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2008-06-12
|
Towards the description of anisotropic plasma at strong coupling
|
We initiate a study of anisotropic plasma at strong coupling using the
AdS/CFT correspondence. We construct an exact dual geometry which represents a
static uniform but anisotropic system and find, that although it is singular,
it allows for a notion of `incoming' boundary conditions. We study small
fluctuations around this background and find that the dispersion relation
depends crucially on the direction of the wave-vector relative to the shape of
the anisotropy reminiscent of similar behaviour at weak coupling. We do not
find explicit instabilities to the considered order but only a huge difference
in the damping behaviour.
|
0806.2141v2
|
2008-06-19
|
Enhancement of sudden death of entanglement for driven qubits
|
We study the recently discovered phenomena of sudden death of entanglement
for a system of two qubits, each of them independently longitudinally damped by
a reservoir and subjected to a continuous driving. We show that driving
produces, in the interaction picture, an effective bath that has elements
amounting to various extra sources of noise (transverse, thermal squeezed,
thermal longitudinal). As a result, the time of sudden death decreases due to
driving, which we verify as well by direct numerical calculation. We suggest
that this phenomenon can be studied systematically using superconducting qubits
driven by microwave fields.
|
0806.3186v1
|
2008-06-19
|
Negative dimensional approach to evaluating real integrals
|
In solving the differential equation for a non damped harmonic oscillator one
meets, after subjecting the equation to a Fourier transformation, an
integration in the complex $\omega$ plane. In most cases such an integral is
evaluated by calculating residues together with some physical input such as the
principle of causality to define which pole residues are relevant to the
physical problem. For this kind of application, Cauchy's theorem or residue
theorem can be applied to evaluate certain real integrals. Here we present an
alternative approach based on the concept of negative dimensional integration
to treat such integrals and give an specific example on how this is
accomplished.
|
0806.3216v1
|
2008-06-20
|
Rabi model beyond the rotating wave approximation: generation of photons from vacuum through decoherence
|
We study numerically the dynamics of the Rabi Hamiltonian, describing the
interaction of a single cavity mode and a two-level atom without the rotating
wave approximation, subjected to damping and dephasing reservoirs included via
usual Lindblad superoperators in the master equation. We show that the
combination of the antirotating term and the atomic dephasing leads to linear
asymptotic photons generation from vacuum. We reveal the origins of the
phenomenon and estimate its importance in realistic situations.
|
0806.3475v1
|
2008-06-24
|
A Gear-like Predictor-Corrector method for Brownian Dynamics Simulation
|
We introduce a Predictor-Corrector type method suitable for performing
many-particle Brownian Dynamics simulations. Since the method goes over to the
Gear's method for Molecular Dynamics simulation in the limit of vanishing
friction, we refer to it as a Gear-like algorithm. The algorithm has been
tested on a one-dimensional, stochastically damped harmonic oscillator model,
showing that it can cover a wide range of friction coefficients with a
high-order accuracy, excellent stability, and a very small energy drift on the
long time scales.
|
0806.3912v2
|
2008-06-25
|
Modulated Inflation (@SUSY08)
|
We consider cosmological perturbations caused by modulated inflaton velocity.
During inflation, the inflaton motion is damped and the velocity is determined
by the parameters such as couplings or masses that may depend on light
fields(moduli). The number of e-foldings is different in different patches if
there are spatial fluctuations of such parameters. Based on this simple idea,
we consider ``modulated inflation'' in which the curvature perturbation is
generated by the fluctuation of the inflaton velocity. This talk is based on
our recent papers.
|
0806.4065v1
|
2008-06-30
|
Superfluidity near phase separation in Bose-Fermi mixtures
|
We study the transition to fermion pair superfluidity in a mixture of
interacting bosonic and fermionic atoms. The fermion interaction induced by the
bosons and the dynamical screening of the condensate phonons due to fermions
are included using the nonperturbative Hamiltonian flow equations. We determine
the bosonic spectrum near the transition towards phase separation and find that
the superfluid transition temperature may be increased substantially due to
phonon damping.
|
0807.0002v2
|
2008-07-10
|
Multiplicative Noise Induces Zero Critical Frequency
|
Stochastic Bloch equations which model the fluorescence of two level
molecules and atoms, NMR experiments and Josephson junctions are investigated
to illustrate the profound effect of multiplicative noise on the critical
frequency of a dynamical system. Using exact solutions and the cumulant
expansion we find two main effects: (i) even very weak noise may double or
triple the number of critical frequencies, which is related to an instability
of the system and (ii) strong multiplicative noise may induce a non-trivial
zero critical frequency thus wiping out the over-damped phase.
|
0807.1585v1
|
2008-07-16
|
Decay of a metastable state activated by non-Gaussian noise: A critical review of the generalized Kramers problem
|
We review the problem of the noise activated escape from a metastable state
in the presence of non-Gaussian noise, and present connections between various
theoretical approaches. We also respond to criticism of our work by Tom\'a\v{s}
Novotn\'y [arXiv:0807.0387] concerning the weak damping limit. The discrepancy
between our results is linked to uncontrolled approximations made by Novotn\'y.
|
0807.2675v1
|
2008-07-18
|
Current-induced dynamics of spiral magnet
|
We study the dynamics of the spiral magnet under the charge current by
solving the Landau-Lifshitz-Gilbert equation numerically. In the steady state,
the current ${\vec j}$ induces (i) the parallel shift of the spiral pattern
with velocity $v=(\beta/\alpha)j$ ($\alpha$, $\beta$: the Gilbert damping
coefficients), (ii) the uniform magnetization $M$ parallel or anti-parallel to
the current depending on the chirality of the spiral and the ratio $\beta /
\alpha $, and (iii) the change in the wavenumber $k$ of the spiral. These are
analyzed by the continuum effective theory using the scaling argument, and the
various nonequilibrium phenomena such as the chaotic behavior and
current-induced annealing are also discussed.
|
0807.2901v1
|
2008-08-04
|
Short Pulse Dynamics in Strongly Nonlinear Dissipative Granular Chains
|
We study the energy decay properties of a pulse propagating in a strongly
nonlinear granular chain with damping proportional to the relative velocity of
the grains. We observe a wave disturbance that at low viscosities consists of
two parts exhibiting two entirely different time scales of dissipation. One
part is an attenuating solitary wave, is dominated by discreteness and
nonlinearity effects as in a dissipationless chain, and has the shorter
lifetime. The other is a purely dissipative shocklike structure with a much
longer lifetime and exists only in the presence of dissipation. The range of
viscosities and initial configurations that lead to this complex wave
disturbance are explored.
|
0808.0527v1
|
2008-08-11
|
Persistence of zero modes in a gauged Dirac model for bilayer graphene
|
A recently constructed model for low lying excitations in bilayer graphene
exhibits mid-gap, zero energy modes in its Dirac-like spectrum, when a scalar
order parameter takes a vortex profile. We show that these modes persist when
the dynamics is extended by a gauge field interaction, which also renders
finite the vortex energy. The effect of the gauge field on the zero energy wave
function is to shift the phase of the (damped) oscillatory component of the
wave function in the absence of the gauge field.
|
0808.1562v1
|
2008-08-14
|
Planar Heterostructure Graphene -- Narrow-Gap Semiconductor -- Graphene
|
We investigate a planar heterostructure composed of two graphene films
separated by a narrow-gap semiconductor ribbon. We show that there is no the
Klein paradox when the Dirac points of the Brillouin zone of graphene are in a
band gap of a narrow-gap semiconductor. There is the energy range depending on
an angle of incidence, in which the above-barrier damped solution exists.
Therefore, this heterostructure is a "filter" transmitting particles in a
certain range of angles of incidence upon a potential barrier. We discuss the
possibility of an application of this heterostructure as a "switch".
|
0808.1981v2
|
2008-08-15
|
Asymptotic behavior of the mean square displacement of the Brownian parametric oscillator near the singular point
|
A parametric oscillator with damping driven by white noise is studied. The
mean square displacement (MSD) in the long-time limit is derived analytically
for the case that the static force vanishes, which was not treated in the past
work \cite{tashiro07}. The formula is asymptotic but is applicable to a general
periodic function. On the basis of this formula, some periodic functions
reducing MSD remarkably are proposed.
|
0808.2207v3
|
2008-08-29
|
Kramers Theory for Conformational Transitions of Macromolecules
|
We consider the application of Kramers theory to the microscopic calculation
of rates of conformational transitions of macromolecules. The main difficulty
in such an approach is to locate the transition state in a huge configuration
space. We present a method which identifies the transition state along the most
probable reaction pathway. It is then possible to microscopically compute the
activation energy, the damping coefficient, the eigenfrequencies at the
transition state and obtain the rate, without any a-priori choice of a reaction
coordinate. Our theoretical results are tested against the results of Molecular
Dynamics simulations for transitions in a 2-dimensional double well and for the
cis-trans isomerization of a linear molecule.
|
0809.0027v1
|
2008-09-19
|
Predicting spin of compact objects from their QPOs: A global QPO model
|
We establish a unified model to explain Quasi-Periodic-Oscillation (QPO)
observed from black hole and neutron star systems globally. This is based on
the accreting systems thought to be damped harmonic oscillators with higher
order nonlinearity. The model explains multiple properties parallelly
independent of the nature of the compact object. It describes QPOs successfully
for several compact sources. Based on it, we predict the spin frequency of the
neutron star Sco X-1 and the specific angular momentum of black holes GRO
J1655-40, GRS 1915+105.
|
0809.3336v1
|
2008-09-21
|
Stochastic Resonance in the Fermi-Pasta-Ulam Chain
|
We consider a damped $\beta$-Fermi-Pasta-Ulam chain, driven at one boundary
subjected to stochastic noise. It is shown that, for a fixed driving amplitude
and frequency, increasing the noise intensity, the system's energy resonantly
responds to the modulating frequency of the forcing signal. Multiple peaks
appear in the signal to noise ratio, signalling the phenomenon of stochastic
resonance. The presence of multiple peaks is explained by the existence of many
stable and metastable states that are found when solving this boundary value
problem for a semi-continuum approximation of the model. Stochastic resonance
is shown to be generated by transitions between these states.
|
0809.3604v1
|
2008-09-23
|
Application of the Lifshitz theory to poor conductors
|
The Lifshitz formula for the dispersive forces is generalized to the
materials, which cannot be described with the local dielectric response.
Principal nonlocality of poor conductors is related with the finite screening
length of the penetrating field and the collisional relaxation; at low
temperatures the role of collisions plays the Landau damping. The spatial
dispersion makes the theory self consistent. Our predictions are compared with
the recent experiment. It is demonstrated that at low temperatures the
Casimir-Lifshitz entropy disappears as $T$ in the case of degenerate plasma and
as $T^2$ for the nondegenerate one.
|
0809.3901v1
|
2008-09-26
|
On a possible connection between Chandler wobble and dark matter
|
Chandler wobble excitation and damping, one of the open problems in
geophysics, is treated as a consequence in part of the interaction between
Earth and a hypothetical oblate ellipsoid made of dark matter. The physical and
geometrical parameters of such an ellipsoid and the interacting torque strength
is calculated in such a way to reproduce the Chandler wobble component of the
polar motion in several epochs, available in the literature. It is also
examined the consequences upon the geomagnetic field dynamo and generation of
heat in the Earth outer core.
|
0809.4506v3
|
2008-09-26
|
The effects of twisted magnetic field on coronal loops oscillations and dissipation
|
The standing MHD modes in a zero-$\beta$ cylindrical magnetic flux tube
modelled as a straight core surrounded by a magnetically twisted annulus, both
embedded in a straight ambient external field is considered. The dispersion
relation for the fast MHD waves is derived and solved numerically to obtain the
frequencies of both the kink ($m=1$), and fluting ($m=2,3$) waves. Damping
rates due to both viscous and resistive dissipations in presence of the twisted
magnetic field is derived and solved numerically for both the kink and fluting
waves.
|
0809.4611v1
|
2008-10-01
|
Estimating Speed and Damping in the Stochastic Wave Equation
|
A parameter estimation problem is considered for a one-dimensional stochastic
wave equation driven by additive space-time Gaussian white noise.
The estimator is of spectral type and utilizes a finite number of the spatial
Fourier coefficients of the solution. The asymptotic properties of the
estimator are studied as the number of the Fourier coefficients increases,
while the observation time and the noise intensity are fixed.
|
0810.0046v1
|
2008-10-11
|
Asymptotic Behavior of Stochastic Wave Equations with Critical Exponents on R^3
|
The existence of a random attractor in H^1(R^3) \times L^2(R^3) is proved for
the damped semilinear stochastic wave equation defined on the entire space R^3.
The nonlinearity is allowed to have a cubic growth rate which is referred to as
the critical exponent. The uniform pullback estimates on the tails of solutions
for large space variables are established. The pullback asymptotic compactness
of the random dynamical system is proved by using these tail estimates and the
energy equation method.
|
0810.1988v1
|
2008-10-16
|
Liquid behavior of hot QGP in the finite temperature field theory
|
In this paper, we compare the dispersion relations of hard thermal loop and
complete one loop. It is shown that in the dynamical screening regime, the
completely one-loop calculation presents a prominent threshold frequency, below
which no pure imaginary mode survives. This phenomenon is responsible for the
oscillatory static in-medium potential and ultimately results in a damping
oscillation of the radial distribution function. We consider this typical shape
is the footprint of liquid QGP.
|
0810.2841v1
|
2008-10-22
|
Quantum Brownian motion under rapid periodic forcing
|
We study the steady state behaviour of a confined quantum Brownian particle
subjected to a space-dependent, rapidly oscillating time-periodic force. To
leading order in the period of driving, the result of the oscillating force is
an effective static potential which has a quantum dissipative contribution,
$V_{QD}$, which adds on to the classical result. This is shown using a coherent
state representation of bath oscillators. $V_{QD}$ is evaluated exactly in the
case of an Ohmic dissipation bath. It is strongest for intermediate values of
the damping, where it can have pronounced effects.
|
0810.4050v2
|
2008-10-25
|
The domain wall spin torque-meter
|
We report the direct measurement of the non-adiabatic component of the
spin-torque in domain walls. Our method is independent of both the pinning of
the domain wall in the wire as well as of the Gilbert damping parameter. We
demonstrate that the ratio between the non-adiabatic and the adiabatic
components can be as high as 1, and explain this high value by the importance
of the spin-flip rate to the non-adiabatic torque. Besides their fundamental
significance these results open the way for applications by demonstrating a
significant increase of the spin torque efficiency.
|
0810.4633v1
|
2008-10-26
|
Static potentials for quarkonia at finite temperatures
|
We review non-perturbative static potentials commonly used in potential
models for quarkonia at finite T. Potentials derived from Polyakov loop
correlators are shown to be inappropriate for this purpose. The q\bar{q} free
energy is physical but has the wrong spatial decay and perturbative limit. The
so-called singlet free energy is gauge dependent and unphysical. An appropriate
static real time potential can be defined through a generalisation of pNRQCD to
finite T. In perturbation theory, its real part reproduces the Debye-screened
potential, its imaginary part accounts for Landau damping. Possibilities for
its non-perturbative evaluation are discussed.
|
0810.4685v1
|
2008-10-30
|
Weakly Turbulent MHD Waves in Compressible Low-Beta Plasmas
|
In this Letter, weak turbulence theory is used to investigate interactions
among Alfven waves and fast and slow magnetosonic waves in collisionless
low-beta plasmas. The wave kinetic equations are derived from the equations of
magnetohydrodynamics, and extra terms are then added to model collisionless
damping. These equations are used to provide a quantitative description of a
variety of nonlinear processes, including "parallel" and "perpendicular" energy
cascade, energy transfer between wave types, "phase mixing," and the generation
of back-scattered Alfven waves.
|
0810.5360v1
|
2008-11-04
|
Amplitude-Phase Coupling in a Spin-Torque Nano-Oscillator
|
The spin-torque nano-oscillator in the presence of thermal fluctuation is
described by the normal form of the Hopf bifurcation with an additive white
noise. By the application of the reduction method, the amplitude-phase coupling
factor, which has a significant effect on the power spectrum of the spin-torque
nano-oscillator, is calculated from the Landau-Lifshitz-Gilbert-Slonczewski
equation with the nonlinear Gilbert damping. The amplitude-phase coupling
factor exhibits a large variation depending on in-plane anisotropy under the
practical external fields.
|
0811.0425v1
|
2008-11-07
|
Stability of drift waves in a field reversed configuration
|
The drift waves in field-reversed configurations without a toroidal magnetic
field, therefore no shear, play an important role in plasma transport. The
short connection length of the poloidal field in these systems leads to
significant stabilization by influencing the wave particle resonance. The field
reversed configuration is modeled by the cylindrical Bennett pinch in the limit
of large aspect ratio. The radial eigenmode equation for the universal mode is
derived from kinetic theory and the method of quadratic forms is used to study
its stability. The short connection lengths of the field lines lead to ion
Landau damping on the inside of the plasma and the stability of the mode depend
on the value of the temperature ratio Ti/Te
|
0811.1201v1
|
2008-11-11
|
Reduction and possible elimination of coating thermal noise using a rigidly controlled cavity with a QND technique
|
Thermal noise of a mirror is one of the most important issues in high
precision measurements such as gravitational-wave detection or cold damping
experiments. It has been pointed out that thermal noise of a mirror with
multi-layer coatings can be reduced by mechanical separation of the layers. In
this paper, we introduce a way to further reduce thermal noise by locking the
mechanically separated mirrors. The reduction is limited by the standard
quantum limit of control noise, but it can be overcome with a
quantum-non-demolition technique, which finally raises a possibility of
complete elimination of coating thermal noise.
|
0811.1780v1
|
2008-11-17
|
PGPE theory of finite temperature collective modes for a trapped Bose gas
|
We develop formalism based on the projected Gross Pitaevskii equation to
simulate the finite temperature collective mode experiments of Jin et al. [PRL
78, 764 (1997)]. We examine the $m=0$ and $m=2$ quadrupolar modes on the
temperature range $0.51T_c-0.83T_c$ and calculate the frequencies of, and phase
between, the condensate and noncondensate modes, and the condensate mode
damping rate. This study is the first quantitative comparison of the projected
Gross-Pitaevskii equation to experimental results in a dynamical regime.
|
0811.2635v1
|
2008-11-19
|
Excitation of spin waves on a cylindrical semiconductor heterostructure with Rashba spin-orbit interaction
|
Elementary excitations in a paramagnetic semiconductor quantum well confined
to a cylindrical surface are theoretically studied on the basis of coupled
spin-charge drift-diffusion equations. The electric-field-mediated eigenmodes
are optically excited by an oscillating interference pattern, which induces a
current in the outer circuit. For a cylinder with a given radius, sharp
resonances are predicted to occur in the steady-state current response, which
are due to weakly damped spin remagnetization waves.
|
0811.3070v1
|
2008-11-28
|
Effect of Nonlocal Spin-Transfer Torque on Current-Induced Magnetization Dynamics
|
Using the self-consistent model, we present nonlocal spin-transfer effects
caused by the feedback between inhomogeneous magnetization and spin-transfer
torque on the current-induced magnetization dynamics in nanomagnets. The
nonlocal effects can substantially improve the coherence time of precession in
nanomagnets and thus reduce the linewidth of power spectrum. This narrow
linewidth results from the nonlinear damping of spin-waves due to the nonlocal
spin torque which is inherent and thus should be considered in future
experiments.
|
0811.4649v1
|
2008-11-29
|
Plane Gravitational Radiation from Neutrinos Source with Kalb-Ramond Coupling
|
In this work, we propose a model based on a non-minimal coupling of neutrinos
to a Kalb-Ramond field. The latter is taken as a possible source for
gravitational radiation. As an immediate illustration of this system, we have
studied the case where gravitational (plane) wave solutions behave as damped
harmonic oscillators.
|
0812.0078v1
|
2008-12-03
|
Observation of ferromagnetic resonance in strontium ruthenate (SrRuO3)
|
We report the observation of ferromagnetic resonance (FMR) in SrRuO3 using
the time-resolved magneto-optical Kerr effect. The FMR oscillations in the
time-domain appear in response to a sudden, optically induced change in the
direction of easy-axis anistropy. The high FMR frequency, 250 GHz, and large
Gilbert damping parameter, alpha ~ 1, are consistent with strong spin-orbit
coupling. We find that the parameters associated with the magnetization
dynamics, including alpha, have a non-monotonic temperature dependence,
suggestive of a link to the anomalous Hall effect.
|
0812.0832v1
|
2008-12-04
|
On parton distributions in a photon gas
|
In some cases it may be useful to know parton distributions in a photon gas.
This may be relevant, e.g., for the analysis of interactions of high energy
cosmic ray particles with the cosmic microwave background radiation. The latter
can be considered as a gas of photons with an almost perfect blackbody
spectrum. An approach to finding such parton distributions is described. The
survival probability of ultra-high energy neutrinos traveling through this
radiation is calculated.
|
0812.0937v2
|
2008-12-09
|
Parameter estimation with cluster states
|
We propose a scheme for parameter estimation with cluster states. We find
that phase estimation with cluster states under a many-body Hamiltonian and
separable measurements leads to a precision at the Heisenberg limit. As noise
models we study the dephasing, depolarizing, and pure damping channels.
Decoherence reduces the sensitivity but our scheme remains superior over
several reference schemes with states such as maximally entangled states and
product states. For small cluster states and fixed evolution times it remains
at the Heisenberg limit for approximately 2 times as many qubits than
alternative schemes.
|
0812.1747v3
|
2008-12-19
|
Head-Tail Modes for Strong Space Charge
|
The head-tail modes are described for the space charge tune shift
significantly exceeding the synchrotron tune. A general equation for the modes
is derived. The spatial shapes of the modes, their frequencies, and coherent
growth rates are explored. The Landau damping rates are also found. The
suppression of the transverse mode coupling instability by the space charge is
explained.
|
0812.3914v3
|
2008-12-30
|
Bulk viscosity of strange matter and r-modes in neutron stars
|
We discuss bulk viscosity due to non-leptonic processes involving hyperons
and Bose-Einstein condensate of negatively charged kaons in neutron stars. It
is noted that the hyperon bulk viscosity coefficient is a few order of
magnitude larger than that of the case with the condensate. Further it is found
that the hyperon bulk viscosity is suppressed in a superconducting phase. The
hyperon bulk viscosity efficiently damps the r-mode instability in neutron
stars irrespective of whether a superconducting phase is present or not in
neutron star interior.
|
0812.5021v1
|
2009-01-06
|
Ionization in damped time-harmonic fields
|
We study the asymptotic behavior of the wave function in a simple one
dimensional model of ionization by pulses, in which the time-dependent
potential is of the form $V(x,t)=-2\delta(x)(1-e^{-\lambda t} \cos\omega t)$,
where $\delta$ is the Dirac distribution. We find the ionization probability in
the limit $t\to\infty$ for all $\lambda$ and $\omega$. The long pulse limit is
very singular, and, for $\omega=0$, the survival probability is $const
\lambda^{1/3}$, much larger than $O(\lambda)$, the one in the abrupt transition
counterpart, $V(x,t)=\delta(x)\mathbf{1}_{\{t\ge 1/\lambda\}}$ where
$\mathbf{1}$ is the Heaviside function.
|
0901.0724v1
|
2009-01-09
|
Stability of the Second Order Delay Differential Equations with a Damping Term
|
For the delay differential equations $$ \ddot{x}(t)
+a(t)\dot{x}(g(t))+b(t)x(h(t))=0, g(t)\leq t, h(t)\leq t, $$ and $$ \ddot{x}(t)
+a(t)\dot{x}(t)+b(t)x(t)+a_1(t)\dot{x}(g(t))+b_1(t)x(h(t))=0 $$ explicit
exponential stability conditions are obtained.
|
0901.1277v1
|
2009-01-20
|
Multiple regimes of diffusion
|
We consider the diffusion of independent particles experiencing random
accelerations by a space- and time-dependent force as well as viscous damping.
This model can exhibit several asymptotic behaviours, depending upon the
limiting cases which are considered, some of which have been discussed in
earlier work. Here we explore the full space of dimensionless parameters, and
introduce an "asymptotic phase diagram" which delineates the limiting regimes.
|
0901.3077v1
|
2009-01-22
|
Magnetic Field Induced Superconductivity in Out-of-Equilibrium Nanowires
|
Four-terminal resistance measurements have been carried out on Zn nanowires
formed using electron-beam lithography. When driven resistive by current, these
wires re-enter the superconducting state upon application of small magnetic
fields. The data are qualitatively different from those of previous experiments
on superconducting nanowires, which revealed either negative magnetoresistance
near T_{c} or magnetic field enhanced critical currents. We suggest that our
observations are associated with the damping of phase slip processes by the
enhancement of dissipation by the quasiparticle conductance channel resulting
from the application of a magnetic field.
|
0901.3519v1
|
2009-01-23
|
Wave propagation through soils in centrifuge testing
|
Wave propagation phenomena in soils can be experimentally simulated using
centrifuge scale models. An original excitation device (drop-ball arrangement)
is proposed to generate short wave trains. Wave reflections on model boundaries
are taken into account and removed by homomorphic filtering. Propagation is
investigated through dispersion laws. For drop-ball experiments, spherical wave
field analysis assuming linear viscoelasticity leads to a complete analytical
description of wave propagation. Damping phenomena are examined and evaluated
using this description.
|
0901.3718v1
|
2009-01-27
|
Excitation of standing kink oscillations in coronal loops
|
In this work we review the efforts that have been done to study the
excitation of the standing fast kink body mode in coronal loops. We mainly
focus on the time-dependent problem, which is appropriate to describe flare or
CME induced kink oscillations. The analytical and numerical studies in slab and
cylindrical loop geometries are reviewed. We discuss the results from very
simple one-dimensional models to more realistic (but still simple) loop
configurations. We emphasise how the results of the initial value problem
complement the eigenmode calculations. The possible damping mechanisms of the
kink oscillations are also discussed.
|
0901.4233v1
|
2009-02-09
|
Seismic Crystals And Earthquake Shield Application
|
We theoretically demonstrate that earthquake shield made of seismic crystal
can damp down surface waves, which are the most destructive type for
constructions. In the paper, seismic crystal is introduced in aspect of band
gaps (Stop band) and some design concepts for earthquake and tsunami shielding
were discussed in theoretical manner. We observed in our FDTD based 2D elastic
wave simulations that proposed earthquake shield could provide about 0.5
reductions in magnitude of surface wave on the Richter scale. This reduction
rate in magnitude can considerably reduce destructions in the case of
earthquake.
|
0902.1429v4
|
2009-02-11
|
Quantum fluctuation theorems in the strong damping limit
|
We consider a driven quantum particle in the strong friction regime described
by the quantum Smoluchowski equation. We derive Crooks and Jarzynski type
relations for the reduced quantum system by properly generalizing the entropy
production to take into account the non-Gibbsian character of the equilibrium
distribution. In the case of a nonequilibrium steady state, we obtain a quantum
version of the Hatano-Sasa relation. We, further, propose an experiment with
driven Josephson junctions that would allow to investigate nonequilibrium
entropy fluctuations in overdamped quantum systems.
|
0902.1858v2
|
2009-02-13
|
Continuous decoupling and freeze-out
|
The decoupling and freeze-out of energetic nuclear collisions is analysed in
terms of transparent semi-classical decoupling formulae. They provide a smooth
transition and generalise frequently employed instantaneous freeze-out
procedures. Simple relations between the damping width and the duration of the
decoupling process are presented and the implications on various physical
phenomena arising from the expansion and decay dynamics of the highly
compressed hadronic matter generated in high energy nuclear collisions are
discussed.
|
0902.2373v1
|
2009-02-22
|
Noise and dissipation in magnetoelectronic nanostructures
|
We study the coupled current and magnetization noise in magnetic
nanostructures by magnetoelectronic circuit theory. Spin current fluctuations,
which depend on the magnetic configuration, are found to be an important source
of magnetization noise and damping in thinly layered systems. The enhanced
magnetization fluctuations in spin valves can be directly measured by their
effect on the resistance noise.
|
0902.3779v1
|
2009-02-26
|
Formation of Cooper pairs in quantum oscillations of electrons in plasma
|
We study low energy quantum oscillations of electron gas in plasma. It is
shown that two electrons participating in these oscillations acquire additional
negative energy when they interact by means of a virtual plasmon. The
additional energy leads to the formation a Cooper pair and possible existence
of the superconducting phase in the system. We suggest that this mechanism
supports slowly damping oscillations of electrons without any energy supply.
Basing on our model we put forward the hypothesis the superconductivity can
occur in a low energy ball lightning.
|
0902.4596v1
|
2009-03-02
|
Gravitational Wave Sources May Be "Further" Than We Think
|
It has been argued that the energy content in time varying spacetimes can be
obtained by using the approximate Lie symmetries of the geodesics equations in
that spacetime. When applied to cylindrical gravitational waves, it gives a
self-damping of the waves. According to this proposal the energy of the waves
go to zero asymptotically as the radial distance to the two-thirds power. If
true, this would mean that the estimates for the sensitivity of the detectors
for the various sources would have to be revised
|
0903.0252v3
|
2009-03-07
|
Impurity effects in multiferroic compounds
|
We investigate the effect of impurities in multiferroic materials using an
equation of motion approach for the spin dynamics of the host multiferroic
compound. We model the impurities as a two-level system and focus on the regime
where the impurity spins relax slowly. When the impurity strength is weak the
host spins oscillate with no decay and the electric polarization is not
affected. However as the impurity strength is increased the host spin
components get damped and the electrion polarization is suppressed. Since
polarization in multiferroic materials is driven by magnetic ordering we
conclude that the presence of impurities is detrimental to multiferroicity.
|
0903.1319v1
|
2009-03-12
|
Quantum Noise Interference and Back-action Cooling in Cavity Nanomechanics
|
We present a theoretical analysis of a novel cavity electromechanical system
where a mechanical resonator directly modulates the damping rate kappa of a
driven electromagnetic cavity. We show that via a destructive interference of
quantum noise, the driven cavity can effectively act like a zero-temperature
bath irrespective of the ratio kappa / omega_M, where omega_M is the mechanical
frequency. This scheme thus allows one to cool the mechanical resonator to its
ground state without requiring the cavity to be in the so-called `good cavity'
limit kappa << omega_M.
|
0903.2242v2
|
2009-03-19
|
Comment on "Non-monotonicity in the Quantum-Classical Transition: Chaos Induced by Quantum Effects"
|
In a recent Letter [PRL 101, 074101 (2008)], Kapulkin and Pattanayak
presented evidence that a quantum Duffing oscillator, sufficiently damped so
that it is not classically chaotic, becomes chaotic in the transition region
between quantum and classical motion. If true, this would be a striking result.
However, Kapulkin and Pattanayak did not calculate the Lyapunov exponent for
the system, usually regarded as the litmus-test of chaos. Here we perform this
calculation, which throws considerable doubt upon their conclusions.
|
0903.3417v1
|
2009-03-24
|
The Jeans Mechanism and Bulk-Viscosity Effects
|
In this paper we study the gravitational instability in presence of
viscosity. In particular, the standard Jeans Mechanism is analyzed taking into
account bulk-viscosity effects in the first-order Newtonian dynamics. We show
how the perturbation evolution is damped by dissipative processes and the
top-down fragmentation mechanism is suppressed for strong viscous effects. The
critical value of the Jeans Mass remains unchanged also in presence of bulk
viscosity.
|
0903.4122v3
|
2009-04-10
|
Vortex oscillations induced by a spin-polarized current in a magnetic nanopillar: Evidence for a failure of the Thiele approach
|
We investigate the vortex excitations induced by a spin-polarized current in
a magnetic nanopillar by means of micromagnetic simulations and analytical
calculations. Damped motion, stationary vortex rotation and the switching of
the vortex core are successively observed for increasing values of the current.
We demonstrate that even for small amplitude of the vortex motion, the
analytical description based the classical Thiele approach can yield
quantitatively and qualitatively unsound results. We suggest and validate a new
analytical technique based on the calculation of the energy dissipation.
|
0904.1751v1
|
2009-04-14
|
Quasiparticle tunneling: P(E) theory
|
A calculation of the energy decay rate of a Josephson qubit from
non-equilibrium quasiparticles is made using the environmental P(E) theory. For
a large-capacitance qubit, we extend the theory to include the tunneling of
quasiparticles, which has an electron- and hole-like charge components.
|
0904.2035v2
|
2009-04-16
|
Experimental synchronization of circuit oscillations induced by common telegraph noise
|
Experimental realization and quantitative investigation of
common-noise-induced synchronization of limit-cycle oscillations subject to
random telegraph signals are performed using an electronic oscillator circuit.
Based on our previous formulation [K. Nagai et al., Phys. Rev. E 71, 036217
(2005)], dynamics of the circuit is described as random-phase mappings between
two limit cycles. Lyapunov exponents characterizing the degree of
synchronization are estimated from experimentally determined phase maps and
compared with linear damping rates of phase differences measured directly.
Noisy on-off intermittency of the phase difference as predicted by the theory
is also confirmed experimentally.
|
0904.2439v1
|
2009-04-17
|
ITM Probe: analyzing information flow in protein networks
|
Summary: Founded upon diffusion with damping, ITM Probe is an application for
modeling information flow in protein interaction networks without prior
restriction to the sub-network of interest. Given a context consisting of
desired origins and destinations of information, ITM Probe returns the set of
most relevant proteins with weights and a graphical representation of the
corresponding sub-network. With a click, the user may send the resulting
protein list for enrichment analysis to facilitate hypothesis formation or
confirmation.
Availability: ITM Probe web service and documentation can be found at
www.ncbi.nlm.nih.gov/CBBresearch/qmbp/mn/itm_probe
|
0904.2770v1
|
2009-04-28
|
Dielectric function and plasmons in graphene
|
The electromagnetic response of graphene, expressed by the dielectric
function, and the spectrum of collective excitations are studied as a function
of wave vector and frequency. Our calculation is based on the full band
structure, calculated within the tight-binding approximation. As a result, we
find plasmons whose dispersion is similar to that obtained in the single-valley
approximation by Dirac fermions. In contrast to the latter, however, we find a
stronger damping of the plasmon modes due to inter-band absorption. Our
calculation also reveals effects due to deviations from the linear Dirac
spectrum as we increase the Fermi energy, indicating an anisotropic behavior
with respect to the wave vector of the external electromagnetic field.
|
0904.4378v1
|
2009-05-01
|
Asymptotic behavior of second-order dissipative evolution equations combining potential with non-potential effects
|
We study the asymptotic convergence properties, as the time variable goes to
infinity, of trajectories of second-order dissipative evolution equations
combining potential with non-potential effects. We exhibit a sharp condition,
involving the damping parameter and the cocoercive coefficient of the
non-potential operator, which guarantees convergence to equilibria of the
trajectories. Applications are given to constrained optimization, fixed point
problems, dynamical approach to Nash equilibria, and asymptotic stabilization
in the case of a continuum of equilibria.
|
0905.0092v1
|
2009-05-04
|
Homopolar oscillating-disc dynamo driven by parametric resonance
|
We use a simple model of Bullard-type disc dynamo, in which the disc rotation
rate is subject to harmonic oscillations, to analyze the generation of magnetic
field by the parametric resonance mechanism. The problem is governed by a
damped Mathieu equation. The Floquet exponents, which define the magnetic field
growth rates, are calculated depending on the amplitude and frequency of the
oscillations. Firstly, we show that the dynamo can be excited at significantly
subcritical disc rotation rates when the latter is subject to harmonic
oscillations with a certain frequency. Secondly, at supercritical mean rotation
rates, the dynamo can also be suppressed but only in narrow frequency bands and
at sufficiently large oscillation amplitudes.
|
0905.0400v1
|
2009-05-06
|
Quantum adaptation of noisy channels
|
Probabilistic quantum filtering is proposed to properly adapt sequential
independent quantum channels in order to stop sudden death of entanglement. In
the adaptation, the quantum filtering does not distill or purify more
entanglement, it rather properly prepares entangled state to the subsequent
quantum channel. For example, the quantum adaptation probabilistically
eliminates the sudden death of entanglement of two-qubit entangled state with
isotropic noise injected into separate amplitude damping channels. The result
has a direct application in quantum key distribution through noisy channels.
|
0905.0862v1
|
2009-05-13
|
Observation of spin-wave propagation in permalloy microstripes
|
We report on the propagation of spin waves in permalloy microstripes. By
means of scanning Kerr microscopy combined with continuous microwave
excitation, we detect the time evolution of spin-wave interference patterns in
an external magnetic field. Assuming transverse spin-wave quantization we can
directly measure the amplitude, phase velocity and damping for the
corresponding transversal wave mode numbers m. We find that the spin-wave
interference pattern is dominated by m=0 and m=2 with phase velocities v_0=71
km/s and v_2=47 km/s, respectively.
|
0905.2172v1
|
2009-05-18
|
Global well-posedness for cubic NLS with nonlinear damping
|
We study the Cauchy problem for the cubic nonlinear Schroedinger equation,
perturbed by (higher order) dissipative nonlinearities. We prove global in-time
existence of solutions for general initial data in the energy space. In
particular we treat the energy-critical case of a quintic dissipation in three
space dimensions.
|
0905.3000v4
|
2009-05-20
|
Pumping properties of the hybrid single-electron transistor in dissipative environment
|
Pumping characteristics were studied of the hybrid
normal-metal/superconductor single-electron transistor embedded in a high-ohmic
environment. Two 3 micrometer-long microstrip resistors of CrOx with a sum
resistance R=80kOhm were placed adjacent to this hybrid device. Substantial
improvement of pumping and reduction of the subgap leakage were observed in the
low-MHz range. At higher frequencies 0.1-1GHz, a slowdown of tunneling due to
the enhanced damping and electron heating negatively affected the pumping, as
compared to the reference bare devices.
|
0905.3402v1
|
2009-05-27
|
Stability of scalar radiative shock profiles
|
This work establishes nonlinear orbital asymptotic stability of scalar
radiative shock profiles, namely, traveling wave solutions to the simplified
model system of radiating gas \cite{Hm}, consisting of a scalar conservation
law coupled with an elliptic equation for the radiation flux. The method is
based on the derivation of pointwise Green function bounds and description of
the linearized solution operator. A new feature in the present analysis is the
construction of the resolvent kernel for the case of an eigenvalue system of
equations of degenerate type. Nonlinear stability then follows in standard
fashion by linear estimates derived from these pointwise bounds, combined with
nonlinear-damping type energy estimates.
|
0905.4448v1
|
2009-05-28
|
Wigner function non-classicality as indicator of quantum chaos
|
We propose a Wigner function based parameter that can be used as an indicator
of quantum chaos. This parameter is defined as "entropy" from the
time-dependence of "non-classicallity" proposed in \cite{KZ04}. We perform our
considerations for the system of damped nonlinear (Kerr-like) oscillator
excited by a series of ultra-short external pulses.
|
0905.4638v2
|
2009-05-30
|
Solution of linearized Fokker - Planck equation for incompressible fluid
|
In this work we construct algebraic equation for elements of spectrum of
linearized Fokker - Planck differential operator for incompressible fluid. We
calculate roots of this equation using simple numeric method. For all these
roots real part is positive, that is corresponding solutions are damping.
Eigenfunctions of linearized Fokker - Planck differential operator for
incompressible fluid are expressed as linear combinations of eigenfunctions of
usual Fokker - Planck differential operator. Poisson's equation for pressure is
derived from incompressibility condition. It is stated, that the pressure could
be totally eliminated from dynamics equations. The Cauchy problem setup and
solution method is presented. The role of zero pressure solutions as
eigenfunctions for confluent eigenvalues is emphasized.
|
0906.0070v1
|
2009-06-09
|
Homogenization of accelerated Frenkel-Kontorova models with $n$ types of particles
|
We consider systems of ODEs that describe the dynamics of particles. Each
particle satisfies a Newton law (including the acceleration term) where the
force is created by the interactions with the other particles and with a
periodic potential. The presence of a damping term allows the system to be
monotone. Our study takes into account the fact that the particles can be
different. After a proper hyperbolic rescaling, we show that the solutions to
this system of ODEs converge to the solution of a macroscopic homogenized
Hamilton-Jacobi equation.
|
0906.1722v2
|
2009-06-12
|
Poor qubits make for rich physics: noise-induced quantum Zeno effects and noise-induced Berry phases
|
We briefly review three ways that environmental noise can slow-down (or
speed-up) quantum transitions; (i) Lamb shifts, (ii) over-damping and (iii)
orthogonality catastrophe. We compare them with the quantum Zeno effect induced
by observing the system. These effects are relevant to poor qubits (those
strongly coupled to noise). We discuss Berry phases generated by the
orthogonality catastrophe, and argue that noise may make it easier to observe
Berry phases.
|
0906.2368v1
|
2009-06-19
|
Investigation of an alternate means of wakefield suppression in the main linacs of CLIC
|
We report on suppression of long-range wakefields in CLIC accelerating
structures. Strong detuning and moderate damping is employed. In these initial
design studies we focus on the CLIC_G structure and enforce a moderate Q of 300
and 500. We maintain a dipole bandwidth of approximately 1 GHz as specified
from breakdown constraints in a modified structure, CLIC_DDS. The circuit
model, which facilitates a rapid design of manifolds slot-coupled to the main
accelerating cells, is described.
|
0906.3591v1
|
2009-06-22
|
Thermal breakage of a discrete one-dimensional string
|
We study the thermal breakage of a discrete one-dimensional string, with open
and fixed ends, in the heavily damped regime. Basing our analysis on the
multidimensional Kramers escape theory, we are able to make analytical
predictions on the mean breakage rate, and on the breakage propensity with
respect to the breakage location on the string. We then support our predictions
with numerical simulations.
|
0906.3754v3
|
2009-06-23
|
Parameter Estimation in Diagonalizable Stochastic Hyperbolic Equations
|
A parameter estimation problem is considered for a linear stochastic
hyperbolic equation driven by additive space-time Gaussian white noise. The
damping/amplification operator is allowed to be unbounded.
The estimator is of spectral type and utilizes a finite number of the spatial
Fourier coefficients of the solution. The asymptotic properties of the
estimator are studied as the number of the Fourier coefficients increases,
while the observation time and the noise intensity are fixed.
|
0906.4353v1
|
2009-06-29
|
Semiclassical Wigner distribution for two-mode entangled state generated by an optical parametric oscillator
|
We derive the steady state solution of the Fokker-Planck equation that
describes the dynamics of the nondegenerate optical parametric oscillator in
the truncated Wigner representation of the density operator. The adiabatic
limit of strong pump damping is assumed. This phase space image provides a
clear view of the intracavity two-mode entangled state valid in all operating
regimes of the OPO. A nongaussian distribution is obtained for the above
threshold solution.
|
0906.5316v1
|
2009-07-02
|
The Jeans Instability in Presence of Viscous Effects
|
An analysis of the gravitational instability in presence of dissipative
effects is addressed. In particular, the standard Jeans Mechanism and the
generalization in treating the Universe expansion are both analyzed when bulk
viscosity affects the first-order Newtonian dynamics. As results, the
perturbation evolution is founded to be damped by dissipative processes and the
top-down mechanism of structure fragmentation is suppressed. In such a scheme,
the value of the Jeans Mass remains unchanged also in presence of viscosity.
|
0907.0434v2
|
2009-07-05
|
Stabilities for Euler-Poisson Equations in Some Special Dimensions
|
We study the stabilities and classical solutions of Euler-Poisson equations
of describing the evolution of the gaseous star in astrophysics. In fact, we
extend the study the stabilities of Euler-Poisson equations with or without
frictional damping term to some special dimensional spaces. Besides, by using
the second inertia function in 2 dimension of Euler-Poisson equations, we prove
the non-global existence of classical solutions with $2\int_{\Omega}(\rho| u|
^{2}+2P)dx<gM^{2}-\epsilon$, for any $\gamma$.
|
0907.0873v1
|
2009-07-10
|
Fractional Equations of Curie-von Schweidler and Gauss Laws
|
The dielectric susceptibility of most materials follows a fractional
power-law frequency dependence that is called the "universal" response. We
prove that in the time domain this dependence gives differential equations with
derivatives and integrals of noninteger order. We obtain equations that
describe "universal" Curie-von Schweidler and Gauss laws for such dielectric
materials. These laws are presented by fractional differential equations such
that the electromagnetic fields in the materials demonstrate "universal"
fractional damping. The suggested fractional equations are common (universal)
to a wide class of materials, regardless of the type of physical structure,
chemical composition or of the nature of the polarization.
|
0907.1837v1
|
2009-07-13
|
Universal Electromagnetic Waves in Dielectric
|
The dielectric susceptibility of a wide class of dielectric materials
follows, over extended frequency ranges, a fractional power-law frequency
dependence that is called the "universal" response. The electromagnetic fields
in such dielectric media are described by fractional differential equations
with time derivatives of non-integer order. An exact solution of the fractional
equations for a magnetic field is derived. The electromagnetic fields in the
dielectric materials demonstrate fractional damping. The typical features of
"universal" electromagnetic waves in dielectric are common to a wide class of
materials, regardless of the type of physical structure, chemical composition,
or of the nature of the polarizing species, whether dipoles, electrons or ions.
|
0907.2163v1
|
2009-07-21
|
Wobbling kinks in $φ^4$ theory
|
We present a uniform asymptotic expansion of the wobbling kink to any order
in the amplitude of the wobbling mode. The long-range behaviour of the
radiation is described by matching the asymptotic expansions in the far field
and near the core of the kink. The complex amplitude of the wobbling mode is
shown to obey a simple ordinary differential equation with nonlinear damping.
We confirm the $t^{-1/2}$-decay law for the amplitude which was previously
obtained on the basis of energy considerations.
|
0907.3611v1
|
2009-07-31
|
New Correlated Model of Colossal Magnetoresistive Manganese Oxides
|
A new minimal model is constructed for the doped manganese oxides which
exhibit colossal magnetoresistance (CMR), involving broad spin-majority
conduction band as well as nearly localised spin-minority electron states. A
simple mean field analysis yields a temperature-dependent hybridised band
structure with suppressed carrier weight at the Fermi level. Spin stiffness is
complex, indicating unusually strong spin wave damping. Experimental and
theoretical investigations are needed to further verify the relevance of the
proposed model.
|
0907.5512v3
|
2009-08-11
|
Effect of bath temperature on the quantum decoherence
|
The dynamics of a qubit in two different environments are investigated
theoretically. The first environment is a two level system coupled to a bosonic
bath. And the second one is a damped harmonic oscillator. Based on a unitary
transformation, we find that the decoherence of the qubit can be reduced with
increasing temperature $T$ in the first case, which agree with the results in
[Phys. Rev. Lett. 100, 120401], whereas, it can not be reduced with $T$ in the
second case. In both cases, the qubit dynamics are changed substantially as the
coupling increases or finite detuning appears.
|
0908.1454v2
|
2009-08-15
|
Numerical study on diverging probability density function of flat-top solitons in an extended Korteweg-de Vries equation
|
We consider an extended Korteweg-de Vries (eKdV) equation, the usual
Korteweg-de Vries equation with inclusion of an additional cubic nonlinearity.
We investigate the statistical behaviour of flat-top solitary waves described
by an eKdV equation in the presence of weak dissipative disorder in the linear
growth/damping term. With the weak disorder in the system, the amplitude of
solitary wave randomly fluctuates during evolution. We demonstrate numerically
that the probability density function of a solitary wave parameter $\kappa$
which characterizes the soliton amplitude exhibits loglognormal divergence near
the maximum possible $\kappa$ value.
|
0908.2152v1
|
2009-09-01
|
Polariton-mediated Raman scattering in microcavities: A Green's function approach
|
We present calculations of the intensity of polariton-mediated inelastic
light scattering in semiconductor microcavities within a Green's function
framework. In addition to reproducing the strong coupling of light and matter,
this method also enables the inclusion of damping mechanisms in a consistent
way. Our results show excellent agreement with recent Raman scattering
experiments.
|
0909.0296v1
|
2009-09-02
|
Numerical modelling of convection-diffusion-reaction problems with free boundary in 1D
|
We discuss a numerical method for convection-diffusion-reaction problems with
a free boundary in 1D. The method is based on the numerical modelling of the
interface evolution, the transformation to a fixed domain problem and the
approximation by an ODE system. The interface evolution is modelled by means of
the local shape of the corresponding travelling wave solution. The method can
be applied to many free boundary problems with a finite speed of the interface.
The presented method can also approximate some problems with an infinite speed
of the interface for damped travelling wave type solutions. In the numerical
experiments we compare our numerical solution with the analytical ones for some
problems.
|
0909.0363v1
|
2009-09-02
|
Quantum Zeno and anti-Zeno effect in atom-atom entanglement induced by non-Markovian environment
|
The dynamic behavior of the entanglement for two two-level atoms coupled to a
common lossy cavity is studied. We find that the speed of disentanglement is a
decreasing (increasing) function of the damping rate of the cavity for on/near
(far-off) resonant couplings. The quantitative explanations for these phenomena
are given, and further, it is shown that they are related to the quantum Zeno
and anti-Zeno effect induced by the non-Markovian environment.
|
0909.0375v1
|
2009-10-07
|
Cavity cooling of an optically trapped nanoparticle
|
We study the cooling of a dielectric nanoscale particle trapped in an optical
cavity. We derive the frictional force for motion in the cavity field, and show
that the cooling rate is proportional to the square of oscillation amplitude
and frequency. Both the radial and axial centre-of-mass motion of the trapped
particle, which are coupled by the cavity field, are cooled. This motion is
analogous to two coupled but damped pendulums. Our simulations show that the
nanosphere can be cooled to 1/e of its initial momentum over time scales of
hundredths of milliseconds.
|
0910.1221v1
|
2009-10-19
|
Valley symmetry breaking in bilayer graphene: a test to the minimal model
|
Physical properties reflecting valley asymmetry of Landau levels in a biased
bilayer graphene under magnetic field are discussed. Within the $4-$band
continuum model with Hartree-corrected self-consistent gap and finite damping
factor we predict the appearance of anomalous steps in quantized Hall
conductivity due to the degeneracy lifting of Landau levels. Moreover, the
valley symmetry breaking effect appears as a non-semiclassical de Haas-van
Alphen effect where the reduction of the oscillation period to half cannot be
accounted for through quasi-classical quantization of the orbits in reciprocal
space, still valley degenerate.
|
0910.3469v1
|
2009-10-27
|
Quasinormal modes of Dirac field perturbation in Reissner-Nordström black hole surrounded by quintessence
|
The dirac quasinormal modes of the Reissner-Nordstr\"om black hole surrounded
by quintessence are investigated using the third WKB approximation. We find
that the magnitude of the imaginary part of the quasinormal mode frequencies
increases firstly and then decreases as the charge $Q$ increases, but it
decreases as the absolute value of $w_{q}$ increases. The magnitude of the
imaginary part of quasinormal complex frequencies is smaller than those with no
quintessence. That is to say, the dirac field damps more slowly due to the
presence of quintessence.
|
0910.5128v2
|
2009-10-28
|
DNA Breathing Dynamics in the Presence of a Terahertz Field
|
We consider the influence of a terahertz field on the breathing dynamics of
double-stranded DNA. We model the spontaneous formation of spatially localized
openings of a damped and driven DNA chain, and find that linear instabilities
lead to dynamic dimerization, while true local strand separations require a
threshold amplitude mechanism. Based on our results we argue that a specific
terahertz radiation exposure may significantly affect the natural dynamics of
DNA, and thereby influence intricate molecular processes involved in gene
expression and DNA replication.
|
0910.5294v1
|
2009-10-28
|
Interacting spin waves in the ferromagnetic Kondo lattice model
|
We present an new approach for the ferromagnetic, three-dimensional,
translational-symmetric Kondo lattice model which allows us to derive both
magnon energies and linewidths (lifetimes) and to study the properties of the
ferromagnetic phase at finite temperatures. Both "anomalous softening" and
"anomalous damping" are obtained and discussed. Our method consists of mapping
the Kondo lattice model onto an effective Heisenberg model by means of the
"modified RKKY interaction" and the "interpolating self-energy approach". The
Heisenberg model is approximatively solved by applying the Dyson-Maleev
transformation and using the "spectral density approach" with a broadened
magnon spectral density.
|
0910.5478v2
|
2009-11-23
|
Constraints on neutrino -- dark matter interactions from cosmic microwave background and large scale structure data
|
We update a previous investigation of cosmological effects of a non-standard
interaction between neutrinos and dark matter. Parameterizing the
elastic-scattering cross section between the two species as a function of the
temperature of the universe, the resulting neutrino-dark matter fluid has a
non-zero pressure, which determines diffusion-damped oscillations in the matter
power spectrum similar to the acoustic oscillations generated by the
photon-baryon fluid. Using cosmic microwave background data in combination with
large scale structure experiment results, we then put constraints on the
fraction of the interacting dark matter component as well as on the
corresponding opacity.
|
0911.4411v1
|
2009-11-25
|
Phase-Mixing and Dissipation of Standing Shear Alfven waves
|
We study the phase mixing and dissipation of a packet of standing shear
Alfv\'en waves localized in a region with non-uniform Alfv\'en background
velocity. We investigate the validity of the exponential damping law in time,
$\exp(-At^3)$, presented by Heyvaerts & Priest (1983) for different ranges of
Lundquist, $S$, and Reynolds, $R$, numbers. Our numerical results shows that it
is valid for $(R,S)\geq 10^7$.
|
0911.4901v1
|
2009-12-10
|
On Schroedinger Equation with Time-Dependent Quadratic Hamiltonian in $R^d$
|
We study solutions to the Cauchy problem for the linear and nonlinear
Schroedinger equation with a quadratic Hamiltonian depending on time. For the
linear case the evolution operator can be expressed as an integral operator
with the explicit formula for the kernel. As a consequence, conditions for
local and global in time Strichartz estimates can be established. For the
nonlinear case we show local well-posedness. As a particular case we obtain
well-posedness for the damped harmonic nonlinear Schroedinger equation.
|
0912.2113v3
|
2009-12-18
|
Polariton crystallization in driven arrays of lossy nonlinear resonators
|
We investigate the steady states of a lossy array of nonlinear optical
resonators that are driven by lasers and interact via mutual photon tunneling.
For weak nonlinearities, we find two-mode squeezing of polaritons in modes
whose quasi-momenta match the relative phases of the laser drives. For strong
nonlinearities the spatial polariton density-density correlations indicate that
the polaritons crystallize and are predominantly found at a specific distance
from each other despite being injected by a coherent light source and damped by
the environment.
|
0912.3612v2
|
2009-12-18
|
Anomalous Light Absorption by Small Particles
|
A new type of resonant light absorption by a small particle (nanocluster) is
reported. The problem cannot be described within the commonly used dipole
scattering approximation and should be studied with methods based upon the
exact Mie solution. It is shown that the absorption cross-section has giant
maxima realized at small values of the imaginary part of the complex dielectric
permittivity of the particle. The maxima are situated in the vicinity of the
plasmon (polariton) resonances and correspond to the regions where the
dissipative damping equals the radiative one. The case is similar to the
recently introduced anomalous scattering [PRL vol. 97, 263902 (2006)] and
exhibits similar peculiarities.
|
0912.3644v1
|
2009-12-20
|
Unconventional state with two coexisting long-range orders for frustrated Heisenberg model at quantum phase transition
|
For the frustrated two-dimensional $S=1/2$ antiferromagnetic Heisenberg model
close to quantum phase transition we consider the singlet ground states
retaining both translational and SU(2) symmetry. Besides usually discussed
checkerboard, spin-liquid and stripe states an unconventional state with two
coexisting long-range orders appears to be possible at sufficiently large
damping of spin excitations. The problem is treated in the frames of
self-consistent spherically symmetric approach.
|
0912.4008v1
|
2009-12-22
|
Interference of magnetointersubband and phonon-induced resistance oscillations in single GaAs quantum wells with two populated subbands
|
Low-temperature electron magnetotransport in single GaAs quantum wells with
two populated subbands is studied at large filling factors.
Magneto-inter-subband (MIS) and acoustic-phonon induced oscillations of the
dissipative resistance are found to be coexisting but interfering substantially
with each other. The experiments show that amplitude of the MIS-oscillations
enhances significantly by phonons, indicating "constructive interference"
between the phonon scattering and the intersubband electron transitions.
Temperature damping of the quantum oscillations is found to be related to
broadening of Landau levels caused by considerable electron-electron
scattering.
|
0912.4366v1
|
2009-12-22
|
Collective oscillations in ultracold atomic gases
|
Using both fluid and kinetic descriptions, where repulsive forces between
near by atoms are included, we discuss the basic oscillations and waves of a
cloud of ultra-cold atoms confined in a magneto-optical trap. The existence of
a hybrid mode, with properties similar to both plasma and acoustic waves is
described in detail. Tonks-Dattner resonances for confined hybrid modes in a
spherical cloud are discussed and the prediction of a nonlinear coupling
between the dipole resonanc and the hybrid modes is considered. Landau damping
processes and quasi-linear diffusion in velocity space are also discussed.
|
0912.4420v1
|
2009-12-23
|
Solar-type Variables
|
The rich acoustic oscillation spectrum in solar-type variables make these
stars particularly interesting for studying fluid-dynamical aspects of the
stellar interior. I present a summary of the properties of solar-like
oscillations, how they are excited and damped and discuss some of the recent
progress in using asteroseismic diagnostic techniques for analysing low-degree
acoustic modes. Also the effects of stellar-cycle variations in low-mass
main-sequence stars are addressed.
|
0912.4622v2
|
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