2,058 research outputs found
Growing length and time scales in a suspension of athermal particles
We simulate a relaxation process of non-brownian particles in a sheared
viscous medium; the small shear strain is initially applied to a system, which
then undergoes relaxation. The relaxation time and the correlation length are
estimated as functions of density, which algebraically diverge at the jamming
density. This implies that the relaxation time can be scaled by the correlation
length using the dynamic critical exponent, which is estimated as 4.6(2). It is
also found that shear stress undergoes power-law decay at the jamming density,
which is reminiscent of critical slowing down
Astrophysical Condition on the attolensing as a possible probe for a modified gravity theory
We investigate the wave effect in the gravitational lensing by a black hole
with very tiny mass less than 10^-19 solar mass, which is called attolensing,
motivated by a recent report that the lensing signature might be a possible
probe of a modified gravity theory in the braneworld scenario. We focus on the
finite source size effect and the effect of the relative motion of the source
to the lens, which are influential to the wave effect in the attolensing.
Astrophysical condition that the lensed interference signature can be a probe
of the modified gravity theory is demonstrated. The interference signature in
the microlensing system is also discussed.Comment: Accepted for publication in IJMP
Novel Extrapolation Method in the Monte Carlo Shell Model
We propose an extrapolation method utilizing energy variance in the Monte
Carlo shell model in order to estimate the energy eigenvalue and observables
accurately. We derive a formula for the energy variance with deformed Slater
determinants, which enables us to calculate the energy variance efficiently.
The feasibility of the method is demonstrated for the full -shell
calculation of Ni, and the applicability of the method to a system
beyond current limit of exact diagonalization is shown for the
+-shell calculation of Ge.Comment: 4 pages, 4figure
Forecasting the Cosmological Constraints with Anisotropic Baryon Acoustic Oscillations from Multipole Expansion
Baryon acoustic oscillations (BAOs) imprinted in the galaxy power spectrum
can be used as a standard ruler to determine angular diameter distance and
Hubble parameter at high redshift galaxies. Combining redshift distortion
effect which apparently distorts the galaxy clustering pattern, we can also
constrain the growth rate of large-scale structure formation. Usually, future
forecast for constraining these parameters from galaxy redshift surveys has
been made with a full 2D power spectrum characterized as function of wavenumber
and directional cosine between line-of-sight direction and wave
vector, i.e., . Here, we apply the multipole expansion to the full 2D
power spectrum, and discuss how much cosmological information can be extracted
from the lower-multipole spectra, taking a proper account of the non-linear
effects on gravitational clustering and redshift distortion. The Fisher matrix
analysis reveals that compared to the analysis with full 2D spectrum, a partial
information from the monopole and quadrupole spectra generally degrades the
constraints by a factor of for each parameter. The additional
information from the hexadecapole spectrum helps to improve the constraints,
which lead to an almost comparable result expected from the full 2D spectrum.Comment: 12 pages, 6 figure
Shape-invariant potentials and an associated coherent state
An algebraic treatment of shape-invariant potentials in supersymmetric
quantum mechanics is discussed. By introducing an operator which reparametrizes
wave functions, the shape-invariance condition can be related to a
oscillator-like algebra. It makes possible to define a coherent state
associated with the shape-invariant potentials. For a large class of such
potentials, it is shown that the introduced coherent state has the property of
resolution of unity.Comment: 11 pages + 1 figure (not included),Plain Tex YITP/K-1019, RCNP-05
Thermally Assisted Penetration and Exclusion of Single Vortex in Mesoscopic Superconductors
A single vortex overcoming the surface barrier in a mesoscopic superconductor
with lateral dimensions of several coherence lengths and thickness of several
nanometers provides an ideal platform to study thermal activation of a single
vortex. In the presence of thermal fluctuations, there is non-zero probability
for vortex penetration into or exclusion from the superconductor even when the
surface barrier does not vanish. We consider the thermal activation of a single
vortex in a mesoscopic superconducting disk of circular shape. To obtain
statistics for the penetration and exclusion magnetic fields, slow and periodic
magnetic fields are applied to the superconductor. We calculate the
distribution of the penetration and exclusion fields from the thermal
activation rate. This distribution can also be measured experimentally, which
allows for a quantitative comparison.Comment: 7 pages, 4 figure
Void-induced cross slip of screw dislocations in fcc copper
Pinning interaction between a screw dislocation and a void in fcc copper is
investigated by means of molecular dynamics simulation. A screw dislocation
bows out to undergo depinning on the original glide plane at low temperatures,
where the behavior of the depinning stress is consistent with that obtained by
a continuum model. If the temperature is higher than 300 K, the motion of a
screw dislocation is no longer restricted to a single glide plane due to cross
slip on the void surface. Several depinning mechanisms that involve multiple
glide planes are found. In particular, a depinning mechanism that produces an
intrinsic prismatic loop is found. We show that these complex depinning
mechanisms significantly increase the depinning stress
Radial Bargmann representation for the Fock space of type B
Let be the probability and orthogonality measure for the
-Meixner-Pollaczek orthogonal polynomials, which has appeared in
\cite{BEH15} as the distribution of the -Gaussian process (the
Gaussian process of type B) over the -Fock space (the Fock space of
type B). The main purpose of this paper is to find the radial Bargmann
representation of . Our main results cover not only the
representation of -Gaussian distribution by \cite{LM95}, but also of
-Gaussian and symmetric free Meixner distributions on . In
addition, non-trivial commutation relations satisfied by -operators
are presented.Comment: 13 pages, minor changes have been mad
Can distributed delays perfectly stabilize dynamical networks?
Signal transmission delays tend to destabilize dynamical networks leading to
oscillation, but their dispersion contributes oppositely toward stabilization.
We analyze an integro-differential equation that describes the collective
dynamics of a neural network with distributed signal delays. With the gamma
distributed delays less dispersed than exponential distribution, the system
exhibits reentrant phenomena, in which the stability is once lost but then
recovered as the mean delay is increased. With delays dispersed more highly
than exponential, the system never destabilizes.Comment: 4pages 5figure
Energy dissipation and violation of the fluctuation-response relation in non-equilibrium Langevin systems
The fluctuation-response relation is a fundamental relation that is
applicable to systems near equilibrium. On the other hand, when a system is
driven far from equilibrium, this relation is violated in general because the
detailed-balance condition is not satisfied in nonequilibrium systems. Even in
this case, it has been found that for a class of Langevin equations, there
exists an equality between the extent of violation of the fluctuation-response
relation in the nonequilibrium steady state and the rate of energy dissipation
from the system into the environment [T. Harada and S. -i. Sasa, Phys. Rev.
Lett. 95, 130602 (2005)]. Since this equality involves only experimentally
measurable quantities, it serves as a proposition to determine experimentally
whether the system can be described by a Langevin equation. Furthermore, the
contribution of each degree of freedom to the rate of energy dissipation can be
determined based on this equality. In this paper, we present a comprehensive
description on this equality, and provide a detailed derivation for various
types of models including many-body systems, Brownian motor models,
time-dependent systems, and systems with multiple heat reservoirs.Comment: 18 pages, submitted to Phys. Rev.
- …