, the Wentzel-Bardeen singularity can be reached for arbitrary phonon coupling. This suppresses antiferromagnetic fluctuations and drives the system in a metallic phase, and ultimately in the triplet superconducting regime.",9408087v1 1995-11-03,A pair of interacting spins coupled to an environmental sea: dissipation and mutual decoherence,"We consider the quantum dynamics of two spin-1/2 systems, each coupled to a bath of oscillators, so that a bath-mediated coupling is generated between the spins. We find that the interactions destroys any coherent motion of the 2 spins, even if the coupling of each spin to the bath is quite weak, unless the interaction is extremely small. This is because the dynamic mutual bias between the spins blocks any coherent transitions between nearly degenerate states. In many quantum measurement operations this means that decoherence effects will be much stonger during the actual measurement",9511020v1 1995-12-08,Failure of Fermi-Liquid Theory at Strong Coupling,"We investigate quantitatively the effects of strong electron-electron coupling onto the dynamics of lattice electrons. To that purpose the self-consistent version of the bubble-chain approximation at zero temperature and half filling of the Anderson (Hubbard) model is used. Special attention is paid to a critical region of an electron-hole correlation function shaping the transition from weak to strong interaction. We find an analytic solution with Fermi-liquid properties on the weak-coupling side of the critical region around the two-particle pole. It is shown that Fermi-liquid theory does not lead to a consistent behavior of the self-consistent solution on the strong-coupling side of the critical region.",9512063v1 1995-12-10,Total dielectric function approach to the electron Boltzmann equation for scattering from a two-dimensional coupled mode system,"The nonequilibrium total dielectric function lends itself to a simple and general method for calculating the inelastic collision term in the electron Boltzmann equation for scattering from a coupled mode system. Useful applications include scattering from plasmon-polar phonon hybrid modes in modulation doped semiconductor structures. This paper presents numerical methods for including inelastic scattering at momentum-dependent hybrid phonon frequencies in the low-field Boltzmann equation for two-dimensional electrons coupled to bulk phonons. Results for mobility in GaAs show that the influence of mode coupling and dynamical screening on electron scattering from polar optical phonons is stronger for two-dimensional electrons than was previously found for the three dimensional case.",9512067v1 1996-05-27,Influence of electron-phonon interaction on superexchange,"We investigate the influence of electron-phonon coupling on the superexchange interaction of magnetic insulators. Both the Holstein-Hubbard model where the phonons couple to the electron density, as well as an extended Su, Schrieffer, Heeger model where the coupling arises from modulation of the overlap integral are studied using exact diagonalization and perturbative methods. In all cases for both the adiabatic (but non-zero frequency) and anti-adiabatic parameter regions the electron-phonon coupling is found to enhance the superexchange.",9605164v1 1996-06-12,A new perspective on the Holstein polaron problem,"The single-polaron band structure of the Holstein model in one and two dimensions is studied using a new form of resummed strong-coupling perturbation theory. Well converged results are obtained for phonon frequencies of the order of the hopping integral and strong to intermediate electron-phonon coupling. The polaron band structure at intermediate coupling is shown to deviate markedly from that of a nearest-neighbor tight-binding model, and is in fact similar in shape to the prediction of weak-coupling self-consistent perturbation theory.",9606082v1 1996-11-06,Incommensurate nodes in the energy spectrum of weakly coupled antiferromagnetic Heisenberg ladders,"Heisenberg ladders are investigated using the bond-mean-field theory [M.Azzouz, Phys. Rev. B 48, 6136 (1993)]. The zero inter-ladder coupling energy gap, the uniform spin susceptibility and the nuclear magnetic resonance spin-relaxation rate are calculated as a function of temperature and magnetic field. For weakly coupled ladders, the energy spectrum vanishes at incommensurate wavevectors giving rise to nodes. As a consequence, the spin susceptibility becomes linear at low temperature. Our results for the single ladder successfully compare to experiments on SrCu_2O_3 and (VO)_2P_2O_7 materials and new predictions concerning the coupling to the magnetic field are made.",9611049v1 1996-11-17,Weakly Coupled Antiferromagnetic Quantum Spin Chains,"Quasi-one-dimensional quantum antiferromagnets formed by a d-dimensional hypercubic lattice of weakly coupled spin-1/2 antiferromagnetic Heisenberg chains are studied by combining exact results in one-dimension and renormalization group analyses of the interchain correlations. It is shown that d-dimensional magnetic long-range order develops at zero-temperature for infinitesimal antiferromagnetic or ferromagnetic interchain couplings. In the presence of weak bond alternations, the order-disorder transition occurs at a finite interchain coupling. Relevances to the lightly doped quantum antiferromagnets and multi-layer quantum Hall systems are discussed.",9611129v2 1997-01-10,In-plane Magnetic Field Induced Kosterlitz-Thouless Type Metal Insulator Transition in Coupled Double Quantum Wells,"We study the localization properties in coupled double quantum wells with an in-plane magnetic field. The localization length is directly calculated using a transfer matrix technique and finite size scaling analysis. We show that the system maps into a 2D XY model and undergoes a disorder driven Kosterlitz-Thouless type metal-insulator transition depending on the coupling strength between the two-dimensional layers and the magnitude of the in-plane magnetic field. For a system with fixed disorder, the metallic regime appears to be a window in the magnetic field - coupling strength plane. Experimental implications of the transition will be discussed.",9701080v1 1997-02-20,Interchain Coupling Effects and Solitons in CuGeO_3,"The effects of interchain coupling on solitons and soliton lattice structures in CuGeO3 are explored. It is shown that interchain coupling substantially increases the soliton width and changes the soliton lattice structures in the incommensurate phase. It is proposed that the experimentally observed large soliton width in CuGeO3 is mainly due to interchain coupling effects.",9702185v2 1997-04-13,Localization in Highly Anisotropic Systems,"The localization behavior of the Anderson model with anisotropic hopping integral t for weakly coupled planes and weakly coupled chains is investigated both numerically with the transfer matrix method and analytically within the self-consistent theory of localization. It is found that the mobility edge is independent of the propagating direction. However, the correlation (localization) length in the extended (localized) side of the transition can be very different for the two directions. The critical disorder W$_c$ is found to vary from t$^{1 \over 4}$ for weakly coupled planes to t$^{1 \over 2}$ for weakly coupled chains.",9704107v1 1997-04-24,Structural Aspects of Magnetic Coupling in CaV4O9,"The strong corrugation of the V4O9 layer in the spin gap system CaV4O9 is examined for its impact on the exchange coupling constants between the spin 1/2 V ions. Local spin density (LSD) calculations show that the V spin occupies a d(x^2-y^2) orbital (x and y are the V-V directions). The Kanamori-Goodenough superexchange rules, and the degeneracy of ferromagnetic and antiferromagnetic alignments within LSD, suggest that 2nd neighbor couplings dominate over nearest neighbor, resulting in two coupled S=1/2 metaplaquette systems.",9704203v1 1996-05-15,Solitons in polymeric chains with periodic interactions,"In this paper we follow the lines of recent works to investigate systems of two coupled real scalar fields defined by potentials that describe periodic interactions between the scalar fields. We work with polymeric chains containing periodic interactions between the coupled fields, and we investigate the topological sectors to obtain explicit soliton solutions and their corresponding energy. In particular, we offer an example that considers deoxyribonucleic acid (DNA) as a system of coupled fields, and we present the main steps to describe DNA as a polymeric chain belonging to the class of systems of two coupled real scalar fields.",9705164v1 1997-05-30,Exchange coupling between magnetic layers across non-magnetic superlattices,"The oscillation periods of the interlayer exchange coupling are investigated when two magnetic layers are separated by a metallic superlattice of two distinct non-magnetic materials. In spite of the conventional behaviour of the coupling as a function of the spacer thickness, new periods arise when the coupling is looked upon as a function of the number of cells of the superlattice. The new periodicity results from the deformation of the corresponding Fermi surface, which is explicitly related to a few controllable parameters, allowing the oscillation periods to be tuned.",9705310v2 1997-06-06,Hole doping and weak quenched disorder effects on the 1D Kondo lattice for ferromagnetic Kondo couplings,"We investigate the one-dimensional Kondo lattice model (1D KLM) for ferromagnetic Kondo couplings, by using the bosonization method. The ferromagnet ic 2-leg spin ladder and the S=1 antiferromagnet occur as new one-dimensional Kondo insulators, for a half-filled band. First,a very small hole-doping makes the charge sector massless and it can produce, either an incommensurate RKKY interaction or a S=1 ferromagnet according to the strength of the ferromagnetic Kondo coupling. Second, we investigate, the effects of a weak and quenched disorder on these two Kondo insulators, by applying renormalization group methods: the Anderson localization is suppressed only in the context of a strong ferromagnetic Kondo coupling.",9706068v1 1997-12-19,Generation of Large Moments in a Spin-1 Chain with Random Antiferromagnetic Couplings,"We study the spin-1 chain with nearest neighbor couplings that are rotationally invariant, but include both Heisenberg and biquadratic exchange, with random strengths. We demonstrate, using perturbative renormalization group methods as well as exact diagonalization of clusters, that the system generates ferromagnetic couplings under certain circumstances even when all the bare couplings are antiferromagnetic. This disorder induced instability leads to formation of large magnetic moments at low temperatures, and is a purely quantum mechanical effect that does not have a classical counterpart. The physical origin of this instability, as well as its consequences, are discussed.",9712252v1 1998-02-14,Strong Coupling Approach to the d-p Model on the Basis of Fermi Liquid Theory,"We study the superconducting transition temperature $T_c$ of the bilayer d-p model with $d_{x^2-y^2}$-wavelike attractive interaction based on the formalism first employed by Nozi\`{e}res and Schmitt-Rink. In the strong coupling regime, $T_c$ obtained through this formalism are much suppressed, compared with those through Thouless criterion only. We also find that, whether the interlayer coupling exsists or not, $T_c$ is almost propotional to the Fermi energy in the strong coupling regime. Thus, we can reproduce the essential nature in the underdoped region.",9802157v1 1998-06-23,Coupling between membrane tilt-difference and dilation: a new ``ripple'' instability and multiple crystalline inclusions phases,"A continuum Landau theory for the micro-elasticity of membranes is discussed, which incorporates a coupling between the bilayer thickness variation and the difference in the two monolayers' tilts. This coupling stabilizes a new phase with a rippled micro-structure. Interactions among membrane inclusions combine a dilation-induced attraction and a tilt-difference-induced repulsion that yield 2D crystal phases, with possible coexistence of different lattice spacings for large couplings. Inclusions favoring crystals are those with either a long-convex or a short-concave hydrophobic core.",9806269v1 1999-10-25,Electron-phonon and spin-phonon coupling in NaV$_{2}$O$_{5}$: charge fluctuations effect,"We show that the asymmetric crystal environment of the V site in the ladder compound NaV$_{2}$O$_{5}$ leads to a strong coupling of vanadium 3d electrons to phonons. This coupling causes fluctuations of the charge on the V ions, and favors a transition to a charge-ordered state at low temperatures. In the low temperature phase the charge fluctuations modulate the spin-spin superexchange interaction, resulting in a strong spin-phonon coupling.",9910403v1 1999-10-26,Mode-coupling theory for heteropolymers,"We study the Langevin dynamics of a heteropolymer by means of a mode-coupling approximation scheme, giving rise to a set of coupled integro-differential equations relating the response and correlation functions. The analysis shows that there is a regime at low temperature characterized by out-of-equilibrium dynamics, with violation of time-translational invariance and of the fluctuation-dissipation theorem. The onset of ageing dynamics at low temperatures gives new insight into the nature of the slow dynamics of a disordered polymer. We also introduce a renormalization-group treatment of our mode-coupling equations, which supports our analysis, and might be applicable to other systems.",9910431v1 1999-11-18,Statistics of Wave Functions in Coupled Chaotic Systems,"Using the supersymmetry technique, we calculate the joint distribution of local densities of electron wavefunctions in two coupled disordered or chaotic quantum billiards. We find novel spatial correlations that are absent in a single chaotic system. Our exact result can be interpreted for small coupling in terms of the hybridization of eigenstates of the isolated billiards. We show that the presented picture is universal, independent of microscopic details of the coupling.",9911284v2 1999-11-24,Josephson Current Flowing in Cyclically Coupled Bose-Einstein Condensates,"The Josephson effect in cyclically coupled Bose-Einstein condensates is studied theoretically. We analyze the simultaneous Gross-Pitaevskii equations with coupling terms between adjacent condensates. Depending on the initial relative phases between condensates, Josephson current flows cyclically to make a quantized vortex. Reducing the coupling between condensates changes the motion from periodic to chaotic, thus suppressing the cyclic current. The relation to the Kibble-Zurek mechanism is discussed.",9911389v2 2000-01-31,Phase Ordering in Chaotic Map Lattices with Additive Noise,"We present some result about phase separation in coupled map lattices with additive noise. We show that additive noise acts as an ordering agent in this class of systems. In particular, in the weak coupling region, a suitable quantity of noise leads to complete ordering. Extrapolating our results at small coupling, we deduce that this phenomenon could take place also in the limit of zero coupling.",0001444v1 2000-07-11,Strong-Coupling Expansions for Multiparticle Excitations: Continuum and Bound States,"We present a new linked cluster expansion for calculating properties of multiparticle excitation spectra to high orders. We use it to obtain the two-particle spectra for systems of coupled spin-half dimers. We find that even for weakly coupled dimers the spectrum is very rich, consisting of many bound states. The number of bound states depends on both geometry of coupling and frustration. Many of the bound states can only be seen by going to sufficiently high orders in the perturbation theory, showing the extended character of the pair-attraction.",0007192v1 2000-08-23,Field-Induced Gaps in the Frustrated Spin Ladder,"We study the magnetization process of the $S=1/2$ antiferromagnetic spin ladder in the presence of the second and the third-neighbor couplings which lead to frustration with the typical nearest-neighbor coupling. We use degenerate perturbation theory and level spectroscopy analysis of the numerical diagonalization data of the Hamiltonian for finite systems. We find two kinds of plateaux at half the saturation moment in the magnetization curve. One is mainly due to the second-neighbor couplings and the other to the third-neighbor couplings. The mechanisms of these two plateaux are quite different with each other.",0008328v1 2000-09-25,Strong-Coupling Theory for Counter-Ion Distributions,"The Poisson-Boltzmann approach gives asymptotically exact counter-ion density profiles around charged objects in the weak-coupling limit of low valency and high temperature. In this paper we derive, using field-theoretic methods, a theory which becomes exact in the opposite limit of strong coupling. Formally, it corresponds to a standard virial expansion. Long-range divergences, which render the virial expansion intractable for homogeneous bulk systems, are shown to be renormalizable for the case of inhomogeneous distribution functions by a systematic expansion in inverse powers of the coupling parameter. For a planar charged wall, our analytical results compare quantitatively with extensive Monte-Carlo simulations.",0009376v1 2000-11-08,Interlayer Exchange Coupling Mediated by Valence Band Electrons,"The interlayer exchange coupling mediated by valence band electrons in all-semiconductor IV-VI magnetic/nonmagnetic superlattices is studied theoretically. A 3D tight-binding model, accounting for the band and magnetic structure of the constituent superlattice components is used to calculate the spin-dependent part of the total electronic energy. The antiferromagnetic coupling between ferromagnetic layers in EuS/PbS superlattices is obtained, in agreement with the experimental evidences. The results obtained for the coupling between antiferromagnetic layers in EuTe/PbTe superlattices are also presented.",0011135v1 2000-11-10,Stretched exponential relaxation in the mode-coupling theory for the Kardar-Parisi-Zhang equation,"We study the mode-coupling theory for the Kardar-Parisi-Zhang equation in the strong-coupling regime, focusing on the long time properties. By a saddle point analysis of the mode-coupling equations, we derive exact results for the correlation function in the long time limit - a limit which is hard to study using simulations. The correlation function at wavevector k in dimension d is found to behave asymptotically at time t as C(k,t)\simeq 1/k^{d+4-2z} (Btk^z)^{\gamma/z} e^{-(Btk^z)^{1/z}}, with \gamma=(d-1)/2, A a determined constant and B a scale factor.",0011191v1 2000-12-19,Self-duality in Maxwell-Chern-Simons theories with non minimal coupling with field,"We consider a general class of non-local MCS models whose usual minimal coupling to a conserved current is supplemented with a (non-minimal) magnetic Pauli-type coupling. We find that the considered models exhibit a self-duality whenever the magnetic coupling constant reaches a special value: the partition function is invariant under a set of transformations among the parameter space (the duality transformations) while the original action and its dual counterpart have the same form. The duality transformations have a structure similar to the one underlying self-duality of the (2+1)-dimensional Zn-abelian Higgs model with Chern-Simons and bare mass term.",0012360v1 2000-12-27,Correlation induced phonon softening in low density coupled bilayer systems,"We predict a possible phonon softening instability in strongly correlated coupled semiconductor bilayer systems. By studying the plasmon-phonon coupling in coupled bilayer structures, we find that the renormalized acoustic phonon frequency may be softened at a finite wave vector due to many-body local field corrections, particularly in low density systems where correlation effects are strong. We discuss experimental possibilities to search for this predicted phonon softening phenomenon.",0012482v1 2001-01-24,Coupling of Nonlocal Potentials to Electromagnetic Fields,"Nonlocal Hamiltonians are used widely in first-principles quantum calculations; the nonlocality stems from eliminating undesired degrees of freedom, e.g. core electrons. To date, attempts to couple nonlocal systems to external electromagnetic (EM) fields have been heuristic or limited to weak or long wavelength fields. Using Feynman path integrals, we derive an exact, closed-form coupling of arbitrary EM fields to nonlocal systems. Our results justify and clarify the couplings used to date and are essential for systematic computation of linear and especially nonlinear response.",0101383v3 2001-01-29,Dynamics of order parameters for a population of globally coupled oscillators,"Using an expansion in order parameters, the equation of motion for the centroid of globally coupled oscillators with natural frequencies taken from a distribution is obtained for the case of high coupling, low dispersion of natural frequencies and any number of oscillators. To the first order, the system can be approximated by a set of four equations, where the centroid is coupled with a second macroscopic variable, which describes the dynamics of the oscillators around their average. This gives rise to collective effects that suggest experiments aimed at measuring the parameters of the population.",0101441v1 2001-03-27,"Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps","Density-functional calculations of the phonon spectrum and electron-phonon coupling in MgB$_2$ are presented. The $E_{2g}$ phonons, which involve in-plane B displacements, couple strongly to the $p_{x,y}$ electronic bands. The isotropic electron-phonon coupling constant is calculated to be about 0.8. Allowing for different order parameters in different bands, the superconducting $\lambda$ in the clean limit is calculated to be significantly larger. The $E_{2g}$ phonons are strongly anharmonic, and the non-linear contribution to the coupling between the $E_{2g}$ modes and the p$_{x,y}$ bands is significant.",0103570v1 2001-04-02,Decoherence and dephasing in coupled Josephson-junction qubits,"We investigate the decoherence and dephasing of two coupled Josephson qubits. With the interaction between the qubits being generated by current-current correlations, two different situations in which the qubits are coupled to the same bath, or to two independent baths, are considered. Upon focussing on dissipation being caused by the fluctuations of voltage sources, the relaxation and dephasing rates are explicitly evaluated. Analytical and numerical results for the coupled qubits dynamics are provided.",0104023v1 2001-05-14,Charge spectrometry with a strongly coupled superconducting single-electron transistor,"We have used a superconducting single-electron transistor as a DC-electrometer that is strongly coupled to the metal island of another transistor. With this set-up, it is possible to directly measure the charge distribution on this island. The strong capacitive coupling was achieved by a multilayer fabrication technique that allowed us to make the coupling capacitance bigger than the junction capacitances. Simulations of this system were done using orthodox theory of single-electron tunnelling and showed excellent agreement with the measurements.",0105263v1 2001-07-20,Raman Response in Antiferromagnetic Two-Leg S=1/2 Heisenberg Ladders,"The Raman response in the antiferromagnetic 2-leg S=1/2 Heisenberg ladder is calculated for various couplings by continuous unitary transformations. For leg couplings above 80% of the rung coupling a characteristic 2-peak structure occurs with a point of zero intensity within the continuum. Experimental data for CaV_2O_5 and La_yCa_(14-y)Cu_24O_41 are analyzed and the coupling constants are determined. Evidence is found that the Heisenberg model is not sufficient to describe cuprate ladders. We argue that a cyclic exchange term is the appropriate extension.",0107431v1 2001-07-27,Nonlinear coupling between scissors modes of a Bose-Einstein condensate,"We explore the nonlinear coupling of the three scissors modes of an anisotropic Bose-Einstein condensate. We show that only when the frequency of one of the scissors modes is twice the frequency of another scissors mode, these two modes can be resonantly coupled and a down conversion can occur. We perform the calculation variationally using a gaussian trial wave function. This enables us to obtain simple analytical results that describe the oscillation and resonance behaviour of the two coupled modes.",0107567v1 2001-09-19,Charge transport through quantum dots via time-varying tunnel couplings,"We describe a novel mechanism for charge pumping through tunnel-coupled quantum dots in the regime of strong Coulomb blockade. The quantum state of an additional electron within the structure is steered by changing the tunneling couplings between neighbouring dots. Appropriate tailoring of the interdot tunneling rates allows to design the instantaneous eigenvalues of the system Hamiltonian. A combination of adiabatic following and Landau-Zener tunneling results in the transfer of charge from one dot to the neighbouring one. Coupling to electron reservoirs via weak tunnel-barriers then allows to implement an electron pump.",0109335v1 2001-11-09,"Strong-Coupling Effects in ""Dirty"" Superfluid $^3He$","The contribution of the strong-coupling effects to the free energy of the ""dirty"" superfluid $^3He$ is estimated using a simple model. It is shown that the strong-coupling effects are less susceptible to the quasiparticle scattering events in comparison to the weak-coupling counterpart. This supports the conclusion about stabilization of the $B$-phase in aerogel environment at pressures where the $A$-phase takes over in bulk superfluid $^3He$, in accordance with recent experimental observations in zero magnetic field.",0111161v2 2001-12-06,Aharonov-Bohm oscillations of a particle coupled to dissipative environments,"The amplitude of the Bohm-Aharonov oscillations of a particle moving around a ring threaded by a magnetic flux and coupled to different dissipative environments is studied. The decay of the oscillations when increasing the radius of the ring is shown to depend on the spatial features of the coupling. When the environment is modelled by the Caldeira-Leggett bath of oscillators, or the particle is coupled by the Coulomb potential to a dirty electron gas, interference effects are suppressed beyond a finite length, even at zero temperature. A finite renormalization of the Aharonov-Bohm oscillations is found for other models of the environment.",0112099v2 2001-12-18,System size resonance in coupled noisy systems and in the Ising model,"We consider an ensemble of coupled nonlinear noisy oscillators demonstrating in the thermodynamic limit an Ising-type transition. In the ordered phase and for finite ensembles stochastic flips of the mean field are observed with the rate depending on the ensemble size. When a small periodic force acts on the ensemble, the linear response of the system has a maximum at a certain system size, similar to the stochastic resonance phenomenon. We demonstrate this effect of system size resonance for different types of noisy oscillators and for different ensembles -- lattices with nearest neighbors coupling and globally coupled populations. The Ising model is also shown to demonstrate the system size resonance.",0112338v1 2002-04-16,Charge Pumping in Mesoscopic Systems coupled to a Superconducting Lead,"We derive a general scattering-matrix formula for the pumped current through a mesoscopic region attached to a normal and a superconducting lead. As applications of this result we calculate the current pumped through (i) a pump in a wire, (ii) a quantum dot in the Coulomb blockade regime, and (iii) a ballistic double-barrier junction, all coupled to a superconducting lead. Andreev reflection is shown to enhance the pumped current by up to a factor of 4 in case of equal coupling to the leads. We find that this enhancement can still be further increased for slightly asymmetric coupling.",0204340v1 2002-06-16,Frequency behavior of Raman coupling coefficient in glasses,"Low-frequency Raman coupling coefficient of 11 different glasses is evaluated. It is found that the coupling coefficient demonstrates a universal linear frequency behavior near the boson peak maximum and a superlinear behavior at very low frequencies. The last observation suggests vanishing of the coupling coefficient when frequency tends to zero. The results are discussed in terms of the vibration wavefunction that combines features of localized and extended modes.",0206295v1 2002-07-18,Disentangling the exchange coupling of entangled donors in the Si quantum computer architecture,"We develop a theory for micro-Raman scattering by single and coupled two-donor states in silicon. We find the Raman spectra to have significant dependence on the donor exchange splitting and the relative spatial positions of the two donor sites. In particular, we establish a strong correlation between the temperature dependence of the Raman peak intensity and the interdonor exchange coupling. Micro-Raman scattering can therefore potentially become a powerful tool to measure interqubit coupling in the development of a Si quantum computer architecture.",0207455v2 2002-08-22,"Spin-Orbit Coupling, Antilocalization, and Parallel Magnetic Fields in Quantum Dots","We investigate antilocalization due to spin-orbit coupling in ballistic GaAs quantum dots. Antilocalization that is prominent in large dots is suppressed in small dots, as anticipated theoretically. Parallel magnetic fields suppress both antilocalization and also, at larger fields, weak localization, consistent with random matrix theory results once orbital coupling of the parallel field is included. In situ control of spin-orbit coupling in dots is demonstrated as a gate-controlled crossover from weak localization to antilocalization.",0208436v2 2002-08-26,Characterization of the stretched exponential trap-time distributions in one-dimensional coupled map lattices,"Stretched exponential distributions and relaxation responses are encountered in a wide range of physical systems such as glasses, polymers and spin glasses. As found recently, this type of behavior occurs also for the distribution function of certain trap time in a number of coupled dynamical systems. We analyze a one-dimensional mathematical model of coupled chaotic oscillators which reproduces an experimental set-up of coupled diode-resonators and identify the necessary ingredients for stretched exponential distributions.",0208487v1 2002-09-21,Dynamical spin-electric coupling in a quantum dot,"Due to the spin-orbital coupling in a semiconductor quantum dot, a freely precessing electron spin produces a time-dependent charge density. This creates a sizeable electric field outside the dot, leading to promising applications in spintronics. The spin-electric coupling can be employed for non-invasive single spin detection by electrical methods. We also consider a spin relaxation mechanism due to long-range coupling to electrons in gates and elsewhere in the system, and find a contribution comparable to, and in some cases dominant over previously discussed mechanisms.",0209507v1 2002-10-27,Effect of Pr doping on the superconductivity and interlayer coupling of Bi2Sr2-xPrxCa1Cu2Oy system,"The effect of Pr substitution on the superconductivity and interlayer coupling of Bi2212 system is investigated. Magnetic and transport measurements were performed for purposes of characterization. The superconducting transition temperature Tc first increased and then decreased till it became zero at x=0.6. The effective superconducting volume also decreases due to Pr substitution. From the fluctuation conductivity analyses it is found that the interlayer coupling constant J decreases monotonically with increase of the Pr content. This result shows that the Pr doping weakens the CuO2 interlayer coupling of Bi2212 system due to the loss of local superconductivity in the CuO2 layers.",0210595v1 2002-10-31,Coexistence of Coherence and Incoherence in Nonlocally Coupled Phase Oscillators,"The phase oscillator model with global coupling is extended to the case of finite-range nonlocal coupling. Under suitable conditions, peculiar patterns emerge in which a quasi-continuous array of identical oscillators separates sharply into two domains, one composed of mutually synchronized oscillators with unique frequency and the other composed of desynchronized oscillators with distributed frequencies. We apply a theory similar to the one which successfully explained the onset of collective synchronization in globally coupled phase oscillators with frequency distribution. A space-dependent order parameter is thus introduced, and an exact functional self-consistency equation is derived for this quantity. Its numerical solution is confirmed to reproduce the simulation results accurately.",0210694v1 2003-01-07,Noise-induced macroscopic bifurcations in populations of globally coupled maps,"Populations of globally coupled identical maps subject to additive, independent noise are studied in the regimes of strong coupling. Contrary to each noisy population element, the mean field dynamics undergoes qualitative changes when the noise strength is varied. In the limit of infinite population size, these macroscopic bifurcations can be accounted for by a deterministic system, where the mean-field, having the same dynamics of each uncoupled element, is coupled with other order parameters. Different approximation schemes are proposed for polynomial and exponential functions and their validity discussed for logistic and excitable maps.",0301056v1 2003-01-23,Mode Repulsion and Mode Coupling in Random Lasers,"We studied experimentally and theoretically the interaction of lasing modes in random media. In a homogeneously broadened gain medium, cross gain saturation leads to spatial repulsion of lasing modes. In an inhomogeneously broadened gain medium, mode repulsion occurs in the spectral domain. Some lasing modes are coupled through photon hopping or electron absorption and reemission. Under pulsed pumping, weak coupling of two modes leads to synchronization of their lasing action. Strong coupling of two lasing modes results in anti-phased oscillations of their intensities.",0301461v1 2003-03-24,Electron-phonon interaction and coupled phonon--plasmon modes,"The theory of Raman scattering by the electron--phonon coupled system in metals and heavily doped semiconductors is developed taking into account the Coulomb screening and the electron--phonon deformation interaction. The Boltzmann equation for carriers is applied. Phonon frequencies and optic coupling constants are renormalized due to interactions with carriers. The $k-$dependent semiclassical dielectric function is involved instead of the Lindhard-Mermin expression. The results of calculations are presented for various values of carrier concentration and electron-phonon coupling constant.",0303503v1 2003-03-28,Effect of Antiferromagnetic Interlayer Coupling on Current-Assisted Magnetization Switching,"We compare magnetization switching in Co/Cu/Co nanopillars with uncoupled and dipole-field coupled Co layers. In uncoupled nanopillars, current-driven switching is hysteretic at low magnetic field H and changes to reversible, characterized by telegraph noise, at high H. We show that dipolar coupling both affects the switching current and causes the switching to become reversible at small H. The coupling thus changes the switching to reversible, hysteretic, and then reversible again as H increases. We describe our results in terms of current-assisted thermal activation.",0303614v1 2003-04-12,Effect of Interlayer Coupling on Current-Assisted Magnetization Switching in Nanopillars,"We show that dipole-field induced antiferromagnetic coupling, or RKKY ferromagnetic coupling, between Co layers can strongly affect the low magnetic field switching behavior of Co/Cu/Co nanopillars. Whereas current-assisted switching at low fields in uncoupled nanopillars is always hysteretic, strong coupling of either kind can change the switching to non-hysteretic (reversible). These differences can be understood with a simple picture of current-assisted thermal activation over a barrier.",0304299v1 2003-04-28,Ferromagnetism and Superconductivity in the multi-orbital Hubbard Model: Hund's Rule Coupling versus Crystal-Field Splitting,"The multi-orbital Hubbard model in one dimension is studied using the numerical diagonalization method. Due to the effect of the crystal-field splitting $\Delta$, the fully polarized ferromagnetism which is observed in the strong coupling regime becomes unstable against the partially polarized ferromagnetism when the Hund's rule coupling $J$ is smaller than a certain critical value of order of $\Delta$. In the vicinity of the partially polarized ferromagnetism, the orbital fluctuation develops due to the competition between the Hund's rule coupling and the crystal-field splitting. The superconducting phase with the Luttinger liquid parameter $K_{\rho}>1$ is observed for the singlet ground state in this region.",0304620v1 2003-05-01,Negative differential resistance due to the resonance coupling of a quantum-dot dimer,"Electron tunneling through a coupled quantum-dot dimer under a dc-bias is investigated. We find that a peak in the $I$-$V$ curve appears at low temperature when two discrete electronic states in the two quantum dots are aligned with each other -- resonance coupling. This leads to a negative differential resistance. The peak height and width depend on the dot-dot coupling. At high temperature, the peak disappears due to thermal smearing effects.",0305018v1 2003-06-11,Relative phase fluctuations of two coupled one-dimensional condensates,"We study the relative phase fluctuations of two one-dimensional condensates coupled along their whole extension with a local single-atom interaction. The thermal equilibrium is defined by the competition between independent longitudinal thermally excited phase fluctuations and the coupling between the condensates which locally favors identical phase. We compute the relative phase fluctuations and their correlation length as a function of the temperature and the strength of the coupling.",0306282v2 2003-06-13,Controllable manipulation and entanglement of macroscopic quantum states in coupled charge qubits,"We present an experimentally implementable method to couple Josephson charge qubits and to generate and detect macroscopic entangled states. A large-junction superconducting quantum interference device is used in the qubit circuit for both coupling qubits and implementing the readout. Also, we explicitly show how to achieve a microwave-assisted macroscopic entanglement in the coupled-qubit system.",0306363v2 2003-07-02,Ferromagnetic phase transition and Bose-Einstein condensation in spinor Bose gases,"Phase transitions in spinor Bose gases with ferromagnetic (FM) couplings are studied via mean-field theory. We show that an infinitesimal value of the coupling can induce a FM phase transition at a finite temperature always above the critical temperature of Bose-Einstein condensation. This contrasts sharply with the case of Fermi gases, in which the Stoner coupling $I_s$ can not lead to a FM phase transition unless it is larger than a threshold value $I_0$. The FM coupling also increases the critical temperatures of both the ferromagnetic transition and the Bose-Einstein condensation.",0307063v1 2003-08-22,Intriguing Heat Conduction of a Polymer Chain,"We study heat conduction in a one-dimensional chain of particles with longitudinal as well as transverse motions. The particles are connected by two-dimensional harmonic springs together with bending angle interactions. Using equilibrium and nonequilibrium molecular dynamics, three types of thermal conducting behaviors are found: a logarithmic divergence with system sizes for large transverse coupling, 1/3 power-law at intermediate coupling, and 2/5 power-law at low temperatures and weak coupling. The results are consistent with a simple mode-coupling analysis of the same model. The 1/3 power-law divergence should be a generic feature for models with transverse motions.",0308445v1 2003-10-20,Spin Blockade in Capacitively Coupled Quantum Dots,"We present transport measurements on a lateral double dot produced by combining local anodic oxidation and electron beam lithography. We investigate the tunability of our device and demonstrate, that we can switch between capacitive and tunnel coupling. In the regime of capacitive coupling we observe the phenomenon of spin blockade in a magnetic field and analyze the influence of capacitive interdot coupling on this effect.",0310469v1 2003-11-14,Spin-orbit coupling and Berry phase with ultracold atoms in 2D optical lattices,"We show how spin-orbit coupling and Berry phase can appear in two-dimensional optical lattices by coupling atoms' internal degrees of freedom to radiation. The Rashba Hamiltonian, a standard description of spin-orbit coupling for two-dimensional electrons, is obtained for the atoms under certain circumstances. We discuss the possibility of observing associated phenomena, such as the anomalous Hall and spin Hall effects, with cold atoms in optical lattices.",0311356v2 2003-12-04,Generalized scaling relations for unidirectionally coupled nonequilibrium systems,"Unidirectionally coupled systems which exhibit phase transitions into an absorbing state are investigated at the multicritical point. We find that for initial conditions with isolated particles, each hierarchy level exhibits an inhomogeneous active region, coupled and uncoupled respectively. The particle number of each level increases algebraically in time as $N(t) \sim t^{\eta}$ with different exponents $\eta$ in each domain. This inhomogeneity is a quite general feature of unidirectionally coupled systems and leads to two hyperscaling relations between dynamic and static critical exponents. Using the contact process and the branching-annihilating random walk with two offsprings, which belong to the DP and PC classes respectively, we numerically confirm the scaling relations.",0312136v1 2004-02-10,First-order Synchronization Transition in Locally Coupled Maps,"We study a family of diffusively coupled chaotic maps on periodic d-dimensional square lattices. Even and odd sub-lattices are updated alternately, introducing an effective delay. As the coupling strength is increased, the system undergoes a first order phase transition from a multi-stable to a synchronized phase. Further increase in coupling strength shows de-synchronization where the phase space splits into two ergodic regions. We argue that the de-synchronization transition is discontinuous for piece-wise linear maps, and is continuous for non-linear maps which are differentiable.",0402283v1 2004-02-27,Coupling Josephson qubits via a current-biased information bus,"Josephson qubits without direct interaction can be effectively coupled by sequentially connecting them to an information bus: a current-biased large Josephson junction treated as an oscillator with adjustable frequency. The coupling between any qubit and the bus can be controlled by modulating the magnetic flux applied to that qubit. This tunable and selective coupling provides two-qubit entangled states for implementing elementary quantum logic operations, and for experimentally testing Bell's inequality.",0402678v2 2004-06-02,Multi-terminal transport through a quantum dot in the Coulomb blockade regime,"Three terminal tunnelling experiments on quantum dots in the Coulomb blockade regime allow a quantitative determination of the coupling strength of individual quantum states to the leads. Exploiting this insight we have observed independent fluctuations of the coupling strengths as a function of electron number and magnetic field due to changes in the shape of the wave function in the dot. Such a detailed understanding and control of the dot-lead coupling can be extended to more complex systems such as coupled dots, and is essential for building functional quantum electronic systems.",0406046v1 2004-10-04,Dephasing of coupled spin qubit system during gate operations due to background charge fluctuations,"It has been proposed that a quantum computer can be constructed based on electron spins in quantum dots or based on a superconducting nanocircuit. During two-qubit operations, the fluctuation of the coupling parameters is a critical factor. One source of such fluctuation is the stirring of the background charges. We focused on the influence of this fluctuation on a coupled spin qubit system. The induced fluctuation in exchange coupling changes the amount of entanglement, fidelity, and purity. In our previous study, the background charge fluctuations were found to be an important channel of dephasing for a single Josephson qubit.",0410060v1 2004-10-11,Electron Correlations in a Quantum Dot with Bychkov-Rashba Coupling,"We report on a theoretical approach developed to investigate the influence of Bychkov-Rashba interaction on a few interacting electrons confined in a quantum dot. We note that the spin-orbit coupling profoundly influences the energy spectrum of interacting electrons in a quantum dot. Inter-electron interaction causes level crossings in the ground state and a jump in magnetization. As the coupling strength is increased, that jump is shifted to lower magnetic fields. Low-field magnetization will therefore provide a direct probe of the spin-orbit coupling strength in a quantum dot.",0410248v1 2004-11-06,Rectification in single molecular dimers with strong polaron effect,"We study theoretically the transport properties of a molecular two level system with large electron-vibron coupling in the Coulomb blockade regime. We show that when the electron-vibron coupling induces polaron states, the current-voltage characteristic becomes strongly asymmetric because, in one current direction, one of the polaron state blocks the current through the other. This situation occurs when the coupling between the polaron states is smaller than the coupling to the leads. We discuss the relevance of our calculation for experiments on C_140 molecules.",0411173v2 2004-11-10,Maxwell Equation for the Coupled Spin-Charge Wave Propagation,"We show that the dissipationless spin current in the ground state of the Rashba model gives rise to a reactive coupling between the spin and charge propagation, which is formally identical to the coupling between the electric and the magnetic fields in the 2+1 dimensional Maxwell equation. This analogy leads to a remarkable prediction that a density packet can spontaneously split into two counter propagation packets, each carrying the opposite spins. In a certain parameter regime, the coupled spin and charge wave propagates like a transverse ""photon"". We propose both optical and purely electronic experiments to detect this effect.",0411276v1 2004-12-16,Magnetoelastic Coupling in the Spin-Dimer System TlCuCl$_3$,"We present high-resolution measurements of the thermal expansion and the magnetostriction of TlCuCl$_{3}$ which shows field-induced antiferromagnetic order. We find pronounced anomalies in the field and temperature dependence of different directions of the lattice signaling a large magnetoelastic coupling. The phase boundary is extremely sensitive to pressure, e.g. the transition field would change by about +/- 185$%/GPa under uniaxial pressure applied along certain directions. This drastic effect can unambiguously be traced back to changes of the intradimer coupling under uniaxial pressure. The interdimer couplings remain essentially unchanged under pressure, but strongly change when Tl is replaced by K.",0412451v1 2005-01-25,Time evolution and decoherence of entangled states realized in coupled superconducting flux qubits,"We study theoretically how decoherence affects superposition states composed of entangled states in inductively coupled two superconducting flux-qubits. We discover that the quantum fluctuation of an observable in a coupled flux-qubit system plays a crucial role in decoherence when the expectation value of the observable is zero. This examplifies that decoherence can be also induced through a quantum mechanically higher-order effect. We also find that there exists a decoherence free subspace for the environment coupled via a charge degree of freedom of the qubit system.",0501581v2 2005-02-09,Bridge-mediated Donor-Acceptor Effective Coupling: Exact theoretical description,"An exact expression of the bridge-mediated donor-acceptor effective coupling, is derived. For systems represented by a tight-binding Hamiltonian with nearest-neighbor interactions, we show that the effective coupling, is equal to the product over all square of nearest-neighbor couplings divided by an appropriate product of level spacing of eigen energies of the Hamiltonian. Results of this calculation are compared to those obtained by perturbative approaches and some drawbacks of the latter are pointed out.",0502242v1 2005-03-09,Theoretical Study of Fano Resonance in Single-Walled Carbon Nanotubes,"Electrical transport through single-walled carbon nanotubes (SWNTs) is investigated by using the nearest-neighbor tight-binding model coupled with two electron reservoirs. When the SWNT-electrode coupling is not axially symmetric, asymmetric resonance peaks are found in the conductance and are considered to be due to the interference between two transport channels. These Fano resonances are sensitive to the coupling with electrodes. When the coupling is axially symmetric, no asymmetric resonance peaks are observed.",0503200v1 2005-03-16,Exciton-optical-phonon coupling: comparison with experiments for ZnO quantum wells,"The temperature-dependent linewidths of excitons in ZnO quantum wells were studied by measuring absorption spectra from 5 K to room temperature. We deduced experimentally the exciton-longitudinal-optical (LO) phonon coupling strength, which showed reduction of coupling with decrease in well width. This reduction was explained in terms of confinement-induced enhancement of the excitonic binding energy by comparing the binding energy dependence of calculated coupling strength.",0503386v1 2005-04-22,Rashba interaction in quantum wires with in-plane magnetic fields,"We analyze the spectral and transport properties of ballistic quasi one-dimensional systems in the presence of spin-orbit coupling and in-plane agnetic fields. Our results demonstrate that Rashba precession and intersubband coupling must be treated on equal footing for wavevectors near the magnetic field induced gaps. We find that intersubband coupling limits the occurrence of negative effective masses at the gap edges and modifies the linear conductance curves in the strong coupling limit. The effect of the magnetic field on the spin textured orientation of the wire magnetization is discussed.",0504578v2 2005-05-27,Charge fluctuations in coupled systems: ring coupled to a wire or ring,"Coupled systems in mesoscopic regime are of interest as charge fluctuation between the sub-systems will depend on electron-electron interactions and will play a dominant role in determining their thermodynamic properties. We study some simple systems like a stub or a bubble strongly coupled to a ring. We show that for strong electron-electron interaction, there are some regimes where these charge fluctuations are quenched and charge is individually conserved in the two subsystems. This feature does not depend on choice of parameters or charge distribution.",0505672v2 2005-06-30,Magnon transport and spin current switching through quantum dots,"We study the nonequilibrium spin current through a quantum dot consisting of two localized spin-1/2 coupled to two ferromagnetic insulators. The influence of an intra-dot magnetic field and exchange coupling, different dot-reservoir coupling configurations, and the influence of magnon chemical potential differences vs. magnetic field gradients onto the spin current are examined. We discuss various spin switching mechanisms and find that, in contrast to electronic transport, the spin current is very sensitive to the specific coupling configuration and band edges. In particular, we identify 1- and 2-magnon transport processes which can lead to resonances and antiresonances for the spin current.",0506806v1 2005-07-24,A framework for public-channel cryptography using chaotic lasers,"Two mutually coupled chaotic diode lasers with individual external feedback, are shown to establish chaos synchronization in the low-frequency fluctuations regime. A third laser with identical external feedback but coupled unidirectionally to one of the pair does not synchronize. Both experiments and simulations reveal the existence of a window of parameters for which synchronization by mutual coupling is possible but synchronization by unidirectional coupling is not. This parameter space forms the basis of a proposed public-channel cryptographic scheme and is robust to various possible attacks.",0507554v1 2005-07-29,Quasiclassical frustration,"We study the dissipative properties of a harmonic oscillator subject to two independent heat baths, one of which couples to its position and the other one to its momentum. This model describes a large spin impurity in a ferromagnet. We find that some effects of the two heat baths partially cancel each other. Most notably, oscillations may remain underdamped for arbitrarily strong coupling. This effect is a direct consequence of the mutually conjugate character of position and momentum. For a single dissipative bath coupled linearly to both position and momentum, no underdamped regime is possible for strong coupling. The dynamics of purity loss for one and two wave packets is also investigated.",0507726v1 2005-08-02,Interaction of a surface acoustic wave with a two-dimensional electron gas,"When a surface acoustic wave propagates on the surface of a GaAs semiconductor, coupling between electrons in the two-dimensional electron gas beneath the interface and the elastic host crystal through piezoelectric interaction will attenuate the SAW. The coupling coefficient is calculated for the SAW propagating along an arbitrary direction. It is found that the coupling strength is largely dependent on the propagating direction. When the SAW propagates along the [011] direction, the coupling becomes quite weak.",0508065v1 2005-09-28,About low field memory and negative magnetization in semiconductors and polymers,"Ginzburg-Landau bulk magnetization of itinerant electrons can provide a negative effective field in the Weiss model by coupling to localized magnetic moments. The coupling enforces remnant magnetization, which can be negative or positive depending on the sample magnetic history. Stable magnetic susceptibility of coupled nonequilibrium subsystems with magnetization reversal is always positive. Gauss-scale fields could be expected for switching between negative and positive remnant moments in semiconductors with coupling at ambient temperatures. Negative magnetization in ultra-high conducting polymers is also discussed within the developed framework.",0509712v1 2005-09-30,Parametric coupling for superconducting qubits,"We propose a scheme to couple two superconducting charge or flux qubits biased at their symmetry points with unequal energy splittings. Modulating the coupling constant between two qubits at the sum or difference of their two frequencies allows to bring them into resonance in the rotating frame. Switching on and off the modulation amounts to switching on and off the coupling which can be realized at nanosecond speed. We discuss various physical implementations of this idea, and find that our scheme can lead to rapid operation of a two-qubit gate.",0509799v2 2005-10-03,Electron-vibron coupling in suspended nanotubes,"We consider the electron-vibron coupling in suspended nanotube quantum dots. Modelling the tube as an elastic medium, we study the possible coupling mechanism for exciting the stretching mode in a single-electron-transistor setup. Both the forces due to the longitudinal and the transverse fields are included. The effect of the longitudinal field is found to be too small to be seen in experiment. In contrast, the transverse field which couple to the stretching mode via the bending of the tube can in some cases give sizeable Franck-Condon factors. However, the length dependence is not compatible with recent experiments [Sapmaz et al. cond-mat/0508270].",0510044v1 2005-10-03,Spin relaxation in quantum dots with random spin-orbit coupling,"We investigate the longitudinal spin relaxation arising due to spin-flip transitions accompanied by phonon emission in quantum dots where the strength of the Rashba spin-orbit coupling is a random function of the lateral (in-plane) coordinate on the spatial nanoscale. In this case the Rashba contribution to the spin-orbit coupling cannot be completely removed by applying a uniform external bias across the quantum dot plane. Due to the remnant random contribution, the spin relaxation rate cannot be decreased by more than two orders of magnitude even when the external bias fully compensates the regular part of the spin-orbit coupling.",0510050v1 2005-10-05,Multibranch Bogoliubov-Bloch spectrum of a cigar shaped Bose condensate in an optical lattice,"We study properties of excited states of an array of weakly coupled quasi-two-dimensional Bose condensates by using the hydrodynamic theory. The spectrum of the axial excited states strongly depends on the coupling among the various discrete radial modes in a given symmetry. By including mode-coupling within a given symmetry, the complete excitation spectrum of axial quasiparticles with various discrete radial nodes are presented. A single parameter which determines the strength of the mode coupling is identified. The excitation spectrum in the zero angular momentum sector can be observed by using the Bragg scattering experiments.",0510096v1 2005-12-08,The universality of synchrony: critical behavior in a discrete model of stochastic phase coupled oscillators,"We present the simplest discrete model to date that leads to synchronization of stochastic phase-coupled oscillators. In the mean field limit, the model exhibits a Hopf bifurcation and global oscillatory behavior as coupling crosses a critical value. When coupling between units is strictly local, the model undergoes a continuous phase transition which we characterize numerically using finite-size scaling analysis. In particular, the onset of global synchrony is marked by signatures of the XY universality class, including the appropriate classical exponents $\beta$ and $\nu$, a lower critical dimension $d_{lc} = 2$, and an upper critical dimension $d_{uc}=4$.",0512171v1 2005-12-29,Theory of phonon-induced spin relaxation in laterally coupled quantum dots,"Phonon-induced spin relaxation in coupled lateral quantum dots in the presence of spin-orbit coupling is calculated. The calculation for single dots is consistent with experiment. Spin relaxation in double dots at useful interdot couplings is dominated by spin hot spots that are strongly anisotropic. Spin hot spots are ineffective for a diagonal crystallographic orientation of the dots with a transverse in-plane field. This geometry is proposed for spin-based quantum information processing.",0512713v2 2006-02-14,Collective dynamics in coupled maps on a lattice with quenched disorder,"It is investigated how a spatial quenched disorder modifies the dynamics of coupled map lattices. The disorder is introduced via the presence or absence of coupling terms among lattice sites. Two nonlinear maps have been considered embodying two paradigmatic dynamics. The Miller and Huse map can be associated with an Ising-like dynamics, whereas the logistic coupled maps is a prototype of a non trivial collective dynamics. Various indicators quantifying the overall behavior, demonstrates that even a small amount of spatial disorder is capable to alter the dynamics found for purely ordered cases.",0602338v1 2006-03-09,Generalized coupling in the Kuramoto model,"We propose a modification of the Kuramoto model to account for the effective change in the coupling constant among the oscillators, as suggested by some experiments on Josephson junction, laser arrays and mechanical systems, where the active elements are turned on one by one. The resulting model is analytically tractable and predicts that both first and second order phase transitions are possible, depending upon the value of a new parameter that tunes the coupling among the oscillators. Numerical simulations of the model are in accordance with the analytical estimates, and in qualitative agreement with the behavior of Josephson junctions coupled via a cavity.",0603241v1 2006-03-18,Long-range spin-qubit interaction mediated by microcavity polaritons,"We study the optically-induced coupling between spins mediated by polaritons in a planar micro-cavity. In the strong coupling regime, the vacuum Rabi splitting introduces anisotropies in the spin coupling. Moreover, due to their photon-like mass, polaritons provide an extremely long spin coupling range. This suggests the realization of two-qubit all-optical quantum operations within tens of picoseconds with spins localized as far as hundreds of nanometers apart.",0603472v1 2006-03-23,Intense terahertz laser fields on a quantum dot with Rashba spin-orbit coupling,"We investigate the effects of the intense terahertz laser field and the spin-orbit coupling on single electron spin in a quantum dot. The laser field and the spin-orbit coupling can strongly affect the electron density of states and can excite a magnetic moment. The direction of the magnetic moment depends on the symmetries of the system, and its amplitude can be tuned by the strength and frequency of the laser field as well as the spin-orbit coupling.",0603614v2 2006-03-27,Quantum Hall droplets in coupled lateral quantum dots,"We present a theory and Coulomb and Spin Blockade spectroscopy experiments on quantum Hall droplets with controlled electron numbers (N1,N2) in laterally coupled gated quantum dots. The theory is based on the configuration interaction method (CI) coupled with the unrestricted Hartree-Fock (URHF) basis. It allows us to calculate the magnetic field evolution of ground and excited states of coupled quantum dots with large electron numbers. The method is applied to the spin transitions in the (5,5) droplet. Preliminary experimental results demonstrate the creation of the (5,5) droplet and its Spin Blockade spectra.",0603723v1 2006-05-04,Sparse repulsive coupling enhances synchronization in complex networks,"Through the last years, different strategies to enhance synchronization in complex networks have been proposed. In this Letter, we show that the synchronization in a small-world network of attractively coupled non-identical neurons is strongly improved by adding a tiny fraction of phase-repulsive couplings. By a purely topological analysis that does not depend on the dynamical model, we link the emerging dynamical behavior to the structural properties of the sparsely coupled repulsive network.",0605115v1 2006-05-19,Switchable resonant coupling of flux qubits,"We propose a coupling scheme, where two or more flux qubits with different eigenfrequencies share Josephson junctions with a coupler loop devoid of its own quantum dynamics. Switchable two-qubit coupling is realized by tuning the frequency of the AC magnetic flux through the coupler to a combination frequency of two of the qubits. The coupling allows any or all of the qubits to be simultaneously at the degeneracy point and can change sign.",0605484v3 2006-06-07,An Exact SU(2) Symmetry and Persistent Spin Helix in a Spin-Orbit Coupled System,"Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constant (the ReD model), and for the $[110]$ Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. This symmetry is robust against spin-independent disorder and interactions, and is generated by operators whose wavevector depends on the coupling strength. It renders the spin lifetime infinite at this wavevector, giving rise to a Persistent Spin Helix (PSH). We obtain the spin fluctuation dynamics at, and away, from the symmetry point, and suggest experiments to observe the PSH.",0606196v1 2006-07-22,Exchange interaction and stability diagram of coupled quantum dots in magnetic fields,"The charge stability diagram for two coupled quantum dots containing up to two electrons is computed in magnetic fields. One- and two-particle Schroedinger equations are solved by exact diagonalization to obtain the chemical potentials and exchange energy in these systems. By analyzing the chemical potentials variation with external biases and magnetic fields, it is possible to distinguish between the weak and strong inter-dot couplings. The variation of the chemical potential curvatures and the double-triple point separations in the stability diagrams confirms the inter-dot coupling decrease with increasing magnetic fields. The computed exchange energies are also found to be significantly smaller than the values estimated from the stability diagram.",0607571v1 2006-07-26,Inelastic effects in Aharonov-Bohm molecular interferometer,"Inelastic effects arising from electron-phonon coupling in molecular Aharonov-Bohm (AB) interferometers are studied using the nonequilibrium Green's function method. Results for the magnetoconductance are compared for different values of the electron-phonon coupling strength. At low bias voltages, the coupling to the phonons does not change the lifetime and leads mainly to scattering phase shifts of the conducting electrons. Surprisingly, opposite to the behavior of an electrical gate, the magnetoconductance of the molecular AB interferometer becomes more sensitive to the threading magnetic flux as the electron-phonon coupling is increased.",0607686v1 2006-08-01,Coherent magnetotransport spectroscopy in an edge-blocked double quantum wire with window and resonator coupling,"We propose an electronic double quantum wire system that contains a pair of edge blocking potential and a coupling element in the middle barrier between two ballistic quantum wires. A window and a resonator coupling control between the parallel wires are discussed and compared for the enhancement of the interwire transfer processes in an appropriate magnetic field. We illustrate the results of the analysis by performing computational simulations on the conductance and probability density of electron waves in the window and resonator coupled double wire system.",0608027v1 2006-09-25,Spectroscopy of three strongly coupled flux qubits,"We have carried out spectroscopic measurements of a system of three strongly coupled four-junction flux qubits. The samples studied cover a wide range of parameters with the coupling energy between neighboring qubits varying between 0.75 GHz and 6.05 GHz. The observed complicated spectra agree well with eight-level theory. The experiments are relevant for the realization of a tunable coupling between qubits.",0609627v1 2006-12-19,Effect of spin-orbit coupling on the excitation spectrum of Andreev billiards,"We consider the effect of spin-orbit coupling on the low energy excitation spectrum of an Andreev billiard (a quantum dot weakly coupled to a superconductor), using a dynamical numerical model (the spin Andreev map). Three effects of spin-orbit coupling are obtained in our simulations: In zero magnetic field: (1) the narrowing of the distribution of the excitation gap; (2) the appearance of oscillations in the average density of states. In strong magnetic field: (3) the appearance of a peak in the average density of states at zero energy. All three effects have been predicted by random-matrix theory.",0612501v1 2007-01-20,Stability of longitudinal coupling for Josephson charge qubits,"For inductively coupled superconducting quantum bits, we determine the conditions when the coupling commutes with the single-qubit terms. We show that in certain parameter regimes such longitudinal coupling can be stabilized with respect to variations of the circuit parameters. In addition, we analyze its stability against fluctuations of the control fields.",0701499v2 2007-01-25,Spin-Hall effect and spin-coherent excitations in a strongly confined two-dimensional hole gas,"Based on a rigorous quantum-kinetic approach, spin-charge coupled drift-diffusion equations are derived for a strongly confined two-dimensional hole gas. An electric field leads to a coupling between the spin and charge degrees of freedom. For weak spin-orbit interaction, this coupling gives rise to the intrinsic spin-Hall effect. There exists a threshold value of the spin-orbit coupling constant that separates spin diffusion from ballistic spin transport. In the latter regime, undamped spin-coherent oscillations are observed. This result is confirmed by an exact microscopic approach valid in the ballistic regime.",0701612v1 2007-03-30,Sensitivity of Global Dynamics on the microscopic details of a network of dynamically coupled maps,"Here we analyze the behavior of dynamically coupled maps, based on those introduced in a series of papers by Ito and Kaneko (Phys. Rev. Lett. 88:028701, 2002 and Phys. Rev. E 67:046226, 2003). We show how the microscopic coupling mechanism changes the behavior of the system both by affecting the stability of fixed points and through a more subtle effect in the crossover behavior between different regions of the parameter space. This makes it necessary to choose very carefully the exact manner in which one couples maps if they are to be used as a general model of composite systems.",0703804v1 2005-12-23,Low-Energy Sensor Network Time Synchronization as an Emergent Property,"The primary contribution of this work is to examine the energy efficiency of pulse coupled oscillation for time synchronization in a realistic wireless network environment and to explore the impact of mobility on convergence rate. Energy coupled oscillation is susceptible to interference; this approach uses reception and decoding of short packet bursts to eliminate this problem. The energy efficiency of a commonly used timestamp broadcast algorithm is compared and contrasted with pulse-coupled oscillation. The emergent pulse coupled oscillation technique shows greater energy efficiency as well as robustness with mobility. A proportion of the sensors may be integrated with GPS receivers in order to obtain a master clock time.",0512094v1 1994-10-17,The Dipole Coupling of Atoms and Light in Gravitational Fields,"The dipole coupling term between a system of N particles with total charge zero and the electromagnetic field is derived in the presence of a weak gravitational field. It is shown that the form of the coupling remains the same as in flat space-time if it is written with respect to the proper time of the observer and to the measurable field components. Some remarks concerning the connection between the minimal and the dipole coupling are given.",9410019v1 1996-01-15,New no-scalar-hair theorem for black-holes,"A new no-hair theorem is formulated which rules out a very large class of non-minimally coupled finite scalar dressing of an asymptotically flat, static, and spherically symmetric black-hole. The proof is very simple and based in a covariant method for generating solutions for non-minimally coupled scalar fields starting from the minimally coupled case. Such method generalizes the Bekenstein method for conformal coupling and other recent ones. We also discuss the role of the finiteness assumption for the scalar field.",9601021v1 1998-11-03,On the non-minimal coupling of Riemann-flat Klein-Gordon,"On the non-minimal coupling of Riemann-flat Klein-Gordon Fields to Space-time torsion} The energy spectrum of Klein-Gordon particles is obtained via the non-minimal coupling of Klein-Gordon fields to Cartan torsion in the approximation of Riemann-flatness and constant torsion.When the mass squared is proportional to torsion coupling constant it is shown that the splitting of energy does not occur.I consider that only the vector part of torsion does not vanish and that it is constant.A torsion Hamiltonian operator is constructed.The spectrum of Klein-Gordon fields is continuos.",9811010v1 2001-07-31,A note on wavemap-tensor cosmologies,"We examine theories of gravity which include finitely many coupled scalar fields with arbitrary couplings to the curvature (wavemaps). We show that the most general scalar-tensor $\sigma$-model action is conformally equivalent to general relativity with a minimally coupled wavemap with a particular target metric. Inflation on the source manifold is then shown to occur in a novel way due to the combined effect of arbitrary curvature couplings and wavemap self-interactions. A new interpretation of the conformal equivalence theorem proved for such `wavemap-tensor' theories through brane-bulk dynamics is also discussed.",0107100v1 2002-02-02,"Nonminimal coupling, equivalence principle and exact Foldy-Wouthuysen transformation","It is shown that the exact Foldy-Wouthuysen transformation for spin-0 particles on spacetimes described by the metrics $ds^2 = V^2 dt^2 - W^2 d {\bf{x}}^2$, where $V=V({\bf{x}})$ and $W=W({\bf{x}})$, only exists if the scalar field is nonminimally coupled to the Ricci scalar field with a coupling constant equal to 1/6. The nonminimal coupling term, in turn, does not violate the equivalence principle. As an application we obtain the nonrelativistic Foldy-Wouthuysen Hamiltonian concerning the general solution to the linearized field equations of higher-derivative gravity for a static pointlike source in the Teyssandier gauge.",0202006v1 2002-09-22,Modification of the Doppler Effect due to the Helicity-Rotation Coupling,"The helicity-rotation coupling and its current empirical basis are examined. The modification of the Doppler effect due to the coupling of photon spin with the rotation of the observer is considered in detail in connection with its applications in the Doppler tracking of spacecraft. Further implications of this coupling and the possibility of searching for it in the intensity response of a rotating detector are briefly discussed.",0209079v2 2003-04-01,"Dirac spinor fields in the teleparallel gravity: comment on ""Metric-affine approach to teleparallel gravity""","We show that the coupling of a Dirac spinor field with the gravitational field in the teleparallel equivalent of general relativity is consistent. For an arbitrary SO(3,1) connection there are two possibilities for the coupling of the spinor field with the gravitational field. The problems of consistency raised by Y. N. Obukhov and J. G. Pereira in the paper {\it Metric-affine approach to teleparallel gravity} [gr-qc/0212080] take place only in the framework of one particular coupling. By adopting an alternative coupling the consistency problem disappears.",0304005v1 2003-06-05,Constraints on non-minimally coupled curved space electrodynamics from astrophysical observations,"We study interactions of electro-magnetic fields with the curvature tensor of the form $\lambda R_{\mu \nu \alpha \beta}F^{\mu \nu}F^{\alpha \beta}$. Such coupling terms though are invariant under general coordinate transformation and CPT, however violate the Einstein equivalence principle. These couplings do not cause any energy dependent dispersion of photons but they exhibit birefringence. We put constraints on the coupling constant $\lambda$ using results from solar system radar ranging experiments and millisecond-pulsar observations. We find that the most stringent constraint comes from pulsar observations and is given by $ \lambda < 10^{11} cm^2 $ obtained from the timing of binary pulsar PSR B1534+12.",0306021v1 2004-04-17,Coupled oscillators as models of phantom and scalar field cosmologies,"We study a toy model for phantom cosmology recently introduced in the literature and consisting of two oscillators, one of which carries negative kinetic energy. The results are compared with the exact phase space picture obtained for similar dynamical systems describing, respectively, a massive canonical scalar field conformally coupled to the spacetime curvature, and a conformally coupled massive phantom. Finally, the dynamical system describing exactly a minimally coupled phantom is studied and compared with the toy model.",0404078v1 2004-09-03,Asymptotic quasinormal modes of a coupled scalar field in the Garfinkle-Horowitz-Strominger dilaton spacetime,"The analytic forms of the asymptotic quasinormal frequencies of a coupled scalar field in the Garfinkle-Horowitz-Strominger dilaton spacetime is investigated by using the monodromy technique proposed by Motl and Neitzke. It is found that the asymptotic quasinormal frequencies depend not only on the structure parameters of the background spacetime, but also on the coupling between the scalar fields and gravitational field. Moreover, our results show that only in the minimal couple case, i.e., $\xi$ tends zero, the real parts of the asymptotic quasinormal frequencies agrees with the Hod's conjecture, $T_H\ln{3}$.",0409013v1 2005-03-19,Metric-scalar gravity with torsion and the measurability of the non-minimal coupling,"The ""measurability"" of the non-minimal coupling is discussed by considering the correction to the Newtonian static potential in the semi-classical approach. The coefficient of the ""gravitational Darwin term"" (GDT) gets redefined by the non-minimal torsion-scalar couplings. Based on a similar analysis of the GDT in the effective field theory approach to non-minimal scalar we conclude that for reasonable values of the couplings the correction is very small.",0503084v3 2005-09-02,Nonmetricity and torsion induced by dilaton gravity in two dimension,"We develop a theory in which there are couplings amongst Dirac spinor, dilaton and non-Riemannian gravity and explore the nature of connection-induced dilaton couplings to gravity and Dirac spinor when the theory is reformulated in terms of the Levi-Civita connection. After presenting some exact solutions without spinors, we investigate the minimal spinor couplings to the model and in conclusion we can not find any nontrivial dilaton couplings to spinor.",0509010v3 1999-03-30,Scalar and Tensor Couplings in Kaon Decays,"In the past few years charged kaon experiments have indicated possible scalar and tensor couplings in semileptonic kaon decays(K --> pi e nu). These couplings, if correct, are not predicted by the Standard Model and may indicate the onset of new physics. We present a summary of the existing data and a new, precision measurement of these couplings in the neutral kaon system based on a 3% subset of the data taken by the KTeV (E799) experiment at Fermilab.",9903069v2 1999-10-02,Measurement of Triple-Gauge-Boson Couplings of the W Boson at LEP,"We report on measurements of the triple-gauge-boson couplings of the W boson in e+e- collisions with the L3 detector at LEP. W-pair, single-W and single-photon events are analysed in a data sample corresponding to a total luminosity of 76.7 pb^{-1} collected at centre-of-mass energies between 161 GeV and 183 GeV. CP-conserving as well as both C- and P-conserving triple-gauge-boson couplings are determined. The results, in good agreement with the Standard-Model expectations, confirm the existence of the self coupling among the electroweak gauge bosons and constrain its structure.",9910008v1 2002-01-23,Anomalous couplings at LEP2,"In its second phase, LEP has allowed to study four fermion processes never observed before. Results are presented on the charged triple gauge boson couplings (TGC) from the W-pair, Single W and Single gamma production. The anomalous quartic gauge couplings (QGC) are constrained using production of WWgamma, nunubargammagamma and Zgammagamma final states. Finally, limits on the neutral anomalous gauge couplings (NGC) using the Zgamma and ZZ production processes are also reported. All results are consistent with the Standard Model expectations.",0201035v1 2004-10-05,Measurement of triple gauge boson couplings a an e-gamma collider,"If no light Higgs boson exists, the interaction among the gauge bosons becomes strong at high energies (~1TeV). The effects of strong electroweak symmetry breaking (SEWSB) could manifest themselves indirectly as anomalous couplings before they give rise to new physical states like resonances. Here a study of the measurement of trilinear gauge couplings is presented looking at the hadronic decay channel of the W boson at an e-gamma - collider. A sensitivity in the range of 10^{-3} to 10^{-4} can be reached depending on the coupling under consideration.",0410011v2 2005-06-22,Boson Gauge Couplings at LEP,"The review of the measurements of the gauge couplings in the boson sector at LEP is presented. The measurements of the charged triple gauge couplings (cTGC) parameters from the four LEP experiments are combined and the results are in good agreement with the Standard Model predictions, proving the non-abelian structure of the SU(2)_L x U(1)_Y gauge simmetry. Different measurements of these parameters are reviewed and all possible fit methods discussed. The current limits on the anomalous neutral triple gauge couplings (nTGC) and the quartic gauge coplings (QGC) are also presented.",0506048v1 2005-07-11,Trilinear Gauge Couplings from gamma/gamma to WW,"If there is no the Standard Model Higgs boson, the interaction among the gauge bosons becomes strong at high energies (~ 1TeV). The effects of strong electroweak symmetry breaking could manifest themselves indirectly through the vertices as anomalous gauge boson couplings before they give rise to new physical states like resonances. Here a study of the measurement of trilinear gauge couplings kappa_gamma and lambda_gamma is presented looking at the hadronic decay channel of the WW boson pair at an gamma/gamma-collider. A sensitivity of order of 0.001-0.0001 can be reached depending on the coupling under consideration and on the initial polarisation state.",0507050v1 1992-06-01,Renormalization group and triviality in noncompact lattice QED with light fermions,"In the framework of noncompact lattice QED with light fermions, we derive the functional dependence of the average energy per plaquette on the bare parameters using block-spin Renormalization Group arguments and assuming that the renormalized coupling vanishes. Our numerical results for this quantity in $8^4$ and $10^4$ lattices show evidence for triviality in the weak coupling phase and point to a non vanishing value for the renormalized coupling constant in the strong coupling phase.",9205030v1 1992-07-18,Fermion Interactions in the Wilson Yukawa Approach for Lattice Chiral Gauge Theories,"We consider fermion-gauge couplings in the Wilson-Yukawa approach for lattice chiral gauge theories. At the leading order of a fermionic hopping parameter expansion we find that the fermion-gauge coupling has a chiral and tree-like structure. We argue that this fermion-gauge coupling remains non-zero in the continuum limit taken in the Higgs phase. Possible fermion-scalar couplings in this approach are considered. We also evaluate the fermion interaction with an external gauge field in the slightly modified model and show that it has a chiral structure in general.",9207018v1 1992-11-26,No strong coupling regime in the fermion-Higgs sector of the standard model,"We present results for the renormalized quartic self-coupling $\lm_R$ and the renormalized Yukawa coupling $y_R$ in a fermion-Higgs model with two SU(2) doublets, indicating that these couplings are not very strong.",9211061v1 1993-09-13,A Precise Determination of the Running Coupling in the SU(3) Yang-Mills Theory,"A non-perturbative finite-size scaling technique is used to study the evolution of the running coupling (in a certain adapted scheme) in the SU(3) Yang-Mills theory. At low energies contact is made with the fundamental dynamical scales, such as the string tension K, while at larger energies the coupling is shown to evolve according to perturbation theory. In that regime the coupling in the MS-bar scheme of dimensional regularization is obtained with an estimated total error of a few percent.",9309005v1 1994-11-15,Do Wilson Fermions Induce an Adjoint Gauge Coupling?,"Expansions of the Wilson determinant in lattice QCD with quarks produce gauge action terms which shift the coupling constant of the fundamental representation plaquette action and induce an adjoint representation plaquette action. We study the magnitude of these induced couplings with two flavors of Wilson fermions. We utilize a microcanonical demon method, which allows us to measure the induced couplings directly from gauge configurations generated by full fermionic simulations.",9411025v1 1994-11-30,The SU(3) running coupling from lattice gluons,"We provide numerical results for the running coupling in $SU(3)$ Yang-Mills theory as determined from an analysis of lattice two and three-point gluon correlation functions. The coupling is evaluated directly, from first principles, by defining suitable renormalisation constants from the lattice triple gluon vertex and gluon propagator. For momenta larger than 2 GeV, the coupling is found to run according to the 2-loop asymptotic formula. The influence of lattice artifacts on the results appears negligible within the precision of our measurements, although further work on this point is in progress.",9411085v1 1994-12-16,Numerical Simulations of an SU(2)_L x SU(2)_R-symmetric Higgs-Yukawa Model on the QUADRICS Q16,"We report on our work on the SU(2)_L x SU(2)_R symmetric Higgs Yukawa Model with mirror fermion action. Our model describes a fermion Higgs system in the limit of vanishing gauge coupling. Setting the bare Yukawa coupling of the mirror fermions G_\chi to zero, we want to determine the triviality bounds on the renormalized Yukawa coupling of the fermions G_{R\psi} and the scalar self-coupling g_R on 8^3x16 and 16^3x32 lattices.",9412082v1 1994-12-24,Strong coupling analysis of the large-N 2-d lattice chiral models,"Two dimensional large-N chiral models on the square and honeycomb lattices are investigated by a strong coupling analysis. Strong coupling expansion turns out to be predictive for the evaluation of continuum physical quantities, to the point of showing asymptotic scaling. Indeed in the strong coupling region a quite large range of beta values exists where the fundamental mass agrees, within about 5% on the square lattice and about 10% on the honeycomb lattice, with the continuum predictions in the %%energy scheme.",9412101v1 1995-02-01,Two-loop relation between the bare lattice coupling and the MSbar coupling in pure SU(N) gauge theories,"We report the result of a computation of the relation between the renormalized coupling in the MSbar scheme of dimensional regularization and the bare coupling in the standard lattice formulation of the SU(N) Yang-Mills theory to two-loop order of perturbation theory and discuss some of its implications.",9502001v1 1995-05-12,Computation of the relation between the bare lattice coupling and the MSbar coupling in SU(N) gauge theories to two loops,"The perturbation expansion of the MSbar coupling in the SU(N) gauge theory in powers of the bare lattice coupling is extended to two-loop order. A discussion of our results has already been published elsewhere. We here describe the calculation in some detail. It relies on the background field technique and a recently introduced coordinate space method to evaluate lattice Feynman integrals.",9505011v1 1995-11-21,Singular Vertices in the Strong Coupling Phase of Four--Dimensional Simplicial Gravity,"We study four--dimensional simplicial gravity through numerical simulation with special attention to the existence of singular vertices, in the strong coupling phase, that are shared by abnormally large numbers of four--simplices. The second order phase transition from the strong coupling phase into the weak coupling phase could be understood as the disappearance of the singular vertices. We also change the topology of the universe from the sphere to the torus.",9511023v1 1996-05-28,Phase diagram of Regge quantum gravity coupled to SU(2) gauge theory,"We analyze Regge quantum gravity coupled to SU(2) gauge theory on $4^3\times 2$, $6^{3}\times 4$ and $8^{3}\times 4$ simplicial lattices. It turns out that the window of the well-defined phase of the gravity sector where geometrical expectation values are stable extends to negative gravitational couplings as well as to gauge couplings across the deconfinement phase transition. We study the string tension from Polyakov loops, compare with the $\beta$-function of pure gauge theory and conclude that a physical limit through scaling is possible.",9605036v1 1997-10-10,Two loop expansion of the Schroedinger functional coupling alpha_SF in SU(3) lattice gauge theory,"The two loop coefficient of the expansion of the Schroedinger functional coupling in terms of the lattice coupling is calculated for the SU(3) Yang-Mills theory. This coefficient is required to relate lattice data to the MS-bar-coupling. As a byproduct of the calculation, the Schroedinger functional is improved to two loop order and the three loop coefficient of the beta function in the SF-scheme is derived.",9710043v1 1999-12-14,Hamiltonian domain wall fermions at strong coupling,"We apply strong-coupling perturbation theory to gauge theories containing domain-wall fermions in Shamir's surface version. We construct the effective Hamiltonian for the color-singlet degrees of freedom that constitute the low-lying spectrum at strong coupling. We show that the effective theory is identical to that derived from naive, doubled fermions with a mass term, and hence that domain-wall fermions at strong coupling suffer both doubling and explicit breaking of chiral symmetry. Since we employ a continuous fifth dimension whose extent tends to infinity, our result applies to overlap fermions as well.",9912019v2 2000-05-01,Center Vortices at Strong Couplings and All Couplings,"Motivations for the center vortex theory of confinement are discussed. In particular, it is noted that the abelian dual Meissner effect, which is the signature of dual superconductivity, cannot adequately describe the confining force at large distance scales. A long-range effective action is derived from strong-coupling lattice gauge theory in D=3 dimensions, and it is shown that center vortices emerge as the stable saddlepoints of this action. Thus, in the case of strong couplings, the vortex picture is arrived at analytically. I also respond briefly to a recent criticism regarding maximal center gauge.",0005001v1 2000-12-28,Phase Structure of the 5D Abelian Higgs Model with Anisotropic Couplings,"We establish the phase diagram of the five-dimensional anisotropic Abelian Higgs model by mean field techniques and Monte Carlo simulations. The anisotropy is encoded in the gauge couplings as well as in the Higgs couplings. In addition to the usual bulk phases (confining, Coulomb and Higgs) we find four-dimensional ``layered'' phases (3-branes) at weak gauge coupling, where the layers may be in either the Coulomb or the Higgs phase, while the transverse directions are confining.",0012028v1 2001-10-11,Investigation of gauge-fixed pure U(1) theory at strong coupling,"We numerically investigate the phase diagram of pure U(1) gauge theory with gauge fixing at strong gauge coupling. The FM-FMD phase transition, which proved useful in defining Abelian lattice chiral gauge theory, persists also at strong gauge coupling. However, there the transition seems no to be longer continuous. At large gauge couplings we find evidences for confinement.",0110043v1 2004-09-23,Domain-Wall Fermions at Strong Coupling,"The DWF formulation becomes increasingly problematic at gauge couplings for which $a^{-1}<2$ GeV, where the roughness of the gauge field leads to increased explicit chiral symmetry breaking ($\mres$). This problem becomes especially severe for sufficiently strong coupling where the underlying 4-dimensional Wilson theory is in the Aoki phase. We review our attempts to find a suitable modification of the gauge and/or the fermion action which would allow the DWF method to work reliably at stronger coupling.",0409143v1 2005-02-23,Running coupling of 2-flavor QCD at zero and finite temperature,"We present lattice studies of the running coupling in 2-flavor QCD. The coupling at zero temperature (T=0) is extracted from Wilson loops while the coupling at finite temperature ($T\neq0$) is determined from Polyakov loop correlation functions.",0502012v2 2005-12-19,The behavior of the sextic coupling for the scalar field at the intermediate and strong coupling regime,"We study the behavior of the renormalized sextic coupling at the intermediate and strong coupling regime for the $\phi^4 $ theory defined in $d=2$-dimension. We found a good agreement with the results obtained by the field-theoretical renormalization-group in the Ising limit. In this work we use the lattice regularization method.",0512024v1 2006-08-21,The spectrum of lattice QCD with staggered fermions at strong coupling,"Using 4 flavors of staggered fermions at infinite gauge coupling, we compare various analytic results for the hadron spectrum with exact Monte Carlo simulations. Agreement with Ref. \cite{Martin_etal} is very good, at the level of a few percent. Our results give credence to a discrepancy between the baryon mass and the critical chemical potential, for which baryons fill the lattice at zero temperature and infinite gauge coupling. Independent determinations of the latter set it at about 30% less than the baryon mass. One possible explanation is that the nuclear attraction becomes strong at infinite gauge coupling.",0608012v1 1992-09-21,CP Violating Form Factors for Three Gauge Boson Vertex in the Two Higgs Doublet and Left-Right symmetric Models,"In this paper we calculate the one loop contributions to the CP violating three gauge boson couplings in two-Higgs doublet and Left--Right symmetric models. In the two-Higgs doublet model only a P conserving and CP violating coupling is generated, and it can be large as $10^{-3}$. In the Left--Right symmetric model both P conserving and violating couplings are generated. Due to constraints on the $W_L$--$W_R$ mixing, these couplings are small.",9209260v1 1993-02-24,"Masses, Mixings, Yukawa Couplings and their Symmetries","We present a method to find the number of real and imaginary observable parameters coming from the Yukawa sector in an arbitrary gauge theory. The method leads naturally to a classification of Yukawa couplings according to their symmetries and suggests a new parametrization of masses and mixings that is useful to study the behaviour of Yukawa couplings under the renormalization group. We apply it to some examples based on the Standard Model with Yukawa couplings obeying various chiral symmetries. We also show how our method of parameter counting can be used in some models with an enlarged leptonic sector.",9302301v1 1993-06-10,Anomalous $WWZ$ couplings and $K_L\rightarrow μ^+ μ^-$,"We study contributions to $K_L \rightarrow \mu^+\mu^-$ from anomalous $WWZ$ interactions. There are, in general, seven anomalous couplings. Among the seven anomalous couplings, only two of them contribute significantly. The others are suppressed by factors like $m_s^2/M_W^2$, $m_d^2$, or $m_K^2/M_W^2$. Using the experimental data on $K_L\rightarrow \mu^+\mu^-$, we obtain strong bounds on the two anomalous couplings.",9306254v3 1994-05-12,Probing the Couplings of the Top Quark to Gauge Bosons,"We parameterize the non-universal couplings of t-t-Z and t-b-W in the electroweak chiral lagrangian approach, and examine the constraints on these parameters from the LEP data. We also study how the SLC, Tevatron, LHC and NLC can improve the measurement of these couplings. Different symmetry breaking scenarios imply different correlations among these couplings, whose measurement will then provide a means to probe the electroweak symmetry breaking sector.",9405277v1 1994-05-21,Anomalous Vector-Boson Couplings in Majorana Neutrino Models,"We examine the contributions of Majorana neutrinos to CP-violating WWZ and ZZZ self-couplings, using a model in which sterile neutrinos couple to the W and Z by mixing with a fourth-generation heavy lepton. We find that the induced form factors can be as large as 0.5%. The model satisfies all phenomenological bounds in a natural way, including those due to the strong limits on the neutron and electron electric dipole moments. Anomalous CP-odd couplings of this size are unlikely to be observed at LEP200, but might be detectable at NLC.",9405349v1 1994-10-25,Bounds on Anomalous Gauge Boson Couplings From Partial Z Widths at LEP,"We place bounds on anomalous gauge boson couplings from LEP data with particular emphasis on those couplings which do not contribute to $Z$ decays at tree level. We use an effective field theory formalism to compute the one-loop corrections to the $Z\rightarrow {\overline f} f$ decay widths resulting from non-standard model three and four gauge boson vertices. We find that the precise measurements at LEP constrain the three gauge boson couplings at a level comparable to that obtainable at LEPII and LHC.",9410364v1 1994-12-09,CP Violation and the Width $Z\rightarrow b\bar{b}$,"We discuss the effect of CP-violating $Zb\bar{b}$, $Zb\bar{b}G$ and $Zb\bar{b}\gamma$ couplings on the width $\Gamma(Z\rightarrow b\bar bX)$. The presence of such couplings leads in a natural way to an increase of this width relative to the prediction of the standard model. Various strategies of a direct search for such CP-violating couplings by using CP-odd observables are outlined. The number of $Z$ bosons required to obtain significant information on the couplings in this way is well within the reach of present LEP experiments.",9412268v1 1995-02-16,Constraining the Strongly-Coupled Standard Model Including a W' Isotriplet,"We consider the Strongly-Coupled Standard Model (Abbott-Farhi model) including an isotriplet of W' vector bosons. First we calculate the corrections to the low-energy theory, which can be effectively summarized in terms of the parameters S, T and U. Then we use high- precision electroweak measurements to constrain the mass and couplings of the W'. The W' couplings are restricted to be unnaturally small, and we conclude that this model is no longer compelling as a theory of the electroweak interactions.",9502331v1 1995-06-12,Axion-photon Couplings in Invisible Axion Models,"We reexamine the axion-photon couplings in various invisible axion models motivated by the recent proposal of using optical interferometry at the ASST facility in the SSCL to search for axion. We illustrate that the assignment of $U(1)_{PQ}$ charges for the fermion fields plays an important role in determining the couplings. Several simple non-minimal invisible axion models with suppressed and enhanced axion-photon couplings are constructed, respectively. We also discuss the implications of possible new experiments to detect solar axions by conversion to $X$-rays in a static magnetic apparatus tracking the sun.",9506295v1 1995-06-16,Chiral symmetry breaking in strongly coupled scalar QED,"Scalar QED with fermions is investigated in an expansion in powers of the inverse gauge coupling constant. The fermion mass generation is studied in next to leading order of the strong coupling expansion for the Higgs-phase of the model. Chiral symmetry breaking is discussed. Our approach supports from a strong coupling point of view the results obtained earlier by Miransky, Bardeen and Kondo.",9506341v1 1995-10-17,New Bounds on R-Parity Violating Couplings,"Bounds on R-parity violating couplings in the supersymmetric standard model are reviewed, and some new bounds arising from non-observation of certain rare B-decays (such as $B \rightarrow K^+K^-$) are presented. The focus is on baryon-number violating couplings, but it is also noted that many products of lepton- number violating and baryon-number violating couplings are not significantly constrained by proton decay bounds. The talk reviewed the work in a recent paper by Carlson, Roy and Sher (Phys. Letters, in press).",9510320v1 1996-01-11,Dynamical Gauge Coupling Constants,"In string theory the coupling parameters are functions of moduli fields. The actual values of the coupling constants are then dynamically determined through the vacuum expextation values of these fields. We review the attempts to connect such theories to low energy effective field theories with realistic gauge coupling constants. This includes a discussion of supersymmetry breakdown, the question of a running dilaton, string threshold calculations and the possibility of string unification.",9601241v1 1996-07-07,Relativistic Coulomb Problem: Energy Levels at the Critical Coupling Constant Analytically,"The Hamiltonian of the spinless relativistic Coulomb problem combines the standard Coulomb interaction potential with the square-root operator of relativistic kinematics. This Hamiltonian is known to be bounded from below up to some well-defined critical coupling constant. At this critical coupling constant, however, the differences between all analytically obtainable upper bounds on the corresponding energy eigenvalues and their numerically determined (approximate) values take their maxima. In view of this, an analytical derivation of (not so bad) upper bounds on the lowest-lying energy levels at the critical coupling constant is presented.",9607249v1 1996-11-26,CP violating couplings in Z -> 3 jet decays revisited,"Possible CP violating effects in $Z\rightarrow$ 3 jet decays are investigated. The analysis assumes the presence of CP violating $Zq\bar qG$ couplings. The contribution of these couplings to the $Z\rightarrow q\bar qG$ decay width is calculated for different cut algorithms, including nonzero quark masses. Various CP--odd observables are discussed and it is shown that their sensitivity can change significantly if one uses normalized or unnormalized momentum vectors for their construction. Optimal observables are proposed which allow to measure the new couplings simultaneously.",9611430v1 1997-01-31,An extension of the standard model with a single coupling parameter,"We show that it is possible to find an extension of the matter content of the standard model with a unification of gauge and Yukawa couplings reproducing their known values. The perturbative renormalizability of the model with a single coupling and the requirement to accomodate the known properties of the standard model fix the masses and couplings of the additional particles. The implications on the parameters of the standard model are discussed.",9702204v1 1997-08-22,Negative coupling instability and grandunified baryogenesis,"I review my recent work with Brian Greene and Thomas Roos. First I discuss the effect of a negative cross-coupling on the inflaton decay in two scalar field theories. Our main finding is a new effect, the negative coupling instability, which leads to explosive particle production and very fast inflaton decay. Then I discuss the consequences of this instability for grandunified baryogenesis models. The novel aspect of this review is an intuitive explanation of the negative coupling instability, using field trajectories in the configuration space.",9708428v1 1997-10-01,Model independent analysis of the trilinear gauge boson couplings at LC: role of polarized cross sections,"By means of a model-independent analysis, we discuss the constraints on anomalous trilinear gauge-boson couplings that can be obtained from the study of electron-positron annihilation into $W$ pairs at LC with \sqrt{s}=0.5 TeV and 1 TeV. We consider the general CP conserving anomalous effective Lagrangian, as well as some specific models with reduced number of independent couplings. The analysis is based on combinations of observables with initial and final state polarizations, that allow to separately constrain the different couplings and to improve the corresponding numerical bounds.",9710215v1 1997-11-02,Excited Baryons Phenomenology from Large-$N_c$ QCD,"We present a phenomenological analysis of the strong couplings of the negative-parity L=1 baryons from the perspective of the large-$N_c$ expansion. In the large-$N_c$ limit the mass spectrum and mixing pattern of these states are constrained in a very specific way. The mixing angles are completely determined in this limit, with predictions in good agreement with experiment. In the combined large-$N_c$ and SU(3) limits the pion couplings of the five negative-parity octets to the ground state baryons are given in terms of only 3 independent couplings. The large-$N_c$ predictions for the ratios of strong couplings are tested against experimental data.",9711201v1 1998-01-20,Indications for an Anomalous Right-Handed Coupling of the b-Quark from a Model Independent Analysis of LEP and SLD Data on Z-Decays,"A model independent analysis is made using the LEP and SLD data on Z decays available at the end of 1996. The effective weak coupling constants of leptons, c quarks and b quarks are extracted. Except for the right-handed b quark coupling, they all agree well with the predictions of the Standard Electroweak Model for $m_t = 172$ GeV and $m_H = 263$ GeV. The right-handed b quark coupling is found to be 42% and 3.2 standard deviations above the Standard Model prediction.",9801355v2 1998-06-03,Flavour symmetry of mesonic decay couplings,"We present flavour-symmetric results for the couplings of quark-antiquark systems to meson-meson channels in the harmonic-oscillator expansion. We tabulate their values for all possible open and closed decay channels of pseudo-scalar, vector and scalar mesons. We compare the predictions of a model that employs these flavour-symmetric couplings, both with the results of a model which uses explicitly flavour-dependent couplings, and with experiment.",9806248v3 1998-10-13,Violation of SUSY equivalence in triple gauge boson and gaugino couplings,"Supersymmetry implies that the trilinear couplings between gauge bosons and gauginos are equal to all orders in perturbation theory. However if SUSY is broken and some of the superpartners have large SUSY breaking masses then they can induce non-decoupling deviations in this relation through radiative corrections. In this article we show that the deviation in the ratio of triple gauge to gaugino couplings from unity can be around 2.3% (3.3%) in heavy QCD models (2-1 models). Precision measurements of triple gaugino couplings at furture high energy colliders can therefore probe such violations and the existence of heavy superparticles in the multi Tev region which would otherwise be inaccessible.",9810344v1 1998-11-19,Quark Gluon Plasma as a Strongly Coupled Color-Coulombic Plasma,"We show that the extensively studied equation of state (EOS) of strongly coupled QED plasma fits the recent lattice EOS data of gluon plasma remarkably well, with appropriate modifications to take account of color degrees of freedom and running coupling constant. Hence we conclude that the quark gluon plasma near the critical temperature is a strongly coupled color-Coulombic plasma.",9811397v1 1999-01-10,Pionic coupling constants of heavy mesons in the quark model,"We analyse pionic couplings of heavy mesons combining PCAC with the dispersion quark model to calculate the relevant transition form factors. Ground states and radial excitations are considered. For the ground state coupling constants the values $\hat g=0.5\pm0.02$ in the heavy quark limit, $g_{B^*B\pi}=40\pm 3$, $g_{D^*D\pi}=16\pm 2$ are obtained. A sizeable suppression of the coupling constants describing the pionic decays of the radial excitations is observed.",9901261v1 1999-01-19,CP Violation in Decays Z --> 4 Jets,"We analyse CP-violating effects in Z \to 4 jet decays, assuming the presence of CP-violating effective $Z b \bar{b} G$ and $Z b \bar{b} G G$ couplings. We discuss the influence of these couplings on the decay width. Furthermore, we propose various strategies of a direct search for such CP-violating couplings by using different CP-odd observables. The present data of LEP 1 should give significant information on the couplings.",9901343v2 1999-02-05,Measurements of electroweak couplings of the tau lepton at L3,"We review the current knowledge of the couplings of the tau lepton to the electroweak gauge bosons, the W, Z and photon, obtained from the full L3 data sample at center-of-mass energies near the Z mass. Measurements of the the effective vector and axial-vector weak neutral couplings of the $\tau$, the Lorentz structure of the weak charged current, and anomalous couplings of the electroweak gauge bosons to the tau are presented.",9902253v1 1999-02-16,Spin Effects in Diffractive $J/Ψ$ Leptoproduction and Structure of Pomeron Coupling,"We calculate the cross section and the $A_{ll}$ asymmetry of the diffractive vector meson leptoproduction for a simple model of the pomeron coupling with the proton. It is found that the sensitivity of the spin--dependent cross section of the diffractive $J/\Psi$ production to the pomeron coupling structure is rather weak. The conclusion is made that it will be difficult to study the structure of the pomeron coupling with the proton in future polarized diffractive experiments on the $J/\Psi$ production.",9902356v2 1999-08-31,A new approach to axial coupling constants in the QCD sum rule,"We derive new QCD sum rules for the axial coupling constants by considering two-point correlation functions of the axial-vector currents in a one nucleon state. The QCD sum rules tell us that the axial coupling constants are expressed by nucleon matrix elements of quark and gluon operators which are related to the sigma terms and the moments of parton distribution functions. The results for the iso-vector axial coupling constants and the 8th component of the SU(3) octet are in good agreement with experiment.",9908512v1 1999-09-28,The CP-violating triple gluon interaction in Z -> 4 jets,"We analyse CP-violating effects in Z -> 4 jet decays, assuming the presence of a CP-violating effective triple gluon coupling. We discuss the influence of this coupling on the decay width. Furthermore, we analyse different CP-odd observables and propose strategies of a direct search for such a CP-violating GGG coupling. The present data of LEP 1 should give significant information on the coupling.",9909527v1 2000-02-14,Anomalous quartic couplings in six-fermion processes at the Linear Collider,"The dimension-four genuine anomalous quartic couplings are studied in processes of six-fermion production via e+e- collisions. Complete tree-level electroweak calculations are performed including initial-state-radiation and beamstrahlung. The analysis of final-state distributions can be used to find kinematical cuts to enhance the effects of anomalous couplings. For the parameters of the custodial-symmetry-conserving anomalous couplings a sensitivity in the range between 10^{-3} and 10^{-2} can be expected at 1 TeV.",0002142v1 2000-03-07,Critical couplings for chiral symmetry breaking via instantons,"Using an instanton effective action formalism, we compute the critical coupling for the nonperturbative formation of a dynamical mass via instantons in non-Abelian gauge theories with N_f massless fermions. Only continuous phase transitions are considered. For large values of N_f the critical couplings are found to be much smaller than the equivalent critical couplings obtained from gauge exchange calculations in the ladder approximation.",0003059v2 2000-11-03,Solving the BFKL Equation with Running Coupling,"We describe a formalism for solving the BFKL equation with a coupling that runs for momenta above a certain infrared cutoff. By suitably choosing matching conditions proper account is taken of the fact that the BFKL diffusion implies that the solution in the infrared (fixed coupling) regime depends upon the solution in the ultraviolet (running coupling) regime and vice versa. Expanding the BFKL kernel to a given order in the ratio of the transverse momenta allows arbitrary accuracy to be achieved.",0011047v2 2000-11-21,CP-violating ZZh Coupling at e+e- Linear Colliders,"We study the general Higgs-weak boson coupling with CP-violation via the process e+e- -> f \bar f h. We categorize the signal channels by sub-processes Zh production and ZZ fusion and construct four CP asymmetries by exploiting polarized e+e- beams. We find complementarity among the sub-processes and the asymmetries to probe the real and imaginary parts of the CP-violating form factor. Certain asymmetries with unpolarized beams can retain significant sensitivity to the coupling. We conclude that at a linear collider with high luminosity, the CP-odd ZZh coupling may be sensitively probed via measurements of the asymmetries.",0011271v1 2000-12-29,Brane Couplings from Bulk Loops,"We compute loop corrections to the effective action of a field theory on a five-dimensional $S_1/Z_2$ orbifold. We find that the quantum loop effects of interactions in the bulk produce infinite contributions that require renormalization by four-dimensional couplings on the orbifold fixed planes. Thus bulk couplings give rise to renormalization group running of brane couplings.",0012379v2 2001-01-23,Testing Higgs Self-Couplings at High-Energy Linear Colliders,"In order to verify the Higgs mechanism experimentally, the Higgs self-couplings have to be probed. These couplings allow the reconstruction of the characteristic Higgs potential responsible for the electroweak symmetry breaking. The couplings are accessible in a variety of multiple Higgs production processes. The theoretical analysis including the most relevant channels for the production of neutral Higgs boson pairs at high-energy and high-luminosity $e^+e^-$ linear colliders will be presented in this note.",0101262v1 2001-04-09,Treatment of the QCD coupling in high energy processes,"The treatment of the running QCD coupling in evolution equations is discussed. It is shown that the use of the virtuality of ladder (vertical) partons as the scale for QCD coupling in every rung of ladder graphs is an approximation that holds for DIS at large x only. On the contrary, in the small x region the coupling depends on the virtuality of s -channel (horizontal) gluons. This observation leads to different results for the Regge-like processes and DIS structure functions at small x.",0104082v2 2001-05-02,Light Higgs bosons from a strongly interacting Higgs sector,"The mass and the decay width of a Higgs boson in the minimal standard model are evaluated by a variational method in the limit of strong self-coupling interaction. The non-perturbative technique provides an interpolation scheme between strong-coupling regime and weak-coupling limit where the standard perturbative results are recovered. In the strong-coupling limit the physical mass and the decay width of the Higgs boson are found to be very small as a consequence of mass renormalization. Thus it is argued that the eventual detection of a light Higgs boson would not rule out the existence of a strongly interacting Higgs sector.",0105018v1 2001-06-30,Critical couplings in Crystalline Color superconductivity,"Solving the Schwinger-Dyson equations, we analyze the pairing of quarks in asymmetric quark matter where quarks have different chemical potentials. We show that in the asymmetric quark matter a crystalline color-superconducting gap opens when the quark coupling is stronger than a critical value. The critical coupling is nonzero, since the infrared divergence is lessened when the momenta of pairing quarks are not opposite. The superconducting gaps and the critical couplings are calculated both at high and intermediate densities.",0107003v1 2001-07-04,Yukawa Hierarchy Transfer from Superconformal Sector and Degenerate Sfermion Masses,"We propose a new type of supersymmetric models coupled to superconformal field theories (SCFT's), leading simultaneously to hierarchical Yukawa couplings and completely degenerate sfermion masses. We consider models with an extra Abelian gauge symmetry to generate hierarchical structure for couplings between the SM sector and the SC sector. Interestingly, this hierarchy is inversely transferred to the Yukawa couplings in the SM sector. In this type of models, flavor-independent structure of the superconformal fixed point guarantees that the sfermion masses of the first and the second generations are completely degenerate at low energy.",0107030v2 2001-11-23,Determination of the muon Yukawa coupling at high energy e+e- linear colliders,"The perspectives for the observation of the rare decay H -> mumu decay and the determination of the muon Yukawa coupling at a TeV-class and at a multi-TeV e+e- linear colliders are discussed. The signal for the decay can be obtained at 0.8 TeV and a first estimate of the coupling derived. A linear collider operating at 3 TeV, with high luminosity, is able to improve the accuracy on this couplings to 4% to 11% for 120 GeV < M_H < 150 GeV.",0111307v1 2002-05-13,The Infrared Behaviour of the Running Coupling in Landau Gauge QCD,"Approximate solutions for the gluon and ghost propagators as well as the running coupling in Landau gauge Yang-Mills theories are presented. These propagators obtained from the corresponding Dyson-Schwinger equations are in remarkable agreement with those of recent lattice calculations. The resulting running coupling possesses an infrared fixed point, $\alpha_S(0) = 8.92/N_c$ for all gauge groups SU($N_c$). Above one GeV the running coupling rapidly approaches its perturbative form.",0205125v1 2002-05-15,The Energy Dependence of the Saturation Momentum,"We study BFKL evolution and, in particular, the energy dependence of the saturation momentum in the presence of saturation boundaries limiting the region of linear BFKL evolution. In the case of fixed coupling evolution we confirm the previously found exponential term in $Q_s(Y)$ and determine the prefactor $Y$ and $\alpha$ dependences. In the running coupling case we find $Y^{1/6}$ corrections to the $Y^{1/2}$exponential behavior previously known. Geometrical scaling of the scattering amplitude is valid in a wide-range of momenta for fixed coupling evolution and in a more restricted region for running coupling evolution.",0205167v1 2002-05-21,Radion Couplings to Bulk Fields in the Randall-Sundrum Model,"The radion may be the lightest new state present in the Randall-Sundrum(RS) model. We examine the couplings of the radion to the Standard Model(SM) fields in the scenario where they propagate in the bulk and expand into Kaluza-Klein towers. These couplings are then contrasted with those of the more familiar case where the SM fields are confined to the TeV brane. We find that the couplings of the radion to both $gg$ and $\gamma\gamma$ can be significantly different in these two cases. Implications for radion collider phenomenology are discussed.",0205242v1 2002-08-08,On the QCD coupling behavior in the infrared region,"The summary of nonperturbative results for the QCD invariant coupling bar{alpha}_s obtained by lattice simulations for functional integral and by solution of approximate Dyson--Schwinger equations reveals a puzzling variety of IR behavior of bar{alpha}_s(Q^2) even on a qualitative level. This, in turn, rises a question of correspondence between the results obtained so far by different groups. We analyze this issue in terms of mass-dependent coupling constant transformations and conclude that the question of the IR behavior of effective QCD coupling and of propagators is not a well--defined one and needs to be more specified.",0208082v1 2002-11-06,Quartic Gauge Boson Couplings and Tree Unitarity in the SU(3)_C X SU(3)_L X U(1)_N Models,"The quartic gauge boson couplings in the ${SU(3)}_C \otimes {SU(3)}_L \otimes {U(1)}_N$ models are presented. We find that the couplings of four {\it differrent} gauge bosons may have unusual Lorentz structure and the couplings sastify the tree unitarity requirement at high energy limit.",0211072v1 2002-11-26,Grand Unification and Time Variation of the Gauge Couplings,"Astrophysical indications that the fine structure constant is time dependent are discussed in the framework of grand unification models. A variation of the electromagnetic coupling constant could either be generated by a corresponding time variation of the unified coupling constant or by a time variation of the unification scale, or by both. The case in which the time variation of the electromagnetic coupling constant is caused by a time variation of the unification scale is of special interest. It is supported in addition by recent hints towards a time change of the proton-electron mass ratio. Possible implications for baryogenesis are discussed.",0211421v1 2003-02-28,J/psi couplings to charmed resonances and to pi,"We present an evaluation of the strong couplings JD^(*)D^(*) and JD^(*)D^(*)pi by an effective field theory of quarks and mesons. These couplings are necessary to calculate pi+J/psi --> D^(*)+barD^(*) cross sections, an important background to the J/psi suppression signal in the quark-gluon plasma. We write down the general effective lagrangian and compute the relevant couplings in the soft pion limit and beyond.",0302273v3 2003-06-17,Vector Boson Fusion and Quartic Boson Couplings,"One of the goals of the upcoming experiments at the LHC is the exploration of electroweak symmetry breaking in all aspects. In particular, the self-couplings of the vector gauge bosons are completely specified in the Standard Model, as are the couplings of the Higgs boson to the vector bosons once the Higgs mass is known. The vector boson fusion mechanism is examined in order to measure the process W + W -> Z + Z which has a favorable signal to noise ratio and which has a major contribution from the quartic coupling WWZZ.",0306160v1 2003-10-01,The trilinear neutral Higgs self-couplings in the MSSM. Complete one-loop analysis,"The Higgs boson effective self-couplings $\lambda_{hhh}$ and $\lambda_{HHH}$ are calculated in the framework of the Minimal Supersymmetric Standard Model (MSSM) for the complete set of one-loop diagrams with one of the Higgs bosons off-shell. The comparison with previous results, where only the leading correction terms in the limiting case of large masses of virtual particles were calculated, is carried out. We analyse the dependence of the self-couplings on the energy and ${\tt tan} \beta$; it is demonstrated that the tree-level self-couplings could acquire substantial one-loop corrections, which could be phenomenologically important.",0310018v1 2003-12-27,Flavor Structure of Scherk-Schwarz Supersymmetry Breaking for Quasi-Localized Matter Field,"We discuss the flavor structure of soft supersymmetry breaking parameters in 5-dimensional orbifold field theories in which N=1 supersymmetry is broken by the Scherk-Schwarz boundary condition and hierarchical 4-dimensional Yukawa couplings are obtained by quasi-localizing the matter fields in extra dimension. In such theories, the resulting soft scalar masses and trilinear scalar couplings at the compactification scale are highly flavor-dependent, but appropriately suppressed in correlation with Yukawa couplings. Those flavor violations can give interesting phenomenological consequences at low energies as well as constrain the mechanism of Yukawa coupling generation.",0312357v1 2004-10-05,The QCD analytic running coupling and chiral symmetry breaking,"We study the dependence on the pion mass of the QCD effective charge by employing the dispersion relations for the Adler D function. This new massive analytic running coupling is compared to the effective coupling saturated by the dynamically generated gluon mass. A qualitative picture of the possible impact of the former coupling on the chiral symmetry breaking is presented.",0410072v1 2004-11-03,Analysis of SO(2N) Couplings of Spinor and Tensor Representations in $SU(N)\times U(1)$ Invariant Forms,"A review is given of a recently developed technique for the analysis of SO(2N) invariant couplings which allows a full exhibition of the SU(N) invariant content of couplings involving the SO(2N) semi-spinors $|\Psi_{\pm}>$ with chiralilty $\pm$ and tensor representations. We discuss the Basic Theorem used in the analysis and then exhibit the technique by illustrative examples for the computation of the trilinear and quartic couplings for the SO(10) case involving three generations of 16 plets of matter.",0411054v1 2004-11-04,On an Intensity-Ratio Equivalence for Two Top-Quark Decay Couplings,"For the t --> W b decay mode, an intensity-ratio equivalence for two distinct Lorentz-invariant couplings is shown to be a consequence of symmetries of tWb-transformations. Three explicit tWb-transformations connect the four standard model's (SM) helicity amplitudes and the amplitudes in the case of an additional chiral-tensorial-coupling of relative strength 53 GeV. Such a coupling will arise if there is a large t_R --> b_L chiral weak-transition-moment. Two commutator plus anti-commutator symmetry algebras are generated from the 3 transformation matrices. Using these transformations, the associated mass scales are related to the SM's electroweak scale v_EW = 246GeV$.",0411072v1 2005-04-04,Weak-coupling techniques for the thermodynamics of the quark-gluon plasma,"We describe some of the recent progress in the calculation of thermodynamic quantities in QCD at high temperatures and densities by weak-coupling techniques and extrapolation to realistic coupling strength. We argue that a (mostly) weakly coupled quark-gluon plasma at temperatures only a few times the transition temperature is not yet ruled out by the observed fast apparent thermalization at RHIC, as nonabelian plasma instabilities might provide an efficient mechanism for fast isotropization even in a collisionless plasma.",0504023v3 2005-10-28,Non-perturbative renormalization of Phi-derivable approximations in theories with multiple fields,"We provide a renormalization procedure for Phi-derivable approximations in theories coupling different types of fields. We illustrate our approach on a scalar phi^4 theory coupled to fermions via a Yukawa-like interaction. The non-perturbative renormalization amounts to fixing the scalar coupling via a set of nested Bethe-Salpeter equations coupling fermions to scalars.",0510380v2 2005-11-01,Unitary Structure of the QCD Sum Rules and KYN and KYΞCouplings,"New relations between QCD Borel sum rules for strong coupling constants of K-mesons to baryons are derived. It is shown that starting from the sum rule for the coupling constants $g_{\pi\Sigma\Sigma}$ and $g_{\pi\Sigma\Lambda}$ it is straightforward to obtain corresponding sum rules for the $g_{K Y N}$, $g_{K Y \Xi}$ couplings, $Y=\Sigma,\Lambda$.",0511007v1 2006-02-03,Higgs Boson Mass From Orbifold GUTs,"We consider a class of seven-dimensional N=1 supersymmetric orbifold GUTs in which the Standard Model (SM) gauge couplings and one of the Yukawa couplings (top quark, bottom quark or tau lepton) are unified, without low energy supersymmetry, at M_{GUT} \simeq 4 \times 10^{16} GeV. With gauge-top quark Yukawa coupling unification the SM Higgs boson mass is estimated to be 135 \pm 6 GeV, which increases to 144 \pm 4 GeV for gauge-bottom quark (or gauge-tau lepton) Yukawa coupling unification.",0602040v2 2006-02-17,"Gauge Coupling Unification, SUSY Scale and Strong Coupling Running","The apparent unification of gauge couplings around 10^16 GeV is one of the strong arguments in favor of Supersymmetric extensions of the Standard Model (SM). In this contribution two new analyses of the gauge coupling running, the latter using in contrast to previous studies not data at the Z peak but at LEP2 energies, are presented. The generic SUSY scale in the more precise novel approach is 93 < M_SUSY < 183 GeV, easily within LHC, and possibly even within Tevatron reach.",0602168v1 2006-09-07,Anomalous Higgs boson couplings in vector boson fusion at the CERN LHC,"Deviations from SM expectations in the Higgs sector can be parameterized by an effective Lagrangian. The corresponding anomalous couplings have been implemented in a Monte Carlo program for Higgs production in vector boson fusion, at NLO QCD accuracy. It allows to study anomalous coupling effects for production and decay of the Higgs boson. We analyze deviations allowed by LEP data and study a new azimuthal angle variable which directly measures the interference between CP-even, CP-odd and SM couplings.",0609075v2 2006-09-19,Testing the SUSY-QCD Yukawa coupling in a combined LHC/ILC analysis,"In order to establish supersymmetry (SUSY) at future colliders, the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions needs to be verified. Here a first phenomenological study for determining the Yukawa coupling of the SUSY-QCD sector is presented, using a method which combines information from LHC and ILC.",0609180v1 2007-01-25,Couplings and spectra in modular inflation,"We analyze how the spectrum of perturbations produced in a multi-component modular inflation model proposed by Kadota and Stewart depends on couplings between the two moduli. Although some simple direct couplings give essentially the same results as the original model, $dn/d\ln k \propto n-1$, simple indirect couplings produce a power law spectrum, $n-1 = \textrm{constant}$, which can naturally be close to scale invariant.",0701213v2 1992-01-29,Interaction of Tachyons and Discrete States in c=1 2-D Quantum Gravity,"The two-dimensional (2-D) quantum gravity coupled to the conformal matter with $c=1$ is studied. We obtain all the three point couplings involving tachyons and/or discrete states via operator product expansion. We find that cocycle factors are necessary and construct them explicitly. We obtain an effective action for these three point couplings. This is a brief summary of our study of couplings of tachyons and discrete states, reported at the workshop in Tokyo Metropolitan University, December 4-6, 1991.",9201066v2 1992-03-25,Moduli Corrections to Gravitational Couplings from String loops,"We study moduli dependent threshold corrections to gravitational couplings in the case of the heterotic string compactified on a symmetric orbifold, for untwisted moduli, extending previous analysis on gauge couplings. Like in the gauge case, the contribution comes entirely from the spacetime $N=2$ sector. As a byproduct, this calculation provides a simple derivation of the trace anomaly coefficients for the different fields coupled to gravity.",9203071v1 1992-04-07,Matter Coupling and Spontaneous Symmetry Breaking in Topological Gravity,"Matter is coupled to three-dimensional gravity such that the topological phase is allowed and the (anti-) de Sitter or Poincar\'e symmetry remains intact. Spontaneous symmetry breaking to the Lorentz group occurs if a scalar field is included. This Higgs field can then be used to couple matter so that the familiar form of the matter coupling is established in the broken phase. We also give the supersymmetrization of this construction.",9204015v1 1992-12-11,Exactly Marginal Operators and Running Coupling Constants in 2D Gravity,"The Liouville action for two--dimensional quantum gravity coupled to interacting matter contains terms that have not been considered previously. They are crucial for understanding the renormalization group flow and can be observed in recent matrix model results for the phase diagram of the Sine--Gordon model coupled to gravity. These terms insure, order by order in the coupling constant, that the dressed interaction is exactly marginal. They are discussed up to second order.",9212075v3 1993-01-18,"Berenstein-Zelevinsky triangles, elementary couplings and fusion rules","We present a general scheme for describing su(N)_k fusion rules in terms of elementary couplings, using Berenstein-Zelevinsky triangles. A fusion coupling is characterized by its corresponding tensor product coupling (i.e. its Berenstein-Zelevinsky triangle) and the threshold level at which it first appears. We show that a closed expression for this threshold level is encoded in the Berenstein-Zelevinsky triangle and an explicit method to calculate it is presented. In this way a complete solution of su(4)_k fusion rules is obtained.",9301075v1 1993-11-02,Mirror Symmetry for Hypersurfaces in Weighted Projective Space and Topological Couplings,"By means of toric geometry we study hypersurfaces in weighted projective space of dimension four. In particular we compute for a given manifold its intrinsic topological coupling. We find that the result agrees with the calculation of the corresponding coupling on the mirror model in the large complex structure limit.",9311014v2 1994-01-11,A Study of Fermions Coupled to Gauge and Gravitational Fields on a Cylinder,"Fermions on a cylinder coupled to gravity and gauge fields are examined by studying the geometric action associated with the symmetries of such a system. The gauge coupling constant is shown to be constrained and the effect of gravity on the masses is discussed. Furthermore, we introduce a new gravitational theory which couples to the fermions by promoting the coadjoint vector of the diffeomorphism sector to a dynamical variable. This system, together with the gauge sector is shown to be equivalent to a one dimensional system.",9401039v2 1994-08-19,Conformal Invariance of Interacting WZNW Models,"We consider two level $k$ WZNW models coupled to each other through a generalized Thirring-like current-current interaction. It is shown that in the large $k$ limit, this interacting system can be presented as a two-parameter perturbation around a nonunitary WZNW model. The perturbation operators are the sigma model kinetic terms with metric related to the Thirring coupling constants. The renormalizability of the perturbed model leads to an algebraic equation for couplings. This equation coincides with the master Virasoro equation. We find that the beta functions of the two-parameter perturbation have nontrivial zeros depending on the Thirring coupling constants. Thus we exhibit that solutions to the master equation provide nontrivial conformal points to the system of two interacting WZNW models.",9408112v1 1994-09-07,Unification of the Soluble Two-dimensional vector coupling models,"The general theory of a massless fermion coupled to a massive vector meson in two dimensions is formulated and solved to obtain the complete set of Green's functions. Both vector and axial vector couplings are included. In addition to the boson mass and the two coupling constants, a coefficient which denotes a particular current definition is required for a unique specification of the model. The resulting four parameter theory and its solution are shown to reduce in appropriate limits to all the known soluble models, including in particular the Schwinger model and its axial vector variant.",9409038v1 1994-10-13,Towards a Strong Coupling Liouville Gravity,"A possibility of strong coupling quantum Liouville gravity is investigated via infinite dimensional representations of $\qslc$ with $q$ at a root of unity. It is explicitly shown that vertex operator in this model can be written by a tensor product of a vertex operator of the classical Liouville theory and that of weak coupling quantum Liouville theory. Some discussions about the strong coupling Liouville gravity within this formulation are given.",9410088v1 1995-03-21,Double expansion in asymptotically free theories,"I propose an approximation scheme for asymptotically free field theories combining both weak coupling and strong coupling series. The weak coupling expansion is used to integrate the high frequency modes and the resulting low energy effective theory is solved using the strong coupling expansion. In some models there exists an intermediate scale at which both expansions make sense. The method is tested on few low dimensional models for which an exact solution is known.",9503128v1 1995-04-01,STRINGY EVIDENCE FOR D=11 STRUCTURE IN STRONGLY COUPLED TYPE II-A SUPERSTRING,"Witten proposed that the low energy physics of strongly coupled D=10 type-IIA superstring may be described by D=11 supergravity. To explore the stringy aspects of the underlying theory we examine the stringy massive states. We propose a systematic formula for identifying non-perturbative states in D=10 type-IIA superstring theory, such that, together with the elementary excited string states, they form D=11 supersymmetric multiplets multiplets in SO(10) representations. This provides hints for the construction of a weakly coupled D=11 theory that is dual to the strongly coupled D=10 type IIA superstring.",9503228v1 1995-05-23,Dilaton Gravity Coupled to a Nonlinear Sigma Model in $2+ε$ Dimensions,"Quantum theory of dilaton gravity coupled to a nonlinear sigma model with a maximally symmetric target space is studied in $2+\epsilon$ dimensions. The ultraviolet stable fixed point for the curvature of the nonlinear sigma model demands a new fixed point theory for the dilaton coupling function. The fixed point of the dilaton coupling is a saddle point similarly to the previous case of the flat target space.",9505132v1 1995-06-07,THE NEW PHYSICS OF STRONGLY COUPLED 2D GRAVITY,"The strong coupling physics of two dimensional gravity at $C=7$, $13$, $19$ is summarized. It is based on a new set of local fields which do not preserve chirality. Thus this quantum number becomes ``deconfined'' in the strongly coupled regime. This new set leads to a novel definition of the area elements, and hence to a modified expression for the string suceptibility, which the real part of the KPZ formula. It allows to define topological (strongly coupled ) Liouville string theories (without transverse degree of freedom) which are completely solvable, and are natural extensions of the standard matrix models.",9506040v1 1995-06-19,Running surface couplings,"We discuss the renormalization group improved effective action and running surface couplings in curved spacetime with boundary. Using scalar self-interacting theory as an example, we study the influence of the boundary effects to effective equations of motion in spherical cap and the relevance of surface running couplings to quantum cosmology and symmetry breaking phenomenon. Running surface couplings in the asymptotically free SU(2) gauge theory are found.",9506117v1 1995-09-21,Strong coupling regime in two-dimensional large-N scalar quantum chromodynamics,"Two-dimensional large-$N$ quantum chromodynamics with scalar quarks is considered with particular emphasis on its strong coupling regime which has not been studied so far. Techniques necessary to deal with the infinitely oscillatory bound state wave functions in the strong coupling regime are developed. I derive an estimate for the ground state mass and show that (1) the lightest hadron in the theory is massless and (2) the ground state mass is continuous across the transition between the weak and the strong coupling.",9509117v2 1995-11-01,Reduction of Coupling Parameters,"The general theory of the reduction in the number of coupling parameters is discussed. The method involves renormalization group invariant relations between couplings. It is more general than the imposition of symmetries. There are reduced theories with no known symmetry. The reduction scheme is finding many applications. Discussed in some detail are the construction of gauge theories with ``minimal'' coupling for Yang-Mills and matter fields, and the Gauge-Yukawa Unification within N=1 supersymmetric GUT's.",9511006v1 1996-04-12,Prepotentials of N=2 SU(2) Yang-Mills theories coupled with massive matter multiplets,"We discuss N=2 SU(2) Yang-Mills gauge theories coupled with N_f (=2,3) massive hypermultiplets in the weak coupling limit. We determine the exact massive prepotentials and the monodromy matrices around the weak coupling limit. We also study that the double scaling limit of these massive theories and find that the massive N_f -1 theory can be obtained from the massive N_f theory. New formulae for the massive prepotentials and the monodromy matrices are proposed. In these formulae, N_f dependences are clarified.",9604059v2 1996-10-07,Is the String Coupling Constant invariant under T-duality?,"It is well known that under T-duality the sigma model dilaton (which is normally thought to be related to the string coupling constant through the simple formula $\kappa = exp <\phi >$), undergoes an additive shift. On the other hand, Kugo and Zwiebach, using a simplified form of string field theory, claim that the string coupling constant does not change under the T-duality. Obviously, what seems to happen is that two different coupling constants, associated to different dilatons, are used. In this contribution we shall try to clarify this, and related issues.",9610032v1 1997-05-02,Exact Renormalization Group and Running Newtonian Coupling in Higher Derivative Gravity,"We discuss exact renormalization group (RG) in $R^2$-gravity using effective average action formalism. The truncated evolution equation for such a theory on De Sitter background leads to the system of nonperturbative RG equations for cosmological and gravitational coupling constants. Approximate solution of these RG equations shows the appearence of antiscreening and screening behaviour of Newtonian coupling what depends on higher derivative coupling constants.",9705008v1 1997-07-17,Integrability of Coupled Conformal Field Theories,"The massive phase of two-layer integrable systems is studied by means of RSOS restrictions of affine Toda theories. A general classification of all possible integrable perturbations of coupled minimal models is pursued by an analysis of the (extended) Dynkin diagrams. The models considered in most detail are coupled minimal models which interpolate between magnetically coupled Ising models and Heisenberg spin-ladders along the $c<1$ discrete series.",9707159v2 1998-02-03,A Solvable Model of Two-Dimensional Dilaton-Gravity Coupled to a Massless Scalar Field,"We present a solvable model of two-dimensional dilaton-gravity coupled to a massless scalar field. We locally integrate the field equations and briefly discuss the properties of the solutions. For a particular choice of the coupling between the dilaton and the scalar field the model can be interpreted as the two-dimensional effective theory of 2+1 cylindrical gravity minimally coupled to a massless scalar field.",9802013v1 1998-02-10,Vortex Solutions of Four-fermion Theory coupled to a Yang-Mills-Chern-Simons Gauge Field,"We have constructed a four-fermion theory coupled to a Yang-Mills-Chern-Simons gauge field which admits static multi-vortex solutions. This is achieved through the introduction of an anomalous magnetic interation term in addition to the usual minimal coupling, and the appropriate choice of the fermion quartic coupling constant.",9802062v2 1998-03-18,Quantum modified moduli spaces and field dependent gauge couplings,"In this paper we discuss quantum modified moduli spaces in supergravity. We examine a model suggested by Izawa and Yanagida and by Intriligator and Thomas that breaks global supersymmetry by a quantum deformation of the classical moduli space. We determine the minimum of the supergravity potential when the gauge coupling is taken to depend on a dynamical field, typically a modulus of string theory. We find that the only minimum is at the trivial configuration of vanishing coupling constant and unbroken supersymmetry. We also discuss models involving more complicated superpotentials and find that the gauge coupling is only stabilized in a supersymmetric ground state.",9803143v1 1998-03-20,Axial and gauge anomalies in a theory with one and two-form gauge fields,"We study the problem of axial and gauge anomalies in a reducible theory involving vector and tensor gauge fields coupled in a topological way. We consider that vector and axial fermionic currents couple with the tensor field in the same topological manner as the vector gauge one. This kind of coupling leads to an anomalous axial current, contrarily to the results found in literature involving other tensor couplings, where no anomaly is obtained.",9803172v1 1998-09-01,Cosmic Strings in the Abelian Higgs Model with Conformal Coupling to Gravity,"Cosmic string solutions of the abelian Higgs model with conformal coupling to gravity are shown to exist. The main characteristics of the solutions are presented and the differences with respect to the minimally coupled case are studied. An important difference is the absence of Bogomolnyi cosmic string solutions for conformal coupling. Several new features of the abelian Higgs cosmic strings of both types are discussed. The most interesting is perhaps a relation between the angular deficit and the central magnetic field which is bounded by a critical value.",9809002v2 1999-03-16,Vortex Solutions of Nonrelativistic Fermion and Scalar Field Theories Coupled to Maxwell-Chern-Simons theories,"We have constructed nonrelativistic fermion and scalar field theories coupled to a Maxwell-Chern-Simons gauge field which admit static multi-vortex solutions. This is achieved by introducing a magnetic coupling term in addition to the usual minimal coupling.",9903138v2 1999-04-06,Some Speculations on the Gauge Coupling in the AdS/CFT Approach,"We propose the principle that the scale of the glueball masses in the AdS/CFT approach to QCD should be set by the square root of the string tension. It then turns out that the strong bare coupling runs logarithmically with the ultraviolet cutoff T if first order world sheet fluctuations are included. We also point out that in the end, when all corrections are included, one should obtain an equation for the coupling running with T which has some similarity with the equation for the strong bare coupling.",9904034v2 1999-10-26,A Simple Proof of the Non-Renormalization of the Chern-Simons Coupling,"We give a very simple proof that the renormalization of the Chern-Simons coupling in the Wilsonian effective action is exhausted at one-loop. Our proof can apply to arbitrary 2+1-dimensional abelian as well as nonabelian gauge theories without a bare Chern-Simons coupling, including any non-renormalizable interactions and non-minimal couplings. Our proof reveals that small (but not large) gauge invariance is enough to ensure the absence of higher order corrections.",9910200v3 2000-05-24,Supergravity couplings: a geometric formulation,"This report provides a pedagogical introduction to the description of the general Poincare supergravity/matter/Yang-Mills couplings using methods of Kahler superspace geometry. At a more advanced level this approach is generalized to include tensor field and Chern-Simons couplings in supersymmetry and supergravity, relevant in the context of weakly and strongly coupled string theories.",0005225v1 2000-11-01,Scale Invariance in a Non-Abelian Chern-Simons-Matter Model,"The general method of reduction in the number of coupling parameters is applied in a Chern-Simons-matter model with several independent couplings. We claim that considering the asymptotic region, and expressing all dimensionless coupling parameters as functions of the Chern-Simons coupling, it is possible to show that all $\beta$-functions vanish to any order of perturbative series. Therefore, the model is asymptotically scale invariant.",0011007v3 2000-12-18,Holography and Phenomenology,"We examine various aspects of the conjectured duality between warped AdS$_5$ geometries with boundary branes and strongly coupled (broken) conformal field theories coupled to dynamical gravity. We also examine compactifications with 5-d gauge fields, in which case the holographic dual is a broken CFT weakly coupled to dynamical gauge fields in addition to gravity. The holographic picture is used to clarify a number of important phenomenological issues in these and related models, including the questions of black hole production, radius stabilization, early universe cosmology, and gauge coupling unification.",0012148v1 2001-06-15,"""Dynamical"" non-minimal higher-spin interaction and gyromagnetic ratio g=2","The field-dependent invariant representation (the ""dynamical"" representation) of the Poincar\'e algebra is considered as a dynamical principle in order to get the corresponding ""dynamical"" electromagnetic coupling for higher spins ($s\geq 1$). If in lower-spin ($s=0,1/2$) cases the ""dynamical"" coupling is taken to coincide with the minimal electromagnetic coupling the higher-spin coupling is inevitably non-minimal, containing a term linear in the field strength tensor $F_{\mu\nu}$. This term leads to $g=2$.",0106137v1 2001-07-11,Ramond-Ramond Couplings of Noncommutative Branes,"We obtain the couplings of noncommutative branes of type II string theories to constant Ramond-Ramond backgrounds, for BPS as well as non-BPS branes, in the background-independent description. For the BPS branes, we also generalize these couplings to other descriptions, and thereby argue their equivalence to the known couplings in the commutative description. The first part is a review of earlier work while the second part contains some additional observations.",0107087v2 2001-08-16,Unification and the Hierarchy from AdS5,"In AdS5, the coupling for bulk gauge bosons runs logarithmically, not as a power law. For this reason, one can preserve perturbative unification of couplings. Depending on the cutoff, this can occur at a high scale. We discuss subtleties in the calculation and present a regularization scheme motivated by the holographic correspondence. We find that generically, as in the standard model, the couplings almost unify. For specific choices of the cutoff and number of scalar multiplets, there is good agreement between the measured couplings and the assumption of high scale unification.",0108115v1 2004-06-29,A Curious Truncation of N=4 Yang-Mills,"The coupling constant dependence of correlation functions of BPS operators in N=4 Yang-Mills can be expressed in terms of integrated correlation functions. We approximate these integrated correlators by using a truncated OPE expansion. This leads to differential equations for the coupling dependence. When applied to a particular sixteen point correlator, the coupling dependence we find agrees with the corresponding amplitude computed via the AdS/CFT correspondence. We conjecture that this truncation becomes exact in the large N and large 't Hooft coupling limit.",0406267v2 2004-09-22,Bounding Gauged Skyrmion Masses,"Normally, standard (ungauged) skyrmion masses are proportional to the coupling of the Skyrme term needed for stability, and so can grow to infinite magnitude with increasing coupling. In striking contrast, when skyrmions are gauged, their masses are bounded above for any Skyrme coupling, and, instead, are of the order of monopole masses, O(v/g), so that the coupling of the Skyrme term is not very important. This boundedness phenomenon and its implications are investigated.",0409222v1 2004-12-21,The symmetric branes of the H4 WZW model,"We review the solution of the boundary CFTs that describe the symmetric branes in the Nappi-Witten gravitational wave, namely D2 and S1 branes. The D2 branes are the twisted branes of the model while the S1 branes are the Cardy branes. We present in both cases the bulk-boundary couplings and the boundary three-point couplings and discuss the relation with branes in AdS3 and in S3. We also discuss the analogy between the open string couplings in the H4 model and the couplings for magnetized and intersecting branes.",0412258v2 2005-09-07,Gravitational Correction to Running of Gauge Couplings,"We calculate the contribution of graviton exchange to the running of gauge couplings at lowest non-trivial order in perturbation theory. Including this contribution in a theory that features coupling constant unification does not upset this unification, but rather shifts the unification scale. When extrapolated formally, the gravitational correction renders all gauge couplings asymptotically free.",0509050v2 2005-12-13,Time variation of the gravitational coupling constant in decrumpling cosmology,"Within the framework of a model universe with time variable space dimension (TVSD) model, known as decrumpling or TVSD model, we study the time variation of the gravitational coupling constant. Using observational bounds on the present time variation of the gravitational Newton's constant in three-dimensional space we are able to obtain a constraint on the time variation of the gravitational coupling constant. As a result, the absolute value of the time variation of the gravitational coupling constant must be less than $\sim 10^{-11} {\rm yr}^{-1}$.",0512139v3 2006-10-19,AdS/CFT duality at strong coupling,"We study the strong coupling limit of AdS/CFT correspondence in the framework of a recently proposed fermionic formulation of the Bethe Ansatz equations governing the gauge theory anomalous dimensions. We provide examples of states that do not follow the Gubser-Klebanov-Polyakov law at large 't Hooft coupling $\lambda$, in contrast with recent results on the quantum string Bethe equations valid in that regime. This result indicates that the fermionic construction cannot be trusted at large $\lambda$, although it remains an efficient tool to compute the weak coupling expansion of anomalous dimensions.",0610215v1 2007-03-21,"On the coupling of tensors to gauge fields: D=5, N=2 supergravity revisited","A general free differential algebra encoding the anti-Higgs mechanism among two-index antisymmetric tensors and gauge vectors is analyzed at the full group theoretical level. N=2 supergravity in five dimensions coupled to tensor, vector and hyper multiplets with all possible couplings included is reconsidered from this point of view. Within our approach, we find that some of the constraints on the couplings usually considered are too stringent and may in fact be relaxed. This generalization also affects the scalar potential.",0703188v1 1992-09-25,Calderón couples of re-arrangement invariant spaces,"We examine conditions under which a pair of re-arrangement invariant function spaces on $[0,1]$ or $[0,\infty)$ form a Calder\'on couple. A very general criterion is developed to determine whether such a pair is a Calder\'on couple, with numerous applications. We give, for example, a complete classification of those spaces $X$ which form a Calder\'on couple with $L_{\infty}.$ We specialize our results to Orlicz spaces and are able to give necessary and sufficient conditions on an Orlicz function $F$ so that the pair $(L_F,L_{\infty})$ forms a Calder\'on pair.",9209217v1 2005-04-21,Block-diagonalization of the linearized coupled-mode system,"We consider the Hamiltonian coupled-mode system that occur in nonlinear optics, photonics, and atomic physics. Spectral stability of gap solitons is determined by eigenvalues of the linearized coupled-mode system, which is equivalent to a four-by-four Dirac system with sign-indefinite metric. In the special class of symmetric nonlinear potentials, we construct a block-diagonal representation of the linearized equations, when the spectral problem reduces to two coupled two-by-two Dirac systems. The block-diagonalization is used in numerical computations of eigenvalues that determine stability of gap solitons.",0504442v1 2005-12-14,Coupling all the Lévy stochastic areas of multidimensional Brownian motion,"It is shown how to construct a successful co-adapted coupling of two copies of an $n$-dimensional Brownian motion $(B_1,...,B_n)$ while simultaneously coupling all corresponding copies of L\'{e}vy stochastic areas $\int B_i dB_j-\int B_j dB_i$. It is conjectured that successful co-adapted couplings still exist when the L\'{e}vy stochastic areas are replaced by a finite set of multiply iterated path- and time-integrals, subject to algebraic compatibility of the initial conditions.",0512336v2 2006-09-29,Enhanced binding for N-particle system interacting with a scalar bose field I,"An enhanced binding of an $N$-particle system interacting through a scalar bose field is investigated, where $N\geq 2$. It is not assumed that this system has a ground state for a zero coupling. It is shown, however, that there exists a ground state for a sufficiently large values of coupling constants. When the coupling constant is sufficiently large, $N$ particles are bound to each other by the scalar bose field, and are trapped by external potentials. Basic ideas of the proofs in this paper are applications of a weak coupling limit and a modified HVZ theorem.",0609086v1 2006-12-12,The bipolaron in the strong coupling limit,"The bipolaron are two electrons coupled to the elastic deformations of an ionic crystal. We study this system in the Fr\""{o}hlich approximation. If the Coulomb repulsion dominates, the lowest energy states are two well separated polarons. Otherwise the electrons form a bound pair. We prove the validity of the Pekar-Tomasevich energy functional in the strong coupling limit, yielding estimates on the coupling parameters for which the binding energy is strictly positive. Under the condition of a strictly positive binding energy we prove the existence of a ground state at fixed total momentum $P$, provided $P$ is not too large.",0612035v1 2007-03-16,Approximations of singular vertex couplings in quantum graphs,"We discuss approximations of the vertex coupling on a star-shaped quantum graph of $n$ edges in the singular case when the wave functions are not continuous at the vertex and no edge-permutation symmetry is present. It is shown that the Cheon-Shigehara technique using $\delta$ interactions with nonlinearly scaled couplings yields a $2n$-parameter family of boundary conditions in the sense of norm resolvent topology. Moreover, using graphs with additional edges one can approximate the ${n+1\choose 2}$-parameter family of all time-reversal invariant couplings.",0703051v1 1998-04-01,Bilinearization of coupled nonlinear Schrödinger type equations: integrabilty and solitons,"Considering the coupled envelope equations in nonlinear couplers, the question of integrability is attempted. It is explicitly shown that Hirota's bilinear method is one of the simple and alternative techniques to Painlev\'e analysis to obtain the integrability conditions of the coupled nonlinear Schr\""odinger (CNLS) type equations. We also show that the coupled Hirota equation introduced by Tasgal and Potasek is the next hierarchy of the inverse scattering solvable CNLS equation. The results are in agreement with the known results.",9804202v1 2000-09-27,Synchronization of rescaled adaptive coupling and its application to shock capturing,"This Letter proposes a rescaled adaptive coupling scheme for the synchronization of spatially extended systems. Coupling and synchronization are analyzed from the point view of image filter construction. A length rescaling technique is introduced based on dimensional argument of control process. Control sensors are adaptively selected according to local information. The coupling strength on each sensor is automatically adjusted according to the magnitude of local oscillations. We demonstrate that the present scheme can efficiently suppress and control spatiotemporal oscillations and thus, provide a powerful approach for shock capturing. Both the Navier-Stokes equation describing shear layer flows around a jet and Burgers' equation are solved to illustrate the idea.",0009048v1 2001-04-09,Effective Coupling for Open Billiards,"We derive an explicit expression for the coupling constants of individual eigenstates of a closed billiard which is opened by attaching a waveguide. The Wigner time delay and the resonance positions resulting from the coupling constants are compared to an exact numerical calculation. Deviations can be attributed to evanescent modes in the waveguide and to the finite number of eigenstates taken into account. The influence of the shape of the billiard and of the boundary conditions at the mouth of the waveguide are also discussed. Finally we show that the mean value of the dimensionless coupling constants tends to the critical value when the eigenstates of the billiard follow random-matrix theory.",0104023v1 2001-04-10,Information processing by a controlled coupling process,"This Letter proposes a controlled coupling process for information processing. The net effect of conventional coupling is isolated from the dynamical system and is analyzed in depth. The stability of the process is studied. We show that the proposed process can locally minimize the smoothness and the fidelity of dynamical data. A digital filter expression of the controlled coupling process is derived and the connection is made to the Hanning filter. The utility and robustness of proposed approach is demonstrated by both the restoration of the contaminated solution of the nonlinear Schr\""{o}dinger equation and the estimation of the trend of a time series.",0104026v1 2001-06-11,Analysis of Hamiltonian Dynamics of Dispersion-Managed Coupled Breathers in Optical Transmission System,"We theoretically derive the Hamiltonian dynamics of dispersion-managed coupled breathers in optical transmission system as a result of phases-plane dynamics of the system. We analytically show that the contribution of a perturbation term caused by a noise sourced by amplifiers in optical fiber can influence the amplitudes and chirps of the pulses dynamics. We also find that the coupled breathers dynamics depent on a certain relationship of the chirps and amplitudes. The results of the perturbed coupled NLS are then reduced to that in the unperturbed system and the single NLS case.",0106009v1 2001-11-01,Exact anticipating synchronization in bi-directionally coupled time-delayed systems,"We present an analytical investigation of exact anticipating synchronization between two bi-idirectionally coupled time-delayed systems in the case when these systems are governed by two characteristic times: the delay time in the coupling and the delay time in the coupled systems. We apply our approach to interpret the results of recent first experimental observation of anticipating chaos synchronization in external cavity semiconductor lasers with optical feedback.We establish that our approach can explain the experimental results only for special cases.",0111002v1 2001-11-02,Exact Lag Synchronization in Time Delay Systems and Why Experimental Lag Times Can Differ from Theoretical Predictions,"We present analytical investigation of exact lag synchronization between two unidirectionally coupled identical time delay systems with two characteristic delay times, where the delay time in the coupling is different from the delay time in the coupled systems themselves. For the first time we demonstrate that parameter mismatches can explain the experimental observation that the lag time is equal to the coupling delay.",0111006v1 2002-02-04,Information transfer and nontrivial collective behavior in chaotic coupled map networks,"The emergence of nontrivial collective behavior in networks of coupled chaotic maps is investigated by means of a nonlinear mutual prediction method. The resulting prediction error is used to measure the amount of information that a local unit possesses about the collective dynamics. Applications to locally and globally coupled map systems are considered. The prediction error exhibits phase transitions at critical values of the coupling for the onset of ordered collective behavior in these networks. This information measure may be used as an order parameter for the characterization of complex behavior in extended chaotic systems.",0202010v1 2002-03-11,Different regimes of synchronization in nonidentical time-delayed maps,"We study the synchronization of time-delayed nonidentical maps subject to unidirectional (master-slave) coupling. The individual dynamics of the maps have a delay n1, and the coupling acts with a delay n2. We show analytically that, suitably tuning the slave map parameters, two distinct synchronization regimes can occur. In one regime the lag time between the slave and the master maps is given by the delay of the coupling, n2, while in the other regime is given by the difference between the delays, n1-n2. We analyze the effect of the coupling strength on the different synchronization regimes in logistic and H\'enon maps.",0203017v1 2002-03-15,Phase-locked and phase drift solutions of phase oscillators with asymmetric coupling strengths,"Phase-locked solutions of coupled oscillators are studied with asymmetric coupling strengths or inhomogeneous natural frequencies. The solutions show remarkable profiles of phase lags from the pacemaker corresponding to the ratio of upward and downward coupling strengths. By means of the existence condition of phase-locked solutions, the transition points from phase-locked to phase drift states are estimated. The application of the existence condition to the case of the linear gradient of natural frequency illustrates some scaling properties in the frequency diagrams.",0203032v1 2002-10-07,Self-organized and driven phase synchronization in coupled maps,"We study the phase synchronization and cluster formation in coupled maps on different networks. We identify two different mechanisms of cluster formation; (a) {\it Self-organized} phase synchronization which leads to clusters with dominant intra-cluster couplings and (b) {\it driven} phase synchronization which leads to clusters with dominant inter-cluster couplings. In the novel driven synchronization the nodes of one cluster are driven by those of the others. We also discuss the dynamical origin of these two mechanisms for small networks with two and three nodes.",0210006v2 2002-10-09,Route to chaotic synchronisation in coupled map lattices: Rigorous results,"Two-dimensional mappings obtained by coupling two piecewise increasing expanding maps are considered. Their dynamics is described when the coupling parameter increases in the expanding domain. By introducing a coding and by analysing an admissibility condition, approximations of the corresponding symbolic systems are obtained. These approximations imply that the topological entropy is located between two decreasing step functions of the coupling parameter. The analysis firstly applies to mappings with piecewise affine local maps which allow explicit expressions and, in a second step, is extended by continuity to mappings with piecewise smooth local maps.",0210019v1 2002-10-24,Stochastic synchronization in globally coupled phase oscillators,"Cooperative effects of periodic force and noise in globally Cooperative effects of periodic force and noise in globally coupled systems are studied using a nonlinear diffusion equation for the number density. The amplitude of the order parameter oscillation is enhanced in an intermediate range of noise strength for a globally coupled bistable system, and the order parameter oscillation is entrained to the external periodic force in an intermediate range of noise strength. These enhancement phenomena of the response of the order parameter in the deterministic equations are interpreted as stochastic resonance and stochastic synchronization in globally coupled systems.",0210056v1 2002-12-27,General Stability Analysis of Synchronized Dynamics in Coupled Systems,"We consider the stability of synchronized states (including equilibrium point, periodic orbit or chaotic attractor) in arbitrarily coupled dynamical systems (maps or ordinary differential equations). We develop a general approach, based on the master stability function and Gershgorin disc theory, to yield constraints on the coupling strengths to ensure the stability of synchronized dynamics. Systems with specific coupling schemes are used as examples to illustrate our general method.",0212051v1 2003-04-02,Inverse scattering approach to coupled higher order nonlinear Schrödinger equation and N-soliton solutions,"A generalized inverse scattering method has been applied to the linear problem associated with the coupled higher order nonlinear schr\""odinger equation to obtain it's $N$-soliton solution. An infinite number of conserved quantities have been obtained by solving a set of coupled Riccati equations. It has been shown that the coupled system admits two different class of solutions, characterised by the number of local maxima of amplitude of the soliton.",0304004v1 2003-05-02,Phase separation in coupled chaotic maps on fractal networks,"The phase ordering dynamics of coupled chaotic maps on fractal networks are investigated. The statistical properties of the systems are characterized by means of the persistence probability of equivalent spin variables that define the phases. The persistence saturates and phase domains freeze for all values of the coupling parameter as a consequence of the fractal structure of the networks, in contrast to the phase transition behavior previously observed in regular Euclidean lattices. Several discontinuities and other features found in the saturation persistence curve as a function of the coupling are explained in terms of changes of stability of local phase configurations on the fractals.",0305004v1 2003-09-21,Painlevé test of coupled Gross-Pitaevskii equations,"Painlev\'{e} test of the coupled Gross-Pitaevskii equations has been carried out with the result that the coupled equations pass the P-test only if a special relation containing system parameters (masses, scattering lengths) is satisfied. Computer algebra is applied to evaluate j=4 compatibility condition for admissible external potentials. Appearance of an arbitrary real potential embedded in the external potentials is shown to be the consequence of the coupling. Connection with recent experiments related to stability of two-component Bose-Einstein condensates of Rb atoms is discussed.",0309056v1 2003-12-10,Periodic orbit theory of two coupled Tchebyscheff maps,"Coupled map lattices have been widely used as models in several fields of physics, such as chaotic strings, turbulence, and phase transitions, as well as in other disciplines, such as biology (ecology, evolution) and information processing. This paper investigates properties of periodic orbits in two coupled Tchebyscheff maps. The zeta function cycle expansions are used to compute dynamical averages appearing in Beck's theory of chaotic strings. The results show close agreement with direct simulation for most values of the coupling parameter, and yield information about the system complementary to that of direct simulation.",0312024v1 2004-01-22,Chaos synchronization in long-range coupled map lattices,"We investigate the synchronization phenomenon in coupled chaotic map lattices where the couplings decay with distance following a power-law. Depending on the lattice size, the coupling strength and the range of the interactions, complete chaos synchronization may be attained. The synchronization domain in parameter space can be analytically delimited by means of the condition of negativity of the largest transversal Lyapunov exponent. Here we analyze in detail the role of all the system parameters in the ability of the lattice to achieve complete synchronization, testing analytical results with the outcomes of numerical experiments.",0401034v1 2004-07-19,Chimera States for Coupled Oscillators,"Arrays of identical oscillators can display a remarkable spatiotemporal pattern in which phase-locked oscillators coexist with drifting ones. Discovered two years ago, such ""chimera states"" are believed to be impossible for locally or globally coupled systems; they are peculiar to the intermediate case of nonlocal coupling. Here we present an exact solution for this state, for a ring of phase oscillators coupled by a cosine kernel. We show that the stable chimera state bifurcates from a spatially modulated drift state, and dies in a saddle-node bifurcation with an unstable chimera.",0407045v1 2004-09-27,Combination of anticipated and isochronous synchronization in coupled semiconductor lasers system,"Combination of two basic types of synchronization, anticipated and isochronous synchronization, is investigated numerically in coupled semiconductor lasers. Due to the combination, a synchronization of good quality can be obtained. We study the dependence of the lag time between two lasers and the synchronization quality on the converse coupling retardation time $\tau_{c21}$. When $\tau_{c21}$ is close to the difference of external cavity round trip time $\tau$ and coupling retardation time $\tau_{c12}$, the combination of anticipated and isochronous synchronization may produce a better synchronization, with a lag time proportional to $\tau_{c21}$. When $\tau_{c21}$ is largely different from $\tau-\tau_{c12}$, the combination is noneffective and even negative in some cases, with a lag time independent of $\tau_{c21}$.",0409056v1 2005-06-08,Energy localization in two chaotically coupled systems,"We set up and analyze a random matrix model to study energy localization and its time behavior in two chaotically coupled systems. This investigation is prompted by a recent experimental and theoretical study of Weaver and Lobkis on coupled elastomechanical systems. Our random matrix model properly describes the main features of the findings by Weaver and Lobkis. Due to its general character, our model is also applicable to similar systems in other areas of physics -- for example, to chaotically coupled quantum dots.",0506017v1 2005-08-10,Fractal Stationary Density in Coupled Maps,"We study the invariant measure or the stationary density of a coupled discrete dynamical system as a function of the coupling parameter \epsilon (0 < \epsilon < 1/4). The dynamical system considered is chaotic and unsynchronized for this range of parameter values. We find that the stationary density, restricted on the synchronization manifold, is a fractal function. We find the lower bound on the fractal dimension of the graph of this function and show that it changes continuously with the coupling parameter",0508017v1 2005-09-06,On possibility of realization of the Mandelbrot set in coupled continuous systems,"According to the method, suggested in our previous work (nlin/0509012) and based on the consideration of the specially coupled systems, the possibility of physical realization of the phenomena of complex analytic dynamics (such as Mandelbrot and Julia sets) is discussed. It is shown, that unlike the case of discrete maps or differential systems with periodic driving, investigated in mentioned work, there are some difficulties in attempts to obtain the Mandelbrot set for the coupled autonomous continuous systems. A system of coupled autonomous R\""{o}ssler oscillators is considered as an example.",0509013v1 2005-10-03,Synchronization by Reactive Coupling and Nonlinear Frequency Pulling,"We present a detailed analysis of a model for the synchronization of nonlinear oscillators due to reactive coupling and nonlinear frequency pulling. We study the model for the mean field case of all-to-all coupling, deriving results for the initial onset of synchronization as the coupling or nonlinearity increase, and conditions for the existence of the completely synchronized state when all the oscillators evolve with the same frequency. Explicit results are derived for Lorentzian, triangular, and top-hat distributions of oscillator frequencies. Numerical simulations are used to construct complete phase diagrams for these distributions.",0510002v1 2005-10-04,Synchronization of Coupled Chaotic Dynamics on Networks,"We review some recent work on the synchronization of coupled dynamical systems on a variety of networks. When nodes show synchronized behaviour, two interesting phenomena can be observed. First, there are some nodes of the floating type that show intermittent behaviour between getting attached to some clusters and evolving independently. Secondly, two different ways of cluster formation can be identified, namely self-organized clusters which have mostly intra-cluster couplings and driven clusters which have mostly inter-cluster couplings.",0510008v1 2005-12-15,Transitions To the Long-Resident State in coupled chaotic oscillators,"The behaviors of coupled chaotic oscillators before complete synchronization were investigated. We report three phenomena: (1) The emergence of long-time residence of trajectories besides one of the saddle foci; (2) The tendency that orbits of the two oscillators get close becomes faster with increasing the coupling strength; (3) The diffusion of two oscillator's phase difference is first enhanced and then suppressed. There are exact correspondences among these phenomena. The mechanism of these correspondences is explored. These phenomena uncover the route to synchronization of coupled chaotic oscillators.",0512037v1 2006-12-05,Random global coupling induces synchronization and nontrivial collective behavior in networks of chaotic maps,"The phenomena of synchronization and nontrivial collective behavior are studied in a model of coupled chaotic maps with random global coupling. The mean field of the system is coupled to a fraction of elements randomly chosen at any given time. It is shown that the reinjection of the mean field to a fraction of randomly selected elements can induce synchronization and nontrivial collective behavior in the system. The regions where these collective states emerge on the space of parameters of the system are calculated.",0612010v1 2006-12-22,Ring Intermittency in Coupled Chaotic Oscillators at the Boundary of Phase Synchronization,"A new type of intermittent behavior is described to occur near the boundary of phase synchronization regime of coupled chaotic oscillators. This mechanism, called ring intermittency, arises for sufficiently high initial mismatches in the frequencies of the two coupled systems. The laws for both the distribution and the mean length of the laminar phases versus the coupling strength are analytically deduced. A very good agreement between the theoretical results and the numerically calculated data is shown. We discuss how this mechanism is expected to take place in other relevant physical circumstances.",0612049v1 1995-02-07,THE COUPLING OF THE $f_1(1285)$ MESON TO THE ISOSCALAR AXIAL CURRENT OF THE NUCLEON,"The weak decay as well as the strong nucleon coupling constants of the isoscalar axial vector meson $f_1 (1285)$ are estimated within the octet quark model. It is shown that the empirical value for the coupling of $\overline{s}s$ quarkonium to nucleons can be understood by attributing the $f_1(1285)$-nucleon coupling to the $a_0\pi N$ triangle diagram.",9502018v1 1998-09-11,Damping of giant resonances in asymmetric nuclear matter,"The giant collective modes in asymmetric nuclear matter are investigated within a dynamic relaxation time approximation. We derive a coupled dispersion relation and show that two sources of coupling appear: (i) a coupling of isoscalar and isovector modes due to different mean-fields acting and (ii) an explicit new coupling in asymmetric matter due to collisional interaction. We show that the latter one is responsible for a new mode arising besides isovector and isoscalar modes.",9809035v1 1999-01-13,About QCD sum rules for pion-nucleon coupling,"We point out subtleties in the previous sum rule calculations of the $\pi NN$ coupling associated with using either the PV or the PS coupling schemes in modeling the phenomenological side. We propose a sum rule which is independent of the coupling schemes used and has less uncertainty in the OPE. The obtained value is $g_{\pi N}=9.76 \pm 2.04$ where the uncertainty mainly comes from the quark-gluon mixed condensate.",9901029v1 2000-06-30,On a q-analogue of the spin-orbit coupling,"Based on the tensor method, a q-analoque of the spin-orbit coupling is introduced in a q-deformed Schroedinger equation, previously derived for a central potential. Analytic expressions for the matrix elemnets of the representation j=l\pm 1/2 are derived. The spectra of the harmonic oscillator and the Coulomb potential are calculated numerically as a function of the deformation parameter, without and with the spin-orbit coupling. The harmonic oscillator spectrum presents strong analogies with the bound spectrum of an Woods-Saxon potential customarily used in nuclear physics. The Coulomb spectrum simulates relativistic effects. The addition of the spin-orbit coupling reinforces this picture.",0006081v1 2003-09-15,Coupled collective motion in nuclear reactions,"In this paper, we review the roles of collective modes in nuclear reactions. We emphaize the strong couplings of various collective states with the monopole and quadrupole motions. In inelastic excitation, these couplings can be seen as an important source of anharmonicity in the multiphonon spectrum. In fusion reaction, the breathing and quadrupole motions strongly affects the oscillation of protons against neutrons. Finally, the modification of the collective properties induced by a large amplitude dilution might be the origin of the nuclear multifragmentation, directly related to the nuclear liquid-gas phase transition. In the three cases we derive a coupling matrix element which appears to be in good agreement.",0309036v1 2003-11-12,Goldberger-Treiman constraint criteria for hyperon coupling constants,"The generalized Goldberger-Treiman relation is combined with the Dashen-Weinstein sum rule to provide a constraint equation between the g(KSigmaN) and g(KLambdaN) coupling constants. A comprehensive examination of the published phenomenological and theoretical hyperon couplings has yielded a much smaller set of values, spanning the intervals 0.80<=g(KSigmaN)/Sqrt(4Pi)<=2.72 and -3.90<=g(KLambdaN)/Sqrt(4Pi)<=-1.84, consistent with this criteria. The SU(3) and Goldberger-Treiman hyperon couplings satisfy the constraint along with predictions from a Taylor series extrapolation using the same momentum variation as exhibited by g(PiNN).",0311039v2 2004-02-18,Gamow and R-matrix Approach to Proton Emitting Nuclei,"Proton emission from deformed nuclei is described within the non-adiabatic weak coupling model which takes into account the coupling to $\gamma$-vibrations around the axially-symmetric shape. The coupled equations are derived within the Gamow state formalism. A new method, based on the combination of the R-matrix theory and the oscillator expansion technique, is introduced that allows for a substantial increase of the number of coupled channels. As an example, we study the deformed proton emitter $^{141}$Ho.",0402063v1 2004-06-05,The dielectric function excited by $ρNN$ tensor coupling in nuclear matter,"The dielectric function of nuclear matter excited by $\rho NN$ tensor coupling has been studied in the framework of Finite temperature field theory. The induced current mechanism has been introduced to explain the three extrema on the dielectric function curve, of which one is in the space-like region and the other two are in the time-like region. It points out that the tensor coupling contributes much more large amplitude than the vector coupling and plays a more important role on the time-like region compared with its effect on the space-like region.",0406014v1 2005-06-14,Random-phase approximation based on relativistic point-coupling models,"The matrix equations of the random-phase approximation (RPA) are derived for the point-coupling Lagrangian of the relativistic mean-field (RMF) model. Fully consistent RMF plus (quasiparticle) RPA illustrative calculations of the isoscalar monopole, isovector dipole and isoscalar quadrupole response of spherical medium-heavy and heavy nuclei, test the phenomenological effective interactions of the point-coupling RMF model. A comparison with experiment shows that the best point-coupling effective interactions accurately reproduce not only ground-state properties, but also data on excitation energies of giant resonances.",0506043v1 2006-03-23,Scalar-Meson - Baryon Coupling Constants in QCD Sum Rules,"The external-field QCD Sum Rules method is used to evaluate the coupling constants of the light-isoscalar scalar meson (``\sigma'' or \epsilon) to the \Lambda, \Sigma, and \Xi baryons. It is shown that these coupling constants as calculated from QCD Sum Rules are consistent with SU(3)-flavor relations, which leads to a determination of the F/(F+D) ratio of the scalar octet assuming ideal mixing: we find \alpha_s \equiv F/(F+D)=0.55. The coupling constants with SU(3) breaking effects are also discussed.",0603058v1 2007-03-28,The Friedrichs-Model with fermion-boson couplings II,"In this work we present a formal solution of the extended version of the Friedrichs Model. The Hamiltonian consists of discrete and continuum bosonic states, which are coupled to fermions. The simultaneous treatment of the couplings of the fermions with the discrete and continuous sectors of the bosonic degrees of freedom leads to a system of coupled equations, whose solutions are found by applying standard methods of representation of bound and resonant states.",0703091v1 1998-05-23,Optical microsphere resonators: optimal coupling to high-Q whispering gallery modes,"A general model is presented for coupling of high-$Q$ whispering-gallery modes in optical microsphere resonators with coupler devices possessing discrete and continuous spectrum of propagating modes. By contrast to conventional high-Q optical cavities, in microspheres independence of high intrinsic quality-factor and controllable parameters of coupling via evanescent field offer variety of regimes earlier available in RF devices. The theory is applied to the earlier-reported data on different types of couplers to microsphere resonators and complemented by experimental demonstration of enhanced coupling efficiency (about 80%) and variable loading regimes with Q>10^8 fused silica microspheres.",9805030v1 2004-05-03,On the role of coupling in mode selective excitation using ultrafast pulse shaping in stimulated Raman spectroscopy,"The coherence of two, coupled two-level systems, representing vibrational modes in a semiclassical model, is calculated in weak and strong fields for various coupling schemes and for different relative phases between initial state amplitudes. A relative phase equal to $\pi$ projects the system into a dark state. The selective excitation of one of the two, two-level systems is studied as a function of coupling strength and initial phases.",0405011v1 2004-05-13,The program for the transformation of atomic state functions from LS- to jj-coupled basis,"Here we present the program for the transformation of the expansions of the atomic state functions from LS- to jj-coupled bases. The program is a part of the coupling optimization package Laris and allows to transform the multiconfigurational expansions with the arbitrary number of open shells (including f-electrons) and to identify atomic levels and classify the atomic spectra by means of intermediate quantum numbers of LS- and jj-couplings.",0405061v1 2005-05-09,Bistable light detectors with nonlinear waveguide arrays,"Bistability induced by nonlinear Kerr effect in arrays of coupled waveguides is studied and shown to be a means to conceive light detectors that switch under excitation by a weak signal. The detector is obtained by coupling two single 1D waveguide to an array of coupled waveguides with adjusted indices and coupling. The process is understood by analytical description in the conservative and continuous case and illustrated by numerical simulations of the model with attenuation.",0505062v2 2005-06-08,Fluorescence measurements of expanding strongly-coupled neutral plasmas,"We report new detailed density profile measurements in expanding strongly-coupled neutral plasmas. Using laser-induced fluorescence techniques, we determine plasma densities in the range of 10^5 to 10^9/cm^3 with a time resolution limit as small as 7 ns. Strong-coupling in the plasma ions is inferred directly from the fluorescence signals. Evidence for strong-coupling at late times is presented, confirming a recent theoretical result.",0506069v2 2006-03-13,Mode coupling control in a resonant device: application to solid-state ring lasers,"A theoretical and experimental investigation of the effects of mode coupling in a resonant macro- scopic quantum device is achieved in the case of a ring laser. In particular, we show both analytically and experimentally that such a device can be used as a rotation sensor provided the effects of mode coupling are controlled, for example through the use of an additional coupling. A possible general- ization of this example to the case of another resonant macroscopic quantum device is discussed.",0603099v1 2002-09-14,Saturation of the production of quantum entanglement between weakly coupled mapping systems in strongly chaotic region,"The production of quantum entanglement between weakly coupled mapping systems, whose classical counterparts are both strongly chaotic, is investigated. In the weak coupling regime, it is shown that time correlation functions of the unperturbed systems determine the entanglement production. In particular, we elucidate that the increment of nonlinear parameter of coupled kicked tops does not accelerate the entanglement production in the strongly chaotic region. An approach to the dynamical inhibition of entanglement is suggested.",0209086v1 2003-01-18,Geometric Phase of electrons due to the Spin-rotation Coupling in Rotating C$_{60}$ Molecules,"The rapidly rotational motion of C$_{60}$ molecules provides us with an ingenious way to test Mashhoon's spin-rotation coupling. The spin-rotation coupling of electrons in the rotating C$_{60}$ molecule is considered in the present letter. It is shown that the intrinsic spin (gravitomagnetic moment) of the electron that can be coupled to the time-dependent rotating frequency of rotating frame of reference (C$_{60}$ molecule) results in a geometric phase, which may be measured through the electronic energy spectra of C$_{60}$ molecules.",0301094v3 2003-04-28,Quantum information processing using Josephson junctions coupled through cavities,"Josephson junctions have been shown to be a promising solid-state system for implementation of quantum computation. The significant two-qubit gates are generally realized by the capacitive coupling between the nearest neighbour qubits. We propose an effective Hamiltonian to describe charge qubits coupled through the cavity. We find that nontrivial two-qubit gates may be achieved by this coupling. The ability to interconvert localized charge qubits and flying qubits in the proposed scheme implies that quantum network can be constructed using this large scalable solid-state system.",0304173v2 2003-09-11,Anticrossings in Foerster Coupled Quantum Dots,"We consider two coupled generic quantum dots, each modelled by a simple potential which allows the derivation of an analytical expression for the inter-dot Foerster coupling, in the dipole-dipole approximation. We investigate the energy level behaviour of this coupled two-dot system under the influence of an external applied electric field and predict the presence of anticrossings in the optical spectra due to the Foerster interaction.",0309099v2 2003-11-20,Entanglement generated between a single atom and a laser pulse,"We quantify the entanglement generated between an atom and a laser pulse in free space. We find that the entanglement calculated using a simple closed-system Jaynes-Cummings Hamiltonian is in remarkable agreement with a full open-system calculation, even though the free-space geometry is far from the strong coupling regime of cavity QED. We explain this result using a simple model in which the atom couples weakly to the laser while coupling strongly to the vacuum. Additionally we place an upper bound on the total entanglement between the atom and all paraxial modes using a quantum trajectories unravelling. This upper bound provides a benchmark for atom-laser coupling.",0311135v1 2005-02-22,Minimal coupling method and the dissipative scalar field theory,"Quantum field theory of a damped vibrating string as the simplest dissipative scalar field investigated by its coupling with an infinit number of Klein-Gordon fields as the environment by introducing a minimal coupling method. Heisenberg equation containing a dissipative term proportional to velocity obtained for a special choice of coupling function and quantum dynamics for such a dissipative system investigated. Some kinematical relations calculated by tracing out the environment degrees of freedom. The rate of energy flowing between the system and it's environment obtained.",0502134v2 2005-02-25,Time Optimal Control of Coupled Qubits Under Non-Stationary Interactions,"In this article, we give a complete characterization of all the unitary transformations that can be synthesized in a given time for a system of coupled spin-1/2 in presence of general time varying coupling tensor. Our treatment is quite general and our results help to characterize the reachable set at all times for a class of bilinear control systems with time varying drift and unbounded control amplitude. These results are of fundamental interest in geometric control theory and have applications to control of coupled spins in solid state NMR spectroscopy.",0502173v2 2005-09-22,Exact solution of quantum dynamics of a cantilever coupling to a single trapped ultracold ion,"The quantum behavior of a precooled cantilever can be probed highly efficiently by coupling to a trapped ultracold ion, in which a fast cooling of the cantilever down to the ground vibrational state is possible. We solve the dynamics of the coupling system by a squeezed-state expansion technique, and can in principle obtain the exact solution of the time-evolution of the coupling system. Compared to the treatment under rotating-wave approximation, we can present a more accurate description of the quantum behavior of the cantilever.",0509160v2 2005-10-11,"Weak and strong coupling regimes, vacuum Rabi splitting and nonstandard resonances","For two discrete-level quantum systems in interaction, we follow the displacement in the complex plane of the eigen-energies of the compound system when the spectrum of one of the two systems becomes continuous. These new points are usually called resonances. This allows us to define and to calculate a critical value of the coupling constant which separates two well-known coupling regimes. We also give an example of these resonances for the hydrogen atom coupled to the continuum of the states of the transverse electromagnetic field in the vacuum. We justify that some resonances be neglected.",0510075v1 2006-03-28,Ultrafast Coherent Coupling of Atomic Hyperfine and Photon Frequency Qubits,"We demonstrate ultrafast coherent coupling between an atomic qubit stored in a single trapped cadmium ion and a photonic qubit represented by two resolved frequencies of a photon. Such ultrafast coupling is crucial for entangling networks of remotely-located trapped ions through photon interference, and is also a key component for realizing ultrafast quantum gates between Coulomb-coupled ions.",0603258v2 1997-01-31,Coupled Nonlinear Schrödinger equation and Toda equation (the Root of Integrability),"We consider the relation between the discrete coupled nonlinear Schr\""{o}dinger equation and Toda equation. Introducing complex times we can show the intergability of the discrete coupled nonlinear Schr\""{o}dinger equation. In the same way we can show the integrability in coupled case of dark and bright equations. Using this method we obtain several integrable equations.",9701022v2 1998-05-02,Analytical Study of the Julia Set of a Coupled Generalized Logistic Map,"A coupled system of two generalized logistic maps is studied. In particular influence of the coupling to the behaviour of the Julia set in two dimensional complex space is analyzed both analytically and numerically. It is proved analytically that the Julia set disappears from the complex plane uniformly as a parameter interpolates from the chaotic phase to the integrable phase, if the coupling strength satisfies a certain condition.",9805001v2 1999-07-02,New Integrable Coupled Nonlinear Schrodinger Equations,"Two types of integrable coupled nonlinear Schrodinger (NLS) equations are derived by using Zakharov-Shabat (ZS) dressing method.The Lax pairs for the coupled NLS equations are also investigated using the ZS dressing method. These give new types of the integrable coupled NLS equations with certain additional terms. Then, the exact solutions of the new types are obtained. We find that the solution of these new types do not always produce a soliton solution even they are the kind of the integrable NLS equations.",9907007v1 1995-07-07,Low-Field Phase Diagram of Layered Superconductors: The Role of Electromagnetic Coupling,"We determine the position and shape of the melting line in a layered superconductor taking the electromagnetic coupling between layers into account. In the limit of vanishing Josephson coupling we obtain a new generic reentrant low-field melting line. Finite Josephson coupling pushes the melting line to higher temperatures and fields and a new line shape $B_{{\rm m}} \propto (1-T/T_c)^{3/2}$ is found. We construct the low-field phase diagram including melting and decoupling lines and discuss various experiments in the light of our new results.",9507003v2 2007-04-21,Strong coupling limit/region of lattice QCD,"We study the phase diagram of quark matter and nuclear properties based on the strong coupling expansion of lattice QCD. Both of baryon and finite coupling correction are found to have effects to extend the hadron phase to a larger mu direction relative to Tc. In a chiral RMF model with logarithmic sigma potential derived in the strong coupling limit of lattice QCD, we can avoid the chiral collapse and normal and hypernuclei properties are well described.",0704.2823v1 2007-04-26,Coupling of phonons and spin waves in triangular antiferromagnet,"We investigate the influence of the spin-phonon coupling in the triangular antiferromagnet where the coupling is of the exchange-striction type. The magnon dispersion is shown to be modified significantly at wave vector (2pi,0) and its symmetry-related points, exhibiting a roton-like minimum and an eventual instability in the dispersion. Various correlation functions such as equal-time phonon correlation, spin-spin correlation, and local magnetization are calculated in the presence of the coupling.",0704.3510v2 2007-04-29,Effect of Decoherence on the Dynamics of Bose-Einstein Condensates in a Double-well Potential,"We study the dynamics of a Bose-Einstein condensate in a double-well potential in the mean-field approximation. Decoherence effects are considered by analyzing the couplings of the condensate to environments. Two kinds of coupling are taken into account. With the first kind of coupling dominated, the decoherence can enhance the self-trapping by increasing the damping of the oscillations in the dynamics, while the decoherence from the second kind of condensate-environment coupling leads to spoiling of the quantum tunneling and self-trapping.",0704.3823v1 2007-05-03,Leader-following coordination of multi-agent systems with coupling time delays,"In this paper, we consider a leader-following consensus problem of a group of autonomous agents with time-varying coupling delays. Two different cases of coupling topologies are investigated. At first, a necessary and sufficient condition is proved in the case when the interconnection topology is fixed and directed. Then a sufficient condition is proposed in the case when the coupling topology is switched and balanced. Numerical examples are also given to illustrate our results.",0705.0401v1 2007-05-28,$WZ$ Production at $eγ$ Colliders and Anomalous Quartic $WWZγ$ Coupling,"We investigate the constraints on the anomalous quartic $W^{+}W^{-}Z\gamma$ gauge boson coupling through the process $e^{-}\gamma\to \nu_{e}W^{-}Z$. Considering incoming beam polarizations and the longitudinal and transverse polarization states of the final W and Z boson we find 95% confidence level limits on the anomalous coupling parameter $a_{n}$ with an integrated luminosity of 500 $fb^{-1}$ and $\sqrt{s}$=0.5, 1 TeV energies. We show that initial beam and final state polarizations improve the sensitivity to the anomalous coupling by up to factors of 2 - 3.5 depending on the energy.",0705.4075v2 2007-06-08,Analytical calculation of the transition to complete phase synchronization in coupled oscillators,"Here we present a system of coupled phase oscillators with nearest neighbors coupling, which we study for different boundary conditions. We concentrate at the transition to total synchronization. We are able to develop exact solutions for the value of the coupling parameter when the system becomes completely synchronized, for the case of periodic boundary conditions as well as for an open chain with fixed ends. We compare the results with those calculated numerically.",0706.1250v2 2007-07-04,Input-output relations for a 3-port grating coupled Fabry-Perot cavity,"We analyze an optical 3-port reflection grating by means of a scattering matrix formalism. Amplitude and phase relations between the 3 ports, i.e. the 3 orders of diffraction are derived. Such a grating can be used as an all-reflective, low-loss coupler to Fabry-Perot cavities. We derive the input output relations of a 3-port grating coupled cavity and find distinct properties not present in 2-port coupled cavities. The cavity relations further reveal that the 3-port coupler can be designed such that the additional cavity port interferes destructively. In this case the all-reflective, low-loss, single-ended Fabry-Perot cavity becomes equivalent to a standard transmissive, 2-port coupled cavity.",0707.0625v1 2007-07-08,A Renormalization Group For Treating 2D Coupled Arrays of Continuum 1D Systems,"We study the spectrum of two dimensional coupled arrays of continuum one-dimensional systems by wedding a density matrix renormalization group procedure to a renormalization group improved truncated spectrum approach. To illustrate the approach we study the spectrum of large arrays of coupled quantum Ising chains. We demonstrate explicitly that the method can treat the various regimes of chains, in particular the three dimensional Ising ordering transition the chains undergo as a function of interchain coupling.",0707.1160v1 2007-07-20,Stress Tensor of Static Dipoles in strongly coupled $\cal{N}$=4 Gauge Theory,"In the context of the AdS/CFT correspondence we calculate the induced stress tensor of static dipoles (electric-electric and electric-magnetic) in a strongly coupled ${\cal N}=4$ SYM gauge theory, by solving the linearized Einstein equation with Maldecena string as a source. Analytic expressions are given for the far-field and a near-field close to one charge, and compared to what one has in weak coupling. The result can be compared to lattice results for QCD-like theories in a deconfined but strongly coupled regime.",0707.3135v2 2007-07-25,Self-Dual Yang-Mills Multiplet in Three Dimensions Coupled to Supergravity,"We couple a recently-established N=1 globally supersymmetric self-dual Yang-Mills multiplet in three dimensions to supergravity. This becomes possible due to our previous result on globally supersymmetric formulation based on a compensator multiplet. We further couple the self-dual vector to a supersymmetric sigma-model on the coset SO(8,n) / SO(8) X SO(n) via minimal couplings for an arbitrary gauged subgroup H_0 \subset SO(8) X SO(n). A corresponding superspace formulation is also presented.",0707.3653v1 2007-07-30,Bulk-edge coupling in the non-abelian $ν=5/2$ quantum Hall interferometer,"Recent schemes for experimentally probing non-abelian statistics in the quantum Hall effect are based on geometries where current-carrying quasiparticles flow along edges that encircle bulk quasiparticles, which are localized. Here we consider one such scheme, the Fabry-Perot interferometer, and analyze how its interference patterns are affected by a coupling that allows tunneling of neutral Majorana fermions between the bulk and edge. While at weak coupling this tunneling degrades the interference signal, we find that at strong coupling, the bulk quasiparticle becomes essentially absorbed by the edge and the intereference signal is fully restored.",0707.4474v1 2007-08-07,Enhance synchronizability via age-based coupling,"In this brief report, we study the synchronization of growing scale-free networks. An asymmetrical age-based coupling method is proposed with only one free parameter $\alpha$. Although the coupling matrix is asymmetric, our coupling method could guarantee that all the eigenvalues are non-negative reals. The eigneratio R will approach to 1 in the large limit of $\alpha$.",0708.0863v1 2007-08-27,Asymptotics of QCD traveling waves with fluctuations and running coupling effects,"Extending independently the Balitsky-Kovchegov (BK) equation to running coupling or to fluctuation effects due to Pomeron loops is known to lead in both cases to qualitative changes of the traveling-wave asymptotic solutions. In this paper we study the extension of the forward BK equation, including both running coupling and fluctuations effects, using the method developed for the fixed coupling case. We derive the exact asymptotic behavior of the probabilistic distribution of the saturation scale.",0708.3659v3 2007-09-04,Polarized Single Top Quark Production in eγCollision and Anomalous Wtb Couplings,"We investigate the potential of $e\gamma$ collisions to probe anomalous $Wtb$ couplings via the polarized single top quark production process $e^{+} \gamma \to t \bar{b} \bar{\nu_{e}}$. We find 95% confidence level limits on the anomalous coupling parameters $F_{2L}$ and $F_{2R}$ with an integrated luminosity of $500 fb^{-1}$ and $\sqrt{s}=0.5, 1$ and 1.5 TeV energies. The effects of top quark spin polarization on the anomalous $Wtb$ couplings are discussed. It is shown that polarization leads to a considerable improvement in the sensitivity limits.",0709.0365v2 2007-09-07,The Adiabatic Instability on Cosmology's Dark Side,"We consider theories with a nontrivial coupling between the matter and dark energy sectors. We describe a small scale instability that can occur in such models when the coupling is strong compared to gravity, generalizing and correcting earlier treatments. The instability is characterized by a negative sound speed squared of an effective coupled dark matter/dark energy fluid. Our results are general, and applicable to a wide class of coupled models and provide a powerful, redshift-dependent tool, complementary to other constraints, with which to rule many of them out. A detailed analysis and applications to a range of models are presented in a longer companion paper.",0709.1124v1 2007-09-26,Nonperturbative Instability of AdS_5 x S^5/Z_k,"We study the AdS/CFT correspondence with boundary conditions AdS_5 x S^5/Z_k, where the Z_k acts freely but breaks all supersymmetry. While there are closed string tachyons at small 't Hooft coupling, there are no tachyons at large coupling. Nevertheless, we show that there is a nonperturbative instability directly analogous to the decay of the Kaluza-Klein vacuum. We discuss the implications of this instability for the strongly coupled dual field theory, and compare with earlier studies of this theory at weak coupling.",0709.4262v2 2007-09-29,Coupled nanopillar waveguides: optical properties and applications,"In this paper we review basic properties of coupled periodic and aperiodic nanopillar waveguides. A coupled nanopillar waveguide consists of several rows of periodically or aperiodically placed dielectric rods (pillars). In such a waveguide, light confinement is due to the total internal reflection, while guided modes dispersion is strongly affected by the waveguide structure. We present a systematic analysis of the optical properties of coupled nanopillar waveguides and discuss their possible applications for integrated optics.",0710.0054v1 2007-09-29,Elliptic functions and efficient control of Ising spin chains with unequal couplings,"In this article, we study optimal control of dynamics in a linear chain of three spin 1/2, weakly coupled with unequal Ising couplings. We address the problem of time-optimal synthesis of multiple spin quantum coherences. We derive time-optimal pulse sequence for creating a desired spin order by computing geodesics on a sphere under a special metric. The solution to the geodesic equation is related to the nonlinear oscillator equation and the minimum time to create multiple spin order can be expressed in terms of an elliptic integral. These techniques are used for efficient creation of multiple spin coherences in Ising spin-chains with unequal couplings.",0710.0075v1 2007-10-04,Thermodynamics of statistically interacting quantum gas in D dimensions,"We present the exact thermodynamics (isochores, isotherms, isobars, response functions) of a statistically interacting quantum gas in D dimensions. The results in D=1 are those of the thermodynamic Bethe ansatz for the nonlinear Schroedinger model, a gas with repulsive two-body contact potential. In all dimensions the ideal boson and fermion gases are recovered in the weak-coupling and strong-coupling limits, respectively. For all nonzero couplings ideal fermion gas behavior emerges for D>>1 and, in the limit D->infinity, a phase transition occurs at T>0. Significant deviations from ideal quantum gas behavior are found for intermediate coupling and finite D.",0710.1031v1 2007-10-05,Renormalization group flow of quartic perturbations in graphene: Strong coupling and large-N limits,"We explore the renormalization group flow of quartic perturbations in the low-energy theory of graphene, in the strong Coulomb coupling and large-N limits, where N is the number of fermion flavors. We compute the anomalous dimensions of the quartic couplings u up to next-to-leading order in 1/N and find both relevant and irrelevant directions in the space of quartic couplings. We discuss possible phase diagrams and relevance for the physics of graphene.",0710.1315v2 2007-10-08,Effective Coupling Constant in Renormalization Group for the Quantum Electrodynamics,"Effective coupling constant in quantum electrodynamics is investigated. A pole appears in the effective coupling constant for the space-like momentum if it is calculated by perturbation. The pole can be eliminated by the analytic regularization. For QED the effective coupling constant is written in terms of the scale parameter, $\Lambda$, having the dimension of mass as in the case of QCD. $\Lambda$ is determined by comparing with the experimental data. The calculated result agrees with experiment with $\Lambda\approx 1.64\times 10^{47}$ GeV; it is very large but much smaller than the mass scale of Landau ghost.",0710.1457v1 2007-10-15,Intersubband spin-orbit coupling and spin splitting in symmetric quantum wells,"In semiconductors with inversion asymmetry, spin-orbit coupling gives rise to the well-known Dresselhaus and Rashba effects. If one considers quantum wells with two or more conduction subbands, an additional, intersubband-induced spin-orbit term appears whose strength is comparable to the Rashba coupling, and which remains finite for symmetric structures. We show that the conduction band spin splitting due to this intersubband spin-orbit coupling term is negligible for typical III-V quantum wells.",0710.2866v1 2007-10-18,Entanglement between charge qubits induced by a common dissipative environment,"We study entanglement generation between two charge qubits due to the strong coupling with a common bosonic environment (Ohmic bath). The coupling to the boson bath is a source of both quantum noise (leading to decoherence) and an indirect interaction between qubits. As a result, two effects compete as a function of the coupling strength with the bath: entanglement generation and charge localization induced by the bath. These two competing effects lead to a non-monotonic behavior of the concurrence as a function of the coupling strength with the bath. As an application, we present results for charge qubits based on double quantum dots.",0710.3576v1 2007-10-19,Evolution of coherence between the Jaynes - Cummings Eigenstates in the presence of repeated occupancy measurements: The case of resonant coupling,"A two level system resonantly coupled to a single mode cavity field and subject to ground state occupancy measurement like interaction is considered. For this situation, the solution to the Lindblad master equation for the density matrix is obtained with respect to the Jaynes Cummings eigenstate representation. It is seen that, the rate of decoherence of the superposition of the Jaynes Cummings eigenstates increases monotonically with the increase in the occupancy measurement coupling up to a certain critical value (already reported in the literature in a different context), whereas the rate decreases with the increase in the measurement coupling beyond the same critical value.",0710.3662v1 2007-10-23,Tan(beta) enhanced Yukawa couplings for supersymmetric Higgs singlets at one loop,"Extensions of the MSSM generically feature gauge singlet Higgs bosons. These singlet Higgs bosons have tan(beta)-enhanced Yukawa couplings to down-type quarks and leptons at the one-loop level. We present an effective Lagrangian incorporating these Yukawa couplings and use it to study their effect on singlet Higgs boson phenomenology within both the mnSSM and NMSSM. It is found that the loop-induced couplings represent an appreciable effect for the singlet pseudoscalar in particular, and may dominate its decay modes in some regions of parameter space.",0710.4281v1 2007-10-25,Classical Renormalization of Codimension-two Brane Couplings,"The curvature on codimension-two and higher branes is not regular for arbitrary matter sources. Nevertheless, the low-energy theory for an observer on such a brane should be well-defined and independent to any regularization procedure. This is achieved via appropriate classical renormalization of the brane couplings, and leads to a natural hierarchy between standard model couplings and couplings to gravity.",0710.4598v1 2007-11-21,Josephson Effect between Conventional and Rashba Superconductors,"We study the Josephson effect between a conventional s-wave superconductor and a non-centrosymmetric superconductor with Rashba spin-orbit coupling. Rashba spin-orbit coupling affects the Josephson pair tunneling in a characteristic way. The Josephson coupling can be decomposed into two parts, a `spin-singlet-like' and a `spin-triplet-like' component. The latter component can lead to shift of the Josephson phase by \pi relative to the former coupling. This has important implications on interference effects and may explain some recent experimental results for the Al/CePt3Si junction.",0711.3241v2 2007-11-30,Non-local dilaton coupling to dark matter: cosmic acceleration and pressure backreaction,"A model of non-local dilaton interactions, motivated by string duality symmetries, is applied to a scenario of ""coupled quintessence"" in which the dilaton dark energy is non-locally coupled to the dark-matter sources. It is shown that the non-local effects tend to generate a backreaction which -- for strong enough coupling -- can automatically compensate the acceleration due to the negative pressure of the dilaton potential, thus asymptotically restoring the standard (dust-dominated) decelerated regime. This result is illustrated by analytical computations and numerical examples.",0711.5022v1 2007-12-11,Valley interference effects on a donor electron close to a Si/SiO2 interface,"We analyze the effects of valley interference on the quantum control and manipulation of an electron bound to a donor close to a Si/SiO2 interface as a function of the valley-orbit coupling at the interface. We find that, for finite valley-orbit coupling, the tunneling times involved in shuttling the electron between the donor and the interface oscillate with the interface/donor distance in much the same way as the exchange coupling oscillates with the interdonor distance. These oscillations disappear when the ground state at the interface is degenerate (corresponding to zero valley-orbit coupling).",0712.1823v1 2008-01-11,Generation of d-wave coupling in the two-dimensional Hubbard model from functional renormalization,"Within the two-dimensional repulsive t-t'-Hubbard model, an attractive coupling in the d-wave pairing channel is induced by antiferromagnetic fluctuations. We investigate this coupling using functional renormalization group equations. The momentum dependent d-wave coupling can be bosonized by the use of scale dependent field transformations. We propose an effective coarse grained model for the Hubbard model which is based on the exchange of antiferromagnetic and d-wave collective bosons.",0801.1773v2 2008-01-29,Microwave-induced coupling of superconducting qubits,"We investigate the quantum dynamics of a system of two coupled superconducting qubits under microwave irradiation. We find that, with the qubits operated at the charge co-degeneracy point, the quantum evolution of the system can be described by a new effective Hamiltonian which has the form of two coupled qubits with tunable coupling between them. This Hamiltonian can be used for experimental tests on macroscopic entanglement and for implementing quantum gates.",0801.4541v2 2008-02-03,Anomalous Higgs couplings in egamma collision with initial beam and final state polarizations,"We investigate the constraints on the anomalous WWH couplings through the process $e^{-}\gamma \to \nu_{e} W^{-} H$. Considering incoming beam polarizations and the longitudinal and transverse polarization states of the final W boson, we find 95% confidence level limits on the anomalous coupling parameters with an integrated luminosity of 500 $fb^{-1}$ and $\sqrt{s}$= 0.5 and 1 TeV energy. We show that initial beam and final state polarizations highly improve the sensitivity limits of the anomalous coupling parameters $b_{W}$ and $\beta_{W}$.",0802.0293v2 2008-02-08,Noise-dependent stability of the synchronized state in a coupled system of active rotators,"We consider a Kuramoto model for the dynamics of an excitable system consisting of two coupled active rotators. Depending on both the coupling strength and the noise, the two rotators can be in a synchronized or desynchronized state. The synchronized state of the system is most stable for intermediate noise intensity in the sense that the coupling strength required to desynchronize the system is maximal at this noise level. We evaluate the phase boundary between synchronized and desynchronized states through numerical and analytical calculations.",0802.1105v1 2008-02-08,Immirzi parameter and fermions with non-minimal coupling,"We clarify the role played by the Immirzi parameter in classical gravity coupled to fermions. Considering the general non-minimal coupling, we show that, although the torsion depends explicitly on the Immirzi parameter, in a suitable parametrization the effective action obtained by integrating out the spin-connection is independent of it. Thus the Immirzi parameter is not detectable in classical theory even after coupling of fermions.",0802.1221v2 2008-02-12,Dynamical Coupling Between Ferromagnets Due to Spin Transfer Torque,"We use a combination of analytic calculations and numerical simulations to demonstrate that electrical current flowing through a magnetic bilayer induces dynamical coupling between the layers. The coupling originates from the dependence of the spin transfer torque exerted on the layers on the relative orientations of their magnetic moments. We demonstrate that such coupling modifies the behaviors of both layers, significantly affecting the the stability of the current-induced dynamical regimes and the efficiency of current-induced magnetic reversal.",0802.1560v1 2008-02-12,Coupling of Electronic and Motional Dynamics in a Cold Atom Optical Lattice,"We study the coupling of internal electronic excitations to vibrational modes of the external motion of ultracold atoms in an optical lattice. For different ground and excited state potentials the on-site coupling of excitations and vibrations term renormalizes the effective electronic transition energy, which appears e.g. in clock transitions. In addition in the Mott state with filling factor one, the dipole-dipole coupling between neighbouring sites includes emission and absorption of vibrational quanta. Such processes create a significant mechanism for excitation of vibrations leading to motional heating of the lattice atoms by resonant light interaction. We calculate estimates of the corresponding parameters from a perturbation expansion in small atomic displacements.",0802.1618v1 2008-02-12,Strong coupling between a metallic nanoparticle and a single molecule,"We theoretically investigate strong coupling between a single molecule and a single metallic nanoparticle. A theory suited for the quantum-mechanical description of surface plasmon polaritons (SPPs) is developed. The coupling between these SPPs and a single molecule, and the modified molecular dynamics in presence of the nanoparticle are described within a combined Drude and boundary-element-method approach. Our results show that strong coupling is possible for single molecules and metallic nanoparticles, and can be observed in fluorescence spectroscopy through the splitting of emission peaks.",0802.1630v1 2008-02-20,Effect of top quark spin on the unparticle couplings in γγ\to t\bar{t},"We investigate the potential of $\gamma\gamma$ collisions to probe scalar unparticle couplings via top-antitop quark pair production. We find 95% confidence level limits on the unparticle couplings with an integrated luminosity of $500 fb^{-1}$ and $\sqrt{s}=1$ TeV energy. We investigate the effect of top quark spin polarization on the unparticle couplings. It is shown that spin polarization of the top quark leads to a significant improvement in the sensitivity limits.",0802.2818v3 2008-02-20,Bang-Bang control of a qubit coupled to a quantum critical spin bath,"We analytically and numerically study the effects of pulsed control on the decoherence of a qubit coupled to a quantum spin bath. When the environment is critical, decoherence is faster and we show that the control is relatively more effective. Two coupling models are investigated, namely a qubit coupled to a bath via a single link and a spin star model, yielding results that are similar and consistent.",0802.2859v2 2008-02-28,Coupling efficiency for phase locking of a spin transfer oscillator to a microwave current,"The phase locking behavior of spin transfer nano-oscillators (STNOs) to an external microwave signal is experimentally studied as a function of the STNO intrinsic parameters. We extract the coupling strength from our data using the derived phase dynamics of a forced STNO. The predicted trends on the coupling strength for phase locking as a function of intrinsic features of the oscillators i.e. power, linewidth, agility in current, are central to optimize the emitted power in arrays of mutually coupled STNOs.",0802.4162v3 2008-03-17,Gluon scattering in N=4 super-Yang-Mills theory from weak to strong coupling,"I describe some recent developments in the understanding of gluon scattering amplitudes in N=4 super-Yang-Mills theory in the large-N_c limit. These amplitudes can be computed to high orders in the weak coupling expansion, and also now at strong coupling using the AdS/CFT correspondence. They hold the promise of being solvable to all orders in the gauge coupling, with the help of techniques based on integrability. They are intimately related to expectation values for polygonal Wilson loops composed of light-like segments.",0803.2475v1 2008-04-10,Solitary waves for linearly coupled nonlinear Schrodinger equations with inhomogeneous coefficients,"Motivated by the study of matter waves in Bose-Einstein condensates and coupled nonlinear optical systems, we study a system of two coupled nonlinear Schrodinger equations with inhomogeneous parameters, including a linear coupling. For that system we prove the existence of two different kinds of homoclinic solutions to the origin describing solitary waves of physical relevance. We use a Krasnoselskii fixed point theorem together with a suitable compactness criterion.",0804.1785v2 2008-04-15,Entangled photon pairs produced by a quantum dot strongly coupled to a microcavity,"We show theoretically that entangled photon pairs can be produced on demand through the biexciton decay of a quantum dot strongly coupled to the modes of a photonic crystal. The strong coupling allows to tune the energy of the mixed exciton-photon (polariton) eigenmodes, and to overcome the natural splitting existing between the exciton states coupled with different linear polarizations of light. Polariton states are moreover well protected against dephasing due to their lifetime ten to hundred times shorter than that of a bare exciton. Our analysis shows that the scheme proposed can be achievable with the present technology.",0804.2396v1 2008-04-29,Nonlinear evolution equations for degenerate transverse waves in anisotropic elastic solids,"Transverse elastic waves behave differently in nonlinear isotropic and anisotropic media. Quadratically nonlinear coupling in the evolution equations for wave amplitudes is not possible in isotropic solids, but such a coupling may occur for certain directions in anisotropic materials. We identify the expression responsible for the coupling and we derive coupled canonical evolution equations for transverse wave amplitudes in the case of two-fold and three-fold symmetry acoustic axes. We illustrate our considerations by examples for a cubic crystal.",0804.4695v1 2008-05-15,Parametrization of the QCD coupling in the Evolution Equations,"We examine the parametrization of the QCD coupling in the Evolution Equations, including DGLAP. Our conclusion is that the well-known parametrization, where the argument of the coupling is k^2_{\perp}/\beta or just k^2_{\perp}, stands only if the lowest integration limit in the transverse momentum space (the starting point mu^2 of the Q^2 -evolution) obeys the relation mu >> Lambda_{QCD} \exp {(\pi/2)}, otherwise the coupling should be replaced by the more complicated expression presented in Eq. (37).",0805.2278v1 2008-05-21,Dynamical Regularization in Scalefree-trees of Coupled 2D Chaotic Maps,"The dynamics of coupled 2D chaotic maps with time-delay on a scalefree-tree is studied, with different types of the collective behaviors already been reported for various values of coupling strength [1]. In this work we focus on the dynamics' time-evolution at the coupling strength of the stability threshold and examine the properties of the regularization process. The time-scales involved in the appearance of the regular state and the periodic state are determined. We find unexpected regularity in the the system's final steady state: all the period values turn out to be integer multiples of one among given numbers. Moreover, the period value distribution follows a power-law with a slope of -2.24.",0805.3311v1 2008-05-29,Driven transverse shear waves in a strongly coupled dusty plasma,"The linear dispersion properties of transverse shear waves in a strongly coupled dusty plasma are experimentally studied by exciting them in a controlled manner with a variable frequency external source. The dusty plasma is maintained in the strongly coupled fluid regime with (1 < Gamma << Gamma_c) where Gamma is the Coulomb coupling parameter and Gamma_c is the crystallization limit. A dispersion relation for the transverse waves is experimentally obtained over a frequency range of 0.1 Hz to 2 Hz and found to show good agreement with viscoelastic theoretical results.",0805.4514v2 2008-06-02,Electron and phonon correlations in systems of one-dimensional electrons coupled to phonons,"Electron and phonon correlations in systems of one-dimensional electrons coupled to phonons are studied at low temperatures by emphasizing on the effect of electron-phonon backward scattering. It is found that the $2k_F$-wave components of the electron density and phonon displacement field share the same correlations. Both correlations are quasi-long-ranged for a single conducting chain coupled to one-dimensional or three-dimensional phonons, and they are long-ranged for repulsive electron-electron interactions for a three-dimensional array of parallel one-dimensional conducting chains coupled to three-dimensional phonons.",0806.0310v3 2008-06-03,Spin-Orbit Coupling in an f-electron Tight-Binding Model,"We extend a tight-binding method to include the effects of spin-orbit coupling, and apply it to the study of the electronic properties of the actinide elements Th, U, and Pu. These tight-binding parameters are determined for the fcc crystal structure using the equivalent equilibrium volumes. In terms of the single particle energies and the electronic density of states, the overall quality of the tight-binding representation is excellent and of the same quality as without spin-orbit coupling. The values of the optimized tight-binding spin-orbit coupling parameters are comparable to those determined from purely atomic calculations.",0806.0420v1 2008-06-04,Coupling and Level Repulsion in the Localized Regime: From Isolated to Quasi-Extended Modes,"We study the interaction of Anderson localized states in an open 1D random system by varying the internal structure of the sample. As the frequencies of two states come close, they are transformed into multiply-peaked quasi-extended modes. Level repulsion is observed experimentally and explained within a model of coupled resonators. The spectral and spatial evolution of the coupled modes is described in terms of the coupling coefficient and Q-factors of resonators.",0806.0704v2 2008-06-20,Identical chaotic synchronization and bidirectional message transmission in incoherently coupled semiconductor laser diodes,"A chaos-based communication scheme allowing simultaneous bidirectional message transmission (Opt. Lett. 32, 403, 2007) is investigated numerically. Incoherent feedback and coupling case is analyzed, which is expected in real long-distance optical communication systems. It is shown that identical synchronization of chaotic laser waveforms and bidirectional message transmission are possible as in the coherent coupling case. However, the chaotic regime at incoherent feedback and coupling is quite different. It is regular destabilized relaxation oscillations with the chaotic envelope. Such dynamics leads to restriction of the transmitting signal bit rate by a portion of relaxation oscillations frequency.",0806.3375v1 2008-06-24,Decoherence of two qubits coupled with one-mode cavity without rotating-wave approximation,"The decoherence of two qubits, coupled with one-mode cavity separately, has been investigated exactly. The results show that, for the resonant case, the decoherence behavior of system is similar to Markovian case when the coupling strength is weak, while the concurrence vanishes in finite time and might recover fractional initial entanglement before it permanently vanishes when the coupling strength is strong. And for detuning case, the entanglement could periodically recover after a period of time from its disappearance. These results are quite different from that of system subjected to Jaynes-Cummings model.",0806.3884v2 2008-08-06,Anomalous WWH couplings in gamma gamma collision with initial beams and final state polarizations,"The constraints on anomalous Higgs boson couplings are investigated through the process $\gamma\gamma \to W^{+}W^{-}H$. Considering the longitudinal and transverse polarization states of the final $W^{+}$ and $W^{-}$ bosons and incoming beam polarizations, we find 95% confidence level limits on the anomalous coupling parameters $\Delta a_{W}$, $b_{W}$ and $\beta_{W}$ with an integrated luminosity of 500 $fb^{-1}$ and $\sqrt{s}$=0.5, 1 TeV energies. We show that initial beam and final state polarizations lead to a significant improvement on the sensitivity limits of the anomalous coupling parameters $b_{W}$ and $\beta_{W}$.",0808.0842v2 2008-09-25,Coherent operation of superconducting flux qubits,"We study the quantum operation of coupled superconducting flux qubits under a microwave irradiation. The flux qubits can be described as magnetic dipole moments in the limit of weak microwave field amplitude consistent with usual experimental situations. With the Hamiltonian for coupled qubits under a microwave field, we show that a strong coupling enables to realize the high performance controlled-NOT gate operation. For practical quantum computing we analyze the effect of microwave on switching function of phase-coupled qubits.",0809.4341v3 2008-09-25,Bias dependence of magnetic exchange interactions: application to interlayer exchange coupling in spin valves,"We study how a bias voltage changes magnetic exchange interactions. We derive a general expression for magnetic exchange interactions for systems coupled to reservoirs under a bias potential, and apply it to spin valves. We find that for metallic systems, the interlayer exchange coupling shows a weak, oscillatory dependence on the bias potential. For tunneling systems, we find a quadratic dependence on the bias potential, and derive an approximate expression for this bias dependence for a toy model. We give general conditions for when the interlayer exchange coupling is a quadratic function of bias potential.",0809.4451v1 2008-09-25,Ground state cooling of nanomechanical resonator via parametric linear coupling,"We present a ground state cooling scheme for a nanomechanical resonator linearly coupled with a LC oscillator. The linear coupling, when periodically modulated at red detuning, up-converts the low-frequency nanomechanical mode to the high-frequency LC oscillator mode and generates backaction force that can cool the resonator to its ground state in the resolved-sideband regime. We also study the effect of the quantum backaction noise on the cooling due to the counter rotating term in the linear coupling. The scheme can be compared with laser cooling for the atomic systems and can be realized in superconducting circuits.",0809.4459v2 2008-10-01,Higher neutrino mass allowed if Cold Dark Matter and Dark Energy are coupled,"Cosmological limits on neutrino masses are softened, by more than a factor 2, if Cold Dark Matter (CDM) and Dark Energy (DE) are coupled. In turn, a neutrino mass yielding $\Omega_\nu$ up to $\sim0.20$ allows coupling levels $\beta \simeq 0.15, $ or more, already easing the coincidence problem. The coupling, in fact, displaces both $P(k)$ and $C_l$ spectra in a fashion opposite to neutrino mass. Estimates are obtained through a Fisher--matrix technique.",0810.0127v2 2008-10-16,Synchronization of Coupled Anizochronous Auto-Oscillating Systems,"The particular properties of synchronization are discussed for coupled auto-oscillating systems, which are characterized by non-quadratic law of potential dependence on the coordinate. In particular, structure of the parameter plane (frequency mismatch - coupling value) is considered for coupled van der Pol - Duffing oscillators. The arrangement of synchronization tongues and the particular properties of their internal structure in the parameter space are revealed. The features of attractors in the phase space are discussed.",0810.2863v1 2008-10-30,Berry Phase in a Single Quantum Dot with Spin-Orbit Interaction,"Berry phase in a single quantum dot with Rashba spin-orbit coupling is investigated theoretically. Berry phases as functions of magnetic field strength, dot size, spin-orbit coupling and photon-spin coupling constants are evaluated. It is shown that the Berry phase will alter dramatically from 0 to $2\pi$ as the magnetic field strength increases. The threshold of magnetic field depends on the dot size and the spin-orbit coupling constant.",0810.5405v1 2008-11-20,Gravitational correction to SU(5) gauge coupling unification,"The gravitational corrections to the gauge coupling constants of abelian and non-abelian gauge theories has been shown to diverge quadratically. Since this result will have interesting consequences, this has been analyzed by several authors from different approaches. We propose to discuss this issue from a phenomenological approach. We analyze the SU(5) gauge coupling unification and argue that the gravitational corrections to gauge coupling constants may not vanish when higher dimensional non-renormalizable terms are included in the problem.",0811.3307v2 2008-11-25,Emergence of zero-lag synchronization in generic mutually coupled chaotic systems,"Zero-lag synchronization (ZLS) is achieved in a very restricted mutually coupled chaotic systems, where the delays of the self-coupling and the mutual coupling are identical or fulfil some restricted ratios. Using a set of multiple self-feedbacks we demonstrate both analytically and numerically that ZLS is achieved for a wide range of mutual delays. It indicates that ZLS can be achieved without the knowledge of the mutual distance between the communicating partners and has an important implication in the possible use of ZLS in communications networks as well as in the understanding of the emergence of such synchronization in the neuronal activities.",0811.4066v1 2008-12-01,Gauge Coupling Unification in F-theory GUT Models,"We investigate gauge coupling unification for F-theory respectively Type IIB orientifold constructions of SU(5) GUT theories with gauge symmetry breaking via non-trivial hypercharge flux. This flux has the non-trivial effect that it splits the values of the three MSSM gauge couplings at the string scale, thus potentially spoiling the celebrated one-loop gauge coupling unification. It is shown how F-theory can evade this problem in a natural way.",0812.0248v3 2008-12-04,Transition to complete synchronization in phase coupled oscillators with nearest neighbours coupling,"We investigate synchronization in a Kuramoto-like model with nearest neighbour coupling. Upon analyzing the behaviour of individual oscillators at the onset of complete synchronization, we show that the time interval between bursts in the time dependence of the frequencies of the oscillators exhibits universal scaling and blows up at the critical coupling strength. We also bring out a key mechanism that leads to phase locking. Finally, we deduce forms for the phases and frequencies at the onset of complete synchronization.",0812.0998v1 2009-01-04,Coupling between a dark and a bright eigenmode in a terahertz metamaterial,"Terahertz time domain spectroscopy and rigorous simulations are used to probe the coupling between a dark and a bright plasmonic eigenmode in a metamaterial with broken symmetry. The metamaterial consists of two closely spaced split ring resonators that have their gaps in non-identical positions within the ring. For normal incidence and a fixed polarization both lowest order eigenmodes of the split ring resonators can be excited; although one of them has to be regarded as dark since coupling is prohibited because of symmetry constraints. Emphasis in this work is put on a systematic evaluation of the coupling effects depending on a spectral tuning of both resonances.",0901.0365v1 2009-01-17,Electronic interferometer capacitively coupled to a quantum dot,"We theoretically study electron interference in a ballistic electronic interferometer capacitively coupled to a quantum dot. The visibility of the interference is reduced when the dot has degenerate ground states with different excess charges. The degree of the reduction depends on system parameters such as the strength of the capacitive coupling, and the dependence is analyzed in the regime where the dwell time of electrons in the dot is much longer than the electron flight time through the interferometry region coupled to the dot. The result is consistent with recent experimental data.",0901.2626v2 2009-01-27,Weakly coupled discretized gravity,"We consider discretized gravity in 4+2 dimensions compactified on a disk of constant negative curvature. The curvature of the disk avoids the presence of dangerous ultra-light scalar modes but comes also along with a high multiplicity of states potentially jeopardizing a good strong-coupling behavior of the discretized theory. We demonstrate that for Standard Model matter propagating on the five-dimensional boundary submanifold of the disk, the strong coupling scale, as seen by an observer, can be parametrically larger than the local Planck scale. As a consequence, we obtain a description of weakly coupled discretized gravity on the boundary that can be compared with the continuum theory all the way up to the effective five-dimensional Planck scale.",0901.4304v1 2009-01-31,An improved lattice measurement of the critical coupling in phi^4_2 theory,"We use Monte Carlo simulations to obtain an improved lattice measurement of the critical coupling constant [lambda / mu^2]_crit for the continuum (1 + 1)-dimensional (lambda / 4) phi^4 theory. We find that the critical coupling constant depends logarithmically on the lattice coupling, resulting in a continuum value of [lambda / mu^2]_crit = 10.8(1), in considerable disagreement with the previously reported [lambda / mu^2]_crit = 10.26(8). Although this logarithmic behavior was not observed in earlier lattice studies, it is consistent with them, and expected analytically.",0902.0045v1 2009-02-03,Asynchronous response of coupled pacemaker neurons,"We study a network model of two conductance-based pacemaker neurons of differing natural frequency, coupled with either mutual excitation or inhibition, and receiving shared random inhibitory synaptic input. The networks may phase-lock spike-to-spike for strong mutual coupling. But the shared input can desynchronize the locked spike-pairs by selectively eliminating the lagging spike or modulating its timing with respect to the leading spike depending on their separation time window. Such loss of synchrony is also found in a large network of sparsely coupled heterogeneous spiking neurons receiving shared input.",0902.0602v1 2009-02-19,Impurity induced spin-orbit coupling in graphene,"We study the effect of impurities in inducing spin-orbit coupling in graphene. We show that the sp3 distortion induced by an impurity can lead to a large increase in the spin-orbit coupling with a value comparable to the one found in diamond and other zinc-blende semiconductors. The spin-flip scattering produced by the impurity leads to spin scattering lengths of the order found in recent experiments. Our results indicate that the spin-orbit coupling can be controlled via the impurity coverage.",0902.3244v1 2009-03-05,Modification of spin mixing of spinor BEC by cavity QED coupling,"Dressed states of spinor Bose-Einstein condensates of spin-1 atoms coupling with optical cavity modes with far off resonance frequency are investigated. The exact solution of time evolution of population of spin component is derived, and the numerical result shows that the evolution is different from spin mixing without the coupling. Due to the coupling with the atoms, the photon state also evolute to different optical cavity modes.",0903.0998v1 2009-03-23,Higher Order Couplings in Magnetized Brane Models,"We compute three-point and higher order couplings in magnetized brane models. We show that higher order couplings are written as products of three-point couplings. This behavior is the same as higher order amplitudes by conformal field theory calculations e.g. in intersecting D-brane models.",0903.3800v2 2009-03-30,Weakly coupled bound states of Pauli operators,"We consider the two-dimensional Pauli operator perturbed by a weakly coupled, attractive potential. We show that besides the eigenvalues arising from the Aharonov-Casher zero modes there are two or one (depending on whether the flux of the magnetic field is integer or not) additional eigenvalues for arbitrarily small coupling and we calculate their asymptotics in the weak coupling limit.",0903.5333v1 2009-04-08,On the gauge coupling unification,"We consider a quark-lepton symmetry model of unification of the strong and electromagnetic interactions. The model has the gauge group $SU(4)\times U(1)_{Y}$ and the minimal Higgs structure consisting of one complex quartet of scalar particles. The spontaneous breakdown of the gauge group to $SU(3)_{c}\times U(1)_{em}$ due to nonzero vacuum expectation value of the Higgs quartet provides the simplest realization of the Higgs mechanism which generates masses for gauge bosons, and masses to quarks and leptons. Using the embedding of the gauge group to SU(5), we study the evolution of coupling constants and find a connection of the couplings with the gauge couplings of the standard model.",0904.1324v1 2009-04-10,Single bipolaronic Transition in Jahn-Teller Model,"We investigate the bipolaronic crossover and the pairing transition for a two-orbital model with Jahn-Teller coupling to a two-fold degenerate phonon mode. The evolution from weak to strong coupling is reminiscent of the behavior of the single-band Holstein model: The polaron crossover in which the electrons and phonons become strongly entangled occurs for a weaker coupling than the binding of bipolarons, which gives rise to a metal-insulator transition. Interestingly, a single bipolaronic transition takes place also when the two bands have significantly different bandwidths, as opposed to the case of repulsive Hubbard-like interactions for which an orbital-selective Mott transition has been reported. This behavior is related to the inter-orbital nature of the Jahn-Teller coupling.",0904.1711v1 2009-04-26,Bouncing Universe with a Nonminimally Coupled Scalar Field on a Moving Domain Wall,"We study dynamics of a dark energy component nonminimally coupled to gravity on a moving domain wall. We use this setup to explain late-time accelerated expansion and crossing of the phantom divide line by the equation of state parameter of this non-minimally coupled dark energy component. By analyzing parameter space of the model, we show that this model accounts for accelerated expansion and crossing of the phantom divide line with a suitable fine-tuning of the nonminimal coupling. Then we study the issue of bouncing solutions in this framework.",0904.4029v1 2009-04-28,Scalar dark matter-Higgs coupling in the case of electroweak symmetry breaking driven by unparticle,"We study the possible annihilation cross section of scalar dark matter and its coupling \lambda_D to the standard model Higgs in the case of the electroweak symmetry breaking driven by unparticle. Here the annihilation process occurs with the help of three intermediate scalars which appear after the mixing. By respecting the annihilation rate which is compatible with the current relic density we predict the tree level coupling \lambda_D. We observe that the unparticle scaling d_u plays a considerable role on the annihilation process and, therefore, on the coupling \lambda_D.",0904.4369v1 2009-05-04,Berry Phase Coupling and the Cuprate Neutron Scattering Resonance,"We examine the influence of coupling between particle-hole and particle-particle spin fluctuations on the inelastic neutron scattering resonance (INSR) in cuprate superconductors in both weak and strong interaction limits. For weak-interactions in the particle-hole channel, we find that the interchannel coupling can eliminate the resonance. For strong interactions which drive the system close to a $\bm{Q}=(\pi,\pi)$ magnetic instablity, the resonance frequency always approaches zero but its value is influenced by the interchannel coupling. We comment on constraints imposed on cuprate physics by the INSR phenomenology, and a comparison between the cuprates and the newly-discovered iron pnictide superconductors is discussed.",0905.0464v1 2009-05-05,Transport through a band insulator with Rashba spin-orbit coupling: metal-insulator transition and spin-filtering effects,"We calculate the current-voltage characteristic of a one-dimensional band insulator with magnetic field and Rashba spin-orbit coupling which is connected to nonmagnetic leads. Without spin-orbit coupling we find a complete spin-filtering effect, meaning that the electric transport occurs in one spin channel only. For a large magnetic field which closes the band gap, we show that spin-orbit coupling leads to a transition from metallic to insulating behavior. The oscillations of the different spin-components of the current with the length of the transport channel are studied as well.",0905.0611v1 2009-05-12,Globally clustered chimera states in delay--coupled populations,"We have identified the existence of globally clustered chimera states in delay coupled oscillator populations and find that these states can breathe periodically, aperiodically and become unstable depending upon the value of coupling delay. We also find that the coupling delay induces frequency suppression in the desynchronized group. We provide numerical evidence and theoretical explanations for the above results and discuss possible applications of the observed phenomena.",0905.1797v1 2009-05-12,Pauli Spin Blockade in the Presence of Strong Spin-Orbit Coupling,"We study electron transport in a double quantum dot in the Pauli spin blockade regime, in the presence of strong spin-orbit coupling. The effect of spin-orbit coupling is incorporated into a modified interdot tunnel coupling. We elucidate the role of the external magnetic field, the nuclear fields in the dots, and spin relaxation. We find qualitative agreement with experimental observations, and we propose a way to extend the range of magnetic fields in which blockade can be observed.",0905.1818v1 2009-05-20,Polaronic memristor strongly coupled to electrodes,"Attractive electron correlations due to an electron-vibron interaction (EVI) can overcome the direct Coulomb repulsion of polarons in strongly deformable molecular quantum dots (MQDs). If it realizes, a switching appears in the I-V characteristics of the degenerate nonadiabatic molecular bridges weakly coupled to electrodes providing a route to ultrafast `memristors' (memory-resistors) as the basis for future oscillators, amplifers, and other important circuit elements. Here, we extend our theory of polaronic memristors to adiabatic MQDs strongly coupled to the leads and show that the degeneracy of MQD (or other multilevel energy structure) along with the polaron-polaron attraction is a necessary ingredient of its switching behavior in the strong-coupling regime as well.",0905.3230v1 2009-05-20,Strong coupling theory for the Jaynes-Cummings-Hubbard model,"We present an analytic strong-coupling approach to the phase diagram and elementary excitations of the Jaynes-Cummings-Hubbard model describing a superfluid-insulator transition of polaritons in an array of coupled QED cavities. In the Mott phase, we find four modes corresponding to particle/hole excitations with lower and upper polaritons, respectively. Simple formulas are derived for the dispersion relation and spectral weights within a strong-coupling random-phase approximation (RPA). The phase boundary is calculated beyond RPA by including the leading correction due to quantum fluctuations.",0905.3344v2 2009-05-23,Weak and Strong-Coupling Electrostatic Interactions between Asymmetrically Charged Planar Surfaces,"We compare weak and strong coupling theory of counterion-mediated electrostatic interactions between two asymmetrically charged plates with extensive Monte-Carlo simulations. Analytical results in both weak and strong coupling limits compare excellently with simulations in their respective regimes of validity. The system shows a surprisingly rich structure in terms of interactions between the surfaces as well as fundamental qualitative differences in behavior in the weak and the strong coupling limits.",0905.3851v1 2009-06-03,Fast Electrical Control of a Quantum Dot Strongly Coupled to a Nano-resonator,"The resonance frequency of an InAs quantum dot strongly coupled to a GaAs photonic crystal cavity was electrically controlled via quantum confined Stark effect. Stark shifts up to 0.3meV were achieved using a lateral Schottky electrode that created a local depletion region at the location of the quantum dot. We report switching of a probe laser coherently coupled to the cavity up to speeds as high as 150MHz, limited by the RC constant of the transmission line. The coupling rate and the magnitude of the Stark shift with electric field were investigated while coherently probing the system.",0906.0751v1 2009-06-04,Theory of Optically-Driven Sideband Cooling for Atomic Collective Excitations and Its Generalization,"We explore how to cool atomic collective excitations in an optically-driven three-level atomic ensemble, which may be described by a model of coupled two harmonic oscillators (HOs) with a time-dependent coupling. Moreover, the coupled two-HO model is further generalized to address other cooling issues, where the lower-frequency HO can be cooled whenever the cooling process dominates over the heating one during the sideband transitions. Unusually, due to the absence of the heating process, the optimal cooling of our first cooling protocol for collective excitations in an atomic ensemble could break a usual sideband cooling limit for general coupled two-HO models.",0906.0806v1 2009-06-09,Quantum criticality near the Stoner transition in a two-dot with spin-orbit coupling,"We study a system of two tunnel-coupled quantum dots, with the first dot containing interacting electrons (described by the Universal Hamiltonian) not subject to spin-orbit coupling, whereas the second contains non-interacting electrons subject to spin-orbit coupling. We focus on describing the behavior of the system near the Stoner transition. Close to the critical point quantum fluctuations become important and the system enters a quantum critical regime. The large-$N$ approximation allows us to calculate physical quantitites reliably even in this strongly fluctuating regime. In particular, we find a scaling function to describe the crossover of the quasiparticle decay rate between the renormalized Fermi liquid regime and the quantum critical regime.",0906.1838v1 2009-06-17,Phase transition and correlation decay in Coupled Map Lattices,"For a Coupled Map Lattice with a specific strong coupling emulating Stavskaya's probabilistic cellular automata, we prove the existence of a phase transition using a Peierls argument, and exponential convergence to the invariant measures for a wide class of initial states using a technique of decoupling originally developed for weak coupling. This implies the exponential decay, in space and in time, of the correlation functions of the invariant measures.",0906.3017v2 2009-06-18,Do data favor neutrino mass and a coupling between Cold Dark Matter and Dark Energy?,"We allow simultaneously for a CDM--DE coupling and non--zero neutrino masses and find that significant coupling and neutrino mass are (slightly) statistically favoured in respect to a cosmology with no coupling and negligible neutrino mass (our best fits are: C~1/2m_p, m_\nu~0.12eV each flavor). We assume DE to be a self--interacting scalar field and use a standard Monte Carlo Markov Chain approach.",0906.3369v1 2009-06-23,Exact AdS/CFT spectrum: Konishi dimension at any coupling,"We compute the full dimension of Konishi operator in planar N=4 SYM theory it for a wide range of couplings, from weak to strong coupling regime, and predict the subleading terms in its strong coupling asymptotics. For this purpose we solve numerically the integral form of the AdS/CFT Y-system equations for the exact energies of excited states proposed by us and A.Kozak.",0906.4240v2 2009-06-29,Quantum logic with weakly coupled qubits,"There are well-known protocols for performing CNOT quantum logic with qubits coupled by particular high-symmetry (Ising or Heisenberg) interactions. However, many architectures being considered for quantum computation involve qubits or qubits and resonators coupled by more complicated and less symmetric interactions. Here we consider a widely applicable model of weakly but otherwise arbitrarily coupled two-level systems, and use quantum gate design techniques to derive a simple and intuitive CNOT construction. Useful variations and extensions of the solution are given for common special cases.",0906.5209v1 2009-07-02,Effect of next-nearest neighbor coupling on the optical spectra in bilayer graphene,"We investigate the dependence of the optical conductivity of bilayer graphene (BLG) on the intra- and inter-layer interactions using the most complete model to date. We show that the next nearest-neighbor intralayer coupling introduces new features in the low-energy spectrum that are highly sensitive to sample doping, changing significantly the ``universal'' conductance. Further, its interplay with interlayer couplings leads to an anisotropy in conductance in the ultraviolet range. We propose that experimental measurement of the optical conductivity of intrinsic and doped BLG will provide a good benchmark for the relative importance of intra- and inter-layer couplings at different doping levels.",0907.0504v1 2009-07-09,Higher-dimensional solitons and black holes with a non-minimally coupled scalar field,"We study higher-dimensional soliton and hairy black hole solutions of the Einstein equations non-minimally coupled to a scalar field. The scalar field has no self-interaction potential but a cosmological constant is included. Non-trivial solutions exist only when the cosmological constant is negative and the constant governing the coupling of the scalar field to the Ricci scalar curvature is positive. At least some of these solutions are stable when this coupling constant is not too large.",0907.1487v2 2009-07-12,Konishi at strong coupling from ABE,"In this letter, we derive analytically the scaling dimension of the Konishi operator in planar N=4 gauge theory at strong coupling from the asymptotic Bethe equations. The first two leading terms agree with the recent string computation and numerical analysis of TBA equations. At the third order we find spurious logarithm of the coupling constant, which should be absent in the anomalous dimension of any finite operator of planar N=4 SYM theory. Showing the cancelation of this term would provide an important test at strong coupling for the recently proposed sets of TBA equations for planar AdS/CFT correspondence.",0907.1919v1 2009-07-16,Entanglement localization after a coupling to incoherent noisy system,"We report the experimental realization of entanglement localization which restores polarization entanglement completely redirected after a linear coupling with incoherent and noisy surrounding photon. The method, based only on measurements of the surrounding photon after the coupling and on post-selection, can localize the entanglement back to original systems for any linear coupling.",0907.2780v1 2009-08-06,Coupled Modulated Bilayers,"We propose a model addressing the coupling mechanism between two spatially modulated monolayers. We obtain the mean-field phase diagrams of coupled bilayers when the two monolayers have the same preferred modulation wavelength. Various combinations of the monolayer modulated phases are obtained and their relative stability is calculated. Due to the coupling, a spatial modulation in one of the monolayers induces a similar periodic structure in the second one. We have also performed numerical simulations for the case when the two monolayers have different modulation wavelengths. Complex patterns may arise from the frustration between the two incommensurate but annealed structures.",0908.0871v2 2009-08-13,"Relativistic coupled-cluster calculations of $^{20}$Ne, $^{40}$Ar, $^{84}$Kr and $^{129}$Xe: correlation energies and dipole polarizabilities","We have carried out a detailed and systematic study of the correlation energies of inert gas atoms Ne, Ar, Kr and Xe using relativistic many-body perturbation theory and relativistic coupled-cluster theory. In the relativistic coupled-cluster calculations, we implement perturbative triples and include these in the correlation energy calculations. We then calculate the dipole polarizability of the ground states using perturbed coupled-cluster theory.",0908.1899v1 2009-08-20,Anomalous Quartic Gauge Couplings from Six Quark Production,"The absence of a light Higgs boson causes vector boson couplings to become strong at 1 TeV. A general framework for a systematic and consistent treatment is provided by effective theories of electroweak symmetry breaking. Already in next-to-leading order there appear quartic gauge couplings that go beyond the standard model and are hence called anomalous. We investigate intermediate three gauge boson states $W^+W^- Z$ and $ZZZ$ occurring in six quark production in electron positron collisions under the conditions of the International Linear Collider. We perform a sensitivity analysis of the relevant anomalous quartic gauge couplings presenting their expected limits.",0908.2951v1 2009-09-07,Fine structure in the tunneling spectra of electron-doped cuprates: No coupling to magnetic resonance mode,"We analyze high-resolution scanning tunneling spectra of the electron-doped cuprate Pr0.88LaCe0.12CuO4 (T_c = 24 K). We find that the spectral fine structure below 35 meV is consistent with strong coupling to a bosonic mode at 16 meV, in quantitative agreement with early tunneling spectra of Nd1.85Ce0.15CuO4. Since the energy of the bosonic mode is significantly higher than that (9.5-11 meV) of the magnetic resonance-like mode observed by inelastic neutron scattering, the coupling feature at 16 meV cannot arise from strong coupling to the magnetic mode. The present work thus demonstrates that the magnetic resonance-like mode cannot be the origin of high-temperature superconductivity in electron-doped cuprates.",0909.1136v1 2009-09-15,Critical current density for spin transfer torque switching with composite free layer structure,"Critical current density of composite free layer (CFL) in magnetic tunneling junction is investigated. CFL consists of two exchange coupled ferromagnetic layers, where the coupling is parallel or anti-parallel. Instability condition of the CFL under the spin transfer torque, which is related with critical current density, is obtained by analytic spin wave excitation model and confirmed by macro-spin Landau-Lifshitz-Gilbert equation. The critical current densities for the coupled two identical layers are investigated with various coupling strengths, and spin transfer torque efficiencies.",0909.2711v1 2009-09-22,"The exchange coupling between the valence electrons of the fullerene cage and the electrons of the N atoms in N@C60^{-1,3}","MCSCF calculations are performed in order to determine the exchange coupling between the 2p electrons of the N atom and the LUMOs of the fullerene cage in the case of mono- and tri-anions of N@C60. The exchange coupling resulted by our calculations is large compared to the hyperfine interaction. The strong coupling can explain the missing EPR signal of the nitrogen in paramagnetic anions.",0909.3939v1 2009-09-22,Probing New Physics in Charm Couplings with Kaon and Other Hadron Processes,"It is possible that the low-energy effects of physics beyond the standard model can be parametrized mainly by anomalous couplings of quarks to the W boson. Such couplings can generate potentially significant contributions to various transitions that can be probed by current and future experiments. This work explores constraints on anomalous charm-W couplings from a number of CP-conserving and -violating processes involving the kaon and other flavored hadrons.",0909.3957v1 2009-10-14,Running of the coupling and quark mass in SU(2) with two adjoint fermions,"We simulate SU(2) gauge theory with two massless Dirac fermions in the adjoint representation. We calculate the running of the Schroedinger Functional coupling and the renormalised quark mass over a wide range of length scales. The running of the coupling is consistent with the existence of an infrared fixed point (IRFP), and we find 0.07 < gamma < 0.56 at the IRFP, depending on the value of the critical coupling.",0910.2562v1 2009-10-14,Plasmon-phonon Strongly-Coupled Mode in Epitaxial Graphene,"We report the dispersion measurements, using angle-resolved reflection electron-energy-loss-spectroscopy (AREELS), on two-dimensional (2D) plasmons in single and multilayer graphene which couple strongly to surface optical phonon (FK phonon) modes of silicon carbide substrate. The coupled modes show discrete dispersion behaviors in the single and bilayer graphene. With increasing graphene layers on SiC(0001), a transition from plasmon-like dispersion to phonon-like dispersion is observed. For plasmon-like modes, the dispersion is strongly damped by electron-hole pair excitations at entering single-particle continuum, while phonon-like mode is undamped. In the region free of coupling, the graphene 2D plasmon exhibits acoustic behavior with linear dispersion with slope and damping determined by the Fermi surface topology.",0910.2735v1 2009-10-16,Finite-size scaling tests for SU(3) lattice gauge theory with color sextet fermions,"The observed slow running of the gauge coupling in SU(3) lattice gauge theory with two flavors of color sextet fermions naturally suggests it is a theory with one relevant coupling, the fermion mass, and that at zero mass correlation functions decay algebraically. I perform a finite-size scaling study on simulation data at two values of the bare gauge coupling with this assumption and observe a common exponent for the scaling of the correlation length with the fermion mass, y_m ~ 1.5. An analysis of the scaling of valence Dirac eigenvalues at one of these bare couplings produces a similar number.",0910.3072v1 2009-11-19,Non-minimal Kinetic coupling to gravity and accelerated expansion,"We study a scalar field with kinetic term coupled to itself and to the curvature, as a source of dark energy, and analyze the role of this new coupling in the accelerated expansion at large times. In the case of scalar field dominance, the scalar field and potential giving rise to power-law expansion are found in some cases, and a dynamical equation of state is calculated for a given solution of the field equations. A behavior very close to that of the cosmological constant was found.",0911.3702v2 2010-01-04,Nonminimal Inflation on the Randall-Sundrum II Brane with Induced Gravity,"We study an inflation model that inflaton field is non-minimally coupled to the induced scalar curvature on the Randall-Sundrum (RS) II brane. We investigate the effects of the non-minimal coupling on the inflationary dynamics of this braneworld model. Our study shows that the number of e-folds decreases by increasing the value of the non-minimal coupling. We compare our model parameters with the minimal case and also with recent observational data. In comparison with recent observation, we obtain a constraint on the values that the non-minimal coupling attains.",1001.0444v1 2010-01-14,State transfer in static and dynamic spin chains with disorder,"We examine the speed and fidelity of several protocols for state or single excitation transfer in finite spin chains subject to diagonal and off-diagonal disorder. We find that, for a given chain length and maximal achievable inter-spin exchange (XY) coupling strength, the optimal static spin-coupling protocol, implementing the fastest state transfer between the two ends of the chain, is more susceptible to off-diagonal (XY coupling) disorder, as compared to a much slower but robust adiabatic transfer protocol with time-dependent coupling strengths.",1001.2444v1 2010-01-15,The innocuousness of adiabatic instabilities in coupled scalar field-dark matter models,"Non-minimally coupled scalar field models suffer of unstable growing modes at the linear perturbation level. The nature of these instabilities depends on the dynamical state of the scalar field. In particular in systems which admit adiabatic solutions, large scale instabilities are suppressed by the slow-roll dynamics of the field. Here we review these results and present a preliminary likelihood data analysis suggesting that along adiabatic solutions coupled models with coupling of order of gravitational strength can provide viable cosmological scenarios satisfying constraints from SN Ia, CMB and large scale structure data.",1001.2687v1 2010-01-25,Spontaneous creation of non-zero angular momentum modes in tunnel-coupled two-dimensional degenerate Bose gases,"We investigate the dynamics of two tunnel-coupled two-dimensional degenerate Bose gases. The reduced dimensionality of the clouds enables us to excite specific angular momentum modes by tuning the coupling strength, thereby creating striking patterns in the atom density profile. The extreme sensitivity of the system to the coupling and initial phase difference results in a rich variety of subsequent dynamics, including vortex production, complex oscillations in relative atom number and chiral symmetry breaking due to counter-rotation of the two clouds.",1001.4344v1 2010-02-03,Deformation Potentials and Electron-Phonon Coupling in Silicon Nanowires,"The role of reduced dimensionality and of the surface on electron-phonon (e-ph) coupling in silicon nanowires is determined from first principles. Surface termination and chemistry is found to have a relatively small influence, whereas reduced dimensionality fundamentally alters the behavior of deformation potentials. As a consequence, electron coupling to ""breathing modes"" emerges that cannot be described by conventional treatments of e-ph coupling. The consequences for physical properties such as scattering lengths and mobilities are significant: the mobilities for [110] grown wires are 6 times larger than those for [100] wires, an effect that cannot be predicted without the form we find for Si nanowire deformation potentials.",1002.0719v1 2010-02-04,Entanglement of fields in coupled-cavities: effects of pumping and fluctuations,"A system of two coupled cavities is studied in the context of bipartite, continuous variable entanglement. One of the cavities is pumped by an external classical source that is coupled quadratically, to the cavity field. Dynamics of entanglement, quantified by covariance measure [Dodonov {\it et al}, Phys. Lett A {\bf 296}, (2002) 73], in the presence of cavity-cavity coupling and external pumping is investigated. The importance of tailoring the coupling between the cavities is brought out by studying the effects of pump fluctuations on the entanglement.",1002.0913v1 2010-02-04,The electron-phonon theory of superconductors: Tc map and vertex correction,"The strong coupling Eliashberg theory plus vertex correction is used to calculate maps of transition temperature (Tc) in parameter-space characterizing superconductivity. Based on these Tc maps, crossover behaviors are found when electron-phonon interaction increases from weak-coupling region to strong coupling region. Especially, the combined interaction of vertex correction and Coulomb interaction can efficiently depress Tc from extremely high values in standard strong-coupling theory to reasonable values found in experiments and successfully explain the doing-dependent Tc of cuprate superconductors. The strong non-adiabatic effect is the barrier for high-Tc in compounds with compositions of light atoms and with high phonon frequencies.",1002.0998v2 2010-03-08,Spin-orbit coupling in a graphene bilayer and in graphite,"The intrinsic spin-orbit interactions in bilayer graphene and in graphite are studied, using a tight binding model, and an intraatomic LS coupling. The spin-orbit interactions in bilayer graphene and graphite are larger, by about one order of magnitude, than the interactions in single layer graphene, due to the mixing of pi and sigma bands by interlayer hopping. Their value is in the range 0.1 - 1K. The spin-orbit coupling opens a gap in bilayer graphene, and it also gives rise to two edge modes. The spin-orbit couplings are largest, 1-4K, in orthorhombic graphite, which does not have a center of inversion.",1003.1618v1 2010-03-09,Ground state properties of the Holstein model near the adiabatic limit,"We adapt a variational procedure to calculate ground state properties of the Holstein model in the adiabatic limit. At strong coupling, this adaption leads to rapid convergence of results. The intermediate coupling regime is further handled with an adaptive algorithm. We also use semi-classically derived results for the adiabatic end-point, along with weak coupling perturbation theory. These establish weak and strong coupling (or large and small polaron, respectively) regimes in two dimensions or higher. As is well known, these are connected smoothly, but the cross-over becomes increasingly abrupt as the phonon frequency decreases.",1003.1952v1 2010-03-19,Competition between symmetry breaking and onset of collapse in weakly coupled atomic condensates,"We analyze the symmetry breaking of matter-wave solitons in a pair of cigar-shaped traps coupled by tunneling of atoms. The model is based on a system of linearly coupled nonpolynomial Schr\""odinger equations (NPSEs). Unlike the well-known spontaneous-symmetry-breaking (SSB) bifurcation in coupled cubic equations, in the present model the SSB competes with the onset of collapse in this system. Stability regions of symmetric and asymmetric solitons, as well as the collapse region, are identified in the parameter space of the system.",1003.3835v1 2010-03-30,The constructive role of diversity on the global response of coupled neuron systems,"We study the effect that the heterogeneity present among the elements of an ensemble of coupled excitable neurons have on the collective response of the system to an external signal. We have considered two different interaction scenarios, one in which the neurons are diffusively coupled and another in which the neurons interact via pulse-like signals. We found that the type of interaction between the neurons has a crucial role in determining the response of the system to the external modulation. We develop a mean-field theory based on an order parameter expansion that quantitatively reproduces the numerical results in the case of diffusive coupling.",1003.5804v1 2010-04-12,Spontaneous Symmetry Breaking in Two Coupled Nanomechanical Electron Shuttles,"We present spontaneous symmetry breaking in a nanoscale version of a setup prolific in classical mechanics: two coupled nanomechanical pendulums. The two pendulums are electron shuttles fabricated as nanopillars and placed between two capacitor plates in a homogeneous electric field. Instead of being mechanically coupled through a spring they exchange electrons, i.e. they shuttle electrons from the source to the drain 'capacitor plate'. Nonzero DC current through this system by external AC excitation is caused via dynamical symmetry breaking. This symmetry-broken current appears at sub- and superharmonics of the fundamental mode of the coupled system.",1004.2028v1 2010-04-23,Spin-orbit coupling and perpendicular Zeeman field for fermionic cold atoms: observation of the intrinsic anomalous Hall effect,"We propose a scheme for generating Rashba spin-orbit coupling and perpendicular Zeeman field simultaneously for cold fermionic atoms in a harmonic trap through the coupling between atoms and laser fields. The realization of Rashba spin-orbit coupling and perpendicular Zeeman field provides opportunities for exploring many topological phenomena using cold fermionic atoms. We focus on the intrinsic anomalous Hall effect and show that it may be observed through the response of atomic density to a rotation of the harmonic trap.",1004.4231v3 2010-04-26,Controlling Entanglement Dynamics by Choosing Appropriate Ratio between Cavity-Fiber Coupling and Atom-Cavity Coupling,"The entanglement characteristics including the so-called sudden death effect between two identical two-level atoms trapped in two separate cavities connected by an optical fiber are studied. The results show that the time evolution of entanglement is sensitive not only to the degree of entanglement of the initial state but also to the ratio between cavity-fiber coupling () and atom-cavity coupling (). This means that the entanglement dynamics can be controlled by choosing specific v and g.",1004.4395v2 2010-04-29,Coupled tensorial form for atomic relativistic two-particle operator given in second quantization representation,"General formulas of the two-electron operator representing either atomic or effective interactions are given in a coupled tensorial form in relativistic approximation. The alternatives of using uncoupled, coupled and antisymmetric two-electron wave functions in constructing coupled tensorial form of the operator are studied. The second quantization technique is used. The considered operator acts in the space of states of open-subshell atoms.",1004.5259v1 2010-04-29,On Synchronization of Coupled Hopf-Kuramoto Oscillators with Phase Delays,"This paper presents new methods and results on almost global synchronization of coupled Hopf nonlinear oscillators, which are commonly used as the dynamic model of engineered central pattern generators (CPGs). On balanced graphs, any positive coupling gain is proven to induce almost global asymptotic synchronization, and a threshold value for truly global exponential synchronization is also computed. Furthermore, a hierarchical connection between coupled Hopf oscillators and Kuramoto oscillators is identified. Finally, a new result on the synchronization of Kuramoto oscillators with arbitrary time-varying heterogeneous frequencies and delays is derived.",1004.5366v2 2010-06-04,Mutual Coupling Reduction in Two-Dimensional Array of Microstrip Antennas Using Concave Rectangular Patches,"Using concave rectangular patches, a new solution to reduce mutual coupling and return loss in two-dimensional array of microstrip antennas is proposed. The effect of width and length concavity on mutual coupling and return loss is studied. Also, the patch parameters as well as the amounts of width and length concavity are optimized using an enhanced genetic algorithm. Simulation results show that the resulting array antenna has low amounts of mutual coupling and return loss.",1006.0839v1 2010-06-10,Variational study of a two-level system coupled to a harmonic oscillator in a ultrastrong coupling regime,"The nonclassical behaviors of a two-level system coupled to a harmonic oscillator is investigated in the ultrastrong coupling regime. We revisit the variational solution of the ground state and find that the existing solution do not account accurately for nonclassical effects such squeezing. We suggest a new trial wave function and demonstrate that it has an excellent accuracy on the quantum correlation effects as well as on energy.",1006.1989v2 2010-06-17,Measurement of Higgs Anomalous Coupling with H->WW* at International Linear Collider,"The measurement of the Higgs coupling to W bosons is an important program at the international linear collider (ILC) to search for the anomaly in the coupling to the gauge bosons. We study the sensitivity of ILC to the Higgs anomalous coupling to W bosons by using ZH->vvWW* events. In this article, we report the status of the study.",1006.3427v1 2010-06-17,Microwave fidelity studies by varying antenna coupling,"The fidelity decay in a microwave billiard is considered, where the coupling to an attached antenna is varied. The resulting quantity, coupling fidelity, is experimentally studied for three different terminators of the varied antenna: a hard wall reflection, an open wall reflection, and a 50 Ohm load, corresponding to a totally open channel. The model description in terms of an effective Hamiltonian with a complex coupling constant is given. Quantitative agreement is found with the theory obtained from a modified VWZ approach [Verbaarschot et al, Phys. Rep. 129, 367 (1985)].",1006.3478v2 2010-06-17,N=2 Generalized Superconformal Quiver Gauge Theory,"Four dimensional N=2 generalized superconformal field theory can be defined by compactifying six dimensional (0,2) theory on a Riemann surface with regular punctures. In previous studies, gauge coupling constant space is identified with the moduli space of punctured Riemann surface M_{g,n}. We show that the weakly coupled gauge group description corresponds to a stable nodal curve, and the coupling space is actually the Deligne-Mumford compactification \bar{M}_{g,n}. We also give an algorithm to determine the weakly coupled gauge group and matter content in any duality frame.",1006.3486v2 2010-06-28,On the Coupling Property of Lévy Processes,"We give necessary and sufficient conditions guaranteeing that the coupling for L\'evy processes (with non-degenerate jump part) is successful. Our method relies on explicit formulae for the transition semigroup of a compound Poisson process and earlier results by Mineka and Lindvall-Rogers on couplings of random walks. In particular, we obtain that a L\'{e}vy process admits a successful coupling, if it is a strong Feller process or if the L\'evy (jump) measure has an absolutely continuous component.",1006.5288v2 2010-07-01,Coupling by reflection of diffusion processes via discrete approximation under a backward Ricci flow,"A coupling by reflection of a time-inhomogeneous diffusion process on a manifold are studied. The condition we assume is a natural time-inhomogeneous extension of lower Ricci curvature bounds. In particular, it includes the case of backward Ricci flow. As in time-homogeneous cases, our coupling provides a gradient estimate of the diffusion semigroup which yields the strong Feller property. To construct the coupling via discrete approximation, we establish the convergence in law of geodesic random walks as well as a uniform non-explosion type estimate.",1007.0275v1 2010-07-15,Perturbations in Matter Bounce with Non-minimal Coupling,"In this paper, we investigate the perturbations in matter bounce induced from Lee-Wick lagrangian with the involvement of non-minimal coupling to the Einstein Gravity. We find that this extra non-minimal coupling term can cause a red-tilt on the primordial metric perturbation at extremely large scales. It can also lead to large enhancement of reheating of the normal field particles compared to the usual minimal coupling models.",1007.2571v2 2010-09-15,Two-Photon Transport in a Waveguide Coupled to a Cavity with a Two-level System,"We consider a system where a waveguide is coupled to a cavity embedded with a two-level system (TLS), and study the effects when a two-photon quantum state is injected into the waveguide. The wave function of two outgoing photons is exactly solved using the Lehmann-Symanzik-Zimmermann (LSZ) reduction formalism. Our results explicitly exhibit the photon blockade effects in the strong atom-cavity coupling regime. The quantum statistical characters of the outgoing photons, including the photon bunching and anti-bunching behaviors, are also investigated in both the strong and weak coupling regimes. These results agree with the observations of recent experiments.",1009.2828v1 2010-09-27,Higher-order coupled quintessence,"We study a coupled quintessence model in which the interaction with the dark matter sector is a function of the quintessence potential. Such a coupling can arise from a field dependent mass term for the dark matter field. The dynamical analysis of a standard quintessence potential coupled with the interaction explored here shows that the system possesses a late time accelerated attractor. In light of these results, we perform a fit to the most recent Supernovae Ia, Cosmic Microwave Background and Baryon Acoustic Oscillation data sets. Constraints arising from weak equivalence principle violation arguments are also discussed.",1009.5263v1 2010-09-27,$g_{D^{\ast}_{s}D K^{\ast}(892)}$ and $g_{B^{\ast}_{s}B K^{\ast}(892)}$ coupling constants in QCD sum rules,"The coupling constants $g_{D^{\ast}_{s}D K^{\ast}(892)}$ and $g_{B^{\ast}_{s}B K^{\ast}(892)}$ are calculated in the framework of three-point QCD sum rules. The correlation functions responsible for these coupling constants are evaluated considering contributions of both $D(B)$ and $K^*(892)$ mesons as off-shell states, but in the absence of radiative corrections. The results, $g_{D^{\ast}_{s}D K^{\ast}(892)}=(4.31\pm1.42) GeV^{-1}$ and $g_{B^{\ast}_{s}B K^{\ast}(892)}=(3.24\pm1.08) GeV^{-1}$ are obtained for the considered strong coupling constants.",1009.5320v2 2010-10-05,Electromagnetically Induced Transparency from Two Phonon Processes in Quadratically Coupled Membranes,"We describe how electromagnetically induced transparency can arise in quadratically coupled optomechanical systems. Due to quadratic coupling the underlying optical process involves a two phonon process in optomechanical system and this two phonon process makes the mean amplitude, which plays the role of atomic coherence in traditional EIT, zero. We show how the fluctuation in displacement can play a role similar to atomic coherence and can lead to EIT-like effects in quadratically coupled optomechanical systems. We show how such effects can be studied using the existing optomechanical systems.",1010.0757v1 2010-10-21,Anomalous coupling of scalars to gauge fields,"We study the transformation properties of a scalar-tensor theory, coupled to fermions, under the Weyl rescaling associated with a transition from the Jordan to the Einstein frame. We give a simple derivation of the corresponding modification to the gauge couplings. After changing frame, this gives rise to a direct coupling between the scalar and the gauge fields.",1010.4536v2 2010-10-23,Unconventional plasmon-phonon coupling in graphene,"We calculate hybridization of plasmons and intrinsic optical phonons in graphene by using the self-consistent linear response formalism. We find that longitudinal plasmons (transverse magnetic modes) couple exclusively to transverse optical phonons, whereas graphene's transverse plasmons (transverse electric modes) couple only to longitudinal optical phonons. This mixing of polarizations is in contrast to the usual plasmon-phonon coupling in other systems. The resulting change in phonon frequencies increases (decreases) for transverse (longitudinal) phonons by increasing the concentration of charge carriers.",1010.4871v2 2010-11-09,Matching with Couples Revisited,"It is well known that a stable matching in a many-to-one matching market with couples need not exist. We introduce a new matching algorithm for such markets and show that for a general class of large random markets the algorithm will find a stable matching with high probability. In particular we allow the number of couples to grow at a near-linear rate. Furthermore, truth-telling is an approximated equilibrium in the game induced by the new matching algorithm. Our results are tight: for markets in which the number of couples grows at a linear rate, we show that with constant probability no stable matching exists.",1011.2121v2 2010-12-06,Extreme value statistics in coupled lasers,"Experimental configuration for investigating the dynamics and the statistics of the phase locking level of coupled lasers that have no common frequency is presented. The results reveal that the probability distribution of the phase locking level of such coupled lasers fits a Gumbel distribution that describes the extreme value statistic of Gaussian processes. A simple model, based on the spectral response of the coupled lasers, is also described, and the calculated results are in good agreement with the experimental results.",1012.1292v1 2010-12-27,Quantum behaviour of a flux qubit coupled to a resonator,"We present a detailed theoretical analysis for a system of a superconducting flux qubit coupled to a transmission line resonator. The master equation, accounting incoherent processes for a weakly populated resonator, is analytically solved. An electromagnetic wave transmission coefficient through the system, which provides a tool for probing dressed states of the qubit, is derived. We also consider a general case for the resonator with more than one photon population and compare the results with an experiment on the qubit-resonator system in the intermediate coupling regime, when the coupling energy is comparable with the qubit relaxation rate.",1012.5599v1 2011-01-05,Statistical Evidence Against Simple Forms of Wavefunction Collapse,"If the initial quantum state of the universe is a multiverse superposition over many different sets of values of the effective coupling ""constants"" of physics, and if this quantum state collapses to an eigenstate of the set of coupling ""constants"" with a probability purely proportional to the absolute square of the amplitude (with no additional factor for something like life or consciousness), then one should not expect that the coupling `constants' would be so biophilic as they are observed to be. Therefore, the observed biophilic values (apparent fine tuning) of the coupling ""constants"" is statistical evidence against such simple forms of wavefunction collapse.",1101.1083v1 2011-01-14,Weak coupling limits in a stochastic model of heat conduction,"We study the Brownian momentum process, a model of heat conduction, weakly coupled to heat baths. In two different settings of weak coupling to the heat baths, we study the non-equilibrium steady state and its proximity to the local equilibrium measure in terms of the strength of coupling. For three and four site systems, we obtain the two-point correlation function and show it is generically not multilinear.",1101.2877v1 2011-01-17,Desynchronization bifurcation of coupled nonlinear dynamical systems,"We analyze the desynchronization bifurcation in the coupled R\""ossler oscillators. After the bifurcation the coupled oscillators move away from each other with a square root dependence on the parameter. We define system transverse Lyapunov exponents and in the desynchronized state one is positive while the other is negative implying that one oscillator is trying to fly away while the other is holding it. We give a simple model of coupled integrable systems that shows a similar phenomena and can be treated as the normal form for the desynchronization bifurcation. We conclude that the desynchronization is a pitchfork bifurcation of the transverse manifold.",1101.3130v1 2011-01-18,Magnetic Excitations in the Site-Centered Stripe Phase: Spin Wave Theory of Coupled Three-Leg Ladders,"The success of models of coupled two-leg spin ladders in describing the magnetic excitation spectrum of La_{2-x}Ba_xCuO_4 had been interpreted previously as evidence for bond-centered stripes. In a recent article, however, we have determined the magnetic coupling induced by the charge stripes between bond- or site-centered spin stripes modeled by two- or three-leg ladders, respectively. We found that only the site-centered models order. We further indicated excellent agreement of a fully consistent analysis of coupled three-leg ladders using a spin wave theory of bond with the experimental data. Here, we provide a full and detailed account of this analysis.",1101.3434v1 2011-01-20,Synchronization of chaotic networks with time-delayed couplings: An analytic study,"Networks of nonlinear units with time-delayed couplings can synchronize to a common chaotic trajectory. Although the delay time may be very large, the units can synchronize completely without time shift. For networks of coupled Bernoulli maps, analytic results are derived for the stability of the chaotic synchronization manifold. For a single delay time, chaos synchronization is related to the spectral gap of the coupling matrix. For networks with multiple delay times, analytic results are obtained from the theory of polynomials. Finally, the analytic results are compared with networks of iterated tent maps and Lang-Kobayashi equations which imitate the behaviour of networks of semiconductor lasers.",1101.3956v1 2011-02-14,Turing instability in oscillator chains with non-local coupling,"We investigate analytically and numerically the conditions for the Turing instability to occur in a one-dimensional chain of nonlinear oscillators coupled non-locally in such a way that the coupling strength decreases with the spatial distance as a power-law. A range parameter makes possible to cover the two limiting cases of local (nearest-neighbor) and a global (all-to-all) couplings. We consider an example from a non-linear auto-catalytic reaction-diffusion model.",1102.2834v1 2011-02-15,A Phenomenological Study on Threshold Improvement via Spatial Coupling,"Kudekar et al. proved an interesting result in low-density parity-check (LDPC) convolutional codes: The belief-propagation (BP) threshold is boosted to the maximum-a-posteriori (MAP) threshold by spatial coupling. Furthermore, the authors showed that the BP threshold for code-division multiple-access (CDMA) systems is improved up to the optimal one via spatial coupling. In this letter, a phenomenological model for elucidating the essence of these phenomenon, called threshold improvement, is proposed. The main result implies that threshold improvement occurs for spatially-coupled general graphical models.",1102.3056v2 2011-02-16,Lagrange equations coupled to a thermal equation: mechanics as consequence of thermodynamics,"Following the analytic approach to thermodynamics developed by Stueckelberg, we study the evolution equations of a closed thermodynamic system consisting of point particles in a fluid. We obtain a system of coupled differential equations describing the mechanical and the thermal evolution of the system. The coupling between these evolution equations is due to the action of a viscous friction term. Finally, we apply our coupled evolution equations to study the thermodynamics of an isolated system consisting of identical point particles interacting through a harmonic potential.",1102.3418v1 2011-02-21,Multifractal analysis of nonhyperbolic coupled map lattices: Application to genomic sequences,"Symbolic sequences generated by coupled map lattices (CMLs) can be used to model the chaotic-like structure of genomic sequences. In this study it is shown that diffusively coupled Chebyshev maps of order 4 (corresponding to a shift of 4 symbols) very closely reproduce the multifractal spectrum $D_q$ of human genomic sequences for coupling constant $\alpha =0.35\pm 0.01$ if $q>0$. The presence of rare configurations causes deviations for $q<0$, which disappear if the rare event statistics of the CML is modified. Such rare configurations are known to play specific functional roles in genomic sequences serving as promoters or regulatory elements.",1102.4237v1 2011-02-25,Entanglement Entropy of Coupled Conformal Field Theories and Fermi Liquids,"In this paper we calculate the entanglement entropy of two coupled gapless systems in general spatial dimension d. The gapless systems can be either conformal field theories (CFT), or Fermi liquids. We assume the two systems are coupled uniformly in a h-dimensional submanifold of the space, with 0 <= h <= d. We will focus on the scaling of the entanglement entropy with the size of the system, and its scaling with the inter-system coupling constant g. Three approaches will be used for our calculation: (1) exact calculation with ground state wave-functional, (2) perturbative calculation with functional path integral, (3) scaling argument.",1102.5345v1 2011-03-02,Center manifold reduction for large populations of globally coupled phase oscillators,"A bifurcation theory for a system of globally coupled phase oscillators is developed based on the theory of rigged Hilbert spaces. It is shown that there exists a finite-dimensional center manifold on a space of generalized functions. The dynamics on the manifold is derived for any coupling functions. When the coupling function is $\sin \theta $, a bifurcation diagram conjectured by Kuramoto is rigorously obtained. When it is not $\sin \theta $, a new type of bifurcation phenomenon is found due to the discontinuity of the projection operator to the center subspace.",1103.0363v1 2011-03-14,Conflicting coupling of the unpaired nucleons and the structure of collective bands in odd-odd nuclei,"Conflicting coupling of unpaired nucleons in the odd-odd nuclei is discussed. A very simple explanation is suggested for the damping of the energy spacing of the lowest levels in the rotational bands in the odd-odd nuclei in the case of a ""conflicting"" coupling of the odd proton and neutron comparative to those of the bands based on the state of the strongly-coupled particle in the neighbouring odd nuclei entering the ""conflicting"" configuration.",1103.2609v1 2011-03-15,Coupled-resonator-induced transparency with a squeezed vacuum,"We present the first experimental observation of quantum fluctuation spectra in two coupled optical cavities with an injected squeezed vacuum light. The quadrature components of the reflected squeezed vacuum spectra are measured by phase sensitive homodyne detector. The experimental results demonstrate coupled-resonator-induced transparency in the quantum regime, in which electromagnetically-induced-transparency-like characteristic of the absorption and dispersion properties of the coupled optical cavities determines the line-shape of the reflected quantum noise spectra.",1103.2836v2 2011-03-28,Coupled coincidence point theorems for nonlinear contractions in partially ordered metric spaces,"We obtain coupled coincidence and coupled common fixed point theorems for mixed $g$-monotone nonlinear operators $F:X \times X \rightarrow X$ in partially ordered metric spaces. Our results are generalizations of recent coincidence point theorems due to Lakshmikantham and \' Ciri\' c [Lakshmikantham, V., \' Ciri\' c, L., \textit{Coupled fixed point theorems for nonlinear contractions in partially ordered metric spaces}, Nonlinear Anal. \textbf{70} (2009), 4341-4349], of coupled fixed point theorems established by Bhaskar and Lakshmikantham [T.G. Bhaskar, V. Lakshmikantham, \textit{Fixed point theorems in partially ordered metric spaces and applications}, Nonlinear Anal. \textbf{65} (2006) 1379-1393] and also include as particular cases several related results in very recent literature.",1103.5288v1 2011-03-28,Klein-tunneling-enhanced directional coupler for Dirac electron wave in graphene,"Using the coupled-mode theory in guided-wave optics and electronics, we explore a directional coupling structure composed of two parallel waveguides electrostatically induced by the split-gate technique in bulk graphene. Our results show that Klein tunneling can greatly enhance the coupling strength of the structure. By adjusting a gate voltage, the probability density of Dirac electron wave function initially in one waveguide can be completely transferred into the other waveguide within several hundred nanometers. Our findings could not only lead to functional coherent coupling devices for quantum-based electronic signal processing and on-chip device integration in graphene, but also shrink the size of the devices to facilitate the fabrication of graphene-based large-scale integrated logic circuits.",1103.5375v1 2011-03-31,Dynamics of multi-frequency oscillator ensembles with resonant coupling,"We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2:1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed.",1103.6194v1 2011-04-10,Linear Stationary Iterative Methods for the Force-based Quasicontinuum Approximation,"Force-based multiphysics coupling methods have become popular since they provide a simple and efficient coupling mechanism, avoiding the difficulties in formulating and implementing a consistent coupling energy. They are also the only known pointwise consistent methods for coupling a general atomistic model to a finite element continuum model. However, the development of efficient and reliable iterative solution methods for the force-based approximation presents a challenge due to the non-symmetric and indefinite structure of the linearized force-based quasicontinuum approximation, as well as to its unusual stability properties. In this paper, we present rigorous numerical analysis and computational experiments to systematically study the stability and convergence rate for a variety of linear stationary iterative methods.",1104.1774v1 2011-04-12,On the Coupling Property and the Liouville Theorem for Ornstein-Uhlenbeck Processes,"Using a coupling for the weighted sum of independent random variables and the explicit expression of the transition semigroup of Ornstein-Uhlenbeck processes driven by compound Poisson processes, we establish the existence of a successful coupling and the Liouville theorem for general Ornstein-Uhlenbeck processes. Then we present the explicit coupling property of Ornstein-Uhlenbeck processes directly from the behaviour of the corresponding symbol or characteristic exponent. This approach allows us to derive gradient estimates for Ornstein-Uhlenbeck processes via the symbol.",1104.2166v2 2011-04-20,SIR epidemics in monogamous populations with recombination,"We study the propagation of an SIR (susceptible-infectious-recovered) disease over an agent population which, at any instant, is fully divided into couples of agents. Couples are occasionally allowed to exchange their members. This process of couple recombination can compensate the instantaneous disconnection of the interaction pattern and thus allow for the propagation of the infection. We study the incidence of the disease as a function of its infectivity and of the recombination rate of couples, thus characterizing the interplay between the epidemic dynamics and the evolution of the population's interaction pattern.",1104.4102v1 2011-05-24,Enumerating ODE Equivalent Homogeneous Networks,"We give an simple criterion for ODE equivalence in identical edge homogeneous coupled cell networks. This allows us to give a simple proof of Theorem 10.3 of Aquiar and Dias ""Minimal Coupled Cell Networks"", which characterizes minimal identical edge homogeneous coupled cell networks. Using our criterion we give a formula for counting homogeneous coupled cell networks up to ODE equivalence. Our criterion is purely graph theoretic and makes no explicit use of linear algebra.",1105.4812v1 2011-06-09,Hamiltonian of mean force for damped quantum systems,"We consider a quantum system linearly coupled to a reservoir of harmonic oscillators. For finite coupling strengths, the stationary distribution of the damped system is not of the Gibbs form, in contrast to standard thermodynamics. With the help of the quantum Hamiltonian of mean force, we quantify this deviation exactly for a harmonic oscillator and provide approximations in the limit of high and low temperatures, and weak and strong couplings. Moreover, in the semiclassical regime, we use the quantum Smoluchowski equation to obtain results valid for any potential. We, finally, give a physical interpretation of the deviation in terms of the initial system-reservoir coupling.",1106.1775v1 2011-06-22,Complete chaotic synchronization and exclusion of mutual Pyragas control in two delay-coupled Rössler-type oscillators,"Two identical chaotic oscillators that are mutually coupled via time delayed signals show very complex patterns of completely synchronized dynamics including stationary states and periodic as well as chaotic oscillations. We have experimentally observed these synchronized states in delay-coupled electronic circuits and have analyzed their stability by numerical simulations and analytical calculations. We found that the conditions for longitudinal and transversal stability largely exclude each other and prevent e.g. the synchronization of Pyragas-controlled orbits. Most striking is the observation of complete chaotic synchronization for large delay times, which should not be allowed in the given coupling scheme on the background of the actual paradigm.",1106.4420v1 2011-06-28,Phase separation in a polarized Fermi gas with spin-orbit coupling,"We study the phase separation of a spin polarized Fermi gas with spin-orbit coupling near a wide Feshbach resonance. As a result of the competition between spin-orbit coupling and population imbalance, the phase diagram for a uniform gas develops a rich structure of phase separation involving gapless superfluid states which are topologically non-trivial. We find that these novel gapless phases can be stabilized by intermediate spin-orbit coupling strengths. We then demonstrate the phase separation induced by an external trapping potential and discuss the optimal parameter region for the experimental observation of the gapless superfluid phases.",1106.5667v2 2011-06-28,Quantum Brownian motion of multipartite systems and their entanglement dynamics,"We solve the model of N quantum Brownian oscillators linearly coupled to an environment of quantum oscillators at finite temperature, with no extra assumptions about the structure of the system-environment coupling. Using a compact phase-space formalism, we give a rather quick and direct derivation of the master equation and its solutions for general spectral functions and arbitrary temperatures. Since our framework is intrinsically nonperturbative, we are able to analyze the entanglement dynamics of two oscillators coupled to a common scalar field in previously unexplored regimes, such as off resonance and strong coupling.",1106.5752v1 2011-07-04,Anomalous Hall conductivity from the dipole mode of spin-orbit-coupled cold-atom systems,"Motivated by recent experiments [Lin {\it et al.}, Nature {\bf 417}, 83 (2011)] that engineered spin-orbit coupling in ultra-cold mixtures of bosonic atoms, we study the dipole oscillation of trapped spin-orbit-coupled non-condensed Bose and Fermi gases. We find that different directions of oscillation are coupled by the spin-orbit interactions. The phase difference between oscillatory motion in orthogonal directions and the trapping frequencies of the modes are shown to be related to the anomalous Hall conductivity. Our results can be used to experimentally determine the anomalous Hall conductivity for cold-atom systems.",1107.0578v1 2011-07-08,Emission spectrum of quasi-resonant laterally coupled quantum dots,"We calculate the emission spectrum of neutral and charged excitons in a pair of laterally coupled InGaAs quantum dots with nearly degenerate energy levels. As the interdot distance decreases, a number of changes take place in the emission spectrum which can be used as indications of molecular coupling. These signatures ensue from the stronger tunnel-coupling of trions as compared to that of neutral excitons.",1107.1590v2 2011-07-09,Coupled-wave model for square-lattice photonic-crystal lasers with TE polarization -- a general approach,"A general coupled-wave model is presented for square-lattice photonic crystal (PC) lasers with transverse-electric polarization. This model incorporates the high-order coupling effects that are important for two-dimensional PC laser cavities and gives a general and rigorous coupled-wave formulation for the full three-dimensional structures of typical laser devices. Numerical examples based on our model are presented for PC structures with different air-hole shapes. The accuracy of the results obtained is verified using three-dimensional finite-difference time-domain simulations.",1107.1772v1 2011-07-25,On the Role of the Running Coupling Constant in a Quark Model Analysis of T-odd TMDs,"We revisit the standard procedure to match non-perturbative models to perturbative QCD, using experimental data. The strong coupling constant plays a central role in the QCD evolution of parton densities. We will extend this procedure with a non-perturbative generalization of the QCD running coupling and use this new development to understand why perturbative treatments are working reasonably well in the context of hadronic models. Vice versa, this new procedure broadens the ways of analyzing the freezing of the running coupling constant.",1107.4880v1 2011-07-26,Bottle microresonator with actively stabilized evanescent coupling,"The evanescent coupling of light between a whispering-gallery-mode bottle microresonator and a sub-wavelength-diameter coupling fiber is actively stabilized by means of a Pound-Drever-Hall technique. We demonstrate the stabilization of a critically coupled resonator with a control bandwidth of 0.1 Hz, yielding a residual transmission of (9 \pm 3) \times 10^-3 for more than an hour. Simultaneously, the frequency of the resonator mode is actively stabilized.",1107.5249v2 2011-07-29,Strong plasmon coupling between two gold nanospheres on a gold slab,"In this work, the plasmon coupling effect between two gold nanospheres on a gold slab is investigated. At plasmon resonance frequencies, electrons on the surface of the slab are absorbed into spheres and contribute to plasmon oscillation. This effect can help enhance the local electric field and optical coupling force between the two spheres.",1107.5939v1 2011-08-01,Charge redistribution and interlayer coupling in twisted bilayer graphene under electric fields,"We investigate the electronic density redistribution of rotated bilayer graphene under a perpendicular electric field, showing that the layers are actually coupled even for large angles. This layer-layer coupling is evidenced by the charge transfer on these structures as a function of the external voltage. We find an inhomogeneous excess charge distribution that is related to the moir\'e patterns for small angles, but that persists for larger angles where the carriers' velocity is equal to that of single layer graphene. Our results show that rotated bilayer systems are coupled for all rotation angles.",1108.0395v1 2011-08-02,Critical optical coupling between a GaAs disk and a nanowaveguide suspended on the chip,"We report on an integrated GaAs disk/waveguide system. A millimeter-long waveguide is suspended and tapered on the chip over a length of 25 {\mu}m to evanescently couple to high Q optical whispering gallery modes of a GaAs disk. The critical coupling regime is obtained both by varying the disk/guide gap distance and the width of the suspended nanoscale taper. The experimental results are in good agreement with predictions from the coupled mode theory.",1108.0680v1 2011-08-09,Microcavities coupled to multilevel atoms,"A three-level atom in the $\Lambda$-configuration coupled to a microcavity is studied. The two transitions of the atom are assumed couple to different counterpropagating mode pairs in the cavity. We analyze the dynamics both, in the strong-coupling and the bad cavity limit. We find that compared to a two-level setup, the third atomic state and the additional control field modes crucially modify the system dynamics and enable more advanced control schemes. All results are explained using appropriate dressed state and eigenmode representations. As potential applications, we discuss optical switching and turnstile operations and detection of particles close to the resonator surface.",1108.1931v1 2011-08-10,"Erratum: Engineering a p+ip Superconductor: Comparison of Topological Insulator and Rashba Spin-Orbit Coupled Materials [Phys. Rev. B 83, 184520 (2011)]","In this erratum, we revisit the issue of bulk-disorder on proposals to realize an effective p+ip superconductor from spin-orbit coupled materials. Contrary to the claim in [Phys. Rev. B 83, 184520 (2011)], we show that the pair breaking effects of bulk-disorder are negligible, and that bulk disorder does not suppress the induced superconductivity. This argument does not apply to our conclusions regarding impurities residing in the spin-orbit coupled material or disorder at the interface to the bulk superconductor, both of which tend to suppress superconductivity unless spin-orbit coupling is large.",1108.2260v1 2011-08-20,On optimal stationary couplings between stationary processes,"By a classical result of Gray, Neuhoff and Shields (1975) the $\bar\varrho$ distance between stationary processes is identified with an optimal stationary coupling problem of the corresponding stationary measures on the infinite product spaces. This is a modification of the optimal coupling problem from Monge--Kantorovich theory. In this paper we derive some general classes of examples of optimal stationary couplings which allow to calculate the $\bar\varrho$ distance in these cases in explicit form. We also extend the $\bar\varrho$ distance to random fields and to general nonmetric distance functions and give a construction method for optimal stationary $\bar c$-couplings. Our assumptions need in this case a geometric positive curvature condition.",1108.4086v1 2011-08-31,A Maxwell field minimally coupled to torsion,"We consider the Lagrangian density for a free Maxwell field, in which the electromagnetic field tensor minimally couples to the affine connection, in the Einstein-Cartan-Sciama-Kibble theory of gravity. We derive the formulae for the torsion and electromagnetic field tensors in terms of the electromagnetic potential. The divergence of the magnetic field does not vanish: the photon-torsion coupling acts like an effective magnetic monopole density. Such a coupling, which breaks U(1) gauge invariance, is significant only at extremely high energies existing in the very early Universe or inside black holes. It may, however, provide a mechanism for Dirac's quantization of electric charge.",1108.6100v1 2011-09-08,Mixed Ising ferrimagnets with next-nearest neighbour couplings on square lattices,"We study Ising ferrimagnets on square lattices with antiferromagnetic exchange couplings between spins of values S=1/2 and S=1 on neighbouring sites, couplings between S=1 spins at next--nearest neighbour sites of the lattice, and a single--site anisotropy term for the S=1 spins. Using mainly ground state considerations and extensive Monte Carlo simulations, we investigate various aspects of the phase diagram, including compensation points, critical properties, and temperature dependent anomalies. In contrast to previous belief, the next--nearest neighbour couplings, when being of antiferromagnetic type, may lead to compensation points.",1109.1709v1 2011-10-04,Spin-orbit-coupled dipolar Bose-Einstein condensates,"We propose an experimental scheme to create spin-orbit coupling in spin-3 Cr atoms using Raman processes. Employing linear Zeeman effect and optical Stark shift, two spin states within the ground electronic manifold are selected, which results in a pseudo-spin-1/2 model. We further study the ground state structures of a spin-orbit-coupled Cr condensate. We show that, in addition to the stripe structures induced by the spin-orbit coupling, the magnetic dipole-dipole interaction gives rise to the vortex phase, in which spontaneous spin vortex is formed.",1110.0558v3 2011-10-28,Artificial spin-orbit coupling in ultra-cold Fermi superfluids,"We develop a theory for interacting fermions in the presence of spin-orbit coupling and Zeeman fields, and show that many new superfluids phases, which are topological in nature, emerge. Depending on values of spin-orbit coupling, Zeeman fields, and interactions, initially gapped s-wave superfluids acquire p-wave, d-wave, f-wave and higher angular momentum components, which produce zeros in the excitation spectrum, rendering the superfluid gapless. Several multi-critical points, which separate topological superfluid phases from normal or non-uniform, are accessible depending on spin-orbit coupling, Zeeman fields or interactions, setting the stage for the study of tunable topological superfluids.",1110.6364v1 2011-12-14,Geometric entangling gates for coupled cavity system in decoherence-free subspaces,"We propose a scheme to implement geometric entangling gates for two logical qubits in a coupled cavity system in decoherence-free subspaces. Each logical qubit is encoded with two atoms trapped in a single cavity and the geometric entangling gates are achieved by cavity coupling and controlling the external classical laser fields. Based on the coupled cavity system, the scheme allows the scalability for quantum computing and relaxes the requirement for individually addressing atoms.",1112.3133v1 2011-12-15,Synchronization of Micromechanical Oscillators Using Light,"Synchronization, the emergence of spontaneous order in coupled systems, is of fundamental importance in both physical and biological systems. We demonstrate the synchronization of two dissimilar silicon nitride micromechanical oscillators, that are spaced apart by a few hundred nanometers and are coupled through optical radiation field. The tunability of the optical coupling between the oscillators enables one to externally control the dynamics and switch between coupled and individual oscillation states. These results pave a path towards reconfigurable massive synchronized oscillator networks.",1112.3636v2 2011-12-27,Synthetic 3D Spin-Orbit Coupling,"We describe a method for creating a three-dimensional analogue to Rashba spin-orbit coupling in systems of ultracold atoms. This laser induced coupling uses Raman transitions to link four internal atomic states with a tetrahedral geometry, and gives rise to a Dirac point that is robust against environmental perturbations. We present an exact result showing that such a spin-orbit coupling in a fermionic system always rise to a molecular bound state.",1112.6022v2 2012-02-06,Segregation and symmetry breaking of strongly coupled two-component Bose-Einstein condensates in a harmonic trap,"We study ground states of two-component condensates in a harmonic trap. We prove that in the strongly coupled and weakly interacting regime, the two components segregate while a symmetry breaking occurs. More precisely, we show that when the intercomponent coupling strength is very large and both intracomponent coupling strengths are small, each component is close to the positive or the negative part of a second eigenfunction of the harmonic oscillator in $\R^2$. As a result, the supports of the components approach complementary half-spaces, and they are not radially symmetric.",1202.1079v1 2012-02-13,Construction and separability of nonlinear soliton integrable couplings,"A very natural construction of integrable extensions of soliton systems is presented. The extension is made on the level of evolution equations by a modification of the algebra of dynamical fields. The paper is motivated by recent works of Wen-Xiu Ma et al. (Comp. Math. Appl. 60 (2010) 2601, Appl. Math. Comp. 217 (2011) 7238), where new class of soliton systems, being nonlinear integrable couplings, was introduced. The general form of solutions of the considered class of coupled systems is described. Moreover, the decoupling procedure is derived, which is also applicable to several other coupling systems from the literature.",1202.2682v1 2012-02-24,Phase locking dynamics of dipolarly coupled vortex-based spin transfer oscillators,"Phase locking dynamics of dipolarly coupled vortices excited by spin-polarized current in two identical nanopillars is studied as a function of the interpillar distance L. Numerical study and analytical model have proved the remarkable efficiency of magneto-static interaction to achieve phase locking. Investigating the dynamics in the transient regime towards phase locking, we extract the evolution of the locking time \tau, the coupling strength {\mu} and the interaction energy W. Finally, we compare this coupling energy with the one obtained by simple model.",1202.5499v1 2012-02-26,Hopping-resolved electron-phonon coupling in bilayer graphene,"In this paper we investigate the electron-phonon coupling in bilayer graphene, as a paradigmatic case for multilayer graphenes where interlayer hoppings are relevant. Using a frozen-phonon approach within the context of Density Functional Theory (DFT) and using different optical phonon displacements we are able to evaluate quantitatively the electron-phonon coupling $\alpha_i$ associated with each hopping term $\gamma_i$. This analysis also reveals a simple scaling law between the hopping terms $\gamma_i$ and the electron-phonon coupling $\alpha_i$ which goes beyond the specific DFT technique employed.",1202.5786v1 2012-03-15,Decoherence effect on the Fano lineshapes in double quantum dots coupled between normal and superconducting leads,"We investigate the Fano-type spectroscopic lineshapes of the T-shape double quantum dot coupled between the conducting and superconducting electrodes and analyze their stability on a decoherence. Because of the proximity effect the quantum interference patterns appear simultaneously at +/- epsilon_2, where epsilon_2 is an energy of the side-attached quantum dot. We find that decoherence gradually suppresses both such interferometric structures. We also show that at low temperatures another tiny Fano-type structure can be induced upon forming the Kondo state on the side-coupled quantum dot due to its coupling to the floating lead.",1203.3393v1 2012-03-16,Computational aspects of nuclear coupled-cluster theory,"We discuss computational aspects of the spherical coupled-cluster method specific to the nuclear many-body problem. Using chiral nucleon-nucleon interaction at next-to-next-to-next-to leading order (N3LO) with cutoff Lambda = 500MeV, we present coupled-cluster results for the ground state of 40Ca. Scaling and performance studies are presented together with challenges we meet with when extending the coupled-cluster effort to nuclei mass hundred and beyond.",1203.3765v1 2012-03-20,Quasiattractors in coupled maps and coupled dielectric cavities,"We study the origin of attracting phenomena in the ray dynamics of coupled optical microcavities. To this end we investigate a combined map that is composed of standard and linear map, and a selection rule that defines when which map has to be used. We find that this system shows attracting dynamics, leading exactly to a quasiattractor, due to collapse of phase space. For coupled dielectric disks, we derive the corresponding mapping based on a ray model with deterministic selection rule and study the quasiattractor obtained from it. We also discuss a generalized Poincar\'e surface of section at dielectric interfaces.",1203.4316v1 2012-03-28,Sommerfeld Enhancement from Multiple Mediators,"We study the Sommerfeld enhancement experienced by a scattering object that couples to a tower of mediators. This can occur in, e.g., models of secluded dark matter when the mediator scale is generated naturally by hidden-sector confinement. Specializing to the case of a confining CFT, we show that off-resonant values of the enhancement can be increased by ~ 20% for cases of interest when (i) the (strongly-coupled) CFT admits a weakly-coupled dual description and (ii) the conformal symmetry holds up to the Planck scale. Larger enhancements are possible for lower UV scales due to an increase in the coupling strength of the tower.",1203.6341v2 2012-06-04,Synchronization of coupled neural oscillators with heterogeneous delays,"We investigate the effects of heterogeneous delays in the coupling of two excitable neural systems. Depending upon the coupling strengths and the time delays in the mutual and self-coupling, the compound system exhibits different types of synchronized oscillations of variable period. We analyze this synchronization based on the interplay of the different time delays and support the numerical results by analytical findings. In addition, we elaborate on bursting-like dynamics with two competing timescales on the basis of the autocorrelation function.",1206.0789v1 2012-06-11,Synchronization in the presence of distributed delays,"We study systems of identical coupled oscillators introducing a distribution of delay times in the coupling. For arbitrary network topologies, we show that the frequency and stability of the fully synchronized states depend only on the mean of the delay distribution. However, synchronization dynamics is sensitive to the shape of the distribution. In the presence of coupling delays, the synchronization rate can be maximal for a specific value of the coupling strength.",1206.2288v2 2012-06-27,Graphene p-n junctions with nonuniform Rashba spin-orbit coupling,"Linear conductance of graphene-based p-n junctions with Rashba spin-orbit coupling is considered theoretically. A square potential step is used to model the junctions, while the coupling is introduced in terms of the Kane-Mele model (C.L. Kane and E.J. Mele, Phys.Rev.Lett. 95, 226801(2005)). The main objective is a description of electronic transport in junctions where Rashba parameter is nonuniform. Such a nonuniformity can appear when graphene is asymmetrically covered with atomic layers, or when Rashba coupling is strongly dependent on electric field. It is shown that conductance is significantly modified by the considered nonuniformity, which is most clearly manifested by an anomalous minimum at a certain potential step height.",1206.6503v1 2012-07-17,Coupled quantum oscillators within independent quantum reservoirs,"System of the quantum Langevin equations for two quantum coupling oscillators within independent heat baths of quantum oscillators are obtained using a model Hamiltonian and corresponding Heisenberg equations of motion. Expressions for mean energy of coupled oscillators and their mean energy of interaction are derived and analyzed. Nonmonotonic dependence of the interaction energy versus a coupling constant is demonstrated and explained. Nontrivial dependence of the quantities as a consequence of the difference in temperatures of heat baths is shown.",1207.3881v1 2012-07-23,Synthetic spin-orbit coupling in ultracold $Λ$-type atoms,"We consider the simulation of non-abelian gauge potentials in ultracold atom systems with atom-field interaction in the $\Lambda$ configuration where two internal states of an atom are coupled to a third common one with a detuning. We find the simulated non-abelian gauge potentials can have the same structures as those simulated in the tripod configuration if we parameterize Rabi frequencies properly, which means we can design spin-orbit coupling simulation schemes based on those proposed in the tripod configuration. We show the simulated spin-orbit coupling in the $\Lambda$ configuration can only be of a form similar to $p_{x}\sigma_{y}$ even when the Rabi frequencies are not much smaller than the detuning.",1207.5369v1 2012-07-26,Weyl meson and its implications in collider physics and cosmology,"Local scale invariant theory leads to the existence of a new particle called the Weyl vector meson. We study a generalized Standard Model, which displays local scale invariance. The model contains a real scalar field, besides the Higgs multiplet and coupling between the Higgs and Weyl meson. For certain range of coupling parameters, the Weyl-Higgs coupling leads to interesting phenomenon in particle colliders as well as in cosmology. Here we study the signature of the Weyl meson in particle colliders and determine the range of coupling parameters for which it can solve the dark matter problem.",1207.6195v2 2012-08-07,A proposal for realizing a 3-qubit controlled-phase gate with superconducting qubit systems coupled to a cavity,"We present a way to realize a 3-qubit quantum controlled-phase gate with superconducting qubit systems coupled to a cavity. This proposal does not require adjustment of the qubit level spacings or identical qubit-cavity coupling constants. Moreover, since only a resonant interaction is applied, the gate can be performed fast, within $\sim $ 10 nanosecond. This proposal is quite general, which can be applied to various types of superconducting qubits, atoms trapped in a cavity, or quantum dots coupled to a resonator.",1208.1345v1 2012-08-16,States of Enhanced Activity in a Network of Pulse Coupled Oscillators with Dynamic Coupling,"We investigate states of enhanced activity in a biological neuronal network composed of pulse-coupled oscillators. The synaptic couplings between the neurons are dynamic, modeling spike time dependent plasticity. The network exhibits statistical characteristics which recently have been identified in an analysis of epileptic seizures [Osorio et al., Phys. Rev. E 82, 021919(2010)] based on analogies to the onset of earth quakes.",1208.3354v1 2012-08-21,Finite element modeling of coupled optical microdisk resonators for displacement sensing,"We analyze normal mode splitting in a pair of vertically coupled microdisk resonators. A full vectorial finite element model is used to find the eigen frequencies of the symmetric and antisymmetric composite modes as a function of coupling distance. We find that the coupled microdisks can compete with the best Fabry-Perot resonators in displacement sensing. We also show how we configured FreeFem++ for the sphere eigenvalue problem.",1208.4320v2 2012-08-30,Robust Stability of Quantum Systems with a Nonlinear Coupling Operator,"This paper considers the problem of robust stability for a class of uncertain quantum systems subject to unknown perturbations in the system coupling operator. A general stability result is given for a class of perturbations to the system coupling operator. Then, the special case of a nominal linear quantum system is considered with non-linear perturbations to the system coupling operator. In this case, a robust stability condition is given in terms of a scaled strict bounded real condition.",1208.6061v1 2012-09-04,Quantum nanostructures in strongly spin-orbit coupled two-dimensional systems,"Recent progress in experimental studies of low-dimensional systems with strong spin-orbit coupling poses a question on the effect of this coupling on the energy spectrum of electrons in semiconductor nanostructures. It is shown in the paper that this effect is profound in the strong coupling limit. In circular quantum dots a soft mode develops, in strongly elongated dots electron spin becomes protected from the effects of the environment, and the lower branch of the energy spectrum of quantum wires becomes nearly flat in a wide region of the momentum space.",1209.0828v1 2012-09-13,Beam Dynamics in a Double-Channel Waveguide with Gain and Loss,"A double-channel waveguide with gain and loss is addressed and the corresponding coupled-mode equations are established by employing the coupled mode approach. Based on the coupled-mode equations, the beam dynamics in the double-channel waveguide with gain and loss is investigated, and the results show that there exist three distinct dynamical behaviors, which are amplification, attenuation to zero and tending to a steady value (or equilibrium state), respectively. Finally, it is shown that the theoretical results suggested by the coupled-mode equations agree well with the numerical simulations.",1209.2762v1 2012-09-21,Adiabatic pumping through an interacting quantum dot with spin-orbit coupling,"We study adiabatic pumping through a two-level quantum dot with spin-orbit coupling. Using a diagrammatic real-time approach, we calculate both the pumped charge and spin for a periodic variation of the dot's energy levels in the limit of weak tunnel coupling. Thereby, we compare the two limits of vanishing and infinitely large charging energy on the quantum dot. We discuss the dependence of the pumped charge and pumped spin on gate voltages, the symmetry in the tunnel-matrix elements and spin-orbit coupling strength. We identify the possibility to generate pure spin currents in the absence of charge currents.",1209.4770v2 2012-09-26,Low temperature acoustic polaron localization,"We calculate the low temperature properties of an acoustic polaron in three dimensions in thermal equilibrium at a given temperature using a specialized path integral Monte Carlo method. In particular we find numerical evidence that the chosen Hamiltonian for the acoustic polaron describes a phase transition from a localized state to an unlocalized state for the electron as the phonons-electron coupling constant decreases. The phase transition manifests itself with a jump discontinuity in the potential energy as a function of the coupling constant. In the weak coupling regime the electron is in an extended state whereas in the strong coupling regime it is found in a self-trapped state.",1209.5975v1 2012-10-04,QED with chiral nonminimal coupling: aspects of the Lorentz-violating quantum corrections,"An effective model for QED with the addition of a nonminimal coupling with a chiral character is investigated. This term, which is proportional to a fixed 4-vector $b_\mu$, violates Lorentz symmetry and may originate a CPT-even Lorentz breaking term in the photon sector. It is shown that this Lorentz breaking CPT-even term is generated and that,in addition, the chiral nonminimal coupling requires this term is present from the beginning. The nonrenormalizability of the model is invoked in the discussion of this fact and the result is confronted with the one from a model with a Lorentz-violating nonminimal coupling without chirality.",1210.1552v1 2012-10-08,Thermal emission in the ultrastrong coupling regime,"We study thermal emission of a cavity quantum electrodynamic system in the ultrastrong-coupling regime where the atom-cavity coupling rate becomes comparable the cavity resonance frequency. In this regime, the standard descriptions of photodetection and dissipation fail. Following an approach that was recently put forward by Ridolfo et al.[arXiv:1206.0944], we are able to calculate the emission of systems with arbitrary strength of light matter interaction, by expressing the electric field operator in the cavity-emitter dressed basis. Here we present thermal photoluminescence spectra, calculated for given temperatures and for different couplings in particular for available circuit QED parameters.",1210.2318v1 2012-10-10,New Two-Componet Coupled KdV Equation and its Connection with the Generalized Harry Dym Equation,"It is shown that, two different Lax operators in the Dym hierarchy, produce two generalized coupled Harry Dym equations. These equations transform, via the reciprocal link, to the coupled two-component KdV system. The first equation gives us new integrable two-component KdV system while the second reduces to the known symmetrical two-component KdV equation. For this new two-component coupled KdV system the Lax representation and Hamiltonian structure is defined.",1210.2819v2 2012-10-11,Anomalous Wtb couplings in gamma-proton collision at the LHC,"We study the possibility for the process $pp \rightarrow p\gamma p \rightarrow pW^-t(W^+\bar t)X$ with anomalous Wtb couplings in a model independent effective Lagrangian approach at the LHC. We find 95% confidence level bounds on the anomalous coupling parameters for various values of the integrated luminosity. The improved constraints on the anomalous Wtb couplings have been obtained compared to current limits.",1210.3235v1 2012-10-15,Highly efficient optical filter based on vertically coupled Photonic crystal cavity and bus waveguide,"We experimentally demonstrate a new optical filter design based on a vertically coupled photonic crystal cavity and a bus waveguide monolithically integrated on the silicon on insulator platform. The use of a vertically coupled waveguide gives flexibility in the choice of the waveguide material and dimensions, dramatically lowering the insertion loss while achieving very high coupling efficiencies to wavelength scale resonators",1210.4138v1 2012-10-16,Strong coupling of in-plane plasmon modes and their control,"We show anti-crossings due to strong in-plane coupling of plasmon modes in dielectric-metal-dielectric structure with top 2D dielectric pattern. Experimentally measured anti-crossing widths are compared with those calculated by coupled mode theory. It is shown that the coupling strength of the plasmon modes can be controlled by the orientation of the sample.",1210.4252v1 2012-10-26,Coupling limit order books and branching random walks,"We consider a model for a one-sided limit order book proposed by Lakner et al. We show that it can be coupled with a branching random walk and use this coupling to answer a non-trivial question about the long-term behavior of the price. The coupling relies on a classical idea of enriching the state-space by artificially creating a filiation, in this context between orders of the book, that we believe has the potential of being useful for a broader class of models.",1210.7062v3 2012-10-31,Heavy Quark Production and Energy Loss,"Heavy flavor research is a vigorous and active topic in high-energy QCD physics. Comparing theoretical predictions to data as a function of flavor provides a unique opportunity to tease out properties of quark-gluon plasma. We explicitly demonstrate this utility with energy loss predictions based on the assumption of 1) a weakly-coupled plasma weakly coupled to a high-pT probe using pQCD and 2) a strongly-coupled plasma strongly coupled to a high-pT probe using AdS/CFT; we find that while the former enjoys broad qualitative agreement with data, it is difficult to reconcile the latter with experimental measurements.",1210.8330v1 2012-11-13,Anomalous quartic ZZgammagamma couplings in gamma-proton collision at the LHC,"We investigate the constraints on the anomalous quartic $ZZ\gamma\gamma$ couplings through the process $p p\to p\gamma p\to p \gamma q Z X$ at the LHC. Taking into consideration various forward detector acceptances and integrated LHC luminosities, we find 95% confidence level bounds on the anomalous coupling parameters. We show that the bounds on these couplings are at the order of $10^{-6}GeV^{-2}$ which are about four orders of magnitude more restricted with respect to current experimental bounds.",1211.3100v1 2012-11-14,The gradient flow running coupling scheme,"The Yang-Mills gradient flow in finite volume is used to define a running coupling scheme. As our main result the discrete beta-function, or step scaling function, is calculated for scale change s=3/2 at several lattice spacings for SU(3) gauge theory coupled to N_f = 4 fundamental massless fermions. The continuum extrapolation is performed and agreement is found with the continuum perturbative results for small renormalized coupling. The case of SU(2) gauge group is briefly commented on.",1211.3247v1 2012-11-23,The effect of isoscalar-isovector coupling in infinite nuclear matter,"Working on the framework of Relativistic Mean Field theory, we exposed the effect of nonlinear isoscalar-isovector coupling on G2 parameter set on the density dependence of nuclear symmetry energy in infinite nuclear matter. The observables like symmetric energy and few related coefficients are studied systematically. We presented the results of stiff symmetry energy at sub-saturation densities and a soft variation at normal densities. Correlation between the symmetric energy and the isoscalar-isovector coupling parameter fully demonstrated for wide range of density. The work further extended to the octet system and showed the effect of coupling over the equation of state.",1211.5461v1 2012-12-11,Stability of symmetric and nonsymmetric FEM-BEM couplings for nonlinear elasticity problems,"We consider symmetric as well as non-symmetric coupling formulations of FEM and BEM in the frame of nonlinear elasticity problems. In particular, the Johnson-N\'ed\'elec coupling is analyzed. We prove that these coupling formulations are well-posed and allow for unique Galerkin solutions if standard discretizations by piecewise polynomials are employed. Unlike prior works, our analysis does neither rely on an interior Dirichlet boundary to tackle the rigid body motions nor on any assumption on the mesh-size of the discretization used.",1212.2620v1 2012-12-26,Ultrastrong coupling in a scalable design for circuit QED with superconducting flux qubits,"We theoretically study a circuit quantum electrodynamics (QED) architecture with superconducting flux qubits. The qubit is coupled to the transmission line resonator by an ac current originating from the current mode of the resonator. Ultrastrong coupling can be obtained by varying the capacitance between the qubit and the resonator. We propose a scalable design where the two-qubit coupling can be achieved.",1212.6181v3 2013-01-02,Coherence and pattern formation in coupled logistic-map lattices,"Three quantitative measures of the spatiotemporal behavior of the coupled map lattices: reduced density matrix, reduced wave function, and an analog of particle number, have been introduced. They provide a quantitative meaning to the concept of coherence which in the context of complex systems have been used rather intuitively. Their behavior suggests that the logistic coupled-map lattices approach the states which resemble the condensed states of systems of Bose particles. In addition, pattern formation in two-dimensional coupled map lattices based on the logistic mapping has been investigated with respect to the non-linear parameter, the diffusion constant and initial as well as boundary conditions.",1301.0231v2 2013-01-03,Faddeev-Popov ghosts in quantum gravity beyond perturbation theory,"We study the Faddeev-Popov ghost sector of asymptotically safe quantum gravity, which becomes non-perturbative in the ultraviolet. We point out that nonzero matter-ghost couplings and higher-order ghost self-interactions exist at a non-Gaussian fixed point for the gravitational couplings, i.e., in the ultraviolet. Thus the ghost sector in this non-perturbative ultraviolet completion does not keep the structure of a simple Faddeev-Popov determinant. We discuss implications of the new ghost couplings for the Renormalization Group flow in gravity, the form of the ultraviolet completion, and the relevant couplings, i.e., free parameters, of the theory.",1301.0632v2 2013-01-07,Eddington inspired Born Infeld Theory: A new look to the matter-coupling paradigm,"We discuss some of the consequences of changing the matter to gravity coupling without affecting the gravitational dynamics. The Einstein tensor is usually assumed to be proportional to the stress tensor due to the divergence free property of both object. This is not the only consistent way to couple matter to gravity; we explore some aspect of consistent modification to the matter/gravity coupling using the recently proposed Eddington inspired Born Infeld extension of gravity.",1301.1233v2 2013-01-16,Vortex lattice solutions to the Gross-Pitaevskii equation with spin-orbit coupling in optical lattices,"Effective spin-orbit coupling can be created in cold atom systems using atom-light interaction. We study the BECs in an optical lattice using the Gross-Pitaevskii equation with spin-orbit coupling. Bloch states for the linear equation are numerically obtained, and compared with stationary solutions to the Gross-Pitaevskii equation with nonlinear terms. Various vortex lattice states are found when the spin-orbit coupling is strong.",1301.3565v1 2013-01-16,Experimental Observations of Group Synchrony in a System of Chaotic Optoelectronic Oscillators,"We experimentally demonstrate group synchrony in a network of four nonlinear optoelectronic oscillators with time-delayed coupling. We divide the nodes into two groups of two each, by giving each group different parameters and by enabling only inter-group coupling. When coupled in this fashion, the two groups display different dynamics, with no isochronal synchrony between them, but the nodes in a single group are isochronally synchronized, even though there is no intra-group coupling. We compare experimental behavior with theoretical and numerical results.",1301.3827v2 2013-01-16,Stability of solutions of certain extended Ricci flow systems,"We consider four extended Ricci flow systems---that is, Ricci flow coupled with other geometric flows---and prove dynamical stability of certain classes of stationary solutions of these flows. The systems include Ricci flow coupled with harmonic map flow (studied abstractly and in the context of Ricci flow on warped products), Ricci flow coupled with both harmonic map flow and Yang-Mills flow, and Ricci flow coupled with heat flow for the torsion of a metric-compatible connection. The methods used to prove stability follow a program outlined by Guenther, Isenberg, and Knopf, which uses maximal regularity theory for quasilinear parabolic systems and a result of Simonett.",1301.3945v2 2013-01-17,Lattice Study of the Extent of the Conformal Window in Two-Color Yang-Mills Theory,"We perform a lattice calculation of the Schr\""odinger functional running coupling in SU(2) Yang-Mills theory with six massless Wilson fermions in the fundamental representation. The aim of this work is to determine whether the above theory has an infrared fixed point. Due to sensitivity of the $SF$ renormalized coupling to the tuning of the fermion bare mass we were unable to reliably extract the running coupling for stronger bare couplings.",1301.4141v1 2013-01-17,Gravitational- and Self- Coupling of Partially Massless Spin 2,"We show that higher spin systems specific to cosmological spaces are subject to the same problems as models with Poincar'e limits. In particular, we analyse partially massless (PM) spin 2 and find that both its gravitational coupling and nonlinear extensions suffer from the usual [background- and self-coupling] difficulties: Consistent free field propagation does not extend beyond background Einstein geometries. Then, using conformal Weyl gravity (CG), which consists of relative ghost PM and graviton excitations, we find that avoiding graviton-ghosts restricts CG-generated PM self-couplings to the usual, safe, Noether current cubic ones.",1301.4181v1 2013-01-25,On the origin and movement of the poles in the coupled channels model for $\bar{K}N$ interactions,"The origin of the poles generated by chiral coupled-channel dynamics and applied to $\bar{K}N$ interactions is related to the nonzero diagonal couplings in the $\pi\Sigma$, $\bar{K}N$ and $K\Xi$ channels. An evolution of the poles from the zero coupling limit and from a limit of restored SU(3) symmetry is discussed.",1301.6032v1 2013-02-06,Multi-Dimensional Spatially-Coupled Codes,"Spatially-coupled (SC) codes are constructed by coupling many regular low-density parity-check codes in a chain. The decoding chain of SC codes stops when facing burst erasures. This problem can not be overcome by increasing coupling number. In this paper, we introduce multi-dimensional (MD) SC codes. Numerical results show that 2D-SC codes are more robust to the burst erasures than 1D-SC codes. Furthermore, we consider designing MD-SC codes with smaller rateloss.",1302.1510v1 2013-02-13,Semiconductor Ring Lasers Coupled by a Single Waveguide,"We experimentally and theoretically study the characteristics of semiconductor ring lasers bidirectionally coupled by a single bus waveguide. This configuration has, e.g., been suggested for use as an optical memory and as an optical neural network motif. The main results are that the coupling can destabilize the state in which both rings lase in the same direction, and it brings to life a state with equal powers at both outputs. These are both undesirable for optical memory operation. Although the coupling between the rings is bidirectional, the destabilization occurs due to behavior similar to an optically injected laser system.",1302.3113v1 2013-02-13,Transverse localization in nonlinear photonic lattices with second-order coupling,"We investigate numerically the effect of long-range interaction on the transverse localization of light. To this end, nonlinear zigzag optical waveguide lattices are applied, which allows precise tuning of the second-order coupling. We find that localization is hindered by coupling between next-nearest lattice sites. Additionally, (focusing) nonlinearity facilitates localization with increasing disorder, as long as the nonlinearity is sufficiently weak. However, for strong nonlinearities, increasing disorder results in weaker localization. The threshold nonlinearity, above which this anomalous result is observed grows with increasing second-order coupling.",1302.3124v1 2013-02-19,Classical Model for Jellium,"A simple, practical model for computing the equilibrium thermodynamics and structure of jellium by classical strong coupling methods is proposed. An effective pair potential and coupling constant are introduced, incorporating the ideal gas, low density, and weak coupling quantum limits. The resulting parameter free, analytic model is illustrated by the calculation of the pair correlation function over a wide range of temperatures and densities via strong coupling classical liquid state theory. The results compare favorably with the first finite temperature restricted path integral Monte Carlo simulations reported recently.",1302.4507v1 2013-02-22,Top couplings and top partners,"We review the model-independent description of the couplings of the top quark to the Higgs and gauge bosons in theories beyond the Standard Model. Then we examine these couplings in the case of arbitrary heavy vector-like quarks mixing with the third family. We also discuss the couplings of these top partners, and comment on implications for LHC searches.",1302.5634v1 2013-02-25,Strong Coupling to Two-Dimensional Anderson Localized Modes,"We use a scattering formalism to derive a condition of strong coupling between a resonant scatterer and an Anderson localized mode for electromagnetic waves in two dimensions. The strong coupling regime is demonstrated based on exact numerical simulations, in perfect agreement with theory. The strong coupling threshold can be expressed in terms of the Thouless conductance and the Purcell factor, thus connecting key concepts in transport theory and cavity quantum electrodynamics.",1302.6148v2 2013-03-03,Optomechanical Transductions in Single and Coupled Wheel Resonators,"In this report, the optomechanical transductions in both single and two side-coupled wheel resonators are investigated. In the single resonator, the optomechanical transduction sensitivity is determined by the optical and mechanical quality factors of the resonator. In the coupled resonators, the optomechanical transduction is related to the energy distribution in the two resonators, which is strongly dependent on the input detuning. Compared to a single resonator, the coupled resonators can still provide very sensitive optomechanical transduction even if the optical and mechanical quality factors of one resonator are degraded.",1303.0440v1 2013-03-11,Quintessence with Kaluza-Klein type couplings to matter and an isotropy-violating vector field,"We study the dynamics of a scalar field with Kaluza-Klein type couplings to cold dark matter and an isotropy-violating vector field. The vector coupling, $f^2(\phi)F^2$, has been studied thoroughly in the context of inflation recently. We generalize the model to a dark energy context and study the cosmological consequences. We find a rich set of exact anisotropic power-law solutions and identify a strong vector coupling regime where the anisotropy is controllable and all solutions are close to the LCDM limit.",1303.2469v1 2013-03-13,Single-photon coherent transparency in a coupled atoms-waveguide system,"We investigate the single-photon propagation in the one-dimensional waveguide coupled to $N$ two-level atoms. For a waveguide coupled to $N$ distant atoms, the transparency can be induced by coherent interaction at resonance for an $even$ $number$ of $N$, while for an $odd$ $number$ of $N$, the photon can be fully reflected. We then can switch the photon transport by controlling the atomic number. For a waveguide coupled to a small atomic ensemble of $N$ atoms in the same position, the transparency disappears, and the photonic transport property displays a jump behavior near the resonance point.",1303.3129v2 2013-04-05,Characterization of intra device mutual thermal coupling in multi finger SiGe:C HBTs,"This paper studies the mutual coupling in trench isolated multi emitter bipolar transistors fabricated in a Si/SiGe:C HBT technology STMicroelectronics featuring fT and fmax of ~300GHz and ~400GHz, respectively. Thermal coupling parameters are extracted using three dimensional (3D) thermal TCAD simulations. The obtained parameters are implemented in a distributed transistor model that considers self-heating as well as thermal coupling between emitter fingers. Very good agreement is achieved between circuit simulations and DC measurements carried out on an in house designed test structure.",1304.1781v1 2013-04-18,SUSY Extended Higgs Sector and SUSY Strong Dynamics,"We consider an extended Higgs sector that arises as a low-energy description of a strongly-coupled SUSY gauge theory. This model predicts the presence of extra superfields that couple with the Higgs superfields through large coupling constants. Large radiative corrections involving the extra fields can realize strongly first order electroweak phase transition, which is a vital requirement for electroweak baryogenesis scenario. At the same time, the large radiative corrections lead to significant deviations in the Higgs boson triple coupling and Higgs-to-diphoton branching ratio, which are testable at the ILC.",1304.5029v2 2013-04-22,Quantum mechanical study of a generic quadratically coupled optomechanical system,"Typical optomechanical systems involving optical cavities and mechanical oscillators rely on a coupling that varies linearly with the oscillator displacement. However, recently a coupling varying instead as the square of the mechanical displacement has been realized, presenting new possibilities for non-demolition measurements and mechanical squeezing. In this article we present a quantum mechanical study of a generic quadratic-coupling optomechanical Hamiltonian. First, neglecting dissipation, we provide analytical results for the dressed states, spectrum, phonon statistics and entanglement. Subsequently, accounting for dissipation, we supply a numerical treatment using a master equation approach. We expect our results to be of use to optomechanical spectroscopy, state transfer, wavefunction engineering, and entanglement generation.",1304.6130v1 2013-04-25,Array of Fabry-Pérot waveguide resonators with tunable coupling,"We demonstrate the elements of a coupled-resonator optical waveguide in a side-coupled Fabry-P\'erot configuration, and show that the coupling rate between adjacent waveguides can be widely tuned through the thermo-optic effect. The device is linearly scalable and can be combined with other integrated devices, with applications as an optical delay line or as a key element in a cavity-QED based quantum simulator.",1304.7013v1 2013-05-02,Photonic molecules formed by coupled hybrid resonators,"We describe a method that enables free-standing whispering-gallery-mode microresonators, and report spectral tuning of photonic molecules formed by coupled free and on-chip resonators with different geometries and materials. We study direct coupling via evanescent fields of free silica microtoroids and microspheres with on-chip polymer coated silica microtoroids. We demonstrate thermal tuning of resonance modes to achieve maximal spectral overlap, mode splitting induced by direct coupling, and the effects of distance between the resonators on the splitting spectra.",1305.0521v1 2013-05-06,Dissipative dynamics of atom-field entanglement in the ultrastrong-coupling regime,"The dynamics of atom-field entanglement for a system composed of two atoms resonantly coupled to a single mode leaky cavity field has been investigated beyond rotating wave approximation (RWA). By using monogamic relation for entanglement of formation (EOF) as well as the lower bound of EOF for bipartite mixed states in higher dimensions, contrary to the RWA case, the atom-field system in the steady states is found to be entangled in the strong-coupling regime and the entanglement can grow as a function of atom-field coupling strength.",1305.1110v2 2013-05-14,The method of coupled fixed points and coupled quasisolutions when working with ODE's with arguments of bounded variation,"The aim of this paper is to show the use of the coupled quasisolutions method as a useful technique when treating with ordinary differential equations with functional arguments of bounded variation. We will do this by looking for solutions for a first-order ordinary differential equation with an advanced argument of bounded variation. The main trick is to use the Jordan decomposition of this argument in a nondecreasing part and a nonincreasing one. As a necessary step, we will also talk about coupled fixed points of multivalued operators.",1305.3266v1 2013-05-17,Breakdown of a renormalized perturbation expansion around mode-coupling theory of the glass transition,"We analyze a renormalized perturbation expansion around the mode-coupling theory of the glass transition. We focus on the long-time limit of the irreducible memory function. We discuss a renormalized diagrammatic expansion for this function and re-sum two infinite classes of diagrams. We show that the resulting contributions to the irreducible memory function diverge at the mode-coupling transition. A further re-summation of ladder diagrams constructed by iterating these divergent contributions gives a finite result which cancels the mode-coupling theory's expression for the irreducible memory function.",1305.4136v2 2013-05-28,Nonlinear-dissipation-induced Entanglement of Coupled Nonlinear Oscillators,"The quantum dynamics of two weakly coupled nonlinear oscillators is analytically and numerically investigated in the context of nonlinear dissipation. The latter facilitates the creation and preservation of non-classical steady states. Starting from a microscopic description of two oscillators individually interacting with their dissipative environments, it is found that in addition to energy relaxation, dephasing arises due to the mutual coupling. Using the negativity as an entanglement measure, it is shown that the coupling entangles the oscillators in the long-time limit. For finite temperatures, entanglement sudden death and rebirth are observed.",1305.6514v2 2013-05-29,Multiple fluxon analogues and dark solitons in linearly coupled Bose-Einstein condensates,"Two effectively one-dimensional parallel coupled Bose-Einstein condensates in the presence of external potentials are studied. The system is modelled by linearly coupled Gross-Pitaevskii equations. In particular, the interactions of grey-soliton-like solutions representing analogues of superconducting Josephson fluxons as well as coupled dark solitons are discussed. A theoretical approximation based on variational formulations to calculate the oscillation frequency of the grey-soliton-like solution is derived and a qualitatively good agreement is obtained.",1305.6685v1 2013-05-30,Anomalous $tqγ$ couplings in $γp$ collision at the LHC,"We have examined the constraints on the anomalous $tq\gamma$ ($q=u,c$) couplings through the process $pp\to p\gamma p\to pWbX$ at the LHC by considering three forward detector acceptances: $0.0015< \xi < 0.5$, $0.0015< \xi <0.15$ and $0.1< \xi < 0.5$. The sensitivity bounds on the anomalous couplings have been obtained at the $95%$ confidence level in a model independent effective lagrangian approach. We have found that the bounds on these couplings can be highly improved compared to current experimental bounds.",1305.7096v3 2013-06-28,Quantum quasicrystals of spin-orbit coupled dipolar bosons,"We study quasi-two-dimensional dipolar Bose gases in which the bosons experience a Rashba spin-orbit coupling. We show that the degenerate dispersion minimum due to the spin-orbit coupling, combined with the long-range dipolar interaction, can stabilize a number of quantum crystalline and quasicrystalline ground states. Coupling the bosons to a fermionic species can further stabilize these phases. We estimate that the crystalline and quasicrystalline phases should be detectable in realistic dipolar condensates, e.g., dysprosium, and discuss their symmetries and excitations.",1307.0002v2 2013-07-01,Models of coupled dark matter to dark energy,"We present three distinct types of models of dark energy in the form of a scalar field which is explicitly coupled to dark matter. Our construction draws from the pull-back formalism for fluids and generalises the fluid action to involve couplings to the scalar field. We investigate the cosmology of each class of model both at the background and linearly perturbed level. We choose a potential for the scalar field and a specific coupling function for each class of models and we compute the Cosmic Microwave Background and matter power spectra.",1307.0458v2 2013-07-03,Almost Ballistic Transport for the Weakly Coupled Fibonacci Hamiltonian,"We prove estimates for the transport exponents associated with the weakly coupled Fibonacci Hamiltonian. It follows in particular that the upper transport exponent $\tilde \alpha^\pm_u$ approaches the value one as the coupling goes to zero. Moreover, for sufficiently small coupling, $\tilde \alpha^\pm_u$ strictly exceeds the fractal dimension of the spectrum.",1307.0925v2 2013-07-13,Strong coupling constant of vector bottomonium to the pseudoscalar and vector $B_c$ mesons via QCD sum rules,"The strong coupling constant $g_{\Upsilon B_c^{ps} B_c^V}$ is evaluated using the three-point QCD sum rules. The correlation functions used to calculate these strong coupling constants contain contributions of both $B_c^V$ and $B_c^{ps}$ mesons as off-shell states with contributions of two gluon condensates as a radiative corrections. The results, $g_{\Upsilon B_c^V B_c^{PS}}=1.67\pm 0.52 GeV^{-1}$ for $B_c^{Ps}$ off-shell and $g_{\Upsilon B_c^{PS}B_c^V}=(0.87\pm0.25) GeV^{-1}$ for $B_c^V$ off-shell are obtained for the relevant strong coupling constants",1307.3633v3 2013-07-30,Curvaton with nonminimal derivative coupling to gravity,"We show a curvaton model, in which the curvaton has a nonminimal derivative coupling to gravity. Thanks to such a coupling, we find that the scale-invariance of the perturbations can be achieved for arbitrary values of the equation-of-state of background, provided that it is nearly a constant. We also discussed about tensor perturbations, the local non-Gaussianities generated by the nonminimal derivative coupling curvaton model, as well as the adiabatic perturbations which are transferred from the field perturbations during the curvaton decay.",1307.7864v2 2013-10-01,Dimensional Crossover in Quasi-one-dimensional Spin-1 Heisenberg Antiferromagnets,"We study the quenching of the Haldane gap in quasi-one-dimensional systems of weakly coupled spin-1 antiferromagnetic Heisenberg chains. The critical interchain coupling Jc required to stabilize long range magnetic order can be accurately determined from large scale quantum Monte Carlo calculations. Several different geometries of coupled chains are studied, illustrating the dependence of Jc on the coordination of chains. For bipartite geometries, ferromagnetically coupled chains yield similar magnitudes for Jc.",1310.0130v1 2013-10-15,A universal attractor for inflation at strong coupling,"We introduce a novel non-minimal coupling between gravity and the inflaton sector. Remarkably, for large values of this coupling all models asymptote to a universal attractor. This behavior is independent of the original scalar potential and generalizes the attractor in the phi^4 theory with non-minimal coupling to gravity. The attractor is located in the `sweet spot' of Planck's recent results.",1310.3950v2 2013-10-15,DBI inflation with a non-minimally coupled Gauss-Bonnet term,"We study the inflation in a model with a Gauss-Bonnet term which is non-minimally coupled to a DBI field. We study the spectrum of the primordial perturbations in detail. The non-Gaussianity of this model is considered and the amplitude of the non-Gaussianity is studied in both the equilateral and orthogonal configurations. By taking various functions of the DBI field, inflaton potential and the Gauss-Bonnet coupling term, we test the model with observational data and find some constraints on the Gauss-Bonnet coupling parameter.",1310.3989v1 2013-10-16,Optical conductivity of a strong-coupling polaron,"The polaron optical conductivity is derived within the strong-coupling expansion, which is asymptotically exact in the strong-coupling limit. The polaron optical conductivity band is provided by the multiphonon optical transitions. The polaron optical conductivity spectra calculated within our analytic strong-coupling approach and the numerically accurate Diagrammatic Quantum Monte Carlo (DQMC) data are in a good agreement with each other at large $\alpha \gtrapprox 9$.",1310.4413v1 2013-10-28,Three-loop Standard Model effective potential at leading order in strong and top Yukawa couplings,"I find the three-loop contribution to the effective potential for the Standard Model Higgs field, in the approximation that the strong and top Yukawa couplings are large compared to all other couplings, using dimensional regularization with modified minimal subtraction. Checks follow from gauge invariance and renormalization group invariance. I also briefly comment on the special problems posed by Goldstone boson contributions to the effective potential, and on the numerical impact of the result on the relations between the Higgs vacuum expectation value, mass, and self-interaction coupling.",1310.7553v2 2013-11-04,Wireless energy transfer between anisotropic metamaterials shells,"The behavior of strongly coupled Radial Photonic Crystals shells is investigated as a potential alternative to transfer electromagnetic energy wirelessly. These sub-wavelength resonant microstructures, which are based on anisotropic metamaterials, can produce efficient coupling phenomena due to their high quality factor. A configuration of selected constitutive parameters (permittivity and permeability) is analyzed in terms of its resonant characteristics. The coupling to loss ratio between two coupled resonators is calculated as a function of distance, the maximum (in excess of 300) is obtained when the shells are separated by three times their radius. Under practical conditions an 83% of maximum power transfer has been also estimated.",1311.0727v1 2013-11-06,Taming Explosive Growth through Dynamic Random Links,"We study the dynamics of a collection of nonlinearly coupled limit cycle oscillators, relevant to systems ranging from neuronal populations to electrical circuits, under coupling topologies varying from a regular ring to a random network. We find that the trajectories of this system escape to infinity under regular coupling, for sufficiently strong coupling strengths. However, when some fraction of the regular connections are dynamically randomized, the unbounded growth is suppressed and the system always remains bounded. Further we determine the critical fraction of random links necessary for successful prevention of explosive behaviour, for different network rewiring time-scales. These results suggest a mechanism by which blow-ups may be controlled in extended oscillator systems.",1311.1544v1 2013-11-22,Stability and convergence analysis of the kinematically coupled scheme for fluid-structure interaction,"In this work we analyze the stability and convergence properties of a loosely-coupled scheme, called the kinematically coupled scheme, for interaction between an incompressible viscous fluid and a thin structure. We consider a benchmark problem where the structure is modeled using the linearly elastic Koiter membrane model and the coupling between the fluid and structure is linear. We derive the energy estimates associated with the unconditional stability and, for the first time, present a priori estimates showing optimal, first-order in time, convergence. The theoretical stability and convergence results are supported with numerical examples.",1311.5649v2 2013-11-22,Optimal preconditioning for the symmetric and non-symmetric coupling of adaptive finite elements and boundary elements,"We analyze a multilevel diagonal additive Schwarz preconditioner for the adaptive coupling of FEM and BEM for a linear 2D Laplace transmission problem. We rigorously prove that the condition number of the preconditioned system stays uniformly bounded, independently of the refinement level and the local mesh-size of the underlying adaptively refined triangulations. Although the focus is on the non-symmetric Johnson-N\'ed\'elec one-equation coupling, the principle ideas also apply to other formulations like the symmetric FEM-BEM coupling. Numerical experiments underline our theoretical findings.",1311.5782v1 2013-12-09,The Pairing of Spin-orbit Coupled Fermi Gas in Optical Lattice,"We investigate Rashba spin-orbit coupled Fermi gases in square optical lattice by using the determinant quantum Monte Carlo (DQMC) simulations which is free of the sign-problem. We show that the Berezinskii-Kosterlitz-Thoules phase transition temperature is firstly enhanced and then suppressed by spin-orbit coupling in the strong attraction region. In the intermediate attraction region, spin-orbit coupling always suppresses the transition temperature. We also show that the spin susceptibility becomes anisotropic and retains finite values at zero temperature.",1312.2292v1 2013-12-20,Heavy Probes in Strongly Coupled Plasmas With Chemical Potential,"We study the properties of heavy probes moving in strongly coupled plasmas at finite chemical potential. Using the gauge/gravity duality we consider large classes of gravity models consisting in deformed AdS5 spacetimes endowed with Reissner-Nordstr\""om-type black holes. We report on our analysis of the screening distance of a quark-antiquark pair, its free energy, and the running coupling. These observables show a certain insensitivity as to which model and deformation is used, pointing to strong-coupling universal behavior. Thus, the results may be relevant for modeling heavy quarkonia traversing a quark-gluon plasma at finite net baryon density, and their suppression by melting.",1312.5999v1 2014-01-03,Spin-Orbit Coupled Bose Gases at Finite Temperatures,"Spin-orbit coupling is predicted to have dramatic effects on thermal properties of a two-component atomic Bose gas. We show that in three spatial dimensions it lowers the critical temperature of condensation and enhances thermal depletion of the condensate fraction. In two dimensions we show that spin-orbit coupling destroys superfluidity at any finite temperature, modifying dramatically the cerebrated Berezinskii-Kosterlitz-Thouless scenario. We explain this by the increase of the number of low energy states induced by spin-orbit coupling, enhancing the role of quantum fluctuations.",1401.0575v1 2014-01-07,Vector inflation by kinetic coupled gravity,"Vector inflation is a newly established model where inflation is driven by non-minimally coupled massive vector fields with a potential term. This model is similar to the model of chaotic inflation with scalar fields, except that for vector fields the isotropy of expansion is achieved either by considering a triplet of orthogonal vector fields or $N$ randomly oriented independent vector fields. We introduce a new version of vector inflation where the vector field has no potential term but is non-minimally coupled to gravity through the kinetic term. The non-minimal coupling is established by introducing the Einstein tensor besides the metric tensor within the kinetic term of the vector field.",1401.1280v1 2014-01-17,Emergent Majorana Mass and Axion Couplings in Superfluids,"Axions (in the general sense) may acquire qualitatively new couplings inside superfluids. Their conventional couplings to fermions, in empty space, involve purely imaginary masses; the new couplings involve emergent Majorana masses. The possibility of weak links for axions, recently put forward, is analyzed, rejected, and replaced with a non-local analogue.",1401.4379v2 2014-02-18,Chimera-like states in an ensemble of globally coupled oscillators,"We demonstrate emergence of a complex state in a homogeneous ensemble of globally coupled identical oscillators, reminiscent of chimera states in locally coupled oscillator lattices. In this regime some part of the ensemble forms a regularly evolving cluster, while all other units irregularly oscillate and remain asynchronous. We argue that chimera emerges because of effective bistability which dynamically appears in the originally monostable system due to internal delayed feedback in individual units. Additionally, we present two examples of chimeras in bistable systems with frequency-dependent phase shift in the global coupling.",1402.4328v1 2014-02-25,No minimally coupled scalar black hole hair in Lanczos-Lovelock gravity,"We extend here the result of Bekenstein [1,2] proving the non-existence of minimally coupled scalar black hole hair in general relativity to the Lanczos-Lovelock gravity in arbitrary dimension with non-negative coupling constants. The only physical requirement on the multiplet of minimally coupled scalar fields is that it fulfills the weak energy condition. We also assume, similarly to Bekenstein, spherical symmetry and asymptotic flatness.",1402.6166v2 2014-04-06,Collective behavior of chaotic oscillators with environmental coupling,"We investigate the collective behavior of a system of chaotic Rossler oscillators indirectly coupled through a common environment that possesses its own dynamics and which in turn is modulated by the interaction with the oscillators. By varying the parameter representing the coupling strength between the oscillators and the environment, we find two collective states previously not reported in systems with environmental coupling: (i) nontrivial collective behavior, characterized by a periodic evolution of macroscopic variables coexisting with the local chaotic dynamics; and (ii) dynamical clustering, consisting of the formation of differentiated subsets of synchronized elements within the system. These states are relevant for many physical and biological systems where interactions with a dynamical environment are frequent.",1404.1625v1 2014-04-15,Finite time cooling in dispersively and dissipatively coupled optomechanics,"The cooling performance of an optomechanical system comprising both dispersive and dissipative coupling is studied. We present a scheme to cool a mechanical resonator to its ground state in finite time by employing a chirped pulse. When the cavity damping strength increases, the phonon occupation of the resonator will decrease. Moreover, the cooling behaviors of this dispersively and dissipatively coupled system with different incident pulses, different system coupling strengths are explored. Our scheme is feasible to cool the resonator in a wide parameter region.",1404.3851v2 2014-04-24,"Ultra-weak sector, Higgs boson mass, and the dilaton","The Higgs boson mass may arise from a portal coupling to a singlet field $\sigma$ which has a very large VEV $f \gg m_\text{Higgs}$. This requires a sector of ""ultra-weak"" couplings $\zeta_i$, where $\zeta_i \lesssim m_\text{Higgs}^2 / f^2$. Ultra-weak couplings are technically naturally small due to a custodial shift symmetry of $\sigma$ in the $\zeta_i \rightarrow 0$ limit. The singlet field $\sigma$ has properties similar to a pseudo-dilaton. We engineer explicit breaking of scale invariance in the ultra-weak sector via a Coleman-Weinberg potential, which requires hierarchies amongst the ultra-weak couplings.",1404.6268v1 2014-04-29,The Kuramoto model of coupled oscillators with a bi-harmonic coupling function,"We study synchronization in a Kuramoto model of globally coupled phase oscillators with a bi-harmonic coupling function, in the thermodynamic limit of large populations. We develop a method for an analytic solution of self-consistent equations describing uniformly rotating complex order parameters, both for single-branch (one possible state of locked oscillators) and multi-branch (two possible values of locked phases) entrainment. We show that synchronous states coexist with the neutrally linearly stable asynchronous regime. The latter has a finite life time for finite ensembles, this time grows with the ensemble size as a power law.",1404.7292v1 2014-07-07,Self-focused beams to couple light into a whispering-gallery mode resonator,"We propose an original method to couple light into a whispering-gallery mode resonator. This method benefits from the mode selectivity and robustness of the prism-coupling along with the single-mode propagation of the fiber taper. It consists in a prism shaped crystal with a waveguide inscribed inside it. The waveguide is self-inscribed in-situ by beam self-trapping to allow an optimum coupling to a given resonator.",1407.1599v1 2014-07-08,Assisted coupled quintessence,"We study models of quintessence consisting of a number of scalar fields coupled to several dark matter components. In the case of exponential potentials the scaling solutions can be described in terms of a single field. The corresponding effective logarithmic slope and effective coupling can be written in a simple form in terms of the individual slopes and couplings of the original fields. We also investigate solutions where the scalar potential is negligible, in particular those leading to transient matter dominated solutions. Finally, we compute the evolution equations for the linear perturbations which will allow these models to be tested against current and future observational data.",1407.2156v1 2014-08-03,Appearance of Boulware-Deser ghost in bigravity with doubly coupled matter,"We discuss the ghost freeness in the case when we add matter coupled to two metrics to the ghost-free bigravity. In this paper we show that the Boulware-Deser ghost generally revives in the presence of doubly coupled matter and that ghost freeness strongly restricts the model of kinetically doubly coupled matter. This result may anticipate difficulties in the attempt to derive the ghost-free bigravity as a low-energy effective theory, starting with a model applicable at high energies.",1408.0487v2 2014-08-12,Coupled Airy breathers,"The dynamics of two component coupled Airy beams is investigated. In the linear propagation regime a complete analytic solution describes breather like propagation of the two components featuring non-diffracting self-accelerating Airy behavior. The superposition of two beams with different input properties opens the possibility to design more complex non-diffracting propagation scenarios. In the strongly nonlinear regime the dynamics remains qualitatively robust as is revealed by direct numerical simulations. Due to the Kerr effect the two beams emit solitonic breathers, whose coupling period is compatible with the remaining Airy-like beams. The results of this study are relevant for the description of photonic and plasmonic beams propagating in coupled planar waveguides as well as for birefrigent or multi-wavelengths beams.",1408.2683v1 2014-08-14,Highly Efficient Mode Converter for Coupling Light into Wide Slot Photonic Crystal Waveguide,"We design, fabricate and experimentally demonstrate a highly efficient adiabatic mode converter for coupling light into a silicon slot waveguide with a slot width as large as 320nm. This strip-to-slot mode converter is optimized to provide a measured insertion loss as low as 0.08dB. Our mode converter provides 0.1dB lower loss compared to a conventional V-shape mode converter. This mode converter is used to couple light into and out of a 320nm slot photonic crystal waveguide, and it is experimentally shown to improve the coupling efficiency up to 3.5dB compared to the V-shape mode converter, over the slow-light wavelength region.",1408.3400v1 2014-09-08,Full hamiltonian structure for a parametric coupled Korteweg-de Vries system,"We obtain the full hamiltonian structure for a parametric coupled KdV system. The coupled system arises from four different real basic lagrangians. The associated hamiltonian functionals and the corresponding Poisson structures follow from the geometry of a constrained phase space by using the Dirac approach for constrained systems. The overall algebraic structure for the system is given in terms of two pencils of Poisson structures with associated hamiltonians depending on the parameter of the Poisson pencils. The algebraic construction we present admits the most general space of observables related to the coupled system.",1409.2418v1 2014-09-15,Switching of a Single Photon by Two Λ-type Three-Level Quantum Dots Embedded in Cavities Coupling to One-Dimensional Waveguide,"Switching of a single photon interacting with two {\Lambda}-type three-level quantum dots embedded in cavities coupled to one-dimensional waveguide is investigated theoretically via the real-space approach. We demonstrated that switching of a single photon can be achieved by tuning the classic driving field on or off, and by controlling the QD-cavity coupling strength, Rabi frequency and the cavity-waveguide coupling rate. The transmission properties of a single photon by such a nanosystem discussed here could find the applications in the design of next-generation quantum devices and quantum information.",1409.4636v1 2014-09-18,Coupling Reduces Noise,"We demonstrate how coupling nonlinear dynamical systems can reduce the effects of noise. For simplicity we investigate noisy coupled map lattices. Noise from different lattice nodes can diffuse across the lattice and lower the noise level of individual nodes. We develop a theoretical model that explains this observed noise evolution and show how the coupled dynamics can naturally function as an averaging filter. Our numerical simulations are in excellent agreement with the model predictions.",1409.5186v1 2014-10-28,Erosion of synchronization in networks of coupled oscillators,"We report erosion of synchronization in networks of coupled phase oscillators, a phenomenon where perfect phase synchronization is unattainable in steady-state, even in the limit of infinite coupling. An analysis reveals that the total erosion is separable into the product of terms characterizing coupling frustration and structural heterogeneity, both of which amplify erosion. The latter, however, can differ significantly from degree heterogeneity. Finally, we show that erosion is marked by the reorganization of oscillators according to their node degrees rather than their natural frequencies.",1410.7559v2 2014-11-03,Small neutrino masses and gauge coupling unification,"The physics responsible for gauge coupling unification may also induce small neutrino masses. We propose a novel gauge mediated radiative seesaw mechanism for calculable neutrino masses. These arise from quantum corrections mediated by new $SU(3)_c \times SU(2)_L \times U(1)_X$ (3-3-1) gauge bosons and the physics driving gauge coupling unification. Gauge couplings unify for a 3-3-1 scale in the TeV range, making the model directly testable at the LHC.",1411.0566v2 2014-11-13,BLF-SSH Polarons coupled to Acoustic Phonons in the Adiabatic limit,"We survey polaron formation in the BLF-SSH model using acoustic phonons in the adiabatic limit. Multiple different numerical optimization routines and strong coupling analytical calculations are used to find a robust ground state energy for a wide range of coupling strengths. The electronic configuration and accompanying ionic distortions of the polaron were determined, as well as a non-zero critical coupling strength for polaron formation in two and three dimensions.",1411.3635v1 2014-11-18,Active optomechanics through relaxation oscillations,"We propose an optomechanical laser based on III-V compounds which exhibits self-pulsation in the presence of a dissipative optomechanical coupling. In such a laser cavity, radiation pressure drives the mechanical degree of freedom and its back-action is caused by the mechanical modulation of the cavity loss rate. Our numerical analysis shows that even in a wideband gain material, such dissipative coupling couples the mechanical oscillation with the laser relaxation oscillations process. Laser self-pulsation is observed for mechanical frequencies below the laser relaxation oscillation frequency under sufficiently high optomechanical coupling factor.",1411.4710v1 2014-11-19,Coupled-mode theory for binary optical lattices,"The coupled-mode theory is developed for description of the nonlinear wave dynamics in binary optical lattices. The obtained equations of motion accurately describe nonlinear wave dynamics close to the band edges and in the gap of the linear spectrum of the system. In order to demonstrate the power of the presented approach, bright gap solitary wave solutions of the nonlinear coupled- mode equations are derived and examined both analytically and numerically. The presented results are relevant to nonlinear wave phenomena in coupled waveguide arrays, coupled nano-cavities in photonic crystals, metallo-dielectric systems, and the Bose-Einstein condensates in deep optical lattices.",1411.5211v1 2014-11-23,A combined field approach for the two-way coupling problem in the liquid evaporation,"During liquid evaporation, the temperature of the liquid determines the saturated vapor pressure above it, which controls the evaporation rate and thus determines the liquid temperature through latent heat. Therefore, the equations for the vapor concentration in the atmosphere and for the temperature in the liquid are coupled and must be solved in an iterative manner. In the present paper, a combined field approach which unifies the coupled fields into one single field and thus makes the iteration unnecessary is proposed. The present work will be useful in scientific and industrial processes involving liquid evaporation and may also have more general applications to coupled field problems in which all the fields have the same governing equation.",1411.6619v1 2014-11-25,Angular spin-orbit coupling in cold atoms,"We propose coupling two internal atomic states using a pair of Raman beams operated in Laguerre-Gaussian laser modes with unequal phase windings. This generates a coupling between the atom's pseudo-spin and its orbital angular momentum. We analyze the single-particle properties of the system using realistic parameters and provide detailed studies of the spin texture of the ground state. Finally, we consider a weakly interacting atomic condensate subject to this angular spin-orbit coupling and show how the inter-atomic interactions modifies the single-particle physics.",1411.6895v1 2014-11-28,Random walks on torus and random interlacements: Macroscopic coupling and phase transition,"For $d\ge 3$ we construct a new coupling of the trace left by a random walk on a large $d$-dimensional discrete torus with the random interlacements on $\mathbb Z^d$. This coupling has the advantage of working up to macroscopic subsets of the torus. As an application, we show a sharp phase transition for the diameter of the component of the vacant set on the torus containing a given point. The threshold where this phase transition takes place coincides with the critical value $u_*(d)$ of random interlacements on $\mathbb Z^d$. Our main tool is a variant of the soft-local time coupling technique of [PT12].",1411.7795v1 2014-12-12,Tunable Spin-Orbit Coupling via Strong Driving in Ultracold Atom Systems,"Spin-orbit coupling (SOC) is an essential ingredient in topological materials, conventional and quantum-gas based alike.~Engineered spin-orbit coupling in ultracold atom systems --unique in their experimental control and measurement opportunities-- provides a major opportunity to investigate and understand topological phenomena.~Here we experimentally demonstrate and theoretically analyze a technique for controlling SOC in a two component Bose-Einstein condensate using amplitude-modulated Raman coupling.",1412.4064v1 2015-01-13,A QCD sum rules calculation of the $J/ψD_s^* D_s$ strong coupling constant,"In this work, we calculate the form factors and the coupling constant of the strange-charmed vertex $J/\psi D_s^* D_s$ in the framework of the QCD sum rules by studying their three-point correlation functions. All the possible off-shell cases are considered, $D_s$, $D_s^*$ and $J/\psi$, resulting in three different form factors. These form factors are extrapolated to the pole of their respective off-shell mesons, giving the same coupling constant for the process. Our final result for the $J/\psi D_s^* D_s$ coupling constant is $g_{J/\psi D^*_s D_s} = 4.30^{+0.42}_{-0.37}\text{GeV}^{-1}$.",1501.03088v1 2015-01-24,Magnetic Coupling in Ferromagnetic Semiconductor GaMnAs/AlGaMnAs Bilayer Devices,"We carefully investigated the ferromagnetic coupling in the as-grown and annealed ferromagnetic semiconductor GaMnAs/AlGaMnAs bilayer devices. We observed that the magnetic interaction between the two layers strongly affects the magnetoresistance of the GaMnAs layer with applying out of plane magnetic field. After low temperature annealing, the magnetic easy axis of the AlGaMnAs layer switches from out of plane into in-plane and the interlayer coupling efficiency is reduced from up to 0.6 to less than 0.4. However, the magnetic coupling penetration depth for the annealed device is twice that of the as-grown bilayer device.",1501.05993v1 2015-01-30,Renewal Approach to the Analysis of the Asynchronous State for Coupled Noisy Oscillators,"We develop a framework in which the activity of nonlinear pulse-coupled oscillators is posed within the renewal theory. In this approach, the evolution of inter-event density allows for a self-consistent calculation that determines the asynchronous state and its stability. This framework, can readily be extended to the analysis of systems with more state variables. To exhibit this, we study a nonlinear pulse-coupled system, where couplings are dynamic and activity dependent. We investigate stability of this system and we show it undergoes a super-critical Hopf bifurcation to collective synchronization.",1501.07799v1 2015-02-17,Monotone substochastic operators and a new Calderon couple,"An important result on submajorization, which goes back to Hardy, Littlewood and P\'olya, states that $b\preceq a$ if and only if there is a doubly stochastic matrix $A$ such that $b=Aa$. We prove that under monotonicity assumptions on vectors $a$ and $b$ respective matrix $A$ may be chosen monotone. This result is then applied to show that $(\widetilde{L^p},L^{\infty})$ is a Calder\'on couple for $1\leq p<\infty $, where $\widetilde{L^{p}}$ is the K\""othe dual of the Ces\`aro space $Ces_{p'}$ (or equivalently the down space $L^{p'}_{\downarrow}$). In particular, $(\widetilde{L^1},L^{\infty})$ is a Calder\'on couple and this complements the result of [MS06] where it was shown that $(L^{\infty}_{\downarrow},L^{1})$ is a Calder\'on couple.",1502.04882v1 2015-02-25,Synchronization of coupled chaotic maps,"We prove a sufficient condition for synchronization for coupled one-dimensional maps and estimate the size of the window of parameters where synchronization takes place. It is shown that coupled systems on graphs with positive eigenvalues (EVs) of the normalized graph Laplacian concentrated around 1 are more amenable for synchronization. In the light of this condition, we review spectral properties of Cayley, quasirandom, power-law graphs, and expanders and relate them to synchronization of the corresponding networks. The analysis of synchronization on these graphs is illustrated with numerical experiments. The results of this paper highlight the advantages of random connectivity for synchronization of coupled chaotic dynamical systems.",1502.07264v1 2015-02-27,Performance of Frozen Density Embedding for Modeling Hole Transfer Reactions,"We have carried out a thorough benchmark of the FDE-ET method for calculating hole transfer couplings. We have considered 10 exchange-correlation functionals, 3 non-additive kinetic energy functionals and 3 basis sets. Overall, we conclude that with a 7% mean relative unsigned error, the PBE functional coupled with the PW91k non-additive Kinetic energy functional and a TZP basis set constitutes the most stable, and accurate level of theory for hole-transfer coupling calculations. The FDE-ET method is found to be an excellent tool for computing diabatic couplings for hole transfer reactions.",1502.07957v1 2015-03-17,Coupled wire construction of chiral spin liquids,"We develop a coupled wire construction of chiral spin liquids. The starting point are individual wires of electrons in the Mott regime that are subject to a Zeeman field and Rashba spin-orbit coupling. Suitable spin-flip couplings between the wires yield an Abelian chiral spin liquid state which supports spinon excitations above a bulk gap, and chiral edge states. The approach generalizes to non-Abelian chiral spin liquids at level k with parafermionic edge states.",1503.05051v2 2015-03-18,Oscillations and synchronization in a system of three reactively coupled oscillators,"We consider a system of three interacting van der Pol oscillators with reactive coupling. Phase equations are derived, using proper order of expansion over the coupling parameter. The dynamics of the system is studied by means of the bifurcation analysis and with the method of Lyapunov exponent charts. Essential and physically meaningful features of the reactive coupling are discussed.",1503.05313v3 2015-03-27,On Coupling NEC-Violating Matter to Gravity,"We show that effective theories of matter that classically violate the null energy condition cannot be minimally coupled to Einstein gravity without being inconsistent with both string theory and black hole thermodynamics. We argue however that they could still be either non-minimally coupled or coupled to higher-curvature theories of gravity.",1503.07950v1 2015-04-16,Coupling ferroelectricity with spin-valley physics in oxide-based heterostructure,"The coupling of spin and valley physics is nowadays regarded as a promising route toward next-generation spintronic and valleytronic devices. In the aim of engineering functional properties for valleytronic applications, we focus on the ferroelectric heterostructure BiAlO3/BiIrO3, where the complex interplay among trigonal crystal field, layer degrees of freedom and spin-orbit coupling mediates a strong spin-valley coupling. Furthermore, we show that ferroelectricity provides a non-volatile handle to manipulate and switch the emerging valley-contrasting spin polarization.",1504.04091v1 2015-05-04,From the Higgs to the top: Couplings and Rare Decays,"Within the Standard Model the Higgs couplings to fermions and gauge bosons, as function of the particle mass, are predicted to lay on a single line. However, new patterns appear in multi-Higgs models that employ the Froggart-Nielsen mechanism, where the diagonal couplings could lay on different lines and flavor-violating Higgs couplings could appear too. These aspects are studied for a specific model with 3+1 Higgs doublets and a singlet FN field. Constraints on the model are derived from the Higgs search at LHC, and some remarks are presented on their implications for the rare top and Higgs decay, t -> ch and h -> \tau \mu.",1505.00757v1 2015-06-03,Non-canonical inflation coupled to matter,"We compute corrections to the inflationary potential due to conformally coupled non-relativistic matter. We find that under certain conditions of the matter coupling, inflation may be interrupted abruptly. We display this in the superconformal Starobinsky model, where matter is conformally coupled to the Einstein frame metric. These corrections may easily stop inflation provided that there is an initial density of non-relativistic matter. Since these additional heavy degrees of freedom generically occur in higher dimension theories, for example as Kaluza-Klein modes, this effect can arise in multiple scenarios.",1506.01244v2 2015-06-14,Targeting engineering synchronization in chaotic systems,"A method of targeting engineering synchronization states in two identical and mismatch chaotic systems is explained in details. The method is proposed using linear feedback controller coupling for engineering synchronization such as mixed synchronization, linear and nonlinear generalized synchronization and targeting fixed point. The general form of coupling design to target any desire synchronization state under unidirectional coupling with the help of Lyapunov function stability theory is derived analytically. A scaling factor is introduced in the coupling definition to smooth control without any loss of synchrony. Numerical results are done on two mismatch Lorenz systems and two identical Sprott oscillators.",1506.04351v1 2015-06-16,Higgs-inflaton coupling from reheating and the metastable Universe,"Current Higgs boson and top quark data favor metastability of our vacuum which raises questions as to why the Universe has chosen an energetically disfavored state and remained there during inflation. In this Letter, we point out that these problems can be solved by a Higgs-inflaton coupling which appears in realistic models of inflation. Since an inflaton must couple to the Standard Model particles either directly or indirectly, such a coupling is generated radiatively, even if absent at tree level. As a result, the dynamics of the Higgs field can change dramatically.",1506.05106v2 2015-06-16,Switchable Coupling of Vibrations to Two-Electron Carbon-Nanotube Quantum Dot States,"We report transport measurements on a quantum dot in a partly suspended carbon nanotube. Electrostatic tuning allows us to modify and even switch 'on' and 'off' the coupling to the quantized stretching vibration across several charge states. The magnetic-field dependence indicates that only the two-electron spin-triplet excited state couples to the mechanical motion, indicating mechanical coupling to both the valley degree of freedom and the exchange interaction, in contrast to standard models.",1506.05137v1 2015-06-19,Chimeras in networks with purely local coupling,"Chimera states in spatially extended networks of oscillators have some oscillators synchronised while the remainder are asynchronous. These states have primarily been studied in networks with nonlocal coupling, and more recently in networks with global coupling. Here we present three networks with only local coupling (diffusive, to nearest neighbours) which are numerically found to support chimera states. One of the networks is analysed using a self-consistency argument in the continuum limit, and this is used to find the boundaries of existence of a chimera state in parameter space.",1506.05871v1 2015-06-29,Monte Carlo determination of the critical coupling in $φ^4_2$ theory,"We use lattice formulation of $\phi^4$ theory in order to investigate non--perturbative features of its continuum limit in two dimensions. In particular, by means of Monte Carlo calculations, we obtain the critical coupling constant $g/\mu^2$ in the continuum, where $g$ is the {\em unrenormalised} coupling. Our final result is $g/\mu^2=11.15(6)(3)$.",1506.08587v2 2015-09-05,Boundary and coupled boundary-finite element methods for transient wave-structure interaction,"We propose time-domain boundary integral and coupled boundary integral and variational formulations for acoustic scattering by linearly elastic obstacles. Well posedness along with stability and error bounds with explicit time dependence are established. Full discretization is achieved coupling boundary and finite elements; Convolution Quadrature is used for time evolution in the pure BIE formulation and combined with time stepping in the coupled BEM/FEM scenario. Second order convergence in time is proven for BDF2-CQ and numerical experiments are provided for both BDF2 and Trapezoidal Rule CQ showing second order behavior for the latter as well.",1509.01713v1 2015-09-08,Probing Scalar Coupling Differences via Long-Lived Singlet States,"We probe small scalar coupling differences via the coherent interactions between two nuclear spin singlet states in organic molecules. We show that the spin-lock induced crossing (SLIC) technique enables the coherent transfer of singlet order between one spin pair and another. The transfer is mediated by the difference in cis and trans vicinal J couplings among the spins. By measuring the transfer rate, we calculate a J coupling difference of $8 \pm 2$ mHz in phenylalanine-glycine-glycine and $2.57 \pm 0.04$ Hz in glutamate. We also characterize a coherence between two singlet states in glutamate, which may enable the creation of a long-lived quantum memory.",1509.02240v1 2015-09-17,Polariton resonances for ultra-strong coupling cavity optomechanics in GaAs/AlAs multiple quantum wells,"Polariton-mediated light-sound interaction is investigated through resonant Brillouin experiments in GaAs/AlAs multiple-quantum wells. Photoelastic coupling enhancement at exciton-polariton resonance reaches 105 at 30 K as compared to a typical bulk solid room temperature transparency value. When applied to GaAs based cavity optomechanical nanodevices, this result opens the path to huge displacement sensitivities and to novel ultrastrong-coupling cavity phenomena with optomechanical couplings g0 in the range of 100 THz.",1509.05152v1 2015-10-12,$β$-function formalism for inflationary models with a non minimal coupling with gravity,"We discuss the introduction of a non minimal coupling between the inflaton and gravity in terms of the recently proposed $\beta$-function formalism for inflation\cite{Binetruy:2014zya}. Via a field redefinition we reduce to the case of minimally coupled theories. The universal attractor at strong coupling has a simple explanation in terms of the new field. Generalizations are discussed and the possibility of evading the universal attractor is shown.",1510.03691v2 2015-10-14,Pseudo-locality for a coupled Ricci flow,"Let $(M,g,\phi)$ be a solution to the Ricci flow coupled with the heat equation for a scalar field $\phi$. We show that a complete, $\kappa$-noncollapsed solution $(M,g,\phi)$ to this coupled Ricci flow with a Type I singularity at time $T<\infty$ will converge to a non-trivial Ricci soliton after parabolic rescaling, if the base point is Type I singular. A key ingredient is a version of Perelman pseudo-locality for the coupled Ricci flow.",1510.04332v3 2015-10-16,Tachyon field non-minimally coupled to massive neutrino matter,"In this paper, we consider rolling tachyon, with steep run-away type of potentials non-minimally coupled to massive neutrino matter. The coupling dynamically builds up at late times as neutrino matter turns non-relativistic. In case of scaling and string inspired potentials, we have shown that non-minimal coupling leads to minimum in the field potential. Given a suitable choice of model parameters, it is shown to give rise to late-time acceleration with the desired equation of state.",1510.04795v2 2015-10-27,Direct measurement of second-order coupling in a waveguide lattice,"We measure the next-nearest-neighbour coupling in an array of coupled optical waveguides directly via an integrated eigenmode interferometer. In contrast to light propagation experiments, the technique is insensitive to nearest-neighbour dynamics. Our results show that second-order coupling in a linear configuration can be suppressed well below the level expected from the exponential decay of the guided modes.",1510.07900v2 2015-11-05,Bounds on Neutrino-Scalar Yukawa Coupling,"General neutrino-scalar couplings appear in many extensions of Standard Model. We can probe these neutrino-scalar couplings by leptonic decay of mesons and from heavy neutrino search. Our analysis improves the present limits to $|g_e|^2<1.9\times 10^{-6}$ and $|g_\mu|^2<1.9\times 10^{-7}$ at 90\% C.L. for massless scalars. For massive scalars we found for the first time the constraints for $g^2_{\alpha}$ couplings to be $10^{-6}-10^{-1}$ respectively for scalar masses between below 1 MeV and for 300 MeV.",1511.01811v2 2016-01-22,FG- coupled fixed point theorems for various contractions in partially ordered metric spaces,"In this paper we introduce FG- coupled fixed point, which is a generalization of coupled fixed point for nonlinear mappings in partially ordered complete metric spaces. We discuss existence and uniqueness theorems of FG- coupled fixed points for different contractive mappings. Our theorems generalizes the results of Gnana Bhaskar and Lakshmikantham [T. Gnana Bhaskar, V. Lakshmikantham; Fixed point theorems in partially ordered metric spaces and applications; Nonlinear Analysis 65 (2006) 1379 -1393].",1602.00543v1 2016-02-05,Yukawa couplings in 6D gauge-Higgs unification on $T^2/Z_N$ with magnetic fluxes,"We discuss the Yukawa couplings in 6D gauge-Higgs unification models on $T^2/Z_N$ in the presence of magnetic fluxes. We provide general formulae for them, and numerically evaluate their magnitude in a specific model on $T^2/Z_3$. Thanks to the nontrivial profiles of the zero-mode wave functions, the top quark Yukawa coupling can be reproduced without introducing a large representation of the gauge group for matter fields. However, it is difficult to realize small Yukawa couplings only by the magnetic fluxes and the Wilson-line phases because of the complicated structure of the mode functions on $T^2/Z_N$ ($N=3,4,6$).",1602.01994v2 2016-02-08,Leptogenesis in supersymmetry with one $L$ violating coupling,"We have shown a new scenario of successful leptogenesis with one $L$ violating coupling and a relative Majorana phase playing the role of $CP$ violation. This is in contrast to the usual consideration of Feynman diagram with at least two $L$ violating couplings. We have considered $R$-parity violating Minimal Supersymmetric Standard Model (MSSM) for leptogenesis at TeV scale. This scenario is also consistent with generating light neutrino mass if asymmetry is generated through semileptonic $\lambda^{\prime}$ coupling.",1602.02684v4 2016-01-25,Method for generating two coupled Gaussian stochastic processes,"Most processes in nature are coupled; however, extensive null models for generating such processes still lacks. We present a new method to generate two coupled Gaussian stochastic processes with arbitrary correlation functions. This method is developed by modifying the Fourier filtering method. The robustness of this method is proved by generating two coupled fractional Brownian motions and extending its range of application to Gaussian random fields.",1602.04697v1 2016-02-26,Coupled networks and networks with bimodal frequency distributions are equivalent,"Populations of oscillators can display a variety of synchronization patterns depending on the oscillators' intrinsic coupling and the coupling between them. We consider two coupled, symmetric (sub)populations with unimodal frequency distributions and show that the resulting synchronization patterns may resemble those of a single population with bimodally distributed frequencies. Our proof of the equivalence of their stability, dynamics, and bifurcations, is based on an Ott-Antonsen ansatz. The generalization to networks consisting of multiple (sub)populations vis-\`a-vis networks with multimodal frequency distributions, however, appears impossible.",1602.08368v2 2016-04-04,Coupling single emitters to quantum plasmonic circuits,"In recent years the controlled coupling of single photon emitters to propagating surface plasmons has been intensely studied, which is fueled by the prospect of a giant photonic non-linearity on a nano-scaled platform. In this article we will review the recent progress on coupling single emitters to nano-wires towards the construction of a new platform for strong light-matter interaction. The control over such a platform might open new doors for quantum information processing and quantum sensing at the nanoscale, and for the study of fundamental physics in the ultra-strong coupling regime.",1604.00846v1 2016-04-06,Periodically modulated electromagnetically induced transparency,"Phenomena of electromagnetically induced transparency (PEIT) may be interpreted by the Autler-Townes Splitting (ATS), where the coupled states are split by the coupling laser field, or by the quantum destructive interference (QDI), where the atomic phases caused by the coupling laser and the probe laser field cancel. We propose modulated experiments to explore the PEIT in an alternative way by periodically modulating the coupling and the probe fields in a ?-type three-level system. Our analytical and numerical results rule out the ATS interpretation and show that the QDI interpretation is more appropriate for the modulated experiments. The proposed experiments are readily implemented in atomic gases, artificial atoms in superconducting quantum devices, or three-level meta-atoms in meta-materials.",1604.01539v1 2016-04-15,A Trigonometric Cubic B-spline Finite Element Method for Solving the Nonlinear Coupled Burger Equation,"The coupled Burgers equation is solved by way of the trigonometric B-spline collocation method. The unknown of the coupled Burgers equation is integrated in time by aid of the Crank-Nicolson method. Resulting time-integrated coupled Burgers equation is discretized using the trigonometric cubic B-spline collocation method. Fully-integrated couupled Burgers equation which is a system of nonlinear algebraic equation is solved with a variant of Thomas algorithm. The three model test problems are studied to illustrate the accuracy of the suggested method.",1604.04419v1 2016-04-20,Cavity piezomechanical strong coupling and frequency conversion on an aluminum nitride chip,"Schemes to achieve strong coupling between mechanical modes of aluminum nitride microstructures and microwave cavity modes due to the piezoelectric effect are proposed. We show that the strong coupling regime is feasible for an on-chip aluminum nitride device that is either enclosed by a three-dimensional microwave cavity or integrated with a superconducting coplanar resonator. Combining with optomechanics, the piezomechanical strong coupling permits coherent conversion between microwave and optical modes with high efficiency. Hence, the piezomechanical system will be an efficient transducer for applications in hybrid quantum systems.",1604.06027v1 2016-06-24,Topological quantum phase transition driven by anisotropic spin-orbit coupling in trinuclear organometallic coordination crystals,"We show how quasi-one-dimensional correlated insulating states arise at two-thirds filling in organometallic multinuclear coordination complexes described by layered decorated honeycomb lattices. The interplay of spin-orbit coupling and electronic correlations leads to pseudospin-1 moments arranged in weakly coupled chains with highly anisotropic exchange and a large trigonal splitting. This leads to a quantum phase transition from a Haldane phase to a topologically trivial phase as the relative strength of the spin-orbit coupling increases.",1606.07691v1 2016-06-25,Monolayer graphene as dissipative membrane in an optical resonator,"We experimentally demonstrate coupling of an atomically thin, free-standing graphene membrane to an optical cavity. By changing the position of the membrane along the standing-wave field of the cavity we tailor the dissipative coupling between the membrane and the cavity, and we show that the dissipative coupling can outweigh the dispersive coupling. Such a system, for which controlled dissipation prevails dispersion, will prove useful for novel laser-cooling schemes in optomechanics. In addition, we have determined the continuous-wave optical damage threshold of free-standing monolayer graphene of 1.8(4)~MW/cm$^2$ at 780nm.",1606.07897v1 2016-03-15,Dynamics of Hydrogen Bonds Coupling on the Specific DNA-Protein Interactions,"We propose a dynamical model depicting the interactions between DNA and a specific binding protein involving long range transmissions. The dynamics rely on the coupling between Hydrogen bonds formed between DNA and protein and between the base pairs because they account for site specificity of the binding. We adopt the Morse potential with coupling terms to construct the Hamiltonian. This model gives rise to a breather excitation, corresponding to the DNA bubble formation, which propagates as the carrier of genetic information. We examine the various kind of possible coupling dynamics and suggest the model feasibility in depicting the renaturation or hybridization processes.",1607.01608v1 2016-07-10,Time optimal control in coupled spin systems: a second order analysis,"In this paper, we study some control problems that derive from time optimal control of coupled spin dynamics in NMR spectroscopy and quantum information and computation. Time optimal control helps to minimize relaxation losses. The ability to synthesize, local unitaries, much more rapidly than evolution of couplings, gives a natural time scale separation in these problems. The generators of evolution, $\g$, are decomposed into fast generators $\k$ (local Hamiltonians) and slow generators $\p$ (couplings) as a Cartan decomposition $\g = \p \oplus \k$. Using this decomposition, we exploit some convexity ideas to completely characterize the reachable set and time optimal control for these problems. In this paper, we carry out a second order analysis of time optimality.",1607.02692v2 2016-07-13,On four-derivative terms in IIB Calabi-Yau orientifold reductions,"We perform a Kaluza-Klein reduction of IIB supergravity including purely gravitational $\alpha '^3$-corrections on a Calabi-Yau threefold, and perform the orientifold projection accounting for the presence of $O3/O7$-planes. We consider infinitesimal K\""{a}hler deformations of the Calabi-Yau background and derive the complete set of four-derivative couplings quadratic in these fluctuations coupled to gravity. In particular, we find four-derivative couplings of the K\""{a}hler moduli fields in the four-dimensional effective supergravity theory, which are referred to as friction couplings in the context of inflation.",1607.03913v2 2016-07-29,Twisted spin vortices in a spinor-dipolar Bose-Einstein condensate with Rashba spin-orbit coupling,"We consider a spin-1 Bose-Einstein condensate with Rashba spin-orbit coupling and dipole-dipole interaction confined in a cigar-shaped trap. Due to the combined effects of spin-orbit coupling, dipole-dipole interaction, and trap geometry, the system exhibits a rich variety of ground-state spin structures, including twisted spin vortices. The ground-state phase diagram is determined with respect to the strengths of the spin-orbit coupling and dipole-dipole interaction.",1607.08724v1 2017-02-15,Superradiant Amplification of a Scalar Wave Coupled Kinematically to Curvature Scattered off a Reissner-Nordström Black Hole,"We study the dynamics of a massive charged scalar wave which except its canonical coupling to gravity it is also coupled kinematically to Einstein tensor. We find that as the strength of the new coupling is increased the scattered wave off the horizon of a Reissner-Nordstr\""om black hole is superradiantly amplified resulting to the instability of the Reissner-Nordstr\""om spacetime.",1702.04618v2 2017-02-20,Electron-ion coupling in semiconductors beyond Fermi's golden rule,"In the present work, a theoretical study of electron-phonon (electron-ion) coupling rates in semiconductors driven out of equilibrium is performed. Transient change of optical coefficients reflects the band gap shrinkage in covalently bonded materials, and thus, the heating of atomic lattice. Utilizing this dependence, we test various models of electron-ion coupling. The simulation technique is based on tight-binding molecular dynamics. Our simulations with the dedicated hybrid approach (XTANT) indicate that the widely used Fermi's golden rule can break down describing material excitation on femtosecond time scales. In contrast, dynamical coupling proposed in this work yields a reasonably good agreement of simulation results with available experimental data.",1702.06174v1 2017-03-23,Boson-vortex duality in compressible spin-orbit coupled BECs,"Using a (1+2)-dimensional boson-vortex duality between non-linear electrodynamics and a two-component compressible Bose-Einstein condensate (BEC) with spin-orbit (SO) coupling, we obtain generalised versions of the hydrodynamic continuity and Euler equations where the phase defect and non-defect degrees of freedom enter separately. We obtain the generalised Magnus force on vortices under SO coupling, and associate the linear confinement of vortices due to SO coupling with instanton fluctuations of the dual theory.",1703.07918v1 2017-08-15,Conditional displacement interaction in ultrastrong-coupling regime,"We investigate the realization of conditional displacement interaction in the transversal direction in ultrastrongly coupled circuit quantum electrodynamics by adjusting parameters of external magnetic fields. The special interaction is derived in the system of charge qubit(s) coupled to a LC resonator. We consolidate the implementation of quantum gates and the generation of superposed coherent states based on the transversal conditional displacement interaction numerically. The conditional displacement interaction in the ultrastrong coupling regime enhances quantum process to operate at the time scale of nanoseconds.",1708.04371v1 2018-02-08,Anomalous phonon lifetime shortening in paramagnetic CrN caused by magneto-lattice coupling: A combined spin and ab initio molecular dynamics study,"We study the mutual coupling of spin fluctuations and lattice vibrations in paramagnetic CrN by combining atomistic spin dynamics and ab initio molecular dynamics. The two degrees of freedom are dynamically coupled leading to non-adiabatic effects. Those effects suppress the phonon life times at low temperature compared to an adiabatic approach. The here identified dynamic coupling provides an explanation for the experimentally observed unexpected temperature dependence of the thermal conductivity of magnetic semiconductors above the magnetic ordering temperature.",1802.02934v1 2018-02-13,Effect of phonon coupling on cooperative two-photon emission from two-quantum dots,"We predict dominating cooperative two-photon emission from two quantum dots coupled with a single mode photonic crystal cavity. The cooperative two photon emission occurs when excitons in two off-resonantly coupled quantum dots decay simultaneously. The interaction with common cavity field leads to cavity induced two-photon emission which is strongly inhibited by electron phonon coupling. The interaction with common phonon bath produces phonon induced two-photon emission which increases on increasing temperature. For identical quantum dots cavity induced two-photon emission is negligible but phonon induced two-photon emission could be large.",1802.04487v1 2018-02-13,Modulational instability of nonlinear polarization mode coupling in microresonators,"We investigate frequency comb generation in the presence of polarization effects induced by nonlinear mode coupling in microresonator devices. A set of coupled temporal Lugiato-Lefever equations are derived to model the propagation dynamics, and an in-depth study is made of the modulational instability of their multistable homogeneous steady-state solutions. It is shown that new kinds of instabilities can occur for co-propagating fields that interact through nonlinear cross-phase modulation. These instabilities display properties that differ from their scalar counterpart, and are shown to result in the generation of new types of incoherently coupled frequency comb states.",1802.04535v1 2018-02-19,On a saddle point problem arising from magneto-elastic coupling,"This paper deals with the analysis of a coupled problem arising from linear magneto-elastostaticity. The model, which can be derived by an energy principle, gives valuable insight into the coupling mechanism and features a saddle point structure with the elastic displacement and magnetic scalar potential as independent variables. As main results, the existence and uniqueness of the solution are proven for the continuous and discrete cases and special properties of the corresponding bilinear forms are shown. In particular, the coupled magneto-elastic bilinear form satisfies an inf-sup condition that is essential for the stability of the problem.",1802.06650v1 2018-04-04,Mechanism of solitary state appearance in an ensemble of nonlocally coupled Lozi maps,"We study the peculiarities of the solitary state appearance in the ensemble of nonlocally coupled chaotic maps. We show that nonlocal coupling and features of the partial elements lead to arising of multistability in the system. The existence of solitary state is caused by formation of two attractive sets with different basins of attraction. Their basins are analysed depending on coupling parameters.",1804.01289v1 2018-04-04,Atomic switch for control of heat transfer in coupled cavities,"Controlled heat transfer and thermal rectification in a system of two coupled cavities connected to thermal reservoirs are discussed. Embedding a dispersively interacting two-level atom in one of the cavities allows switching from a thermally conducting to resisting behavior. By properly tuning the atomic state and system-reservoir parameters, direction of current can be reversed, which violates the second law of thermodynamics. It is shown that a large thermal rectification is achievable in this system by tuning the cavity-reservoir and cavity-atom couplings. Partial recovery of diffusive heat transport in an array of $N$ cavities containing one dispersively coupled atom is established.",1804.01897v2 2018-03-29,The impact of electrical couplings on the sequential bursting activity in the ensemble of inhibitory coupled Van der Pol elements,"The new phenomenological model of the ensemble of three neurons with chemical (synaptic) and electrical couplings has been studied. One neuron is modeled by a single Van der Pol oscillator. The influence of the electrical coupling strength and the frequency mismatch between the elements to the regime of sequential activity is investigated.",1804.02437v1 2018-04-11,Constraint-Based Synthesis of Coupling Proofs,"Proof by coupling is a classical technique for proving properties about pairs of randomized algorithms by carefully relating (or coupling) two probabilistic executions. In this paper, we show how to automatically construct such proofs for probabilistic programs. First, we present f-coupled postconditions, an abstraction describing two correlated program executions. Second, we show how properties of f-coupled postconditions can imply various probabilistic properties of the original programs. Third, we demonstrate how to reduce the proof-search problem to a purely logical synthesis problem of the form $\exists f\ldotp \forall X\ldotp \phi$, making probabilistic reasoning unnecessary. We develop a prototype implementation to automatically build coupling proofs for probabilistic properties, including uniformity and independence of program expressions.",1804.04052v1 2018-11-02,Numerical phase reduction beyond the first order approximation,"We develop a numerical approach to reconstruct the phase dynamics of driven or coupled self-sustained oscillators. Employing a simple algorithm for computation of the phase of a perturbed system, we construct numerically the equation for the evolution of the phase. Our simulations demonstrate that the description of the dynamics solely by phase variables can be valid for rather strong coupling strengths and large deviations from the limit cycle. Coupling functions depend crucially on the coupling and are generally non-decomposable in phase response and forcing terms. We also discuss limitations of the approach.",1811.00771v2 2018-11-22,Enhanced Rashba spin-orbit coupling in core-shell nanowires by the interfacial effect,"We report on $\vec{k}\cdot\vec{p}$ calculations of Rashba spin-orbit coupling controlled by external gates in InAs/InAsP core-shell nanowires. We show that charge spilling in the barrier material allows for a stronger symmetry breaking than in homoegenous nano-materials, inducing a specific interface-related contribution to spin-orbit coupling. Our results qualitatively agree with recent experiments [S. Futhemeier \textit{et al.}, Nat. Commun. \textbf{7}, 12413 (2016)] and suggest additional wavefunction engineering strategies to enhance and control spin-orbit coupling.",1811.09088v1 2010-05-10,Relaxation Dynamics of Photocarriers in One-Dimensional Mott Insulators Coupled to Phonons,"We examine recombination processes of photocarriers in one-dimensional Mott insulators coupled to phonons. Performing density matrix renormalization group calculations, we find that, even for small electron-phonon coupling, many phonons are generated dynamically, which cause initial relaxation process after the irradiation. At the same time, spin-charge coupling coming from mixing of high- and low-energy states by the irradiation is suppressed. We discuss differences between Mott and band insulators in terms of relaxation dynamics.",1005.1690v3 2010-05-21,Synchronization of coupled limit cycles,"A unified approach for analyzing synchronization in coupled systems of autonomous differential equations is presented in this work. Through a careful analysis of the variational equation of the coupled system we establish a sufficient condition for synchronization in terms of the geometric properties of the local limit cycles and the coupling operator. This result applies to a large class of differential equation models in physics and biology. The stability analysis is complemented with a discussion of numerical simulations of a compartmental model of a neuron.",1005.4074v2 2013-08-06,Barrierless Electronic Relaxation in Solution: An analytically solvable model with arbitrary coupling,"In our recent publication, we have proposed an analytical method for solving the problem of electronic relaxation in solution, modeled by a particle undergoing diffusive motion under the influence of two arbitrary potentials and the coupling between the two potentials was assumed to be localized at one point. In this paper we have extended our work to deal with the case of delocalized coupling between two potentials. The average and long term rate constant for delocalized coupling is presented.",1308.1354v2 2013-08-07,Coupling of optical far-fields into aperture-less plasmonic nanofibre tips,"This paper reports on the excitation of surface plasmons on gold-coated nanofibre tips by side-illumination with a laser beam and the coupling of the surface plasmons to the optical fiber. The measurements show a strong dependence of the coupling efficiency on the incidence angle with a maximum coupling efficiency on the order of few percent. Moreover, the fibre tip was used as scanning probe device for measuring the beam waist of a focussed laser beam. This work is motivated by the goal to use such plasmonic nanofibre tips in quantum optics experiments with cold atoms.",1308.1593v1 2013-08-10,Desired Control of Mutually Delay-Coupled Diode Lasers near Phase-flip Transition Regimes,"We investigate zero-lag synchronization (ZLS) between delay-coupled diode lasers system with mutual optical injection in a face-to-face configuration. We observed numerical evidence of such ZLS without using any relay element or mediating laser. In addition, simulation also demonstrate that this kind of robust ZLS occurs around the phase flip transition regimes where in-phase and anti-phase oscillations coexist due to delayed coupling induced modulation of the phase-amplitude coupling factor {\alpha}. Our finding could be implemented in highly secured optical communication network as well as the understanding of the occurrence of such ZLS in the neural network functionality.",1308.2313v1 2013-08-15,Spintronics and Pseudospintronics in Graphene and Topological Insulators,"The two-dimensional electron systems in graphene and in topological insulators are described by massless Dirac equations. Although the two systems have similar Hamiltonians, they are polar opposites in terms of spin-orbit coupling strength. We briefly review the status of efforts to achieve long spin relaxation times in graphene with its weak spin-orbit coupling, and to achieve large current-induced spin polarizations in topological-insulator surface states that have strong spin-orbit coupling. We also comment on differences between the magnetic responses and dilute-moment coupling properties of the two systems, and on the pseudospin analog of giant magnetoresistance in bilayer graphene.",1308.3428v1 2013-08-18,(In-)Stability and Stabilisation of QNL-Type Atomistic-to-Continuum Coupling Methods,"We study the stability of ghost force-free energy-based atomistic-to-continuum coupling methods. In 1D we essentially complete the theory by introducing a universally stable a/c coupling as well as a stabilisation mechanism for unstable coupling schemes. We then present a comprehensive study of a two-dimensional scalar planar interface setting, as a step towards a general 2D/3D vectorial analysis. Our results point out various new challenges. For example, we find that none of the ghost force-free methods known to us are universally stable (i.e., stable under general interaction and general loads). We then explore to what extent our 1D stabilisation mechanism can be extended.",1308.3894v1 2013-08-22,The quantum AdS_5 x S^5 superstring at finite coupling,"The integrability of string theory in AdS_5 x S^5 and of the dilatation operator of N=4 super-Yang-Mills theory has been used to propose an exact solution to the spectral problem in these theories. Weak coupling perturbation theory both in gauge theory and on the worldsheet has been extensively used to verify this solution. We discuss worldsheet methods for finding the spectrum of the AdS_5 x S^5 superstring at finite values of the coupling constant and illustrate them by recovering, within numerical errors, the predictions of the BES equation for the universal scaling function. This is the first finite-coupling calculation in this theory which uses field theory methods.",1308.4875v1 2013-08-24,Effect of solute segregation on shear-induced grain boundary motion,"Atomic-scale simulations are performed to study the effect of solute segregation on the shear-induced motion of select grain boundaries in the classical $\alpha$-Fe/C system. At shear rates larger than the solute diffusion rate, we observe a transition from coupled motion to sliding. Below a critical solute excess, the boundaries break away from the solute cloud and move in a coupled motion. At smaller shear rates, we observe extrinsic coupled motion at small stresses indicating that the coupling is aided by convective solute diffusion along the boundary. Our studies underscore the role of solutes in modifying the bicrystallography, temperature and rate dependence of shear accommodation at grain boundaries.",1308.5350v1 2013-08-29,Spin-orbit coupling and spin Hall effect for neutral atoms without spin-flips,"We propose a scheme which realizes spin-orbit coupling and the spin Hall effect for neutral atoms in optical lattices without relying on near resonant laser light to couple different spin states. The spin-orbit coupling is created by modifying the motion of atoms in a spin-dependent way by laser recoil. The spin selectivity is provided by Zeeman shifts created with a magnetic field gradient. Alternatively, a quantum spin Hamiltonian can be created by all-optical means using a period- tripling, spin-dependent superlattice.",1308.6349v1 2014-03-01,Synchronization in populations of sparsely connected pulse-coupled oscillators,"We propose a population model for $\delta$-pulse-coupled oscillators with sparse connectivity. The model is given as an evolution equation for the phase density which take the form of a partial differential equation with a non-local term. We discuss the existence and stability of stationary solutions and exemplify our approach for integrate-and-fire-like oscillators. While for strong couplings, the firing rate of stationary solutions diverges and solutions disappear, small couplings allow for partially synchronous states which emerge at a supercritical Andronov-Hopf bifurcation.",1403.0102v1 2014-03-05,Breathing solitary-pulse pairs in a linearly coupled system,"It is shown that pairs of solitary pulses (SPs) in a linearly-coupled system with opposite group-velocity dispersions form robust breathing bound states. The system can be realized by temporal-modulation coupling of SPs with different carrier frequencies propagating in the same medium, or by coupling of SPs in a dual-core waveguide. Broad SP pairs are produced in a virtually exact form by means of the variational approximation. Strong nonlinearity tends to destroy the periodic evolution of the SP pairs.",1403.1031v1 2014-03-10,Infinitely many solutions to linearly coupled Schrödinger equations with non-symmetric potential,"We study a linearly coupled Schr\""{o}dinger system in $\R^N(N\leq3).$ Assume that the potentials in the system are continuous functions satisfying suitable decay assumptions, but without any symmetry properties and the parameters in the system satisfy some suitable restrictions. Using the Liapunov-Schmidt reduction methods two times and combing localized energy method, we prove that the problem has infinitely many positive synchronized solutions, which extends the result Theorem 1.2 about nonlinearly coupled Schr\""{o}dinger equations in \cite{aw} to our linearly coupled problem.",1403.2179v2 2014-03-11,Holographic thermalization patterns,"We investigate the behaviour of various correlators in N=4 super Yang Mills theory, taking finite coupling corrections into account. In the thermal limit we investigate the flow of the quasinormal modes as a function of the 't Hooft coupling. Then by using a specific model of holographic thermalization we investigate the deviation of the spectral densities from their thermal limit in an out-of-equilibrium situation. The main focus lies on the thermalization pattern with which the various plasma constituents of different energies approach their final thermal distribution as the coupling constant decreases from the infinite coupling limit. All results point towards the weakening of the usual top down thermalization pattern.",1403.2489v1 2014-03-12,Present and future constraints on top EW couplings,"Various BSM models predict large deviations of the top electroweak couplings. Many examples will be given emphasizing the need for precise and model independent measurements of these couplings. Here I address the question of compatibility between theoretical predictions and the LEP/SLC/Tevatron constraints which, through loop effects, allow setting very significant constraints on these predictions. A Randall Sundrum inspired prediction will be discussed in more details. Finally the prospects offered by LHC and ILC measurements for top EW couplings are briefly reviewed.",1403.2893v1 2014-03-25,Synchronization in nonlinear oscillators with conjugate coupling,"In this work, we investigate the synchronization in oscillators with conjugate coupling in which oscillators interact via dissimilar variables. The synchronous dynamics and its stability are investigated theoretically and numerically. We find that the synchronous dynamics and its stability are dependent on both coupling scheme and the coupling constant. We also find that the synchronization may be independent of the number of oscillators. Numerical demonstrations with Lorenz oscillators are provided.",1403.6226v1 2017-01-12,Molecular Plasmonics: strong coupling at the low molecular density limit,"We study the strong coupling between the molecular excited state and the plasmonic modes of silver hole arrays with a resonant frequency very close to the asymptotic line of the plasmonic dispersion relation, at the nonlinear regime. We demonstrate that the strong coupling regime can be achieved between the two sub-systems at low molecular densities with negligible damping of the electromagnetic field. Our results are supported by rigorous numerical simulations showing that the strong coupling is observed when the molecular transition lies within the nonlinear regime of the dispersion relation rather than the linear regime.",1701.03402v2 2017-01-17,Vortex pairs in a spin-orbit coupled Bose-Einstein condensate,"Static and dynamic properties of vortices in a two-component Bose-Einstein condensate with Rashba spin-orbit coupling are investigated. The mass current around a vortex core in the plane-wave phase is found to be deformed by the spin-orbit coupling, and this makes the dynamics of the vortex pairs quite different from those in a scalar Bose-Einstein condensate. The velocity of a vortex-antivortex pair is much smaller than that without spin-orbit coupling, and there exist stationary states. Two vortices with the same circulation move away from each other or unite to form a stationary state.",1701.04591v1 2017-01-19,Controllability of a 2x2 parabolic system by one force with a space-dependent coupling term of order one,"This paper is devoted to the controllability of linear systems of two coupled parabolic equations when the coupling involves a space dependent first order term. This system is set on an bounded interval, and the first equation is controlled by a force supported in a subinterval of I or on the boundary. In the case where the intersection of the coupling and control domains is nonempty, we prove null controllability at any time. Otherwise, we provide a minimal time for null controllability. Finally we give a necessary and sufficient condition for the approximate controllability. The main technical tool for obtaining these results is the moment method",1701.05315v1 2017-01-19,Positive and negative results on the internal controllability of parabolic equations coupled by zero and first order terms,"This paper is devoted to studying the null and approximate controllability of two linear coupled parabolic equations posed on a smooth domain of R^N (N>1) with coupling terms of zero and first orders and one control localized in some arbitrary nonempty open subset of the domain. We prove the null controllability under a new sufficient condition and we also provide the first example of a not approximately controllable system in the case where the support of one of the nontrivial first order coupling terms intersects the control domain.",1701.05318v1 2017-01-20,Non-minimally coupled gravity and vacuum stability,"We investigate the properties of vacuum decay taking into account a non-minimal coupling to gravity. We extend the standard thin-wall solution to include the non-minimal coupling and verify its validity by comparison with a full numerical study. We also investigate the implications of a~large cosmological constant whose influence on the geometry boosts the tunneling rate. Our analysis shows that the influence of the non-minimal coupling differs significantly between the cases of Minkowski and deSitter backgrounds.",1701.05731v1 2018-05-18,Boosting Entanglement Between Exciton-Polaritons with On-Off Switching of Josephson Coupling,"We show that the appropriate on-off switching of Josephson coupling between exciton-polaritons in coupled semiconductor microcavities can reveal the full capacity for generating entanglement with a recently proposed method which essentially enhances the nonlinearity of the system. The improvement achieved with this simple modulation of the coupling is substantial over the case where it is kept constant. The suggested procedure is expected to find also application in other research areas, where nonlinear interacting bosons are encountered.",1805.08600v1 2018-05-25,Generation of Spin Current from Lattice Distortion Dynamics: Spin-Orbit Routes,"Generation of spin current from lattice distortion dynamics in metals is studied with special attention on the effect of spin-orbit coupling. Treating the lattice distortion by local coordinate transformation, we calculate spin current and spin accumulation with the linear response theory. It is found that there are two routes to the spin-current generation, one via the spin Hall effect and the other via the spin accumulation. The present effect due to spin-orbit coupling can be comparable to, or even larger than, the one based on the spin-vorticity coupling in systems with strong spin-orbit coupling.",1805.10328v2 2008-07-09,Effect of different Dzyaloshinskii-Moriya interactions on entanglement in the Heisenberg XYZ chain,"In this paper, we study the thermal entanglement in a two-qubit Heisenberg XYZ system with different Dzyaloshinskii-Moriya (DM) couplings. We show that different DM coupling parameters have different influences on the entanglement and the critical temperature. In addition, we find that when $J_{i}$ ($i$-component spin coupling interaction) is the largest spin coupling coefficient, $D_{i}$ ($i$-component DM interaction) is the most efficient DM control parameter, which can be obtained by adjusting the direction of DM interaction.",0807.1457v2 2008-07-10,Coupling superconducting flux qubits at optimal point via dynamic decoupling with the quantum bus,"We propose a scheme with dc-control of finite bandwidth to implement two-qubit gate for superconducting flux qubits at the optimal point. We provide a detailed non-perturbative analysis on the dynamic evolution of the qubits interacting with a common quantum bus. An effective qubit-qubit coupling is induced while decoupling the quantum bus with proposed pulse sequences. The two-qubit gate is insensitive to the initial state of the quantum bus and applicable to non-perturbative coupling regime which enables rapid two-qubit operation. This scheme can be scaled up to multi-qubit coupling.",0807.1584v2 2008-07-22,Tests of flavor universality for neutrino-Z couplings in future neutrino experiments,"We investigate the physics potential of NuSOnG experiment to probe new physics contributions to Z-neutrino-neutrino couplings in muon-neutrino electron elastic and neutral-current deep-inelastic scattering processes. We employ an effective Lagrangian approach and do not a priori assume universality of the coupling of neutrinos to Z. We obtain 95% C.L. limits on possible universality violating couplings.",0807.3385v2 2008-07-22,Coherent-incoherent transition in a Cooper-pair-box coupled to a quantum oscillator: an equilibrium approach,"Temperature effect on quantum tunneling in a Cooper-pair-box coupled to a quantum oscillator is studied by both numerical and analytical calculations. It is found that, in strong coupling regions, coherent tunneling of a Cooper-pair-box can be destroyed by its coupling to a quantum oscillator and the tunneling becomes thermally activated as the temperature rises, leading to failure of the Cooper-pair-box. The transition temperature between the coherent tunneling and thermo-activated hopping is determined and physics analysis based on small polaron theory is also provided.",0807.3475v1 2008-07-28,Dissociation of Relativistic Projectiles with the Continuum-Discretized Coupled-Channels Method,"Relativistic effects in the breakup of weakly-bound nuclei at intermediate energies are studied by means of the continuum-discretized coupled-channels method with eikonal approximation. Nuclear coupling potentials with Lorentz contraction are newly included and those effects on breakup cross sections are investigated. We show that relativistic corrections lead to larger breakup cross sections. Coupled-channel effects on the breakup cross sections are also discussed.",0807.4485v2 2008-07-28,Echo Phenomena in Large Systems of Coupled Oscillators,"As exemplified by the Kuramoto model, large systems of coupled oscillators may undergo a transition to phase coherence with increasing coupling strength. It is shown that below the critical coupling strength for this transition such systems may be expected to exhibit `echo' phenomena: a stimulation by two successive pulses separated by a time interval tau leads to the spontaneous formation of response pulses at a time tau, 2 tau, 3 tau ..., after the second stimulus pulse. Analysis of this phenomenon, as well as illustrative numerical experiments, are presented. The theoretical significance and potential uses of echoes in such systems are discussed.",0807.4499v1 2008-07-30,Coherent switching by detuning a side-coupled quantum-dot system,"We investigate phase coherent electronic transport in an open quantum system, which consists of quantum dots side-coupled to a nanowire. It is demonstrated that coherent switching can be characterized by adjusting the electronic energy. A comparative analysis of quantum coherence effects in side-coupled quantum-dot systems is presented. Our results demonstrate the relevance of electronic nanodevices based on coherent switching by appropriately detuning the side-coupled quantum dots that are located at variable distance along a wire.",0807.4865v1 2008-07-31,Non-invasive detection of molecular bonds in quantum dots,"We performed charge detection on a lateral triple quantum dot with star-like geometry. The setup allows us to interpret the results in terms of two double dots with one common dot. One double dot features weak tunnel coupling and can be understood with atom-like electronic states, the other one is strongly coupled forming molecule-like states. In nonlinear measurements we identified patterns that can be analyzed in terms of the symmetry of tunneling rates. Those patterns strongly depend on the strength of interdot tunnel coupling and are completely different for atomic- or molecule-like coupled quantum dots allowing the non-invasive detection of molecular bonds.",0807.5095v1 2009-12-05,Delta-Interference of Two Friedel Resonances,"When a single resonator is coupled to a continuous spectrum one obtains a resonance of finite half-width. Such a resonance is known in many fields of physics. The Friedel resonance is an example where a d-impurity is dissolved in a simple metal. If two resonators are coupled to the continuous spectrum the resonances interfere. For identical coupling and frequencies one obtains two effective resonances. The effective coupling of one of them to the continuum can be tuned to zero yielding a delta-like resonance.",0912.1049v1 2009-12-18,"Properties from relativistic coupled-cluster without truncation: hyperfine constants of $^{25}{\rm Mg}^+$, $^{43}{\rm Ca}^+ $, $^{87}{\rm Sr}^+ $ and $^{137}{\rm Ba}^+$","We demonstrate an iterative scheme for coupled-cluster properties calculations without truncating the dressed properties operator. For validation, magnetic dipole hyperfine constants of alkaline Earth ions are calculated with relativistic coupled-cluster and role of electron correlation examined. Then, a detailed analysis of the higher order terms is carried out. Based on the results, we arrive at an optimal form of the dressed operator. Which we recommend for properties calculations with relativistic coupled-cluster theory.",0912.3681v2 2011-11-07,Constructive role of dissipation for driven coupled bosonic modes,"We theoretically investigate a system of two coupled bosonic modes subject to both dissipation and external driving. We show that in the steady state the degree of entanglement between the coupled bosonic modes can be enhanced by dissipation. The non-monotonic dependence of entanglement on the decay rates is observed when the bosonic modes are asymmetrically coupled to their local baths. This counterintuitive result opens a new way to better understand the interplay between noise and coherence in continuous variable systems driven away from equilibrium.",1111.1709v2 2011-11-14,Chameleon Effects on Small Scale Structure and the Baryonic Jeans Mass,"In the framework of Newtonian cosmology or general relativity it is simple to derive a mass scale below which collapsed structures are relatively devoid of baryons. We examine how the inclusion of a chameleon scalar field affects this baryonic Jeans mass, bearing in mind both the canonical case of a gravitational-strength coupling between the scalar field and matter, as well as the strong coupling regime wherein the coupling is very large. We find that baryon effects persist down to smaller scales in a chameleon theory than they do in ordinary general relativity, especially in the case of strong coupling. Several potentially observable consequences of this are identified.",1111.3227v1 2011-11-21,Multipartite Entanglement Generation Assisted by Inhomogeneous Coupling,"We show that controllable inhomogeneous coupling between two-level systems and a common data bus provides a fast mechanism to produce multipartite entanglement. Our proposal combines resonant interactions and engineering of coupling strengths---between the qubits and the single mode---leading to well defined entangled states. Furthermore, we show that, if the two-level systems interact dispersively with the quantized mode, engineering of coupling strengths allows the controlled access of the symmetric Hilbert space of qubits.",1111.4966v1 2011-11-22,z/-z Symmetry of spin-orbit coupling and weak localization in graphene,"We show that the influence of spin-orbit (SO) coupling on the weak localization effect for electrons in graphene depends on the lack or presence of z/-z symmetry in the system. While for z/-z asymmetric SO coupling, disordered graphene should display a weak anti-localization behavior at lowest temperature, z/-z symmetric coupling leads to an effective saturation of decoherence time which can be partially lifted by an in-plane magnetic field, thus, tending to restore the weak localization effect.",1111.5267v1 2011-11-22,Strong Coupling Optimization With Planar Spiral Resonators,"Planar spirals offer a highly scalable geometry appropriate for wireless power transfer via strongly coupled inductive resonators. We numerically derive a set of geometric scale and material independent coupling terms, and analyze a simple model to identify design considerations for a variety of different materials. We use our model to fabricate integrated planar resonators of handheld sizes, and optimize them to achieve high Q factors, comparable to much larger systems, and strong coupling over significant distances with approximately constant efficiency.",1111.5271v1 2011-11-29,Collective strong coupling in a lossy optical cavity,"We observe vacuum Rabi splitting in a lossy nearly confocal cavity indicating the strong coupling regime, despite a weak single-atom single-mode coupling. Strong collective interaction manifests itself in the typical $\sqrt{N}$-dependence of the normal mode splitting on the number of atoms $N$. The $TEM_{00}$-mode coupling parameters are $(g,\kappa,\gamma)=2\pi\times(0.12,0.8,2.6)$ MHz and up to $(1.33\pm 0.08)\times10^5$ cesium atoms were loaded into the mode volume.",1111.6770v1 2011-11-30,Sub-Poissonian photon statistics in a strongly coupled single-qubit laser,"We investigate qubit lasing in the strong coupling limit. The qubit is given by a Cooper-pair box, and population inversion is established by an additional third state, which can be addressed via quasiparticle tunneling. The coupling strength between oscillator and qubit is assumed to be much higher than the quasiparticle tunneling rate. We find that the photon number distribution is sub-Poissonian in this strong coupling limit.",1111.7184v1 2011-11-30,Ultra strong coupling regime and plasmon-polaritons in parabolic semiconductor quantum wells,"Ultra strong coupling is studied in a modulation-doped parabolic potential well coupled to an inductance-capacitance resonant circuit. In this system, in accordance to Kohn's theorem, strong reduction of the energy level separation caused by the electron-electron interaction compensates the depolarization shift. As a result, a very large ratio of 27% of the Rabi frequency to the center resonance frequency as well as a polariton gap of width 2? ? 670GHz are observed, suggesting parabolic quantum wells as the system of choice in order to explore the ultra-strong coupling regime.",1111.7266v2 2012-01-16,Amplitude death in complex networks induced by environment,"We present a mechanism for amplitude death in coupled nonlinear dynamical systems on a complex network having interactions with a common environment-like external system. We develop a general stability analysis that is valid for any network topology and obtain the threshold values of coupling constants for the onset of amplitude death. An important outcome of our study is a universal relation between the critical coupling strength and the largest non-zero eigenvalue of the coupling matrix. Our results are fully supported by the detailed numerical analysis for different network topologies.",1201.3244v2 2012-01-20,Josephson dynamics of a spin-orbit coupled Bose-Einstein condensate in a double well potential,"We investigate the quantum dynamics of an experimentally realized spin-orbit coupled Bose-Einstein condensate in a double well potential. The spin-orbit coupling can significantly enhance the atomic inter-well tunneling. We find the coexistence of internal and external Josephson effects in the system, which are moreover inherently coupled in a complicated form even in the absence of interatomic interactions. Moreover, we show that the spin-dependent tunneling between two wells can induce a net atomic spin current referred as spin Josephson effects. Such novel spin Josephson effects can be observable for realistically experimental conditions.",1201.4306v1 2012-01-29,Some Unfinished Thoughts on Strong Yukawa Couplings,"Yukawa couplings of electroweak Goldstone bosons can be inferred from experiment, but the existence of an elementary Higgs boson is not yet an established fact. If a sequential chiral quark generation does exist, it would bring us now into the strong Yukawa coupling regime. Guided by a Bethe--Salpeter equation approach, we postulate that the leading collapse state, the (heavy) isotriplet and color-singlet $\pi_1$ meson, becomes the Goldstone boson $G$ itself. Viewing it as a deeply bound state, a gap equation is constructed. This ""`bootstrap"" picture for electroweak symmetry breaking relies on strong Yukawa coupling, without providing any theory of the latter.",1201.6029v1 2012-04-04,Avoiding dark states in open quantum systems by tailored initial correlations,"We study the transport of excitations on a V-shaped network of three coupled two-level systems that are subjected to an environment that induces incoherent hopping between the nodes. Two of the nodes are coupled to a source while the third node is coupled to a drain. A common feature of these networks is the existence of a dark-state that blocks the transport to the drain. Here we propose a means to avoid this state by a suitable choice of initial correlations, induced by a source that is common to both coupled nodes.",1204.0954v1 2012-04-08,On the dissipative non-minimal braneworld inflation,"We study the effects of the non-minimal coupling on the dissipative dynamics of the warm inflation in a braneworld setup, where the inflaton field is non-minimally coupled to induced gravity on the warped DGP brane. We study with details the effects of the non-minimal coupling and dissipation on the inflationary dynamics on the normal DGP branch of this scenario in the high-dissipation and high-energy regime. We show that incorporation of the non-minimal coupling in this setup decreases the number of e-folds relative to the minimal case. We also compare our model parameters with recent observational data.",1204.1714v1 2012-04-26,The Lightest Higgs Boson Mass in the MSSM with Strongly Interacting Spectators,"We propose a new mechanism for producing a Higgs boson mass near 125 GeV within the MSSM. By coupling the MSSM Higgs boson to a set of strongly interacting fields, large corrections to the Higgs quartic coupling are induced. Although the Higgs doublets do not participate in the strong dynamics, they feel the effects of the strongly coupled sector via (semi-)perturbative interactions. These same strong dynamics are also capable of generating the $\mu$-term. Additionally, this strong sector is in the conformal window, which drives the couplings to an infrared fixed point and naturally generates model parameters of the appropriate size.",1204.6085v1 2013-09-08,Conformally Coupled Induced Gravity as an Infrared Fixed Point,"We have found that the conformally coupled induced gravity can be an infrared fixed point of induced gravity with Yukawa couplings with matter. The late time cosmology with a uniform mean matter distribution can be described by the conformally coupled induced gravity, which has an emergent global conformal symmetry in the cosmic scale. Aiming to resolve the puzzles for the dark energy, we have obtained exact cosmological equations and determined the dark energy density, the matter density, and the jerk parameter in the present universe based on the recent observational cosmic expansion data for $a/H^{2}$.",1309.1990v1 2013-09-19,Conformally coupled inflation,"A massive scalar field in a curved spacetime can propagate along the light cone, a causal pathology, which can, in principle, be eliminated only if the scalar couples conformally to the Ricci curvature of spacetime. This property mandates conformal coupling for the field driving inflation in the early universe. During slow-roll inflation, this coupling can cause super-acceleration and, as a signature, a blue spectrum of primordial gravitational waves.",1309.4900v1 2013-09-25,Spontaneous electric polarization and Magneto-dielectric coupling in ceramic multiferroic Co3TeO6,"We report observation of magneto-electric and magneto-dielectric couplings in ceramic Co3TeO6. Temperature dependent DC magnetization and dielectric constant measurements together indicate coupling between magnetic order and electronic polarization. Strong anomaly in dielectric constant at ~ 18K in zero magnetic field indicates presence of spontaneous polarization. Observations like weak ferromagnetic order at lower temperature, field and temperature dependences of the ferroelectric transition provide experimental verification of the recent theoretical proposal by P. Toledano et al., Phys. Rev. B 85, 214439 (2012). We provide direct evidence of spin-phonon coupling as possible origin of magnetic order.",1309.6417v1 2014-05-16,Gravitational-Wave Mediated Preheating,"We propose a new preheating mechanism through the coupling of the gravitational field to both the inflaton and matter fields, without direct inflaton-matter couplings. The inflaton transfers power to the matter fields through interactions with gravitational waves, which are exponentially enhanced due to an inflation-graviton coupling. One such coupling is the product of the inflaton to the Pontryagin density, as in dynamical Chern-Simons gravity. The energy scales involved are constrained by requiring that preheating happens fast during matter domination.",1405.4288v2 2014-05-21,Synchronization of oscillators in a Kuramoto-type model with generic coupling,"We study synchronization properties of coupled oscillators on networks that allow description in terms of global mean field coupling. These models generalize the standard Kuramoto-Sakaguchi model, allowing for different contributions of oscillators to the mean field and to different forces from the mean field on oscillators. We present the explicit solutions of self-consistency equations for the amplitude and frequency of the mean field in a parametric form, valid for noise-free and noise-driven oscillators. As an example we consider spatially spreaded oscillators, for which the coupling properties are determined by finite velocity of signal propagation.",1405.5464v1 2014-05-27,Lattice mapping for many-body open quantum systems and its application to atoms in photonic cystals,"We present a derivation that maps the original problem of a many body open quantum system (OQS) coupled to a harmonic oscillator reservoir into that of a many body OQS coupled to a lattice of harmonic oscillators. The present method is particularly suitable to analyse the dynamics of atoms arranged in a periodic structure and coupled the EM field within a photonic crystal. It allows to solve the dynamics of a many body OQS with methods alternative to the commonly used master, stochastic Schr\""{o}dinger and Heisenberg equations, and thus to reach regimes well beyond the weak coupling and Born-Markov approximations.",1405.6995v2 2014-06-11,Strongly bound yet light bipolarons for double-well electron-phonon coupling,"We use the Momentum Average approximation (MA) to study the ground-state properties of strongly bound bipolarons in the double-well electron-phonon (el-ph) coupling model, which describes certain intercalated lattices where the linear term in the el-ph coupling vanishes due tosymmetry. We show that this model predicts the existence of strongly bound yet lightweight bipolarons in some regions of the parameter space. This provides a novel mechanism for the appearance of such bipolarons, in addition to long-range el-ph coupling and special lattice geometries.",1406.3072v1 2014-06-17,The lattice QCD phase diagram in and away from the strong coupling limit,"We study lattice QCD with four flavors of staggered quarks. In the limit of infinite gauge coupling, ""dual"" variables can be introduced, which render the finite-density sign problem mild and allow a full determination of the $\mu-T$ phase diagram by Monte Carlo simulations, also in the chiral limit. However, the continuum limit coincides with the weak coupling limit. We propose a strong-coupling expansion approach towards the continuum limit. We show first results, including the phase diagram and its chiral critical point, from this expansion truncated to next-to-leading order.",1406.4397v1 2016-05-02,Coupled-layer description of topological crystalline insulators,"We introduce a coupled-layer construction to describe three-dimensional topological crystalline insulators protected by reflection symmetry. Our approach uses stacks of weakly-coupled two-dimensional Chern insulators to produce topological crystalline insulators in one higher dimension, with tunable number and location of surface Dirac cones. As an application of our formalism, we turn to a simplified model of topological crystalline insulator SnTe, showing that its protected surface states can be described using the coupled layer construction.",1605.00652v2 2016-05-08,Symmetry-broken states on networks of coupled oscillators,"When identical oscillators are coupled together in a network, dynamical steady states are often assumed to reflect network symmetries. Here we show that alternative persistent states may also exist that break the symmetries of the underlying coupling network. We further show that these symmetry-broken coexistent states are analogous to those dubbed ""chimera states,"" which can occur when identical oscillators are coupled to one another in identical ways.",1605.02271v1 2016-05-10,Coherently coupling distinct spin ensembles through a high-$T_c$ superconducting resonator,"The problem of coupling multiple spin ensembles through cavity photons is revisited by using PyBTM organic radicals and a high-$T_c$ superconducting coplanar resonator. An exceptionally strong coupling is obtained and up to three spin ensembles are simultaneously coupled. The ensembles are made physically distinguishable by chemically varying the $g$ factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures.",1605.02879v1 2016-05-10,Magnetic-field-mediated coupling and control in hybrid atomic-nanomechanical systems,"Magnetically coupled hybrid quantum systems enable robust quantum state control through Landau-Zener transitions. Here, we show that an ultracold atomic sample coupled to a nanomechanical resonator via oscillating magnetic fields can be used to cool the resonator's mechanical motion, to measure the mechanical temperature, and to enable entanglement of these mesoscopic objects. We calculate the expected coupling for both permanent-magnet and current-conducting nanostring resonators and describe how this hybridization is attainable using recently developed fabrication techniques, including SiN nanostrings and atom chips.",1605.03126v1 2016-05-20,Breathers in Hamiltonian ${\cal PT}$-symmetric chains of coupled pendula under a resonant periodic force,"We derive a Hamiltonian version of the ${\cal PT}$-symmetric discrete nonlinear Schr\""{o}dinger equation that describes synchronized dynamics of coupled pendula driven by a periodic movement of their common strings. In the limit of weak coupling between the pendula, we classify the existence and spectral stability of breathers (time-periodic solutions localized in the lattice) supported near one pair of coupled pendula. Orbital stability or instability of breathers is proved in a subset of the existence region.",1605.06455v1 2016-05-29,Wasserstein approximations of the Lévy area random walk via polynomial perturbations of Gaussian distributions,"We construct a coupling between the random walk composed of L\'evy area increments from a $d$-dimensional Brownian motion and a random walk composed of quadratic polynomials of Gaussian random variables. This coupling construction is used to produce a new pathwise approximation scheme for stochastic differential equations in the preprint [Flint-Lyons-2015]. The coupling arguments of the present paper are based extensively on the recent coupling results of Davie concerning a multidimensional variant of the Koml\'os-Major-Tusn\'ady theorem and Wasserstein estimates for polynomial perturbations of Gaussian measures.",1605.08996v1 2016-05-24,Non- Markovian Quantum Stochastic Equation For Two Coupled Oscillators,"The system of nonlinear Langevin equations was obtained by using Hamiltonian's operator of two coupling quantum oscillators which are interacting with heat bath. By using the analytical solution of these equations, the analytical expressions for transport coefficients was found. Generalized Langevin equations and fluctuation-dissipation relations are derived for the case of a nonlinear non-Markovian noise. The explicit expressions for the time-dependent friction and diffusion coefficients are presented for the case of linear couplings in the coordinate between the collective two coupled harmonic oscillators and heat bath.",1605.09327v1 2016-08-18,Amplitude determinant coupled cluster with pairwise doubles,"Recently developed pair coupled cluster doubles (pCCD) theory successfully reproduces doubly occupied configuration interaction (DOCI) with mean field cost. However, the projective nature of pCCD makes the method non-variational and thus hard to improve systematically. As a variational alternative, we explore the idea of coupled-cluster-like expansions based on amplitude determinants and develop a specific theory similar to pCCD based on determinants of pairwise doubles. The new ansatz admits a variational treatment through Monte Carlo methods while remaining size-consistent and, crucially, polynomial cost. In the dissociations of LiH, HF, H2O and N2, the method performs very similarly to pCCD and DOCI, suggesting that coupled-cluster-like ansatzes and variational evaluation may not be mutually exclusive.",1608.05195v1 2017-06-07,Some complexity and approximation results for coupled-tasks scheduling problem according to topology,"We consider the makespan minimization coupled-tasks problem in presence of compatibility constraints with a specified topology. In particular, we focus on stretched coupled-tasks, i.e. coupled-tasks having the same sub-tasks execution time and idle time duration. We study several problems in framework of classic complexity and approximation for which the compatibility graph is bipartite (star, chain,. . .). In such a context, we design some efficient polynomial-time approximation algorithms for an intractable scheduling problem according to some parameters.",1706.02214v1 2017-06-24,Magnon cotunneling through a quantum dot,"I consider a single-level quantum dot coupled to two reservoirs of spin waves (magnons). Such systems have been studied recently from the point of view of possible coupling between electronic and magnonic spin currents. However, usually weakly coupled systems were investigated. When coupling between the dot and reservoirs is not weak, then higher order processes play a role and have to be included. Here I consider cotunneling of magnons through a spin-occupied quantum dot, which can be understood as a magnon (spin) leakage current in analogy to leakage currents in charge-based electronics. Particular emphasis has been put on investigating the effect of magnetic field and temperature difference between the magnonic reservoirs.",1706.07914v1 2017-06-26,Strong Coupling Limit of A Family of Chern-Simons-matter Theories,"We investigate the strong coupling limit of a family of Chern-Simons-matter theories in the planar limit. The family consists of ${\cal N}=3$ theories with the gauge group ${\rm U}(N_1)_{k_1}\times{\rm U}(N_2)_{k_2}$ coupled to $n$ bi-fundamental hypermultiplets. All observables which can be determined from the planar resolvent turn out to have finite limits in the large 't Hooft coupling limit. Possible gravity duals are briefly discussed. We observe that Kac-Moody algebras govern the structure of the planar spectral curves of the theories.",1706.08204v2 2017-10-10,Flipping-shuttle oscillations of bright one- and two-dimensional solitons in spin-orbit-coupled Bose-Einstein condensates with Rabi mixing,"We analyze a possibility of macroscopic quantum effects in the form of coupled structural oscillations and shuttle motion of bright two-component spin-orbit-coupled striped (one-dimensional, 1D) and semi-vortex (two-dimensional, 2D) matter-wave solitons, under the action of linear mixing (Rabi coupling) between the components. In 1D, the intrinsic oscillations manifest themselves as flippings between spatially even and odd components of striped solitons, while in 2D the system features periodic transitions between zero-vorticity and vortical components of semi-vortex solitons. The consideration is performed by means of a combination of analytical and numerical methods.",1710.03664v1 2017-10-13,Dynamical analysis for a scalar-tensor model with Gauss-Bonnet and non-minimal couplings,"We study the autonomous system for a scalar-tensor model of dark energy with Gauss-Bonnet and non-minimal couplings. The critical points describe important stable asymptotic scenarios including quintessence, phantom and de Sitter attractor solutions. Two functional forms for the coupling functions and the scalar potential were considered: power-law and exponential functions of the scalar field. For the exponential functions the existence of stable quintessence, phantom or de Sitter solutions, allows an asymptotic behavior where the effective Newtonian coupling becomes constant. The phantom solutions could be realized without appealing to ghost degrees of freedom. Transient inflationary and radiation dominated phases can also be described.",1710.04760v1 2017-10-25,On the Scarcity of Weak Coupling in the String Landscape,"We study the geometric requirements on a threefold base for the corresponding F-theory compactification to admit a weakly-coupled type IIB limit. We examine both the standard Sen limit and a more restrictive limit, and determine conditions sufficient for their non-existence for both toric bases and more general algebraic bases. In a large ensemble of geometries generated by base changing resolutions we derive an upper bound on the frequency with which a weak-coupling limit may occur, and find that such limits are extremely rare. Our results sharply quantify the widely held notion that the vast number of weakly-coupled IIB vacua is but a tiny fraction of the landscape.",1710.09374v1 2017-10-30,Star network synchronization led by strong coupling-induced frequency squeezing,"We consider a star network consisting of N oscillators coupled to a central one which in turn is coupled to an infinite set of oscillators (reservoir), which makes it leaking. Two of the N + 1 normal modes are dissipating, while the remaining N - 1 lie in a frequency range which is more and more squeezed as the coupling strengths increase, which realizes synchronization of the single parts of the system.",1710.11025v1 2017-10-31,Synchronization in Networks of Diffusively Coupled Nonlinear Systems: Robustness Against Time-Delays,"In this manuscript, we study the problem of robust synchronization in networks of diffusively time-delayed coupled nonlinear systems. In particular, we prove that, under some mild conditions on the input-output dynamics of the systems and the network topology, there always exists a unimodal region in the parameter space (coupling strength versus time-delay), such that if they belong to this region, the systems synchronize. Moreover, we show how this unimodal region scales with the network topology, which, in turn, provides useful insights on how to design the network topology to maximize robustness against time-delays. The results are illustrated by extensive simulation experiments of time-delayed coupled Hindmarsh-Rose neural chaotic oscillators.",1710.11276v1 2017-12-14,"Coupled Hall-Littlewood functions, vertex operators and the $q$-boson model","In this paper, we firstly give the definition of the coupled Hall-Littlewood function and its realization in terms of vertex operators. Then we construct the representation of the two-site generalized $q$-boson model in the algebra of coupled Hall-Littlewood functions. Finally, we find that the vertex operators which generate coupled Hall-Littlewood functions can also be used to obtain the partition function of the A-model topological string on the conifold.",1712.05093v1 2018-09-08,Triple Higgs Boson Coupling in Gauge-Higgs Unification,"We consider the triple coupling of the Higgs boson in the context of the gauge-Higgs unification scenario. We show that the triple coupling of the Higgs boson in this scenario generically deviates from SM prediction since the Higgs potential in this scenario has a periodicity. We calculate the coupling in the five-dimensional $SU(3)$ x $U(1)_X$ gauge-Higgs unification model and obtain 70% deviation from the SM prediction.",1809.02748v2 2019-09-11,On String Theory Expectations for Photon Couplings to Axion-Like Particles,"ALP-photon couplings are modeled in large ensembles of string vacua and random matrix theories. In all cases, the effective coupling increases polynomially in the number of ALPs, of which hundreds or thousands are expected in the string ensembles, many of which are ultralight. The expected value of the couplings $g_{a\gamma\gamma}\simeq 10^{-12}\text{GeV}^{-1} - 10^{-10}\text{GeV}^{-1}$ provide viable targets for future x-ray telescopes and axion helioscopes, and in some cases are already in tension with existing data.",1909.05257v1 2020-12-10,Impact of independent reservoirs on the quantum Zeno and anti-Zeno effects,"In this paper, we look into what happens to a quantum system under repeated measurements if it interacts with two independent reservoirs. In particular, we look at the behavior of a two-level system interacting with reservoirs consisting of harmonic oscillators. The interaction with one reservoir is weak with a dissipative-type coupling, while the interaction with the other reservoir is strong with a dephasing-type coupling. Using a polaron transformation, we show that the presence of the strongly coupled reservoir can actually reduce the decay rate of the quantum system due to the effect of the weakly-coupled reservoir.",2012.05574v1 2020-12-12,Chirality-driven delocalization in disordered waveguide-coupled quantum arrays,"We study theoretically the competition between directional asymmetric coupling and disorder in a one-dimensional array of quantum emitters chirally coupled through a waveguide mode. Our calculation reveals highly nontrivial phase diagram for the eigenstates spatial profile, nonmonotonously depending on the disorder and directionality strength. The increase of the coupling asymmetry drives the transition from Anderson localization in the bulk through delocalized states to chirality-induced localization at the array edge. Counterintuitively, this transition is not smeared by strong disorder but becomes sharper instead. Our findings could be important for the rapidly developing field of the waveguide quantum electrodynamics, where the chiral interactions and disorder play crucial roles.",2012.06886v2 2020-12-26,Optimization of telescope focal ratios for MLA-fiber coupled Integral Field Units,"We have developed an analytic model for generic image transfer using microlens-coupled fibers to determine the telescope input beam speed that optimizes the lenslet clear aperture and minimizes fiber focal-ratio degradation. Assuming fibers are fed at f/3.5 by the lenslets, our study shows that f/11 is the optimum telescope beam speed to feed a lenslet coupled to a fiber with a 100um diameter core. These considerations are relevant for design of high-efficiency, dedicated survey telescopes that employ lenslet-coupled fiber systems.",2012.13704v1 2020-12-27,Microwave spectroscopy of spin-orbit coupled states: energy detuning versus interdot coupling modulation,"We study the AC field induced current peaks of a spin blockaded double quantum dot with spin-orbit interaction. The AC field modulates either the interdot tunnel coupling or the energy detuning, and we choose the AC field frequency range to induce two singlet-triplet transitions giving rise to two current peaks. We show that for a large detuning the two current peaks can be significantly stronger when the AC field modulates the tunnel coupling, thus making the detection of the spin-orbit gap more efficient. We also demonstrate the importance of the time dependence of the spin-orbit interaction.",2012.13914v1 2000-06-09,A Consistent Treatment of Strong Coupling in Disordered Superconducting Films,"We develop a consistent treatment of disorder effects in strong coupling superconductors. We use two different approaches, starting either from above or below the transition temperature, and show their equivalence. The normal state approach is a natural extension of a recently developed non-perturbative resummation technique. For the superconducting state we extend the standard Eliashberg theory to include disorder effects. We obtain a compact set of equations which are physically transparent and easy to use. They correctly reproduce the usual strong coupling results and disordered perturbation theory results in the appropriate limits. We numerically solve these equations to obtain transition temperature as a function of disorder for different phonon couplings.",0006160v1 2012-05-01,Entangling homogeneously broadened matter qubits in the weak-coupling cavity-QED regime,"In distributed quantum information processing, flying photons entangle matter qubits confined in cavities. However, when a matter qubit is homogeneously broadened, the strong-coupling regime of cavity QED is typically required, which is hard to realize in actual experimental setups. Here, we show that a high-fidelity entanglement operation is possible even in the weak-coupling regime in which dampings (dephasing, spontaneous emission, and cavity leakage) overwhelm the coherent coupling between a qubit and the cavity. Our proposal enables distributed quantum information processing to be performed using much less demanding technology than previously.",1205.0060v1 2012-05-21,Single Top Quark Production at DØ,"We present new measurements of the single top quark production cross section in \ppbar collisions at $\sqrt{s} = 1.96 TeV$ using data corresponding to 5.4 \ifb of integrated luminosity collected by the {\dzero} detector at the Fermilab Tevatron collider. The large mass of the top quark, close to the electroweak symmetry-breaking scale, makes it a good candidate for probing physics beyond the Standard Model, including possible anomalous couplings. We examine the data to study the Lorentz structure of the $Wtb$ coupling, and find that the data prefer the left-handed vector coupling, and set upper limits on the anomalous couplings.",1205.4501v1 2017-05-29,Multiscale simulation on shearing transitions of thin-film lubrication with multi-layer molecules,"Shearing transitions of multi-layer molecularly thin-film lubrication systems in variations of the film-substrate coupling strength and the load are studied by using a multiscale method. Three kinds of the interlayer slips found in decreasing the coupling strength are in qualitative agreement with experimental results. Although tribological behaviors are almost insensitive to the smaller coupling strength, they and the effective film thickness are enlarged more and more as the larger one increases. When the load increases, the tribological behaviors are similar to those in increasing coupling strength, but the effective film thickness is opposite.",1705.10008v1 2017-09-06,No nonminimally coupled massless scalar hair for spherically symmetric neutral reflecting stars,"It has recently been proved that horizonless compact stars with reflecting boundary conditions {\it cannot} support spatially regular matter configurations made of minimally coupled scalar fields, vector fields, and tensor fields. In the present paper we extend this intriguing no-hair property to the physically interesting regime of scalar fields with {\it nonminimal} coupling to gravity. In particular, we prove that static spherically symmetric configurations made of nonminimally coupled massless scalar fields cannot be supported by compact reflecting stars.",1709.01933v1 2018-03-05,Dynamics of a system of coupled inverted pendula with vertical forcing,"Dynamical stabilization of an inverted pendulum through vertical movement of the pivot is a well-known counterintuitive phenomenon in classical mechanics. This system is also known as Kapitza pendulum and the stability can be explained with the aid of effective potential. We explore the effect of many body interaction for such a system. Our numerical analysis shows that interaction between pendula generally degrades the dynamical stability of each pendulum. This effect is more pronounced in nearest neighbour coupling than all-to-all coupling and stability improves with the increase of the system size. We report development of beats and clustering in network of coupled pendula.",1803.01643v1 2018-03-16,Exchange-correlation functionals of i-DFT for asymmetrically coupled leads,"A recently proposed density functional approach for steady-state transport through nanoscale systems (called i-DFT) is used to investigate junctions which are asymmetrically coupled to the leads and biased with asymmetric voltage drops. In the latter case, the system can simply be transformed to a physically equivalent one with symmetric voltage drop by a total energy shift of the entire system. For the former case, known exchange correlation gate and bias functionals have to be generalized to take into account the asymmetric coupling to the leads. We show how differential conductance spectra of the constant interaction model evolve with increasing asymmetry of both voltage drops and coupling to the leads.",1803.06307v1 2018-03-24,Ground state properties of Ising chain with random monomer-dimer couplings,"We study analytically the one-dimensional Ising model with a random binary distribution of ferromagnetic and antiferromagnetic exchange couplings at zero temperature. We introduce correlations in the disorder by assigning a dimer of one type of coupling with probability $x$, and a monomer of the other type with probability $1-x$. We find that the magnetization behaves differently from the original binary model. In particular, depending on which type of coupling comes in dimers, magnetization jumps vanish at a certain set of critical fields. We explain the results based on the structure of ground state spin configuration.",1803.09069v1 2018-03-25,Enhanced photon-phonon coupling via dimerization in one-dimensional optomechanical crystals,"We show that dimerization of an optomechanical crystal lattice, which leads to folding of the band diagram, can couple flexural mechanical modes to optical fields within the unit cell via radiation pressure. When compared to currently realized crystals, a substantial improvement in the coupling between photons and phonons is found. For experimental verification, we implement a dimerized lattice in a silicon optomechanical nanobeam cavity and measure a vacuum coupling rate of $g_0/2\pi=1.7MHz$ between an optical resonance at $\lambda_{c} = 1545nm$ and a mechanical resonance at 1.14GHz.",1803.09324v1 2018-06-06,Detection of emitter-resonator coupling strength in quantum Rabi model via an auxiliary resonator,"In this paper, we propose a theoretical scheme to detect the emitter-resonator coupling strength in the ultra-strong coupling regime in the quantum Rabi model via introducing an auxiliary resonator. We demonstrate the total system as a two-mode Rabi model and obtain the ground state by the transformed rotating wave approximation, which is shown to be superior to the usually applied rotating wave approximation. Here, the coupling strength is detected by monitoring the average excitation number in the auxiliary resonator and the sensitivity of the detection scheme is discussed analytically.",1806.01971v2 2018-07-17,Nonlinear coupling of flow harmonics in heavy-ion collisions,"Anisotropic flow coefficients beyond triangular flow receive important contributions from lower-order harmonics through nonlinear coupling. We present a theoretical framework which allows one to quantify the contribution induced by such nonlinear couplings to any flow harmonic of any order. We show the effectiveness of this formalism through an application to hexagonal flow, $V_6$. We study, in particular, the coupling of $V_6$ to triangular flow, $V_3$, in Pb+Pb collisions at $~\sqrt[]{s}=2.76$ TeV, using both Large Hadron Collider data and event-by-event hydrodynamic calculations.",1807.06382v1 2018-12-03,Phase transition in a Rabi coupled two-component Bose-Einstein condensate,"This paper deals with the study of the phase transition of the wave functions of a segregated two-component Bose-Einstein condensate under Rabi coupling. This yields a system of two coupled ODE's where the Rabi coupling is linear in the other wave function and acts against segregation. We prove estimates on the asymptotic behaviour of the wave functions, as the strength of the interaction gets strong or weak. We also derive limiting problems in both cases.",1812.00618v1 2018-12-11,Corrections to the Higgs Mode Masses in Superfluid 3He,"Superfluid 3He has a rich spectrum of collective modes with both massive and massless excitations. The masses of these modes can be precisely measured using acoustic spectroscopy and fit to theoretical models. Prior comparisons of the experimental results with theory did not include strong-coupling effects beyond the weak-coupling-plus BCS model, so-called non-trivial strong-coupling corrections. In this work we utilize recent strong-coupling calculations to determine the Higgs masses and find consistency between experiments that relate them to a sub-dominant $f$-wave pairing strength.",1812.04545v2 2018-12-12,Polaron-induced band renormalization due to linear and quadratic electron-phonon coupling,"We present a novel approach to electron-lattice interaction beyond the linear-coupling regime. Based on the solution of a Holstein-Peierls-type model, we derive explicit analytical expressions for the eigenvalue spectrum of the Hamiltonian, resulting in a narrowing of bands as a function of temperature. Our approach enables the intuitive interpretation in terms of quasiparticles, i.e. polaron bands and dressed-phonon frequencies. Being nonperturbative, the formalism also applies in the strong-coupling case. We apply it to the organic crystal naphthalene, with the coupling strengths obtained by \textit{ab initio} calculations.",1812.04793v1 2018-12-15,Eta-nucleon and eta-prime-nucleon coupling constants in QCD and the role of gluons,"Coupling constants of $\eta$ and $\eta^{\prime}$ mesons with nucleons have been calculated using the method of QCD sum rules. Starting from vacuum-to-meson correlation function of interpolating fields of two nucleons, its matrix element with respect to nucleon spinors has been considered. Coupling constants at the physical points have been estimated from extrapolation of results obtained at two other points. Anomalous glue has been found to give substantial contribution to the coupling constants and also accounts for a significant OZI-rule violation.",1812.06275v2 2018-12-21,Quantifying coherence of chimera states in coupled chaotic systems,"Chimera states in coupled oscillator systems present both spatially coherent and incoherent domains. The number and size of these domains depend on many factors like the system parameters and initial conditions. Systematic investigations of these dependences require a quantification of the degree of coherence present in a given snapshot spatial pattern. We propose the use of a local order parameter magnitude combined with the counting of the corresponding plateaus so as to provide such quantification. We use this technique in non-locally coupled lattices of chaotic logistic maps and chaotic R\""ossler systems to investigate the dependence of the degree of coherence on the coupling strength.",1812.09306v1 2018-12-24,Motion Blur removal via Coupled Autoencoder,"In this paper a joint optimization technique has been proposed for coupled autoencoder which learns the autoencoder weights and coupling map (between source and target) simultaneously. The technique is applicable to any transfer learning problem. In this work, we propose a new formulation that recasts deblurring as a transfer learning problem, it is solved using the proposed coupled autoencoder. The proposed technique can operate on-the-fly, since it does not require solving any costly inverse problem. Experiments have been carried out on state-of-the-art techniques, our method yields better quality images in shorter operating times.",1812.09888v1 2019-02-18,Scalable quantum computer with superconducting circuits in the ultrastrong coupling regime,"So far, superconducting quantum computers have certain constraints on qubit connectivity, such as nearest-neighbor couplings. To overcome this limitation, we propose a scalable architecture to simultaneously connect several pairs of distant qubits via a dispersively coupled quantum bus. The building-block of the bus is composed of orthogonal coplanar waveguide resonators connected through ancillary flux qubits working in the ultrastrong coupling regime. This regime activates virtual processes that boost the effective qubit-qubit interaction, which results in quantum gates on the nanosecond timescale. The interaction is switchable and preserves the coherence of the qubits.",1902.06569v2 2019-03-01,The vanishing discount problem for monotone systems of Hamilton-Jacobi equations. Part 1: linear coupling,"We establish a convergence theorem for the vanishing discount problem for a weakly coupled system of Hamilton-Jacobi equations. The crucial step is the introduction of Mather measures and their relatives for the system, which we call respectively viscosity Mather and Green-Poisson measures. This is done by the convex duality and the duality between the space of continuous functions on a compact set and the space of Borel measures on it. This is part 1 of our study of the vanishing discount problem for systems, which focuses on the linear coupling, while part 2 will be concerned with nonlinear coupling.",1903.00244v2 2019-03-04,Continuous ground-state degeneracy of classical dipoles on regular lattices,"Dipolar interactions are crucial in the modeling of many complex magnetic systems, such as the pyrochlores and artificial spin systems. Remarkably, many classical dipolar coupled spin systems exhibit a continuous ground-state degeneracy, which is unexpected as the Hamiltonian does not possess a continuous symmetry. In this paper, we explain, how such a finite point-symmetry leads to a continuous ground-state degeneracy of specific classical dipolar-coupled systems. This work, therefore, provides new insight into the theory of classical dipolar-coupled spin-systems and opens the way to understand more complex dipolar coupled systems.",1903.01160v2 2019-03-05,Phonon sidebands of color centers in hexagonal boron nitride,"Low temperature photoluminescence spectra of a color center in hexagonal boron nitride are analyzed. The acoustic phonon sideband can be described by a deformation coupling proportional to strain to a phonon bath that is effectively two dimensional. The optical phonon band is described by Frohlich coupling to the LO-branches, and a deformation coupling proportional to lattice displacement for the TO-branch. The resonances expressed in the optical band vary from defect to defect, in some emitters, coupling to out-of-plane polarized phonons is reported.",1903.01751v1 2019-03-09,Coupled Decorated Membrane Resonators with Large Willis Coupling,"We report the experimental studies on an acoustic scatterer consisting of a pair of coupled decorated membrane resonators (DMRs) that exhibits near extreme contrast in reflection asymmetry and strong Willis coupling coefficient with amplitude of 2.5 and polarizability cross term of 1.1 x 10-8 ms2. The design is based on the theoretical analysis using the Greens function formulism we developed earlier. The clean line shapes of the real and the imaginary parts of the Willis coefficient clear show, even by visual inspection, that the Kramers-Kronig relations are satisfied. Theoretical analysis agrees well with the major features of the experimental results.",1903.03743v2 2019-04-12,The coupling effect of Lipschitz regularization in deep neural networks,"We investigate robustness of deep feed-forward neural networks when input data are subject to random uncertainties. More specifically, we consider regularization of the network by its Lipschitz constant and emphasize its role. We highlight the fact that this regularization is not only a way to control the magnitude of the weights but has also a coupling effect on the network weights accross the layers. We claim and show evidence on a dataset that this coupling effect brings a tradeoff between robustness and expressiveness of the network. This suggests that Lipschitz regularization should be carefully implemented so as to maintain coupling accross layers.",1904.06253v1 2019-04-12,Spatially Coupled LDPC Codes with Non-uniform Coupling for Improved Decoding Speed,"We consider spatially coupled low-density parity-check codes with finite smoothing parameters. A finite smoothing parameter is important for designing practical codes that are decoded using low-complexity windowed decoders. By optimizing the amount of coupling between spatial positions, we show that we can construct codes with improved decoding speed compared with conventional, uniform smoothing constructions. This leads to a significantly better performance under decoder complexity constraints while keeping the degree distribution regular. We optimize smoothing configurations using differential evolution and illustrate the performance gains by means of a simulation.",1904.07026v2 2019-08-15,Chaotic inflation with four-form couplings,"We consider chaotic inflation models with a pseudo-scalar field containing the general couplings to the four-form flux. The four-form mixing with the pseudo-scalar field induces a quadratic potential for inflaton while the coexisting four-form mixing with graviton generates a non-minimal gravity coupling for inflaton. The shift symmetry is respected by the derived inflaton couplings and it is broken spontaneously only by the fixed four-form flux. We discuss the success of inflationary predictions and robustness against higher order terms. Finally, the built-in reheating mechanism is also addressed.",1908.05475v2 2019-08-27,On the Charge Dependence of the Pion-Nucleon Coupling Constant and Nucleon-Nucleon Low-Energy Scattering Parameters,"The simple model describing charge independence and charge symmetry breaking of the pion-nucleon coupling constant is proposed. The model, which has simple physical meaning and foundation, suggests directly proportional dependence of the pion-nucleon coupling constants on the masses of interacting nucleons and pions. Charge dependence of the pion-nucleon coupling constant and the $^{1}S_{0}$-state low-energy nucleon-nucleon ($NN$) scattering parameters are studied on the basis of the Yukawa meson theory. The values of the $np$ and $nn$ interaction characteristics calculated by the proposed model agree quite well with the experimental data.",1908.10124v1 2019-11-28,The dynamics of entropy uncertainty for qutrit system under the random telegraph noise,"We study the dynamics of quantum memory assist entropy uncertainty for qutrit system coupled to an environment modeled by random matrices. The results show that the effect of relative coupling strength on entropy uncertainty is opposite in Markov region and non-Markov region, and the influence of a common environment and independent environments in Markov region and non-Markov region is also opposite. One can reduce the entropy uncertainty by decreasing relative coupling strength or puting the system in two separate environments in the Markov case. In the non-Markov case, the entropy uncertainty can be reduced by increasing the relative coupling strength or by placing the system in a common environment.",1911.12681v1 2019-12-09,Double-$Q$ Chiral Stripe in the $d$-$p$ Model with Strong Spin-Charge Coupling,"We investigate the stability of multiple-$Q$ spiral states in $d$-$p$ electron systems with the strong spin-charge coupling. By using variational calculations on a square lattice, we find that the double-$Q$ state with the scalar chirality density wave, which has been studied in the weak spin-charge coupling regime, becomes the ground state even in the strong spin-charge coupling regime by considering the effect of the $d$-$p$ hybridization. We also show that the regions where the double-$Q$ state is stabilized are widely extended for introducing the antiferromagnetic superexchange interaction between nearest-neighbor localized spins.",1912.03906v1 2019-12-23,Higher-derivative couplings in string theory: five-point contact terms,"We compute the tree-level $H^2R^3$ couplings of type II strings and provide some basic tests of the couplings by considering both K3 and Calabi-Yau threefold compactifications. Curiously, additional kinematical structures show up at tree level that are not present in the one-loop couplings. This has interesting implications for type II supersymmetry as well as $SL(2, \mathbb Z)$ duality in type IIB strings.",1912.10974v3 2015-08-06,Entanglement Dynamics of Molecular Exciton States in Coupled Quantum Dots,"We theoretically model the electronic dynamics of a coupled quantum dot pair in a static electric field. We then investigate the possibility of polarization-entangled photon emission from the radiative cascade of the molecular biexciton state. Through numerical simulations, we analyze the dependence of entanglement fidelity on temperature and electric field, as well as tunnel coupling. We establish a regime of direct-indirect exciton detunings for which coupled quantum dots are superior to single dots for entangled photon generation, yielding near-unit fidelity over a larger range of exchange splittings.",1508.01298v2 2015-08-11,A critical look at methods for calculating charge transfer couplings fast and accurately,"We present here a short and subjective review of methods for calculating charge transfer couplings. Although we mostly focus on Density Functional Theory, we discuss a small subset of semiempirical methods as well as the adiabatic-to-diabatic transformation methods typically coupled with wavefunction-based electronic structure calculations. In this work, we will present the reader with a critical assessment of the regimes that can be modeled by the various methods their strengths and weaknesses. In order to give a feeling about the practical aspects of the calculations, we also provide the reader with a practical protocol for running coupling calculations with the recently developed FDE-ET method.",1508.02735v1 2015-08-18,Present status of coupled-channels calculations for heavy-ion subbarrier fusion reactions,"The coupled-channels method has been a standard tool in analyzing heavy-ion fusion reactions at energies around the Coulomb barrier. We investigate three simplifications usually adopted in the coupled-channels calculations. These are i) the exclusion of non-collective excitations, ii) the assumption of coordinate independent coupling strengths, and iii) the harmonic oscillator approximation for multi-phonon excitations. In connection to the last point, we propose a novel microscopic method based on the beyond-mean-field approach in order to take into account the anharmonic effects of collective vibrations.",1508.04222v1 2016-03-06,Increasing coupling of probabilistic cellular automata,"We give a necessary and sufficient condition for the existence of an increasing coupling of $N$ ($N \geq 2$) synchronous dynamics on $S^{\mathbb Z^d}$(PCA). Increasing means the coupling preserves stochastic ordering. We first present our main construction theorem in the case where $S$ is totally ordered, applications to attractive PCA's are given. When $S$ is only partially ordered, we show on two examples that a coupling of more than two synchronous dynamics may not exist. We also prove an extension of our main result for a particular class of partially ordered spaces.",1603.01885v1 2016-03-09,Coupling vs decoupling approaches for PDE/ODE systems modeling intercellular signaling,"We consider PDE/ODE systems for the simulation of intercellular signaling in multicellular environments. The intracellular processes for each cell described here by ODEs determine the long-time dynamics, but the PDE part dominates the solving effort. Thus, it is not clear if commonly used decoupling methods can outperform a coupling approach. Based on a sensitivity analysis, we present a systematic comparison between coupling and decoupling approaches for this class of problems and show numerical results. For biologically relevant configurations of the model, our quantitative study shows that a coupling approach performs much better than a decoupling one.",1603.02744v1 2016-03-22,Emergence of coupling-induced oscillations and broken symmetries in heterogeneously driven nonlinear reaction networks,"Many natural systems including the brain comprise coupled non-uniformly stimulated elements. In this paper we show that heterogeneously driven networks of excitatory-inhibitory units exhibit striking collective phenomena, including spontaneous oscillations upon coupling. On varying the coupling strength a novel transition is seen wherein the pattern symmetries of stimulated and unstimulated groups undergo mutual exchange. The system exhibits coexisting chaotic and non-chaotic attractors - an intriguing result in view of earlier reports of varying degrees of chaoticity in the brain.",1603.06734v1 2016-03-28,Dynamics of a population of oscillatory and excitable elements,"We analyze a variant of a model proposed by Kuramoto, Shinomoto, and Sakaguchi for a large population of coupled oscillatory and excitable elements. Using the Ott-Antonsen ansatz, we reduce the behavior of the population to a two-dimensional dynamical system with three parameters. We present the stability diagram and calculate several of its bifurcation curves analytically, for both excitatory and inhibitory coupling. Our main result is that when the coupling function is broad, the system can display bistability between steady states of constant high and low activity, whereas when the coupling function is narrow and inhibitory, one of the states in the bistable regime can show persistent pulsations in activity.",1603.08803v1 2016-10-20,Coupling in the Heisenberg group and its applications to gradient estimates,"We construct a non-Markovian coupling for hypoelliptic diffusions which are Brownian motions in the three-dimensional Heisenberg group. We then derive properties of this coupling such as estimates on the coupling rate, and upper and lower bounds on the total variation distance between the laws of the Brownian motions. Finally we use these properties to prove gradient estimates for harmonic functions for the hypoelliptic Laplacian which is the generator of Brownian motion in the Heisenberg group.",1610.06430v3 2016-10-25,Coherent Coupling of Remote Spin Ensembles via a Cavity Bus,"We report coherent coupling between two macroscopically separated nitrogen-vacancy electron spin ensembles in a cavity quantum electrodynamics system. The coherent interaction between the distant ensembles is directly detected in the cavity transmission spectrum by observing bright and dark collective multiensemble states and an increase of the coupling strength to the cavity mode. Additionally, in the dispersive limit we show transverse ensemble-ensemble coupling via virtual photons.",1610.07890v1 2016-12-07,Symmetry-Breaking Transition and Spectral Singularity in Coupled $\mathcal{PT}$-Symmetric Quantum Potentials,"We study the scattering properties of $N$ identical one-dimensional localized $\mathcal{PT}$-symmetric potentials, connected in series as well as in parallel. We derive a general transfer matrix formalism for parallel coupled quantum scatterers, and apply that theory to demonstrate that the spectral singularities and $\mathcal{PT}$-symmetric transitions of single scattering cells may be observed in coupled systems, at the same or distinct values of the critical parameters, depending on the connection modes under which the scattering objects are coupled. We analyse the influences of the connection configuration on the related transport properties such as spectral singularities and anisotropic transmission resonances.",1612.02469v1 2016-12-19,Generalising the coupling between spacetime and matter,"We explore the idea that the coupling between matter and spacetime is more complex than the one originally envisioned by Einstein. We propose that such coupling takes the form of a new fundamental tensor in the Einstein field equations. We then show that the introduction of this tensor can account for dark phenomenology in General Relativity, maintaining a weak field limit compatible with standard Newtonian gravitation. The same paradigm can be applied any other theory of gravitation. We show, as an example, that in the context of conformal gravity a generalised coupling is able to solve compatibility issues between the matter and the gravitational sector.",1612.06207v1 2016-12-20,$E_6$ Yukawa couplings in F-theory as D-brane instanton effects,"In a weak coupling limit the neighborhood of $E_6$ Yukawa points in $SU(5)$ GUT F-theory models is described by a non-resolvable orientifold of the conifold. We explicitly show, first directly in IIB and then via a mirror symmetry argument, that in this limit the $E_6$ Yukawa coupling is better described as coming from the non-perturbative contribution of a euclidean D1-brane wrapping the non-resolvable cycle. We also discuss how the M-theory description interpolates between the weak and strong coupling viewpoints.",1612.06874v1 2017-07-07,A QCD sum rules calculation of the $η_c D^* D$ and $η_c D_s^* D_s$ form factors and strong coupling constants,"We use the QCD sum rules for the three point correlation functions to compute the strong coupling constants of the meson vertices $\eta_c D^* D$ and $\eta_c D_s^* D_s$. We consider perturbative and non-perturbative contributions, working up to dimension five on the OPE. The vertices were studied considering that each one of its three mesons are off-shell alternately. The vertex coupling constant is evaluated through the extrapolation of the three different form factors. The results obtained for the coupling constants are $g_{\eta_c D^* D} = 5.23^{+1.80}_{-1.38}$ and $g_{\eta_c D_s^* D_s}=5.55^{+1.29}_{-1.55}$.",1707.02330v1 2017-07-21,Semiclassical gravity with a nonminimally coupled scalar field,"Semiclassical approximation to the Wheeler-DeWitt equation which corresponds to gravity with a minimally coupled scalar field has been performed. To the leading order, vacuum Einstein's equation along with the functional Schrodinger equation for the matter field, propagating in the background of classical curved space are obtained. The Schrodinger equation is solved for a quartic potential. It is observed that the wave-functional admits the wormhole boundary condition even for large negative values of the coupling constant epsilon. For conformal coupling epsilon = 1/6, the Hawking-Page wormhole solution is recovered.",1707.06930v1 2017-11-04,Intermittent behaviors in weakly coupled map lattices,"In this paper, we study intermittent behaviors of coupled piecewise-expanding map lattices with two nodes and a weak coupling. We show that the successive phase transition between ordered and disordered phases occurs for almost every orbit. That is, we prove $\liminf_{n\rightarrow \infty}| x_1(n)-x_2(n)|=0$ and $\limsup_{n\rightarrow \infty}| x_1(n)-x_2(n)|\ge c_0>0$, where $x_1(n), x_2(n)$ correspond to the coordinates of two nodes at the iterative step $n$. We also prove the same conclusion for weakly coupled tent-map lattices with any multi-nodes.",1711.01457v1 2017-11-14,Vortex dipole precession in a Fermi superfluid with Rashba spin-orbit coupling,"We present a closed-form expression for the time dynamics of a balanced Fermi superfluid with s-wave pairing and Rashba spin-orbit (SO) coupling. Solving the associated self-consistency conditions for an initial number density given by a Gaussian and an initial gap containing a vortex dipole, we show that Rashba SO coupling results in precession of the vortex dipole. The integrated self-consistent gap decays as a function of time, characterising a ""transient Fermi superfluid"". Our analytic solution forms a starting point for studies of vortex dynamics -- in particular braiding of Majorana fermions -- in Fermi superfluids in the presence of spin population imbalance and two-dimensional SO coupling, which are both required to realize a topological atomic Fermi gas in experiments.",1711.04970v1 2017-11-17,Reconstruction of a random phase dynamics network from observations,"We consider networks of coupled phase oscillators of different complexity: Kuramoto-Daido-type networks, generalized Winfree networks, and hypernetworks with triple interactions. For these setups an inverse problem of reconstruction of the network connections and of the coupling function from the observations of the phase dynamics is addressed. We show how a reconstruction based on the minimization of the squared error can be implemented in all these cases. Examples include random networks with full disorder both in the connections and in the coupling functions, as well as networks where the coupling functions are taken from experimental data of electrochemical oscillators. The method can be directly applied to asynchronous dynamics of units, while in the case of synchrony, additional phase resettings are necessary for reconstruction.",1711.06453v1 2017-11-27,Coupled Kähler-Ricci solitons on toric Fano manifolds,"We prove a necessary and sufficient condition in terms of the barycenters of a collection of polytopes for existence of coupled K\""ahler-Einstein metrics on toric Fano manifolds. This confirms the toric case of a coupled version of the Yau-Tian-Donaldson conjecture. We also obtain a necessary and sufficient condition for existence of torus-invariant solutions to a system of soliton type equations on toric Fano manifolds. Some of these solutions provide natural candidates for the large time limits of a certain geometric flow generalizing the K\""ahler-Ricci flow.",1711.09881v2 2017-11-28,Conformal inflation with chameleon coupling,"We investigate the possibility that the inflaton, in particular in conformal inflation models, is also a chameleon, i.e. that it couples to the energy density of some heavy non-relativistic matter present during inflation. We find new and interesting attractor behaviours, either prolonging inflation, or changing the observables $n_s,r$, depending on the sign of the chameleon coupling exponent. We also check that the chameleon coupling with the heavy matter field strongly suppress entropy modes during inflation.",1711.10408v3 2018-10-02,Controlling synchronization in coupled area-preserving maps using stickiness,"Unidirectionally coupled area-preserving maps with a mixed phase space may show identical synchronization in the sticky neighborhood of the regular islands. We use this fact to devise numerical procedures to control (delay and expedite) the process of synchronization in two standard maps coupled under the Pecora-Carroll coupling scheme. The delay method is based on controlled kicking of trajectories away from synchronization traps for as long as necessary. The method to expedite the process is achieved by a parameter perturbation technique which rapidly drives the chaotic trajectories to synchronization traps in the sticky neighborhoods of regular islands. We also discuss the limitations of these methods.",1810.01364v2 2018-10-29,Quark meson coupling model with $su(3)$ symmetry within the Bogoliubov independent quark model of the nucleon,"We generalize the Bogoliubov quark-meson coupling model to also include hyperons. The hyperon-$\sigma$-meson couplings are fixed by the model and the hyperon-$\omega$-meson couplings are fitted to the hypreon potentials in symmetric nuclear matter. The present model predicts neutron stars with masses above 2$M_\odot$ and the radius of a 1.4$M_\odot$ star equal to 13.83 km.",1810.12191v1 2019-05-10,Bound-State Band Reconstruction and Resonance in Spin-1/2 Bose Gas with 1D Spin-Orbit Coupling,"In this work, we study two-body bound states in two-component Bose gas with a one-dimensional (1D) spin-orbit coupling (SOC) induced by Raman lasers. The finite Raman coupling strength generates coupling among three spin channels, resulting in the reconstruction of three bound-state bands. In addition, multiple resonances can be induced at finite scattering lengths. By tuning the interaction in one intra-species channel, one bound-state band can be lifted and three resonances can be achieved at different center-of-mass momenta, which can be observable under current experimental conditions in ${}^{87}$Rb atoms.",1905.03979v1 2019-05-20,Stabilization of two strongly coupled hyperbolic equations in exterior domains,"In this paper we study the behavior of the total energy and the $L^2$-norm of solutions of two coupled hyperbolic equations by velocities in exterior domains. Only one of the two equations is directly damped by a localized damping term. We show that, when the damping set contains the coupling one and the coupling term is effective at infinity and on captive region, then the total energy decays uniformly and the $L^2$-norm of smooth solutions is bounded. In the case of two Klein-Gordon equations with equal speeds we deduce an exponential decay of the energy.",1905.08370v1 2019-05-31,Nonlinear phase coupling functions: a numerical study,"Phase reduction is a general tool widely used to describe forced and interacting self-sustained oscillators. Here we explore the phase coupling functions beyond the usual first-order approximation in the strength of the force. Taking the periodically forced Stuart-Landau oscillator as the paradigmatic model, we determine and numerically analyse the coupling functions up to the fourth order in the force strength. We show that the found nonlinear phase coupling functions can be used for predicting synchronization regions of the forced oscillator.",1905.13631v1 2020-09-12,"Search for the anomalous $WWγ$ couplings through the process $e^-e^+\,\rightarrow\,ν_e\barν_eγ$ at ILC with unpolarized and polarize beams","We investigate the anomalous $W^+W^-\gamma$ couplings through the process $e^-e^+\,\rightarrow\,\nu_e\bar{\nu}_e\gamma$ for unpolarized and polarized electron (positron) beams at the International Linear Collider. We give the 95$\%$ Confidence Level limits on the anomalous couplings with and without the systematic uncertainties for various values of center-of-mass energies and the integrated luminosities. We show that the obtained limits on the anomalous couplings through the process $e^-e^+\,\rightarrow\,\nu_e\bar{\nu}_e\gamma$ can highly improve the current experimental limits.",2009.05848v2 2021-02-16,Variational theory combining number-projected BCS and coupled-cluster doubles,"The ground state pairing correlations in finite fermionic systems are described with a high degree of accuracy within a variational approach based on a combined coupled-cluster and particle-number-projected BCS ansatz. The flexibility of this symmetry-preserving wavefunction enables a unified picture valid from weak to strong coupling, both in small and large systems. The present variational approach consistently yields an energy upper bound while operating at the same level of precision of the non-variational particle-number projected Bogoliubov-coupled-cluster theory [Phys. Rev. C 99, 044301 (2019)].",2102.08233v1 2013-06-03,The role of the Rashba coupling in spin current of monolayer gapped graphene,"In the current work we have investigated the influence of the Rashba spin-orbit coupling on spin-current of a single layer gapped graphene. It was shown that the Rashba coupling has a considerable role in generation of the spin-current of vertical spins in mono-layer graphene. The behavior of the spin-current is determined by density of impurities. It was also shown that the spin-current of the system could increase by increasing the Rashba coupling strength and band-gap of the graphene and the sign of the spin-current could be controlled by the direction of the current-driving electric field.",1306.0611v1 2015-07-03,Unitarity implications of diboson resonance in the TeV region for Higgs physics,"We investigate the implications of a putative new resonance in the TeV region coupled to the weak bosons. By studying perturbative unitarity in longitudinal WW scattering, we find that a weakly coupled spin-1 resonance, that explains the ATLAS diboson excesses, is allowed with a SM-like Higgs. On the other hand, larger values of the resonance couplings, preferred in models of strong dynamics, would imply either sizeable reduction of the Higgs couplings or new physics, beyond the diboson resonance, at a few TeV.",1507.00900v1 2015-07-16,Reduction of couplings in the MSSM,"We present an application of the reduction of couplings program in the minimal supersymmetric Standard Model (MSSM). We investigate if a functional relation between $\alpha_1$ and $\alpha_2$ gauge couplings can be realized which is Renormalization Group Invariant (RGI). Following the same procedure for the top and bottom Yukawa couplings we end up with a prediction of a narrow window for tan$\beta$, which is one of the basic parameters that determine the light Higgs mass.",1507.04469v1 2015-07-18,Couplings of Brownian Motions of deterministic distance in model spaces of constant curvature,"We consider the model space of constant curvature in dimension n and characterize all co-adapted couplings of Brownian motions on this space for which the distance between the processes is deterministic. In addition, the construction of the coupling is explicit for every choice of $\rho$ satisfying the above hypotheses.",1507.05202v2 2015-07-25,Holographic Superconductors with the General $RF^2$ type Couplings,"We explore the effects of the general non-minimally coupled $RF^2$-type couplings on the holographic s-wave superconductors numerically in the Schwarzschild-AdS background. We calculate the condensation and conductivity of the model for the coupling parameters $a_1$ and $\beta$. We obtain that the bigger deviations of the parameter $a_1$ from the minimal case lead to the larger deviations of the gap frequency from the universal value $\omega_g/T_c \approx 8$. Moreover the smaller $\beta $ and $a_1$ cause to gradually stronger and narrower coherence peak.",1507.07084v3 2015-07-28,Deviation of yukawa coupling and Higgs decay in gauge-Higgs Unification,"We study the deviation of yukawa coupling in the gauge-Higgs unification scenario from the Standard Model one. Applying the obtained results to the tau and bottom yukawa couplings, we numerically calculate the signal strength of $gg \to H \to \bar b b, \bar {\tau} \tau$in the gauge-Higgs unification.",1507.07630v1 2015-12-02,Modeling of processes with anomalous interactions by means of auxiliary fields,"The paper presents a method of modeling events with anomalous fermion-boson couplings by means of an auxiliary vector fields in addition to the SM gauge field. The method allows to simulate anomalous gauge couplings in different approaches, keeping only the linear order or higher order contributions of the anomalous couplings. The effectiveness of proposed method is demonstrated by modeling the single top quark production processes with anomalous Wtb couplings.",1512.00826v1 2016-09-13,Effects of Herzberg--Teller vibronic coupling on coherent excitation energy transfer,"In this work, we study the effects of non-Condon vibronic coupling on the quantum coherence of excitation energy transfer, via the exact dissipaton-equation-of-motion (DEOM) evaluations on excitonic model systems. Field-triggered excitation energy transfer dynamics and two dimensional coherent spectroscopy are simulated for both Condon and non-Condon vibronic couplings. Our results clearly demonstrate that the non-Condon vibronic coupling intensifies the dynamical electronic-vibrational energy transfer and enhances the total system-and-bath quantum coherence. Moreover, the hybrid bath dynamics for non-Condon effects enriches the theoretical calculation, and further sheds light on the interpretation of the experimental nonlinear spectroscopy.",1609.03685v1 2016-09-19,An entropic gradient structure for Lindblad equations and couplings of quantum systems to macroscopic models,"We show that all Lindblad operators (i.e. generators of quantum semigroups) on a finite-dimensional Hilbert space satisfying the detailed balance condition with respect to the thermal equilibrium state can be written as a gradient system with respect to the relative entropy. We discuss also thermodynamically consistent couplings to macroscopic systems, either as damped Hamiltonian systems with constant temperature or as GENERIC systems. In particular we discuss the coupling of a quantum dot coupled to macroscopic charge carriers.",1609.05765v3 2016-09-21,Mean-field beyond mean-field: the single particle view for moderately to strongly coupled charged fluids,"In a counter-ion only charged fluid, Coulomb coupling is quantified by a single dimensionless parameter. Yet, the theoretical treatment of moderately to strongly coupled charged fluids is a difficult task, central to the understanding of a wealth of soft matter problems, including biological systems. We show that the corresponding coupling regime can be remarkably well described by a single particle treatment, which, at variance with previous works, takes due account of inter-ionic interactions. To this end, the prototypical problem of a planar charged dielectric interface is worked out. Testing our predictions against Monte Carlo simulation data reveals an excellent agreement.",1609.06541v1 2016-09-28,Synchronization of coupled noisy oscillators: Coarse-graining from continuous to discrete phases,"The theoretical description of synchronization phenomena often relies on coupled units of continuous time noisy Markov chains with a small number of states in each unit. It is frequently assumed, either explicitly or implicitly, that coupled discrete-state noisy Markov units can be used to model mathematically more complex coupled noisy continuous phase oscillators. In this work we explore conditions that justify this assumption by coarse-graining continuous phase units. In particular, we determine the minimum number of states necessary to justify this correspondence for Kuramoto-like oscillators.",1609.08731v1 2016-11-18,Temperature dependent quantum correlations in three dipolar coupled two-level atoms,"We investigate the thermal entanglement characteristics of three dipole-coupled two-level atoms arranged in two different configurations - in a line with nearest neighbour coupling and in a closed loop with each atom interacting with both its neighbours. It is observed that in loop configuration, any one of the three atoms is indeed entangled with the other two atoms in the system, which are not mutually entangled, and further that this feature is specific to only the loop configuration, which is markedly absent in the line configuration. A detailed study of the quantum correlations demonstrated how these can be tuned by varying the temperature and the dipole dipole coupling strength, in both the configurations.",1611.07063v1 2016-11-24,On the synchronization of coupled forced negative conductance circuits: A numerical study,"In this paper, a numerical study on the complete synchronization phenomenon exhibited by coupled forced negative conductance circuits is presented. The nonlinear system exhibiting two types of chaotic attractors is studied for complete synchronization of the identical chaotic attractors through phase portraits under one type of coupling. The stability of the synchronized states is observed for different coupling schemes of the circuit variables through {\emph{Master Stability Function}}. The Conditional lyapunov exponents explaining the dynamical behaviour of the driven system is presented.",1611.08170v1 2017-04-21,Vortex-hole duality: a unified picture of weak and strong-coupling regimes of bosonic ladders with flux,"Two-leg bosonic ladders with flux harbor a remarkable vortex-hole duality between the weak-coupling vortex lattice superfluids and strong-coupling charge-density-wave crystals. The strong-coupling crystalline states, which are realized in the vicinity of $\pi$-flux, are independent of particle statistics, and are related with the incompressible fractional quantum Hall states in the thin-cylinder limit. These fully gapped ground states, away of $\pi$-flux, develop nonzero chiral (spin) currents. Contact-interacting quantum gases permit exploration of this vortex-hole duality in experiments.",1704.06517v1 2018-01-01,Kinetic layers and coupling conditions for nonlinear scalar equations on networks,"We consider a kinetic relaxation model and an associated macroscopic scalar nonlinear hyperbolic equation on a network. Coupling conditions for the macroscopic equations are derived from the kinetic coupling conditions via an asymptotic analysis near the nodes of the network. This analysis leads to the combination of kinetic half-space problems with Riemann problems at the junction. Detailed numerical comparisons between the different models show the agreement of the coupling conditions for the case of tripod networks.",1801.00457v1 2018-08-01,Long range dynamical coupling between magnetic adatoms mediated by a 2D topological insulator,"We study the spin excitation spectra and the dynamical exchange coupling between iron adatoms on a Bi bilayer nanoribbon. We show that the topological character of the edge states is preserved in the presence of the magnetic adatoms. Nevertheless, they couple significantly to the edge spin currents, as witnessed by the large and long-ranged dynamical coupling we obtain in our calcula- tions. The large effective magnetocrystalline anisotropy of the magnetic adatoms combined with the transport properties of the topologically protected edge states make this system a strong candidate for implementation of spintronics devices and quantum information and/or computation protocols.",1808.00347v1 2018-08-23,Organic polariton lasing and the weak- to strong-coupling crossover,"Following experimental realizations of room temperature polariton lasing with organic molecules, we present a microscopic model that allows us to explore the crossover from weak to strong matter-light coupling. We consider a non-equilibrium Dicke-Holstein model, including both strong coupling to vibrational modes and strong matter-light coupling, providing the phase diagram of this model in the thermodynamic limit. We discuss the mechanism of polariton lasing, uncovering a process of self-tuning, and identify the relation and distinction between regular dye lasers and organic polariton lasers.",1808.07683v1 2018-08-28,Nonlinear Dynamics of Coupled Axion-Josephson Junction Systems,"We study the classical dynamics of an axion field (the signal) that is coupling into a Josephson junction (the detector) by means of a capacitive coupling of arbitrary size. Depending on the size of the coupling constant and the initial conditions, we find a rich phase space structure of this nonlinear problem. We present general analytic solutions of the equations of motion in the limit of small amplitudes of the angle variables, and discuss both the case of no dissipation and the case of dissipation in the system. The effect of a magnetic field is investigated as well, leading to topological phase transitions in the phase space structure.",1808.09417v1 2019-06-06,Observation of incoherently coupled dark-bright vector solitons in single-mode fibers,"We report experimental observation of incoherently coupled dark-bright vector solitons in single-mode fibers. Properties of the vector solitons agree well with those predicted by the respective systems of incoherently coupled nonlinear Schroedinger equations. To the best of our knowledge, this is the first experimental observation of temporal incoherently coupled dark-bright solitons in single-mode fibers.",1906.02504v1 2019-06-20,Synchronization of linear oscillators coupled through dynamic networks with interior nodes,"Synchronization is studied in an array of identical linear oscillators of arbitrary order, coupled through a dynamic network comprising dissipative connectors (e.g., dampers) and restorative connectors (e.g., springs). The coupling network is allowed to contain interior nodes, i.e., those that are not directly connected to an oscillator. It is shown that the oscillators asymptotically synchronize if and only if the Schur complement (with respect to the boundary nodes) of the complex-valued Laplacian matrix representing the coupling has a single eigenvalue on the imaginary axis.",1906.08572v1 2019-07-18,GBDT and explicit solutions for the matrix coupled dispersionless equations (local and nonlocal cases),"We introduce matrix coupled (local and nonlocal) dispersionless equations, construct wide classes of explicit multipole solutions, give explicit expressions for the corresponding Darboux and wave matrix valued functions and consider their asymptotics in some interesting cases. We consider the scalar cases of coupled, complex coupled and nonlocal dispersionless equations as well.",1907.08258v1 2019-07-26,Time-dependent coupled cluster theory on the Keldysh contour for non-equilibrium systems,"We leverage the Keldysh formalism to extend our implementation of finite temperature coupled cluster theory [\textit{J. Chem. Theory Comput.} 2018, \textit{14}, 5690-5700] to thermal systems that have been driven out of equilibrium. The resulting Keldysh coupled cluster theory is discussed in detail. We describe the implementation of the equations necessary to perform Keldysh coupled cluster singles and doubles calculations of finite temperature dynamics, and we apply the method to some simple systems including a Hubbard model with a Peierls phase and an {\it ab initio} model of warm-dense silicon subject to an ultrafact XUV pulse.",1907.11695v1 2019-10-02,Strong Coupling Thermodynamics of Open Quantum Systems,"A general thermodynamic framework is presented for open quantum systems in fixed contact with a thermal reservoir. The first and second law are obtained for arbitrary system-reservoir coupling strengths, and including both factorized and correlated initial conditions. The thermodynamic properties are adapted to the generally strong coupling regime, approaching the ones defined for equilibrium, and their standard weak-coupling counterparts as appropriate limits. Moreover, they can be inferred from measurements involving only system observables. Finally, a thermodynamic signature of non-Markovianity is formulated in the form of a negative entropy production rate.",1910.01246v2 2019-10-10,Improved phase locking of laser arrays with nonlinear coupling,"An arrangement based on a degenerate cavity laser for forming an array of non-linearly coupled lasers with an intra-cavity saturable absorber is presented. More than $30$ lasers were spatially phase locked and temporally Q-switched. The arrangement with nonlinear coupling was found to be $25$ times more sensitive to loss differences and converged $5$ times faster to the lowest loss phase locked state than with linear coupling, thus providing a unique solution to problems that have several near-degenerate solutions.",1910.04430v1 2019-10-24,"Formulation, analysis and computation of an optimization-based local-to-nonlocal coupling method","We present an optimization-based coupling method for local and nonlocal continuum models. Our approach couches the coupling of the models into a control problem where the states are the solutions of the nonlocal and local equations, the objective is to minimize their mismatch on the overlap of the local and nonlocal problem domains, and the virtual controls are the nonlocal volume constraint and the local boundary condition. We present the method in the context of Local-to-Nonlocal diffusion coupling. Numerical examples illustrate the theoretical properties of the approach.",1910.11214v2 2019-10-30,Scalarization of compact stars in the scalar-Gauss-Bonnet gravity,"We study scalarization of horizonless neutral compact reflecting stars. In our model, the scalar hair can be induced by the coupling of static scalar fields to the Gauss-Bonnet invariant. We analytically obtain lower bounds on the coupling parameter. Below the bound, the static scalar hair cannot form. And above the bound, we numerically get the discrete coupling parameter that can support scalar hairs outside stars. We also disclose effects of model parameters on the discrete coupling parameter.",1910.13718v3 2020-01-27,Bidirectional switching assisted by interlayer exchange coupling in asymmetric magnetic tunnel junctions,"We study the combined effects of spin transfer torque, voltage modulation of interlayer exchange coupling and magnetic anisotropy on the switching behavior of perpendicular magnetic tunnel junctions (p-MTJs). In asymmetric p-MTJs, a linear-in-voltage dependence of interlayer exchange coupling enables the effective perpendicular anisotropy barrier to be lowered for both voltage polarities. This mechanism is shown to reduce the critical switching current and effective activation energy. Finally, we analyze the possibility of having switching via interlayer exchange coupling only.",2001.10024v1 2020-03-30,Coupling colloidal quantum dots to gap waveguides,"The coupling between single photon emitters and integrated photonic circuits is an emerging topic relevant for quantum information science and other nanophotonic applications. We investigate the coupling between a hybrid system of colloidal quantum dots and propagating gap modes of a silicon nitride waveguide system. We furthermore explore the density of optical states of the system by using a scanning probe technique and find that the quantum dots couple significantly to the photonic circuit. Our results indicate that a scalable slot-waveguide might serve as a promising platform in future developments of integrated quantum circuitry.",2003.13823v1 2020-03-30,A kinetic traffic network model and its macroscopic limit: diverging lanes,"In this paper we propose coupling conditions for a kinetic two velocity model for vehicular traffic for junctions with diverging lanes. We consider cases with and without directional preferences and present corresponding kinetic coupling conditions. From this kinetic network model coupling conditions for a macroscopic traffic model are derived. We use an analysis of the layer equations at the junction in combination with a suitable matching procedure with half-Riemann problems for the macroscopic model. In this way classical coupling conditions for scalar conservation laws for traffic flow on networks are derived from an underlying network problem.",2003.14254v1 2020-03-31,Spurious Resonances in Coupled Domain-Boundary Variational Formulations of Transmission Problems in Electromagnetism and Acoustics,"We develop a framework shedding light on common features of coupled variational formulations arising in electromagnetic scattering and acoustics. We show that spurious resonances haunting coupled domain-boundary formulations based on direct boundary integral equations of the first kind originate from the formal structure of their Calderon identities. Using this observation, the kernel of the coupled problem is characterized explicitly and we show that it completely vanishes under the exterior representation formula.",2003.14357v3 2020-04-07,FEM-BEM mortar coupling for the Helmholtz problem in three dimensions,"We present a FEM-BEM coupling strategy for time-harmonic acoustic scattering in media with variable sound speed. The coupling is realized with the aid of a mortar variable that is an impedance trace on the coupling boundary. The resulting sesquilinear form is shown to satisfy a Garding inequality. Quasi-optimal convergence is shown for sufficiently fine meshes. Numerical examples confirm the theoretical convergence results.",2004.03523v1 2020-04-10,Green's functions perspective on nonequilibrium thermodynamics of open quantum systems strongly coupled to baths,"We give nonequilibrium Green's function (NEGF) perspective on thermodynamics formulations for open quantum systems strongly coupled to baths. Scattering approach implying thermodynamic consideration of a super-system (system plus baths) weakly coupled to external super-baths is compared with consideration of thermodynamics of a system strongly coupled to its baths. We analyze both approaches from the NEGF perspective and argue that the latter yields a possibility of thermodynamic formulation consistent with dynamical (quantum transport) description.",2004.05175v1 2020-07-15,"Harmonic synchronization under all three types of coupling: position, velocity, and acceleration","Synchronization of identical harmonic oscillators interconnected via position, velocity, and acceleration couplings is studied. How to construct a complex Laplacian matrix representing the overall coupling is presented. It is shown that the oscillators asymptotically synchronize if and only if this matrix has a single eigenvalue on the imaginary axis. This result generalizes some of the known spectral tests for synchronization. Some simpler Laplacian constructions are also proved to work provided that certain structural conditions are satisfied by the coupling graphs.",2007.07546v1 2020-07-15,Type-II fractons from coupled spin chains and layers,"We describe a construction of topological orders from coupled lower dimensional symmetry-protected topological orders, which is closely related to gauging a subsystem symmetry. Our construction yields both conventional topological orders and exotic fracton topological orders of type-I and type-II. In particular, we find a coupled spin chain construction of Haah's cubic code, and a coupled layer construction of Yoshida's fractal spin liquids.",2007.07894v2 2020-08-17,Coupling Functions in Neuroscience,"The interactions play one of the central roles in the brain mediating various processes and functions. They are particularly important for the brain as a complex system that has many different functions from the same structural connectivity. When studying such neural interactions the coupling functions are very suitable, as inherently they can reveal the underlaying functional mechanism. This chapter overviews some recent and widely used aspects of coupling functions for studying neural interactions. Coupling functions are discussed in connection to two different levels of brain interactions - that of neuron interactions and brainwave cross-frequency interactions. Aspects relevant to this from both, theory and methods, are presented. Although the discussion is based on neuroscience, there are strong implications from, and to, other fields as well.",2008.07612v1 2020-10-09,Transition time estimation for $δ$-function coupling in two state problem: An analytically solvable model,"We propose a simple method to calculate transition time in a two-state scattering problem, where two constant potentials are coupled by a delta function potential $V_{12}=V_{21}=k_0 \delta(x)$. The exact analytical expression for the time of transition $\tau$ is derived. We notice $\tau$ explicitly depends on the second state's potential energy along with the incident energy and coupling strength. We also observe from the derived expression of $\tau$ that depending on the initial energy, the coupling potential could behave like a transparent or opaque medium to the incident wave in a single state equivalent description.",2010.04497v1 2020-11-06,Wilson loops in circular quiver SCFTs at strong coupling,"We study circular BPS Wilson loops in the $\mathcal{N}=2$ superconformal $n$-node quiver theories at large $N$ and strong 't Hooft coupling by using localization. We compute the expectation values of Wilson loops in the limit when the 't Hooft couplings are hierarchically different and when they are nearly equal. Based on these results, we make a conjecture for arbitrary strong couplings.",2011.03531v3 2020-11-12,Path regularity of coupled McKean-Vlasov FBSDEs,"This paper establishes H\""{o}lder time regularity of solutions to coupled McKean-Vlasov forward-backward stochastic differential equations (MV-FBSDEs). This is not only of fundamental mathematical interest, but also essential for their numerical approximations. We show that a solution triple to a MV-FBSDE with Lipschitz coefficients is 1/2-H\""{o}lder continuous in time in the $L^p$-norm provided that it admits a Lipschitz decoupling field. Special examples include decoupled MV-FBSDEs, coupled MV-FBSDEs with a small time horizon and coupled stochastic Pontryagin systems arsing from mean field control problems.",2011.06664v1 2020-11-23,Synchronization of oscillators with hyperbolic chaotic phases,"Synchronization in a population of oscillators with hyperbolic chaotic phases is studied for two models. One is based on the Kuramoto dynamics of the phase oscillators and on the Bernoulli map applied to these phases. This system possesses an Ott-Antonsen invariant manifold, allowing for a derivation of a map for the evolution of the complex order parameter. Beyond a critical coupling strength, this model demonstrates bistability synchrony-disorder. Another model is based on the coupled autonomous oscillators with hyperbolic chaotic strange attractors of Smale-Williams type. Here a disordered asynchronous state at small coupling strengths, and a completely synchronous state at large couplings are observed. Intermediate regimes are characterized by different levels of complexity of the global order parameter dynamics.",2011.11310v1 2020-11-25,Cavity-modulated ionization potentials and electron affinities from quantum electrodynamics coupled-cluster theory,"Quantum electrodynamics coupled-cluster (QED-CC) theory is used to model vacuum-field-induced changes to ground-state properties of a series of sodium halide compounds (NaX, X = F, Cl, Br, I) strongly coupled to an optical cavity. Ionization potentials (IPs) and electron affinities (EAs) are presented, and it is demonstrated that EAs are easily modulated by cavity interactions, while IPs for these compounds are far less sensitive to the presence of the cavity. EAs predicted by QED-CC can be reduced by as much 0.22 eV (or ~50%) when considering experimentally-accessible coupling parameters.",2011.12768v2 2021-01-21,Polarons in a ferromagnetic spinor Bose-Einstein condensates,"We investigate the polarons formed by immersing a spinor impurity in a ferromagnetic state of $F=1$ spinor Bose-Einstein condensate. The ground state energies and effective masses of the polarons are calculated in both weak-coupling regime and strong-coupling regime. In the weakly interacting regime the second order perturbation theory is performed. In the strong coupling regime we use a simple variational treatment. The analytical approximations to the energy and effective mass of the polarons are constructed. Especially, a transition from the mobile state to the self-trapping state of the polaron in the strong coupling regime is discussed. We also estimate the signatures of polaron effects in spinor BEC for the future experiments.",2101.08474v1 2021-03-02,Nonadiabatic effects in attosecond transient absorption spectroscopy,"We study effects of nonadiabatic couplings in a model of a diatomic molecule in the context of attosecond transient absorption spectroscopy. By using a model system consisting of four diabatic electronic states and with a variable strength of the diabatic coupling, we can explore attosecond transient absorption spectra in different regimes of the vibronic couplings between the electronic and nuclear dynamics, and determine when nonadiabatic couplings can be ignored or when they have a substantial effect. The findings are rationalized in terms of a multilevel model, which captures aspects of both electronic and nuclear degrees of freedom.",2103.01582v1 2021-03-31,Wormholes without averaging,"After averaging over fermion couplings, SYK has a collective field description that sometimes has ""wormhole"" solutions. We study the fate of these wormholes when the couplings are fixed. Working mainly in a simple model, we find that the wormhole saddles persist, but that new saddles also appear elsewhere in the integration space -- ""half-wormholes."" The wormhole contributions depend only weakly on the specific choice of couplings, while the half-wormhole contributions are strongly sensitive. The half-wormholes are crucial for factorization of decoupled systems with fixed couplings, but they vanish after averaging, leaving the non-factorizing wormhole behind.",2103.16754v1 2021-04-02,Plasmon modes of coupled quantum Hall edge channels in the presence of disorder-induced tunneling,"Coupled quantum Hall edge channels show intriguing non-trivial modes, for example, charge and neutral modes at Landau level filling factors 2 and 2/3. We propose an appropriate and effective model with Coulomb interaction and disorder-induced tunneling characterized by coupling capacitances and tunneling conductances, respectively. This model explains how the transport eigenmodes, within the interaction- and disorder-dominated regimes, change with the coupling capacitance, tunneling conductance, and measurement frequency. We propose frequency- and time-domain transport experiments, from which eigenmodes can be determined using this model.",2104.00839v2 2021-04-15,Multi-objective Herglotz' variational principle and cooperative Hamilton-Jacobi systems,"We study a multi-objective variational problem of Herglotz' type with cooperative linear coupling. We established the associated Euler-Lagrange equations and the characteristic system for cooperative weakly coupled systems of Hamilton-Jacobi equations. We also established the relation of the value functions of this variational problem with the viscosity solutions of cooperative weakly coupled systems of Hamilton-Jacobi equations. Comparing to the previous work in stochastic frame, this approach affords a pure deterministic explanation of this problem under more general conditions. We also showed this approach is valid for general linearly coupling matrix for short time.",2104.07546v1 2021-04-18,Boundary controllability of two coupled wave equations with space-time first-order coupling in 1-D,"This paper is devoted to study exact controllability of two one-dimensional coupled wave equations with first-order coupling terms with coefficients depending on space and time. We give a necessary and sufficient condition for both exact controllability in high frequency in the general case and the unique continuation in the cascade case.",2104.08960v2 2021-05-07,Optomechanical amplification driven by interference of phonon-exciton and phonon-photon couplings,"We study theoretically optomechanical damping and amplification spectra for vibrations interacting with excitonic polaritons in a zero-dimensional microcavity. We demonstrate, that the spectra strongly depend on the ratio of the exciton-phonon and the photon-phonon coupling constants. The interference between these couplings enables a situation when optomechanical gain exists either only for a lower polaritonic resonance or only for an upper polaritonic resonance. Our results provide insight in the optomechanical interactions in various multi-mode systems, where several resonant oscillators, such as photons, plasmons, or excitons are coupled to the same vibration mode.",2105.03214v1 2021-05-11,Note: Vibronic coupling in light-harvesting complex II revisited,"We discuss our recent theoretical work on vibronic coupling mechanisms in a model energy transfer system in the context of previous 2DEV experiments on a natural light-harvesting system, light-harvesting complex II (LHCII), where vibronic signatures were suggested to be involved in energy transfer. In this comparison, we directly assign the vibronic coupling mechanism in LHCII as arising from Herzberg-Teller activity and show how this coupling modulates the energy transfer dynamics in this photosynthetic system.",2105.04725v1 2021-05-11,Symmetry-protected non-Abelian geometric phases in optical waveguides with nonorthogonal modes,"The generation of non-Abelian geometric phases from a system of evanescently coupled waveguides is extended towards the framework of nonorthogonal coupled-mode theory. Here, we study an experimentally feasible tripod arrangement of waveguides that contain dark states from which a nontrivial U(2)-mixing can be obtained by means of an adiabatic parameter variation. We investigate the influence of higher-order contributions beyond nearest-neighbour coupling as well as self-coupling on the stability of a U(3)-phase generated from an optical tetrapod setup. Our results indicate that, despite the mode nonorthogonality, the symmetry of dark states protects the geometric evolution of light from distortion.",2105.04859v1 2021-05-31,Insights into the performance of loosely-coupled FSI schemes based on Robin boundary conditions,"Robin boundary conditions are a natural consequence of employing Nitsche's method for imposing the kinematic velocity constraint at the fluid-solid interface. Loosely-coupled FSI schemes based on Dirichlet-Robin or Robin-Robin coupling have been demonstrated to improve the stability of such schemes with respect to added-mass. This paper aims to offer some numerical insights into the performance characteristics of such loosely-coupled FSI schemes based on Robin boundary conditions. Using numerical examples, we demonstrate that the improved stability due to the added damping term is actually at the expense of important dynamic characteristics of the structural sub-problem.",2105.14831v1 2021-06-03,Hybrid coupling of finite element and boundary element methods using Nitsche's method and the Calderon projection,"In this paper we discuss a hybridised method for FEM-BEM coupling. The coupling from both sides use a Nitsche type approach to couple to the trace variable. This leads to a formulation that is robust and flexible with respect to approximation spaces and can easily be combined as a building block with other hybridised methods. Energy error norm estimates and the convergence of Jacobi iterations are proved and the performance of the method is illustrated on some computational examples.",2106.01720v2 2021-06-06,"Arazy-Cwikel and Calderón-Mityagin type properties of the couples $(\ell^{p},\ell^{q})$, $0 \le p1$ TeV. The Wtb couplings in vector-like quark models and the Littlest Higgs models are sensitive to the mixing angles of new heavy particles and SM particles. We also include the constraints of the oblique T-parameter and Zbb couplings which impose much tighter constraints on the mixing angles. We show that the Wtb coupling constraints become relevant if the precision of single top production cross section measurements could be reduced to 1\% relative to the SM predictions in future.",1504.03785v2 2014-05-26,Top Yukawa coupling measurement with indefinite CP Higgs in $e^+e^-\to t\bar{t}Φ$,"We consider the issue of the top quark Yukawa coupling measurement in a model in dependent and general case with the inclusion of CP-violation in the coupling. Arguably the best process to study this coupling is the associa ted production of Higgs boson along with a $t\bar t$ pair in a machine like the International Linear Collider (ILC). While detailed analyses of the sensitivity of the measurement assuming a Standard Model (SM) - like coupling are available in the context of ILC, conclude that th e coupling could be pinned down at about 10\% level with modest luminosity, our investigations show that the scenario could be different in case of a more general coupling. The modified Lorentz structure resulting in a changed functional dependence of the cross section on the couplin g, along with the difference in the cross section itself leads to considerable deviation in the sensitivity. Our studies with an ILC of center of mass energies of 500 GeV, 800 GeV and 1000 GeV show that moderate CP-mixing in the Higgs sector could change the sensitivity to about 20\ %, while it could be worsened to 75\% in cases which could accommodate more dramatic changes in the coupling. While detailed considerations of the decay distributions point to a need for a relook at the analysis strategy followed for the case of SM such as for a model independent analysis of the top quark Yukawa coupling measurement. This study strongly suggests that, a joint analysis of the CP properties and the Yukawa coupling measurement would be the way forward at the ILC and that caution must be excercised in the measurem ent of the Yukawa couplings and the conclusions drawn from it.",1405.6465v1 2018-09-28,Engineering long spin coherence times of spin-orbit systems,"Spin-orbit coupling fundamentally alters spin qubits, opening pathways to improve the scalability of quantum computers via long distance coupling mediated by electric fields, photons, or phonons. It also allows for new engineered hybrid and topological quantum systems. However, spin qubits with intrinsic spin-orbit coupling are not yet viable for quantum technologies due to their short ($\sim1~\mu$s) coherence times $T_2$, while qubits with long $T_2$ have weak spin-orbit coupling making qubit coupling short-ranged and challenging for scale-up. Here we show that an intrinsic spin-orbit coupled ""generalised spin"" with total angular momentum $J=\tfrac{3}{2}$, which is defined by holes bound to boron dopant atoms in strained $^{28}\mathrm{Si}$, has $T_2$ rivalling the electron spins of donors and quantum dots in $^{28}\mathrm{Si}$. Using pulsed electron paramagnetic resonance, we obtain $0.9~\mathrm{ms}$ Hahn-echo and $9~\mathrm{ms}$ dynamical decoupling $T_2$ times, where strain plays a key role to reduce spin-lattice relaxation and the longitudinal electric coupling responsible for decoherence induced by electric field noise. Our analysis shows that transverse electric dipole can be exploited for electric manipulation and qubit coupling while maintaining a weak longitudinal coupling, a feature of $J=\tfrac{3}{2}$ atomic systems with a strain engineered quadrupole degree of freedom. These results establish single-atom hole spins in silicon with quantised total angular momentum, not spin, as a highly coherent platform with tuneable intrinsic spin-orbit coupling advantageous to build artificial quantum systems and couple qubits over long distances.",1809.10859v2 2018-10-23,The Key Player Problem in Complex Oscillator Networks and Electric Power Grids: Resistance Centralities Identify Local Vulnerabilities,"Identifying key players in a set of coupled individual systems is a fundamental problem in network theory. Its origin can be traced back to social sciences and led to ranking algorithms based on graph theoretic centralities. Coupled dynamical systems differ from social networks in that, they are characterized by degrees of freedom with a deterministic dynamics and the coupling between individual units is a well-defined function of those degrees of freedom. One therefore expects the resulting coupled dynamics, and not only the network topology, to also determine the key players. Here, we investigate synchronizable network-coupled dynamical systems such as high voltage electric power grids and coupled oscillators. We search for nodes which, once perturbed by a local noisy disturbance, generate the largest overall transient excursion away from synchrony. A spectral decomposition of the coupling matrix leads to an elegant, concise, yet accurate solution to this identification problem. We show that, when the internodal coupling matrix is Laplacian, these key players are peripheral in the sense of a centrality measure defined from effective resistance distances. For linearly coupled dynamical systems such as weakly loaded power grids or consensus algorithms, the nodal ranking is efficiently obtained through a single Laplacian matrix inversion, regardless of the operational synchronous state. We call the resulting ranking index LRank. For heavily loaded power grids or coupled oscillators systems closer to the transition to synchrony, nonlinearities render the nodal ranking dependent on the synchronous state. In this case a weighted Laplacian matrix inversion gives another ranking index, which we call WLRank. Quite surprisingly, we find that LRank provides a faithful ranking even for well developed coupling nonlinearities, corresponding to oscillator angle differences up to $40^o$ approximately.",1810.09694v1 2022-09-15,Spin-orbital-angular-momentum-coupled quantum gases,"We briefly review the recent progress of theories and experiments on spin-orbital-angular-momentum (SOAM)-coupled quantum gases. The coupling between the intrinsic degree of freedom of particles and their external orbital motions widely exists in universe, and leads to a broad variety of fundamental phenomena both in the classical physics and quantum mechanics. Recent realization of synthetic SOAM coupling in cold atoms has attracted a great deal of attention, and stimulates a large amount of considerations on exotic quantum phases in both Bose and Fermi gases. In this review, we present a basic idea of engineering SOAM coupling in neutral atoms, starting from a semiclassical description of atom-light interaction. Unique features of the single-particle physics in the presence of SOAM coupling are discussed. The intriguing ground-state quantum phases of weakly interacting Bose gases are introduced, with emphasis on a so-called angular stripe phase, which has yet been observed at present. It is demonstrated how to generate a stable giant vortex in a SOAM-coupled Fermi superfluid. We also discuss topological characters of a Fermi superfluid in the presence of SOAM coupling. We then introduce the experimental achievement of SOAM coupling in $^{87}$Rb Bose gases and its first observation of phase transitions. The most recent development of SOAM-coupled Bose gases in experiments is also summarized. Regarding the controllability of ultracold quantum gases, it opens a new era, on the quantum simulation point of view, to study the fundamental physics resulted from SOAM coupling as well as newly emergent quantum phases.",2209.07051v2 2023-02-23,Minimum-Entropy Coupling Approximation Guarantees Beyond the Majorization Barrier,"Given a set of discrete probability distributions, the minimum entropy coupling is the minimum entropy joint distribution that has the input distributions as its marginals. This has immediate relevance to tasks such as entropic causal inference for causal graph discovery and bounding mutual information between variables that we observe separately. Since finding the minimum entropy coupling is NP-Hard, various works have studied approximation algorithms. The work of [Compton, ISIT 2022] shows that the greedy coupling algorithm of [Kocaoglu et al., AAAI 2017] is always within $log_2(e) \approx 1.44$ bits of the optimal coupling. Moreover, they show that it is impossible to obtain a better approximation guarantee using the majorization lower-bound that all prior works have used: thus establishing a majorization barrier. In this work, we break the majorization barrier by designing a stronger lower-bound that we call the profile method. Using this profile method, we are able to show that the greedy algorithm is always within $log_2(e)/e \approx 0.53$ bits of optimal for coupling two distributions (previous best-known bound is within 1 bit), and within $(1 + log_2(e))/2 \approx 1.22$ bits for coupling any number of distributions (previous best-known bound is within 1.44 bits). We also examine a generalization of the minimum entropy coupling problem: Concave Minimum-Cost Couplings. We are able to obtain similar guarantees for this generalization in terms of the concave cost function. Additionally, we make progress on the open problem of [Kova\v{c}evi\'c et al., Inf. Comput. 2015] regarding NP membership of the minimum entropy coupling problem by showing that any hardness of minimum entropy coupling beyond NP comes from the difficulty of computing arithmetic in the complexity class NP. Finally, we present exponential-time algorithms for computing the exactly optimal solution.",2302.11838v1 2023-02-06,On the use of Lagrange Multiplier State-Space Substructuring in dynamic substructuring analysis,"In this article, the formulation of Lagrange Multiplier State-Space Substructuring (LM-SSS) is presented and extended to directly compute coupled displacement and velocity state-space models. The LM-SSS method is applied to couple and decouple state-space models established in the modal domain. Moreover, it is used together with tailored postprocessing procedures to eliminate the redundant states originated from the coupling and decoupling operations. This specific formulation of the LM-SSS approach made it possible to develop a tailored coupling form, named Unconstrained Coupling Form (UCF). UCF just requires the computation of a nullspace and does not rely on the selection of a subspace from a nullspace. By exploiting a numerical example, LM-SSS was compared with the Lagrange Multiplier Frequency Based Substructuring (LMFBS) approach, which is currently widely recognized as a reference approach. This was done both in terms of: a)coupled FRFs derived by coupling the state-space models of two substructures and b) decoupled FRFs derived by decoupling the state-space model of a component from the coupled model. LM-SSS showed to be suitable to compute minimal order coupled models and UCF turned out to have similar performance as other coupling forms already presented to the scientific community. As for the decoupling task, the FRFs derived from the LM-SSS approach perfectly matched those obtained by LM-FBS. Moreover, it was also demonstrated that the elimination of the redundant states originated from the decoupling operation was correctly performed. The approaches discussed were exploited on an experimental substructuring application. LM-SSS resulted to be a reliable SSS technique to perform coupling and decoupling operations with state-space models estimated from measured FRFs as well as to provide accurate minimal-order models.",2303.15297v1 2023-05-03,Nontrivial Quantum Geometry and the Strength of Electron-Phonon Coupling,"The coupling of electrons to phonons (electron-phonon coupling) is crucial for the existence of various phases of matter, in particular superconductivity and density waves. While the consequences of nontrivial quantum geometry/topology are well-established in electronic bands, countless studies of the bulk electron-phonon coupling strength performed in the pre-topological era missed a crucial aspect of multi-band electron systems coupled to phonons: the effect of electron band geometry and/or topology on the electron-phonon coupling. We devise a theory that incorporates the quantum geometry of the electron bands into the electron-phonon coupling. We find that the Fubini-Study quantum metric contributes indispensably to the dimensionless electron-phonon coupling constant, and we generalize the fundamental concept of quantum geometry to take into account orbital selective quantities, which also can play a dominant role in the electron-phonon coupling. More specifically, we show, in a simple analytic model, why the electron quantum geometry is essential to a deep understanding of the bulk electron-phonon coupling. Furthermore, we apply the theory to two of the famous materials, graphene and MgB$_2$ where the geometric contributions account for approximately 50% and 90% of the total electron-phonon coupling constant, respectively. The quantum geometric contributions in the two systems are further bounded from below by topological contributions, arising from the winding numbers of nodal points/lines or the effective Euler number -- topological aspects previously unknown in MgB$_2$. Given that MgB$_2$ is a phonon-mediated superconductor with critical temperature about 39K, our results suggest that the nontrivial electron band geometry/topology might favor superconductivity with relatively high critical temperature.",2305.02340v1 2007-02-01,Probing the Coupling between Dark Components of the Universe,"We place observational constraints on a coupling between dark energy and dark matter by using 71 Type Ia supernovae (SNe Ia) from the first year of the five-year Supernova Legacy Survey (SNLS), the cosmic microwave background (CMB) shift parameter from the three-year Wilkinson Microwave Anisotropy Probe (WMAP), and the baryon acoustic oscillation (BAO) peak found in the Sloan Digital Sky Survey (SDSS). The interactions we study are (i) constant coupling delta and (ii) varying coupling delta(z) that depends on a redshift z, both of which have simple parametrizations of the Hubble parameter to confront with observational data. We find that the combination of the three databases marginalized over a present dark energy density gives stringent constraints on the coupling, -0.08 < delta < 0.03 (95% CL) in the constant coupling model and -0.4 < delta_0 < 0.1 (95% CL) in the varying coupling model, where delta_0 is a present value. The uncoupled LambdaCDM model (w_X = -1 and delta = 0) still remains a good fit to the data, but the negative coupling (delta < 0) with the equation of state of dark energy w_X < -1 is slightly favoured over the LambdaCDM model.",0702015v3 1994-08-03,Exact calculation of the ground state single-particle Green's function for the $1/r^2$ quantum many body system at integer coupling,"The ground state single particle Green's function describing hole propagation is calculated exactly for the $1/r^2$ quantum many body system at integer coupling. The result is in agreement with a recent conjecture of Haldane.",9408008v1 1997-08-25,Effects of Phonons and Nuclear Spins on the Tunneling of a Domain Wall,"We consider the quantum dynamics of a magnetic domain wall at low temperatures, where dissipative couplings to magnons and electrons are very small. The wall motion is then determined by its coupling to phonons and nuclear spins, and any pinning potentials. In the absence of nuclear spins there is a dominant superOhmic 1-phonon coupling to the wall velocity, plus a strongly T-dependent Ohmic coupling to pairs of phonons. There is also a T-independent Ohmic coupling between single phonons and the wall chirality, which suppresses ``chirality tunneling''. We calculate the effect of these couplings on the T-dependent tunneling rate of a wall out of a pinning potential. Nuclear spins have a very strong and hitherto unsuspected influence on domain wall dynamics, coming from a hyperfine-mediated coupling to the domain wall position. For $k_B T \gg \omega_{0}$ this coupling yields a spatially random potential, fluctuating at a rate governed by the nuclear $T_2$. When $k_B T \ll \omega_{0}$, the hyperfine potential fluctuates around a linear binding potential. The wall dynamics is influenced by the fluctuations of this potential, ie., by the nuclear spin dynamics. Wall tunneling can occur when fluctuations open an occasional ``tunneling window''. This changes the crossover to tunneling and also causes a slow ""wandering"", in time, of the energy levels associated with domain wall motion inside the pinning potential. This effect is fairly weak in $Ni$- and $Fe$- based magnets, and we give an approximate treatment of its effect on the tunneling dynamics, as well as a discussion of the relationship to recent domain wall tunneling experiments.",9708191v1 2002-11-03,Damping of coupled phonon--plasmon modes,"The effect of free carriers on dispersion and damping of coupled phonon-plasmon modes is considered in the long-wave approximation. The electron and phonon scattering rate as well as Landau damping are taken into account.",0211040v1 2003-03-20,Dephasing due to background charge fluctuations,"In quantum computation, quantum coherence must be maintained during gate operation. However, in physical implementations, various couplings with the environment are unavoidable and can lead to a dephasing of a quantum bit(qubit). The background charge fluctuations are an important dephasing process, especially in a charge qubit system. We examined the dephasing rate of a qubit due to random telegraph noise. Solving stochastic differential equations, we obtained the dephasing rate of a qubit constructed of a coupled-dot system; we applied our results to the charge Josephson qubit system. We examined the dephasing rates due to two types of couplings between the coupled-dot system and the background charge, namely, fluctuation in the tunnel coupling constant and fluctuation in the asymmetric bias. For a strong coupling condition, the dephasing rate was inversely proportional to the time constant of the telegraph noise. When there is fluctuation in the tunnel coupling constant, Gaussian decay occurs in the initial regime. We also examined the rate of dephasing due to many impurity sites. For a weak coupling condition with fluctuation in the asymmetric bias, the obtained dephasing rate coincided with that obtained by the perturbation method using the spectral weight of a boson thermal bath, which is proportional to the inverse of the frequency.",0303412v1 2004-03-17,"Dynamical mean-filed approximation to small-world networks of spiking neurons: From local to global, and/or from regular to random couplings","By extending a dynamical mean-field approximation (DMA) previously proposed by the author [H. Hasegawa, Phys. Rev. E {\bf 67}, 41903 (2003)], we have developed a semianalytical theory which takes into account a wide range of couplings in a small-world network. Our network consists of noisy $N$-unit FitzHugh-Nagumo (FN) neurons with couplings whose average coordination number $Z$ may change from local ($Z \ll N $) to global couplings ($Z=N-1$) and/or whose concentration of random couplings $p$ is allowed to vary from regular ($p=0$) to completely random (p=1). We have taken into account three kinds of spatial correlations: the on-site correlation, the correlation for a coupled pair and that for a pair without direct couplings. The original $2 N$-dimensional {\it stochastic} differential equations are transformed to 13-dimensional {\it deterministic} differential equations expressed in terms of means, variances and covariances of state variables. The synchronization ratio and the firing-time precision for an applied single spike have been discussed as functions of $Z$ and $p$. Our calculations have shown that with increasing $p$, the synchronization is {\it worse} because of increased heterogeneous couplings, although the average network distance becomes shorter. Results calculated by out theory are in good agreement with those by direct simulations.",0403415v3 2005-11-17,Coupled-Cluster Theory for Systems of Bosons in External Traps,"A coupled-cluster approach for systems of $N$ bosons in external traps is developed. In the coupled-cluster approach the exact many-body wavefunction is obtained by applying an exponential operator $\exp{T}$ to the ground configuration $|\phi_0>$. The natural ground configuration for bosons is, of course, when all reside in a single orbital. Because of this simple structure of $|\phi_0>$, the appearance of excitation operators $T=\sum_{n=1}^N T_n$ for bosons is much simpler than for fermions. We can treat very large numbers of bosons with coupled-cluster expansions. In a substantial part of this work, we address the issue of size consistency for bosons and enquire whether truncated coupled-cluster expansions are size consistent. We show that, in contrast to the familiar situation for fermions for which coupled-cluster expansions are size consistent, for bosons the answer to this question {\it depends} on the choice of ground configuration. Utilizing the natural ground configuration, working equations for the truncated coupled-cluster with $T=T_1+T_2$, i.e., coupled-cluster singles doubles (CCSD) are explicitly derived. Finally, an illustrative numerical example for a condensate with up to N=10000 bosons in an harmonic trap is provided and analyzed. The results are highly promising.",0511430v1 2006-02-27,Effective Crystalline Electric Field Potential in a j-j Coupling Scheme,"We propose an effective model on the basis of a $j$-$j$ coupling scheme to describe local $f$-electron states for realistic values of Coulomb interaction $U$ and spin-orbit coupling $\lambda$, for future development of microscopic theory of magnetism and superconductivity in $f^n$-electron systems, where $n$ is the number of local $f$ electrons. The effective model is systematically constructed by including the effect of a crystalline electric field (CEF) potential in the perturbation expansion in terms of $1/\lambda$. In this paper, we collect all the terms up to the first order of $1/\lambda$. Solving the effective model, we show the results of the CEF states for each case of $n$=2$\sim$5 with $O_{\rm h}$ symmetry in comparison with those of the Stevens Hamiltonian for the weak CEF. In particular, we carefully discuss the CEF energy levels in an intermediate coupling region with $\lambda/U$ in the order of 0.1 corresponding to actual $f$-electron materials between the $LS$ and $j$-$j$ coupling schemes. Note that the relevant energy scale of $U$ is the Hund's rule interaction. It is found that the CEF energy levels in the intermediate coupling region can be quantitatively reproduced by our modified $j$-$j$ coupling scheme, when we correctly take into account the corrections in the order of $1/\lambda$ in addition to the CEF terms and Coulomb interactions which remain in the limit of $\lambda$=$\infty$. As an application of the modified $j$-$j$ coupling scheme, we discuss the CEF energy levels of filled skutterudites with $T_{\rm h}$ symmetry.",0602646v2 2006-10-30,Complexity of Self-similar Hierarchical Ensembles,"Within the framework of generalized combinatorial approach, the complexity is determined for infinite set of self-similar hierarchical ensembles. This complexity is shown to increase with strengthening of the hierarchy coupling to the value, which decreases with growth of both scattering of this coupling and non-extensivity parameter.",0610824v1 2006-11-06,Spin relaxation in a generic two-dimensional spin-orbit coupled system,"We study the relaxation of a spin density injected into a two-dimensional electron system with generic spin-orbit interactions. Our model includes the Rashba as well as linear and cubic Dresselhaus terms. We explicitly derive a general spin-charge coupled diffusion equation. Spin diffusion is characterized by just two independent dimensionless parameters which control the interplay between different spin-orbit couplings. The real-time representation of the diffuson matrix (Green's function of the diffusion equation) is evaluated analytically. The diffuson describes space-time dynamics of the injected spin distribution. We explicitly study two regimes: The first regime corresponds to negligible spin-charge coupling and is characterized by standard charge diffusion decoupled from the spin dynamics. It is shown that there exist several qualitatively different dynamic behaviors of the spin density, which correspond to various domains in the spin-orbit coupling parameter space. We discuss in detail a few interesting phenomena such as an enhancement of the spin relaxation times, real space oscillatory dynamics, and anisotropic transport. In the second regime, we include the effects of spin-charge coupling. It is shown that the spin-charge coupling leads to an enhancement of the effective charge diffusion coefficient. We also find that in the case of strong spin-charge coupling, the relaxation rates formally become complex and the spin/charge dynamics is characterized by real time oscillations. These effects are qualitatively similar to those observed in spin-grating experiments [Weber et al., Nature 437, 1330 (2005)].",0611165v1 2007-01-02,Decoherence of a Spin Qubit Coupled with Spin Chain,"In this report, we examine the relaxation phenomena of a spin qubit coupled to a spin chain with a $1/r^2$ interaction.",0701036v3 1994-05-05,Classical and Quantum Solutions of Conformally Related Multidimensional Cosmological Models,"Consider multidim. universes M= R x M_1 x ... x M_n with D = 1+ d_1 .. + d_n, where M_i of dimension d_i are of have constant curvature and compact for i>1. For Lagrangian models L(R,phi) on M which depend only on Ricci curvature R and a scalar field phi, there exists an explicit description of conformal equivalence, with the minimal coupling model and the conformal coupling model as distinguished representatives of a conformal class. For the conformally coupled model we study classical solutions and their relation to solutions in the equivalent minimally coupled model. The domains of equivalence are separated by certain critical values of the scalar field phi. Furthermore the coupling constant xi of the coupling between phi and R is critical at both, the minimal value xi=0 and the conformal value xi_c={D-2}/{4(D-1)}. In different noncritical regions of $xi$ the solutions behave qualitatively different. For vanishing potential of the minimally coupled scalar field we find a multidimensional generalization of Kasner's solution. Its scale factor singularity vanishes in the conformal coupling model. Static internal spaces in the minimal model become dynamical in the conformal one. The nonsingular conformal solution has a particular interesting region, where internal spaces shrink while the external space expands. While the Lorentzian solution relates to a creation of the universe at finite scale, it Euclidean counterpart is an (instanton) wormhole. Solving the Wheeler de Witt equation we obtain the quantum counterparts to the classical solutions. A real Euclidean quantum wormhole is obtained in a special case.",9405011v1 1996-01-10,Primordial Density Fluctuations in Phase Coupling Gravity,"In this paper we study the evolution of density perturbations in the framework of Phase Coupling Gravity theory at the very early universe. We show that these perturbation display an exponential-like behaviour.",9601016v1 1996-09-26,Gravitional coupling constant in higher dimensions,"Assuming the equivalence of FRW-cosmological models and their Newtonian counterparts, we propose using the Gauss law in arbitrary dimension a general relation between the Newtonian gravitational constant G and the gravitational coupling constant \kappa.",9609061v1 1997-06-25,Solutions of Quantum Gravity Coupled to the Scalar Field,"We consider the Wheeler-De Witt equation for canonical quantum gravity coupled to massless scalar field. After regularizing and renormalizing this equation, we find a one-parameter class of its solutions.",9706076v1 2002-06-29,Bianchi - Euler system for relativistice fluids and Bel - Robinson type energy,"We write a first order symmetric hyperbolic system coupling the Riemann with the dynamical acceleration of a relativistic fluid. W determine the associated, coupled, Bel - Robinson energy, and the integral equality that it satisfies.",0207002v1 2006-08-11,"GL(3,R) gauge theory of gravity coupled with an electromagnetic field","Consistency of $GL(3,R)$ gauge theory of gravity coupled with an external electromagnetic field, is studied. It is shown that possible restrictions on Maxwell field can be avoided through introduction of auxiliary fields.",0608057v1 2001-05-22,Quartic Gauge Boson Couplings Results at LEP,"The study of charged and neutral boson vertices has been performed in different production channels at the LEP experiments. Decay rates and kinematic properties of these events are exploited to set constraints on the corresponding gauge couplings.",0105063v1 1993-11-23,Running Coupling in SU(3) Yang-Mills Theory,"We report about our ongoing computation of running coupling constants in asymptotically free theories using the recursive finite size scaling technique. The latest results for the SU(3) Yang-Mills theory are presented.",9311033v1 1994-08-21,The (LATTICE) QCD Potential and Running Coupling: How to Accurately Interpolate between Multi-Loop QCD and the String Picture,"We present a simple parameterization of a running coupling constant, defined via the static potential, that interpolates between 2-loop QCD in the UV and the string prediction in the IR. Besides the usual $\Lam$-parameter and the string tension, the coupling depends on one dimensionless parameter, determining how fast the crossover from UV to IR behavior occurs (in principle we know how to take into account any number of loops by adding more parameters). Using a new Ansatz for the LATTICE potential in terms of the continuum coupling, we can fit quenched and unquenched Monte Carlo results for the potential down to ONE lattice spacing, and at the same time extract the running coupling to high precision. We compare our Ansatz with 1-loop results for the lattice potential, and use the coupling from our fits to quantitatively check the accuracy of 2-loop evolution, compare with the Lepage-Mackenzie estimate of the coupling extracted from the plaquette, and determine Sommer's scale $r_0$ much more accurately than previously possible. For pure SU(3) we find that the coupling scales on the percent level for $\beta\geq 6$.",9408016v4 1997-09-29,Scalar-gauge dynamics in (2+1) dimensions at small and large scalar couplings,"We present the results of a detailed calculation of the excitation spectrum of states with quantum numbers J^{PC}=0++, 1-- and 2++ in the three-dimensional SU(2) Higgs model at two values of the scalar self-coupling and for fixed gauge coupling. In the context of studies of the electroweak phase transition at finite temperature these couplings correpond to tree-level, zero temperature Higgs masses of 35 GeV and 120 GeV, respectively. We also study the properties of Polyakov loop operators, which serve to test the confining properties of the model in the symmetric phase. At both values of the scalar coupling we obtain masses of bound states consisting entirely of gauge degrees of freedom (""W-balls""), which are very close to those obtained in the pure gauge theory. We conclude that the previously observed, approximate decoupling of the scalar and gauge sectors of the theory persists at large scalar couplings. We study the crossover region at large scalar coupling and present a scenario how the confining properties of the model in the symmetric phase are lost inside the crossover by means of flux tube decay. We conclude that the underlying dynamics responsible for the observed dense spectrum of states in the Higgs region at large couplings must be different from that in the symmetric phase.",9709145v2 1999-11-26,Renormalization group flow of SU(3) lattice gauge theory - Numerical studies in a two coupling space,"We investigate the renormalization group (RG) flow of SU(3) lattice gauge theory in a two coupling space with couplings $\beta_{11}$ and $\beta_{12}$ corresponding to $1\times 1$ and $1\times 2$ loops respectively. Extensive numerical calculations of the RG flow are made in the fourth quadrant of this coupling space, i.e., $\beta_{11}>0$ and $\beta_{12}<0$. Swendsen's factor two blocking and the Schwinger-Dyson method are used to find an effective action for the blocked gauge field. The resulting renormalization group flow runs quickly towards an attractive stream which has an approximate line shape. This is numerical evidence of a renormalized trajectory which locates close to the two coupling space. A model flow equation which incorporates a marginal coupling (asymptotic scaling term), an irrelevant coupling and a non-perturbative attraction towards the strong coupling limit reproduces qualitatively the observed features. We further examine the scaling properties of an action which is closer to the attractive stream than the currently used improved actions. It is found that this action shows excellent restoration of rotational symmetry even for coarse lattices with $a \sim 0.3$ fm.",9911033v2 2003-07-10,Diquark condensation at strong coupling,"The possibility of diquark condensation at sufficiently large baryon chemical potential and zero temperature is analyzed in QCD at strong coupling. In agreement with other strong coupling analysis, it is found that a first order phase transition separates a low density phase with chiral symmetry spontaneously broken from a high density phase where chiral symmetry is restored. In none of the phases diquark condensation takes place as an equilibrium state, but, for any value of the chemical potential, there is a metastable state characterized by a non-vanishing diquark condensate. The energy difference between this metastable state and the equilibrium state decreases with the chemical potential and is minimum in the high density phase. The results indicate that there is attraction in the quark-quark sector also at strong coupling, and that the attraction is more effective at high baryon density, but for infinite coupling it is not enough to produce diquark condensation. It is argued that the absence of diquark condensation is not a peculiarity of the strong coupling limit, but persists at sufficiently large finite couplings.",0307019v2 1994-03-24,QCD Accurately Predicts the Induced Pseudoscalar Coupling Constant,"Using chiral Ward identities of QCD, we derive a relation for the induced pseudoscalar coupling constant which is accurate within a few percent, $g_P = 8.44 \pm 0.16$.",9403351v1 1994-09-22,Threshold Effects on the QCD Coupling $α_{\overline{MS}}$,"The matching condition which determines the effect of a heavy quark threshold on the running of the QCD coupling $\alpha_{\overline{MS}}$ is reviewed. The matching scale is arbitrary to some extent. However, this affects the value of $\alpha_{\overline{MS}}$ away from the threshold region only marginally.",9409390v1 1995-11-30,Renormalization group evolution of R-parity-violating Yukawa couplings,"We study the evolution of $R$-parity-violating (RPV) couplings in the minimum supersymmetric standard model, between the electroweak and grand unification scales, assuming a family hierarchy for these coupling strengths. Particular attention is given to solutions where both the $R$-conserving and $R$-violating top quark Yukawa couplings simultaneously approach infrared fixed points; these we analyse both algebraically and with numerical solutions of the evolution equations at one-loop level. We identify constraints on these couplings at the GUT scale, arising from lower limits on the top quark mass. We show that fixed points offer a new source of bounds on RPV couplings at the electroweak scale. We derive evolution equations for the CKM matrix, and show that RPV couplings affect the scaling of the unitarity triangle. The fixed-point behaviour is compatible with all present experimental constraints. However, fixed-point values of RPV top-quark couplings would require the corresponding sleptons or squarks to have mass $\agt m_t$ to suppress strong new top decays to sparticles.",9511473v1 1996-05-23,The Soft Pomeron,"The soft pomeron successfully correlates a wide variety of data. Its properties seem rather simple: it couples to single quarks and its coupling factorises.",9605383v1 1997-01-14,Predictions for s-Wave and p-Wave Heavy Baryons from Sum Rules and Constituent Quark Model (I): Strong Interactions,"We study the strong interactions of the L=1 orbitally excited baryons with one heavy quark in the framework of the Heavy Hadron Chiral Perturbation Theory. To leading order in the heavy mass expansion, the interaction Lagrangian describing the couplings of these states among themselves and with the ground state heavy baryons contains 46 unknown couplings. We derive sum rules analogous to the Adler-Weisberger sum rule which constrain these couplings and relate them to the couplings of the s-wave heavy baryons. Using a spin 3/2 baryon as a target, we find a sum rule expressing the deviation from the quark model prediction for pion couplings to s-wave states in terms of couplings of the p-wave states. In the constituent quark model these couplings are related and can be expressed in terms of only two reduced matrix elements. Using recent CLEO data on $\Sigma_c^{*}$ and $\Lambda_{c1}^+$ strong decays, we determine some of the unknown couplings in the chiral Lagrangian and the two quark model reduced matrix elements. Specific predictions are made for the decay properties of all L=1 charmed baryons.",9701291v2 1998-01-23,A Model Independent Analysis of LEP and SLD Data on Z-Decays; is the Standard Model Confirmed?,"A model independent analysis has been performed on the LEP and SLD data on Z decays. Using only very weak theoretical assumptions, the effective vector and axial-vector couplings of leptons, c quarks and b quarks have been extracted. Although the lepton and c quark couplings agree well with Standard Model predictions, those of the b quark show deviations of more than three standard deviations. The effect is mainly in the right-handed b quark coupling, the left-handed coupling being consistent (at the 2$\sigma$ level) with the Standard Model prediction. The probability that the observed deviations of all the measured effective couplings are statistical fluctuations from lepton universality and the Standard Model is estimated to be 0.9%. The estimated probability that the deviations in the leptonic and b quark couplings alone are a fluctuation is 0.18%. A thorough discussion is made of the internal consistency of the different measurements contributing to the average values $A_l$ and $A_b$ used to extract the b quark couplings, as well as possible sources of systematic error that may not, hitherto, have been taken into account. Excluding \tpol~ measurements, which show internal inconsistencies, from the averages increases the deviations of the extracted b quark couplings from the Standard Model predictions to the four standard deviation level.",9801403v2 1999-03-25,Applications of the Reduction of Couplings,"Applications of the principle of reduction of couplings to the standard model and supersymmetric grand unified theories are reviewed. Phenomenological applications of renormalization group invariant sum rules for soft supersymmetry-breaking parameters are also reviewed.",9903482v1 2002-01-23,Measurements of the SUSY Higgs self-couplings and the reconstruction of the Higgs potential,"We address the issue of the reconstruction of the scalar potential of a two-Higgs doublet model having in mind that of the MSSM. We first consider the general CP conserving dim-4 effective potential. To fully reconstruct this potential, we show that even if all the Higgs masses and their couplings to the standard model particles are measured one needs not only to measure certain trilinear Higgs self-couplings but some of the quartic couplings as well. We also advocate expressing the Higgs self couplings in the mass basis. We show explicitly, that in the so-called decoupling limit, the most easily accessible Higgs self-couplings are given in terms of the Higgs mass while all other dependencies on the parameters of the general effective potential are screened. This helps also easily explain how, in the MSSM, the largest radiative corrections which affect these self couplings are reabsorbed by using the corrected Higgs mass. We also extend our analysis to higher order operators in the effective Higgs potential. While the above screening properties do not hold, we argue that these effects must be small and may not be measured considering the foreseen poor experimental precision in the extraction of the SUSY Higgs self-couplings.",0201219v1 2005-04-11,Coupling Unifications in Gauge-Higgs Unified Orbifold Models,"Supersymmetric gauge theories, in higher dimensions compactified in an orbifold, give a natural framework to unify the gauge bosons, Higgs fields and even the matter fields in a single multiplet of the unifying gauge symmetry. The extra dimensions and the supersymmetry are the two key ingredients for such an unification. In this work, we investigate various scenarios for the unification of the three gauge couplings, and the Yukawa couplings in the Minimal Supersymmetric Standard Model (MSSM), as well as the trilinear Higgs couplings \lambda and \kappa of the Non-Minimal Supersymmetric Standard Model (NMSSM). We present an SU(8) model in six dimensions with N=2 supersymmetry, compactified in a T^2/Z_6 orbifold which unifies the three gauge couplings with \lambda and \kappa of NMSSM. Then, we present an SU(9) model in 6D, which, in addition, includes partial unification of Yukawa couplings, either for the up-type (top quark and Dirac tau-neutrino) or down-type (bottom quark and tau lepton). We also study the phenomenological implications of these various unification scenarios using the appropriate renormalization group equations, and show that such unification works very well with the measured low energy values of the couplings. The predicted upper bounds for the lightest neutral Higgs boson mass in our model is higher than those in MSSM, but lower that those in the general NMSSM (where the couplings \lambda and \kappa are arbitrary). Some of the predictions of our models can be tested in the upcoming Large Hadron Collider.",0504082v1 2005-09-13,Stability of Subsequent-to-Leading-Logarithm Corrections to the Effective Potential for Radiative Electroweak Symmetry Breaking,"We demonstrate the stability under subsequent-to-leading logarithm corrections of the quartic scalar-field coupling constant $\lambda$ and the running Higgs boson mass obtained from the (initially massless) effective potential for radiatively broken electroweak symmetry in the single-Higgs-Doublet Standard Model. Such subsequent-to-leading logarithm contributions are systematically extracted from the renormalization group equation considered beyond one-loop order. We show $\lambda$ to be the dominant coupling constant of the effective potential for the radiatively broken case of electroweak symmetry. We demonstrate the stability of $\lambda$ and the running Higgs boson mass through five orders of successively subleading logarithmic corrections to the scalar-field-theory projection of the effective potential for which all coupling constants except the dominant coupling constant $\lambda$ are disregarded. We present a full next-to-leading logarithm potential in the three dominant Standard Model coupling constants ($t$-quark-Yukawa, $\alpha_s$, and $\lambda$) from these coupling constants' contribution to two loop $\beta$- and $\gamma$-functions. Finally, we demonstrate the manifest order-by-order stability of the physical Higgs boson mass in the 220-231 GeV range. In particular, we obtain a 231 GeV physical Higgs boson mass inclusive of the $t$-quark-Yukawa and $\alpha_s$ coupling constants to next-to-leading logarithm order, and inclusive of the smaller $SU(2)\times U(1)$ gauge coupling constants to leading logarithm order.",0509122v2 2005-11-14,Couplings of Vector-Spinor Representation for SO(10) Model Building,"Higgs multiplet in the vector-spinor representations of SO(10), i.e., the $144+\bar{144}$ multiplet can break the SO(10) gauge symmetry spontaneously in one step down to the Standard Model gauge group symmetry $SU(3)_C\times SU(2)_L\times U(1)_Y$ and a recent analysis has used such vector-spinors for building a new class of SO(10) grand unification models (hep-ph/0506312) . Here we discuss the techniques for the computation of several classes of vector-spinor couplings using the Basic Theorem on the SO(2N) vertex expansion developed by the authors. The computations include the cubic couplings of the vector-spinors with SO(10) tensors, quartic self-couplings of the vector-spinors, and couplings of the vector-spinors with spinor representations of SO(10). The last set include couplings of vector-spinors with the 16-plets of quarks and lepton and with the 16 and $\bar{16}$ of Higgs. These couplings provide a crucial tool for further development of the SO(10) grand unification using vector-spinor representations. These include study of quark-lepton masses, analysis of dimension five operators including baryon and lepton number violating operators, and study of neutrino masses and mixings. Illustrative examples are given for their computation using a sample of vector-spinor couplings.",0511172v1 2006-06-02,Evidence for infrared finite coupling in Sudakov resummation: a revised view-point,"I show that Sudakov resummation takes a particularly transparent form if one deals with the second logarithmic derivative of the short distance coefficient functions for deep inelastic scattering and the Drell-Yan process. A uniquely defined Sudakov exponent emerges, and I conjecture that the leftover constant terms not included in the exponent are given by the second logarithmic derivative of the massless quark form factor. The meaning of a previously obtained large $N_f$ evidence for an infrared finite perturbative Sudakov coupling is reconsidered. This coupling is reinterpreted as a Minkowskian coupling, making the introduction of a low-energy non-perturbative modification of the corresponding Euclidean coupling a priori necessary. Some hints for a Banks-Zaks type of fixed point in the Euclidean coupling at finite $N_f$ are nevertheless pointed out, and strong evidence is provided in favor of its universality. A criterion to select in a unique way the proper Euclidean Sudakov coupling relevant to the issue of power corrections is suggested.",0606033v2 2006-12-15,"Reply to Comment on ""Mass and K-Lambda Coupling of the N*(1535)""","Here we give our reply to the comment by Sibirtsev et al on our paper ``Mass and K-Lambda Coupling of the N*(1535)"".",0612192v1 2007-02-17,"U-boson production in e+e- annihilations, psi and Upsilon decays, and Light Dark Matter","We recall how a new light gauge boson emerged in Supersymmetric extensions of the Standard Model with an extra singlet superfield, and how it could behave very much as a light pseudoscalar, with the corresponding symmetry broken at a scale higher than electroweak. Such a new gauge boson U, light and very weakly coupled, allows for Light Dark Matter particles, which could be at the origin of the 511 keV line from the galactic bulge. Could it be found directly in e+e- annihilations ? Not so easily, due to various constraints on its couplings, especially axial ones, leading to an axionlike behavior or extra parity-violation effects. Searches for the decay Upsilon -> gamma + invisible U may be used to constrain severely its axial coupling to the electron, f_eA = f_bA, to be less than about 10^-6 m_U(MeV). The vector coupling to the electron may in principle be larger. We find from g_mu-2, under reasonable assumptions, that this coupling can be at most as large as ~ 1.3 10^-3, for m_U < m_mu. Such a coupling of the order of 10^-3 could also be responsible for the somewhat large value of g_mu-2, compared to Standard Model expectations. The U couplings to electrons are otherwise likely to be smaller, e.g. \lsim 3 10^-6 m_U(MeV), if the couplings to neutrinos and electrons are similar. This restricts significantly the possibility of detecting a light U boson in e+e- -> gamma U. Despite that, U exchanges can provide annihilation cross sections of LDM particles of the appropriate size, even if this may require that light dark matter be relatively strongly self-interacting.",0702176v1 1991-10-11,Correlation Functions of Local Operators in 2D Gravity Coupled to Minimal Matter,"Recent advances are being discussed on the calculation, within the conformal field theory approach, of the correlation functions for local operators in the theory of 2D gravity coupled to the minimal models of matter.",9110030v1 1991-10-12,BRST Analysis of Physical States for 2D (Super) Gravity Coupled to (Super) Conformal Matter,"We summarize some recent results on the BRST analysis of physical states of 2D gravity coupled to c<=1 conformal matter and the supersymmetric generalization.",9110031v1 1992-10-06,Twisted Sector Yukawa Couplings for the $Z_3\times Z_3$ Orbifold,"The moduli dependent Yukawa couplings between twisted sectors of the $Z_3\times Z_3$ orbifold are studied.",9210030v1 1993-01-19,Twisted Sector Yukawa Couplings For The ${\bf Z}_M\times {\bf Z}_N$ Orbifolds,"The moduli dependent Yukawa couplings between twisted sectors of ${\bf Z}_M\times {\bf Z}_N$ Coxeter orbifolds are studied.",9301079v1 1993-02-10,Constrained Dynamics of the Coupled Abelian Two-Form,"I present the reduction of phase space of the theory of an antisymmetric tensor potential coupled to an abelian gauge field, using Dirac's procedure. Duality transformations on the reduced phase space are also discussed.",9302046v1 1993-04-26,Wess-Zumino-Witten model off criticality,"We study the renormalization group flow properties of the Wess-Zumino-Witten model in the region of couplings between $g^2=0$ and $g^2=4\pi/k$, by evaluating the two-loop Zamolodchikov's $c$-function. We also discuss the region of negative couplings.",9304127v1 1998-03-31,On the value of coupling constant,"Using an analogy between Bogomol'nyi bound and the harmonic oscillator in quantum mechanics we propose a possible explanation of the coupling constant numerical value at the grand unification scale. It is found to be $1/8\pi$.",9803256v1 1998-05-25,Coupling Constant Dependence in the Thermodynamics of N=4 Supersymmetric Yang-Mills Theory,"The free energy of the maximally supersymmetric SU(N) gauge theory at temperature T is expected to scale, in the large N limit, as N^2 T^4 times a function of the 't Hooft coupling, f(g_{YM}^2 N). In the strong coupling limit the free energy has been deduced from the near-extremal 3-brane geometry, and its normalization has turned out to be 3/4 times that found in the weak coupling limit. In this paper we calculate the leading correction to this result in inverse powers of the coupling, which originates from the R^4 terms in the tree level effective action of type IIB string theory. The correction to 3/4 is positive and of order (g_{YM}^2 N)^{-3/2}. Thus, f(g_{YM}^2 N) increases as the 't Hooft coupling is decreased, in accordance with the expectation that it should be approaching 1 in the weak coupling limit. We also discuss similar corrections for other conformal theories describing coincident branes. In particular, we suggest that the coupling-independence of the near extremal entropy for D1-branes bound to D5-branes is related to the vanishing of the Weyl tensor of AdS_3\times S^3.",9805156v4 1999-03-10,Reduction of Coupling Parameters and Duality,"The general method of the reduction in the number of coupling parameters is discussed. Using renormalization group invariance, theories with several independent couplings are related to a set of theories with a single coupling parameter. The reduced theories may have particular symmetries, or they may not be related to any known symmetry. The method is more general than the imposition of invariance properties. Usually, there are only a few reduced theories with an asymptotic power series expansion corresponding to a renormalizable Lagrangian. There also exist `general' solutions containing non-integer powers and sometimes logarithmic factors. As an example for the use of the reduction method, the dual magnetic theories associated with certain supersymmetric gauge theories are discussed. They have a superpotential with a Yukawa coupling parameter. This parameter is expressed as a function of the gauge coupling. Given some standard conditions, a unique, isolated power series solution of the reduction equations is obtained. After reparametrization, the Yukawa coupling is proportional to the square of the gauge coupling parameter. The coefficient is given explicitly in terms of the numbers of colors and flavors. `General' solutions with non-integer powers are also discussed. A brief list is given of other applications of the reduction method.",9903092v1 1999-04-23,The Complete Brane Solution in D-dimensional Coupled Gravity System,"In this letter we present the complete explicit brane solution in D-dimensional coupled gravity system.",9904157v1 2000-07-09,Wess Zumino Couplings for Generalized Sigma Orbifold Fixed-points,"The Wess-Zumino couplings for generalized sigma-orbifold fixed-points are presented and the generalized GS 6-form that encoding the complete sigma-standard gauge-gravitational-non standard gauge anomaly and its opposite inflow is derived.",0007068v1 2000-08-02,On Chapline-Manton couplings: a cohomological approach,"Chern-Simons couplings between Yang-Mills gauge fields and an abelian 2-form are derived by means of cohomological arguments.",0008022v1 2003-09-28,Finiteness of quantum gravity coupled with matter in three spacetime dimensions,"As it stands, quantum gravity coupled with matter in three spacetime dimensions is not finite. In this paper I show that an algorithmic procedure that makes it finite exists, under certain conditions. To achieve this result, gravity is coupled with an interacting conformal field theory C. The Newton constant and the marginal parameters of C are taken as independent couplings. The values of the other irrelevant couplings are determined iteratively in the loop- and energy-expansions, imposing that their beta functions vanish. The finiteness equations are solvable thanks to the following properties: the beta functions of the irrelevant couplings have a simple structure; the irrelevant terms made with the Riemann tensor can be reabsorbed by means of field redefinitions; the other irrelevant terms have, generically, non-vanishing anomalous dimensions. The perturbative expansion is governed by an effective Planck mass that takes care of the interactions in the matter sector. As an example, I study gravity coupled with Chern-Simons U(1) gauge theory with massless fermions, solve the finiteness equations and determine the four-fermion couplings to two-loop order. The construction of this paper does not immediately apply to four-dimensional quantum gravity.",0309250v4 2004-10-27,"Unification of Gravitation, Gauge Field and Dark Energy","This paper is composed of two correlated topics: 1. unification of gravitation with gauge fields; 2. the coupling between the daor field and other fields and the origin of dark energy. After introducing the concept of ``daor field"" and discussing the daor geometry, we indicate that the complex daor field has two kinds of symmetry transformations. Hence the gravitation and SU(1,3) gauge field are unified under the framework of the complex connection. We propose a first-order nonlinear coupling equation of the daor field, which includes the coupling between the daor field and SU(1,3) gauge field and the coupling between the daor field and the curvature, and from which Einstein's gravitational equation can be deduced. The cosmological observations imply that dark energy cannot be zero, and which will dominate the doom of our Universe. The real part of the daor field self-coupling equation can be regarded as Einstein's equation endowed with the cosmological constant. It shows that dark energy originates from the self-coupling of the space-time curvature, and the energy-momentum tensor is proportional to the square of coupling constant \lambda. The dark energy density given by our scenario is in agreement with astronomical observations. Furthermore, the Newtonian gravitational constant G and the coupling constant \epsilon of gauge field satisfy G= \lambda^{2}\epsilon^{2}.",0410266v2 2005-12-06,Exploring AdS Waves Via Nonminimal Coupling,"We consider nonminimally coupled scalar fields to explore the Siklos spacetimes in three dimensions. Their interpretation as exact gravitational waves propagating on AdS restrict the source to behave as a pure radiation field. We show that the related pure radiation constraints single out a unique self-interaction potential depending on one coupling constant. For a vanishing coupling constant, this potential reduces to a mass term with a mass fixed in terms of the nonminimal coupling parameter. This mass dependence allows the existence of several free cases including massless and tachyonic sources. There even exists a particular value of the nonminimal coupling parameter for which the corresponding mass exactly compensates the contribution generated by the negative scalar curvature, producing a genuinely massless field in this curved background. The self-interacting case is studied in detail for the conformal coupling. The resulting gravitational wave is formed by the superposition of the free and the self-interaction contributions, except for a critical value of the coupling constant where a non-perturbative effect relating the strong and weak regimes of the source appears. We establish a correspondence between the scalar source supporting an AdS wave and a pp wave by showing that their respective pure radiation constraints are conformally related, while their involved backgrounds are not. Finally, we consider the AdS waves for topologically massive gravity and its limit to conformal gravity.",0512074v2 2006-02-24,Dynamics of Flux Tubes in Large N Gauge Theories,"The gluonic field created by a static quark anti-quark pair is described via the AdS/CFT correspondence by a string connecting the pair which is located on the boundary of AdS. Thus the gluonic field in a strongly coupled large N CFT has a stringy spectrum of excitations. We trace the stability of these excitations to a combination of large N suppressions and energy conservation. Comparison of the physics of the N=infinity flux tube in the {\cal N}=4 SYM theory at weak and strong coupling shows that the excitations are present only above a certain critical coupling. The density of states of a highly excited string with a fold reaching towards the horizon of AdS is in exact agreement at strong coupling with that of the near-threshold states found in a ladder diagram model of the weak-strong coupling transition. We also study large distance correlations of local operators with a Wilson loop, and show that the fall off at weak coupling and N=infinity (i.e. strictly planar diagrams) matches the strong coupling predictions given by the AdS/CFT correspondence, rather than those of a weakly coupled U(1) gauge theory.",0602255v3 2003-01-24,Couplings of Uniform Spanniing Forests,"We prove the existence of an automorphism-invariant coupling for the wired and the free uniform spanning forests on Cayley graphs of finitely generated residually amenable groups.",0301291v2 2005-07-28,Poisson fiber bundles and coupling Dirac structures,"We give sufficient conditions for the existence of a Dirac structure on the total space of a Poisson fiber bundle endowed with a compatible connection. We also show that Cartan and Cartan-Hannay-Berry connections give rise to coupling Dirac structures.",0507594v1 2003-11-13,Bifurcations due to small time-lag in coupled excitable systems,"A system of ODE's is used to approximate the dynamics of two delayed coupled FitzHugh-Nagumo excitable units, and study the relevant bifurcations. It is shown that the Bautin bifurcation acts as the organizing center for the dynamics of ODE's for small time-lags.",0311025v1 2006-03-27,Synchronization and time shifts of dynamical patterns for mutually delay-coupled fiber ring lasers,"A pair of coupled erbium doped fiber ring lasers is used to explore the dynamics of coupled spatiotemporal systems. The lasers are mutually coupled with a coupling delay less than the cavity round-trip time. We study synchronization between the two lasers in the experiment and in a delay differential equation model of the system. Because the lasers are internally perturbed by spontaneous emission, we include a noise source in the model to obtain stochastic realizations of the deterministic equations. Both amplitude synchronization and phase synchronization are considered. We use the Hilbert transform to define the phase variable and compute phase synchronization. We find that synchronization increases with coupling strength in the experiment and the model. When the time series from two lasers are time-shifted in either direction by the delay time, approximately equal synchronization is frequently observed, so that a clear leader and follower cannot be identified. We define an algorithm to determine which laser leads the other when the synchronization is sufficiently different with one direction of time shift, and statistics of switches in leader and follower are studied. The frequency of switching between leader and follower increases with coupling strength, as might be expected since the lasers mutually influence each other more effectively with stronger coupling.",0603063v1 1996-04-17,Meson-hyperon couplings in the bound-state approach to the Skyrme model,"Strong pion and kaon couplings to hyperons are given in the bound-state approach to the Skyrme model.",9604022v1 2002-05-13,Effective Screened Potentials of Strongly Coupled Semiclassical Plasma,"The pseudopotentials of particle interaction of astrongly coupled semiclassical plasma, taking into account bothquantum-mechanical effects of diffraction at short distances andalso screening field effects at large distances are obtained. Thelimiting cases of potentials are considered.",0205036v1 2005-05-11,Quantum Gauge Theory Amplitude Solutions,"The $n$-point amplitudes of gauge and gravity theory are given as a series in the coupling. The recursive derivative expansion is used to find all of the coupling coefficients. Initial conditions to any bare Lagrangian, or of an improved action, are used to compute quantum amplitudes.",0505077v1 2005-08-14,Recirculating BBU thresholds for polarized HOMs with optical coupling,"We will derive the general theory of the beam-breakup instability in recirculating linear accelerators with coupled beam optics and with polarized higher order dipole modes. The bunches do not have to be at the same RF phase during each recirculation turn. This is important for the description of energy recovery linacs (ERLs) where beam currents become very large and coupled optics are used on purpose to increase the threshold current. A remarkable agreement with tracking data is demonstrated. The general formulas are then analyzed for several analytically solvable cases, which show: (a) Why different higher order modes (HOM) in one cavity can couple and cannot be considered individually, even when their frequencies are separated by much more than the resonance widths of the HOMs. For the Cornell ERL as an example, it is noted that optimum advantage of coupled optics is taken when the cavities are designed with an $x$-$y$ HOM frequency splitting of above 50MHz. The threshold current is then far above the design current of this accelerator. (b) How the $x$-$y$ coupling in the particle optics determines when modes can be considered separately. (c) That the increase of the threshold current obtainable by coupled optics and polarized modes diminishes roughly with the square root of the HOMs' quality factors. Therefore the largest advantages are achieved with cavities that are not specifically designed to minimize these quality factors, e.g. by means of HOM absorbers. (d) How multiple-turn recirculation interferes with the threshold improvements obtained with a coupled optics.",0508089v1 2006-02-14,The three-wave coupling coefficients for a cold magnetized plasma,"The resonant interaction between three waves in a uniform magnetized plasma is considered. Using the somewhat inaccessible result of the general theory we deduce the explicit expressions for the coupling coefficients of a cold magnetized two-component plasma.",0602089v1 2000-02-23,On the weak-coupling limit and complete positivity,"We consider two non-interacting systems embedded in a heat bath. If they remain dynamically independent, physical inconsistencies are avoided only if the single-system reduced dynamics is completely positive also beyond the weak-coupling limit.",0002062v1 2003-01-27,Two-Level System and Some Approximate Solutions in the Strong Coupling Regime,"In this paper we treat the 2--level system interacting with external fields without the rotating wave approximation and construct some approximate solutions in the strong coupling regime.",0301145v2 2004-09-27,Quantum information processing by NMR using a 5-qubit system formed by dipolar coupled spins in an oriented molecule,"Quantum Information processing by NMR with small number of qubits is well established. Scaling to higher number of qubits is hindered by two major requirements (i) mutual coupling among qubits and (ii) qubit addressability. It has been demonstrated that mutual coupling can be increased by using residual dipolar couplings among spins by orienting the spin system in a liquid crystalline matrix. In such a case, the heteronuclear spins are weakly coupled but the homonuclear spins become strongly coupled. In such circumstances, the strongly coupled spins can no longer be treated as qubits. However, it has been demonstrated elsewhere, that the $2^N$ energy levels of a strongly coupled N spin-1/2 system can be treated as an N-qubit system. For this purpose the various transitions have to be identified to well defined energy levels. This paper consists of two parts. In the first part, the energy level diagram of a heteronuclear 5-spin system is obtained by using a newly developed heteronuclear z-cosy (HET-Z-COSY) experiment. In the second part, implementation of logic gates, preparation of pseudopure states, creation of entanglement and entanglement transfer is demonstrated, validating the use of such systems for quantum information processing.",0409186v1 2007-04-04,Solving The High Energy Evolution Equation Including Running Coupling Corrections,"We study the solution of the nonlinear BK evolution equation with the recently calculated running coupling corrections [hep-ph/0609105, hep-ph/0609090]. Performing a numerical solution we confirm the earlier result of [hep-ph/0408216] that the high energy evolution with the running coupling leads to a universal scaling behavior for the dipole scattering amplitude. The running coupling corrections calculated recently significantly change the shape of the scaling function as compared to the fixed coupling case leading to a considerable increase in the anomalous dimension and to a slow-down of the evolution with rapidity. The difference between the two recent calculations is due to an extra contribution to the evolution kernel, referred to as the subtraction term, which arises when running coupling corrections are included. These subtraction terms were neglected in both recent calculations. We evaluate numerically the subtraction terms for both calculations, and demonstrate that when the subtraction terms are added back to the evolution kernels obtained in the two works the resulting dipole amplitudes agree with each other! We then use the complete running coupling kernel including the subtraction term to find the numerical solution of the resulting full non-linear evolution equation with the running coupling corrections. Again the scaling regime is recovered at very large rapidity.",0704.0612v2 2007-05-08,Controllability of the coupled spin-half harmonic oscillator system,"We present a control-theoretic analysis of the system consisting of a two-level atom coupled with a quantum harmonic oscillator. We show that by applying external fields with just two resonant frequencies, any desired unitary operator can be generated.",0705.1055v1 2007-05-14,Wandering breathers and self-trapping in weakly coupled nonlinear chains: classical counterpart of macroscopic tunneling quantum dynamics,"We present analytical and numerical studies of phase-coherent dynamics of intrinsically localized excitations (breathers) in a system of two weakly coupled nonlinear oscillator chains. We show that there are two qualitatively different dynamical regimes of the coupled breathers, either immovable or slowly-moving: the periodic transverse translation (wandering) of low-amplitude breather between the chains, and the one-chain-localization of high-amplitude breather. These two modes of coupled nonlinear excitations, which involve large number of anharmonic oscillators, can be mapped onto two solutions of a single pendulum equation, detached by a separatrix mode. We also study two-chain breathers, which can be considered as bound states of discrete breathers with different symmetry and center locations in the coupled chains, and bifurcation of the anti-phase two-chain breather into the one-chain one. Delocalizing transition of 1D breather in 2D system of a large number of parallel coupled nonlinear chains is described, in which the breather, initially excited in a given chain, abruptly spreads its vibration energy in the whole 2D system upon decreasing breather frequency or amplitude below the threshold one. The threshold breather frequency is above the cut off phonon frequency in 2D system, and the threshold breather amplitude scales as square root of the inter-chain coupling constant. Delocalizing transition of discrete vibrational breather in 2D and 3D systems of coupled nonlinear chains has an analogy with delocalizing transition for Bose-Einstein condensates in 2D and 3D optical lattices.",0705.1957v2 2007-07-11,"Comment about the ""Gravity coupled to a scalar field in extra dimensions"" paper","Wehus and Ravndal have argued that in d + 1 dimensions the general solution for gravity minimally coupled to a scalar field can not be explicitly written in Schwarzschild coordinates. We contest these objections.",0707.1671v1 2007-07-27,Summary of H1 Results on the Strong Coupling from Inclusive and Final States,"Several determinations of the strong coupling from the H1 Collaboration are reviewed.",0707.4059v1 2007-08-20,Three-State Feshbach Resonances Mediated By Second-Order Couplings,"We present an analytical study of three-state Feshbach resonances induced by second-order couplings. Such resonances arise when the scattering amplitude is modified by the interaction with a bound state that is not directly coupled to the scattering state containing incoming flux. Coupling occurs indirectly through an intermediate state. We consider two problems: (i) the intermediate state is a scattering state in a distinct open channel; (ii) the intermediate state is an off-resonant bound state in a distinct closed channel. The first problem is a model of electric-field-induced resonances in ultracold collisions of alkali metal atoms [Phys. Rev. A 75, 032709 (2007)] and the second problem is relevant for ultracold collisions of complex polyatomic molecules, chemical reaction dynamics, photoassociation of ultracold atoms, and electron - molecule scattering. Our analysis yields general expressions for the energy dependence of the T-matrix elements modified by three-state resonances and the dependence of the resonance positions and widths on coupling amplitudes for the weak-coupling limit. We show that the second problem can be generalized to describe resonances induced by indirect coupling through an arbitrary number of sequentially coupled off-resonant bound states and analyze the dependence of the resonance width on the number of the intermediate states.",0708.2638v2 2007-08-23,The $J$-matrix inverse scattering approach for coupled channels with different thresholds,"The inverse scattering method within the $J$-matrix approach to the two coupled-channel problem is discussed. We propose a generalization of the procedure to the case with different thresholds.",0708.3113v1 2007-08-27,Jahn-Teller effect versus Hund's rule coupling in C60N-,"We propose variational states for the ground state and the low-energy collective rotator excitations in negatively charged C60N- ions (N=1...5). The approach includes the linear electron-phonon coupling and the Coulomb interaction on the same level. The electron-phonon coupling is treated within the effective mode approximation (EMA) which yields the linear t_{1u} x H_g Jahn-Teller problem whereas the Coulomb interaction gives rise to Hund's rule coupling for N=2,3,4. The Hamiltonian has accidental SO(3) symmetry which allows an elegant formulation in terms of angular momenta. Trial states are constructed from coherent states and using projection operators onto angular momentum subspaces which results in good variational states for the complete parameter range. The evaluation of the corresponding energies is to a large extent analytical. We use the approach for a detailed analysis of the competition between Jahn-Teller effect and Hund's rule coupling, which determines the spin state for N=2,3,4. We calculate the low-spin/high-spin gap for N=2,3,4 as a function of the Hund's rule coupling constant J. We find that the experimentally measured gaps suggest a coupling constant in the range J=60-80meV. Using a finite value for J, we recalculate the ground state energies of the C60N- ions and find that the Jahn-Teller energy gain is partly counterbalanced by the Hund's rule coupling. In particular, the ground state energies for N=2,3,4 are almost equal.",0708.3666v1 2007-10-28,Some symmetry properties of spin currents and spin polarizations in multi-terminal mesoscopic spin-orbit coupled systems,"We study theoretically some symmetry properties of spin currents and spin polarizations in multi-terminal mesoscopic spin-orbit coupled systems. Based on a scattering wave function approach, we show rigorously that in the equilibrium state no finite spin polarizations can exist in a multi-terminal mesoscopic spin-orbit coupled system (both in the leads and in the spin-orbit coupled region) and also no finite equilibrium terminal spin currents can exist. By use of a typical two-terminal mesoscopic spin-orbit coupled system as the example, we show explicitly that the nonequilibrium terminal spin currents in a multi-terminal mesoscopic spin-orbit coupled system are non-conservative in general. This non-conservation of terminal spin currents is not caused by the use of an improper definition of spin current but is intrinsic to spin-dependent transports in mesoscopic spin-orbit coupled systems. We also show that the nonequilibrium lateral edge spin accumulation induced by a longitudinal charge current in a thin strip of \textit{finite} length of a two-dimensional electronic system with intrinsic spin-orbit coupling may be non-antisymmetric in general, which implies that some cautions may need to be taken when attributing the occurrence of nonequilibrium lateral edge spin accumulation induced by a longitudinal charge current in such a system to an intrinsic spin Hall effect.",0710.5316v1 2007-11-09,Linear response results for phonons and electron-phonon coupling in hcp Sc - spin fluctuations and implications for superconductivity,"We present a study of the electronic structure, phonon frequencies and electron-phonon coupling in hcp Sc under pressure. The electron-phonon coupling constant is found to increase steadily with pressure in the hcp phase, until the pressure reaches a value where the hcp phase becomes unstable. Calculations for the normal pressure $c/a$ ratio predict a phase change somewhere between calculated pressures of 22 and 30 GPa. The calculated frequencies for the equilibrium hcp lattice parameters are in good agreement with the inelastic neutron scattering results. From the measured value of the electronic specific heat constant and the calculated values of the Fermi level density of states and electron-phonon coupling constant, we conclude that the electron-paramagnon coupling constant in hcp Sc should be comparable to the electron-phonon coupling constant. This indicates that the spin fluctuation effects are strong enough to suppress superconductivity completely in hcp Sc. Based on estimates of the electron-paramagnon coupling constants and the calculated or estimated electron-phonon coupling constants, we argue that the hcp phase may become superconducting with a very low transition temperature immediately prior to the transition to the Sc-II phase and that the Sc-II phase should indeed be superconducting.",0711.1543v1 2007-11-19,Generation and escape of local waves from the boundary of uncoupled cardiac tissue,"We aim to understand the formation of abnormal waves of activity from myocardial regions with diminished cell-to-cell coupling. In route to this goal, we studied the behavior of a heterogeneous myocyte network in which a sharp coupling gradient was placed under conditions of increasing network automaticity. Experiments were conducted in monolayers of neonatal rat cardiomyocytes using heptanol and isoproterenol as means of altering cell-to-cell coupling and automaticity respectively. Experimental findings were explained and expanded using a modified Beeler-Reuter numerical model. The data suggests that the combination of a heterogeneous substrate, a gradient of coupling and an increase in oscillatory activity of individual cells creates a rich set of behaviors associated with self-generated spiral waves and ectopic sources. Spiral waves feature a flattened shape and a pin-unpin drift type of tip motion. These intercellular waves are action-potential based and can be visualized with either voltage or calcium transient measurements. A source/load mismatch on the interface between the boundary and well-coupled layers can lock wavefronts emanating from both ectopic sources and rotating waves within the inner layers of the coupling gradient. A numerical approach allowed us to explore how: i) the spatial distribution of cells, ii) the amplitude and dispersion of cell automaticity, iii) and the speed at which the coupling gradient moves in space, affects wave behavior, including its escape into well-coupled tissue.",0711.2945v1 2008-01-06,Higgs self coupling measurement,"A measurement of the Higgs self coupling from e+e- collisions in the International Linear Collider is presented. The impact of the detector performance in terms of $b$-tagging and particle flow is investigated.",0801.0866v1 2008-08-21,Padé expansion and nucleon-nucleon scattering in coupled channels,"We extend our Pad\'e-aided analysis of the nonperturbative renormalization of nucleon-nucleon scattering to the case of coupled channels.",0808.2850v1 2008-09-10,"Multi-Loop Results, Charm- and Bottom-Quark Masses and the Strong Coupling Constant","The impact of recent multi-loop calculations on precise determinations of charm- and bottom-quark masses and the strong coupling constant is discussed.",0809.1780v2 2009-03-30,Observation of strong coupling between a micromechanical resonator and an optical cavity field,"Achieving coherent quantum control over massive mechanical resonators is a current research goal. Nano- and micromechanical devices can be coupled to a variety of systems, for example to single electrons by electrostatic or magnetic coupling, and to photons by radiation pressure or optical dipole forces. So far, all such experiments have operated in a regime of weak coupling, in which reversible energy exchange between the mechanical device and its coupled partner is suppressed by fast decoherence of the individual systems to their local environments. Controlled quantum experiments are in principle not possible in such a regime, but instead require strong coupling. So far, this has been demonstrated only between microscopic quantum systems, such as atoms and photons (in the context of cavity quantum electrodynamics) or solid state qubits and photons. Strong coupling is an essential requirement for the preparation of mechanical quantum states, such as squeezed or entangled states, and also for using mechanical resonators in the context of quantum information processing, for example, as quantum transducers. Here we report the observation of optomechanical normal mode splitting, which provides unambiguous evidence for strong coupling of cavity photons to a mechanical resonator. This paves the way towards full quantum optical control of nano- and micromechanical devices.",0903.5293v2 2009-04-08,A note on coupled nonlinear Schrödinger systems under the effect of general nonlinearities,"We prove the existence of non-trivial solutions to a system of coupled, nonlinear, Schroedinger equations with general nonlinearity.",0904.1346v3 2009-06-08,Ultrastrong coupling regime of cavity QED with phase-biased flux qubits,"We theoretically study a circuit QED architecture based on a superconducting flux qubit directly coupled to the center conductor of a coplanar waveguide transmission-line resonator. As already shown experimentally [Abdumalikov et al. Phys. Rev. B 78, 180502 (2008)], the strong coupling regime of cavity QED can readily be achieved by optimizing the local inductance of the resonator in the vicinity of the qubit. In addition to yielding stronger coupling with respect to other proposals for flux qubit based circuit QED, this approach leads to a qubit-resonator coupling strength g which does not scale as the area of the qubit but is proportional to the total inductance shared between the resonator and the qubit. Strong coupling can thus be attained while still minimizing sensitivity to flux noise. Finally, we show that by taking advantage of the the large kinetic inductance of a Josephson junction in the center conductor of the resonator can lead to coupling energies of several tens of percent of the resonator frequency, reaching the ultrastrong coupling regime of cavity QED where the rotating-wave approximation breaks down. This should allow an on-chip implementation of the E x B Jahn-Teller model.",0906.1383v2 2009-07-07,Phase diagram of chiral quark matter: Fulde-Ferrell pairing from weak to strong coupling,"We calculate the phase diagram of two-flavor quark matter in the temperature-flavor asymmetry plane in the case where there are three competing phases: the homogeneous Bardeen-Cooper-Schrieffer (BCS) phase, the unpaired phase, and a phase with broken spatial symmetry, which is here taken to be the counterpart of the Fulde-Ferrell (FF) phase in condensed matter physics. We show that the system belongs to the universality class of paramagnetic-ferromagnetic -helical systems. We vary the coupling constant of the theory, which is obtained from integrating out the gluonic degrees of freedom. In weak coupling, the FF phase is favored at arbitrary flavor asymmetries for sufficiently low temperatures; at intermediate coupling its occupancy domain is shifted towards larger asymmetries. Strong coupling features a new regime of an inhomogeneous FF state, which we identify with a current-carrying Bose-Einstein condensate of tightly bound up and down quarks. We analyze the occupation numbers and the Cooper-pair wave function and show that when the condensate momentum is orthogonal to the particle momentum the minority component contains a blocking region (breach) around the Fermi sphere in the weak-coupling limit, which engulfs more low-momentum modes as the coupling is increased, and eventually leads to a topological change in strong coupling, where the minority Fermi sphere contains either two occupied strips or an empty sphere. For non-orthogonal momenta, the blocking region is either reduced or extinct, i.e., no topological changes are observed.",0907.1260v1 2009-08-17,The Spin-Torsion coupling and Causality for the Standard Model,"We study the influence of the spin-torsion coupling prescription and we prove the causal propagation for the fields of the standard model.",0908.2349v2 2009-11-19,Inverse Chaos Synchronization between Bidirectionally Coupled Variable Multiple Time Delay Systems,"We make first report on inverse chaos synchronization between bi-directionally non-linearly and linearly coupled variable multiple time delay Ikeda systems.The results are of certain importance in secure chaos-based communication systems.",0911.3925v1 2010-04-05,Galactic rotation curves in modified gravity with non-minimal coupling between matter and geometry,"We investigate the possibility that the behavior of the rotational velocities of test particles gravitating around galaxies can be explained in the framework of modified gravity models with non-minimal matter-geometry coupling. Generally, the dynamics of test particles around galaxies, as well as the corresponding mass deficit, is explained by postulating the existence of dark matter. The extra-terms in the gravitational field equations with geometry-matter coupling modify the equations of motion of test particles, and induce a supplementary gravitational interaction. Starting from the variational principle describing the particle motion in the presence of the non-minimal coupling, the expression of the tangential velocity of a test particle, moving in the vacuum on a stable circular orbit in a spherically symmetric geometry, is derived. The tangential velocity depends on the metric tensor components, as well as of the coupling function between matter and geometry. The Doppler velocity shifts are also obtained in terms of the coupling function. If the tangential velocity profile is known, the coupling term between matter and geometry can be obtained explicitly in an analytical form. The functional form of this function is obtained in two cases, for a constant tangential velocity, and for an empirical velocity profile obtained from astronomical observations, respectively. Therefore, these results open the possibility of directly testing the modified gravity models with non-minimal coupling between matter and geometry by using direct astronomical and astrophysical observations at the galactic or extra-galactic scale.",1004.0576v1 2010-04-27,Construction of a Microscopic Model for Yb and Tm Compounds on the Basis of a $\mib{j}$-$\mib{j}$ Coupling Scheme,"We provide a prescription to construct a microscopic model for heavy lanthanide systems such as Yb and Tm compounds by exploiting a $j$-$j$ coupling scheme. Here we consider a situation with a large spin-orbit coupling, in which $j$=5/2 sextet is fully occupied, while $j$=7/2 octet is partially occupied, where $j$ denotes total angular momentum. We evaluate crystalline electric field potentials and Coulomb interactions among the states of the $j$=7/2 octet to construct a local Hamiltonian in the $j$-$j$ coupling scheme. Then, it is found that the local $f$-electron states composed of the $j$=7/2 octet agree quite well with those of seven $f$ orbitals even for a realistic value of the spin-orbit coupling. As an example of the application of the present model, we discuss low-temperature multipole states of Yb- and Tm-based filled skutterudites by analyzing multipole susceptibility of the Anderson model in the $j$-$j$ coupling scheme with the use of a numerical renormalization group technique. From the comparison with the numerical results of the seven-orbital Anderson model, it is concluded that the multipole state is also well reproduced by the $j$-$j$ coupling model, even when we include the hybridization between conduction and $f$ electrons for the realistic value of the spin-orbit coupling. Finally, we briefly discuss future applications of the present prescription for theoretical research on heavy lanthanide compounds.",1004.4707v1 2010-06-03,Running coupling and mass anomalous dimension of SU(3) gauge theory with two flavors of symmetric-representation fermions,"We have measured the running coupling constant of SU(3) gauge theory coupled to Nf=2 flavors of symmetric representation fermions, using the Schrodinger functional scheme. Our lattice action is defined with hypercubic smeared links which, along with the larger lattice sizes, bring us closer to the continuum limit than in our previous study. We observe that the coupling runs more slowly than predicted by asymptotic freedom, but we are unable to observe fixed point behavior before encountering a first order transition to a strong coupling phase. This indicates that the infrared fixed point found with the thin-link action is a lattice artifact. The slow running of the gauge coupling permits an accurate determination of the mass anomalous dimension for this theory, which we observe to be small, gamma_m < 0.6, over the range of couplings we can reach. We also study the bulk and finite-temperature phase transitions in the strong coupling region.",1006.0707v3 2010-06-27,Bidirectionally Coupled Variable Multiple Time Delay Systems and Inverse Chaos Synchronization,"We present the first report on inverse chaos synchronization between bi-directionally non-linearly and linearly coupled variable multiple time delay Ikeda systems. The results are of certain importance in secure chaos-based communication systems.",1006.5238v1 2010-09-22,A qubit strongly-coupled to a resonant cavity: asymmetry of the spontaneous emission spectrum beyond the rotating wave approximation,"We investigate the spontaneous emission spectrum of a qubit in a lossy resonant cavity. We use neither the rotating-wave approximation nor the Markov approximation. The qubit-cavity coupling strength is varied from weak, to strong, even to lower bound of the ultra-strong. For the weak-coupling case, the spontaneous emission spectrum of the qubit is a single peak, with its location depending on the spectral density of the qubit environment. Increasing the qubit-cavity coupling increases the asymmetry (the positions about the qubit energy spacing and heights of the two peaks) of the two spontaneous emission peaks (which are related to the vacuum Rabi splitting) more. Explicitly, for a qubit in a low-frequency intrinsic bath, the height asymmetry of the splitting peaks becomes larger, when the qubit-cavity coupling strength is increased. However, for a qubit in an Ohmic bath, the height asymmetry of the spectral peaks is inverted from the same case of the low-frequency bath, when the qubit is strongly coupled to the cavity. Increasing the qubit-cavity coupling to the lower bound of the ultra-strong regime, the height asymmetry of the left and right peak heights are inverted, which is consistent with the same case of low-frequency bath, only relatively weak. Therefore, our results explicitly show how the height asymmetry in the spontaneous emission spectrum peaks depends not only on the qubit-cavity coupling, but also on the type of intrinsic noise experienced by the qubit.",1009.4366v1 2010-10-04,Probing Lorentz Symmetry with Gravitationally Coupled Matter,"Methods for obtaining additional sensitivities to Lorentz violation in the fermion sector of the Standard-Model Extension using gravitational couplings are discussed.",1010.0464v1 2010-10-19,Lorentz Symmetry and Matter-Gravity Couplings,"This proceedings contribution summarizes recent investigations of Lorentz violation in matter-gravity couplings.",1010.3990v1 2010-11-14,Running couplings and operator mixing in the gravitational corrections to coupling constants,"The use of a running coupling constant in renormalizable theories is well known, but the implementation of this idea for effective field theories with a dimensional coupling constant is in general less useful. Nevertheless there are multiple attempts to define running couplings including the effects of gravity, with varying conclusions. We sort through many of the issues involved, most particularly the idea of operator mixing and also the kinematics of crossing, using calculations in Yukawa and lambda phi^4 theory as illustrative examples. We remain in the perturbative regime. In some theories with a high permutation symmetry, such as lambda phi^4, a reasonable running coupling can be defined. However in most cases, such as Yukawa and gauge theories, a running coupling fails to correctly account for the energy dependence of the interaction strength. As a byproduct we also contrast on-shell and off-shell renormalizaton schemes and show that operators which are normally discarded, such as those that vanish by the equations of motion, are required for off-shell renormalization of effective field theories. Our results suggest that the inclusion of gravity in the running of couplings is not useful or universal in the description of physical processes.",1011.3229v2 2010-12-01,Effect of Randomness on Quantum Data Buses of Heisenberg Spin Chains,"A strongly coupled spin chain can mediate long-distance effective couplings or entanglement between remote qubits, and can be used as a quantum data bus. We study how the fidelity of a spin-1/2 Heisenberg chain as a spin bus is affected by static random exchange couplings and magnetic fields. We find that, while non-uniform exchange couplings preserve the isotropy of the qubit effective couplings, they cause the energy levels, the eigenstates, and the magnitude of the couplings to vary locally. On the other hand, random local magnetic fields lead to an avoided level crossing for the bus ground state manifold, and cause the effective qubit couplings to be anisotropic. Interestingly, the total magnetic moment of the ground state of an odd-size bus may not be parallel to the average magnetic field. Its alignment depends on both the direction of the average field and the field distribution, in contrast with the ground state of a single spin which always aligns with the applied magnetic field to minimize the Zeeman energy. Lastly, we calculate sensitivities of the spin bus to such local variations, which are potentially useful for evaluating decoherence when dynamical fluctuations in the exchange coupling or magnetic field are considered.",1012.0288v2 2011-03-19,Some Coupled Fixed Point Results on Partial Metric Spaces,"In this paper we give some coupled fixed point results for mappings satisfying different contractive conditions on complete partial metric spaces.",1103.3772v1 2011-03-26,Next-to-leading order QCD corrections to $tZ$ associated production via the flavor-changing neutral-current couplings at hadron colliders,"We present the complete next-to-leading order (NLO) QCD corrections to $tZ$ associated production induced by the model-independent $tqg$ and $tqZ$ flavor-changing neutral-current couplings at hadron colliders, respectively. Our results show that, for the $tuZ$ coupling the NLO QCD corrections can enhance the total cross sections by about 60% and 42%, and for the $tcZ$ coupling by about 51% and 43% at the Tevatron and LHC, respectively. The NLO corrections, for the $tug$ couplings, can enhance the total cross sections by about 27%, and by about 42% for the $tcg$ coupling at the LHC. We also consider the mixing effects between the $tqg$ and $tqZ$ couplings for this process, which can either be large or small depending on the values of the anomalous couplings. Besides, the NLO corrections reduce the dependence of the total cross sections on the renormalization or factorization scale significantly, which lead to increased confidence on the theoretical predictions. And we also evaluate the NLO corrections to several important kinematic distributions.",1103.5122v2 2011-04-04,Arnold diffusion in a pendulum lattice,"The main model studied in this paper is a lattice of nearest neighbors coupled pendula. For certain localized coupling we prove existence of energy transfer and estimate its speed.",1104.0580v1 2011-04-28,"Fractal properties in fundamental force coupling constants, in atomic energies, and in elementary particle masses","Using the discrete-scale invariance theory, we show that the coupling constants of fundamental forces, the atomic masses and energies, and the elementary particle masses, obey to the fractal properties.",1104.5379v1 2011-05-02,Diffractively coupled Fabry-Perot resonator with power-recycling,"We demonstrate the optical coupling of two cavities without light transmission through a substrate. Compared to a conventional coupling component, that is a partially transmissive mirror, an all-reflective coupler avoids light absorption in the substrate and therefore associated thermal problems, and even allows the use of opaque materials with possibly favourable mechanical and thermal properties. Recently, the all-reflective coupling of two cavities with a low-efficiency 3-port diffraction grating was theoretically investigated. Such a grating has an additional (a third) port. However, it was shown that the additional port does not necessarily decrease the bandwidth of the coupled cavities. Such an all-reflective scheme for cavity coupling is of interest in the field of gravitational wave detection. In such detectors light that is resonantly enhanced inside the so-called power-recycling cavity is coupled to (kilometre-scale) Fabry-Perot resonators representing the arms of a Michelson interferometer. In order to achieve a high sensitivity over a broad spectrum, the Fabry-Perot resonators need to have a high bandwidth for a given (high) power build-up. We realized such an all-reflective coupling in a table-top experiment. Our findings are in full agreement with the theoretical model incorporating the characteristics of the 3-port grating used, and therefore encourage the application of all-reflective cavity couplers in future gravitational wave detectors.",1105.0305v1 2011-06-21,Analogs of noninteger powers in general analytic QCD,"In contrast to the coupling parameter in the usual perturbative QCD (pQCD), the coupling parameter in the analytic QCD models has cuts only on the negative semiaxis of the Q^2-plane (where q^2 = -Q^2 is the momentum squared), thus reflecting correctly the analytic structure of the spacelike observables. The Minimal Analytic model (MA, named also APT) of Shirkov and Solovtsov removes the nonphysical cut (at positive Q^2) of the usual pQCD coupling and keeps the pQCD cut discontinuity of the coupling at negative Q^2 unchanged. In order to evaluate in MA the physical QCD quantities whose perturbation expansion involves noninteger powers of the pQCD coupling, a specific method of construction of MA analogs of noninteger pQCD powers was developed by Bakulev, Mikhailov and Stefanis (BMS). We present a construction, applicable now in any analytic QCD model, of analytic analogs of noninteger pQCD powers; this method generalizes the BMS approach obtained in the framework of MA. We need to know only the discontinuity function of the analytic coupling (the analog of the pQCD coupling) along its cut in order to obtain the analytic analogs of the noninteger powers of the pQCD coupling, as well as their timelike (Minkowskian) counterparts. As an illustration, we apply the method to the evaluation of the width for the Higgs decay into b+(bar b) pair.",1106.4275v3 2011-07-06,Tau Decay Determination of the QCD Coupling,"The accurate determination of the strong coupling from tau decay data is briefly reviewed. The present phenomenological status is summarized.",1107.1123v1 2011-07-13,BCS-BEC crossover in spin-orbit coupled two-dimensional Fermi gases,"The recent experimental realization of spin-orbit coupling for ultra-cold atoms has generated much interest in the physics of spin-orbit coupled degenerate Fermi gases. Although recently the BCS-BEC crossover in three-dimensional (3D) spin-orbit coupled Fermi gases has been intensively studied, the corresponding two-dimensional (2D) crossover physics has remained unexplored. In this paper, we investigate, both numerically and analytically, the BCS-BEC crossover physics in 2D degenerate Fermi gases in the presence of a Rashba type of spin-orbit coupling. We derive the mean field gap and atom number equations suitable for the 2D spin-orbit coupled Fermi gases and solve them numerically and self-consistently, from which the dependence of the ground state properties (chemical potential, superfluid pairing gap, ground state energy per atom) on the system parameters (e.g., binding energy, spin-orbit coupling strength) is obtained. Furthermore, we derive analytic expressions for these ground state quantities, which agree well with our numerical results within a broad parameter region. Such analytic expressions also agree qualitatively with previous numerical results for the 3D spin-orbit coupled Fermi gases, where analytic results are lacked. We show that with an increasing SOC strength, the chemical potential is shifted by a constant determined by the SOC strength. The superfluid pairing gap is enhanced significantly in the BCS limit for strong SOC, but only increases slightly in the BEC limit.",1107.2627v3 2011-10-22,su(3) intelligent states as coupled Su(3) coherent states,"We extend previous work on intelligent states and show how to construct su(3) intelligent states by coupling Su(3) coherent states. We also discuss some properties of the resulting states.",1110.4995v1 2012-06-26,Transport and semiclassical dynamics of coupled quantum dots interacting with a local magnetic moment,"We present a theory of magnetotransport through a system of two coupled electronic orbitals, where the electron spin interacts with a (large) local magnetic moment via an exchange interaction. For the physical realization of such a set-up we have in mind, for example, semiconductor quantum dots coupled to an ensemble of nuclear spins in the host material or molecular orbitals coupled to a local magnetic moment. Using a semiclassical approximation, we derive a set of Ehrenfest equations of motion for the electron density matrix and the mean value of the external spin (Landau equations): Due to the spin coupling they turn out to be nonlinear and, importantly, also coherences between electron states with different spin directions need to be considered. The electronic spin-polarized leads are implemented in form of a Lindblad-type dissipator in the infinite bias limit. We have solved this involved dynamical system numerically for various isotropic and anisotropic coupling schemes. For isotropic spin coupling and spin-polarized leads we study the effect of current-induced magnetization of the attached spin and compare this with a single quantum dot set-up. We further demonstrate that an anisotropic coupling can lead to a rich variety of parametric oscillations in the average current reflecting the complicated interplay between the Larmor precession of the external spin and the dissipative coherent dynamics of the electron spin.",1206.5994v2 2012-06-30,Fluid-structure interaction in blood flow capturing non-zero longitudinal structure displacement,"We present a new model and a novel loosely coupled partitioned numerical scheme modeling fluid-structure interaction (FSI) in blood flow allowing non-zero longitudinal displacement. Arterial walls are modeled by a {linearly viscoelastic, cylindrical Koiter shell model capturing both radial and longitudinal displacement}. Fluid flow is modeled by the Navier-Stokes equations for an incompressible, viscous fluid. The two are fully coupled via kinematic and dynamic coupling conditions. Our numerical scheme is based on a new modified Lie operator splitting that decouples the fluid and structure sub-problems in a way that leads to a loosely coupled scheme which is {unconditionally} stable. This was achieved by a clever use of the kinematic coupling condition at the fluid and structure sub-problems, leading to an implicit coupling between the fluid and structure velocities. The proposed scheme is a modification of the recently introduced ""kinematically coupled scheme"" for which the newly proposed modified Lie splitting significantly increases the accuracy. The performance and accuracy of the scheme were studied on a couple of instructive examples including a comparison with a monolithic scheme. It was shown that the accuracy of our scheme was comparable to that of the monolithic scheme, while our scheme retains all the main advantages of partitioned schemes, such as modularity, simple implementation, and low computational costs.",1207.0039v1 2012-07-17,Commissioning report of the MuCool 5 Tesla solenoid coupled with helium refrigerator,"This report describes results of the commissioning of the MuCool refrigeration system coupled with superconducting 5T solenoid. The commissioning was done from March 4 through April 1, 2010.",1207.4052v1 2012-07-19,Deconfinement transitions of large N QCD with chemical potential at weak and strong coupling,"We calculate the deconfinement line of transitions for large Nc QCD at finite temperature and chemical potential in two different regimes: weak coupling in the continuum, and, strong coupling on the lattice, working in the limit where Nf is of order Nc. In the first regime we extend previous weak-coupling results from one-loop perturbation theory on S^1 x S^3 to higher temperatures, where the theory reduces to a matrix model, analogous to that of Gross, Witten, and Wadia. We obtain the line of transitions that extends from the temperature-axis, where to a first approximation the transition is higher than fourth order, to the chemical potential-axis, where the transition is third order. In the second regime we use the same matrix model to obtain the deconfinement line of transitions as a function of the coupling strength and mu / T to leading order in a strong coupling expansion of lattice QCD with heavy quarks, extending previous U(Nc) results to SU(Nc). We show that in the case of zero chemical potential the result obtained for the Polyakov line from QCD on S^1 x S^3 at weak coupling reproduces the known results from the strong coupling expansion, under a simple change of parameters, which is valid for sufficiently low temperatures and chemical potentials.",1207.4605v2 2012-09-07,Theory of free space coupling to high-Q whispering gallery modes,"A theoretical study of free space coupling to high-Q whispering gallery modes both in circular and deformed microcavities are presented. In the case of a circular cavity, both analytical solutions and asymptotic formulas are derived. The coupling efficiencies at different coupling regimes for cylinder incoming wave are discussed, and the maximum efficiency is estimated for the practical Gaussian beam excitation. In the case of a deformed cavity, the coupling efficiency can be higher if the excitation beam can match the intrinsic emission well and the radiation loss can be tuned by adjusting the degree of deformation. Employing an abstract model of slightly deformed cavity, we found that the asymmetric and peak like line shapes instead of the Lorentz-shape dip are universal in transmission spectra due to multi-mode interference, and the coupling efficiency can not be estimated from the absolute depth of the dip. Our results provide guidelines for free space coupling in experiments, suggesting that the high-Q ARCs can be efficiently excited through free space which will stimulate further experiments and applications of WGMs based on free space coupling.",1209.1442v1 2012-09-26,Self-force on an arbitrarily coupled static scalar particle in a wormhole space-time,"In this paper, we consider the problem of computing the self-force and self-energy for a static scalar charge in a wormhole space-time with throat profile $r(\rho)=\sqrt{\rho^{2}+a^{2}}$ for arbitrary coupling of the field to the curvature. This calculation has previously been considered numerically by Bezerra and Khusnutdinov, while analytic results have been obtained in the special cases of minimal ($\xi=0$) coupling and conformal coupling ($\xi=1/8$ in three dimensions). We present here a closed form expression for the static Green's function for arbitrary coupling and hence we obtain an analytic expression for the self-force. The self-force depends crucially on the coupling of the field to the curvature of the space-time and hence it is useful to determine the dependence explicitly. The numerical computation can identify some qualitative aspects of this dependence such as the change in the sign of the force as it passes through the conformally coupled value, as well as the fact that the self-force diverges for $\xi=1/2$. From the closed form expression, it is straight-forward to see that there is an infinite set of values of the coupling constant for which the self-force diverges, but we also see that there is an infinite set of values for which the self-force vanishes.",1209.6088v2 2012-10-08,Local and non-local electron-phonon couplings in K3Picene and the effect of metallic screening,"We analyze the properties of electron-phonon couplings in K3Picene by exploiting a molecular orbital representation derived in the maximally localized Wannier function formalism. This allows us to go beyond the analysis done in Phys. Rev. Lett. 107, 137006 (2011), and separate not only the intra- and intermolecular phonon contributions but also the local and non-local electronic states in the electron-phonon matrix elements. Despite the molecular nature of the crystal, we find that the purely molecular contributions (Holstein-like couplings where the local deformation potential is coupled to intramolecular phonons) account for only 20% of the total electron-phonon interaction lambda. In particular, the Holstein-like contributions to lambda in K3Picene are four times smaller than those computed for an isolated neutral molecule, as they are strongly screened by the metallic bands of the doped crystal. Our findings invalidate the use of molecular electron-phonon calculations to estimate the total electron-phonon coupling in metallic picene, and possibly in other doped metallic molecular crystals. The major contribution (80%) to lambda in K3Picene comes from non-local couplings due to phonon modulated hoppings. We show that the crystal geometry together with the molecular picene structure leads to a strong 1D spatial anisotropy of the non-local couplings. Finally, based on the parameters derived from our density functional theory calculations, we propose a lattice modelization of the electron-phonon couplings in K3Picene which gives 90% of ab-initio lambda.",1210.2409v1 2012-10-15,The Wigner Strong-Coupling approach,"Mini-review on strong coupling approaches in charged soft matter, with emphasis on Wigner technique.",1210.4032v1 2012-10-16,Linear Kinetic Coupling of Firehose (KAW) and Mirror Mode,"A general gyrokinetic dispersion relation is gotten and is applied to analysis linear kinetic coupling of anisotropic firehose (or, kinetic Alfven wave) and mirror mode. Nyquist stability analysis is also given.",1210.4441v1 2012-10-28,Two-loop SQCD corrections to Higgs-quark-quark couplings in the generic MSSM,"In this article we compute the two-loop SQCD corrections to Higgs-quark-quark couplings in the generic MSSM generated by diagrams involving squarks and gluinos. We give analytic results for the two-loop contributions in the limit of vanishing external momenta for general SUSY masses valid in the MSSM with general flavour-structure. Working in the decoupling limit (M_SUSY >> v) we resum all chirally enhanced corrections (related to Higgs-quark-quark couplings) up to order \alpha_s^(n+1) tan(\beta)^n. This resummation allows for a more precise determination of the Yukawa coupling and CKM elements of the MSSM superpotential necessary for the study of Yukawa coupling unification. The knowledge of the Yukawa couplings of the MSSM superpotential in addition allows us to derive the effective Higgs-quark-quark couplings entering FCNC processes. These effective vertices can in addition be used for the calculation of Higgs decays into quarks as long as M_SUSY > M_Higgs holds. Furthermore, our calculation is also necessary for consistently including the chirally enhanced self-energies contributions into the calculation of FCNC processes in the MSSM beyond leading order. At two-loop order, we find an enhancement of the SUSY threshold corrections, induced by the quark self-energies, of approximately 9% for \mu=M_SUSY compared to the one-loop result. At the same time, the matching scale dependence of the effective Higgs-quark-quark couplings is significantly reduced.",1210.7453v2 2012-10-31,Laser profile Changes Due to Photon-Axion Induced Beam Splitting,"This paper looks at a potentially unique measurable due to photon-axion coupling in an external magnetic field. Simulations indicate that probing couplings significantly lower than seen by previous cavity experiments is possible.",1210.8319v2 2012-11-08,Quasi-Grammian Solutions of the Generalized Coupled Dispersionless Integrable System,"The standard binary Darboux transformation is investigated and is used to obtain quasi-Grammian multisoliton solutions of the generalized coupled dispersionless integrable system.",1211.1762v1 2012-11-09,Liberating Higgs couplings in supersymmetry,"In the MSSM, the Higgs couplings to down-type quarks and leptons, normalized with respect to their corresponding Standard Model values, coincide at tree-level and this degeneracy is only slightly broken at the quantum level. Motivated by the latest results of the Higgs searches at the LHC and Tevatron, we explore the possibility of disentangling these couplings from each other by considering a scenario in which supersymmetry is broken spontaneously at a low scale. In such a scenario, all the Higgs couplings, except the ones to the Z and W bosons, receive tree level corrections that depend on the MSSM soft parameters. In particular, the corrections to the Yukawa couplings depend on the A-term soft parameter for the corresponding fermion, allowing for the freedom to break their usual relations, even in the MSSM decoupling limit. We highlight the main features of this scenario in terms of a benchmark point for which the normalized Higgs coupling to the tau leptons is depleted, the coupling to photons is enhanced, while all the other Higgs couplings, including the one to the bottom quarks, are close to their corresponding SM values. We also discuss the experimental bounds arising mainly from di-tau searches and comment on the discovery/exclusion prospects at the LHC.",1211.2114v1 2013-01-12,Quantum phase transitions in a pseudogap Anderson-Holstein model,"We study a pseudogap Anderson-Holstein model of a magnetic impurity level that hybridizes with a conduction band whose density of states vanishes in power-law fashion at the Fermi energy, and couples, via its charge, to a nondispersive bosonic mode (e.g., an optical phonon). The model, which we treat using poor-man's scaling and the numerical renormalization group, exhibits quantum phase transitions of different types depending on the strength of the impurity-boson coupling. For weak impurity-boson coupling, the suppression of the density of states near the Fermi energy leads to quantum phase transitions between strong-coupling (Kondo) and local-moment phases. For sufficiently strong impurity-boson coupling, however, the bare repulsion between a pair of electrons in the impurity level becomes an effective attraction, leading to quantum phase transitions between strong-coupling (charge-Kondo) and local-charge phases. Even though the Hamiltonian exhibits different symmetries in the spin and charge sectors, the thermodynamic properties near the two types of quantum phase transition are closely related under spin-charge interchange. Moreover, the critical responses to a local magnetic field (for small impurity-boson coupling) and to an electric potential (for large impurity-boson coupling) are characterized by the same exponents, whose values place these quantum critical points in the universality class of the pseudogap Anderson model. One specific case of the pseudogap Anderson-Holstein model may be realized in a double-quantum-dot device, where the quantum phase transitions manifest themselves in the finite-temperature linear electrical conductance.",1301.2719v2 2013-01-28,Coupling dimers to CDT - conceptual issues,"Causal dynamical triangulations allows for a non perturbative approach to quantum gravity. In this article a solution for dimers coupled to CDT is presented and some of the conceptual problems that arise are reflected upon.",1301.6483v1 2013-03-25,Four Fermion Interactions in Non-Abelian Gauge Theory,"We continue our earlier study of the phase structure of a SU(2) gauge theory whose action contains additional chirally invariant four fermion interactions. Our lattice theory uses a reduced staggered fermion formalism to generate two Dirac flavors in the continuum limit. In the current study we have tried to reduce lattice spacing and taste breaking effects by using an improved fermion action incorporating stout smeared links. As in our earlier study we observe two regimes; for weak gauge coupling the chiral condensate behaves as an order parameter differentiating a phase at small four fermi coupling where the condensate vanishes from a phase at strong four fermi coupling in which chiral symmetry is spontaneously broken. This picture changes qualitatively when the gauge coupling is strong enough to cause confinement; in this case we observe a first order phase transition for some critical value of the four fermi coupling associated with a strong enhancement of the chiral condensate. We observe that this critical four fermi coupling varies monotonically with bare gauge coupling - decreasing, as expected, as the gauge coupling is increased. We have checked that these results remain stable under differing levels of smearing. They appear to rule out the appearance of new fixed points associated with chirally invariant four fermion interactions in confining non abelian gauge theories.",1303.6187v1 2013-04-03,Decay coupling constant sum rules for tetraquarks $\bm{T[(\bar{Q}q)(Q\bar{q})]}$ with broken SU(3) symmetry,"For tetraquarks of the form $T[(\bar{Q}q)(Q\bar{q})]$ we give sum rules for their decay coupling constants, taking into account the SU(3) symmetry breaking interactions to first order.",1304.1166v1 2013-04-03,Sum rules for tetraquark decay coupling constants with broken SU(3) symmetry,"We give sum rules for tetraquark decay coupling constants, taking into account the SU(3) symmetry breaking interactions to first order.",1304.1177v1 2013-05-24,Heat transport through quantum Hall edge states: Tunneling versus capacitive coupling to reservoirs,"We study the heat transport along an edge state of a two-dimensional electron gas in the quantum Hall regime, in contact to two reservoirs at different temperatures. We consider two exactly solvable models for the edge state coupled to the reservoirs. The first one corresponds to filling $\nu=1$ and tunneling coupling to the reservoirs. The second one corresponds to integer or fractional filling of the sequence $\nu=1/m$ (with $m$ odd), and capacitive coupling to the reservoirs. In both cases we solve the problem by means of non-equilibrium Green function formalism. We show that heat propagates chirally along the edge in the two setups. We identify two temperature regimes, defined by $\Delta$, the mean level spacing of the edge. At low temperatures, $T< \Delta$, finite size effects play an important role in heat transport, for both types of contacts. The nature of the contacts manifest themselves in different power laws for the thermal conductance as a function of the temperature. For capacitive couplings a highly non-universal behavior takes place, through a prefactor that depends on the length of the edge as well as on the coupling strengths and the filling fraction. For larger temperatures, $T>\Delta$, finite-size effects become irrelevant, but the heat transport strongly depends on the strength of the edge-reservoir interactions, in both cases. The thermal conductance for tunneling coupling grows linearly with $T$, whereas for the capacitive case it saturates to a value that depends on the coupling strengths and the filling factors of the edge and the contacts.",1305.5833v2 2013-05-30,Experimental Determination of the Finite-Temperature Phase Diagram of a Spin-Orbit Coupled Bose Gas,"Spin-orbit (SO) coupling has led to numerously exciting phenomena in electron systems, for instance, the recently discovered topological insulator. The synthesized SO coupling with ultracold neutral atoms opens a new avenue of quantum simulation, and gives us an opportunity to study SO coupling in bosonic systems. Indeed, SO coupling leads to many new phenomena of boson superfluidity and various condensate phases that spontaneously break different symmetries. A richer structure of symmetry breaking always results in a nontrivial finite-temperature phase diagram. While the thermodynamics of the SO coupled Bose gas at finite temperature is still unknown either in theory or experiment. In this work, we experimentally generate the SO coupling in ultracold Rb-87 gas to explore in a large temperature range and get most key features. We discover a novel phase transition between the stripe ordered phase and the magnetized phase, which is reminiscent of temperature-driven transition from the B phase to the A phase in super- fluid Helium-3 and from spin-density-wave to spin nematic transition in iron pnictide. We also observe that the magnetic phase transition and the Bose condensate transition occur simultaneously as temperature decreases. Our work determines the entire finite-temperature phase diagram of SO coupled Bose gas and further demonstrate the power of quantum simulation.",1305.7054v2 2013-05-31,A Kac CROW Delay Line,"A low-loss CROW delay line with a weak inter-resonator coupling determined by the Kac matrix is dispersionless and can be easily impedance-matched by adjusting the coupling to the input/output waveguide.",1305.7359v2 2013-10-16,Global Existence and Nonlinear Stability for the Coupled CGL Burgers Equations for Sequential flames in RN,"The present paper is devoted to the study of the global solution and nonlinear stability to the coupled complex Ginzburg Landau and Burgers equations for sequential flames",1310.4326v1 2013-10-21,Multivariate Concentration Inequalities with Size Biased Couplings,"Let $\mathbf{W}=(W_1,W_2,...,W_k)$ be a random vector with nonnegative coordinates having nonzero and finite variances. We prove concentration inequalities for $\mathbf{W}$ using size biased couplings that generalize the previous univariate results. Two applications on local dependence and counting patterns are provided.",1310.5448v1 2013-11-24,The Raman dressed spin-1 spin-orbit coupled quantum gas,"The recently realized spin-orbit coupled quantum gases (Y.-J Lin {\it et al}., Nature 471, 83-86 (2011); P. Wang {\it et al}., PRL 109, 095301 (2012); L. W. Cheuk {\it et al}., PRL 109, 095302 (2012)) mark a breakthrough in the cold atom community. In these experiments, two hyperfine states are selected from a hyperfine manifold to mimic a pseudospin-1/2 spin-orbit coupled system by the method of Raman dressing, which is applicable to both bosonic and fermionic gases. In this work, we show that the method used in these experiments can be generalized to create any large pseudospin spin-orbit coupled gas if more hyperfine states are coupled equally by the Raman lasers. As an example, we study in detail a quantum gas with three hyperfine states coupled by the Raman lasers, and show when the state-dependent energy shifts of the three states are comparable, triple-degenerate minima will appear at the bottom of the band dispersions, thus realizing a spin-1 spin-orbit coupled quantum gas. A novel feature of this three minima regime is that there can be two different kinds of stripe phases with different wavelengths, which has an interesting connection to the ferromagnetic and polar phases of spin-1 spinor BECs without spin-orbit coupling.",1311.6177v2 2013-12-11,An Indirect Model-Dependent Probe of the Higgs Self-Coupling,"The Higgs associated production cross section at an $e^+ e^-$ collider is indirectly sensitive to the Higgs self-coupling, $h^3$, at next-to-leading order (NLO). Utilizing this, a new indirect method is proposed for constraining deviations in the self-coupling below the di-Higgs production threshold in certain models. Although this indirect constraint is model-dependent, making it valid only under specific assumptions, meaningful indirect constraints on the self-coupling may be realized. Specific realistic scenarios where the indirect constraint applies are discussed and in particular it is shown that in the well-motivated class of two Higgs-doublet models there exist regions of parameter space in which the NLO effects from a modified self-coupling dominate over the LO modifications, demonstrating a concrete scenario in which large modifications of the Higgs self-coupling may be indirectly constrained using the proposed method. Other models, such as strongly coupled scenarios, are also discussed. The indirect method would give valuable constraints on deviations in the Higgs self-coupling, and would be complementary to the direct measurements possible with di-Higgs production at other colliders, providing precious additional information in the effort to unravel the properties of the Higgs boson.",1312.3322v6 2013-12-30,Radiative corrections to the Higgs couplings in the triplet model,"The feature of extended Higgs models can appear in the pattern of deviations from the Standard Model (SM) predictions in coupling constants of the SM-like Higgs boson ($h$). We can thus discriminate extended Higgs models by precisely measuring the pattern of deviations in the coupling constants of $h$, even when extra bosons are not found directly. In order to compare the theoretical predictions to the future precision data at the ILC, we must evaluate the theoretical predictions with radiative corrections in various extended Higgs models. In this talk, we give our comprehensive study for radiative corrections to various Higgs boson couplings of $h$ in the minimal Higgs triplet model (HTM). First, we define renormalization conditions in the model, and we calculate the Higgs coupling; $g\gamma\gamma, hWW, hZZ$ and $hhh$ at the one loop level. We then evaluate deviations in coupling constants of the SM-like Higgs boson from the predictions in the SM. We find that one-loop contributions to these couplings are substantial as compared to their expected measurement accuracies at the ILC. Therefore the HTM has a possibility to be distinguished from the other models by comparing the pattern of deviations in the Higgs boson couplings.",1312.7641v1 2014-02-14,(Non-)Decoupled Supersymmetric Field Theories,"We study some consequences of coupling supersymmetric theories to (super)gravity. To linear order, the couplings are determined by the energy-momentum supermultiplet. At higher orders, the couplings are determined by contact terms in correlation functions of the energy-momentum supermultiplet. We focus on the couplings of one particular field in the supergravity multiplet, the auxiliary field $M$. We discuss its linear and quadratic (seagull) couplings in various supersymmetric theories. In analogy to the local renormalization group formalism, we provide a prescription for how to fix the quadratic couplings. They generally arise at two-loops in perturbation theory. We check our prescription by explicitly computing these couplings in several examples such as mass-deformed ${\cal N}$ = 4 and in the Coulomb phase of some theories. These couplings affect the Lagrangians of rigid supersymmetric theories in curved space. In addition, our analysis leads to a transparent derivation of the phenomenon known as Anomaly Mediation. In contrast to previous approaches, we obtain both the gaugino and scalar masses of Anomaly Mediation by relying just on classical, minimal supergravity and a manifestly local and supersymmetric Wilsonian point of view. Our discussion naturally incorporates the connection between Anomaly Mediation and supersymmetric $AdS_4$ Lagrangians. This note can be read without prior familiarity with Anomaly Mediated Supersymmetry Breaking (AMSB).",1402.3385v1 2014-02-24,On Power and Load Coupling in Cellular Networks for Energy Optimization,"We consider the problem of minimization of sum transmission energy in cellular networks where coupling occurs between cells due to mutual interference. The coupling relation is characterized by the signal-to-interference-and-noise-ratio (SINR) coupling model. Both cell load and transmission power, where cell load measures the average level of resource usage in the cell, interact via the coupling model. The coupling is implicitly characterized with load and power as the variables of interest using two equivalent equations, namely, non-linear load coupling equation (NLCE) and non-linear power coupling equation (NPCE), respectively. By analyzing the NLCE and NPCE, we prove that operating at full load is optimal in minimizing sum energy, and provide an iterative power adjustment algorithm to obtain the corresponding optimal power solution with guaranteed convergence, where in each iteration a standard bisection search is employed. To obtain the algorithmic result, we use the properties of the so-called standard interference function; the proof is non-standard because the NPCE cannot even be expressed as a closed-form expression with power as the implicit variable of interest. We present numerical results illustrating the theoretical findings for a real-life and large-scale cellular network, showing the advantage of our solution compared to the conventional solution of deploying uniform power for base stations.",1402.5726v3 2014-04-04,Probing the Higgs Couplings to Photons in $h\rightarrow 4\ell$ at the LHC,"We explore the sensitivity of the Higgs decay to four leptons, the so-called golden channel, to higher dimensional loop-induced couplings of the Higgs boson to $ZZ$, $Z\gamma$, and $\gamma\gamma$, allowing for general CP mixtures. The larger standard model tree level coupling $hZ^\mu Z_\mu$ is the dominant ""background"" for the loop induced couplings. However this large background interferes with the smaller loop induced couplings, enhancing the sensitivity. We perform a maximum likelihood analysis based on analytic expressions of the fully differential decay width for $h\to 4\ell$ ($4\ell \equiv 2e2\mu, 4e, 4\mu$) including all interference effects. We find that the spectral shapes induced by Higgs couplings to photons are particularly different than the $hZ^\mu Z_\mu$ background leading to enhanced sensitivity to these couplings. We show that even if the $h\to\gamma\gamma$ and $h\to 4\ell$ rates agree with that predicted by the Standard Model, the golden channel has the potential to probe both the CP nature as well as the overall sign of the Higgs coupling to photons well before the end of high-luminosity LHC running ($\sim$3 ab$^{-1}$).",1404.1336v2 2014-07-06,Coupling Linear Sloshing with Six Degrees of Freedom Rigid Body Dynamics,"Fluid motion in tanks is usually described in space industry with the so-called Lomen hypothesis which assumes the vorticity is null in the moving frame. We establish in this contribution that this hypothesis is valid only for uniform rotational motions. We give a more general formulation of this coupling problem, with a compact formulation. We consider the mechanical modeling of a rigid body with a motion of small amplitude, containing an incompressible fluid in the linearized regime. We first establish that the fluid motion remains irrotational in a Galilean referential if it is true at the initial time. When continuity of normal velocity and pressure are prescribed on the free surface, we establish that the global coupled problem conserves an energy functional composed by three terms. We introduce the Stokes - Zhukovsky vector fields, solving Neumann problems for the Laplace operator in the fluid in order to represent the rotational rigid motion with irrotational vector fields. Then we have a good framework to consider the coupled problem between the fluid and the rigid motion. The coupling between the free surface and the ad hoc component of the velocity potential introduces a ""Neumann to Dirichlet"" operator that allows to write the coupled system in a very compact form. The final expression of a Lagrangian for the coupled system is derived and the Euler-Lagrange equations of the coupled motion are presented.",1407.1829v2 2014-07-08,A $N$-uniform quantitative Tanaka's theorem for the conservative Kac's $N$-particle system with Maxwell molecules,"This paper considers the space homogenous Boltzmann equation with Maxwell molecules and arbitrary angular distribution. Following Kac's program, emphasis is laid on the the associated conservative Kac's stochastic $N$-particle system, a Markov process with binary collisions conserving energy and total momentum. An explicit Markov coupling (a probabilistic, Markovian coupling of two copies of the process) is constructed, using simultaneous collisions, and parallel coupling of each binary random collision on the sphere of collisional directions. The euclidean distance between the two coupled systems is almost surely decreasing with respect to time, and the associated quadratic coupling creation (the time variation of the averaged squared coupling distance) is computed explicitly. Then, a family (indexed by $\delta > 0$) of $N$-uniform ''weak'' coupling / coupling creation inequalities are proven, that leads to a $N$-uniform power law trend to equilibrium of order ${\sim}_{ t \to + \infty} t^{-\delta} $, with constants depending on moments of the velocity distributions strictly greater than $2(1 + \delta)$. The case of order $4$ moment is treated explicitly, achieving Kac's program without any chaos propagation analysis. Finally, two counter-examples are suggested indicating that the method: (i) requires the dependance on $>2$-moments, and (ii) cannot provide contractivity in quadratic Wasserstein distance in any case.",1407.1965v2 2014-07-18,The ground state of two coupled Gross-Pitaevskii equations in the Thomas-Fermi limit,"We prove existence and uniqueness of a positive solution to a system of two coupled Gross-Pitaevskii equations. We give a full asymptotic expansion of this solution into powers of the semi classical parameter $\varepsilon$ in the Thomas--Fermi limit $\varepsilon\to 0$.",1407.4974v1 2014-07-19,The coupled effect of tides and stellar winds on the evolution of compact binaries,"We follow the evolution of compact binaries under the coupled effect of tides and stellar winds until the onset of Roche-lobe overflow. These binaries contain a compact object (either a black-hole, a neutron-star, or a planet) and a stellar component. We integrate the full set of tidal equations, which are based on Hut's model for tidal evolution, and we couple them with the angular momentum loss in a stellar wind. Our aim is twofold. Firstly, we wish to highlight some interesting evolutionary outcomes of the coupling. When tides are coupled with a non-massive stellar wind, one interesting outcome is that in certain types of binaries, the stellar spin tends to reach a quasi-equilibrium state, where the effect of tides and wind are counteracting each other. When tides are coupled with a massive wind, we parametrize the evolution in terms of the decoupling radius, at which the wind decouples from the star. Even for small decoupling radii this \emph{wind braking} can drive systems on the main sequence to Roche-lobe overflow that otherwise would fail to do so. Our second aim is to inspect whether simple timescale considerations are a good description of the evolution of the systems. We find that simple timescale considerations, which rely on neglecting the coupling between tides and stellar winds, do not accurately represent the true evolution of compact binaries. The outcome of the coupled evolution of the rotational and orbital elements can strongly differ from simple timescale considerations, as already pointed out by Barker & Ogilvie 2009 in the case of short-period planetary systems.",1407.5182v1 2014-07-22,Ground states and dynamics of spin-orbit-coupled Bose-Einstein condensates,"We study analytically and asymptotically as well as numerically ground states and dynamics of two-component spin-orbit-coupled Bose-Einstein condensates (BECs) modeled by the coupled Gross-Pitaevskii equations (CGPEs). In fact, due to the appearance of the spin-orbit (SO) coupling in the two-component BEC with a Raman coupling, the ground state structures and dynamical properties become very rich and complicated. For the ground states, we establish the existence and non-existence results under different parameter regimes, and obtain their limiting behaviors and/or structures with different combinations of the SO and Raman coupling strengths. For the dynamics, we show that the motion of the center-of-mass is either non-periodic or with different frequency to the trapping frequency when the external trapping potential is taken as harmonic and the initial data is chosen as a stationary state (e.g. ground state) with a shift, which is completely different from the case of a two-component BEC without the SO coupling, and obtain the semiclassical limit of the CGPEs in the linear case via the Wigner transform method. Efficient and accurate numerical methods are proposed for computing the ground states and dynamics, especially for the case of box potentials. Numerical results are reported to demonstrate the efficiency and accuracy of the numerical methods and show the rich phenomenon in the SO-coupled BECs.",1407.5815v1 2014-08-21,Thermoelectric effect in the Kondo dot side-coupled to a Majorana fermion,"We investigate the linear thermoelectric response of an interacting quantum dot side-coupled by one of two Majorana fermions (MFs) formed at the ends of a topological superconducting wire. We employ the numerical renormalization group technique to obtain the thermoelectrical conductance $L$ as well as the electrical conductance $G$ when the background temperature $T$ and the dot gate are tuned. We distinguish two transport regimes in which $L$ displays different features: the weak- $(\Gamma_{m} < T_{K})$ and strong-coupling $(\Gamma_{m} > T_{K})$ regimes, where $\Gamma_{m}$ and $T_{K}$ are the Majorana-dot coupling and the Kondo temperature, respectively. For an ideal (infinitely long) nanowire where the Majorana end states do not overlap $(\epsilon_{m} = 0)$, the thermoelectrical conductance $L$ in the weak-coupling regime exhibits a peak at $T \sim \Gamma_{m}$. This peak is ascribed to the anti-Fano resonance between the asymmetric Kondo resonance and the zero-energy MF mode. Interestingly, in the strong-coupling regime, the Kondo-induced peak in $L$ is shifted due to the MF-induced Zeeman splitting in the dot. For finite but small $\epsilon_{m} > 0$, the interference between two MFs restores the Kondo effect in the dot in a smaller energy scale $\Gamma^{\prime}_{m}$ and gives rise to an additional peak in $L$ at $T \sim \Gamma^{\prime}_{m}$, whose sign is opposite to that at $T\sim\Gamma_{m}$. In the strong-coupling regime this additional peak can cause a non-monotonic behavior of $L$ with respect to the dot gate. Finally, we examine the case in which an ordinary spin-polarized fermion is coupled to the dot and identify the fingerprint of MFs by comparing two cases.",1408.5053v1 2014-09-10,Ab initio lattice dynamics and electron-phonon coupling of Bi(111),"We present a comprehensive ab initio study of structural, electronic, lattice dynamical and electron-phonon coupling properties of the Bi(111) surface within density functional perturbation theory. Relativistic corrections due to spin-orbit coupling are consistently taken into account. As calculations are carried out in a periodic slab geometry, special attention is given to the convergence with respect to the slab thickness. Although the electronic structure of Bi(111) thin films varies significantly with thickness, we found that the lattice dynamics of Bi(111) is quite robust and appears converged already for slabs as thin as 6 bilayers. Changes of interatomic couplings are confined mostly to the first two bilayers, resulting in super-bulk modes with frequencies higher than the optic bulk spectrum, and in an enhanced density of states at lower frequencies for atoms in the first bilayer. Electronic states of the surface band related to the outer part of the hole Fermi surfaces exhibit a moderate electron-phonon coupling of about 0.45, which is larger than the coupling constant of bulk Bi. States at the inner part of the hole surface as well as those forming the electron pocket close to the zone center show much increased couplings due to transitions into bulk projected states near Gamma_bar. For these cases, the state dependent Eliashberg functions exhibit pronounced peaks at low energy and strongly deviate in shape from a Debye-like spectrum, indicating that an extraction of the coupling strength from measured electronic self-energies based on this simple model is likely to fail.",1409.3054v1 2014-09-18,The role of cellular coupling in the spontaneous generation of electrical activity in uterine tissue,"The spontaneous emergence of contraction-inducing electrical activity in the uterus at the beginning of labor remains poorly understood, partly due to the seemingly contradictory observation that isolated uterine cells are not spontaneously active. It is known, however, that the expression of gap junctions increases dramatically in the approach to parturition, which results in a significant increase in inter-cellular electrical coupling. In this paper, we build upon previous studies of the activity of electrically excitable smooth muscle cells (myocytes) and investigate the mechanism through which the coupling of these cells to electrically passive cells results in the generation of spontaneous activity in the uterus. Using a recently developed, realistic model of uterine muscle cell dynamics, we investigate a system consisting of a myocyte coupled to passive cells. We then extend our analysis to a simple two-dimensional lattice model of the tissue, with each myocyte being coupled to its neighbors, as well as to a random number of passive cells. We observe that different dynamical regimes can be observed over a range of gap junction conductances: at low coupling strength, the activity is confined to cell clusters, while the activity for high coupling may spread across the entire tissue. Additionally, we find that the system supports the spontaneous generation of spiral wave activity. Our results are both qualitatively and quantitatively consistent with observations from in vitro experiments. In particular, we demonstrate that an increase in inter-cellular electrical coupling, for realistic parameter values, strongly facilitates the appearance of spontaneous action potentials that may eventually lead to parturition.",1409.5302v1 2014-10-14,Analysis of anomalous quartic $WWZγ$ couplings in $γp$ collision at the LHC,"Gauge boson self-couplings are exactly determined by the non-Abelian gauge nature of the Standard Model (SM), thus precision measurements of these couplings at the LHC provide an important opportunity to test the gauge structure of the SM and the spontaneous symmetry breaking mechanism. It is a common way to examine the physics of anomalous quartic gauge boson couplings via effective Lagrangian method. In this work, we investigate the potential of the process $pp\rightarrow p\gamma p\rightarrow p W Z q X$ to analyze anomalous quartic $WWZ\gamma$ couplings by two different CP-violating and CP-conserving effective Lagrangians at the LHC. We calculate $95\%$ confidence level limits on the anomalous coupling parameters with various values of the integrated luminosity. Our numerical results show that the best limits obtained on the anomalous couplings $\frac{k_{0}^{W}}{\Lambda^{2}}$, $\frac{k_{c}^{W}}{\Lambda^{2}}$, $\frac{k_{2}^{m}}{\Lambda^{2}}$ and $\frac{a_{n}}{\Lambda^{2}}$ at $\sqrt{s}=14$ TeV and an integrated luminosity of $L_{int}=100$ fb$^{-1}$ are $[-1.37;\, 1.37]\times 10^{-6}$ GeV$^{-2}$, $[-1.88; \, 1.88]\times 10^{-6}$ GeV$^{-2}$, $[-6.55; \, 6.55]\times 10^{-7}$ GeV$^{-2}$ and $[-2.21;\,2.21]\times 10^{-6}$ GeV$^{-2}$, respectively. Thus, $\gamma p$ mode of photon-induced reactions at the LHC highly improves the sensitivity limits of the anomalous coupling parameters $\frac{k_{0}^{W}}{\Lambda^{2}}$, $\frac{k_{c}^{W}}{\Lambda^{2}}$, $\frac{k_{2}^{m}}{\Lambda^{2}}$ and $\frac{a_{n}}{\Lambda^{2}}$.",1410.3648v3 2014-10-28,Higgs Couplings in NonCommutative Standard Model,"We consider the Higgs and Yukawa parts of the Non-Commutative Standard Model (NCSM). We explore the NC-action to give all Feynman rules for couplings of the Higgs boson to electro-weak gauge fields and fermions.",1410.7725v1 2014-11-11,A scenario for inflationary magnetogenesis without strong coupling problem,"Cosmological magnetic fields pervade the entire universe, from small to large scales. Since they apparently extend into the intergalactic medium, it is tantalizing to believe that they have a primordial origin, possibly being produced during inflation. However, finding consistent scenarios for inflationary magnetogenesis is a challenging theoretical problem. The requirements to avoid an excessive production of electromagnetic energy, and to avoid entering a strong coupling regime characterized by large values for the electromagnetic coupling constant, typically allow one to generate only a tiny amplitude of magnetic field during inflation. We propose a scenario for building gauge-invariant models of inflationary magnetogenesis potentially free from these issues. The idea is to derivatively couple a dynamical scalar, not necessarily the inflaton, to fermionic and electromagnetic fields during the inflationary era. Such couplings give additional freedom to control the time-dependence of the electromagnetic coupling constant during inflation. This fact allows us to find conditions to avoid the strong coupling problems that affect many of the existing models of magnetogenesis. We do not need to rely on a particular inflationary set-up for developing our scenario, that might be applied to different realizations of inflation. On the other hand, specific requirements have to be imposed on the dynamics of the scalar derivatively coupled to fermions and electromagnetism, that we are able to satisfy in an explicit realization of our proposal.",1411.2803v4 2014-11-26,Collider limits on leptophilic interactions,"Leptophilic interactions can only be observed at the LHC in four-lepton final states. If these interactions are mediated by a resonance in the di-leptonic channel with renormalizable couplings, the mediator must have spin 1. We study the LHC reach for such a vector boson allowing for arbitrary couplings. We find that only couplings to muons can be probed at the LHC because lepton flavor violating couplings are constrained by rare processes, couplings to electrons by LEP and the LHC is not sensitive to final states involving taus in this case. The ILC becomes then complementary to the LHC as it will provide the best limits on $Z'$ couplings to tau leptons. A prominent example is the case of the anomaly-free $Z'$ coupling to the muon minus tau lepton number ${\rm L}_\mu - {\rm L}_\tau$. If no departure from the Standard Model is observed at the LHC, the most stringent bounds on this vector boson are provided from events with only three charged leptons plus missing energy. Masses of the order of 1 TeV can be probed at the high-luminosity phase of the LHC for $Z^\prime$ couplings of order one. Generic four-lepton operators parametrizing leptophilic interactions can be also constrained using three and four (or two at the ILC) charged-lepton samples, but the corresponding limits are marginal, if meaningful, because the resonant behavior appears to be essential for the signal to be significant.",1411.7394v2 2015-01-05,Phase Selective Quantum Eraser,"A quantum-eraser experiment is reported with photon pairs generated by two synchronously pumped parametric down converters coupled via induced coherence. The complementarity between which-source information and two-photon interference fringe visibility has been investigated by two coupled interferometers.",1501.00817v1 2015-02-03,Vacuum stability bounds on Higgs coupling deviations,"We analyze the constraints imposed by Higgs vacuum stability on models with new fermions beyond the Standard Model. We focus on the phenomenology of Higgs couplings accessible at the Large Hadron Collider. New fermions that affect Higgs couplings lead to vacuum instability of the Higgs potential. Above the scale of vacuum instability, bosonic states must stabilize the potential, implying a cut-off to the pure fermion model. Conservatively tuning the models to produce the maximal cut-off for a given Higgs coupling effect, we show that observing a deviation in the $Htt$, $H$-diphoton, or $H$-digluon coupling, larger than 20$%$, would require that new bosons exist in order to stabilize the Higgs potential below about 100 TeV. For generic parameter configurations, and unless the new fermions are made as light as they can possibly be given current experimental constraints, observing a 10$%$ deviation in any of these couplings would suggest an instability cut-off below 10-100 TeV. Similarly, if new bosons are absent up to a high scale, then a deviation in the $Hbb$ or $H\tau\tau$ coupling, larger than about 20$%$, should be accompanied by a sizable deviation in the $Zbb$ or $Z\tau\tau$ couplings that can be conclusively tested with electroweak precision measurements at planned lepton colliders.",1502.01045v1 2015-02-16,Some remarks on strongly coupled systems of convection-diffusion equations in 2D,"Almost nothing is known about the layer structure of solutions to strongly coupled systems of convection-diffusion equations in two dimensions. In some special cases we present first results.",1502.04473v1 2015-03-19,New Opportunities in $h\to 4\ell$,"The Higgs decay $h\to 4\ell$ has played an important role in discovering the Higgs and measuring its mass thanks to low background and excellent resolution. Current cuts in this channel have been optimized for Higgs discovery via the dominant tree level $ZZ$ contribution arising from electroweak symmetry breaking. Going forward, one of the primary objectives of this sensitive channel will be to probe other Higgs couplings and search for new physics on top of the tree level $ZZ$ `background'. Thanks to interference between these small couplings and the large tree level contribution to $ZZ$, the $h\to 4\ell$ decay is uniquely capable of probing the magnitude \emph{and} CP phases of the Higgs couplings to $\gamma\gamma$ and $Z\gamma$ as well as, to a lesser extent, $ZZ$ couplings arising from higher dimensional operators. With this in mind we examine how much relaxing current cuts can enhance the sensitivity while also accounting for the dominant non-Higgs continuum $q\bar{q}\to4\ell$ background. We find the largest enhancement in sensitivity for the $hZ\gamma$ couplings ($\gtrsim 100\%$) followed by $h\gamma\gamma$ ($\gtrsim 40\%$) and less so for the higher dimensional $hZZ$ couplings (a few percent). With these enhancements, we show that couplings of order Standard Model values for $h\gamma\gamma$ may optimistically be probed by end of Run-II at the LHC while for $hZ\gamma$ perhaps towards the end of a high luminosity LHC. Thus an appropriately optimized $h\to4\ell$ analysis can complement direct decays of the Higgs to on-shell $\gamma\gamma$ and $Z\gamma$ pairs giving a unique opportunity to directly access the CP properties of these couplings.",1503.05855v1 2015-05-08,Can single-reference coupled cluster theory describe static correlation?,"While restricted single-reference coupled cluster theory truncated to singles and doubles (CCSD) provides very accurate results for weakly correlated systems, it usually fails in the presence of static or strong correlation. This failure is generally attributed to the qualitative breakdown of the reference, and can accordingly be corrected by using a multi-determinant reference, including higher-body cluster operators in the ansatz, or allowing symmetry breaking in the reference. None of these solutions are ideal; multi-reference coupled cluster is not black box, including higher-body cluster operators is computationally demanding, and allowing symmetry breaking leads to the loss of good quantum numbers. It has long been recognized that quasidegeneracies can instead be treated by modifying the coupled cluster ansatz. The recently introduced pair coupled cluster doubles (pCCD) approach is one such example which avoids catastrophic failures and accurately models strong correlations in a symmetry-adapted framework. Here we generalize pCCD to a singlet-paired coupled cluster model (CCD0) intermediate between coupled cluster doubles and pCCD, yielding a method that possesses the invariances of the former and much of the stability of the latter. Moreover, CCD0 retains the full structure of coupled cluster theory, including a fermionic wave function, antisymmetric cluster amplitudes, and well-defined response equations and density matrices.",1505.01894v1 2015-05-26,Tunable frequency combs based on dual microring resonators,"In order to achieve efficient parametric frequency comb generation in microresonators, external control of coupling between the cavity and the bus waveguide is necessary. However, for passive monolithically integrated structures, the coupling gap is fixed and cannot be externally controlled, making tuning the coupling inherently challenging. We design a dual-cavity coupled microresonator structure in which tuning one ring resonance frequency induces a change in the overall cavity coupling condition. We demonstrate wide extinction tunability with high efficiency by engineering the ring coupling conditions. Additionally, we note a distinct dispersion tunability resulting from coupling two cavities of slightly different path lengths, and present a new method of modal dispersion engineering. Our fabricated devices consist of two coupled high quality factor silicon nitride microresonators, where the extinction ratio of the resonances can be controlled using integrated microheaters. Using this extinction tunability, we optimize comb generation efficiency as well as provide tunability for avoiding higher-order mode-crossings, known for degrading comb generation. The device is able to provide a 110-fold improvement in the comb generation efficiency. Finally, we demonstrate open eye diagrams using low-noise phase-locked comb lines as a wavelength-division multiplexing channel.",1505.07138v1 2015-05-27,A note on coupled focusing nonlinear Schrodinger equations,"Some focusing coupled Schrodinger equations are investigated. First, existence of ground state is obtained. Second, global and non global existence of solutions are discussed via potential-well method. Finally, strong instability of standing waves is established.",1505.07506v1 2015-05-29,On focusing coupled fourth-order nonlinear Schrodinger equations,"We investigate some focusing fourth-order coupled Schrodinger equations. Existence of ground state and global well-posedness are obtained. Moreover, the best constant of some Gagliardo-Nirenberg inequality is studied.",1505.08096v1 2015-05-29,On defocusing fourth-order coupled nonlinear Schrodinger equations,"We investigate the initial value problem for some defocusing coupled nonlinear fourth-order Schrodinger equations. Global well-posedness and scattering in the energy space are obtained.",1505.08101v1 2015-06-22,Exploring extended Higgs sectors by radiative corrections with future precision coupling measurements,"In non-minimal Higgs sectors, coupling constants of the discovered Higgs boson can deviate from the predictions in the Standard Model by effects of additional scalar bosons. The pattern of the deviations in various Higgs boson couplings largely depends on the structure of extended Higgs sectors. Therefore, we may be able to determine the true Higgs sector by fingerprinting the predictions on the Higgs boson couplings in each model with the future precision data. As the expected precision is extremely high, it is essentially important to evaluate the theory predictions as accurately as possible with radiative corrections in each model. We calculate a full set of one-loop corrections to the Higgs boson couplings in the two Higgs doublet models with a softly-broken $Z_2$ symmetry, where there are four types of Yukawa interactions. We discuss how to distinguish four types of the model by evaluating the pattern of the deviations in the Yukawa coupling constants and also the couplings with gauge bosons. In addition, we demonstrate how inner parameters in each type of the model can be extracted by the future precision measurements of these couplings at the high luminosity LHC and the International Linear Collider.",1506.06675v1 2015-10-01,The variation of the fine-structure constant from disformal couplings,"We study a theory in which the electromagnetic field is disformally coupled to a scalar field, in addition to a usual non-minimal electromagnetic coupling. We show that disformal couplings modify the expression for the fine-structure constant, alpha. As a result, the theory we consider can explain the non-zero reported variation in the evolution of alpha by purely considering disformal couplings. We also find that if matter and photons are coupled in the same way to the scalar field, disformal couplings itself do not lead to a variation of the fine-structure constant. A number of scenarios are discussed consistent with the current astrophysical, geochemical, laboratory and the cosmic microwave background radiation constraints on the cosmological evolution of alpha. The models presented are also consistent with the current type Ia supernovae constraints on the effective dark energy equation of state. We find that the Oklo bound in particular puts strong constraints on the model parameters. From our numerical results, we find that the introduction of a non-minimal electromagnetic coupling enhances the cosmological variation in alpha. Better constrained data is expected to be reported by ALMA and with the forthcoming generation of high-resolution ultra-stable spectrographs such as PEPSI, ESPRESSO, and ELT-HIRES. Furthermore, an expected increase in the sensitivity of molecular and nuclear clocks will put a more stringent constraint on current laboratory measurements.",1510.00200v1 2016-01-26,Calderón-Mityagin couples of Banach spaces related to decreasing functions,"A number of Calder\'on-Mityagin couples and relative Calder\'on-Mityagin pairs are identified among Banach function spaces defined in terms of the least decreasing majorant construction on the half line. The interpolation structure of such spaces is shown to closely parallel that of the rearrangement invariant spaces, and it is proved that a couple of these spaces is a Calder\'on-Mityagin couple if and only if the corresponding couple of rearrangement invariant spaces is a Calder\'on-Mityagin couple. Consequently, the class of all interpolation spaces for any couple of spaces of this type admits a complete description by the K-method if and only if the class of all interpolation spaces for the corresponding couple of rearrangement invariant spaces does. Analogous results are proved for spaces defined in terms of the level function construction. In the main, the conclusions for both types of spaces remain valid when Lebesgue measure on the half line is replaced by a general Borel measure on R. However, for certain measures the class of interpolation spaces of these new spaces may be degenerate, reducing the ""if and only if"" of the main results to a single implication.",1601.06861v2 2016-01-26,Cellular Automata Model of Synchronization in Coupled Oscillators,"We have developed a simple cellular automata model for nonlinearly coupled phase oscillators which can exhibit many important collective dynamical states found in other synchronizing systems. The state of our system is specified by a set of integers chosen from a finite set and defined on a lattice with periodic boundary conditions. The integers undergo coupled dynamics over discrete time steps. Depending on the values of coupling strength and range of coupling, we observed interesting collective dynamical phases namely: asynchronous, where all the integers oscillate incoherently; synchronized, where all integers oscillate coherently and also other states of intermediate and time-dependent ordering. We have adapted conventional order parameters used in coupled oscillator systems to measure the amount of synchrony in our system. We have plotted phase diagrams of these order parameters in the plane of strength of coupling and the radius of coupling. The phase diagrams reveal interesting properties about the nature of the synchronizing transition. There are partially ordered states, where there are synchronized clusters which are shown to have a power law distribution of their sizes. The power law exponent is found to be independent of the system parameters. We also discuss the possibility of chimera states in this model. A criterion of persistence of chimera is developed analytically and compared with numerical simulation.",1601.06980v4 2016-04-13,Envelope Hamiltonian for Charged-Particle Dynamics in General Linear Coupled Systems,"We report the discovery of an envelope Hamiltonian describing the charged-particle dynamics in general linear coupled lattices.",1604.03643v1 2016-04-25,Spatially Coupled Turbo-Like Codes,"In this paper, we introduce the concept of spatially coupled turbo-like codes (SC-TCs) as the spatial coupling of a number of turbo-like code ensembles. In particular, we consider the spatial coupling of Berrou et al. parallel concatenated codes (PCCs) and Benedetto et al. serially concatenated codes (SCCs). Furthermore, we propose two extensions of braided convolutional codes (BCCs), a class of turbo-like codes which have an inherent spatially coupled structure, to higher coupling memories, and show that these yield improved belief propagation (BP) thresholds as compared to the original BCC ensemble. We derive the exact density evolution (DE) equations for SC-TCs and analyze their asymptotic behavior on the binary erasure channel. We also consider the construction of families of rate-compatible SC-TC ensembles. Our numerical results show that threshold saturation of the belief propagation (BP) decoding threshold to the maximum a-posteriori threshold of the underlying uncoupled ensembles occurs for large enough coupling memory. The improvement of the BP threshold is especially significant for SCCs and BCCs, whose uncoupled ensembles suffer from a poor BP threshold. For a wide range of code rates, SC-TCs show close-to-capacity performance as the coupling memory increases. We further give a proof of threshold saturation for SC-TC ensembles with identical component encoders. In particular, we show that the DE of SC-TC ensembles with identical component encoders can be properly rewritten as a scalar recursion. This allows us to define potential functions and prove threshold saturation using the proof technique recently introduced by Yedla et al..",1604.07315v2 2016-07-02,A higher order system of some coupled nonlinear Schrödinger and Korteweg-de Vries equations,"We prove existence and multiplicity of bound and ground state solutions, under appropriate conditions on the parameters, for a bi-harmonic stationary system of coupled nonlinear Schr\""odinger--Korteweg-de Vries equations.",1607.00482v1 2017-02-03,Light-enhanced electron-phonon coupling from nonlinear electron-phonon coupling,"We investigate an exact nonequilibrium solution of a two-site electron-phonon model, where an infrared-active phonon that is nonlinearly coupled to the electrons is driven by a laser field. The time-resolved electronic spectrum shows coherence-incoherence spectral weight transfer, a clear signature of light-enhanced electron-phonon coupling. The present study is motivated by recent evidence for enhanced electron-phonon coupling in pump-probe TeraHertz and angle-resolved photoemission spectroscopy in bilayer graphene when driven near resonance with an infrared-active phonon mode [E.~Pomarico et al., Phys.~Rev.~B 95, 024304 (2017)], and by a theoretical study suggesting that transient electronic attraction arises from nonlinear electron-phonon coupling [D.~M.~Kennes et al., Nature Physics (2017), 10.1038/nphys4024]. We show that a linear scaling of light-enhanced electron-phonon coupling with the pump field intensity emerges, in accordance with a time-nonlocal self-energy based on a mean-field decoupling using quasi-classical phonon coherent states. Finally we demonstrate that this leads to enhanced double occupancies in accordance with an effective electron-electron attraction. Our results suggest that materials with strong phonon nonlinearities provide an ideal playground to achieve light-enhanced electron-phonon coupling and possibly light-induced superconductivity.",1702.00952v5 2017-08-23,D-brane Disformal Coupling and Thermal Dark Matter,"Conformal and Disformal couplings between a scalar field and matter occur naturally in general scalar-tensor theories. In D-brane models of cosmology and particle physics, these couplings originate from the D-brane action describing the dynamics of its transverse (the scalar) and longitudinal (matter) fluctuations, which are thus coupled. During the post-inflationary regime and before the onset of big-bang nucleosynthesis (BBN), these couplings can modify the expansion rate felt by matter, changing the predictions for the thermal relic abundance of dark matter particles and thus the annihilation rate required to satisfy the dark matter content today. We study the D-brane-like conformal and disformal couplings effect on the expansion rate of the universe prior to BBN and its impact on the dark matter relic abundance and annihilation rate. For a purely disformal coupling, the expansion rate is always enhanced with respect to the standard one. This gives rise to larger cross-sections when compared to the standard thermal prediction for a range of dark matter masses, which will be probed by future experiments. In a D-brane-like scenario, the scale at which the expansion rate enhancement occurs depends on the string coupling and the string scale.",1708.07153v2 2018-02-06,Manipulation of two quantum systems through their mutual interaction in presence of a radiation field,"In cavity QED, the mutual interaction between natural atomic systems in presence of a radiation field was ignored due to its negligible impact compared with the coupling to the field. The newly engineered artificial atomic systems (such as quantum dots and superconducting circuits) proposed for quantum information processing enjoy strong interaction with same type of systems or even with other types in hybrid structures, which is coherently controllable and moreover they can be efficiently coupled to radiation fields. We present an exact analytic solution for the time evolution of a composite system of two interacting two-level quantum systems coupled to a single mode radiation field, which can be realized in cavity (circuit) QED. We show how the non-classical dynamical properties of the composite system are affected and can be tuned by introducing and varying the mutual coupling between the two systems. Particularly, the collapse-revival pattern shows a splitting during the revival intervals as the coupling ratio (system-system to system-field) increases, which is a sign of an interruption in the system-radiation energy exchange process. Furthermore, the time evolution of the bipartite entanglement between the two systems is found to vary significantly depending on the coupling ratio as well as the initial state of the composite system resulting in either an oscillatory behavior or a collapse-revival like pattern. Increasing the coupling ratio enhances the entanglement, raises its oscillation average value and emphasizes the collapse-revival like pattern. However, raising the coupling ratio beyond unity increases the revival time considerably. The effect of the other system parameters such as detuning and radiation field intensity on the system dynamics has been investigated as well.",1802.01935v1 2018-04-18,Hybrid seesaw leptogenesis and TeV singlets,"The appealing feature of inverse seesaw models is that the Standard Model (SM) neutrino mass emerges from the exchange of TeV scale singlets with sizable Yukawa couplings, which can be tested at colliders. However, the tiny Majorana mass splitting between TeV singlets, introduced to accommodate small neutrino masses, is left unexplained. Moreover, we argue that these models suffer from a structural limitation that prevents a successful leptogenesis if one insists on having unsuppressed Yukawa couplings and TeV scale singlets. In this work we propose a hybrid seesaw model, where we replace the mass splitting with a coupling to a high scale seesaw module including a TeV scalar. We show that this structure achieves the goal of filling both the above gaps with couplings of order unity. The necessary structure automatically arises embedding the seesaw mechanism in composite Higgs models, but may also be enforced by new gauge symmetries in a weakly-coupled theory. Our hybrid seesaw models have distinguishing features compared to the standard high scale type-I seesaw and inverse seesaw. Firstly, they have much richer phenomenology. Indeed, they generally predict new TeV scale physics (including scalars) potentially accessible at present and future colliders, whereas weakly-coupled versions may also have astrophysical and cosmological signatures due to the presence of a light Nambu-Goldstone boson coupled to neutrinos. Secondly, our scenario features an interesting interplay between high scale and TeV scale physics in leptogenesis and enlarges the range of allowed high scale singlet masses beyond the usual $\sim 10^9-10^{ 15 }$ GeV, without large hierarchies in the Yukawa couplings nor small mass splitting among the singlets.",1804.06847v1 2010-05-18,Coupled fixed point theorems in partially ordered ε-chainable metric spaces,"In this paper, we introduce the notion of partially ordered {\epsilon}-chainable metric spaces and we derive new coupled fixed point theorems for uniformly locally contractive mappings on such spaces.",1005.3132v1 2010-05-23,N-Body Simulations for Coupled Scalar Field Cosmology,"We describe in detail the general methodology and numerical implementation of consistent N-body simulations for coupled scalar field cosmological models, including the background cosmology and the generation of initial conditions (with the different couplings to different matter species taken into account). We perform fully consistent simulations for a class of coupled scalar field models with an inverse power-law potential and negative coupling constant, for which the chameleon mechanism does not operate. We find that in such cosmological models the scalar-field potential plays a negligible role except in the background expansion, and the fifth force that is produced is proportional to gravity in magnitude, justifying the use of a rescaled gravitational constant G in some earlier N-body simulations of similar models. We study the effects of the scalar coupling on the nonlinear matter power spectra and compare with linear perturbation calculations to investigate where the nonlinear model deviates from the linear approximation. For the first time, the algorithm to identify gravitationally virialized matter halos is adapted to the scalar field cosmology, and then used to measure the mass function and study the properties of virialized halos. We find that the net effect of the scalar coupling helps produce more heavy halos in our simulation boxes and suppresses the inner (but not the outer) density profile of halos compared with those predicted by lambda-CDM, while this suppression weakens as the coupling between the scalar field and dark matter particles increases in strength.",1005.4231v1 2013-08-16,Top quark anomalous tensor couplings in the two-Higgs-doublet models,"We compute the one loop right and left anomalous tensor couplings ($g_R$ and $g_L$, respectively) for the top quark, in the aligned two-Higgs-doublet model. They are the magnetic-like couplings in the most general parameterization of the $tbW$ vertex. We find that the aligned two-Higgs doublet model, that includes as particular cases some of the most studied extensions of the Higgs sector, introduces new electroweak contributions and provides theoretical predictions that are very sensitive to both new scalar masses and the neutral scalar mixing angle. For a large area in the parameters space we obtain significant deviations in both the real and the imaginary parts of the couplings $g_R$ and $g_L$, compared to the predictions given by the electroweak sector of the Standard Model. The most important ones are those involving the imaginary part of the left coupling $g_{L}$ and the real part of the right coupling $g_R$. The real part of $g_L$ and the imaginary part of $g_R$ also show an important sensitivity to new physics scenarios. The model can also account for new CP violation effects via the introduction of complex alignment parameters that have important consequences on the values for the imaginary parts of the couplings. The top anomalous tensor couplings will be measured at the LHC and at future colliders providing a complementary insight on new physics, independent from the bounds in top decays coming from B physics and $b \rightarrow s \gamma$.",1308.3652v2 2014-03-14,Ergodicity of the Spin-Boson Model for arbitrary coupling strength,"We prove that the spin-boson system is ergodic, for arbitrary strengths of the coupling between the spin and the boson bath, provided the spin tunneling matrix element is small enough.",1403.3634v1 2014-03-24,Tavis-Cummings model beyond the rotating wave approximation: Inhomogeneous coupling,"We present the analytical solution of the Tavis-Cummings (TC) model for more than one qubit inhomogeneously coupled to a single mode radiation field beyond the rotating-wave approximation (RWA). The significant advantage of the displaced oscillator basis enables us to apply the same truncation techniques adopted in the single qubit Jaynes-Cummings (JC) model to the multiple qubits system. The derived analytical spectrum match perfectly the exact diagonalization numerical solutions of the inhomogeneous TC model in the parameter regime where the qubits transition frequencies are far off-resonance with the field frequency and the interaction strengths reach the ultra-strong coupling regime. The two-qubit TC model is quasi-exactly solvable because part of the spectra can be determined exactly in the homogeneous coupling case with two identical qubits or with symmetric(asymmetric) detuning. By means of the fidelity of quantum states we identify several nontrivial level crossing points in the same parity subspace, which implies that homogeneous coupled two-qubit TC model with $\omega_1=\omega_2$ or $\omega_1\pm\omega_2=2\omega_c$ is integrable. We further explore the time evolution of the qubit's population inversion and the entanglement behavior taking two qubits as an example. The analytical methods provide unexpectedly accurate results in describing the dynamics of the qubit in the present experimentally accessible coupling regime, showing that the collapse-revival phenomena emerge, survive, and are finally destroyed when the coupling strength increases beyond the ultra-strong coupling regime. The suggested procedure applies readily to the multiple qubits system such as the GHZ state entanglement evolution and quantum entanglement between a single photon and superconducting qubits of particular experiment interest.",1403.5893v1 2017-01-29,Coherence and entanglement of mechanical oscillators mediated by coupling to different baths,"We study the non-equilibrium dynamics of two coupled mechanical oscillators with general linear couplings to two uncorrelated thermal baths at temperatures $T_1$ and $T_2$, respectively. We obtain the complete solution of the Heisenberg-Langevin equations, which reveal a coherent mixing among the normal modes of the oscillators as a consequence of their off-diagonal couplings to the baths. Unique renormalization aspects resulting from this mixing are discussed. Diagonal and off-diagonal (coherence) correlation functions are obtained analytically in the case of strictly Ohmic baths with different couplings in the strong and weak coupling regimes. An asymptotic non-equilibrium stationary state emerges for which we obtain the complete expressions for the correlations and coherence. Remarkably the coherence survives in the high temperature, classical limit for $T_1 \neq T_2$. In the case of vanishing detuning between the oscillator normal modes both coupling to one and the same bath the coherence retains memory of the initial conditions at long time. A perturbative expansion of the early time evolution reveals that the emergence of coherence is a consequence of the entanglement between the normal modes of the oscillators \emph{mediated} by their couplings to the baths. This \emph{suggests} the survival of entanglement in the high temperature limit for different temperatures of the baths which is essentially a consequence of the non-equilibrium nature of the asymptotic stationary state. An out of equilibrium setup with small detuning and large $|T_1- T_2|$ produces non-vanishing steady-state coherence and entanglement in the high temperature limit of the baths.",1701.08759v2 2018-05-07,Understanding transient uncoupling induced synchronization through modified dynamic coupling,"An important aspect of the recently introduced transient uncoupling scheme is that it induces synchronization for large values of coupling strength at which the coupled chaotic systems resist synchronization when continu- ously coupled. However, why this is so is an open problem. To answer this question, we recall the conventional wisdom that the eigenvalues of the Jacobian of the transverse dynamics measure whether a trajectory at a phase point is locally contracting or diverging with respect to another nearby trajectory. Subsequently, we go on to highlight a lesser appreciated fact that even when, under the corresponding linearised flow, the nearby trajectory asymptotically diverges away, its distance from the reference trajectory may still be contracting for some intermediate period. We term this phenomenon transient decay in line with the phenomenon of the transient growth. Using these facts, we show that an optimal coupling region, i.e., a region of the phase space where coupling is on, should ideally be such that at any of the constituent phase point either the maximum of the real parts of the eigenvalues is negative or the magnitude of the positive maximum is lesser than that of the negative minimum. We also invent and employ modified dynamics coupling scheme---a significant improvement over the well-known dynamic coupling scheme---as a decisive tool to justify our results.",1805.02584v1 2018-05-31,Canonical Formalism of Non-Relativistic Theories Coupled to Newton-Cartan Gravity,"In this short note we perform canonical analysis of Schrodinger field and non-relativistic electrodynamics coupled to Newton-Cartan gravity. We identify physical degrees of freedom and analyze constraints structure of these theories.",1805.12392v1 2011-11-03,Gauge invariance and non-constant gauge couplings,"It is shown that space-time dependent gauge couplings do not completely break gauge invariance. We demonstrate this in various gauge theories.",1111.0758v2 2013-09-17,Markovian evolution of strongly coupled harmonic oscillators,"We investigate how to model Markovian evolution of coupled harmonic oscillators, each of them interacting with a local environment. When the coupling between the oscillators is weak, dissipation may be modeled using local Lindblad terms for each of the oscillators in the master equation, as is commonly done. When the coupling between oscillators is strong, this model may become invalid. We derive a master equation for two coupled harmonic oscillators which are subject to individual heat baths modeled by a collection of harmonic oscillators, and show that this master equation in general contains non-local Lindblad terms. We compare the resulting time evolution with that obtained for dissipation through local Lindblad terms for each individual oscillator, and show that the evolution is different in the two cases. In particular, the two descriptions give different predictions for the steady state and for the entanglement between strongly coupled oscillators. This shows that when describing strongly coupled harmonic oscillators, one must take great care in how dissipation is modeled, and that a description using local Lindblad terms may fail. This may be particularly relevant when attempting to generate entangled states of strongly coupled quantum systems.",1309.4366v2 2013-09-18,Control problems for weakly coupled systems with memory,"We investigate control problems for wave-Petrovsky coupled systems in the presence of memory terms. By writing the solutions as Fourier series, we are able to prove Ingham type estimates, and hence reachability results. Our findings have applications in viscoelasticity theory and linear acoustic theory.",1309.4600v1 2014-05-13,A monolithic multi-time-step computational framework for first-order transient systems with disparate scales,"Developing robust simulation tools for problems involving multiple mathematical scales has been a subject of great interest in computational mathematics and engineering. A desirable feature to have in a numerical formulation for multiscale transient problems is to be able to employ different time-steps (multi-time-step coupling), and different time integrators and different numerical formulations (mixed methods) in different regions of the computational domain. We present two new monolithic multi-time-step mixed coupling methods for first-order transient systems. We shall employ unsteady advection-diffusion-reaction equation with linear decay as the model problem, which offers several unique challenges in terms of non-self-adjoint spatial operator and rich features in the solutions. We shall employ the dual Schur domain decomposition technique to handle the decomposition of domain into subdomains. Two different methods of enforcing compatibility along the subdomain interface will be used in the time discrete setting. A systematic theoretical analysis (which includes numerical stability, influence of perturbations, bounds on drift along the subdomain interface) will be performed. The first coupling method ensures that there is no drift along the subdomain interface but does not facilitate explicit/implicit coupling. The second coupling method allows explicit/implicit coupling with controlled (but non-zero) drift in the solution along the subdomain interface. Several canonical problems will be solved to numerically verify the theoretical predictions, and to illustrate the overall performance of the proposed coupling methods. Finally, we shall illustrate the robustness of the proposed coupling methods using a multi-time-step transient simulation of a fast bimolecular advective-diffusive-reactive system.",1405.3230v2 2014-06-05,Two mutually loss-coupled lasers featuring astable multivibrator,"Self-sustained antiphase relaxation oscillations of high amplitude are shown to be possible in a system of two single-mode semiconductor lasers strongly coupled through their cavities.",1406.1268v1 2014-06-05,A note on the Lee-Yang singularity coupled to 2d quantum gravity,"We show how to obtain the critical exponent of magnetization in the Lee-Yang edge singularity model coupled to two-dimensional quantum gravity.",1406.1458v1 2014-06-17,First-principles study of the electronic structure of CdS/ZnSe coupled quantum dots,"We have studied the electronic structure of CdS/ZnSe coupled quantum dot, a novel heterostructure at the nano-scale. Our calculations reveal CdS/ZnSe coupled quantum dots to be of type-II in nature where the anion-p states play an important role in deciding the band offset for the highest occupied molecular orbitals (HOMO). We show that the offsets of HOMO as well as the lowest unoccupied molecular orbitals (LUMO) can be tuned by changing the sizes of the components of the coupled quantum dot, thereby providing an additional control parameter to tune the band gap and the optical properties. Our investigations also suggest that formation of alloy near the interface has very little influence on the band offsets, although it affects the spatial localization of the quantum states from the individual components. Comparing the influence of strain on coupled quantum dots and core/shell nanowires, we find strain practically has no role in the electronic structure of coupled quantum dots as the small effective area of the interface in a coupled quantum dot helps a large part of the structure remain free from any substantial strain. We argue that in contrast to core-shell nanowires, quantum confinement is the key parameter that controls the electronic properties of coupled quantum dot and should therefore be an ideal candidate for the design of a quantum device.",1406.4487v1 2014-06-24,Algebro-geometric solution of the coupled Burgers equation,"We derive theta function representation of algebro-geometric solution of a Coupled Burgers equation which the second nonlinear evolution equation in a hierarchy. We also derive the algebro-geometric characters of the meromorphic function {\phi} and the Baker-Akhiezer vector {\Psi}.",1406.6233v1 2016-05-09,Impacts of the tensor couplings of $ω$ and $ρ$ mesons and Coulomb exchange terms on super-heavy nuclei and their relation to symmetry energy,"We have studied the effects of tensor coupling of $\omega$ and $\rho$ meson terms, Coulomb exchange term in local density approximation and various isoscalar-isovector coupling terms of relativistic mean field model on the properties of nuclear matter, finite nuclei, and super-heavy nuclei. We found that for the same fixed value of symmetry energy $J$ or its slope $L$ the presence of tensor coupling of $\omega$ and $\rho$ meson terms and Coulomb exchange term yields thicker neutron skin thickness of $^{208}$Pb. We also found that the roles of tensor coupling of $\omega$ and $\rho$ meson terms, Coulomb exchange term in local density approximation and various isoscalar-isovector coupling terms on the bulk properties of finite nuclei varies depending on the corresponding nucleus mass. However, on average, tensor coupling terms play a significant role in predicting the bulk properties of finite nuclei in a quite wide mass range especially in binding energies. We also observed that for some particular nuclei, the corresponding experimental data of binding energies is rather less compatible with the presence of Coulomb exchange term in local density approximation and they tend to disfavor the presence of isoscalar-isovector coupling term with too high $\Lambda$ value. Furthermore, we have found that these terms influence the detail properties of $^{292}$120 super-heavy nucleus such as binding energies, the magnitude of two nucleon gaps, single particle spectra, neutron densities, neutron skin thicknesses and mean square charge radii. However, the shell closure predictions of $^{208}$Pb and $^{292}$120 nuclei is not affected by the presence of these terms.",1605.02399v1 2016-05-10,Directly characterizing the relative strength and momentum dependence of electron-phonon coupling using resonant inelastic x-ray scattering,"The coupling between lattice and charge degrees of freedom in condensed matter materials is ubiquitous and can often result in interesting properties and ordered phases, including conventional superconductivity, charge density wave order, and metal-insulator transitions. Angle-resolved photoemission spectroscopy and both neutron and non-resonant x-ray scattering serve as effective probes for determining the behavior of appropriate, individual degrees of freedom -- the electronic structure and lattice excitation, or phonon dispersion, respectively. However, each provides less direct information about the mutual coupling between the degrees of freedom, usual through self-energy effects, which tend to renormalize and broaden spectral features precisely where the coupling is strong, impacting ones ability to quantitively characterize the coupling. Here we demonstrate that resonant inelastic x-ray scattering, or RIXS, can be an effective tool to directly determine the relative strength and momentum dependence of the electron-phonon coupling in condensed matter systems. Using a diagrammatic approach for an 8-band model of copper oxides, we study the contributions from the lowest order diagrams to the full RIXS intensity for a realistic scattering geometry, accounting for matrix element effects in the scattering cross-section as well as the momentum dependence of the electron-phonon coupling vertex. A detailed examination of these maps offers a unique perspective into the characteristics of electron-phonon coupling, which complements both neutron and non-resonant x-ray scattering, as well as Raman and infrared conductivity.",1605.03129v1 2016-05-24,Transcriptional Similarity in Couples Reveals the Impact of Shared Environment and Lifestyle on Gene Regulation through Modified Cytosines,"Gene expression is a complex and quantitative trait that is influenced by both genetic and non-genetic regulators including environmental factors. Evaluating the contribution of environment to gene expression regulation and identifying which genes are more likely to be influenced by environmental factors are important for understanding human complex traits. We hypothesize that by living together as couples, there can be commonly co-regulated genes that may reflect the shared living environment (e.g., diet, indoor air pollutants, behavioral lifestyle). The lymphoblastoid cell lines (LCLs) derived from unrelated couples of African ancestry (YRI, Yoruba people from Ibadan, Nigeria) from the International HapMap Project provided a unique model for us to characterize gene expression pattern in couples by comparing gene expression levels between husbands and wives. Strikingly, 778 genes were found to show much smaller variances in couples than random pairs of individuals at a false discovery rate (FDR) of 5%. Since genetic variation between unrelated family members in a general population is expected to be the same assuming a random-mating society, non-genetic factors (e.g., epigenetic systems) are more likely to be the mediators for the observed transcriptional similarity in couples. We thus evaluated the contribution of modified cytosines to those genes showing transcriptional similarity in couples as well as the relationships these CpG sites with other gene regulatory elements, such as transcription factor binding sites (TFBS). Our findings suggested that transcriptional similarity in couples likely reflected shared common environment partially mediated through cytosine modifications.",1605.07488v1 2017-06-01,Thermoelectrics in Coulomb-coupled quantum dots: Cotunneling and energy-dependent lead couplings,"We study thermoelectric effects in Coulomb-coupled quantum-dot (CCQD) systems beyond lowest-order tunneling processes and the often applied wide-band approximation. To this end, we present a master-equation (ME) approach based on a perturbative $T$-matrix calculation of the charge and heat tunneling rates and transport currents. Applying the method to transport through a non-interacting single-level QD, we demonstrate excellent agreement with the Landauer-B{\""u}ttiker theory when higher-order (cotunneling) processes are included in the ME. Next, we study the effect of cotunneling and energy-dependent lead couplings on the heat currents in a system of two Coulomb-coupled QDs. Overall, we find that cotunneling processes (i) dominate the heat currents at low temperature and bias, and (ii) give rise to a pronounced reduction of the cooling power achievable with the recently demonstrated Maxwell's demon cooling mechanism. Furthermore, we demonstrate that the cooling power can be boosted significantly by carefully engineering the energy dependence of the lead couplings to filter out undesired transport processes. Our findings emphasize the importance of considering higher-order cotunneling processes as well as the advantage of engineered energy-dependent lead couplings in the optimization of the thermoelectric performance of Coulomb-coupled QD systems.",1706.00461v1 2017-06-03,Lorden's inequality and coupling method for backward renewal process,"We give a scheme of using the coupling method to obtain strong bounds for the convergence rate of the distribution of the backward renewal process in the total variation distance. This scheme can be applied to a wide class of regenerative processes in queuing theory.",1706.00922v1 2017-10-09,Tunable superconducting critical temperature in ballistic hybrid structures with strong spin-orbit coupling,"We present a theoretical description and numerical simulations of the superconducting transition in hybrid structures including strong spin-orbit interactions. The spin-orbit coupling is taken to be of Rashba type for concreteness, and we allow for an arbitrary magnitude of the spin-orbit strength as well as an arbitrary thickness of the spin-orbit coupled layer. This allows us to make contact with the experimentally relevant case of enhanced interfacial spin-orbit coupling via atomically thin heavy metal layers. We consider both interfacial spin-orbit coupling induced by inversion asymmetry in an S/F-junction, as well as in-plane spin-orbit coupling in the ferromagnetic region of an S/F/S- and an S/F-structure. Both the pair amplitudes, local density of states and critical temperature show dependency on the Rashba strength and, importantly, the orientation of the exchange field. In general, spin-orbit coupling increases the critical temperature of a proximity system where a magnetic field is present, and enhances the superconducting gap in the density of states. We perform a theoretical derivation which explains these results by the appearance of long-ranged singlet correlations. Our results suggest that $T_c$ in ballistic spin-orbit coupled superconducting structures may be tuned by using only a single ferromagnetic layer.",1710.03228v2 2017-12-14,The strong coupling: a theoretical perspective,"This contribution to the volume ""From My Vast Repertoire - The Legacy of Guido Altarelli"" discusses the state of our knowledge of the strong coupling.",1712.05165v2 2018-09-21,General coupled semirings of residuated lattices,"Di Nola and Gerla showed that MV-algebras and coupled semirings are in a natural one-to-one correspondence. We generalize this correspondence to residuated lattices satisfying the double negation law.",1809.08176v1 2019-09-18,Dzyaloshinskii-Moriya coupling in 3d insulators,"We present an overview of the microscopic theory of the Dzyaloshinskii-Moriya (DM) coupling in strongly correlated 3d compounds. Most attention in the paper centers around the derivation of the Dzyaloshinskii vector, its value, orientation, and sense (sign) under different types of the (super)exchange interaction and crystal field. We consider both the Moriya mechanism of the antisymmetric interaction and novel contributions, in particular, that of spin-orbital coupling on the intermediate ligand ions. We have predicted a novel magnetic phenomenon, {\it weak ferrimagnetism} in mixed weak ferromagnets with competing signs of the Dzyaloshinskii vectors. We revisit a problem of the DM coupling for a single bond in cuprates specifying the local spin-orbital contributions to Dzyaloshinskii vector focusing on the oxygen term. We predict a novel puzzling effect of the on-site staggered spin polarization to be a result of the on-site spin-orbital coupling and the the cation-ligand spin density transfer. The intermediate ligand NMR measurements are shown to be an effective tool to inspect the effects of the DM coupling in an external magnetic field. We predict the effect of a $strong$ oxygen weak antiferromagnetism in edge-shared CuO$_2$ chains due to uncompensated oxygen Dzyaloshinskii vectors. We revisit the effects of symmetric spin anisotropy directly induced by the DM coupling. A critical analysis will be given of different approaches to exchange-relativistic coupling based on the cluster and the DFT based calculations. Theoretical results are applied to different classes of 3d compounds from conventional weak ferromagnets ($\alpha$-Fe$_2$O$_3$, FeBO$_3$, FeF$_3$, RFeO$_3$, RCrO$_3$,.. ) to unconventional systems such as weak ferrimagnets (e.g., RFe$_{1-x}$Cr$_x$O$_3$), helimagnets (e.g., CsCuCl$_3$), and parent cuprates (La$_2$CuO$_4$,...).",1909.08342v1 2020-12-02,Using Noise to Augment Synchronization among Oscillators,"Noise is expected to play an important role in the dynamics of analog systems such as coupled oscillators which have recently been explored as a hardware platform for application in computing. In this work, we experimentally investigate the effect of noise on the synchronization of relaxation oscillators and their computational properties. Specifically, in contrast to its typically expected adverse effect, we first demonstrate that a common white noise input induces global frequency synchronization among uncoupled oscillators. Experiments show that the minimum noise voltage required to induce synchronization increases linearly with the amplitude of the oscillator output whereas it decreases with increasing number of oscillators. Further, our work reveals that in a coupled system of oscillators - relevant to solving computational problems such as graph coloring, the injection of white noise helps reduce the minimum required capacitive coupling strength. With the injection of noise, the coupled system demonstrates frequency synchronization along with the desired phase-based computational properties at 5x lower coupling strength than that required when no external noise is introduced. Consequently, this can reduce the footprint of the coupling element and the corresponding area-intensive coupling architecture. Our work shows that noise can be utilized as an effective knob to optimize the implementation of coupled oscillator-based computing platforms.",2012.01355v2 2012-05-16,Twiss Parameters of Coupled Particle Beams with Equal Eigenemittances,"We show that the 1D Courant-Snyder theory can be considered as a partial case of the multidimensional theory of coupled particle beams with equal eigenemittances.",1205.3589v1 2017-05-20,Regeneration of $K^0_{S}$ mesons,"It is shown that in the previous calculations of $K^0_{S}$ regeneration the noncoupled equations of motion have been considered instead of coupled one. We present the calculations based on the exact solution of coupled equations of motion and perturbation theory. The results differ radically from the previous ones.",1705.08289v1 2018-03-07,"Rapidly forming, slowly evolving, spatial patterns from quasi-cycle Mexican Hat coupling","A lattice-indexed family of stochastic processes has quasi-cycle oscillations if its otherwise-damped oscillations are sustained by noise. Such a family performs the reaction part of a discrete stochastic reaction-diffusion system when we insert a local Mexican Hat-type, difference of Gaussians, coupling on a one-dimensional and on a two-dimensional lattice. Quasi-cycles are a proposed mechanism for the production of neural oscillations, and Mexican Hat coupling is ubiquitous in the brain. Thus this combination might provide insight into the function of neural oscillations in the brain. Importantly, we study this system only in the transient case, on time intervals before saturation occurs. In one dimension, for weak coupling, we find that the phases of the coupled quasi-cycles synchronize (establish a relatively constant relationship, or phase lock) rapidly at coupling strengths lower than those required to produce spatial patterns of their amplitudes. In two dimensions the amplitude patterns form more quickly, but there remain parameter regimes in which phase synchronization patterns form without being accompanied by clear amplitude patterns. At higher coupling strengths we find patterns both of phase synchronization and of amplitude (resembling Turing patterns) corresponding to the patterns of phase synchronization. Specific properties of these patterns are controlled by the parameters of the reaction and of the Mexican Hat coupling.",1803.02917v2 2018-03-22,Nonmonotonic particle-size-dependence of magnetoelectric coupling in strained nanosized particles of BiFeO$_3$,"Using high resolution powder x-ray and neutron diffraction experiments, we determined the off-centered displacement of the ions within a unit cell and magnetoelectric coupling in nanoscale BiFeO$_3$ ($\approx$20-200 nm). We found that both the off-centered displacement of the ions and magnetoelectric coupling exhibit nonmonotonic variation with particle size. They increase as the particle size reduces from bulk and reach maximum around 30 nm. With further decrease in particle size, they decrease precipitously. The magnetoelectric coupling is determined by the anomaly in off-centering of ions around the magnetic transition temperature ($T_N$). The ions, in fact, exhibit large anomalous displacement around the $T_N$ which is analyzed using group theoretical approach. It underlies the nonmonotonic particle-size-dependence of off-centre displacement of ions and magnetoelectric coupling. The nonmonotonic variation of magnetoelectric coupling with particle size is further verified by direct electrical measurement of remanent ferroelectric hysteresis loops at room temperature under zero and $\sim$20 kOe magnetic field. Competition between enhanced lattice strain and compressive pressure appears to be causing the nonmonotonic particle-size-dependence of off-centre displacement while coupling between piezo and magnetostriction leads to nonmonotonicity in the variation of magnetoelectric coupling.",1803.08322v1 2018-03-26,Non-minimally Coupled Pseudoscalar Inflaton,"We consider a scenario in which the inflaton $\phi$ is a pseudoscalar field non-minimally coupled to gravity through a term of the form ${\cal X} R \phi^2$. The pseudoscalar is also coupled to a $U(1)$ gauge field (or an ensemble of ${\cal N}$ gauge fields) through an axial coupling of the form $\phi F \tilde{F}$. After M. M. Anber and L. Sorbo, Phys. Rev. D 81, 043534 (2010), Ref. [1], it is well known that this axial coupling leads to a production of gauge particles which acts as a friction term in the dynamics of the inflaton, producing a slow-roll regime even in presence of a steep potential. A remarkable result in this scenario, is that the spectrum of the chiral gravitational waves sourced by the scalar-gauge field interplay can be enhanced due to the non-minimal coupling with gravity, leading to measurable signatures, while maintaining agreement with current observational constraints on $n_s$ and $r$. The inclusion of non-minimal coupling could be helpful to alleviate tensions with non-Gaussianity bounds in models including axial couplings.",1803.09743v2 2018-07-11,Strong coupling of a single photon to a magnetic vortex,"Strong light-matter coupling is a necessary condition for exchanging information in quantum information protocols. It is used to couple different qubits (matter) via a quantum bus (photons) or to communicate different type of excitations, e.g. transducing between light and phonons or magnons. An unexplored, so far, interface is the coupling between light and topologically protected particle like excitations as magnetic domain walls, skyrmions or vortices. Here, we show theoretically that a single photon living in a superconducting cavity can be coupled strongly to the gyrotropic mode of a magnetic vortex in a nanodisc. We combine numerical and analytical calculations for a superconducting coplanar waveguide resonator and different realizations of the nanodisc (materials and sizes). We show that, for enhancing the coupling, constrictions fabricated in the resonator are beneficial, allowing to reach the strong coupling in CoFe discs of radius $200-400$ nm having resonance frequencies of few GHz. The strong coupling regime permits to exchange coherently a single photon and quanta of vortex excitations. Thus, our calculations show that the device proposed here serves as a transducer between photons and gyrating vortices, opening the way to complement superconducting qubits with topologically protected spin-excitations like vortices or skyrmions. We finish by discussing potential applications in quantum data processing based on the exploitation of the vortex as a short-wavelength magnon emitter.",1807.04075v2 2018-07-11,"Magnetodielectric coupling in a Ru-based 6H-perovskite, Ba3NdRu2O9","A large spin-orbit coupling is a way to control strong magnetodielectric (MD) coupling in a higher d-orbital materials. However reports are rare on such compounds due to often leaky conductive behavior. Here, we demonstrate MD coupling in a Ru-based 6H-perovskite system, Ba3NdRu2O9. The rare-earth ion in a 6H-perovskite makes the system insulating enough to carry out MD investigation. The compound is ferromagnetically ordered below 24 K (TC), followed by another magnetic feature at T~ 17 K (T2). The dielectric constant clearly traces the magnetic ordering, manifesting a peak at the onset of TC, which is suppressed by the application of an external magnetic field (H). The results indicate the presence of MD coupling in this compound, which is further confirmed by the H-dependence of the dielectric constant. Interestingly, a cross-over of the sign of MD coupling is observed at T ~ T2. We conclude that two different mechanism controls the MD coupling which yields positive and negative coupling, respectively. Both mechanisms are competing as a function of temperature and magnetic field. This brings us a step closer to design and control the magnetodielectric effect in 6H-perovskites containing higher d-orbital elements.",1807.04231v2 2018-07-13,Standing waves for a Schrödinger-Chern-Simons-Higgs system,"We consider a system arising from a nonrelativistic Chern-Simon-Higgs model, in which a charged field is coupled with a gauge field. We prove an existence result for small coupling constants.",1807.05168v1 2018-07-19,Three-boson spectrum in the presence of 1D spin-orbit coupling: Efimov's generalized radial scaling law,"Spin-orbit coupled cold atom systems, governed by Hamiltonians that contain quadratic kinetic energy terms typical for a particle's motion in the usual Schr\""odinger equation and linear kinetic energy terms typical for a particle's motion in the usual Dirac equation, have attracted a great deal of attention recently since they provide an alternative route for realizing fractional quantum Hall physics, topological insulators, and spintronics physics. The present work focuses on the three-boson system in the presence of 1D spin-orbit coupling, which is most relevant to ongoing cold atom experiments. In the absence of spin-orbit coupling terms, the three-boson system exibits the Efimov effect: the entire energy spectrum is uniquely determined by the $s$-wave scattering length and a single three-body parameter, i.e., using one of the energy levels as input, the other energy levels can be obtained via Efimov's radial scaling law, which is intimately tied to a discrete scaling symmetry. It is demonstrated that the discrete scaling symmetry persists in the presence of 1D spin-orbit coupling, implying the validity of a generalized radial scaling law in five-dimensional space. The dependence of the energy levels on the scattering length, spin-orbit coupling parameters, and center-of-mass momentum is discussed. It is conjectured that three-body systems with other types of spin-orbit coupling terms are also governed by generalized radial scaling laws, provided the system exhibits the Efimov effect in the absence of spin-orbit coupling.",1807.07653v1 2018-07-31,Synchronization patterns in LIF Neural Networks: Merging Nonlocal and Diagonal Connectivity,"The effects of nonlocal and reflecting connectivities have been previously investigated in coupled Leaky Integrate-and-Fire (LIF) elements, which assimilate the exchange of electrical signals between neurons. In this work we investigate the effect of diagonal coupling inspired by findings in brain neuron connectivity. Multi-chimera states are reported both for the simple diagonal and combined nonlocal-diagonal connectivities and we determine the range of optimal parameter regions where chimera states appear. Overall, the measures of coherence indicate that as the coupling range increases (below all-to-all coupling) the emergence of chimera states is favoured and the mean phase velocity deviations between coherent and incoherent regions become more prominent. A number of novel synchronization phenomena are induced as a result of the combined connectivity. We record that for coupling strengths $\sigma < 1$ the synchronous regions have mean phase velocities lower than the asynchronous, while the opposite holds for $\sigma > 1$. In the intermediate regime, $\sigma \sim 1$, the oscillators have common mean phase velocity (i.e., are frequency-locked) but different phases (i.e., they are phase-asynchronous). Solitary states are recorded for small values of the coupling strength, which grow into chimera states as the coupling strength increases.We determine parameter values where the combined effects of nonlocal-diagonal coupling generate chimera states with two different levels of synchronous domains mediated by asynchronous regions.",1807.11843v2 2018-12-12,Nonminimally coupled Weyl gravity,"Weyl gravity in the presence of a non-minimal matter-curvature coupling is presented. Some properties arising from the non-metricity give rise to a second order theory whose vacuum is compatible with a cosmological constant, under conditions on the vector field.",1812.04976v1 2019-02-11,Divergence of the effective mass of a polaron in the strong coupling limit,"We consider the Fr\""ohlich model of a polaron, and show that its effective mass diverges in the strong coupling limit.",1902.04025v1 2019-03-08,Line of fixed points in a bosonic tensor model,"We consider the $O(N)^3$ tensor model of Klebanov and Tarnopolsky \cite{Klebanov:2016xxf} in $d<4$ with a free covariance modified to fit the infrared conformal scaling. We study the renormalization group flow of the model using a Wilsonian approach valid in any $d$ (notably we do not require $d=4-\epsilon$ with small $\epsilon$). At large $N$, the tetrahedral coupling has a finite flow, hence it becomes a free parameter. The remaining flow can be parameterized by two couplings which do not mix. We show that, at leading order in $1/N$ but non perturbatively in the couplings, the beta functions stop at quadratic order in the pillow and double-trace couplings. We find four fixed points which depend parametrically on the tetrahedral coupling. For purely imaginary values of the latter we identify a real and \emph{infrared attractive} fixed point. We remark that an imaginary tetrahedral coupling is in fact natural from the onset as the tetrahedral invariant does not have any positivity property, and moreover in the large-$N$ limit beta functions depend on the square of the tetrahedral coupling, thus they remain real, as long as the other couplings stay real.",1903.03578v3 2019-03-23,An extension of a Liapunov approach to the stabilization of second order coupled systems,"This paper deals with the convergence to 0 of the energy of the solutions of a second order linear coupled system. In order to obtain the energy decay, we exhibit a Liapunov function.",1903.09810v1 2019-03-29,Forces on a Clifford bundle,"In a companion article, the Clifford bundle over spacetime was used as a geometric framework for obtaining coupled Dirac and Einstein equations. Other forces may be incorporated using minimal coupling. Here the fundamental forces that are allowed within this framework are explicitly enumerated.",1903.12367v1 2019-03-31,Reduction of Couplings and its application in Particle Physics,"The idea of reduction of couplings in renormalizable theories will be presented and then will be applied in Particle Physics models. Reduced couplings appeared as functions of a primary one, compatible with the renormalization group equation and thus solutions of a specific set of ordinary differential equations. If these functions have the form of power series the respective theories resemble standard renormalizable ones and thus widen considerably the area covered until then by symmetries as a tool for constraining the number of couplings consistently. Still on the more abstract level reducing couplings enabled one to construct theories with beta-functions vanishing to all orders of perturbation theory. Reduction of couplings became physics-wise truly interesting and phenomenologically important when applied to the standard model and its possible extensions. In particular in the context of supersymmetric theories it became the most powerful tool known today once it was learned how to apply it also to couplings having dimension of mass and to mass parameters. Technically this all relies on the basic property that reducing couplings is a renormalization scheme independent procedure. Predictions of top and Higgs mass prior to their experimental finding highlight the fundamental physical significance of this notion.",1904.00410v1 2019-11-20,Anti-crossing properties of strong coupling system of silver nanoparticle dimers coated with thin dye molecular films analyzed by classical electromagnetism,"The evidence of strong coupling between plasmons and molecular excitons for plasmonic nanoparticle (NP) dimers exhibiting ultra-sensitive surface enhanced resonant Raman scattering is the observation of anti-crossing in the coupled resonance. However, it is not easy to experimentally tune plasmon resonance of such dimers for the observation. In this work, we theoretically investigate the anti-crossing properties of the dimers coated by the thin dye films with thicknesses greater than 0.1 nm and gap distances larger than 1.2 nm according to the principles of classical electromagnetism. The plasmon resonance spectra of these dimers are strongly affected by their coupling with the exciton resonance of dye molecules. A comparison of the film thickness dependences of dimer spectral changes with those of silver ellipsoidal NPs indicates that the dipole plasmons localized in the dimer gap are coupled with molecular excitons of the film much stronger than the dipole plasmons of ellipsoidal NPs. Furthermore, the anti-crossing of coupled resonances is investigated while tuning plasmon resonance by changing the morphology and refractive index of the surrounding medium. The spectral changes observed for ellipsoidal NPs clearly exhibit anti-crossing properties; however, the anti-crossing behavior of dimers is more complex due to the strong coupling of dipoles and higher order plasmons with multiple molecular excitons. We find that the anti-crossing for dimers is clearly confirmed by the refractive index dependence of coupled resonance.",1911.08663v1 2019-11-26,Modulating Super-Exchange Strength to Achieve Robust Ferromagnetic Couplings in Two-Dimensional Semiconductors,"Low-dimensional semiconducting ferromagnets have attracted considerable attention due to their promising applications as nano-size spintronics. However, realizing robust ferromagnetic couplings that can survive at high temperature is restrained by two decisive factors: super-exchange couplings and anisotropy. Despite widely explored low-dimensional anisotropy, strengthening super-exchange couplings has rarely been investigated. Here, we found that ligands with lower electronegativity can strengthen ferromagnetic super-exchange couplings and further proposed the ligand modulation strategy to enhance the Curie temperature of low-dimensional ferromagnets. Based on the metallic CrX2 (X = S, Se, Te) family, substituting ligand atoms by halides can form stable semiconducting phase as CrSeCl, CrSeBr and CrTeBr. It is interesting to discover that, the nearest ferromagnetic super-exchange couplings can be strengthened when substituting ligands from S to Se and Te. Such evolution originates from the enhanced electron hopping integral and reduced energy intervals between d and p orbits. While the second nearest anti-ferromagnetic couplings are also benefitted due to delocalized p-p interactions. Finally, ligand modulation strategy is applied in other ferromagnetic monolayers, further verifying our theory and providing a fundamental understanding on controlling super-exchange couplings in low-dimension.",1911.11333v1 2019-12-06,Synthetic spin-orbit coupling mediated by a bosonic environment,"We study a mobile quantum impurity, possessing internal rotational degrees of freedom, confined to a ring in the presence of a many-particle bosonic bath. By considering the recently introduced rotating polaron problem, we define the Hamiltonian and examine the energy spectrum. The weak-coupling regime is studied by means of a variational ansatz in the truncated Fock space. The corresponding spectrum indicates that there emerges a coupling between the internal and orbital angular momenta of the impurity as a consequence of the phonon exchange. We interpret the coupling as a phonon-mediated spin-orbit coupling and quantify it by using a correlation function between the internal and orbital angular momentum operators. The strong-coupling regime is investigated within the Pekar approach and it is shown that the correlation function of the ground state shows a kink at a critical coupling, that is explained by a sharp transition from the non-interacting state to the states that exhibit strong interaction with the surroundings. The results might find applications in such fields as spintronics or topological insulators, where spin-orbit coupling is of crucial importance.",1912.03092v2 2019-12-09,Weakly Nonlinear Theory for Oscillatory Dynamics in a One-Dimensional PDE-ODE Model of Membrane Dynamics Coupled by a Bulk Diffusion Field,"We study the dynamics of systems consisting of two spatially segregated ODE compartments coupled through a one-dimensional bulk diffusion field. For this coupled PDE-ODE system, we first employ a multi-scale asymptotic expansion to derive amplitude equations near codimension-one Hopf bifurcation points for both in-phase and anti-phase synchronization modes. The resulting normal form equations pertain to any vector nonlinearity restricted to the ODE compartments. In our first example, we apply our weakly nonlinear theory to a coupled PDE-ODE system with Sel'kov membrane kinetics, and show that the symmetric steady state undergoes supercritical Hopf bifurcations as the coupling strength and the diffusivity vary. We then consider the PDE diffusive coupling of two Lorenz oscillators. It is shown that this coupling mechanism can have a stabilizing effect, characterized by a significant increase in the Rayleigh number required for a Hopf bifurcation. Within the chaotic regime, we can distinguish between synchronous chaos, where both the left and right oscillators are in-phase, and chaotic states characterized by the absence of synchrony. Finally, we compute the largest Lyapunov exponent associated with a linearization around the synchronous manifold that only considers odd perturbations. This allows us to predict the transition to synchronous chaos as the coupling strength and the diffusivity increase.",1912.04237v2 2019-12-31,Topological and nontopological edge states induced by qubit-assisted coupling potentials,"In the usual Su-Schrieffer-Heeger (SSH) chain, the topology of the energy spectrum is divided into two categories in different parameter regions. Here we study the topological and nontopological edge states induced by qubit-assisted coupling potentials in circuit quantum electrodynamics (QED) lattice system modelled as a SSH chain. We find that, when the coupling potential added on only one end of the system raises to a certain extent, the strong coupling potential will induce a new topologically nontrivial phase accompanied with the appearance of a nontopological edge state in the whole parameter region, and the novel phase transition leads to the inversion of odd-even effect in the system directly. Furthermore, we also study the topological properties as well as phase transitions when two unbalanced coupling potentials are injected into both the ends of the circuit QED lattice system, and find that the system exhibits three distinguishing phases in the process of multiple flips of energy bands. These phases are significantly different from the previous phase induced via unilateral coupling potential, which is reflected by the existence of a pair of nontopological edge states under strong coupling potential regime. Our scheme provides a feasible and visible method to induce a variety of different kinds of topological and nontopological edge states through controlling the qubit-assisted coupling potentials in circuit QED lattice system both in experiment and theory.",1912.13217v1 2015-08-06,"Non-Isothermal, Multi-phase, Multi-component Flows through Deformable Methane Hydrate Reservoirs","We present a hydro-geomechanical model for subsurface methane hydrate systems. Our model considers kinetic hydrate phase change and non-isothermal, multi-phase, multi-component flow in elastically deforming soils. The model accounts for the effects of hydrate phase change and pore pressure changes on the mechanical properties of the soil, and also for the effect of soil deformation on the fluid-solid interaction properties relevant to reaction and transport processes (e.g., permeability, capillary pressure, reaction surface area). We discuss a 'cause-effect' based decoupling strategy for the model and present our numerical discretization and solution scheme. We then identify the important model components and couplings which are most vital for a hydro-geomechanical hydrate simulator, namely, 1) dissociation kinetics, 2) hydrate phase change coupled with non-isothermal two phase two component flow, 3) two phase flow coupled with linear elasticity (poroelasticity coupling), and finally 4) hydrate phase change coupled with poroelasticity (kinetics-poroelasticity coupling) and present numerical examples where, for each example, one of the aforementioned model components/couplings is isolated. A special emphasis is laid on the kinetics-poroelasticity coupling. We also present a more complex 3D example based on a subsurface hydrate reservoir which is destabilized through depressurization using a low pressure gas well. In this example, we simulate the melting of hydrate, methane gas generation, and the resulting ground subsidence and stress build-up in the vicinity of the well.",1508.01421v1 2015-08-07,Fermionic extensions of the Standard Model in light of the Higgs couplings,"As the Higgs boson properties settle, the constraints on the Standard Model extensions tighten. We consider all possible new fermions that can couple to the Higgs, inspecting sets of up to four chiral multiplets. We confront them with direct collider searches, electroweak precision tests, and current knowledge of the Higgs couplings. The focus is on scenarios that may depart from the decoupling limit of very large masses and vanishing mixing, as they offer the best prospects for detection. We identify exotic chiral families that may receive a mass from the Higgs only, still in agreement with the $h\gamma\gamma$ signal strength. A mixing $\theta$ between the Standard Model and non-chiral fermions induces order $\theta^2$ deviations in the Higgs couplings. The mixing can be as large as $\theta\sim 0.5$ in case of custodial protection of the $Z$ couplings or accidental cancellation in the oblique parameters. We also notice some intriguing effects for much smaller values of $\theta$, especially in the lepton sector. Our survey includes a number of unconventional pairs of vector-like and Majorana fermions coupled through the Higgs, that may induce order one corrections to the Higgs radiative couplings. We single out the regions of parameters where $h\gamma\gamma$ and $hgg$ are unaffected, while the $h\gamma Z$ signal strength is significantly modified, turning a few times larger than in the Standard Model in two cases. The second run of the LHC will effectively test most of these scenarios.",1508.01645v2 2016-03-05,Identifiability of Electrical and Heat Transfer Parameters Using Coupled Boundary Measurements,"In this paper, we show that a hybrid method using coupled boundary measurements can determine electrical conductivity, thermal conductivity, and the product of heat capacity and heat density within a bounded domain on the plane uniquely up to a boundary-fixing diffromorphism.",1603.01754v1 2016-03-17,Existence of Strong and Nontrivial Solutions to Strongly Coupled Elliptic Systems,"We establish the existence of strong solutions to a class of nonlinear strongly coupled and uniform elliptic systems consisting of more than two equations. The existence of of nontrivial and non constant solutions (or pattern formations) will also be studied.",1603.05481v1 2016-03-30,Rashba-type Spin-orbit Coupling in Bilayer Bose-Einstein Condensates,"We explore a new way of producing the Rashba spin-orbit coupling (SOC) for ultracold atoms by using a two-component (spinor) atomic Bose-Einstein condensate (BEC) confined in a bilayer geometry. The SOC of the Rashba type is created if the atoms pick up a {\pi} phase after completing a cyclic transition between four combined spin-layer states composed of two spin and two layer states. The cyclic coupling of the spin-layer states is carried out by combining an intralayer Raman coupling and an interlayer laser assisted tunneling. We theoretically determine the ground-state phases of the spin-orbit-coupled BEC for various strengths of the atom-atom interaction and the laser-assisted coupling. It is shown that the bilayer scheme provides a diverse ground-state phase diagram. In an intermediate range of the atom-light coupling two interlacing lattices of half- skyrmions and half-antiskyrmions are spontaneously created. In the strong-coupling regime, where the SOC of the Rashba-type is formed, the ground state represents plane-wave or standing-wave phases depending on the interaction between the atoms. A variational analysis is shown to be in a good agreement with the numerical results.",1603.09043v2 2016-03-30,Euclidean Supergravity in Five Dimensions,"We construct a 5D, N = 2 Euclidean theory of supergravity coupled to vector multiplets. Upon reducing this theory over a circle we recover the action of 4D, N = 2 Euclidean supergravity coupled to vector multiplets.",1603.09244v1 2016-10-06,Emergence of phase concentration for the Kuramoto-Sakaguchi equation,"We study the asymptotic phase concentration phenomena for the Kuramoto-Sakaguchi(K-S) equation in a large coupling strength regime. For this, we analyze the detailed dynamics of the order parameters such as the amplitude and the average phase. For the infinite ensemble of oscillators with the identical natural frequency, we show that the total mass distribution concentrates on the average phase asymptotically, whereas the mass around the antipodal point of the average phase decays to zero exponentially fast in any positive coupling strength regime. Thus, generic initial kinetic densities evolve toward the Dirac measure concentrated on the average phase. In contrast, for the infinite ensemble with distributed natural frequencies, we find a certain time-dependent interval whose length can be explicitly quantified in terms of the coupling strength. Provided that the coupling strength is sufficiently large, the mass on such an interval is eventually non-decreasing over the time. We also show that the amplitude order parameter has a positive lower bound that depends on the size of support of the distribution function for the natural frequencies and the coupling strength. The proposed asymptotic lower bound on the order parameter tends to unity, as the coupling strength increases to infinity. This is reminiscent of practical synchronization for the Kuramoto model, in which the diameter for the phase configuration is inversely proportional to the coupling strength. Our results for the K-S equation generalize the results in [19] on the emergence of phase-locked states for the Kuramoto model in a large coupling strength regime.",1610.01703v1 2016-10-10,Exploring the Top-Higgs FCNC Couplings at Polarized Linear Colliders with Top Spin Observables,"We study the nature of the flavor changing neutral couplings of the top quark with the Higgs boson and the up/charm quark in the $t\bar{t}$ production at linear colliders. There are previous bounds on such tqH couplings at both, linear and hadronic colliders, with the assumption that it couples equally to the left and the right handed fermions. In this paper we examine the chirality of the tqH coupling and construct different observables which will be sensitive to it. The kinematics of the emitted q from t $\rightarrow$ qH in $t\bar{t}$ production is discussed and it was found that the polar angle distribution of q is sensitive to the chiral nature of tqH couplings. The observables in the context of top-antitop spin correlations, which are sensitive to new physics in the top decay are considered using different spin-quantization bases. It was found that in particular the off-diagonal basis can be useful to distinguish among the chiral tqH couplings. The sensitivity of the unpolarized ILC in probing the couplings at the 3$\sigma$ level at $\sqrt{s}$ = 500 GeV and L = 500 fb$^{-1}$ is also studied, resulting in predicted BR(t $\rightarrow$ qH) < 1.19 $\times 10^{-3}$. This limit is further improved to BR(t $\rightarrow$ qH) < 8.84 $\times 10^{-4}$ with the inclusion of initial beam polarization of left handed electrons and right handed positrons.",1610.02983v2 2016-10-27,Efficient fiber-coupled single-photon source based on quantum dots in a photonic-crystal waveguide,"Many photonic quantum information processing applications would benefit from a high brightness, fiber-coupled source of triggered single photons. Here, we present a fiber-coupled photonic-crystal waveguide single-photon source relying on evanescent coupling of the light field from a tapered out-coupler to an optical fiber. A two-step approach is taken where the performance of the tapered out-coupler is recorded first on an independent device containing an on-chip reflector. Reflection measurements establish that the chip-to-fiber coupling efficiency exceeds 80 %. The detailed characterization of a high-efficiency photonic-crystal waveguide extended with a tapered out-coupling section is then performed. The corresponding overall single-photon source efficiency is 10.9 % $\pm$ 2.3 %, which quantifies the success probability to prepare an exciton in the quantum dot, couple it out as a photon in the waveguide, and subsequently transfer it to the fiber. The applied out-coupling method is robust, stable over time, and broadband over several tens of nanometers, which makes it a highly promising pathway to increase the efficiency and reliability of planar chip-based single-photon sources.",1610.08670v1 2016-12-02,Remote synchronization in networks of coupled oscillators,"We study under which conditions systems of coupled oscillators on complex networks display remote synchronization, a situation where pairs of vertices, not necessarily physically linked, but with the same network symmetry, are synchronized.",1612.00658v1 2017-07-18,Employing coupled cavities to increase the cooling rate of a levitated nanosphere in the resolved sideband regime,"In this paper we investigate cooling of a levitated nanosphere in a system of coupled cavities in the resolved sideband regime. Thanks to the presence of an extra resonance in the coupled cavity cooling system, the coupling strength can be maximized at the optimum detuning. In this fashion, the intra-cavity photon number is increased and thereby the cooling rate is enhanced and the strong coupling regime is achieved without resorting to increased driving laser power. The underlying physics of the increased cooling efficiency in the here-proposed system of coupled cavities in the resolved sideband regime and that of the already reported system of coupled cavities in the unresolved sideband regime are significantly different from each other. Since the spectral density of the displacement of the particle can no longer be accurately approximated by the conventional Lorentzian lineshape in the strong coupling regime, a double Lorentzian lineshape is employed to accurately approximate the spectral density of the displacement of the particle and to provide analytical formulations for the cooling rate. The analytical expression given for the cooling rate is validated by numerical simulations.",1707.05823v2 2017-11-02,On one-loop impacts of the Rashba coupling,"In this paper, we describe the one-loop contributions in QED with Rashba coupling. We show that all purely nonminimal contributions are explicitly finite, so, the whole theory is one-loop renormalizable.",1711.02981v1 2017-11-30,Theory for polariton-assisted remote energy transfer,"Strong-coupling between light and matter produces hybridized states (polaritons) whose delocalization and electromagnetic character allow for novel modifications in spectroscopy and chemical reactivity of molecular systems. Recent experiments have demonstrated remarkable distance-independent long-range energy transfer between molecules strongly coupled to optical microcavity modes. To shed light on the mechanism of this phenomenon, we present the first comprehensive theory of polariton-assisted remote energy transfer (PARET) based on strong-coupling of donor and/or acceptor chromophores to surface plasmons. Application of our theory demonstrates that PARET up to a micron is indeed possible via strong-coupling. In particular, we report two regimes for PARET: in one case, strong-coupling to a single type of chromophore leads to transfer mediated largely by surface plasmons while in the other case, strong-coupling to both types of chromophores creates energy transfer pathways mediated by vibrational relaxation. Importantly, we highlight conditions under which coherence enhances or deteriorates these processes. For instance, while exclusive strong-coupling to donors can enhance transfer to acceptors, the reverse turns out not to be true. However, strong-coupling to acceptors can shift energy levels in a way that transfer from acceptors to donors can occur, thus yielding a chromophore role-reversal or ""carnival effect."" This theoretical study demonstrates the potential for confined electromagnetic fields to control and mediate PARET, thus opening doors to the design of remote mesoscale interactions between molecular systems.",1711.11576v2 2019-05-07,Dissipative Bose-Josephson junction coupled to bosonic baths,"We investigate the effect of dissipation in a Bose-Josephson junction (BJJ) coupled to bath of bosons at two sites. Apart from the dynamical transition due to repulsive interactions, the BJJ undergoes a quantum phase transition by increasing the coupling strength with the bath modes. We analyze this system by mapping to an equivalent spin model coupled to the bosonic modes. The excitation energies and fluctuation of number imbalance are obtained within Holstein-Primakoff approximation, which exhibit vanishing of energy gap and enhanced quantum fluctuations at the critical coupling. We study the dynamics of BJJ using time dependent variational method and analyze stability of different types of steady states. As a special case we study in details the phase space dynamics of BJJ coupled to a single mode, which reveals diffusive and incoherent behaviour with increasing coupling to the bath mode. The dynamical steady states corresponding to the Pi-oscillation and self-trapped state become unstable in the region where their oscillation frequencies are in resonance with the bath modes. We investigate the time evolution of number imbalance and relative phase in presence of Ohmic bath with Gaussian noise to incorporate thermal fluctuations. Apart from damping of Josephson oscillations and transition to symmetry broken state for strong coupling we observe decay of Pi-oscillation and self-trapped state to the ground state as a result of dissipation. Variation of phase fluctuation with temperature of the bath shows similar behaviour as observed in experiment. Finally we discuss the experimental setup to study the observable effects of dissipation in BJJ.",1905.02668v1 2020-06-09,The continuum limit of the conformal sector at second order in perturbation theory,"Recently a novel perturbative continuum limit for quantum gravity has been proposed and demonstrated to work at first order. Every interaction monomial $\sigma$ is dressed with a coefficient function $f^\sigma_\Lambda(\varphi)$ of the conformal factor field, $\varphi$. Each coefficient function is parametrised by an infinite number of underlying couplings, and decays at large $\varphi$ with a characteristic amplitude suppression scale which can be chosen to be at a common value, $\Lambda_\text{p}$. Although the theory is perturbative in couplings it is non-perturbative in $\hbar$. At second order in perturbation theory, one must sum over all melonic Feynman diagrams to obtain the particular integral. We show that it leads to a well defined renormalized trajectory and thus continuum limit, provided it is solved by starting at an arbitrary cutoff scale $\Lambda=\mu$ which lies in the range $0<\mu