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0704.0301

Akitoshi Kawamura

Akitoshi Kawamura

Differential Recursion and Differentially Algebraic Functions

14 pages, 3 figures

Revised and published in ACM Trans. Comput. Logic 10, Article 22, 2009, under the title "Differential Recursion".

10.1145/1507244.1507252

cs.CC

Moore introduced a class of real-valued "recursive" functions by analogy with Kleene's formulation of the standard recursive functions. While his concise definition inspired a new line of research on analog computation, it contains some technical inaccuracies. Focusing on his "primitive recursive" functions, we pin down what is problematic and discuss possible attempts to remove the ambiguity regarding the behavior of the differential recursion operator on partial functions. It turns out that in any case the purported relation to differentially algebraic functions, and hence to Shannon's model of analog computation, fails.

0704.0302

Li Wang

Li Wang and Lijian Yang

Spline Single-Index Prediction Model

39 pages,5 figures

math.ST stat.TH

For the past two decades, single-index model, a special case of projection pursuit regression, has proven to be an efficient way of coping with the high dimensional problem in nonparametric regression. In this paper, based on weakly dependent sample, we investigate the single-index prediction (SIP) model which is robust against deviation from the single-index model. The single-index is identified by the best approximation to the multivariate prediction function of the response variable, regardless of whether the prediction function is a genuine single-index function. A polynomial spline estimator is proposed for the single-index prediction coefficients, and is shown to be root-n consistent and asymptotically normal. An iterative optimization routine is used which is sufficiently fast for the user to analyze large data of high dimension within seconds. Simulation experiments have provided strong evidence that corroborates with the asymptotic theory. Application of the proposed procedure to the rive flow data of Iceland has yielded superior out-of-sample rolling forecasts.

0704.0303

Stefan Westerhoff

S.Y. BenZvi, B.M. Connolly, J.A.J. Matthews, M. Prouza, E.F. Visbal, S. Westerhoff

Measurement of the Aerosol Phase Function at the Pierre Auger Observatory

19 pages, 10 figures (4 in color), replaced with version accepted for publication in Astroparticle Physics

Astropart.Phys.28:312-320,2007

10.1016/j.astropartphys.2007.06.005

astro-ph physics.ao-ph

Air fluorescence detectors measure the energy of ultra-high energy cosmic rays by collecting fluorescence light emitted from nitrogen molecules along the extensive air shower cascade. To ensure a reliable energy determination, the light signal needs to be corrected for atmospheric effects, which not only attenuate the signal, but also produce a non-negligible background component due to scattered Cherenkov light and multiple-scattered light. The correction requires regular measurements of the aerosol attenuation length and the aerosol phase function, defined as the probability of light scattered in a given direction. At the Pierre Auger Observatory in Malargue, Argentina, the phase function is measured on an hourly basis using two Aerosol Phase Function (APF) light sources. These sources direct a UV light beam across the field of view of the fluorescence detectors; the phase function can be extracted from the image of the shots in the fluorescence detector cameras. This paper describes the design, current status, standard operation procedure, and performance of the APF system at the Pierre Auger Observatory.

0704.0304

Carlos Gershenson

Carlos Gershenson

The World as Evolving Information

16 pages. Extended version, three more laws of information, two classifications, and discussion added. To be published (soon) in International Conference on Complex Systems 2007 Proceedings

Minai, A., Braha, D., and Bar-Yam, Y., eds. Unifying Themes in Complex Systems VII, pp. 100-115. Springer, Berlin Heidelberg, 2012

10.1007/978-3-642-18003-3_10

cs.IT cs.AI math.IT q-bio.PE

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

This paper discusses the benefits of describing the world as information, especially in the study of the evolution of life and cognition. Traditional studies encounter problems because it is difficult to describe life and cognition in terms of matter and energy, since their laws are valid only at the physical scale. However, if matter and energy, as well as life and cognition, are described in terms of information, evolution can be described consistently as information becoming more complex. The paper presents eight tentative laws of information, valid at multiple scales, which are generalizations of Darwinian, cybernetic, thermodynamic, psychological, philosophical, and complexity principles. These are further used to discuss the notions of life, cognition and their evolution.

0704.0305

Yongxing Guo

Yongxing Guo, Yifeng Liu, Jay X. Tang, and James M. Valles Jr

Polymerization Force Driven Buckling of Microtubule Bundles Determines the Wavelength of Patterns Formed in Tubulin Solutions

4 pages, 4 figures

Phys. Rev. Lett. 98, 198103 (2007)

10.1103/PhysRevLett.98.198103

physics.bio-ph

We present a model for the spontaneous formation of a striated pattern in polymerizing microtubule solutions. It describes the buckling of a single microtubule (MT) bundle within an elastic network formed by other similarly aligned and buckling bundles and unaligned MTs. Phase contrast and polarization microscopy studies of the temporal evolution of the pattern imply that the polymerization of MTs within the bundles creates the driving compressional force. Using the measured rate of buckling, the established MT force-velocity curve and the pattern wavelength, we obtain reasonable estimates for the MT bundle bending rigidity and the elastic constant of the network. The analysis implies that the bundles buckle as solid rods.

0704.0306

Dongming Mei

D.-M. Mei, S.R. Elliott, A. Hime, V. Gehman and K. Kazkaz

Neutron Inelastic Scattering Processes as Background for Double-Beta Decay Experiments

16 pages, 7 figures

Phys.Rev.C77:054614,2008

10.1103/PhysRevC.77.054614

nucl-ex hep-ex

We investigate several Pb$(n,n'\gamma$) and Ge$(n,n'\gamma$) reactions. We measure $\gamma$-ray production from Pb$(n,n'\gamma$) reactions that can be a significant background for double-beta decay experiments which use lead as a massive inner shield. Particularly worrisome for Ge-based double-beta decay experiments are the 2041-keV and 3062-keV $\gamma$ rays produced via Pb$(n,n'\gamma$). The former is very close to the ^{76}Ge double-beta decay endpoint energy and the latter has a double escape peak energy near the endpoint. Excitation $\gamma$-ray lines from Ge$(n,n'\gamma$) reactions are also observed. We consider the contribution of such backgrounds and their impact on the sensitivity of next-generation searches for neutrinoless double-beta decay using enriched germanium detectors.

0704.0307

Eric L. N. Jensen

Eric L. N. Jensen (1), Saurav Dhital (1,2), Keivan G. Stassun (2), Jenny Patience (3), William Herbst (4), Frederick M. Walter (5), Michal Simon (5), Gibor Basri (6); (1 - Swarthmore College; 2 - Vanderbilt; 3 - Caltech; 4 - Wesleyan University; 5 - SUNY Stony Brook; 6 - UC Berkeley)

Periodic accretion from a circumbinary disk in the young binary UZ Tau E

Accepted by the Astronomical Journal; to appear July 2007; Corrected minor typos

Astron.J.134:241-251,2007

10.1086/518408

astro-ph

Close pre-main-sequence binary stars are expected to clear central holes in their protoplanetary disks, but the extent to which material can flow from the circumbinary disk across the gap onto the individual circumstellar disks has been unclear. In binaries with eccentric orbits, periodic perturbation of the outer disk is predicted to induce mass flow across the gap, resulting in accretion that varies with the binary period. This accretion may manifest itself observationally as periodic changes in luminosity. Here we present a search for such periodic accretion in the pre-main-sequence spectroscopic binary UZ Tau E. We present BVRI photometry spanning three years; we find that the brightness of UZ Tau E is clearly periodic, with a best-fit period of 19.16 +/- 0.04 days. This is consistent with the spectroscopic binary period of 19.13 days, refined here from analysis of new and existing radial velocity data. The brightness of UZ Tau E shows significant random variability, but the overall periodic pattern is a broad peak in enhanced brightness, spanning more than half the binary orbital period. The variability of the H-alpha line is not as clearly periodic, but given the sparseness of the data, some periodic component is not ruled out. The photometric variations are in good agreement with predictions from simulations of binaries with orbital parameters similar to those of UZ Tau E, suggesting that periodic accretion does occur from circumbinary disks, replenishing the inner disks and possibly extending the timescale over which they might form planets.

0704.0308

Ke Deng

Ke Deng, Heping Zhao, Dejun Li

Effect of node deleting on network structure

12 pages, 9 figures, to be published in physica a

Physica A 379 (2007) 714-726

10.1016/j.physa.2007.02.039

physics.soc-ph

The ever-increasing knowledge of the structure of various real-world networks has uncovered their complex multi-mechanism-governed evolution processes. Therefore, a better understanding of the structure and evolution of these networked complex systems requires us to describe such processes in a more detailed and realistic manner. In this paper, we introduce a new type of network growth rule which comprises addition and deletion of nodes, and propose an evolving network model to investigate the effect of node deleting on network structure. It is found that, with the introduction of node deleting, network structure is significantly transformed. In particular, degree distribution of the network undergoes a transition from scale-free to exponential forms as the intensity of node deleting increases. At the same time, nontrivial disassortative degree correlation develops spontaneously as a natural result of network evolution in the model. We also demonstrate that node deleting introduced in the model does not destroy the connectedness of a growing network so long as the increasing rate of edges is not excessively small. In addition, it is found that node deleting will weaken but not eliminate the small-world effect of a growing network, and generally it will decrease the clustering coefficient in a network.

0704.0309

Guohun Zhu

Guohun Zhu

The Complexity of HCP in Digraps with Degree Bound Two

10 pages, 4 figures, had been submitted to a Journal

cs.CC cs.DM

The Hamiltonian cycle problem (HCP) in digraphs D with degree bound two is solved by two mappings in this paper. The first bijection is between an incidence matrix C_{nm} of simple digraph and an incidence matrix F of balanced bipartite undirected graph G; The second mapping is from a perfect matching of G to a cycle of D. It proves that the complexity of HCP in D is polynomial, and finding a second non-isomorphism Hamiltonian cycle from a given Hamiltonian digraph with degree bound two is also polynomial. Lastly it deduces P=NP base on the results.

0704.0310

Xiang Liu

Xiang Liu, Lang Cui, Wen-Feng Luo, Wei-Zhao Shi, Hua-Gang Song (Urumqi Observatory, NAOC)

VLBI observations of nineteen GHz-Peaked-Spectrum radio sources at 1.6 GHz

11 pages, 12 figures, to appear in AA

A&A 470, 97-104 (2007)

10.1051/0004-6361:20077265

astro-ph

Aims and Methods: We present the results of VLBI observations of nineteen GHz-Peaked-Spectrum (GPS) radio sources at 1.6 GHz. Of them, 15 sources are selected from the Parkes Half Jansky (PHJ) sample (Snellen 2002), 4 others are from our previous observation list. We aimed at imaging the structure of GPS sources, searching for Compact Symmetric Objects (CSOs) and studying the absorption for the convex radio spectra of GPS sources. Results: We obtained total intensity 1.6 GHz VLBI images of 17 sources for the first time. Of them, 80% show mini-double-lobe radio structure, indicating that they are CSOs or candidates, and their host AGNs could be edge-on to us. This result suggests that there is a high incidence of mini double-lobe sources (or CSOs) in the PHJ sample. The sources J0323+0534, J1135-0021, J1352+0232, J2058+0540, J2123-0112 and J2325-0344 with measured redshift, showing double-lobe structure with sizes of <1 kpc, are classified as CSOs. Three sources J1057+0012, J1600-0037 and J1753+2750 are considered as core-jet sources according to their morphologies and flux variability.

0704.0311

J. R. Kirtley

John R. Kirtley, Zhifeng Deng, Lan Luan, Erhan Yenilmez, Hongjie Dai, and Kathryn A. Moler

Moment switching in nanotube magnetic force probes

10 pages

10.1088/0957-4484/18/46/465506

cond-mat.mes-hall cond-mat.mtrl-sci

A recent advance in improving the spatial resolution of magnetic force microscopy (MFM) uses as sensor tips carbon nanotubes grown at the apex of conventional silicon cantilever pyramids and coated with a thin ferromagnetic layer. Magnetic images of high density vertically recorded media using these tips exhibit a doubling of the spatial frequency under some conditions. Here we demonstrate that this spatial frequency doubling is due to the switching of the moment direction of the nanotube tip. This results in a signal which is proportional to the absolute value of the signal normally observed in MFM. Our modeling indicates that a significant fraction of the tip volume is involved in the observed switching, and that it should be possible to image very high bit densities with nanotube magnetic force sensors.

0704.0312

Geraint F. Lewis

Matthew J. Francis, Geraint F. Lewis, Eric V. Linder

Power Spectra to 1% Accuracy between Dynamical Dark Energy Cosmologies

9 pages, 14 figures, submitted to MNRAS

Mon.Not.Roy.Astron.Soc.380:1079,2007

10.1111/j.1365-2966.2007.12139.x

GFL-001

astro-ph

For dynamical dark energy cosmologies we carry out a series of N-body gravitational simulations, achieving percent level accuracy in the relative mass power spectra at any redshift. Such accuracy in the power spectrum is necessary for next generation cosmological mass probes. Our matching procedure reproduces the CMB distance to last scattering and delivers subpercent level power spectra at z=0 and z~3. We discuss the physical implications for probing dark energy with surveys of large scale structure.

0704.0313

Yuta Hayashi

Yuta Hayashi, Masao Ogata

Possibility of Gapless Spin Liquid State by One-dimensionalization

4 pages, 4 figures(downsized), To appear in J. Phys. Soc. Jpn.

J.Phys.Soc.Jpn. 76 (2007) 053705.

10.1143/JPSJ.76.053705

cond-mat.str-el

Motivated by the observation of a gapless spin liquid state in $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$, we analyze the anisotropic triangular lattice $S=1/2$ Heisenberg model with the resonating valence bond mean-field approximation. Paying attention to the small quasi-one-dimensional anisotropy of the material, we take an approach from one-dimensional (1D) chains coupled with frustrating zig-zag bonds. By calculating one-particle excitation spectra changing anisotropy parameter $J'/J$ from the decoupled 1D chains to the isotropic triangular lattice, we find almost gapless excitations in the wide range from the 1D limit. This one-dimensionalization by frustration is considered to be a candidate for the mechanism of the gapless spin liquid state.

0704.0314

Alexander Zhuk

Viktor Baukh, Alexander Zhuk, Tina Kahniashvili

Extra dimensions and Lorentz invariance violation

RevTex, 5 pages, references added and minor changes. Corrected typos in title

Phys.Rev.D76:027502,2007

10.1103/PhysRevD.76.027502

hep-ph astro-ph hep-th

We consider effective model where photons interact with scalar field corresponding to conformal excitations of the internal space (geometrical moduli/gravexcitons). We demonstrate that this interaction results in a modified dispersion relation for photons, and consequently, the photon group velocity depends on the energy implying the propagation time delay effect. We suggest to use the experimental bounds of the time delay of gamma ray bursts (GRBs) photons propagation as an additional constrain for the gravexciton parameters.

0704.0315

Vitalii Gasanenko A.

Vitalii A. Gasanenko

The small deviations of many-dimensional diffusion processes and rarefaction by boundaries

10 pages

math.PR math.AP

We lead the algorithm of expansion of sojourn probability of many-dimensional diffusion processes in small domain. The principal member of this expansion defines normalizing coefficient for special limit theorems.

0704.0316

Alister W. Graham

Alister W. Graham, Simon P. Driver, Paul D. Allen, Jochen Liske

The Millennium Galaxy Catalogue: The local supermassive black hole mass function in early- and late-type galaxies

10 pages of text plus 5 of figs and refs. MNRAS, accepted.

Mon.Not.Roy.Astron.Soc.378:198-210,2007

10.1111/j.1365-2966.2007.11770.x

astro-ph

We provide a new estimate of the local supermassive black hole mass function using (i) the empirical relation between supermassive black hole mass and the Sersic index of the host spheroidal stellar system and (ii) the measured (spheroid) Sersic indices drawn from 10k galaxies in the Millennium Galaxy Catalogue. The observational simplicity of our approach, and the direct measurements of the black hole predictor quantity, i.e. the Sersic index, for both elliptical galaxies and the bulges of disc galaxies makes it straightforward to estimate accurate black hole masses in early- and late-type galaxies alike. We have parameterised the supermassive black hole mass function with a Schechter function and find, at the low-mass end, a logarithmic slope (1+alpha) of ~0.7 for the full galaxy sample and ~1.0 for the early-type galaxy sample. Considering spheroidal stellar systems brighter than M_B = -18 mag, and integrating down to black hole masses of 10^6 M_sun, we find that the local mass density of supermassive black holes in early-type galaxies rho_{bh, early-type} = (3.5+/-1.2) x 10^5 h^3_{70} M_sun Mpc^{-3}, and in late-type galaxies rho_{bh, late-type} = (1.0+/-0.5) x 10^5 h^3_{70} M_sun Mpc^{-3}. The uncertainties are derived from Monte Carlo simulations which include uncertainties in the M_bh-n relation, the catalogue of Sersic indices, the galaxy weights and Malmquist bias. The combined, cosmological, supermassive black hole mass density is thus Omega_{bh, total} = (3.2+/-1.2) x 10^{-6} h_70. That is, using a new and independent method, we conclude that (0.007+/-0.003) h^3_{70} per cent of the universe's baryons are presently locked up in supermassive black holes at the centres of galaxies.

0704.0317

William Wylie

William Wylie

Complete Shrinking Ricci Solitons have Finite Fundamental Group

4 pages, To appear in Proceedings of AMS

math.DG

We show that if a complete Riemannian manifold supports a vector field such that the Ricci tensor plus the Lie derivative of the metric with respect to the vector field has a positive lower bound, then the fundamental group is finite. In particular, it follows that complete shrinking Ricci solitons and complete smooth metric measure spaces with a positive lower bound on the Bakry-Emery tensor have finite fundamental group. The method of proof is to generalize arguments of Garcia-Rio and Fernandez-Lopez in the compact case.

0704.0318

Subhrajyoti Biswas

Subhrajyoti Biswas and Abhee K. Dutt-Mazumder

Effects of Dirac sea on pion propagation in asymmetric nuclear matter

Accepted for publication in PRC

Phys.Rev.C77:045201,2008

10.1103/PhysRevC.77.045201

nucl-th hep-ph

We study pion propagation in asymmetric nuclear matter (ANM). One of the interesting consequences of pion propagation in ANM is the mode splitting for the different charged states of pions. First we describe the pion-nucleon dynamics using the non-chiral model where one starts with pseudoscalar (PS) $\pi$N coupling and the pseudovector (PV) representation is obtained via suitable non-linear field transformations. For both of these cases the effect of the Dirac sea is estimated. Subsequently, we present results using the chiral effective Lagrangian where the short-distance behavior (Dirac vacuum) is included by re-defining the field parameters as done in the modern effective field theory approach developed recently. The results are compared with the previous calculations for the case of symmetric nuclear matter (SNM). Closed form analytical results are presented for the effective pion masses and dispersion relations by making hard nucleon loop (HNL) approximation and suitable density expansion.

0704.0319

Guo-Hui Ding

Guo-Hui Ding and Bing Dong

Spin-orbit coupling effect on the persistent currents in mesoscopic ring with an Anderson impurity

10.1103/PhysRevB.76.125301

cond-mat.mes-hall

Based on the finite $U$ slave boson method, we have investigated the effect of Rashba spin-orbit(SO) coupling on the persistent charge and spin currents in mesoscopic ring with an Anderson impurity. It is shown that the Kondo effect will decrease the magnitude of the persistent charge and spin currents in this side-coupled Anderson impurity case. In the presence of SO coupling, the persistent currents change drastically and oscillate with the strength of SO coupling. The SO coupling will suppress the Kondo effect and restore the abrupt jumps of the persistent currents. It is also found that a persistent spin current circulating the ring can exist even without the charge current in this system.

0704.0320

Francesco Mainardi

Francesco Mainardi, Paolo Paradisi and Rudolf Gorenflo

Probability distributions generated by fractional diffusion equations

46 pages, 3 figures. International Workshop on Econophysics, Budapest, July 21-27, 1997.

cond-mat.stat-mech

Fractional calculus allows one to generalize the linear, one-dimensional, diffusion equation by replacing either the first time derivative or the second space derivative by a derivative of fractional order. The fundamental solutions of these equations provide probability density functions, evolving on time or variable in space, which are related to the class of stable distributions. This property is a noteworthy generalization of what happens for the standard diffusion equation and can be relevant in treating financial and economical problems where the stable probability distributions play a key role.

0704.0321

Dr. Kalobaran Maiti

Kalobaran Maiti

Fabrication of half metallicity in a ferromagnetic metal

4 pages, 5 figures

cond-mat.str-el cond-mat.mtrl-sci

We investigate the growth of half metallic phase in a ferromagnetic material using state-of-the-art full potential linearized augmented plane wave method. To address the issue, we have substituted Ti at the Ru-sites in SrRuO3, where SrRuO3 is a ferromagnetic material. Calculated results establish Ti4+ valence states (similar to SrTiO3), which was predicted experimentally. Thus, Ti substitution dilutes the Ru-O-Ru connectivity, which is manifested in the calculated results in the form of significant band narrowing leading to finite gap between t2g and eg bands. At 75% substitution, a large gap (> 2 eV) appears at the Fermi level, e_F in the up spin density of states, while the down spin states contributes at e_F characterizing the system a half-metallic ferromagnet. The t2g - eg gap can be tailored judiciously by tuning Ti concentrations to minimize thermal effects, which is often the major bottleneck to achieve high spin polarization at elevated temperatures in other materials. This study, thus, provides a novel but simple way to fabricate half-metallicity in ferromagnetic materials, which are potential candidates for spin-based technology.

0704.0322

Liu Quanxing

Quan-Xing Liu, Gui-Quan Sun, Bai-Lian Li and Zhen Jin

Emergence of spatiotemporal chaos driven by far-field breakup of spiral waves in the plankton ecological systems

9 Figures and 11 pages, REVTeX 4

2009 Chinese Phys. B 18 506-515

10.1088/1674-1056/18/2/021

nlin.PS nlin.CD q-bio.PE

Alexander B. Medvinsky \emph{et al} [A. B. Medvinsky, I. A. Tikhonova, R. R. Aliev, B.-L. Li, Z.-S. Lin, and H. Malchow, Phys. Rev. E \textbf{64}, 021915 (2001)] and Marcus R. Garvie \emph{et al} [M. R. Garvie and C. Trenchea, SIAM J. Control. Optim. \textbf{46}, 775-791 (2007)] shown that the minimal spatially extended reaction-diffusion model of phytoplankton-zooplankton can exhibit both regular, chaotic behavior, and spatiotemporal patterns in a patchy environment. Based on that, the spatial plankton model is furtherly investigated by means of computer simulations and theoretical analysis in the present paper when its parameters would be expected in the case of mixed Turing-Hopf bifurcation region. Our results show that the spiral waves exist in that region and the spatiotemporal chaos emerge, which arise from the far-field breakup of the spiral waves over large ranges of diffusion coefficients of phytoplankton and zooplankton. Moreover, the spatiotemporal chaos arising from the far-field breakup of spiral waves does not gradually involve the whole space within that region. Our results are confirmed by means of computation spectra and nonlinear bifurcation of wave trains. Finally, we give some explanations about the spatially structured patterns from the community level.

0704.0323

Heng Fan

Gui-Fang Dang, and Heng Fan

General sequential quantum cloning

4 pages

J.Phys.A 41, 155303 (2008)

10.1088/1751-8113/41/15/155303

quant-ph

Some multipartite quantum states can be generated in a sequential manner which may be implemented by various physical setups like microwave and optical cavity QED, trapped ions, and quantum dots etc. We analyze the general N to M qubits Universal Quantum Cloning Machine (UQCM) within a sequential generation scheme. We show that the N to M sequential UQCM is available. The case of d-level quantum states sequential cloning is also presented.

0704.0324

Karel Pravda-Starov

Karel Pravda-Starov

On the pseudospectrum of elliptic quadratic differential operators

39 pages

math.AP

We study the pseudospectrum of a class of non-selfadjoint differential operators. Our work consists in a detailed study of the microlocal properties, which rule the spectral stability or instability phenomena appearing under small perturbations for elliptic quadratic differential operators. The class of elliptic quadratic differential operators stands for the class of operators defined in the Weyl quantization by complex-valued elliptic quadratic symbols. We establish in this paper a simple necessary and sufficient condition on the Weyl symbol of these operators, which ensures the stability of their spectra. When this condition is violated, we prove that it occurs some strong spectral instabilities for the high energies of these operators, in some regions which can be far away from their spectra. We give a precise geometrical description of them, which explains the results obtained for these operators in some numerical simulations giving the computation of false eigenvalues far from their spectra by algorithms for eigenvalues computing.

0704.0325

Antoine Naert

Vincent Grenard (Phys-ENS), Nicolas Garnier (Phys-ENS), Antoine Naert (Phys-ENS)

Fluctuation-dissipation relation on a Melde string in a turbulent flow, considerations on a "dynamical temperature"

3,5 new printed pages

10.1088/1742-5468/2008/09/L09003

cond-mat.stat-mech physics.ins-det

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

We report on measurements of the transverse fluctuations of a string in a turbulent air jet flow. Harmonic modes are excited by the fluctuating drag force, at different wave-numbers. This simple mechanical probe makes it possible to measure excitations of the flow at specific scales, averaged over space and time: it is a scale-resolved, global measurement. We also measure the dissipation associated to the string motion, and we consider the ratio of the fluctuations over dissipation (FDR). In an exploratory approach, we investigate the concept of {\it effective temperature} defined through the FDR. We compare our observations with other definitions of temperature in turbulence. From the theory of Kolmogorov (1941), we derive the exponent -11/3 expected for the spectrum of the fluctuations. This simple model and our experimental results are in good agreement, over the range of wave-numbers, and Reynolds number accessible ($74000 \leq Re \leq 170000$).

0704.0326

Hans J. Haubold

A.M. Mathai, H.J. Haubold

On generalized entropy measures and pathways

12 pages, LaTeX, typos corrected

Physica A 385(2007)493-500

10.1016/j.physa.2007.06.047

math.ST cond-mat.stat-mech stat.TH

Product probability property, known in the literature as statistical independence, is examined first. Then generalized entropies are introduced, all of which give generalizations to Shannon entropy. It is shown that the nature of the recursivity postulate automatically determines the logarithmic functional form for Shannon entropy. Due to the logarithmic nature, Shannon entropy naturally gives rise to additivity, when applied to situations having product probability property. It is argued that the natural process is non-additivity, important, for example, in statistical mechanics, even in product probability property situations and additivity can hold due to the involvement of a recursivity postulate leading to a logarithmic function. Generalizations, including Mathai's generalized entropy are introduced and some of the properties are examined. Situations are examined where Mathai's entropy leads to pathway models, exponential and power law behavior and related differential equations. Connection of Mathai's entropy to Kerridge's measure of "inaccuracy" is also explored.

0704.0327

Dr. Kalobaran Maiti

Kalobaran Maiti, Ravi Shankar Singh, V.R.R. Medicherla

Evolution of a band insulating phase from a correlated metallic phase

4 figures

10.1103/PhysRevB.76.165128

cond-mat.str-el cond-mat.mtrl-sci

We investigate the evolution of the electronic structure in SrRu_(1-x)Ti_xO_3 as a function of x using high resolution photoemission spectroscopy, where SrRuO3 is a weakly correlated metal and SrTiO3 is a band insulator. The surface spectra exhibit a metal-insulator transition at x = 0.5 by opening up a soft gap. A hard gap appears at higher x values consistent with the transport properties. In contrast, the bulk spectra reveal a pseudogap at the Fermi level, and unusual evolution exhibiting an apparent broadening of the coherent feature and subsequent decrease in intensity of the lower Hubbard band with the increase in x. Interestingly, the first principle approaches are found to be sufficient to capture anomalous evolutions at high energy scale. Analysis of the spectral lineshape indicates strong interplay between disorder and electron correlation in the electronic properties of this system.

0704.0328

Seung Woo Ham

S.W. Ham, E.J. Yoo, S.K. OH

Electroweak phase transitions in the MSSM with an extra $U(1)'$

17 pages, 2 tables, 3 figures

Phys.Rev.D76:075011,2007

10.1103/PhysRevD.76.075011

hep-ph

We investigate the possibility of electroweak phase transition in the minimal supersymmetric standard model (MSSM) with an extra $U(1)'$. This model has two Higgs doublets and a singlet, in addition to a singlet exotic quark superfield. We find that at the one-loop level this model may accommodate the electroweak phase transitions that are strongly first-order in a reasonably large region of the parameter space. In the parameter region where the phase transitions take place, we observe that the lightest scalar Higgs boson has a smaller mass when the strength of the phase transition becomes weaker. Also, the other three heavier neutral Higgs bosons get more large masses when the strength of the phase transition becomes weaker.

0704.0329

Hans J. Haubold

H.J. Haubold, A.M. Mathai, R.K. Saxena

Solutions of fractional reaction-diffusion equations in terms of the H-function

9 pages, LaTeX, typos corrected

Bull. Astr. Soc. India 35(2007)681-689

math.PR math.CA math.ST stat.TH

This paper deals with the investigation of the solution of an unified fractional reaction-diffusion equation associated with the Caputo derivative as the time-derivative and Riesz-Feller fractional derivative as the space-derivative. The solution is derived by the application of the Laplace and Fourier transforms in closed form in terms of the H-function. The results derived are of general nature and include the results investigated earlier by many authors, notably by Mainardi et al. (2001, 2005) for the fundamental solution of the space-time fractional diffusion equation, and Saxena et al. (2006a, b) for fractional reaction- diffusion equations. The advantage of using Riesz-Feller derivative lies in the fact that the solution of the fractional reaction-diffusion equation containing this derivative includes the fundamental solution for space-time fractional diffusion, which itself is a generalization of neutral fractional diffusion, space-fractional diffusion, and time-fractional diffusion. These specialized types of diffusion can be interpreted as spatial probability density functions evolving in time and are expressible in terms of the H-functions in compact form.

0704.0330

Jacobus Verbaarschot

K. Splittorff and J.J.M. Verbaarschot

Random Matrix Theory at Nonzero $\mu$ and $T$

Invited talk at YKIS2006, YITP-Kyoto, 10 pages, 10 figures

Prog.Theor.Phys.Suppl.168:265-275,2007

10.1143/PTPS.168.265

hep-ph

We review applications of random matrix theory to QCD at nonzero temperature and chemical potential. The chiral phase transition of QCD and QCD-like theories is discussed in terms of eigenvalues of the Dirac operator. We show that for QCD at $\mu \ne 0$, which has a sign problem, the discontinuity in the chiral condensate is due to an alternative to the Banks-Casher relation. The severity of the sign problem is analyzed in the microscopic domain of QCD.

0704.0331

C. Soule

J.-L. Jestin, C. Soule (IHES)

Symmetries by base substitutions in the genetic code predict 2' or 3' aminoacylation of tRNAs

Accepted for publication in the Journal of Theoretical Biology

q-bio.OT

This letter reports complete sets of two-fold symmetries between partitions of the universal genetic code. By substituting bases at each position of the codons according to a fixed rule, it happens that properties of the degeneracy pattern or of tRNA aminoacylation specificity are exchanged.

0704.0332

Timothy Sumner

M.B. Gerrard and T.J. Sumner

The effect of a fifth large-scale space-time dimension on the conservation of energy in a four dimensional Universe

9 pages, 2 figures version update to correct figure placement Final update to include corrected typos and two additional equations

gr-qc

The effect of introducing a fifth large-scale space-time dimension to the equations of orbital dynamics was analysed in an earlier paper by the authors. The results showed good agreement with the observed flat rotation curves of galaxies and the Pioneer Anomaly. This analysis did not require the modification of Newtonian dynamics, but rather only their restatement in a five dimensional framework. The same analysis derived a acceleration parameter ar, which plays an important role in the restated equations of orbital dynamics, and suggested a value for ar. In this companion paper, the principle of conservation of energy is restated within the same five-dimensional framework. The resulting analysis provides an alternative route to estimating the value of ar, without reference to the equations of orbital dynamics, and based solely on key cosmological constants and parameters, including the gravitational constant, G. The same analysis suggests that: (i) the inverse square law of gravity may itself be due to the conservation of energy at the boundary between a four-dimensional universe and a fifth large-scale space-time dimension; and (ii) there is a limiting case for the Tulley-Fisher relationship linking the speed of light to the mass of the Universe.

0704.0333

Emmanuele Cappelluti

E. Cappelluti, S. Ciuchi, S. Fratini

Optical properties of the Holstein-t-J model from dynamical mean-field theory

Proceeding of SCES07 Conference

10.1016/j.physb.2007.10.107

cond-mat.str-el

We employ dynamical mean-field theory to study the optical conductivity $\sigma(\omega)$ of one hole in the Holstein-t-J model. We provide an exact solution for $\sigma(\omega)$ in the limit of infinite connectivity. We apply our analysis to Nd$_{2-x}$Ce$_x$CuO$_4$. We show that our model can explain many features of the optical conductivity in this compounds in terms of magnetic/lattice polaron formation.

0704.0334

Pratim Kumar Chattaraj

J. Padmanabhan (1,2), R. Parthasarathi (2), M. Elango (2), V. Subramanian (2), B. S. Krishnamoorthy (1,3), S. Gutierrez-Oliva (4), A. Toro-Labbe (4), D. R. Roy (1) and P. K. Chattaraj (1)

A Multiphilic Descriptor for Chemical Reactivity and Selectivity

38 pages, 8 figures, 11 tables

10.1021/jp0718909

physics.chem-ph

In line with the local philicity concept proposed by Chattaraj et al. (Chattaraj, P. K.; Maiti, B.; Sarkar, U. J. Phys. Chem. A. 2003, 107, 4973) and a dual descriptor derived by Toro-Labbe and coworkers (Morell, C.; Grand, A.; Toro-Labbe, A. J. Phys. Chem. A. 2005, 109, 205), we propose a multiphilic descriptor. It is defined as the difference between nucleophilic (Wk+) and electrophilic (Wk-) condensed philicity functions. This descriptor is capable of simultaneously explaining the nucleophilicity and electrophilicity of the given atomic sites in the molecule. Variation of these quantities along the path of a soft reaction is also analyzed. Predictive ability of this descriptor has been successfully tested on the selected systems and reactions. Corresponding force profiles are also analyzed in some representative cases. Also, to study the intra- and intermolecular reactivities another related descriptor namely, the nucleophilicity excess (DelW-+) for a nucleophile, over the electrophilicity in it has been defined and tested on all-metal aromatic compounds.

0704.0335

Fabien Panloup

Gilles Pag\`es (PMA, LSProba), Fabien Panloup (PMA)

Approximation of the distribution of a stationary Markov process with application to option pricing

Bernoulli 15, 1 (2009) 146-177

math.PR q-fin.CP q-fin.PR

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

We build a sequence of empirical measures on the space D(R_+,R^d) of R^d-valued c\`adl\`ag functions on R_+ in order to approximate the law of a stationary R^d-valued Markov and Feller process (X_t). We obtain some general results of convergence of this sequence. Then, we apply them to Brownian diffusions and solutions to L\'evy driven SDE's under some Lyapunov-type stability assumptions. As a numerical application of this work, we show that this procedure gives an efficient way of option pricing in stochastic volatility models.

0704.0336

Ilari J. Maasilta

J. T. Karvonen and I. J. Maasilta

Influence of Phonon dimensionality on Electron Energy Relaxation

Phys. Rev. Lett. in press

Phys. Rev. Lett. 99, 145503 (2007).

10.1103/PhysRevLett.99.145503

cond-mat.mes-hall

We studied experimentally the role of phonon dimensionality on electron-phonon (e-p) interaction in thin copper wires evaporated either on suspended silicon nitride membranes or on bulk substrates, at sub-Kelvin temperatures. The power emitted from electrons to phonons was measured using sensitive normal metal-insulator-superconductor (NIS) tunnel junction thermometers. Membrane thicknesses ranging from 30 nm to 750 nm were used to clearly see the onset of the effects of two-dimensional (2D) phonon system. We observed for the first time that a 2D phonon spectrum clearly changes the temperature dependence and strength of the e-p scattering rate, with the interaction becoming stronger at the lowest temperatures below $\sim$ 0.5 K for the 30 nm membranes.

0704.0337

Francois Golse

Fran\c{c}ois Golse (CMLS-EcolePolytechnique, LJLL), Alex Mahalov, Basil Nicolaenko

Bursting Dynamics of the 3D Euler Equations in Cylindrical Domains

Instability in models connected with fluid flows I, Int. Math. Ser. (N. Y.), 6, (Springer, New York, 2008), 301--338

math.AP

A class of three-dimensional initial data characterized by uniformly large vorticity is considered for the Euler equations of incompressible fluids. The fast singular oscillating limits of the Euler equations are studied for parametrically resonant cylinders. Resonances of fast swirling Beltrami waves deplete the Euler nonlinearity. The resonant Euler equations are systems of three-dimensional rigid body equations, coupled or not. Some cases of these resonant systems have homoclinic cycles, and orbits in the vicinity of these homoclinic cycles lead to bursts of the Euler solution measured in Sobolev norms of order higher than that corresponding to the enstrophy.

0704.0338

Sandrine Bec

Sandrine Bec (LTDS), Andr\'e Tonck (LTDS), Jean-Marie Georges (LTDS), Glyn W. Roper (SHELL)

Synergistic Effects of MoDTC and ZDTP on Frictional Behaviour of Tribofilms at the Nanometer Scale

Tribology Letters 4 (2004) 797-809

10.1007/s11249-004-8088-7

cond-mat.mtrl-sci

The layered structure and the rheological properties of anti-wear films, generated in a rolling/sliding contact from lubricants containing zinc dialkyldithiophosphate (ZDTP) and/or molybdenum dialkyldithiocarbamate (MoDTC) additives, have been studied by dynamic nanoindentation experiments coupled with a simple modelling of the stiffness measurements. Local nano-friction experiments were conducted with the same device in order to determine the evolution of the friction coefficient as a function of the applied pressure for the different lubricant formulations. For the MoDTC film, the applied pressure in the friction test remains low (<0.5 GPa) and the apparent friction coefficient is high ($\mu$ > 0.4). For the tribofilms containing MoDTC together with ZDTP, which permits the applied pressure to increase up to a few GPa through some accommodation process, a very low friction domain appears (0.01 < $\mu$ < 0.05), located a few nanometers below the surface of the tribofilm. This low friction coefficient is attributed to the presence of MoS2 planes sliding over each other in a favourable configuration obtained when the pressure is sufficiently high, which is made possible by the presence of ZDTP.

0704.0339

Massimo Tessarotto

Enrico Fonda, Massimo Tessarotto and Marco Ellero

Lattice Boltzmann inverse kinetic approach for the incompressible Navier-Stokes equations

physics.flu-dyn physics.comp-ph

In spite of the large number of papers appeared in the past which are devoted to the lattice Boltzmann (LB) methods, basic aspects of the theory still remain unchallenged. An unsolved theoretical issue is related to the construction of a discrete kinetic theory which yields \textit{exactly} the fluid equations, i.e., is non-asymptotic (here denoted as \textit{LB inverse kinetic theory}). The purpose of this paper is theoretical and aims at developing an inverse kinetic approach of this type. In principle infinite solutions exist to this problem but the freedom can be exploited in order to meet important requirements. In particular, the discrete kinetic theory can be defined so that it yields exactly the fluid equation also for arbitrary non-equilibrium (but suitably smooth) kinetic distribution functions and arbitrarily close to the boundary of the fluid domain. Unlike previous entropic LB methods the theorem can be obtained without functional constraints on the class of the initial distribution functions. Possible realizations of the theory and asymptotic approximations are provided which permit to determine the fluid equations \textit{with prescribed accuracy.} As a result, asymptotic accuracy estimates of customary LB approaches and comparisons with the Chorin artificial compressibility method are discussed.

0704.0340

Fam Le Kien

Fam Le Kien, S. Dutta Gupta, and K. Hakuta

Phonon-mediated decay of an atom in a surface-induced potential

14 pages, 15 figures

quant-ph

We study phonon-mediated transitions between translational levels of an atom in a surface-induced potential. We present a general master equation governing the dynamics of the translational states of the atom. In the framework of the Debye model, we derive compact expressions for the rates for both upward and downward transitions. Numerical calculations for the transition rates are performed for a deep silica-induced potential allowing for a large number of bound levels as well as free states of a cesium atom. The total absorption rate is shown to be determined mainly by the bound-to-bound transitions for deep bound levels and by bound-to-free transitions for shallow bound levels. Moreover, the phonon emission and absorption processes can be orders of magnitude larger for deep bound levels as compared to the shallow bound ones. We also study various types of transitions from free states. We show that, for thermal atomic cesium with temperature in the range from 100 $\mu$K to 400 $\mu$K in the vicinity of a silica surface with temperature of 300 K, the adsorption (free-to-bound decay) rate is about two times larger than the heating (free-to-free upward decay) rate, while the cooling (free-to-free downward decay) rate is negligible.

0704.0341

Boris Ermolaev

B.I. Ermolaev, M. Greco, S.I. Troyan

Infrared Evolution Equations: Method and Applications

Talk given at Cracow Epiphany conference on precision physics and Monte Carlos for LHS. 4-6 January 2007, Cracow, Poland. 12 pp, 3 figures.

Acta Phys.Polon.B38:2243-2260,2007

hep-ph

It is a brief review on composing and solving Infrared Evolution Equations. They can be used in order to calculate amplitudes of high-energy reactions in different kinematic regions in the double-logarithmic approximation.

0704.0342

Patrice Ntumba Pungu

B. Dugmore and PP. Ntumba

Cofibrations in the Category of Frolicher Spaces. Part I

27 pages

math.AT

Cofibrations are defined in the category of Fr\"olicher spaces by weakening the analog of the classical definition to enable smooth homotopy extensions to be more easily constructed, using flattened unit intervals. We later relate smooth cofibrations to smooth neighborhood deformation retracts. The notion of smooth neighborhood deformation retract gives rise to an analogous result that a closed Fr\"olicher subspace $A$ of the Fr\"olicher space $X$ is a smooth neighborhood deformation retract of $X$ if and only if the inclusion $i: A\hookrightarrow X$ comes from a certain subclass of cofibrations. As an application we construct the right Puppe sequence.

0704.0343

J\"org Baumgartl

J\"org Baumgartl, Roel P.A. Dullens, Marjolein Dijkstra, Roland Roth and Clemens Bechinger

Experimental observation of structural crossover in binary mixtures of colloidal hard spheres

4 pages, 4 figures

Phys. Rev. Lett. 98, 198303 (2007)

10.1103/PhysRevLett.98.198303

cond-mat.soft cond-mat.dis-nn

Using confocal-microscopy we investigate the structure of binary mixtures of colloidal hard spheres with size ratio q=0.61. As a function of the packing fraction of the two particle species, we observe a marked change of the dominant wavelength in the pair correlation function. This behavior is in excellent agreement with a recently predicted structural crossover in such mixtures. In addition, the repercussions of structural crossover on the real-space structure of a binary fluid are analyzed. We suggest a relation between crossover and the lateral extension of networks containing only equally sized particles that are connected by nearest neighbor bonds. This is supported by Monte-Carlo simulations which are performed at different packing fractions and size ratios.

0704.0344

Fabrizio Tavecchio

L. Maraschi, G. Ghisellini, F. Tavecchio

The Blazar Spectral Sequence and GLAST

3 pages, 4 figures. Proceedings of the First GLAST Symposium, to be published

AIP Conf.Proc.921:160-162,2007

10.1063/1.2757292

astro-ph

The present status and understanding of the "spectral sequence" of blazars is discussed in the perspective of the upcoming GLAST launch. The vast improvement in sensitivity will allow to i) determine more objectively the "average" gamma-ray properties of classes objects ii) probe more deeply the ratio between accretion power and jet power in different systems.

0704.0345

Bing Wang

Bing Wang, Beom Jun Kim

A High Robustness and Low Cost Model for Cascading Failures

5 pages, 5 figures, accepted by EPL

EPL, 78(2007)48001

10.1209/0295-5075/78/48001

physics.soc-ph

We study numerically the cascading failure problem by using artificially created scale-free networks and the real network structure of the power grid. The capacity for a vertex is assigned as a monotonically increasing function of the load (or the betweenness centrality). Through the use of a simple functional form with two free parameters, revealed is that it is indeed possible to make networks more robust while spending less cost. We suggest that our method to prevent cascade by protecting less vertices is particularly important for the design of more robust real-world networks to cascading failures.

0704.0346

Kenji Hamaguchi

Kenji Hamaguchi, the Suzaku Eta Carinae team and the Carinae D-1 team

Diffuse X-ray Emission from the Carina Nebula Observed with Suzaku

4 pages, 2 figures, proceeding of the extreme universe in the Suzaku era, held in Kyoto, Japan on Dec. 4-8, 2006

10.1143/PTPS.169.174

astro-ph

A number of giant HII regions are associated with soft diffuse X-ray emission. Among these, the Carina nebula possesses the brightest soft diffuse emission. The required plasma temperature and thermal energy can be produced by collisions or termination of fast winds from main-sequence or embedded young O stars, but the extended emission is often observed from regions apart from massive stellar clusters. The origin of the X-ray emission is unknown. The XIS CCD camera onboard Suzaku has the best spectral resolution for extended soft sources so far, and is therefore capable of measuring key emission lines in the soft band. Suzaku observed the core and the eastern side of the Carina nebula (Car-D1) in 2005 Aug and 2006 June, respectively. Spectra of the south part of the core and Car-D1 similarly showed strong L-shell lines of iron ions and K-shell lines of silicon ions, while in the north of the core these lines were much weaker. Fitting the spectra with an absorbed thin-thermal plasma model showed kT~0.2, 0.6 keV and NH~1-2e21 cm-2 with a factor of 2-3 abundance variation in oxygen, magnesium, silicon and iron. The plasma might originate from an old supernova, or a super shell of multiple supernovae.

0704.0347

Hiroyuki Chihara

Hiroyuki Chihara

Resolvent estimates related with a class of dispersive equations

minor change, 20 pages, no figure, final version

math.AP math.CA

We present a simple proof of the resolvent estimates of elliptic Fourier multipliers on the Euclidean space, and apply them to the analysis of time-global and spatially-local smoothing estimates of a class of dispersive equations. For this purpose we study in detail the properties of the restriction of Fourier transform on the unit cotangent sphere associated with the symbols of multipliers.

0704.0348

Grazyna Stasinska

G. Stasinska

What can emission lines tell us?

55 pages, Lectures given at the XVIII Canary Island Winterschool "The emission line Universe", to be published by Cambridge University Press

10.1017/CBO9780511552038.003

astro-ph

1 Generalities 2 Empirical diagnostics based on emission lines 3 Photoionization modelling 4 Pending questions 5 Appendix: Lists of useful lines and how to deal with them

0704.0349

Ivan Izmestiev

Ivan Izmestiev

The Colin de Verdi\`ere number and graphs of polytopes

18 pages, 2 figures; reorganized; an estimate of the spectral gap added; the appendix on mixed volumes rewritten

math.CO math.MG

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

The Colin de Verdi\`ere number $\mu(G)$ of a graph $G$ is the maximum corank of a Colin de Verdi\`ere matrix for $G$ (that is, of a Schr\"odinger operator on $G$ with a single negative eigenvalue). In 2001, Lov\'asz gave a construction that associated to every convex 3-polytope a Colin de Verdi\`ere matrix of corank 3 for its 1-skeleton. We generalize the Lov\'asz construction to higher dimensions by interpreting it as minus the Hessian matrix of the volume of the polar dual. As a corollary, $\mu(G) \ge d$ if $G$ is the 1-skeleton of a convex $d$-polytope. Determination of the signature of the Hessian of the volume is based on the second Minkowski inequality for mixed volumes and on Bol's condition for equality.

0704.0350

Sonia Fornasier

S. Fornasier, E. Dotto, O. Hainaut, F. Marzari, H. Boehnhardt, F. De Luise, M. A. Barucci

Visible spectroscopic and photometric survey of Jupiter Trojans: final results on dynamical families

52 pages, 14 figure, paper accepted for publication in Icarus

10.1016/j.icarus.2007.03.033

astro-ph

We present the results of a visible spectroscopic and photometric survey of Jupiter Trojans belonging to different dynamical families carried out at the ESO-NTT telescope. We obtained data on 47 objects, 23 belonging to the L5 swarm and 24 to the L4 one. These data together with those already published by Fornasier et al. (2004a) and Dotto et al. (2006), constitute a total sample of visible spectra for 80 objects. The survey allows us to investigate six families (Aneas, Anchises, Misenus, Phereclos, Sarpedon, Panthoos) in the L5 cloud and four L4 families (Eurybates, Menelaus, 1986 WD and 1986 TS6). The sample that we measured is dominated by D--type asteroids, with the exception of the Eurybates family in the L4 swarm, where there is a dominance of C- and P-type asteroids. All the spectra that we obtained are featureless with the exception of some Eurybates members, where a drop--off of the reflectance is detected shortward of 5200 A. Similar features are seen in main belt C-type asteroids and commonly attributed to the intervalence charge transfer transition in oxidized iron. Our sample comprises fainter and smaller Trojans as compared to the literature's data and allows us to investigate the properties of objects with estimated diameter smaller than 40--50 km. The analysis of the spectral slopes and colors versus the estimated diameters shows that the blue and red objects have indistinguishable size distribution. We perform a statistical investigation of the Trojans's spectra property distributions as a function of their orbital and physical parameters, and in comparison with other classes of minor bodies in the outer Solar System. Trojans at lower inclination appear significantly bluer than those at higher inclination, but this effect is strongly driven by the Eurybates family.

0704.0351

Andrzej Marecki

Magdalena Kunert-Bajraszewska (1), Andrzej Marecki (1),((1) Torun Centre for Astronomy, N. Copernicus University, Torun)

FIRST-based survey of Compact Steep Spectrum sources, V. Milliarcsecond-scale morphology of CSS objects

14 pages, 10 figures, matches the version appearing in Astronomy & Astrophysics

10.1051/0004-6361:20066364

astro-ph

Multifrequency VLBA observations of the final group of ten objects in a sample of FIRST-based compact steep spectrum (CSS) sources are presented. The sample was selected to investigate whether objects of this kind could be relics of radio-loud AGNs switched off at very early stages of their evolution or possibly to indicate intermittent activity. Initial observations were made using MERLIN at 5 GHz. The sources have now been observed with the VLBA at 1.7, 5 and 8.4 GHz in a snapshot mode with phase-referencing. The resulting maps are presented along with unpublished 8.4-GHz VLA images of five sources. Some of the sources discussed here show a complex radio morphology and therefore a complicated past that, in some cases, might indicate intermittent activity. One of the sources studied - 1045+352 - is known as a powerful radio and infrared-luminous broad absorption line (BAL) quasar. It is a young CSS object whose asymmetric two-sided morphology on a scale of several hundred parsecs, extending in two different directions, may suggest intermittent activity. The young age and compact structure of 1045+352 is consistent with the evolution scenario of BAL quasars. It has also been confirmed that the submillimetre flux of 1045+352 can be seriously contaminated by synchrotron emission.

0704.0352

Jaba Chigvinadze G

J.G. Chigvinadze, J.V. Acrivos, S.M. Ashimov, A.A. Iashvili, T. V. Machaidze, Th. Wolf

Investigation of relaxation phenomena in high-temperature superconductors HoBa2Cu3O7-d at the action of pulsed magnetic fields

6 pages, 0 figures

10.1016/j.physleta.2007.06.035

cond-mat.soft cond-mat.supr-con

It is used the mechanical method of Abrikosov vortex stimulated dynamics investigation in superconductors. With its help it was studied relaxation phenomena in vortex matter of high-temperature superconductors. It established that pulsed magnetic fields change the course of relaxation processes taking place in vortex matter. The study of the influence of magnetic pulses differing by their durations and amplitudes on vortex system of isotropic high-temperature superconductors system HoBa2Cu3O7-d showed the presence of threshold phenomena. The small duration pulses does not change the course of relaxation processes taking place in vortex matter. When the duration of pulses exceeds some critical value (threshold), then their influence change the course of relaxation process which is revealed by stepwise change of relaxing mechanical moment . These investigations showed that the time for formatting of Abrikosov vortex lattice in HoBa2Cu3O7-d is of the order of 20 microsec. which on the order of value exceeds the time necessary for formation of a single vortex observed in type II superconductors.

0704.0353

Pedro Alberto

P. Alberto, A. S. de Castro, M. Malheiro

Spin and pseudospin symmetries and the equivalent spectra of relativistic spin-1/2 and spin-0 particles

5 pages, uses revtex macros

Phys.Rev.C75:047303,2007

10.1103/PhysRevC.75.047303

nucl-th quant-ph

We show that the conditions which originate the spin and pseudospin symmetries in the Dirac equation are the same that produce equivalent energy spectra of relativistic spin-1/2 and spin-0 particles in the presence of vector and scalar potentials. The conclusions do not depend on the particular shapes of the potentials and can be important in different fields of physics. When both scalar and vector potentials are spherical, these conditions for isospectrality imply that the spin-orbit and Darwin terms of either the upper component or the lower component of the Dirac spinor vanish, making it equivalent, as far as energy is concerned, to a spin-0 state. In this case, besides energy, a scalar particle will also have the same orbital angular momentum as the (conserved) orbital angular momentum of either the upper or lower component of the corresponding spin-1/2 particle. We point out a few possible applications of this result.

0704.0354

Dmitry I. Podolsky

D. Podolsky

General asymptotic solutions of the Einstein equations and phase transitions in quantum gravity

8 pages; reference added, acknoledgement added

HIP-2007-17/TH

hep-th gr-qc

We discuss generic properties of classical and quantum theories of gravity with a scalar field which are revealed at the vicinity of the cosmological singularity. When the potential of the scalar field is exponential and unbounded from below, the general solution of the Einstein equations has quasi-isotropic asymptotics near the singularity instead of the usual anisotropic Belinskii - Khalatnikov - Lifshitz (BKL) asymptotics. Depending on the strength of scalar field potential, there exist two phases of quantum gravity with scalar field: one with essentially anisotropic behavior of field correlation functions near the cosmological singularity, and another with quasi-isotropic behavior. The ``phase transition'' between the two phases is interpreted as the condensation of gravitons.

0704.0355

Christine Ducourant

C. Ducourant, R. Teixeira, N.C. Hambly, B. R. Oppenheimer, M.R.S. Hawkins, M. Rapaport, J. Modolo, J.F. Lecampion

Trigonometric parallaxes of high velocity halo white dwarf candidates

10.1051/0004-6361:20066876

Accepted (12/03/2007) for publication in A&A main journal

astro-ph

The status of 38 halo white dwarf candidates identified by Oppenheimer et al. (2001) has been intensively discussed by various authors. In analyses undertaken to date, trigonometric parallaxes are crucial missing data. Distance measurements are mandatory to kinematically segregate halo object from disk objects and hence enable a more reliable estimate of the local density of halo dark matter residing in such objects. We present trigonometric parallax measurements for 15 candidate halo white dwarfs (WDs) selected from the Oppenheimer et al. (2001) list. We observed the stars using the ESO 1.56-m Danish Telescope and ESO 2.2-m telescope from August 2001 to July 2004. Parallaxes with accuracies of 1--2 mas were determined yielding relative errors on distances of $\sim5$% for 6 objects, $\sim12$% for 3 objects, and $\sim20$% for two more objects. Four stars appear to be too distant (probably farther than 100 pc) to have measurable parallaxes in our observations. Distances, absolute magnitudes and revised space velocities were derived for the 15 halo WDs from the Oppenheimer et al. (2001) list. Halo membership is confirmed unambiguously for 6 objects while 5 objects may be thick disk members and 4 objects are too distant to draw any conclusion based solely on kinematics. Comparing our trigonometric parallaxes with photometric parallaxes used in previous work reveals an overestimation of distance as derived from photometric techniques. This new data set can be used to revise the halo white dwarf space density, and that analysis will be presented in a subsequent publication.

0704.0356

Pablo Cerd\'a-Dur\'an

Pablo Cerd\'a-Dur\'an, Vicent Quilis, Jos\'e A. Font

AMR simulations of the low T/|W| bar-mode instability of neutron stars

20 pages, 9 figures, accepted for publication in Computer Physics Communications.

Comput.Phys.Commun.177:288-297,2007

10.1016/j.cpc.2007.04.001

astro-ph

It has been recently argued through numerical work that rotating stars with a high degree of differential rotation are dynamically unstable against bar-mode deformation, even for values of the ratio of rotational kinetic energy to gravitational potential energy as low as O(0.01). This may have implications for gravitational wave astronomy in high-frequency sources such as core collapse supernovae. In this paper we present high-resolution simulations, performed with an adaptive mesh refinement hydrodynamics code, of such low T/|W| bar-mode instability. The complex morphological features involved in the nonlinear dynamics of the instability are revealed in our simulations, which show that the excitation of Kelvin-Helmholtz-like fluid modes outside the corotation radius of the star leads to the saturation of the bar-mode deformation. While the overall trends reported in an earlier investigation are confirmed by our work, we also find that numerical resolution plays an important role during the long-term, nonlinear behaviour of the instability, which has implications on the dynamics of rotating stars and on the attainable amplitudes of the associated gravitational wave signals.

0704.0357

Gergely J Sz\"oll\H{o}si

Gergely J Szollosi and Imre Derenyi

Evolutionary games on minimally structured populations

Supporting information available as EPAPS Document No. E-PLEEE8-78-144809 at http://ftp.aip.org/epaps/phys_rev_e/E-PLEEE8-78-144809/

PHYSICAL REVIEW E 78, 031919 (2008)

10.1103/PhysRevE.78.031919

q-bio.PE q-bio.OT

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Population structure induced by both spatial embedding and more general networks of interaction, such as model social networks, have been shown to have a fundamental effect on the dynamics and outcome of evolutionary games. These effects have, however, proved to be sensitive to the details of the underlying topology and dynamics. Here we introduce a minimal population structure that is described by two distinct hierarchical levels of interaction. We believe this model is able to identify effects of spatial structure that do not depend on the details of the topology. We derive the dynamics governing the evolution of a system starting from fundamental individual level stochastic processes through two successive meanfield approximations. In our model of population structure the topology of interactions is described by only two parameters: the effective population size at the local scale and the relative strength of local dynamics to global mixing. We demonstrate, for example, the existence of a continuous transition leading to the dominance of cooperation in populations with hierarchical levels of unstructured mixing as the benefit to cost ratio becomes smaller then the local population size. Applying our model of spatial structure to the repeated prisoner's dilemma we uncover a novel and counterintuitive mechanism by which the constant influx of defectors sustains cooperation. Further exploring the phase space of the repeated prisoner's dilemma and also of the "rock-paper-scissor" game we find indications of rich structure and are able to reproduce several effects observed in other models with explicit spatial embedding, such as the maintenance of biodiversity and the emergence of global oscillations.

0704.0358

Paride Paradisi

Paride Paradisi

Flavor Physics in SUSY at large tan(beta)

Proceedings of the Workshop CKM2006, 12-16 December, Nagoya (Japan). 4 pages, 2 figures.

hep-ph

We discuss the phenomenological impact of a particularly interesting corner of the MSSM: the large tan(beta) regime. The capabilities of leptonic and hadronic Flavor Violating processes in shedding light on physics beyond the Standard Model are reviewed. Moreover, we show that tests of Lepton Universality in charged current processes can represent an interesting handle to obtain relevant information on New Physics scenarios.

0704.0359

Hoang Hiep Pham

Nguyen Van Khue and Pham Hoang Hiep

Some properties of the complex Monge-Ampere operator in Cegrell's classes and applications

19 pages

math.CV

In this article we will first prove a result about convergence in capacity. Using the achieved result we will obtain a general decompositon theorem for complex Monge-Ampere measues which will be used to prove a comparison principle for the complex Monge-Ampere operator.

0704.0360

Zaqarashvili

T.V. Zaqarashvili and K Murawski

Torsional oscillations of longitudinally inhomogeneous coronal loops

6 pages, 3 figures, accepted in A&A

10.1051/0004-6361:20077246

astro-ph

We explore the effect of an inhomogeneous mass density field on frequencies and wave profiles of torsional Alfven oscillations in solar coronal loops. Dispersion relations for torsional oscillations are derived analytically in limits of weak and strong inhomogeneities. These analytical results are verified by numerical solutions, which are valid for a wide range of inhomogeneity strength. It is shown that the inhomogeneous mass density field leads to the reduction of a wave frequency of torsional oscillations, in comparison to that of estimated from mass density at the loop apex. This frequency reduction results from the decrease of an average Alfven speed as far as the inhomogeneous loop is denser at its footpoints. The derived dispersion relations and wave profiles are important for potential observations of torsional oscillations which result in periodic variations of spectral line widths. Torsional oscillations offer an additional powerful tool for a development of coronal seismology.

0704.0361

Ioannis Chatzigeorgiou

Ioannis Chatzigeorgiou, Miguel R. D. Rodrigues, Ian J. Wassell and Rolando Carrasco

Pseudo-random Puncturing: A Technique to Lower the Error Floor of Turbo Codes

5 pages, 1 figure, Proceedings of the 2007 IEEE International Symposium on Information Theory, Nice, France, June 24-29, 2007

10.1109/ISIT.2007.4557299

cs.IT math.IT

It has been observed that particular rate-1/2 partially systematic parallel concatenated convolutional codes (PCCCs) can achieve a lower error floor than that of their rate-1/3 parent codes. Nevertheless, good puncturing patterns can only be identified by means of an exhaustive search, whilst convergence towards low bit error probabilities can be problematic when the systematic output of a rate-1/2 partially systematic PCCC is heavily punctured. In this paper, we present and study a family of rate-1/2 partially systematic PCCCs, which we call pseudo-randomly punctured codes. We evaluate their bit error rate performance and we show that they always yield a lower error floor than that of their rate-1/3 parent codes. Furthermore, we compare analytic results to simulations and we demonstrate that their performance converges towards the error floor region, owning to the moderate puncturing of their systematic output. Consequently, we propose pseudo-random puncturing as a means of improving the bandwidth efficiency of a PCCC and simultaneously lowering its error floor.

0704.0362

Andrei Pronko G

F. Colomo and A.G. Pronko

The Arctic Circle Revisited

16 pages, 3 figures

Contemp. Math. 458 (2008) 361-376

math-ph hep-th math.MP

The problem of limit shapes in the six-vertex model with domain wall boundary conditions is addressed by considering a specially tailored bulk correlation function, the emptiness formation probability. A closed expression of this correlation function is given, both in terms of certain determinant and multiple integral, which allows for a systematic treatment of the limit shapes of the model for full range of values of vertex weights. Specifically, we show that for vertex weights corresponding to the free-fermion line on the phase diagram, the emptiness formation probability is related to a one-matrix model with a triple logarithmic singularity, or Triple Penner model. The saddle-point analysis of this model leads to the Arctic Circle Theorem, and its generalization to the Arctic Ellipses, known previously from domino tilings.

0704.0363

John H. Field

J.H.Field

Time and motion in physics: the Reciprocity Principle, relativistic invariance of the lengths of rulers and time dilatation

14 pages, 3 figures. v2 Important conceptual errors explained in Added Note. See also arXiv:0807.0158, arXiv:0809.4121. References added

physics.gen-ph

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Ponderable objects moving in free space according to Newton's First Law constitute both rulers and clocks when one such object is viewed from the rest frame of another. Together with the Reciprocity Principle this is used to demonstrate, in both Galilean and special relativity, the invariance of the measured length of a ruler in motion. The different times: `proper', `improper' and `apparent' appearing in different formulations of the relativistic time dilatation relation are discussed and exemplified by experimental applications. A non-intuitive `length expansion' effect predicted by the Reciprocity Principle as a necessary consequence of time dilatation is pointed out

0704.0364

Georges Vasseur

G. Vasseur

B --> rho K* decays and other rare vector-vector modes

4 pages, 8 figures, presented at the 4th International Workshop on the CKM Unitariry Triangle, Nagoya, Japan, December 12-16, 2006.

Preprint DAPNIA-06-601

hep-ex

The recent analyses of the following rare vector-vector decays of the B meson are presented: rho K*, omega K*, omega rho, omega omega, and omega phi charmless final states. The latest results indicate that the fraction of longitudinal polarization is about 0.5 in penguin-dominated modes and close to 1 for tree-dominated modes.

0704.0365

Jim Hague

J.P.Hague

Extending the theory of phonon-mediated superconductivity in quasi-2D

Reprint to improve access. 10 pages, 7 figures.

Lectures on the physics of highly correlated electron systems X, p255-264, AIP Conference Proceedings vol. 846 (2006)

cond-mat.supr-con cond-mat.str-el

I present results from an extended Migdal-Eliashberg theory of electron-phonon interactions and superconductivity. The history of the electron-phonon problem is introduced, and then study of the intermediate parameter regime is justified from the energy scales in the cuprate superconductors. The Holstein model is detailed, and limiting cases are examined to demonstrate the need for an extended theory of superconductivity. Results of the extended approximation are shown, including spectral functions and phase diagrams. These are discussed with reference to Hohenberg's theorem, the Bardeen-Cooper-Schrieffer theory and Coulomb repulsion.

0704.0366

Antonio J. Segui

Pablo Diaz, Antonio Segui

Generalized Nariai Solutions for Yang-type Monopoles

15 pages, 3 figures. References added, typos corrected and points clarified

Phys.Rev.D76:064033,2007

10.1103/PhysRevD.76.064033

gr-qc hep-th

A detailed study of the geometries that emerge by a gravitating generalized Yang monopole in even dimensions is carried out. In particular, those which present black hole and cosmological horizons. This two-horizon system is thermally unstable. The process of thermalization will drive both horizons to coalesce. This limit is what is profusely studied in this paper. It is shown that eventhough coordinate distance shrinks to zero, physical distance does not. So, there is some remaining space which geometry has been computed and identified as a generalized Nariai solution. The thermal properties of this new spacetime are then calculated. Topics, as the elliptical relation between radii of spheres in the geometry or a discussion about whether a mass-type term should be present in the line element or not, are also included.

0704.0367

Eyo Ita III

Eyo Eyo Ita III

Instanton representation of Plebanski gravity. Consistency of the initital value constraints under time evolution

16 pages

The Abraham Zelmanov Journal, 2011, Vol 4. (pages (96-114)

DAMTP-2007-32

gr-qc

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

The instanton representation of Plebanski gravity provides as equations of motion a Hodge self-duality condition and a set of `generalized' Maxwell's equations, subject to gravitational degrees of freedom encoded in the initial value constraints of general relativity. The main result of the present paper will be to prove that this constraint surface is preserved under time evolution. We carry this out not using the usual Dirac procedure, but rather the Lagrangian equations of motion themsleves. Finally, we provide a comparison with the Ashtekar formulation to place these results into overall context.

0704.0368

Alexej Pashkin

A. Pashkin, K. Thirunavukkuarasu, Y.-L. Mathis, W. Kang, and C. A. Kuntscher

Metal-insulator transition in the low-dimensional organic conductor (TMTSF)2FSO3 probed by infrared microspectroscopy

to appear in Eur. Phys. J. B

Eur. Phys. J. B 56, 285-290 (2007)

10.1140/epjb/e2007-00121-8

cond-mat.str-el

We present measurements of the infrared response of the quasi-one-dimensional organic conductor (TMTSF)2$SO3 along (E||a) and perpendicular (E||b') to the stacking axis as a function of temperature. Above the metal-insulator transition related to the anion ordering the optical conductivity spectra show a Drude-like response. Below the transition an energy gap of about 1500 cm-1 (185 meV) opens, leading to the corresponding charge transfer band in the optical conductivity spectra. The analysis of the infrared-active vibrations gives evidence for the long-range crystal structure modulation below the transition temperature and for the short-range order fluctuations of the lattice modulation above the transition temperature. Also we report about a new infrared mode at around 710 cm-1 with a peculiar temperature behavior, which has so far not been observed in any other (TMTSF)2X salt showing a metal-insulator transition. A qualitative model based on the coupling between the TMTSF molecule vibration and the reorientation of electrical dipole moment of the FSO3 anion is proposed, in order to explain the anomalous behavior of the new mode.

0704.0369

Tatsu Takeuchi

Minako Honda, Yee Kao, Naotoshi Okamura, Alexey Pronin, and Tatsu Takeuchi

The effect of Topcolor Assisted Technicolor, and other models, on Neutrino Oscillation

7 pages, latex, uses ws-procs9x6.cls; talk presented by Takeuchi at SCGT06, 21-24 November 2006, Nagoya, Japan

10.1142/9789812790750_0027

OCHA-PP-270, YITP-07-09, VPI-IPNAS-07-02

hep-ph

New physics beyond the Standard Model can lead to extra matter effects on neutrino oscillation if the new interactions distinguish among the three flavors of neutrino. In Ref.1, we argued that a long-baseline neutrino oscillation experiment in which the Fermilab-NUMI beam in its high-energy mode is aimed at the planned Hyper-Kamiokande detector would be capable of constraining the size of those extra matter effects, provided the vacuum value of \sin^2 2\theta_{23} is not too close to one. In this talk, we discuss how such a constraint would translate into limits on the coupling constants and masses of new particles in models such as topcolor assisted technicolor.

0704.0370

Julie Grollier

O. Boulle, V. Cros, J. Grollier, L. G. Pereira, C. Deranlot, F. Petroff, G. Faini, J. Barnas, A. Fert

Shaped angular dependence of the spin transfer torque and microwave generation without magnetic field

10.1038/nphys618

cond-mat.mtrl-sci

The generation of oscillations in the microwave frequency range is one of the most important applications expected from spintronics devices exploiting the spin transfer phenomenon. We report transport and microwave power measurements on specially designed nanopillars for which a non-standard angular dependence of the spin transfer torque (wavy variation) is predicted by theoretical models. We observe a new kind of current-induced dynamics that is characterized by large angle precessions in the absence of any applied field, as this is also predicted by simulation with such a wavy angular dependence of the torque. This type of non-standard nanopillars can represent an interesting way for the implementation of spin transfer oscillators since they are able to generate microwave oscillations without applied magnetic field. We also emphasize the theoretical implications of our results on the angular dependence of the torque.

0704.0371

Gilberto Medeiros Kremer

G. M. Kremer

Dark energy interacting with neutrinos and dark matter: a phenomenological theory

7 pages, 5 figures. To appear in GRG

Gen.Rel.Grav.39:965-972,2007

10.1007/s10714-007-0428-0

gr-qc

A model for a flat homogeneous and isotropic Universe composed of dark energy, dark matter, neutrinos, radiation and baryons is analyzed. The fields of dark matter and neutrinos are supposed to interact with the dark energy. The dark energy is considered to obey either the van der Waals or the Chaplygin equations of state. The ratio between the pressure and the energy density of the neutrinos varies with the red-shift simulating massive and non-relativistic neutrinos at small red-shifts and non-massive relativistic neutrinos at high red-shifts. The model can reproduce the expected red-shift behaviors of the deceleration parameter and of the density parameters of each constituent.

0704.0372

Luigi Delle Site

L.Delle Site

Levy-Lieb constrained-search formulation as a minimization of the correlation functional

9 pages, no figures

Journal of Physics A:Math.Theor.40, 2787 (2007)

10.1088/1751-8113/40/11/013

quant-ph

The constrained-search formulation of Levy and Lieb, which formally defines the exact Hohenberg-Kohn functional for any N-representable electron density, is here shown to be equivalent to the minimization of the correlation functional with respect to the N-1 conditional probability density, where N is number of electrons of the system. The consequences and implications of such a result are here analyzed and discussed via a practical example.

0704.0373

Shreecharan Tangirala

Utpal Roy, Suranjana Ghosh, T. Shreecharan, and Kaushik Bhattacharya

Reality of linear and angular momentum expectation values in bound states

18 pages

quant-ph hep-th

In quantum mechanics textbooks the momentum operator is defined in the Cartesian coordinates and rarely the form of the momentum operator in spherical polar coordinates is discussed. Consequently one always generalizes the Cartesian prescription to other coordinates and falls in a trap. In this work we introduce the difficulties one faces when the question of the momentum operator in spherical polar coordinate comes. We have tried to point out most of the elementary quantum mechanical results, related to the momentum operator, which has coordinate dependence. We explicitly calculate the momentum expectation values in various bound states and show that the expectation value really turns out to be zero, a consequence of the fact that the momentum expectation value is real. We comment briefly on the status of the angular variables in quantum mechanics and the problems related in interpreting them as dynamical variables. At the end, we calculate the Heisenberg's equation of motion for the radial component of the momentum for the Hydrogen atom.

0704.0374

Igor Kretinin

Boris A. Zon, Igor Yu. Kretinin

Gravity-induced electric polarization of matter and planetary magnetic fields

This paper has been withdrawn

physics.geo-ph

This paper has been withdrawn due to copyright reasons.

0704.0375

Denise Hagnier

Hadj-Ali Gueniche (DCPR), Pierre-Alexandre Glaude (DCPR), Guillaume Dayma (DCPR), Ren\'e Fournet (DCPR), Fr\'ed\'erique Battin-Leclerc (DCPR)

Rich methane premixed laminar flames doped by light unsaturated hydrocarbons - Part I : allene and propyne

Combustion and Flame 146 (2006) 620-634

10.1016/j.combustflame.2006.07.004

physics.chem-ph

The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of C3H4 was added, corresponding to a ratio C3H4/CH4 of 12% and an equivalence ratio of 1.55. The three flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz microprobe. Quantified species included carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, propane, 1,2-butadiene, 1,3-butadiene, 1-butene, isobutene, 1-butyne, vinylacetylene, and benzene. The temperature was measured using a PtRh (6%)-PtRh (30%) thermocouple settled inside the enclosure and ranged from 700 K close to the burner up to 1850 K. In order to model these new results, some improvements have been made to a mechanism previously developed in our laboratory for the reactions of C3-C4 unsaturated hydrocarbons. The main reaction pathways of consumption of allene and propyne and of formation of C6 aromatic species have been derived from flow rate analyses.

0704.0376

Daniele Parodi

Daniele Parodi, Maura Sassetti, Paolo Solinas, Nino Zangh\`i

Environmental noise reduction for holonomic quantum gates

7 pages, 2 figures, to appear in Phys. Rev. A

10.1103/PhysRevA.76.012337

quant-ph cond-mat.mes-hall

We study the performance of holonomic quantum gates, driven by lasers, under the effect of a dissipative environment modeled as a thermal bath of oscillators. We show how to enhance the performance of the gates by suitable choice of the loop in the manifold of the controllable parameters of the laser. For a simplified, albeit realistic model, we find the surprising result that for a long time evolution the performance of the gate (properly estimated in terms of average fidelity) increases. On the basis of this result, we compare holonomic gates with the so-called stimulated Raman adiabatic passage (STIRAP) gates.

0704.0377

Vladimir Pascalutsa

Daniele Binosi (ECT*, Trento), Vladimir Pascalutsa (ECT*, Trento & Mainz U.)

The lifetime of unstable particles in electromagnetic fields

11 pages, 3 figs; published version

J.Phys.G36:045001,2009

10.1088/0954-3899/36/4/045001

ECT*-07-08

hep-ph hep-th nucl-th

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

We show that the electromagnetic moments of unstable particles (resonances) have an absorptive contribution which quantifies the change of the particle's lifetime in an external electromagnetic field. To give an example we compute here the imaginary part of the magnetic moment for the cases of the muon and the neutron at leading order in the electroweak coupling. We also consider an analogous effect for the strongly-decaying $\Delta$(1232) resonance. The result for the muon is Im$ \mu = e G_F^2 m^3/768 \pi^3$, with $e$ the charge and $m$ the mass of the muon, $G_F$ the Fermi constant, which in an external magnetic field of $B$ Tesla give rise to the relative change in the muon lifetime of $3\times 10^{-15} B$. For neutron the effect is of a similar magnitude. We speculate on the observable implications of this effect.

0704.0378

Maurice Duits

Maurice Duits and Arno B.J. Kuijlaars

An equilibrium problem for the limiting eigenvalue distribution of banded Toeplitz matrices

28 pages; 7 figures

math.CV math.CA

We study the limiting eigenvalue distribution of $n\times n$ banded Toeplitz matrices as $n\to \infty$. From classical results of Schmidt-Spitzer and Hirschman it is known that the eigenvalues accumulate on a special curve in the complex plane and the normalized eigenvalue counting measure converges weakly to a measure on this curve as $n\to\infty$. In this paper, we characterize the limiting measure in terms of an equilibrium problem. The limiting measure is one component of the unique vector of measures that minimes an energy functional defined on admissible vectors of measures. In addition, we show that each of the other components is the limiting measure of the normalized counting measure on certain generalized eigenvalues.

0704.0379

Peter Virnau

P. Virnau, M. Kardar, and Y. Kantor

Capturing knots in polymers

2 pages, 4 figures

Chaos 15, 041103 (2005)

10.1063/1.2130690

cond-mat.soft cond-mat.stat-mech

This paper visualizes a knot reduction algorithm

0704.0380

J. W. Harris

Y. Git, J. W. Harris, S. C. Harris

Exponential growth rates in a typed branching diffusion

Published at http://dx.doi.org/10.1214/105051606000000853 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Annals of Applied Probability 2007, Vol. 17, No. 2, 609-653

10.1214/105051606000000853

IMS-AAP-AAP0219

math.PR

We study the high temperature phase of a family of typed branching diffusions initially studied in [Ast\'{e}risque 236 (1996) 133--154] and [Lecture Notes in Math. 1729 (2000) 239--256 Springer, Berlin]. The primary aim is to establish some almost-sure limit results for the long-term behavior of this particle system, namely the speed at which the population of particles colonizes both space and type dimensions, as well as the rate at which the population grows within this asymptotic shape. Our approach will include identification of an explicit two-phase mechanism by which particles can build up in sufficient numbers with spatial positions near $-\gamma t$ and type positions near $\kappa \sqrt{t}$ at large times $t$. The proofs involve the application of a variety of martingale techniques--most importantly a ``spine'' construction involving a change of measure with an additive martingale. In addition to the model's intrinsic interest, the methodologies presented contain ideas that will adapt to other branching settings. We also briefly discuss applications to traveling wave solutions of an associated reaction--diffusion equation.

0704.0381

Garry Angus

Garry W. Angus (St. Andrews), Stacy S. McGaugh (Maryland)

The collision velocity of the bullet cluster in conventional and modified dynamics

8 pages, 4 figures, 1 table, accepted for publication in MNRAS

10.1111/j.1365-2966.2007.12403.x

astro-ph

We consider the orbit of the bullet cluster 1E 0657-56 in both CDM and MOND using accurate mass models appropriate to each case in order to ascertain the maximum plausible collision velocity. Impact velocities consistent with the shock velocity (~ 4700km/s) occur naturally in MOND. CDM can generate collision velocities of at most ~ 3800km/s, and is only consistent with the data provided that the shock velocity has been substantially enhanced by hydrodynamical effects.

0704.0382

Gilles Z\'emor

Yahya Ould Hamidoune, Oriol Serra, Gilles Zemor

On Some Subgroup Chains Related to Kneser's Theorem

J. de Theorie des Nombres de Bordeaux, 20 (2008) 125--130

math.NT

A recent result of Balandraud shows that for every subset S of an abelian group G, there exists a non trivial subgroup H such that |TS| <= |T|+|S|-2 holds only if the stabilizer of TS contains H. Notice that Kneser's Theorem says only that the stabilizer of TS must be a non-zero subgroup. This strong form of Kneser's theorem follows from some nice properties of a certain poset investigated by Balandraud. We consider an analogous poset for nonabelian groups and, by using classical tools from Additive Number Theory, extend some of the above results. In particular we obtain short proofs of Balandraud's results in the abelian case.

0704.0383

Rajendra Prasad

Rajendra Prasad

The Exact Boundary Condition to Solve the Schrodinger Equation of Many Electron System

cond-mat.str-el

In an attempt to bypass the sign problem in quantum Monte Carlo simulation of electronic systems within the framework of fixed node approach, we derive the exclusion principle "Two electrons can't be at the same external isopotential surface simultaneously" using the first postulate of quantum mechanics. We propose the exact Coulomb-Exchange nodal surface i.e. the exact boundary condition to solve the non-relativistic Schrodinger equation for the non-degenerate ground state of atoms and molecules. This boundary condition was applied to compute the ground state energies of N, Ne, Li2, Be2, B2, C2, N2, O2, F2, and H2O systems using diffusion Monte Carlo method. The ground state energies thus obtained agree well with the exact estimate of non-relativistic energies.

0704.0384

Denis Artemenkov

D. A. Artemenkov, T. V. Shchedrina, R. Stanoeva, and P. I. Zarubin

Clustering features of $^9$Be, $^{14}$N, $^7$Be, and $^8$B nuclei in relativistic fragmentation

14 pages, 6 figures, 4 tables, International Symposium on Exotic Nuclei (EXON-2006), 17-22 July, 2006, Khanty-Mansiysk, Russia

AIPConf.Proc.912:78-87,2007

10.1063/1.2746582

nucl-ex

Recent studies of clustering in light nuclei with an initial energy above 1 A GeV in nuclear treack emulsion are overviewed. The results of investigations of the relativistic $^9$Be nuclei fragmentation in emulsion, which entails the production of He fragments, are presented. It is shown that most precise angular measurements provided by this technique play a crucial role in the restoration of the excitation spectrum of the $\alpha$ particle sysytem. In peripheral interactions $^9$Be nuclei are dissociated practically totally through the 0$^+$ and 2$^+$ states of the $^8$Be nucleus. The results of investigations of the dissociation of a $^{14}$N nucleus of momentum 2.86 A GeV/c in emulsion are presented as example of more complicated system. The momentum and correlation characteristics of $\alpha$ particles for the $^{14}$N$\to3\alpha+X$ channel in the laboratory system and the rest systems of 3$\alpha$ particles were considered in detail. Topology of charged fragments produced in peripheral relativistic dissociation of radioactive $^8$B, $^7$Be nuclei in emulsion is studied.

0704.0385

Magnus Ogren

M. Ogren and H. Heiselberg

Super-shell structures and pairing in ultracold trapped Fermi gases

4 pages, 2 figures.

Phys. Rev. A 76, 021601(R) (2007)

10.1103/PhysRevA.76.021601

cond-mat.other

We calculate level densities and pairing gaps for an ultracold dilute gas of fermionic atoms in harmonic traps under the influence of mean field and anharmonic quartic trap potentials. Super-shell structures, which were found in Hartree-Fock calculations, are calculated analytically within periodic orbit theory as well as from WKB calculations. For attractive interactions, the underlying level densities are crucial for pairing and super-shell structures in gaps are predicted.

0704.0386

Franck Laloe

Franck Lalo\"e (LKB - Lhomond), William J. Mullin (UMASS)

Quantum non-local effects with Bose-Einstein condensates

version published, with a shorter abstract to fit into the 9 lines of PRL, one more reference, and minor changes

Physical Review Letters 99 (2007) 150401

10.1103/PhysRevLett.99.150401

quant-ph cond-mat.other

We study theoretically the properties of two Bose-Einstein condensates in different spin states, represented by a double Fock state. Individual measurements of the spins of the particles are performed in transverse directions, giving access to the relative phase of the condensates. Initially, this phase is completely undefined, and the first measurements provide random results. But a fixed value of this phase rapidly emerges under the effect of the successive quantum measurements, giving rise to a quasi-classical situation where all spins have parallel transverse orientations. If the number of measurements reaches its maximum (the number of particles), quantum effects show up again, giving rise to violations of Bell type inequalities. The violation of BCHSH inequalities with an arbitrarily large number of spins may be comparable (or even equal) to that obtained with two spins.

0704.0387

Thomas Eisenbeiss

T. Eisenbeiss, A. Seifahrt, M. Mugrauer, T.O.B. Schmidt, R. Neuhaeuser, T. Roell

Low mass visual binaries in the solar neighbourhood: The case of HD141272

6 pages, 6 figures

10.1002/asna.200610770

astro-ph

We search for stellar and substellar companions of young nearby stars to investigate stellar multiplicity and formation of stellar and substellar companions. We detect common proper-motion companions of stars via multi-epoch imaging. Their companionship is finally confirmed with photometry and spectroscopy. Here we report the discovery of a new co-moving (13 sigma) stellar companion ~17.8 arcsec (350 AU in projected separation) north of the nearby star HD141272 (21 pc). With EMMI/NTT optical spectroscopy we determined the spectral type of the companion to be M3+-0.5V. The derived spectral type as well as the near infrared photometry of the companion are both fully consistent with a 0.26+-0.07 Msol dwarf located at the distance of HD141272 (21 pc). Furthermore the photometry data rules out the pre-main sequence status, since the system is consistent with the ZAMS of the Pleiades.

0704.0388

Pasquale Migliozzi Dr.

A. Donini, M. Maltoni, D. Meloni, P. Migliozzi, F. Terranova

Sterile neutrinos at the CNGS

Major modifications; new analysis after MiniBooNE data release: 21 pages, 5 figures

JHEP 0712:013,2007

10.1088/1126-6708/2007/12/013

hep-ph

We study the potential of the CNGS beam in constraining the parameter space of a model with one sterile neutrino separated from three active ones by an $\mathcal{O}(\eVq)$ mass-squared difference, $\Dmq_\Sbl$. We perform our analysis using the OPERA detector as a reference (our analysis can be upgraded including a detailed simulation of the ICARUS detector). We point out that the channel with the largest potential to constrain the sterile neutrino parameter space at the CNGS beam is $\nu_\mu \to \nu_\tau$. The reason for that is twofold: first, the active-sterile mixing angle that governs this oscillation is the less constrained by present experiments; second, this is the signal for which both OPERA and ICARUS have been designed, and thus benefits from an extremely low background. In our analysis we also took into account $\nu_\mu \to \nu_e$ oscillations. We find that the CNGS potential to look for sterile neutrinos is limited with nominal intensity of the beam, but it is significantly enhanced with a factor 2 to 10 increase in the neutrino flux. Data from both channels allow us, in this case, to constrain further the four-neutrino model parameter space. Our results hold for any value of $\Dmq_\Sbl \gtrsim 0.1 \eVq$, \textit{i.e.} when oscillations driven by this mass-squared difference are averaged. We have also checked that the bound on $\theta_{13}$ that can be put at the CNGS is not affected by the possible existence of sterile neutrinos.

0704.0389

Tanja Hinderer

Eanna E. Flanagan and Tanja Hinderer

Evolution of the Carter constant for inspirals into a black hole: effect of the black hole quadrupole

Typos found in sec. III, this version has the corrected expressions. An erratum is in press. 22 pages, added a paragraph to sec. V B; Erratum-ibid.D82:069904,2010; Erratum-ibid.D82:129903,2010

Phys.Rev.D75:124007,2007; Erratum-ibid.D82:069904,2010; Erratum-ibid.D82:129903,2010

10.1103/PhysRevD.75.124007 10.1103/PhysRevD.82.029901 10.1103/PhysRevD.82.129903

gr-qc

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

We analyze the effect of gravitational radiation reaction on generic orbits around a body with an axisymmetric mass quadrupole moment Q to linear order in Q, to the leading post-Newtonian order, and to linear order in the mass ratio. This system admits three constants of the motion in absence of radiation reaction: energy, angular momentum, and a third constant analogous to the Carter constant. We compute instantaneous and time-averaged rates of change of these three constants. For a point particle orbiting a black hole, Ryan has computed the leading order evolution of the orbit's Carter constant, which is linear in the spin. Our result, when combined with an interaction quadratic in the spin (the coupling of the black hole's spin to its own radiation reaction field), gives the next to leading order evolution. The effect of the quadrupole, like that of the linear spin term, is to circularize eccentric orbits and to drive the orbital plane towards antialignment with the symmetry axis. In addition we consider a system of two point masses where one body has a single mass multipole or current multipole. To linear order in the mass ratio, to linear order in the multipole, and to the leading post-Newtonian order, we show that there does not exist an analog of the Carter constant for such a system (except for the cases of spin and mass quadrupole). With mild additional assumptions, this result falsifies the conjecture that all vacuum, axisymmetric spacetimes posess a third constant of geodesic motion.

0704.0390

Serge Troubetzkoy

Serge Troubetzkoy (CPT, Iml, Frumam)

Dual billiards, Fagnano orbits and regular polygons

The American Mathematical Monthly 116 (2009) 251-260

math.DS

We study the notion of Fagnano orbits for dual polygonal billiards. We used them to characterize regular polygons and we study the iteration of the developing map.

0704.0391

Kozlov Gleb Gennadievich

G. G. Kozlov

Exactly solvable spin dynamics of an electron coupled to large number of nuclei and the electron-nuclear spin echo in a quantum dot

5 figures. submitted to JETP

10.1134/S1063776107100159

cond-mat.mes-hall

The model considered in the paper is used nowadays to describe spin dynamics of quantum dots after optical excitation. Based on the exact diagonalization of a model Hamiltonian, we solve the problems of the electron spin polarization decay and magnetic field dependence of the steady state polarization. The important role of the nuclear state is shown and methods of its calculation for different regimes of optical excitation are proposed. The effect of spin echo observed after application of the magnetic field $\pi$-pulse is predicted.

0704.0392

Marcus Kaiser

Marcus Kaiser, Robert Martin, Peter Andras and Malcolm P. Young

Simulation of Robustness against Lesions of Cortical Networks

submitted to European Journal of Neuroscience (under review)

European Journal of Neuroscience, 25:3185--3192, 2007

10.1111/j.1460-9568.2007.05574.x

q-bio.NC cond-mat.dis-nn physics.soc-ph

Structure entails function and thus a structural description of the brain will help to understand its function and may provide insights into many properties of brain systems, from their robustness and recovery from damage, to their dynamics and even their evolution. Advances in the analysis of complex networks provide useful new approaches to understanding structural and functional properties of brain networks. Structural properties of networks recently described allow their characterization as small-world, random (exponential) and scale-free. They complement the set of other properties that have been explored in the context of brain connectivity, such as topology, hodology, clustering, and hierarchical organization. Here we apply new network analysis methods to cortical inter-areal connectivity networks for the cat and macaque brains. We compare these corticocortical fibre networks to benchmark rewired, small-world, scale-free and random networks, using two analysis strategies, in which we measure the effects of the removal of nodes and connections on the structural properties of the cortical networks. The brain networks' structural decay is in most respects similar to that of scale-free networks. The results implicate highly connected hub-nodes and bottleneck connections as structural basis for some of the conditional robustness of brain systems. This informs the understanding of the development of brain networks' connectivity.

0704.0393

Shaun Hendy

S. C. Hendy

A thermodynamic model for the melting of supported metal nanoparticles

7 pages, 2 figures

Nanotechnology 18, 175703 (2007).

10.1088/0957-4484/18/17/175703

cond-mat.mtrl-sci

We construct a simple thermodynamic model to describe the melting of a supported metal nanoparticle with a spherically curved free surface both with and without surface melting. We use the model to investigate the results of recent molecular dynamics simulations, which suggest the melting temperature of a supported metal particle is the same as that of a free spherical particle with the same surface curvature. Our model shows that this is only the case when the contact angles of the supported solid and liquid particles are similar. This is also the case for the temperature at which surface melting begins.

0704.0394

Anna Ja\'{s}kiewicz

Anna Ja\'skiewicz

Average optimality for risk-sensitive control with general state space

Published at http://dx.doi.org/10.1214/105051606000000790 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Annals of Applied Probability 2007, Vol. 17, No. 2, 654-675

10.1214/105051606000000790

IMS-AAP-AAP410

q-fin.RM math.PR

This paper deals with discrete-time Markov control processes on a general state space. A long-run risk-sensitive average cost criterion is used as a performance measure. The one-step cost function is nonnegative and possibly unbounded. Using the vanishing discount factor approach, the optimality inequality and an optimal stationary strategy for the decision maker are established.

0704.0395

Zhenjun Xiao

Xin Liu, Zhen-Jun Xiao, and Hui-Sheng Wang

A Study of $B_{d}^0 \to J/\Psi \eta^{(\prime)}$ Decays in the pQCD Approach

10 pages, 1 ps figure, Revtex

ZJOU-PHY-TH-07-02, NJNU-TH-07-11

hep-ph

Motivated by the very recent measurement of the branching ratio of ${B_d^0} \to J/\psi \eta$ decay, we calculate the branching ratios of ${B_d}^0 \to J/\psi \eta$ and ${B_d}^0 \to J/\Psi \eta'$ decays in the perturbative QCD (pQCD) approach. The pQCD predictions for the branching ratios of considered decays are: $BR(B_d^0 \to J/\Psi \eta) = (1.96 ^{+9.68}_{-0.65}) \times 10^{-6}$, which is consistent with the first experimental measurement within errors; while $BR(B_d^0 \to J/\Psi \eta') = (1.09 ^{+3.76}_{-0.25}) \times 10^{-6}$, very similar with $B_d^0 \to \jpsi \eta$ decay and can be tested by the forthcoming LHC experiments. The measurements of these decay channels may help us to understand the QCD dynamics in the corresponding energy scale, especially the reliability of pQCD approach to these kinds of B meson decays.

0704.0396

Min-Chul Cha

Min-Chul Cha and Ji-Woo Lee

Finite-temperature phase transitions in a two-dimensional boson Hubbard model

4 pages, 7 figures

10.1103/PhysRevLett.98.266406

cond-mat.str-el

We study finite-temperature phase transitions in a two-dimensional boson Hubbard model with zero-point quantum fluctuations via Monte Carlo simulations of quantum rotor model, and construct the corresponding phase diagram. Compressibility shows a thermally activated gapped behavior in the insulating regime. Finite-size scaling of the superfluid stiffness clearly shows the nature of the Kosterlitz-Thouless transition. The transition temperature, $T_c$, confirms a scaling relation $T_c \propto \rho_0^x$ with $x=1.0$. Some evidences of anomalous quantum behavior at low temperatures are presented.

0704.0397

Anne Ersbak Bang Nielsen

Anne E. B. Nielsen and Klaus Molmer

Conditional generation of path-entangled optical NOON states

7 pages, 5 figures, v2: added references and minor changes

Phys. Rev. A 75, 063803 (2007)

10.1103/PhysRevA.75.063803

quant-ph

We propose a measurement protocol to generate path-entangled NOON states conditionally from two pulsed type II optical parametric oscillators. We calculate the fidelity of the produced states and the success probability of the protocol. The trigger detectors are assumed to have finite dead time, and for short pulse trigger fields they are modeled as on/off detectors with finite efficiency. Continuous-wave operation of the parametric oscillators is also considered.

0704.0398

Rudolf Gr\"{u}bel

Florian Dennert, Rudolf Gr\"ubel

Renewals for exponentially increasing lifetimes, with an application to digital search trees

Published at http://dx.doi.org/10.1214/105051606000000862 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Annals of Applied Probability 2007, Vol. 17, No. 2, 676-687

10.1214/105051606000000862

IMS-AAP-AAP412

math.PR

We show that the number of renewals up to time $t$ exhibits distributional fluctuations as $t\to\infty$ if the underlying lifetimes increase at an exponential rate in a distributional sense. This provides a probabilistic explanation for the asymptotics of insertion depth in random trees generated by a bit-comparison strategy from uniform input; we also obtain a representation for the resulting family of limit laws along subsequences. Our approach can also be used to obtain rates of convergence.

0704.0399

Gerard Clement

G. Clement, J.C. Fabris and G.T. Marques

Hawking radiation of linear dilaton black holes

9 pages

Phys.Lett.B651:54-57,2007

10.1016/j.physletb.2007.05.052

LAPTH-1178/07

gr-qc hep-th

We compute exactly the semi-classical radiation spectrum for a class of non-asymptotically flat charged dilaton black holes, the so-called linear dilaton black holes. In the high frequency regime, the temperature for these black holes generically agrees with the surface gravity result. In the special case where the black hole is massless, we show that, although the surface gravity remains finite, there is no radiation, in agreement with the fact that massless objects cannot radiate.

0704.0400

Niklas Beisert

Niklas Beisert

The S-Matrix of AdS/CFT and Yangian Symmetry

12 pages, contributed to the Solvay workshop "Bethe Ansatz: 75 Years Later", v2: references added, v3: wording changed, v4: factor 1/2 for Delta C hat corrected in tab 2 (thanks to F. Spill)

PoS Solvay:002,2006

AEI-2007-019

nlin.SI cond-mat.stat-mech hep-th

We review the algebraic construction of the S-matrix of AdS/CFT. We also present its symmetry algebra which turns out to be a Yangian of the centrally extended su(2|2) superalgebra.