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Submitter: Sebastien Forget
Authors: Sebastien Chenais (LCFIO, LPL), Frederic Druon (LCFIO), Sebastien
Forget (LCFIO, LPL), Francois Balembois (LCFIO), Patrick Georges (LCFIO)
Title: On thermal effects in solid state lasers: the case of ytterbium-doped
materials
Abstract: A review of theoretical and experimental studies of thermal effects in
solid-state lasers is presented, with a special focus on diode-pumped
ytterbium-doped materials. A large part of this review provides however general
information applicable to any kind of solid-state laser. Our aim here is not to
make a list of the techniques that have been used to minimize thermal effects,
but instead to give an overview of the theoretical aspects underneath, and give
a state-of-the-art of the tools at the disposal of the laser scientist to
measure thermal effects. After a presentation of some general properties of
Yb-doped materials, we address the issue of evaluating the temperature map in
Yb-doped laser crystals, both theoretically and experimentally. This is the
first step before studying the complex problem of thermal lensing (part III).
We will focus on some newly discussed aspects, like the definition of the
thermo-optic coefficient: we will highlight some misleading interpretations of
thermal lensing experiments due to the use of the dn/dT parameter in a context
where it is not relevant. Part IV will be devoted to a state-of-the-art of
experimental techniques used to measure thermal lensing. Eventually, in part V,
we will give some concrete examples in Yb-doped materials, where their
peculiarities will be pointed out.
Journal: Progress in quantum electronics 30 (12/2006) 89-126 |
Submitter: Wang Jian
Authors: Jian Wang and Jian-Sheng Wang
Title: Dimensional crossover of thermal conductance in nanowires
Abstract: Dimensional dependence of thermal conductance at low temperatures in
nanowires is studied using the nonequilibrium Green's function (NEGF) method.
Our calculation shows a smooth dimensional crossover of thermal conductance in
nanowire from one-dimensional to three-dimensional behavior with the increase
of diameters. The results are consistent with the experimental findings that
the temperature dependence of thermal conductance at low temperature for
diameters from tens to hundreds nanometers will be close to Debye law. The
calculation also suggests that universal thermal conductance is only observable
in nanowires with small diameters. We also find that the interfacial thermal
conductance across Si and Ge nanowire is much lower than the corresponding
value in bulk materials.
Journal: None |
Submitter: Ga\"etan L\'ev\^eque
Authors: Gaetan Leveque, Olivier J. F. Martin, John Weiner
Title: Transient behavior of surface plasmon polaritons scattered at a
subwavelength groove
Abstract: We present a numerical study and analytical model of the optical near-field
diffracted in the vicinity of subwavelength grooves milled in silver surfaces.
The Green's tensor approach permits computation of the phase and amplitude
dependence of the diffracted wave as a function of the groove geometry. It is
shown that the field diffracted along the interface by the groove is equivalent
to replacing the groove by an oscillating dipolar line source. An analytic
expression is derived from the Green's function formalism, that reproduces well
the asymptotic surface plasmon polariton (SPP) wave as well as the transient
surface wave in the near-zone close to the groove. The agreement between this
model and the full simulation is very good, showing that the transient
"near-zone" regime does not depend on the precise shape of the groove. Finally,
it is shown that a composite diffractive evanescent wave model that includes
the asymptotic SPP can describe the wavelength evolution in this transient
near-zone. Such a semi-analytical model may be useful for the design and
optimization of more elaborate photonic circuits whose behavior in large part
will be controlled by surface waves.
Journal: None |
Submitter: Max-K. von Renesse
Authors: Max-K von Renesse, Karl-Theodor Sturm
Title: Entropic Measure and Wasserstein Diffusion
Abstract: We construct a new random probability measure on the sphere and on the unit
interval which in both cases has a Gibbs structure with the relative entropy
functional as Hamiltonian. It satisfies a quasi-invariance formula with respect
to the action of smooth diffeomorphism of the sphere and the interval
respectively. The associated integration by parts formula is used to construct
two classes of diffusion processes on probability measures (on the sphere or
the unit interval) by Dirichlet form methods. The first one is closely related
to Malliavin's Brownian motion on the homeomorphism group. The second one is a
probability valued stochastic perturbation of the heat flow, whose intrinsic
metric is the quadratic Wasserstein distance. It may be regarded as the
canonical diffusion process on the Wasserstein space.
Journal: None |
Submitter: Bart Van Overmeire
Authors: B. Van Overmeire, J. Ryckebusch
Title: Second-Order Eikonal Corrections for A(e,e'p)
Abstract: The first-order eikonal approximation is frequently adopted in interpreting
the results of $A(e,e'p)$ measurements. Glauber calculations, for example,
typically adopt the first-order eikonal approximation. We present an extension
of the relativistic eikonal approach to $A(e,e'p)$ which accounts for
second-order eikonal corrections. The numerical calculations are performed
within the relativistic optical model eikonal approximation. The nuclear
transparency results indicate that the effect of the second-order eikonal
corrections is rather modest, even at $Q^{2} \approx 0.2$ (GeV/c)$^2$. The same
applies to polarization observables, left-right asymmetries, and differential
cross sections at low missing momenta. At high missing momenta, however, the
second-order eikonal corrections are significant and bring the calculations in
closer agreement with the data and/or the exact results from models adopting
partial-wave expansions.
Journal: Phys.Lett.B650:337-343,2007 |
Submitter: Bon-Chul Koo
Authors: Bon-Chul Koo, Ho-Gyu Lee, Dae-Sik Moon, Jae-Joon Lee, Ji Yeon Seok,
Hyung Mok Lee, Seung Soo Hong, Myung Gyoon Lee, Hidehiro Kaneda, Yoshifusa
Ita, Woong-Seob Jeong, Takashi Onaka, Itsuki Sakon, Takao Nakagawa, Hiroshi
Murakami
Title: AKARI Detection of the Infrared-Bright Supernova Remnant B0104-72.3 in
the Small Magellanic Cloud
Abstract: We present a serendipitous detection of the infrared-bright supernova remnant
(SNR) B0104-72.3 in the Small Magellanic Cloud by the Infrared Camera (IRC)
onboard AKARI. An elongated, partially complete shell is detected in all four
observed IRC bands covering 2.6-15 um. The infrared shell surrounds radio,
optical, and X-ray emission associated with the SNR and is probably a radiative
SNR shell. This is the first detection of a SNR shell in this near/mid-infrared
waveband in the Small Magellanic Cloud. The IRC color indicates that the
infrared emission might be from shocked H2 molecules with some possible
contributions from ionic lines. We conclude that B0104-72.3 is a middle-aged
SNR interacting with molecular clouds, similar to the Galactic SNR IC 443. Our
results highlight the potential of AKARI IRC observations in studying SNRs,
especially for diagnosing SNR shocks.
Journal: None |
Submitter: Patrick Warren
Authors: Patrick B. Warren
Title: Flory-Huggins theory for the solubility of heterogeneously-modified
polymers
Abstract: Many water soluble polymers are chemically modified versions of insoluble
base materials such as cellulose. A Flory-Huggins model is solved to determine
the effects of heterogeneity in modification on the solubility of such
polymers. It is found that heterogeneity leads to decreased solubility, with
the effect increasing with increasing blockiness. In the limit of extreme
blockiness, the nature of the phase coexistence crosses over to a
polymer-polymer demixing transition. Some consequences are discussed for the
synthesis of partially modified polymers, and the experimental characterisation
of such systems.
Journal: None |
Submitter: Marc Dambrine
Authors: Lekbir Afraites (LMAC), Marc Dambrine (LMAC), Djalil Kateb (LMAC)
Title: On second order shape optimization methods for electrical impedance
tomography
Abstract: This paper is devoted to the analysis of a second order method for recovering
the \emph{a priori} unknown shape of an inclusion $\omega$ inside a body
$\Omega$ from boundary measurement. This inverse problem - known as electrical
impedance tomography - has many important practical applications and hence has
focussed much attention during the last years. However, to our best knowledge,
no work has yet considered a second order approach for this problem. This paper
aims to fill that void: we investigate the existence of second order derivative
of the state $u$ with respect to perturbations of the shape of the interface
$\partial\omega$, then we choose a cost function in order to recover the
geometry of $\partial \omega$ and derive the expression of the derivatives
needed to implement the corresponding Newton method. We then investigate the
stability of the process and explain why this inverse problem is severely
ill-posed by proving the compactness of the Hessian at the global minimizer.
Journal: None |
Submitter: Jing-Ling Chen
Authors: Jing-Ling Chen, Kang Xue, and Mo-Lin Ge
Title: Braiding transformation, entanglement swapping and Berry phase in
entanglement space
Abstract: We show that braiding transformation is a natural approach to describe
quantum entanglement, by using the unitary braiding operators to realize
entanglement swapping and generate the GHZ states as well as the linear cluster
states. A Hamiltonian is constructed from the unitary
$\check{R}_{i,i+1}(\theta,\phi)$-matrix, where $\phi=\omega t$ is
time-dependent while $\theta$ is time-independent. This in turn allows us to
investigate the Berry phase in the entanglement space.
Journal: Phys. Rev. A 76, 042324 (2007) |
Submitter: Joerg Junkersfeld
Authors: J. Junkersfeld (for the CB-ELSA collaboration)
Title: Photoproduction of pi0 omega off protons for E(gamma) < 3 GeV
Abstract: Differential and total cross-sections for photoproduction of gamma proton to
proton pi0 omega and gamma proton to Delta+ omega were determined from
measurements of the CB-ELSA experiment, performed at the electron accelerator
ELSA in Bonn. The measurements covered the photon energy range from the
production threshold up to 3GeV.
Journal: Eur.Phys.J.A31:365-372,2007 |
Submitter: Souichi Ishikawa
Authors: S. Ishikawa and M.R. Robilotta
Title: Two-pion exchange three-nucleon potential: O(q^4) chiral expansion
Abstract: We present the expansion of the two-pion exchange three-nucleon potential
(TPE-3NP) to chiral order q^4, which corresponds to a subset of all
possibilities at this order and is based on the \piN amplitude at O(q^3).
Results encompass both numerical corrections to strength coefficients of
previous O(q^3) terms and new structures in the profile functions. The former
are typically smaller than 10% whereas the latter arise from either loop
functions or non-local gradients acting on the wave function. The influence of
the new TPE-3NP over static and scattering three-body observables has been
assessed and found to be small, as expected from perturbative corrections.
Journal: Phys.Rev.C76:014006,2007 |
Submitter: Carla Figueira de Morisson Faria
Authors: H. Hetzheim, C. Figueira de Morisson Faria, and W. Becker
Title: Interference effects in above-threshold ionization from diatomic
molecules: determining the internuclear separation
Abstract: We calculate angle-resolved above-threshold ionization spectra for diatomic
molecules in linearly polarized laser fields, employing the strong-field
approximation. The interference structure resulting from the individual
contributions of the different scattering scenarios is discussed in detail,
with respect to the dependence on the internuclear distance and molecular
orientation. We show that, in general, the contributions from the processes in
which the electron is freed at one center and rescatters off the other obscure
the interference maxima and minima obtained from single-center processes.
However, around the boundary of the energy regions for which rescattering has a
classical counterpart, such processes play a negligible role and very clear
interference patterns are observed. In such energy regions, one is able to
infer the internuclear distance from the energy difference between adjacent
interference minima.
Journal: None |
Submitter: Ute Loew
Authors: Ute L\"ow
Title: Neel order in the two-dimensional S=1/2 Heisenberg Model
Abstract: The existence of Neel order in the S=1/2 Heisenberg model on the square
lattice at T=0 is shown using inequalities set up by Kennedy, Lieb and Shastry
in combination with high precision Quantum Monte Carlo data.
Journal: None |
Submitter: Fuquan Fang
Authors: Fuquan Fang, Yuguang Zhang, Zhenlei Zhang
Title: Maximum solutions of normalized Ricci flows on 4-manifolds
Abstract: We consider maximum solution $g(t)$, $t\in [0, +\infty)$, to the normalized
Ricci flow. Among other things, we prove that, if $(M, \omega) $ is a smooth
compact symplectic 4-manifold such that $b_2^+(M)>1$ and let
$g(t),t\in[0,\infty)$, be a solution to (1.3) on $M$ whose Ricci curvature
satisfies that $|\text{Ric}(g(t))|\leq 3$ and additionally $\chi(M)=3 \tau
(M)>0$, then there exists an $m\in \mathbb{N}$, and a sequence of points
$\{x_{j,k}\in M\}$, $j=1, ..., m$, satisfying that, by passing to a
subsequence, $$(M, g(t_{k}+t), x_{1,k},..., x_{m,k})
\stackrel{d_{GH}}\longrightarrow (\coprod_{j=1}^m N_j, g_{\infty},
x_{1,\infty}, ...,, x_{m,\infty}),$$ $t\in [0, \infty)$, in the $m$-pointed
Gromov-Hausdorff sense for any sequence $t_{k}\longrightarrow \infty$, where
$(N_{j}, g_{\infty})$, $j=1,..., m$, are complete complex hyperbolic orbifolds
of complex dimension 2 with at most finitely many isolated orbifold points.
Moreover, the convergence is $C^{\infty}$ in the non-singular part of
$\coprod_1^m N_{j}$ and
$\text{Vol}_{g_{0}}(M)=\sum_{j=1}^{m}\text{Vol}_{g_{\infty}}(N_{j})$, where
$\chi(M)$ (resp. $\tau(M)$) is the Euler characteristic (resp. signature) of
$M$.
Journal: None |
Submitter: Arnaud Ralko
Authors: A. Ralko, F. Mila, and D. Poilblanc
Title: Phase separation and flux quantization in the doped quantum dimer model
on the square and triangular lattices
Abstract: The doped two-dimensional quantum dimer model is investigated by numerical
techniques on the square and triangular lattices, with significantly different
results. On the square lattice, at small enough doping, there is always a phase
separation between an insulating valence-bond solid and a uniform superfluid
phase, whereas on the triangular lattice, doping leads directly to a uniform
superfluid in a large portion of the RVB phase. Under an applied Aharonov-Bohm
flux, the superfluid exhibits quantization in terms of half-flux quanta,
consistent with Q=2e elementary charge quanta in transport properties.
Journal: Phys. Rev. Lett. 99, 127202 (2007) |
Submitter: Christoph Richard
Authors: Christoph Richard
Title: Limit distributions and scaling functions
Abstract: We discuss the asymptotic behaviour of models of lattice polygons, mainly on
the square lattice. In particular, we focus on limiting area laws in the
uniform perimeter ensemble where, for fixed perimeter, each polygon of a given
area occurs with the same probability. We relate limit distributions to the
scaling behaviour of the associated perimeter and area generating functions,
thereby providing a geometric interpretation of scaling functions. To a major
extent, this article is a pedagogic review of known results.
Journal: Polygons, polyominoes and polycubes, 247-299, Lecture Notes in
Phys., 775, Springer, Dordrecht, 2009 |
Submitter: Alberto Anfossi
Authors: A. A. Aligia, A. Anfossi, L. Arrachea, C. Degli Esposti Boschi, A. O.
Dobry, C. Gazza, A. Montorsi, F. Ortolani, and M. E. Torio
Title: Incommmensurability and unconventional superconductor to insulator
transition in the Hubbard model with bond-charge interaction
Abstract: We determine the quantum phase diagram of the one-dimensional Hubbard model
with bond-charge interaction X in addition to the usual Coulomb repulsion U at
half-filling. For large enough X and positive U the model shows three phases.
For large U the system is in the spin-density wave phase already known in the
usual Hubbard model. As U decreases, there is first a spin transition to a
spontaneously dimerized bond-ordered wave phase and then a charge transition to
a novel phase in which the dominant correlations at large distances correspond
to an incommensurate singlet superconductor.
Journal: Phys. Rev. Lett. 99, 206401 (2007) |
Submitter: Paolo Lipari
Authors: Paolo Lipari, Maurizio Lusignoli, Davide Meloni
Title: Flavor Composition and Energy Spectrum of Astrophysical Neutrinos
Abstract: The measurement of the flavor composition of the neutrino fluxes from
astrophysical sources has been proposed as a method to study not only the
nature of their emission mechanisms, but also the neutrino fundamental
properties. It is however problematic to reconcile these two goals, since a
sufficiently accurate understanding of the neutrino fluxes at the source is
needed to extract information about the physics of neutrino propagation. In
this work we discuss critically the expectations for the flavor composition and
energy spectrum from different types of astrophysical sources, and comment on
the theoretical uncertainties connected to our limited knowledge of their
structure.
Journal: Phys.Rev.D75:123005,2007 |
Submitter: Kenta Kiuchi
Authors: Kenta Kiuchi, Hiroko Koyama, Kei-ichi Maeda
Title: Gravitational Wave Signals from Chaotic System: A Point Mass with A Disk
Abstract: We study gravitational waves from a particle moving around a system of a
point mass with a disk in Newtonian gravitational theory. A particle motion in
this system can be chaotic when the gravitational contribution from a surface
density of a disk is comparable with that from a point mass. In such an orbit,
we sometimes find that there appears a phase of the orbit in which particle
motion becomes to be nearly regular (the so-called ``stagnant motion'') for a
finite time interval between more strongly chaotic phases. To study how these
different chaotic behaviours affect on observation of gravitational waves, we
investigate a correlation of the particle motion and the waves. We find that
such a difference in chaotic motions reflects on the wave forms and energy
spectra. The character of the waves in the stagnant motion is quite different
from that either in a regular motion or in a more strongly chaotic motion. This
suggests that we may make a distinction between different chaotic behaviours of
the orbit via the gravitational waves.
Journal: Phys.Rev.D76:024018,2007 |
Submitter: Daniel Wilczak
Authors: D. Wilczak, P. Zgliczy\'nski
Title: $C^r$-Lohner algorithm
Abstract: We present a Lohner type algorithm for the computation of rigorous bounds for
solutions of ordinary differential equations and its derivatives with respect
to initial conditions up to arbitrary order. As an application we prove the
existence of multiple invariant tori around some elliptic periodic orbits for
the pendulum equation with periodic forcing and for Michelson system.
Journal: None |
Submitter: Daniel Summons
Authors: D.P. Summons, P. Arevalo, I.M. McHardy, P.Uttley and A.Bhaskar
(University of Southampton)
Title: Timing evidence in determining the accretion state of the Seyfert galaxy
NGC 3783
Abstract: Previous observations with the Rossi X-ray Timing Explorer (RXTE) have
suggested that the power spectral density (PSD) of NGC 3783 flattens to a slope
near zero at low frequencies, in a similar manner to that of Galactic black
hole X-ray binary systems (GBHs) in the `hard' state. The low radio flux
emitted by this object, however, is inconsistent with a hard state
interpretation. The accretion rate of NGC 3783 (~7% of the Eddington rate) is
similar to that of other AGN with `soft' state PSDs and higher than that at
which the GBH Cyg X-1, with which AGN are often compared, changes between
`hard' and `soft' states (~2% of the Eddington rate). If NGC 3783 really does
have a `hard' state PSD, it would be quite unusual and would indicate that AGN
and GBHs are not quite as similar as we currently believe. Here we present an
improved X-ray PSD of NGC 3783, spanning from ~10^{-8} to ~10^{-3} Hz, based on
considerably extended (5.5 years) RXTE observations combined with two orbits of
continuous observation by XMM-Newton. We show that this PSD is, in fact, well
fitted by a `soft' state model which has only one break, at high frequencies.
Although a `hard' state model can also fit the data, the improvement in fit by
adding a second break at low frequency is not significant. Thus NGC 3783 is not
unusual. These results leave Arakelian 564 as the only AGN which shows a second
break at low frequencies, although in that case the very high accretion rate
implies a `very high', rather than `hard' state PSD. The break frequency found
in NGC 3783 is consistent with the expectation based on comparisons with other
AGN and GBHs, given its black hole mass and accretion rate.
Journal: Mon.Not.Roy.Astron.Soc.378:649-656,2007 |
Submitter: Axel Maas
Authors: Axel Maas
Title: Two- and three-point Green's functions in two-dimensional Landau-gauge
Yang-Mills theory
Abstract: The ghost and gluon propagator and the ghost-gluon and three-gluon vertex of
two-dimensional SU(2) Yang-Mills theory in (minimal) Landau gauge are studied
using lattice gauge theory. It is found that the results are qualitatively
similar to the ones in three and four dimensions. The propagators and the
Faddeev-Popov operator behave as expected from the Gribov-Zwanziger scenario.
In addition, finite volume effects affecting these Green's functions are
investigated systematically. The critical infrared exponents of the
propagators, as proposed in calculations using stochastic quantization and
Dyson-Schwinger equations, are confirmed quantitatively. For this purpose
lattices of volume up to (42.7 fm)^2 have been used.
Journal: Phys.Rev.D75:116004,2007 |
Submitter: L\"u Jing Tao
Authors: J. T. L\"u and Jian-Sheng Wang
Title: Coupled electron and phonon transport in one-dimensional atomic
junctions
Abstract: Employing the nonequilibrium Green's function method, we develop a fully
quantum mechanical model to study the coupled electron-phonon transport in
one-dimensional atomic junctions in the presence of a weak electron-phonon
interaction. This model enables us to study the electronic and phononic
transport on an equal footing. We derive the electrical and energy currents of
the coupled electron-phonon system and the energy exchange between them. As an
application, we study the heat dissipation in current carrying atomic junctions
within the self-consistent Born approximation, which guarantees energy current
conservation. We find that the inclusion of phonon transport is important in
determining the heat dissipation and temperature change of the atomic
junctions.
Journal: Phys. Rev. B 76, 165418 (2007) |
Submitter: Ning Kang
Authors: Ning Kang, Eisuke Abe, Yoshiaki Hashimoto, Yasuhiro Iye, and Shingo
Katsumoto
Title: Observation of Spin-Orbit Berry's Phase in Magnetoresistance of a
Two-Dimensional Hole Anti-dot System
Abstract: We report observation of spin-orbit Berry's phase in the Aharonov-Bohm (AB)
type oscillation of weak field magnetoresistance in an anti-dot lattice (ADL)
of a two-dimensional hole system. An AB-type oscillation is superposed on the
commensurability peak, and the main peak in the Fourier transform is clearly
split up due to variation in Berry's phase originating from the spin-orbit
interaction. A simulation considering Berry's phase and the phase arising from
the spin-orbit shift in the momentum space shows qualitative agreement with the
experiment.
Journal: J. Phys. Soc. Jpn. 76, 083704 (2007) |
Submitter: J\"org G\"otte
Authors: J. B. Goette, S. M. Barnett and M. Padgett
Title: On the dragging of light by a rotating medium
Abstract: When light is passing through a rotating medium the optical polarisation is
rotated. Recently it has been reasoned that this rotation applies also to the
transmitted image (Padgett et al. 2006). We examine these two phenomena by
extending an analysis of Player (1976) to general electromagnetic fields. We
find that in this more general case the wave equation inside the rotating
medium has to be amended by a term which is connected to the orbital angular
momentum of the light. We show that optical spin and orbital angular momentum
account respectively for the rotation of the polarisation and the rotation of
the transmitted image.
Journal: None |
Submitter: Pouria Pedram
Authors: G. R. Jafari, P. Pedram, L. Hedayatifar
Title: Long-range correlation and multifractality in Bach's Inventions pitches
Abstract: We show that it can be considered some of Bach pitches series as a stochastic
process with scaling behavior. Using multifractal deterend fluctuation analysis
(MF-DFA) method, frequency series of Bach pitches have been analyzed. In this
view we find same second moment exponents (after double profiling) in ranges
(1.7-1.8) in his works. Comparing MF-DFA results of original series to those
for shuffled and surrogate series we can distinguish multifractality due to
long-range correlations and a broad probability density function. Finally we
determine the scaling exponents and singularity spectrum. We conclude fat tail
has more effect in its multifractality nature than long-range correlations.
Journal: J. Stat. Mech. P04012 (2007) |
Submitter: Tobias Lindstrom
Authors: T. Lindstrom, C.H. Webster, A.Ya.Tzalenchuk, J.E. Healey, M. S.
Colclough and C.M. Muirhead
Title: Circuit QED with a Flux Qubit Strongly Coupled to a Coplanar
Transmission Line Resonator
Abstract: We propose a scheme for circuit quantum electrodynamics with a
superconducting flux-qubit coupled to a high-Q coplanar resonator. Assuming
realistic circuit parameters we predict that it is possible to reach the strong
coupling regime. Routes to metrological applications, such as single photon
generation and quantum non-demolition measurements are discussed.
Journal: Supercond.Sci.Technol.20:814-821,2007 |
Submitter: D. B. Gutman
Authors: D. B. Gutman, Yuval Gefen, and A. D. Mirlin
Title: Zero bias anomaly out of equilibrium
Abstract: The non-equilibrium zero bias anomaly (ZBA) in the tunneling density of
states of a diffusive metallic film is studied. An effective action describing
virtual fluctuations out-of-equilibrium is derived. The singular behavior of
the equilibrium ZBA is smoothed out by real processes of inelastic scattering.
Journal: Phys. Rev. Lett. 100, 086801 (2008) |
Submitter: David Kastor
Authors: David Kastor, Sourya Ray and Jennie Traschen
Title: The First Law for Boosted Kaluza-Klein Black Holes
Abstract: We study the thermodynamics of Kaluza-Klein black holes with momentum along
the compact dimension, but vanishing angular momentum. These black holes are
stationary, but non-rotating. We derive the first law for these spacetimes and
find that the parameter conjugate to variations in the length of the compact
direction is an effective tension, which generally differs from the ADM
tension. For the boosted black string, this effective tension is always
positive, while the ADM tension is negative for large boost parameter. We also
derive two Smarr formulas, one that follows from time translation invariance,
and a second one that holds only in the case of exact translation symmetry in
the compact dimension. Finally, we show that the `tension first law' derived by
Traschen and Fox in the static case has the form of a thermodynamic Gibbs-Duhem
relation and give its extension in the stationary, non-rotating case.
Journal: JHEP 0706:026,2007 |
Submitter: Hamed Haddadi MSc MIEE
Authors: Hamed Haddadi, Raul Landa, Miguel Rio, Saleem Bhatti
Title: Revisiting the Issues On Netflow Sample and Export Performance
Abstract: The high volume of packets and packet rates of traffic on some router links
makes it exceedingly difficult for routers to examine every packet in order to
keep detailed statistics about the traffic which is traversing the router.
Sampling is commonly applied on routers in order to limit the load incurred by
the collection of information that the router has to undertake when evaluating
flow information for monitoring purposes. The sampling process in nearly all
cases is a deterministic process of choosing 1 in every N packets on a
per-interface basis, and then forming the flow statistics based on the
collected sampled statistics. Even though this sampling may not be significant
for some statistics, such as packet rate, others can be severely distorted.
However, it is important to consider the sampling techniques and their relative
accuracy when applied to different traffic patterns. The main disadvantage of
sampling is the loss of accuracy in the collected trace when compared to the
original traffic stream. To date there has not been a detailed analysis of the
impact of sampling at a router in various traffic profiles and flow criteria.
In this paper, we assess the performance of the sampling process as used in
NetFlow in detail, and we discuss some techniques for the compensation of loss
of monitoring detail.
Journal: None |
Submitter: Thomas Lesinski
Authors: T. Lesinski (IPNL), M. Bender (DAPNIA, Cenbg), K. Bennaceur (IPNL,
Dapnia), T. Duguet (NSCL, Msu), J. Meyer (IPNL)
Title: The tensor part of the Skyrme energy density functional. I. Spherical
nuclei
Abstract: We perform a systematic study of the impact of the J^2 tensor term in the
Skyrme energy functional on properties of spherical nuclei. In the Skyrme
energy functional, the tensor terms originate both from zero-range central and
tensor forces. We build a set of 36 parameterizations, which covers a wide
range of the parameter space of the isoscalar and isovector tensor term
coupling constants, with a fit protocol very similar to that of the successful
SLy parameterizations. We analyze the impact of the tensor terms on a large
variety of observables in spherical mean-field calculations, such as the
spin-orbit splittings and single-particle spectra of doubly-magic nuclei, the
evolution of spin-orbit splittings along chains of semi-magic nuclei, mass
residuals of spherical nuclei, and known anomalies of charge radii. Our main
conclusion is that the currently used central and spin-orbit parts of the
Skyrme energy density functional are not flexible enough to allow for the
presence of large tensor terms.
Journal: Physical Review C 76, (2007) 014312 |
Submitter: T. Damour
Authors: Thibault Damour
Title: Cosmological Singularities and a Conjectured Gravity/Coset
Correspondence
Abstract: We review the recently discovered connection between the
Belinsky-Khalatnikov-Lifshitz-like ``chaotic'' structure of generic
cosmological singularities in eleven-dimensional supergravity and the ``last''
hyperbolic Kac-Moody algebra E(10). This intriguing connection suggests the
existence of a hidden ``correspondence'' between supergravity (or even
M-theory) and null geodesic motion on the infinite-dimensional coset space
K(E(10)). If true, this gravity/coset correspondence would offer a new view of
the (quantum) fate of space (and matter) at cosmological singularities.
Journal: Lect.NotesPhys.737:941-948,2008 |
Submitter: Bludov Yuliy
Authors: Yu. V. Bludov, V. V. Konotop
Title: Acceleration and localization of matter in a ring trap
Abstract: A toroidal trap combined with external time-dependent electric field can be
used for implementing different dynamical regimes of matter waves. In
particular, we show that dynamical and stochastic acceleration, localization
and implementation of the Kapitza pendulum can be originated by means of proper
choice of the external force.
Journal: PHYSICAL REVIEW A 75, 053614 (2007) |
Submitter: Xiaoling Zhang
Authors: Xiao-Ling Zhang, Shuang Nan Zhang, Gloria Sala, Jochen Greiner, Yuxin
Feng, Yangsen Yao
Title: GRO J1655-40: from ASCA and XMM-Newton Observations
Abstract: We have analysed four ASCA observations (1994--1995, 1996--1997) and three
XMM-Newton observations (2005) of this source, in all of which the source is in
high/soft state. We modeled the continuum spectra with relativistic disk model
kerrbb, estimated the spin of the central black hole, and constrained the
spectral hardening factor f_col and the distance. If kerrbb model applies, for
normally used value of f_col, the distance cannot be very small, and f_col
changes with observations.
Journal: None |
Submitter: Pozzi Francesca
Authors: F. Pozzi, C. Vignali, A. Comastri, L. Pozzetti, M. Mignoli, C.
Gruppioni, G. Zamorani, C. Lari, F. Civano, M. Brusa, F. Fiore, R. Maiolino
and F. La Franca
Title: The HELLAS2XMM survey. X. The bolometric output of luminous obscured
quasars: The Spitzer perspective
Abstract: Aims: We aim at estimating the spectral energy distributions (SEDs) and the
physical parameters related to the black holes harbored in eight high
X-ray-to-optical (F_X/F_R>10) obscured quasars at z>0.9 selected in the 2--10
keV band from the HELLAS2XMM survey.
Methods: We use IRAC and MIPS 24 micron observations, along with optical and
Ks-band photometry, to obtain the SEDs of the sources. The observed SEDs are
modeled using a combination of an elliptical template and torus emission (using
the phenomenological templates of Silva et al. 2004) for six sources associated
with passive galaxies; for two point-like sources, the empirical SEDs of red
quasars are adopted. The bolometric luminosities and the M_BH-L_K relation are
used to provide an estimate of the masses and Eddington ratios of the black
holes residing in these AGN.
Results: All of our sources are detected in the IRAC and MIPS (at 24 micron)
bands. The SED modeling described above is in good agreement with the observed
near- and mid-infrared data. The derived bolometric luminosities are in the
range ~10^45-10^47 erg s^-1, and the median 2--10 keV bolometric correction is
~25, consistent with the widely adopted value derived by Elvis et al. (1994).
For the objects with elliptical-like profiles in the K_s band, we derive high
stellar masses (0.8-6.2)X10^11 Mo, black hole masses in the range
(0.2-2.5)X10^9 Mo, and Eddington ratios L/L_Edd<0.1, suggesting a low-accretion
phase.
Journal: None |
Submitter: Vladimir Shelkovich M
Authors: V. M. Shelkovich, M. Skopina
Title: $p$-Adic Haar multiresolution analysis
Abstract: In this paper, the notion of {\em $p$-adic multiresolution analysis (MRA)} is
introduced. We use a ``natural'' refinement equation whose solution (a
refinable function) is the characteristic function of the unit disc. This
equation reflects the fact that the characteristic function of the unit disc is
the sum of $p$ characteristic functions of disjoint discs of radius $p^{-1}$.
The case $p=2$ is studied in detail. Our MRA is a 2-adic analog of the real
Haar MRA. But in contrast to the real setting, the refinable function
generating our Haar MRA is periodic with period 1, which never holds for real
refinable functions. This fact implies that there exist infinity many different
2-adic orthonormal wavelet bases in ${\cL}^2(\bQ_2)$ generated by the same Haar
MRA. All of these bases are constructed. Since $p$-adic pseudo-differential
operators are closely related to wavelet-type bases, our bases can be
intensively used for applications.
Journal: None |
Submitter: Marcus Berg
Authors: Marcus Berg, Michael Haack, Enrico Pajer
Title: Jumping Through Loops: On Soft Terms from Large Volume Compactifications
Abstract: We subject the phenomenologically successful large volume scenario of
hep-th/0502058 to a first consistency check in string theory. In particular, we
consider whether the expansion of the string effective action is consistent in
the presence of D-branes and O-planes. Due to the no-scale structure at
tree-level, the scenario is surprisingly robust. We compute the modification of
soft supersymmetry breaking terms, and find only subleading corrections. We
also comment that for large-volume limits of toroidal orientifolds and fibered
Calabi-Yau manifolds the corrections can be more important, and we discuss
further checks that need to be performed.
Journal: JHEP0709:031,2007 |
Submitter: Patrick Ilg
Authors: Patrick Ilg and Jean-Louis Barrat
Title: Driven activation versus thermal activation
Abstract: Activated dynamics in a glassy system undergoing steady shear deformation is
studied by numerical simulations. Our results show that the external driving
force has a strong influence on the barrier crossing rate, even though the
reaction coordinate is only weakly coupled to the nonequilibrium system. This
"driven activation" can be quantified by introducing in the Arrhenius
expression an effective temperature, which is close to the one determined from
the fluctuation-dissipation relation. This conclusion is supported by
analytical results for a simplified model system.
Journal: EPL 79 (2007) 26001 |
Submitter: Lucas Gallindo
Authors: Lucas Gallindo Martins Soares
Title: Computation of Power Loss in Likelihood Ratio Tests for Probability
Densities Extended by Lehmann Alternatives
Abstract: We compute the loss of power in likelihood ratio tests when we test the
original parameter of a probability density extended by the first Lehmann
alternative.
Journal: None |
Submitter: Carlo Nipoti
Authors: Carlo Nipoti (1), Pasquale Londrillo (2), HongSheng Zhao (3), Luca
Ciotti (1) ((1) Bologna Univ., (2) INAF - Bologna Astr. Obs. (3) SUPA, St.
Andrews Univ.)
Title: Vertical dynamics of disk galaxies in MOND
Abstract: We investigate the possibility of discriminating between Modified Newtonian
Dynamics (MOND) and Newtonian gravity with dark matter, by studying the
vertical dynamics of disk galaxies. We consider models with the same circular
velocity in the equatorial plane (purely baryonic disks in MOND and the same
disks in Newtonian gravity embedded in spherical dark matter haloes), and we
construct their intrinsic and projected kinematical fields by solving the Jeans
equations under the assumption of a two-integral distribution function. We
found that the vertical velocity dispersion of deep-MOND disks can be much
larger than in the equivalent spherical Newtonian models. However, in the more
realistic case of high-surface density disks this effect is significantly
reduced, casting doubts on the possibility of discriminating between MOND and
Newtonian gravity with dark matter by using current observations.
Journal: Mon.Not.Roy.Astron.Soc.379:597-604,2007 |
Submitter: Christophe Texier
Authors: Christophe Texier and Gilles Montambaux
Title: Al'tshuler-Aronov correction to the conductivity of a large metallic
square network
Abstract: We consider the correction $\Delta\sigma_\mathrm{ee}$ due to
electron-electron interaction to the conductivity of a weakly disordered metal
(Al'tshuler-Aronov correction). The correction is related to the spectral
determinant of the Laplace operator. The case of a large square metallic
network is considered. The variation of $\Delta\sigma_\mathrm{ee}(L_T)$ as a
function of the thermal length $L_T$ is found very similar to the variation of
the weak localization $\Delta\sigma_\mathrm{WL}(L_\phi)$ as a function of the
phase coherence length. Our result for $\Delta\sigma_\mathrm{ee}$ interpolates
between the known 1d and 2d results, but the interaction parameter entering the
expression of $\Delta\sigma_\mathrm{ee}$ keeps a 1d behaviour. Quite
surprisingly, the result is very close to the 2d logarithmic behaviour already
for $L_T\sim{a}/2$, where $a$ is the lattice parameter.
Journal: Phys. Rev. B 76, 094202 (2007) |
Submitter: Christophe Texier
Authors: Christophe Texier and Gilles Montambaux
Title: Magnetoconductance oscillations in metallic rings and decoherence due to
electron-electron interaction
Abstract: We study weak localization in chains of metallic rings. We show than
nonlocality of quantum transport can drastically affect the behaviour of the
harmonics of magnetoconductance oscillations. Two different geometries are
considered: the case of rings separated by long wires compared to the phase
coherence length and the case of contacted rings. In a second part we discuss
the role of decoherence due to electron-electron interaction in these two
geometries.
Journal: None |
Submitter: Adam Rycerz
Authors: Adam Rycerz
Title: Diatomic molecule as a quantum entanglement switch
Abstract: We investigate a pair entanglement of electrons in diatomic molecule, modeled
as a correlated double quantum dot attached to the leads. The low-temperature
properties are derived from the ground state obtained by utilizing the
Rejec-Ramsak variational technique within the framework of EDABI method, which
combines exact diagonalization with ab initio calculations. The results show,
that single-particle basis renormalization modifies the entanglement-switch
effectiveness significantly. We also found the entanglement signature of a
competition between an extended Kondo and singlet phases.
Journal: Physica B 403, 1534 (2008) |
Submitter: Gergely Palla
Authors: Gergely Palla, Albert-Laszlo Barabasi and Tamas Vicsek
Title: Quantifying social group evolution
Abstract: The rich set of interactions between individuals in the society results in
complex community structure, capturing highly connected circles of friends,
families, or professional cliques in a social network. Thanks to frequent
changes in the activity and communication patterns of individuals, the
associated social and communication network is subject to constant evolution.
Our knowledge of the mechanisms governing the underlying community dynamics is
limited, but is essential for a deeper understanding of the development and
self-optimisation of the society as a whole. We have developed a new algorithm
based on clique percolation, that allows, for the first time, to investigate
the time dependence of overlapping communities on a large scale and as such, to
uncover basic relationships characterising community evolution. Our focus is on
networks capturing the collaboration between scientists and the calls between
mobile phone users. We find that large groups persist longer if they are
capable of dynamically altering their membership, suggesting that an ability to
change the composition results in better adaptability. The behaviour of small
groups displays the opposite tendency, the condition for stability being that
their composition remains unchanged. We also show that the knowledge of the
time commitment of the members to a given community can be used for estimating
the community's lifetime. These findings offer a new view on the fundamental
differences between the dynamics of small groups and large institutions.
Journal: Nature 446, 664 (2007) |
Submitter: Maria Siopacha
Authors: Maria Siopacha and Josef Teichmann
Title: Weak and Strong Taylor methods for numerical solutions of stochastic
differential equations
Abstract: We apply results of Malliavin-Thalmaier-Watanabe for strong and weak Taylor
expansions of solutions of perturbed stochastic differential equations (SDEs).
In particular, we work out weight expressions for the Taylor coefficients of
the expansion. The results are applied to LIBOR market models in order to deal
with the typical stochastic drift and with stochastic volatility. In contrast
to other accurate methods like numerical schemes for the full SDE, we obtain
easily tractable expressions for accurate pricing. In particular, we present an
easily tractable alternative to ``freezing the drift'' in LIBOR market models,
which has an accuracy similar to the full numerical scheme. Numerical examples
underline the results.
Journal: None |
Submitter: Roche Patrice
Authors: Preden Roulleau, F. Portier, D. C. Glattli, P. Roche, A. Cavanna, G.
Gaini, U. Gennser, and D. Mailly
Title: Finite bias visibility of the electronic Mach-Zehnder interferometer
Abstract: We present an original statistical method to measure the visibility of
interferences in an electronic Mach-Zehnder interferometer in the presence of
low frequency fluctuations. The visibility presents a single side lobe
structure shown to result from a gaussian phase averaging whose variance is
quadratic with the bias. To reinforce our approach and validate our statistical
method, the same experiment is also realized with a stable sample. It exhibits
the same visibility behavior as the fluctuating one, indicating the intrinsic
character of finite bias phase averaging. In both samples, the dilution of the
impinging current reduces the variance of the gaussian distribution.
Journal: Phys. Rev. B 76, 161309 (2007) |
Submitter: Branko Malesevic
Authors: Branko J. Malesevic
Title: A note on higher-order differential operations
Abstract: In this paper we consider successive iterations of the first-order
differential operations in space ${\bf R}^3.$
Journal: Univ. Beograd. Publ. Elektrotehn. Fak., Ser. Mat. 7 (1996),
105--109 |
Submitter: Joseph Harris
Authors: Christopher C. Davis, Joseph Harris, Robert W. Gammon, Igor I.
Smolyaninov and Kyuman Cho
Title: Experimental Challenges Involved in Searches for Axion-Like Particles
and Nonlinear Quantum Electrodynamic Effects by Sensitive Optical Techniques
Abstract: We discuss the experimental techniques used to date for measuring the changes
in polarization state of a laser produced by a strong transverse magnetic field
acting in a vacuum. We point out the likely artifacts that can arise in such
experiments, with particular reference to the recent PVLAS observations and the
previous findings of the BFRT collaboration. Our observations are based on
studies with a photon-noise limited coherent homodyne interferometer with a
polarization sensitivity of 2x10^-8 rad Hz^(1/2) mW^(-1/2).
Journal: None |
Submitter: T. Damour
Authors: Thibault Damour
Title: Binary Systems as Test-beds of Gravity Theories
Abstract: We review the general relativistic theory of the motion, and of the timing,
of binary systems containing compact objects (neutron stars or black holes).
Then we indicate the various ways one can use binary pulsar data to test the
strong-field and/or radiative aspects of General Relativity, and of general
classes of alternative theories of relativistic gravity.
Journal: None |
Submitter: Branko Malesevic
Authors: Branko J. Malesevic
Title: Some combinatorial aspects of differential operation compositions on
space $R^n$
Abstract: In this paper we present a recurrent relation for counting meaningful
compositions of the higher-order differential operations on the space $R^{n}$
(n=3,4,...) and extract the non-trivial compositions of order higher than two.
Journal: Univ. Beograd. Publ. Elektrotehn. Fak. Ser. Mat. 9 (1998), 29--33 |
Submitter: Filippo Bracci
Authors: Filippo Bracci, Alberto Saracco
Title: Hyperbolicity in unbounded convex domains
Abstract: We provide several equivalent characterizations of Kobayashi hyperbolicity in
unbounded convex domains in terms of peak and anti-peak functions at infinity,
affine lines, Bergman metric and iteration theory.
Journal: None |
Submitter: Davoud Kamani
Authors: Davoud Kamani
Title: Actions for the Bosonic String with the Curved Worldsheet
Abstract: At first we introduce an action for the string, which leads to a worldsheet
that always is curved. For this action we study the Poincar\'e symmetry and the
associated conserved currents. Then, a generalization of the above action,
which contains an arbitrary function of the two-dimensional scalar curvature,
will be introduced. An extra scalar field enables us to modify these actions to
Weyl invariant models.
Journal: Braz.J.Phys.38:268-271,2008 |
Submitter: Dr. Anirudh Pradhan
Authors: Raj Bali, Umesh Kumar Pareek and Anirudh Pradhan
Title: Bianchi Type I Massive String Magnetized Barotropic Perfect Fluid
Cosmological Model in General Relativity
Abstract: Bianchi type I massive string cosmological model with magnetic field of
barotropic perfect fluid distribution through the techniques used by Latelier
and Stachel, is investigated. To get the deterministic model of the universe,
it is assumed that the universe is filled with barotropic perfect fluid
distribution. The magnetic field is due to electric current produced along
x-axis with infinite electrical conductivity. The behaviour of the model in
presence and absence of magnetic field together with other physical aspects is
further discussed.
Journal: Chin.Phys.Lett.24:2455-2458,2007 |
Submitter: T. Damour
Authors: Thibault Damour
Title: General Relativity Today
Abstract: After recalling the conceptual foundations and the basic structure of general
relativity, we review some of its main modern developments (apart from
cosmology) : (i) the post-Newtonian limit and weak-field tests in the solar
system, (ii) strong gravitational fields and black holes, (iii) strong-field
and radiative tests in binary pulsar observations, (iv) gravitational waves,
(v) general relativity and quantum theory.
Journal: None |
Submitter: Branko Malesevic
Authors: Branko Malesevic, Ivana Jovovic
Title: A procedure for finding the k-th power of a matrix
Abstract: We give a new procedure in Maple for finding the k-th power of a martix. The
algorithm is based on the article [1].
Journal: None |
Submitter: Ruth Durrer
Authors: Ruth Durrer and Marcus Ruser
Title: The dynamical Casimir effect in braneworlds
Abstract: In braneworld cosmology the expanding Universe is realized as a brane moving
through a warped higher-dimensional spacetime. Like a moving mirror causes the
creation of photons out of vacuum fluctuations, a moving brane leads to
graviton production. We show that, very generically, Kaluza-Klein (KK)
particles scale like stiff matter with the expansion of the Universe and can
therefore not represent the dark matter in a warped braneworld. We present
results for the production of massless and KK gravitons for bouncing branes in
five-dimensional anti de Sitter space. We find that for a realistic bounce the
back reaction from the generated gravitons will be most likely relevant. This
letter summarizes the main results and conclusions from numerical simulations
which are presented in detail in a long paper [M.Ruser and R. Durrer, Phys.
Rev. D 76, 104014 (2007), arXiv:0704.0790]
Journal: Phys.Rev.Lett.99:071601,2007 |
Submitter: Ou Yong-Cheng
Authors: Yong-Cheng Ou and Heng Fan
Title: Bounds on Negativity of Superpositions
Abstract: The entanglement quantified by negativity of pure bipartite superposed states
is studied. We show that if the entanglement is quantified by the concurrence
two pure states of high fidelity to one another still have nearly the same
entanglement. Furthermore this conclusion can be guaranteed by our obtained
inequality, and the concurrence is shown to be a continuous function even in
infinite dimensions. The bounds on the negativity of superposed states in terms
of those of the states being superposed are obtained. These bounds can find
useful applications in estimating the amount of the entanglement of a given
pure state.
Journal: Physical Review A 76,022320(2007) |
Submitter: Matthaeus Halder
Authors: Matthaeus Halder, Alexios Beveratos, Nicolas Gisin, Valerio Scarani,
Christoph Simon and Hugo Zbinden
Title: Entangling Independent Photons by Time Measurement
Abstract: A quantum system composed of two or more subsystems can be in an entangled
state, i.e. a state in which the properties of the global system are well
defined but the properties of each subsystem are not. Entanglement is at the
heart of quantum physics, both for its conceptual foundations and for
applications in information processing and quantum communication. Remarkably,
entanglement can be "swapped": if one prepares two independent entangled pairs
A1-A2 and B1-B2, a joint measurement on A1 and B1 (called a "Bell-State
Measurement", BSM) has the effect of projecting A2 and B2 onto an entangled
state, although these two particles have never interacted or shared any common
past[1,2]. Experiments using twin photons produced by spontaneous parametric
down-conversion (SPDC) have already demonstrated entanglement swapping[3-6],
but here we present its first realization using continuous wave (CW) sources,
as originally proposed[2]. The challenge was to achieve sufficiently sharp
synchronization of the photons in the BSM. Using narrow-band filters, the
coherence time of the photons that undergo the BSM is significantly increased,
exceeding the temporal resolution of the detectors. Hence pulsed sources can be
replaced by CW sources, which do not require any synchronization[6,7], allowing
for the first time the use of completely autonomous sources. Our experiment
exploits recent progress in the time precision of photon detectors, in the
efficiency of photon pair production by SPDC with waveguides in nonlinear
crystals[8], and in the stability of narrow-band filters. This approach is
independent of the form of entanglement; we employed time-bin entangled
photons[9] at telecom wavelengths. Our setup is robust against thermal or
mechanical fluctuations in optical fibres thanks to cm-long coherence lengths.
Journal: Nature Physics 3, 692 - 695 (2007) |
Submitter: Peter Constantin
Authors: A. Cheskidov, P. Constantin, S. Friedlander, R. Shvydkoy
Title: Energy conservation and Onsager's conjecture for the Euler equations
Abstract: Onsager conjectured that weak solutions of the Euler equations for
incompressible fluids in 3D conserve energy only if they have a certain minimal
smoothness, (of order of 1/3 fractional derivatives) and that they dissipate
energy if they are rougher. In this paper we prove that energy is conserved for
velocities in the function space $B^{1/3}_{3,c(\NN)}$. We show that this space
is sharp in a natural sense. We phrase the energy spectrum in terms of the
Littlewood-Paley decomposition and show that the energy flux is controlled by
local interactions. This locality is shown to hold also for the helicity flux;
moreover, every weak solution of the Euler equations that belongs to
$B^{2/3}_{3,c(\NN)}$ conserves helicity. In contrast, in two dimensions, the
strong locality of the enstrophy holds only in the ultraviolet range.
Journal: None |
Submitter: Peter Wagner
Authors: A. Abulencia et al. (CDF Collaboration)
Title: Search for Heavy, Long-Lived Particles that Decay to Photons at CDF II
Abstract: We present the first search for heavy, long-lived particles that decay to
photons at a hadron collider. We use a sample of photon+jet+missing transverse
energy events in p-pbar collisions at \sqrt{s}=1.96 TeV taken with the CDF II
detector. Candidate events are selected based on the arrival time of the photon
at the detector. Using an integrated luminosity of 570 pb-1 of collision data,
we observe 2 events, consistent with the background estimate of 1.3+-0.7
events. While our search strategy does not rely on model-specific dynamics, we
set cross section limits in a supersymmetric model with
\tilde{\chi}_1^0->\gamma\gravitino and place the world-best 95% C.L. lower
limit on the \tilde{\chi}_1^0 mass of 101 GeV/c^2 at \tau_{\tilde{\chi}_1^0} =
5 ns.
Journal: Phys.Rev.Lett.99:121801,2007 |
Submitter: Jose Vilar
Authors: Jose M. G. Vilar and J. Miguel Rubi
Title: Failure of the work-Hamiltonian connection for free energy calculations
Abstract: Extensions of statistical mechanics are routinely being used to infer free
energies from the work performed over single-molecule nonequilibrium
trajectories. A key element of this approach is the ubiquitous expression
dW/dt=\partial H(x,t)/ \partial t which connects the microscopic work W
performed by a time-dependent force on the coordinate x with the corresponding
Hamiltonian H(x,t) at time t. Here we show that this connection, as pivotal as
it is, cannot be used to estimate free energy changes. We discuss the
implications of this result for single-molecule experiments and atomistic
molecular simulations and point out possible avenues to overcome these
limitations.
Journal: None |
Submitter: Yongmei Wang Prof.
Authors: Jesse D. Ziebarth, Yongmei Wang, Alexey Polotsky, Mengbo Luo
Title: Dependence of the Critical Adsorption Point on Surface and Sequence
Disorders for Self-Avoiding Walks Interacting with a Planar Surface
Abstract: The critical adsorption point (CAP) of self-avoiding walks (SAW) interacting
with a planar surface with surface disorder or sequence disorder has been
studied. We present theoretical equations, based on ones previously developed
by Soteros and Whittington (J. Phys. A.: Math. Gen. 2004, 37, R279-R325), that
describe the dependence of CAP on the disorders along with Monte Carlo
simulation data that are in agreement with the equations. We also show
simulation results that deviate from the equations when the approximations used
in the theory break down. Such knowledge is the first step toward understanding
the correlation of surface disorder and sequence disorder during polymer
adsorption.
Journal: None |
Submitter: Daniel Braun
Authors: John Martin and Daniel Braun
Title: Coherent control of atomic tunneling
Abstract: We study the tunneling of a two-level atom in a double well potential while
the atom is coupled to a single electromagnetic field mode of a cavity. The
coupling between internal and external degrees of freedom, due to the
mechanical effect on the atom from photon emission into the cavity mode, can
dramatically change the tunneling behavior. We predict that in general the
tunneling process becomes quasiperiodic. In a certain regime of parameters a
collapse and revival of the tunneling occurs. Accessing the internal degrees of
freedom of the atom with a laser allows to coherently manipulate the atom
position, and in particular to prepare the atom in one of the two wells. The
effects described should be observable with atoms in an optical double well
trap.
Journal: J. Phys. B: At. Mol. Opt. Phys. 41, 115502 (2008) |
Submitter: Temo Vekua Dr.
Authors: T. Vekua, A. Honecker, H.-J. Mikeska, and F. Heidrich-Meisner
Title: Correlation functions and excitation spectrum of the frustrated
ferromagnetic spin-1/2 chain in an external magnetic field
Abstract: Magnetic field effects on the one-dimensional frustrated ferromagnetic chain
are studied by means of effective field theory approaches in combination with
numerical calculations utilizing Lanczos diagonalization and the density matrix
renormalization group method. The nature of the ground state is shown to change
from a spin-density-wave region to a nematic-like one upon approaching the
saturation magnetization. The excitation spectrum is analyzed and the behavior
of the single spin-flip excitation gap is studied in detail, including the
emergent finite-size corrections.
Journal: Phys. Rev. B 76, 174420 (2007) |
Submitter: Kevin Parendo
Authors: K. H. Sarwa B. Tan, Kevin A. Parendo, and A. M. Goldman
Title: Evidence of Spatially Inhomogeous Pairing on the Insulating Side of a
Disorder-Tuned Superconductor-Insulator Transition
Abstract: Measurements of transport properties of amorphous insulating indium oxide
thin films have been interpreted as evidence of the presence of superconducting
islands on the insulating side of a disorder-tuned superconductor-insulator
transition. Although the films are not granular, the behavior is similar to
that observed in granular films. The results support theoretical models in
which the destruction of superconductivity by disorder produces spatially
inhomogenous pairing with a spectral gap.
Journal: None |
Submitter: Michael Clover
Authors: Michael Clover
Title: Local de Broglie-Bohm Trajectories from Entangled Wavefunctions
Abstract: We present a local interpretation of what is usually considered to be a
nonlocal de Broglie-Bohm trajectory prescription for an entangled singlet state
of massive particles. After reviewing various meanings of the term
``nonlocal'', we show that by using appropriately retarded wavefunctions (i.e.,
the locality loophole) this local model can violate Bell's inequality, without
making any appeal to detector inefficiencies.
We analyze a possible experimental configuration appropriate to massive
two-particle singlet wavefunctions and find that as long as the particles are
not ultra-relativistic, a locality loophole exists and Dirac wave(s) can
propagate from Alice or Bob's changing magnetic field, through space, to the
other detector, arriving before the particle and thereby allowing a local
interpretation to the 2-particle de Broglie-Bohm trajectories.
We also propose a physical effect due to changing magnetic fields in a
Stern-Gerlach EPR setup that will throw away events and create a detector
loophole in otherwise perfectly efficient detectors, an effect that is only
significant for near-luminal particles that might otherwise close the locality
loophole.
Journal: None |
Submitter: B. Scott Gaudi
Authors: Andrew Gould (OSU), B. Scott Gaudi (OSU), David P. Bennett (Notre
Dame)
Title: Ground-based Microlensing Surveys
Abstract: Microlensing is a proven extrasolar planet search method that has already
yielded the detection of four exoplanets. These detections have changed our
understanding of planet formation ``beyond the snowline'' by demonstrating that
Neptune-mass planets with separations of several AU are common. Microlensing is
sensitive to planets that are generally inaccessible to other methods, in
particular cool planets at or beyond the snowline, very low-mass (i.e.
terrestrial) planets, planets orbiting low-mass stars, free-floating planets,
and even planets in external galaxies. Such planets can provide critical
constraints on models of planet formation, and therefore the next generation of
extrasolar planet searches should include an aggressive and well-funded
microlensing component. When combined with the results from other complementary
surveys, next generation microlensing surveys can yield an accurate and
complete census of the frequency and properties of planets, and in particular
low-mass terrestrial planets.
Journal: None |
Submitter: Valeri Golev
Authors: I. M. Yankulova (1), V. K. Golev (1), K. Jockers (2) ((1) Department
of Astronomy, St Kliment Okhridski University of Sofia, Bulgaria (2)
Max-Planck-Institut fur Sonnensystemforschung, Germany)
Title: The luminous infrared composite Seyfert 2 galaxy NGC 7679 through the [O
III] 5007 emission line
Abstract: NGC 7679 is a nearby luminous infrared Sy2 galaxy in which starburst and AGN
activities co-exist. The ionization structure is maintained by both the AGN
power-law continuum and starburst. The galaxy is a bright X-ray source
possessing a low X-ray column density N_H < 4 x 10^20 cm^{-2}. The Compton-thin
nature of such unabsorbed objects infers that the simple formulation of the
Unified model for SyGs is not applicable in their case. The main goal of this
article is to investigate both gas distribution and ionization structure in the
circumnuclear region of NGC 7679 in search for the presence of a hidden Sy1
nucleus, using the [O III] 5007 luminosity as a tracer of AGN activity. The [O
III] 5007 image of the NGC 7679 shows elliptical isophotes extended along the
PA ~ 80 deg in the direction to the counterpart galaxy NGC 7682. The maximum of
ionization by the AGN power-law continuum traced by [O III] 5007/Halpha ratio
is displaced by ~ 13 arcsec eastward from the nucleus. We conclude that the
dust and gas in the high ionization direction has a direct view to the central
AGN engine. This possibly results in dust/star-formation decay. A large
fraction of the unabsorbed Compton-thin Sy2s with [O III] luminosity > 10^41
erg s^{-1} possesses a hidden AGN source (abridged).
Journal: Astronomy and Astrophysics, Volume 469, Issue 3, July III 2007,
pp.891-898 |
Submitter: Rajat Bhaduri
Authors: Michael Seidl and Rajat K. Bhaduri
Title: The Fermionic Density-functional at Feshbach Resonance
Abstract: We consider a dilute gas of neutral unpolarized fermionic atoms at zero
temperature.The atoms interact via a short range (tunable) attractive
interaction. We demonstrate analytically a curious property of the gas at
unitarity. Namely, the correlation energy of the gas, evaluated by second order
perturbation theory, has the same density dependence as the first order
exchange energy, and the two almost exactly cancel each other at Feshbach
resonance irrespective of the shape of the potential, provided $(\mu r_s) >>
1$. Here $(\mu)^{-1}$ is the range of the two-body potential, and $r_s$ is
defined through the number density $n=3/(4\pi r_s^3)$. The implications of this
result for universality is discussed.
Journal: None |
Submitter: Francesca Matteucci
Authors: Francesca Matteucci
Title: Chemical Evolution
Abstract: In this series of lectures we first describe the basic ingredients of
galactic chemical evolution and discuss both analytical and numerical models.
Then we compare model results for the Milky Way, Dwarf Irregulars, Quasars and
the Intra-Cluster- Medium with abundances derived from emission lines. These
comparisons allow us to put strong constraints on the stellar nucleosynthesis
and the mechanisms of galaxy formation.
Journal: None |
Submitter: Mikko Mottonen
Authors: Pekko Kuopanportti, Mikko Mottonen, Ville Bergholm, Olli-Pentti Saira,
Jun Zhang, and K. Birgitta Whaley
Title: Suppression of 1/f noise in one-qubit systems
Abstract: We investigate the generation of quantum operations for one-qubit systems
under classical noise with 1/f^\alpha power spectrum, where 2>\alpha > 0. We
present an efficient way to approximate the noise with a discrete multi-state
Markovian fluctuator. With this method, the average temporal evolution of the
qubit density matrix under 1/f^\alpha noise can be feasibly determined from
recently derived deterministic master equations. We obtain qubit operations
such as quantum memory and the NOT}gate to high fidelity by a gradient based
optimization algorithm. For the NOT gate, the computed fidelities are
qualitatively similar to those obtained earlier for random telegraph noise. In
the case of quantum memory however, we observe a nonmonotonic dependency of the
fidelity on the operation time, yielding a natural access rate of the memory.
Journal: Phys. Rev. A 77, 032334 (2008) |
Submitter: Sebastien Zimmermann
Authors: Sebastien Zimmermann
Title: Stability of a colocated finite volume scheme for the incompressible
Navier-Stokes equations
Abstract: We introduce a finite volume scheme for the two-dimensional incompressible
Navier-Stokes equations. We use a triangular mesh. The unknowns for the
velocity and pressure are both piecewise constant (colocated scheme). We use a
projection (fractional-step) method to deal with the incompressibility
constraint. We prove that the differential operators in the Navier-Stokes
equations and their discrete counterparts share similar properties. In
particular, we state an inf-sup (Babuska-Brezzi) condition. We infer from it
the stability of the scheme.
Journal: None |
Submitter: Raj Kumar Pan
Authors: Raj Kumar Pan and Sitabhra Sinha
Title: Collective behavior of stock price movements in an emerging market
Abstract: To investigate the universality of the structure of interactions in different
markets, we analyze the cross-correlation matrix C of stock price fluctuations
in the National Stock Exchange (NSE) of India. We find that this emerging
market exhibits strong correlations in the movement of stock prices compared to
developed markets, such as the New York Stock Exchange (NYSE). This is shown to
be due to the dominant influence of a common market mode on the stock prices.
By comparison, interactions between related stocks, e.g., those belonging to
the same business sector, are much weaker. This lack of distinct sector
identity in emerging markets is explicitly shown by reconstructing the network
of mutually interacting stocks. Spectral analysis of C for NSE reveals that,
the few largest eigenvalues deviate from the bulk of the spectrum predicted by
random matrix theory, but they are far fewer in number compared to, e.g., NYSE.
We show this to be due to the relative weakness of intra-sector interactions
between stocks, compared to the market mode, by modeling stock price dynamics
with a two-factor model. Our results suggest that the emergence of an internal
structure comprising multiple groups of strongly coupled components is a
signature of market development.
Journal: Phys. Rev. E 76, 046116 (2007) (9 pages) |
Submitter: Kyle Lane
Authors: K. P. Lane, M. E. Gray, A. Aragon-Salamanca, C. Wolf and K.
Meisenheimer
Title: Galaxy morphologies and environment in the Abell 901/902 supercluster
from COMBO-17
Abstract: We present a morphological study of galaxies in the A901/902 supercluster
from the COMBO-17 survey. A total of 570 galaxies with photometric redshifts in
the range 0.155 < z_phot < 0.185 are visually classified by three independent
classifiers to M_V=-18. These morphological classifications are compared to
local galaxy density, distance from the nearest cluster centre, local surface
mass density from weak lensing, and photometric classification. At high local
galaxy densities, log(Sigma_10 /Mpc^2) > 1.5, a classical morphology-density
relation is found. A correlation is also found between morphology and local
projected surface mass density, but no trend is observed with distance to the
nearest cluster. This supports the finding that local environment is more
important to galaxy morphology than global cluster properties. The breakdown of
the morphological catalogue by colour shows a dominance of blue galaxies in the
galaxies displaying late-type morphologies and a corresponding dominance of red
galaxies in the early-type population. Using the 17-band photometry from
COMBO-17, we further split the supercluster red sequence into old passive
galaxies and galaxies with young stars and dust according to the prescription
of Wolf et al. (2005). We find that the dusty star-forming population describes
an intermediate morphological group between late-type and early-type galaxies,
supporting the hypothesis that field and group spiral galaxies are transformed
into S0s and, perhaps, ellipticals during cluster infall.
Journal: Mon.Not.Roy.Astron.Soc.378:716-722,2007 |
Submitter: Efton Park
Authors: Efton Park and Jody Trout
Title: K_0-theory of n-potents in rings and algebras
Abstract: Let $n \geq 2$ be an integer. An \emph{$n$-potent} is an element $e$ of a
ring $R$ such that $e^n = e$. In this paper, we study $n$-potents in matrices
over $R$ and use them to construct an abelian group $K_0^n(R)$. If $A$ is a
complex algebra, there is a group isomorphism $K_0^n(A) \cong
\bigl(K_0(A)\bigr)^{n-1}$ for all $n \geq 2$. However, for algebras over
cyclotomic fields, this is not true in general. We consider $K_0^n$ as a
covariant functor, and show that it is also functorial for a generalization of
homomorphism called an \emph{$n$-homomorphism}.
Journal: None |
Submitter: Alexios D. Klironomos
Authors: A. D. Klironomos, Julia S. Meyer, T. Hikihara, K. A. Matveev
Title: Spin coupling in zigzag Wigner crystals
Abstract: We consider interacting electrons in a quantum wire in the case of a shallow
confining potential and low electron density. In a certain range of densities,
the electrons form a two-row (zigzag) Wigner crystal whose spin properties are
determined by nearest and next-nearest neighbor exchange as well as by three-
and four-particle ring exchange processes. The phase diagram of the resulting
zigzag spin chain has regions of complete spin polarization and partial spin
polarization in addition to a number of unpolarized phases, including
antiferromagnetism and dimer order as well as a novel phase generated by the
four-particle ring exchange.
Journal: Phys. Rev. B 76, 075302 (2007) |
Submitter: John H. Schwarz
Authors: Michael B. Green, Hirosi Ooguri, and John H. Schwarz
Title: Decoupling Supergravity from the Superstring
Abstract: We consider the conditions necessary for obtaining perturbative maximal
supergravity in d dimensions as a decoupling limit of type II superstring
theory compactified on a (10 -- d)-torus. For dimensions d = 2 and d = 3 it is
possible to define a limit in which the only finite-mass states are the 256
massless states of maximal supergravity. However, in dimensions d > 3 there are
infinite towers of additional massless and finite-mass states. These correspond
to Kaluza--Klein charges, wound strings, Kaluza--Klein monopoles or branes
wrapping around cycles of the toroidal extra dimensions. We conclude that
perturbative supergravity cannot be decoupled from string theory in dimensions
d > 3. In particular, we conjecture that pure N = 8 supergravity in four
dimensions is in the Swampland.
Journal: Phys.Rev.Lett.99:041601,2007 |
Submitter: Xuhua He
Authors: Xuhua He and Jesper Funch Thomsen
Title: Frobenius splitting and geometry of $G$-Schubert varieties
Abstract: Let $X$ be an equivariant embedding of a connected reductive group $G$ over
an algebraically closed field $k$ of positive characteristic. Let $B$ denote a
Borel subgroup of $G$. A $G$-Schubert variety in $X$ is a subvariety of the
form $\diag(G) \cdot V$, where $V$ is a $B \times B$-orbit closure in $X$. In
the case where $X$ is the wonderful compactification of a group of adjoint
type, the $G$-Schubert varieties are the closures of Lusztig's $G$-stable
pieces. We prove that $X$ admits a Frobenius splitting which is compatible with
all $G$-Schubert varieties. Moreover, when $X$ is smooth, projective and
toroidal, then any $G$-Schubert variety in $X$ admits a stable Frobenius
splitting along an ample divisors. Although this indicates that $G$-Schubert
varieties have nice singularities we present an example of a non-normal
$G$-Schubert variety in the wonderful compactification of a group of type
$G_2$. Finally we also extend the Frobenius splitting results to the more
general class of $\mathcal R$-Schubert varieties.
Journal: None |
Submitter: Markos Georganopoulos
Authors: Philip B. Graff, Markos Georganopoulos, Eric S. Perlman, Demosthenes
Kazanas
Title: High Energy Variability Of Synchrotron-Self Compton Emitting Sources:
Why One Zone Models Do Not Work And How We Can Fix It
Abstract: With the anticipated launch of GLAST, the existing X-ray telescopes, and the
enhanced capabilities of the new generation of TeV telescopes, developing tools
for modeling the variability of high energy sources such as blazars is becoming
a high priority. We point out the serious, innate problems one zone
synchrotron-self Compton models have in simulating high energy variability. We
then present the first steps toward a multi zone model where non-local, time
delayed Synchrotron-self Compton electron energy losses are taken into account.
By introducing only one additional parameter, the length of the system, our
code can simulate variability properly at Compton dominated stages, a situation
typical of flaring systems. As a first application, we were able to reproduce
variability similar to that observed in the case of the puzzling `orphan' TeV
flares that are not accompanied by a corresponding X-ray flare.
Journal: AIP Conf.Proc.921:333-334,2007 |
Submitter: Felix Liang
Authors: J. F. Liang, D. Shapira, J. R. Beene, C. J. Gross, R. L. Varner, A.
Galindo-Uribarri, J. Gomez del Campo, P. A. Hausladen, P. E. Mueller, D. W.
Stracener, H. Amro, J. J. Kolata, J. D. Bierman, A. L. Caraley, K. L. Jones,
Y. Larochelle, W. Loveland, D. Peterson
Title: Fusion of radioactive $^{132}$Sn with $^{64}$Ni
Abstract: Evaporation residue and fission cross sections of radioactive $^{132}$Sn on
$^{64}$Ni were measured near the Coulomb barrier. A large sub-barrier fusion
enhancement was observed. Coupled-channel calculations including inelastic
excitation of the projectile and target, and neutron transfer are in good
agreement with the measured fusion excitation function. When the change in
nuclear size and shift in barrier height are accounted for, there is no extra
fusion enhancement in $^{132}$Sn+$^{64}$Ni with respect to stable Sn+$^{64}$Ni.
A systematic comparison of evaporation residue cross sections for the fusion of
even $^{112-124}$Sn and $^{132}$Sn with $^{64}$Ni is presented.
Journal: Phys.Rev.C75:054607,2007 |
Submitter: Alison Hatt
Authors: Alison J. Hatt and Nicola A. Spaldin
Title: Tri-layer superlattices: A route to magnetoelectric multiferroics?
Abstract: We explore computationally the formation of tri-layer superlattices as an
alternative approach for combining ferroelectricity with magnetism to form
magnetoelectric multiferroics. We find that the contribution to the
superlattice polarization from tri-layering is small compared to typical
polarizations in conventionalferroelectrics, and the switchable ferroelectric
component is negligible. In contrast, we show that epitaxial strain and
``negative pressure'' can yield large, switchable polarizations that are
compatible with the coexistence of magnetism, even in materials with no active
ferroelectric ions.
Journal: Appl. Phys. Lett. 90, 242916 (2007) |
Submitter: Oliver Rinne
Authors: Oliver Rinne, Lee Lindblom and Mark A. Scheel
Title: Testing outer boundary treatments for the Einstein equations
Abstract: Various methods of treating outer boundaries in numerical relativity are
compared using a simple test problem: a Schwarzschild black hole with an
outgoing gravitational wave perturbation. Numerical solutions computed using
different boundary treatments are compared to a `reference' numerical solution
obtained by placing the outer boundary at a very large radius. For each
boundary treatment, the full solutions including constraint violations and
extracted gravitational waves are compared to those of the reference solution,
thereby assessing the reflections caused by the artificial boundary. These
tests use a first-order generalized harmonic formulation of the Einstein
equations. Constraint-preserving boundary conditions for this system are
reviewed, and an improved boundary condition on the gauge degrees of freedom is
presented. Alternate boundary conditions evaluated here include freezing the
incoming characteristic fields, Sommerfeld boundary conditions, and the
constraint-preserving boundary conditions of Kreiss and Winicour. Rather
different approaches to boundary treatments, such as sponge layers and spatial
compactification, are also tested. Overall the best treatment found here
combines boundary conditions that preserve the constraints, freeze the
Newman-Penrose scalar Psi_0, and control gauge reflections.
Journal: Class.Quant.Grav.24:4053-4078,2007 |
Submitter: Sebastien Zimmermann
Authors: Sebastien Zimmermann
Title: Stability of a finite volume scheme for the incompressible fluids
Abstract: We introduce a finite volume scheme for the two-dimensional incompressible
Navier-Stokes equations. We use a triangular mesh. The unknowns for the
velocity and pressure are respectively piecewise constant and affine. We use a
projection method to deal with the incompressibility constraint. We show that
the differential operators in the Navier-Stokes equations and their discrete
counterparts share similar properties. In particular we state an inf-sup
(Babuska-Brezzi) condition. Using these properties we infer the stability of
the scheme.
Journal: None |
Submitter: Massimo Bianchi
Authors: Massimo Bianchi, Francesco Fucito and Jose F. Morales
Title: D-brane Instantons on the T^6/Z_3 orientifold
Abstract: We give a detailed microscopic derivation of gauge and stringy instanton
generated superpotentials for gauge theories living on D3-branes at
Z_3-orientifold singularities. Gauge instantons are generated by D(-1)-branes
and lead to Affleck, Dine and Seiberg (ADS) like superpotentials in the
effective N=1 gauge theories with three generations of bifundamental and
anti/symmetric matter. Stringy instanton effects are generated by Euclidean
ED3-branes wrapping four-cycles on T^6/\Z_3. They give rise to Majorana masses
in one case and non-renormalizable superpotentials for the other cases. Finally
we determine the conditions under which ADS like superpotentials are generated
in N=1 gauge theories with adjoints, fundamentals, symmetric and antisymmetric
chiral matter.
Journal: JHEP0707:038,2007 |
Submitter: Viviane Turq
Authors: Viviane Turq (LTDS), Julien Fontaine (LTDS), Jean-Luc Loubet (LTDS),
Denis Mazuyer (LTDS)
Title: Viscoplastic Properties and Tribological Behavior of Diamond-Like Carbon
Films Using Nanoindentation and Nanoscratch Tests
Abstract: Diamond-Like Carbon (DLC) films have been shown to demonstrate various
tribological behaviors: in ultra-high vacuum (UHV), with either friction
coefficients as low as 0.01 or less and very mild wear, or very high friction
coefficients (>0.4) and drastic wear. These behaviors depend notably on gaseous
environment, hydrogen content of the film [1], and on its viscoplastic
properties [2,3]. A relation between superlow friction in UHV and
viscoplasticity has indeed been established for a-C:H films and confirmed for a
fluorinated sample (a-C:F:H). In this study, nanoindentation and nanoscratch
tests were conducted in ambient air, using a nanoindentation apparatus, in
order to evaluate tribological behaviors, as well as mechanical and
viscoplastic properties of different amorphous carbon films.
Journal: Synopses of the International Tribology Conference (ITC) Kobe,
2005 (29/05/2005) A-39 |
Submitter: Patricia Ball
Authors: Patricia Ball
Title: Implication of the D^0 Width Difference On CP-Violation in D^0-\bar D^0
Mixing
Abstract: Both BaBar and Belle have found evidence for a non-zero width difference in
the $D^0$-$\bar D^0$ system. Although there is no direct experimental evidence
for CP-violation in $D$ mixing (yet), we show that the measured values of the
width difference $y\sim \Delta\Gamma$ already imply constraints on the
CP-violating phase in $D$ mixing, which, if significantly different from zero,
would be an unambiguous signal of new physics.
Journal: J.Phys.G34:2199-2206,2007 |
Submitter: Sebastien Zimmermann
Authors: Sebastien Zimmermann
Title: Convergence of a finite volume scheme for the incompressible fluids
Abstract: We consider a finite volume scheme for the two-dimensional incompressible
Navier-Stokes equations. We use a triangular mesh. The unknowns for the
velocity and pressure are respectively piecewise constant and affine. We use a
projection method to deal with the incompressibility constraint. In a former
paper, the stability of the scheme has been proven. We infer from it its
convergence.
Journal: None |
Submitter: Kerry Soileau
Authors: Kerry M. Soileau
Title: Optimal Synthesis of Multiple Algorithms
Abstract: In this paper we give a definition of "algorithm," "finite algorithm,"
"equivalent algorithms," and what it means for a single algorithm to dominate a
set of algorithms. We define a derived algorithm which may have a smaller mean
execution time than any of its component algorithms. We give an explicit
expression for the mean execution time (when it exists) of the derived
algorithm. We give several illustrative examples of derived algorithms with two
component algorithms. We include mean execution time solutions for
two-algorithm processors whose joint density of execution times are of several
general forms. For the case in which the joint density for a two-algorithm
processor is a step function, we give a maximum-likelihood estimation scheme
with which to analyze empirical processing time data.
Journal: None |
Submitter: Nicole Silvestri
Authors: Nicole M. Silvestri(1), Mara P. Lemagie(1), Suzanne L. Hawley(1),
Andrew A. West(2), Gary D. Schmidt(3), James Liebert(3), Paula Szkody(1), Lee
Mannikko(1), Michael A. Wolfe(1), J. C. Barentine(4), Howard J.
Brewington(4), Michael Harvanek(4), Jurik Krzesinski(5), Dan Long(4), Donald
P. Schneider(6), and Stephanie A. Snedden(4) ((1) University of Washington;
(2) University of California, Berkeley; (3) University of Arizona and Steward
Observatory; (4) Apache Point Observatory; (5) Mt. Suhora Observatory, Cracow
Pedagogical University; (6) Penn State University)
Title: New Close Binary Systems from the SDSS-I (Data Release Five) and the
Search for Magnetic White Dwarfs in Cataclysmic Variable Progenitor Systems
Abstract: We present the latest catalog of more than 1200 spectroscopically-selected
close binary systems observed with the Sloan Digital Sky Survey through Data
Release Five. We use the catalog to search for magnetic white dwarfs in
cataclysmic variable progenitor systems. Given that approximately 25% of
cataclysmic variables contain a magnetic white dwarf, and that our large sample
of close binary systems should contain many progenitors of cataclysmic
variables, it is quite surprising that we find only two potential magnetic
white dwarfs in this sample. The candidate magnetic white dwarfs, if confirmed,
would possess relatively low magnetic field strengths (B_WD < 10 MG) that are
similar to those of intermediate-Polars but are much less than the average
field strength of the current Polar population. Additional observations of
these systems are required to definitively cast the white dwarfs as magnetic.
Even if these two systems prove to be the first evidence of detached magnetic
white dwarf + M dwarf binaries, there is still a large disparity between the
properties of the presently known cataclysmic variable population and the
presumed close binary progenitors.
Journal: Astron.J.134:741-748,2007 |
Submitter: Ruth Durrer
Authors: Marcus Ruser and Ruth Durrer
Title: Dynamical Casimir effect for gravitons in bouncing braneworlds
Abstract: We consider a two-brane system in a five-dimensional anti-de Sitter
spacetime. We study particle creation due to the motion of the physical brane
which first approaches the second static brane (contraction) and then recedes
from it(expansion). The spectrum and the energy density of the generated
gravitons are calculated. We show that the massless gravitons have a blue
spectrum and that their energy density satisfies the nucleosynthesis bound with
very mild constraints on the parameters. We also show that the Kaluza-Klein
modes cannot provide the dark matter in an anti-de-Sitter braneworld. However,
for natural choices of parameters, backreaction from the Kaluza-Klein gravitons
may well become important. The main findings of this work have been published
in the form of a Letter [R. Durrer and M. Ruser, Phys. Rev. Lett. 99, 071601
(2007), arXiv:0704.0756].
Journal: Phys.Rev.D76:104014,2007 |
Submitter: Vladimir Avila-Reese
Authors: J. I. Cabrera (1), C. Firmani (2,1), V. Avila-Reese (1), G. Ghirlanda
(2), G. Ghisellini (2), L. Nava (2,3) ((1)U.N.A.M., (2)INAF-OAB, (3)Univ.
Insubria)
Title: Spectral analysis of Swift long GRBs with known redshift
Abstract: We study the spectral and energetics properties of 47 long-duration gamma-ray
bursts (GRBs) with known redshift, all of them detected by the Swift satellite.
Due to the narrow energy range (15-150 keV) of the Swift-BAT detector, the
spectral fitting is reliable only for fitting models with 2 or 3 parameters. As
high uncertainty and correlation among the errors is expected, a careful
analysis of the errors is necessary. We fit both the power law (PL, 2
parameters) and cut--off power law (CPL, 3 parameters) models to the
time-integrated spectra of the 47 bursts, and present the corresponding
parameters, their uncertainties, and the correlations among the uncertainties.
The CPL model is reliable only for 29 bursts for which we estimate the nuf_nu
peak energy Epk. For these GRBs, we calculate the energy fluence and the rest-
frame isotropic-equivalent radiated energy, Eiso, as well as the propagated
uncertainties and correlations among them. We explore the distribution of our
homogeneous sample of GRBs on the rest-frame diagram E'pk vs Eiso. We confirm a
significant correlation between these two quantities (the "Amati" relation) and
we verify that, within the uncertainty limits, no outliers are present. We also
fit the spectra to a Band model with the high energy power law index frozen to
-2.3, obtaining a rather good agreement with the "Amati" relation of non-Swift
GRBs.
Journal: Mon.Not.Roy.Astron.Soc.382:342-355, 2007 |
Submitter: Mark R. Krumholz
Authors: Mark R. Krumholz and Todd A. Thompson (Princeton University)
Title: The Relationship Between Molecular Gas Tracers and Kennicutt-Schmidt
Laws
Abstract: We provide a model for how Kennicutt-Schmidt (KS) laws, which describe the
correlation between star formation rate and gas surface or volume density,
depend on the molecular line chosen to trace the gas. We show that, for lines
that can be excited at low temperatures, the KS law depends on how the line
critical density compares to the median density in a galaxy's star-forming
molecular clouds. High critical density lines trace regions with similar
physical properties across galaxy types, and this produces a linear correlation
between line luminosity and star formation rate. Low critical density lines
probe regions whose properties vary across galaxies, leading to a star
formation rate that varies superlinearly with line luminosity. We show that a
simple model in which molecular clouds are treated as isothermal and homogenous
can quantitatively reproduce the observed correlations between galactic
luminosities in far infrared and in the CO(1->0) and HCN(1->0) lines, and
naturally explains why these correlations have different slopes. We predict
that IR-line luminosity correlations should change slope for galaxies in which
the median density is close to the line critical density. This prediction may
be tested by observations of lines such as HCO^+(1->0) with intermediate
critical densities, or by HCN(1->0) observations of intensely star-forming high
redshift galaxies with very high densities. Recent observations by Gao et al.
hint at just such a change in slope. We argue that deviations from linearity in
the HCN(1->0)-IR correlation at high luminosity are consistent with the
assumption of a constant star formation efficiency.
Journal: None |
Submitter: Yungui Gong
Authors: Yungui Gong and Anzhong Wang
Title: Friedmann Equations and Thermodynamics of Apparent Horizons
Abstract: With the help of a masslike function which has dimension of energy and equals
to the Misner-Sharp mass at the apparent horizon, we show that the first law of
thermodynamics of the apparent horizon $dE=T_AdS_A$ can be derived from the
Friedmann equation in various theories of gravity, including the Einstein,
Lovelock, nonlinear, and scalar-tensor theories. This result strongly suggests
that the relationship between the first law of thermodynamics of the apparent
horizon and the Friedmann equation is not just a simple coincidence, but rather
a more profound physical connection.
Journal: Phys.Rev.Lett.99:211301,2007 |
Submitter: Adrienne Erickcek
Authors: Adrienne L. Erickcek (1), Paul J. Steinhardt (2), Dan McCammon (3),
Patrick C. McGuire (4)((1)Caltech, (2)Princeton University, (3)University of
Wisconsin, (4)Washington University)
Title: Constraints on the Interactions between Dark Matter and Baryons from the
X-ray Quantum Calorimetry Experiment
Abstract: Although the rocket-based X-ray Quantum Calorimetry (XQC) experiment was
designed for X-ray spectroscopy, the minimal shielding of its calorimeters, its
low atmospheric overburden, and its low-threshold detectors make it among the
most sensitive instruments for detecting or constraining strong interactions
between dark matter particles and baryons. We use Monte Carlo simulations to
obtain the precise limits the XQC experiment places on spin-independent
interactions between dark matter and baryons, improving upon earlier analytical
estimates. We find that the XQC experiment rules out a wide range of
nucleon-scattering cross sections centered around one barn for dark matter
particles with masses between 0.01 and 10^5 GeV. Our analysis also provides new
constraints on cases where only a fraction of the dark matter strongly
interacts with baryons.
Journal: Phys.Rev.D76:042007,2007 |
Submitter: Christopher Aubin
Authors: C. Aubin and C. Bernard
Title: Heavy-Light Semileptonic Decays in Staggered Chiral Perturbation Theory
Abstract: We calculate the form factors for the semileptonic decays of heavy-light
pseudoscalar mesons in partially quenched staggered chiral perturbation theory
(\schpt), working to leading order in $1/m_Q$, where $m_Q$ is the heavy quark
mass. We take the light meson in the final state to be a pseudoscalar
corresponding to the exact chiral symmetry of staggered quarks. The treatment
assumes the validity of the standard prescription for representing the
staggered ``fourth root trick'' within \schpt by insertions of factors of 1/4
for each sea quark loop. Our calculation is based on an existing partially
quenched continuum chiral perturbation theory calculation with degenerate sea
quarks by Becirevic, Prelovsek and Zupan, which we generalize to the staggered
(and non-degenerate) case. As a by-product, we obtain the continuum partially
quenched results with non-degenerate sea quarks. We analyze the effects of
non-leading chiral terms, and find a relation among the coefficients governing
the analytic valence mass dependence at this order. Our results are useful in
analyzing lattice computations of form factors $B\to\pi$ and $D\to K$ when the
light quarks are simulated with the staggered action.
Journal: Phys.Rev.D76:014002,2007 |
Submitter: Stephen Adler
Authors: Stephen L. Adler
Title: A density tensor hierarchy for open system dynamics: retrieving the
noise
Abstract: We introduce a density tensor hierarchy for open system dynamics, that
recovers information about fluctuations lost in passing to the reduced density
matrix. For the case of fluctuations arising from a classical probability
distribution, the hierarchy is formed from expectations of products of pure
state density matrix elements, and can be compactly summarized by a simple
generating function. For the case of quantum fluctuations arising when a
quantum system interacts with a quantum environment in an overall pure state,
the corresponding hierarchy is defined as the environmental trace of products
of system matrix elements of the full density matrix. Only the lowest member of
the quantum noise hierarchy is directly experimentally measurable. The unit
trace and idempotence properties of the pure state density matrix imply descent
relations for the tensor hierarchies, that relate the order $n$ tensor, under
contraction of appropriate pairs of tensor indices, to the order $n-1$ tensor.
As examples to illustrate the classical probability distribution formalism, we
consider a quantum system evolving by It\^o stochastic and by jump process
Schr\"odinger equations. As examples to illustrate the corresponding trace
formalism in the quantum fluctuation case, we consider collisional Brownian
motion of an infinite mass Brownian particle, and the weak coupling Born-Markov
master equation. In different specializations, the latter gives the hierarchies
generalizing the quantum optical master equation and the Caldeira--Leggett
master equation. As a further application of the density tensor, we contrast
stochastic Schr\"odinger equations that reduce and that do not reduce the state
vector, and discuss why a quantum system coupled to a quantum environment
behaves like the latter.
Journal: J.Phys.A40:8959-8990,2007 |
Submitter: Roland Haas
Authors: Roland Haas
Title: Scalar self-force on eccentric geodesics in Schwarzschild spacetime: a
time-domain computation
Abstract: We calculate the self-force acting on a particle with scalar charge moving on
a generic geodesic around a Schwarzschild black hole. This calculation requires
an accurate computation of the retarded scalar field produced by the moving
charge; this is done numerically with the help of a fourth-order convergent
finite-difference scheme formulated in the time domain. The calculation also
requires a regularization procedure, because the retarded field is singular on
the particle's world line; this is handled mode-by-mode via the mode-sum
regularization scheme first introduced by Barack and Ori. This paper presents
the numerical method, various numerical tests, and a sample of results for
mildly eccentric orbits as well as ``zoom-whirl'' orbits.
Journal: Phys.Rev.D75:124011,2007 |
Submitter: Donald M. Davis
Authors: Donald M. Davis and Mark Mahowald
Title: Nonimmersions of RP^n implied by tmf, revisited
Abstract: In a 2002 paper, the authors and Bruner used the new spectrum tmf to obtain
some new nonimmersions of real projective spaces. In this note, we
complete/correct two oversights in that paper.
The first is to note that in that paper a general nonimmersion result was
stated which yielded new nonimmersions for RP^n with n as small as 48, and yet
it was stated there that the first new result occurred when n=1536. Here we
give a simple proof of those overlooked results.
Secondly, we fill in a gap in the proof of the 2002 paper. There it was
claimed that an axial map f must satisfy f^*(X)=X_1+X_2. We realized recently
that this is not clear. However, here we show that it is true up multiplication
by a unit in the appropriate ring, and so we retrieve all the nonimmersion
results claimed in the original paper.
Finally, we present a complete determination of tmf^{8*}(RP^\infty\times
RP^\infty) and tmf^*(CP^\infty\times CP^\infty) in positive dimensions.
Journal: None |
Submitter: Ruxandra Bondarescu
Authors: Ruxandra Bondarescu, Saul A. Teukolsky and Ira Wasserman (Cornell
University)
Title: Spin Evolution of Accreting Neutron Stars: Nonlinear Development of the
R-mode Instability
Abstract: The nonlinear saturation of the r-mode instability and its effects on the
spin evolution of Low Mass X-ray Binaries (LMXBs) are modeled using the triplet
of modes at the lowest parametric instability threshold. We solve numerically
the coupled equations for the three mode amplitudes in conjunction with the
spin and temperature evolution equations. We observe that very quickly the mode
amplitudes settle into quasi-stationary states. Once these states are reached,
the mode amplitudes can be found algebraically and the system of equations is
reduced from eight to two equations: spin and temperature evolution.
Eventually, the system may reach thermal equilibrium and either (1) undergo a
cyclic evolution with a frequency change of at most 10%, (2) evolve toward a
full equilibrium state in which the accretion torque balances the gravitational
radiation emission, or (3) enter a thermogravitational runaway on a very long
timescale of about $10^6$ years. Alternatively, a faster thermal runaway
(timescale of about 100 years) may occur. The sources of damping considered are
shear viscosity, hyperon bulk viscosity and boundary layer viscosity. We vary
proprieties of the star such as the hyperon superfluid transition temperature
T_c, the fraction of the star that is above the threshold for direct URCA
reactions, and slippage factor, and map the different scenarios we obtain to
ranges of these parameters. For all our bound evolutions the r-mode amplitude
remains small $\sim 10^{-5}$. The spin frequency is limited by boundary layer
viscosity to $\nu_{max} \sim 800 Hz [S_{ns}/(M_{1.4} R_6)]^{4/11} T_8^{-2/11}$.
We find that for $\nu > 700$ Hz the r-mode instability would be active for
about 1 in 1000 LMXBs and that only the gravitational waves from LMXBs in the
local group of galaxies could be detected by advanced LIGO interferometers.
Journal: Phys.Rev.D76:064019,2007 |
Submitter: Tad Hogg
Authors: Tad Hogg, Pavithra Harsha and Kay-Yut Chen
Title: Quantum Auctions
Abstract: We present a quantum auction protocol using superpositions to represent bids
and distributed search to identify the winner(s). Measuring the final quantum
state gives the auction outcome while simultaneously destroying the
superposition. Thus non-winning bids are never revealed. Participants can use
entanglement to arrange for correlations among their bids, with the assurance
that this entanglement is not observable by others. The protocol is useful for
information hiding applications, such as partnership bidding with allocative
externality or concerns about revealing bidding preferences. The protocol
applies to a variety of auction types, e.g., first or second price, and to
auctions involving either a single item or arbitrary bundles of items (i.e.,
combinatorial auctions). We analyze the game-theoretical behavior of the
quantum protocol for the simple case of a sealed-bid quantum, and show how a
suitably designed adiabatic search reduces the possibilities for bidders to
game the auction. This design illustrates how incentive rather that
computational constraints affect quantum algorithm choices.
Journal: Intl. J. of Quantum Information 5:751-780 (2007) |