publicationDate
stringlengths 1
2.79k
| title
stringlengths 1
36.5k
⌀ | abstract
stringlengths 1
37.3k
⌀ | id
stringlengths 9
47
|
|---|---|---|---|
2011-09-14
|
On the approximation for singularly perturbed stochastic wave equations
|
We explore the relation between fast waves, damping and imposed noise for
different scalings by considering the singularly perturbed stochastic nonlinear
wave equations
\nu u_{tt}+u_t=\D u+f(u)+\nu^\alpha\dot{W} on a bounded spatial domain. An
asymptotic approximation to the stochastic wave equation is constructed by a
special transformation and splitting of $\nu u_{t}$. This splitting gives a
clear description of the structure of $u$. The approximating model, for small
$\nu>0$\,, is a stochastic nonlinear heat equation for exponent
$0\leq\alpha<1$\,, and is a deterministic nonlinear wave equation for exponent
$\alpha>1$\,.
|
1109.3000v1
|
2011-09-19
|
Quasinormal resonances of a massive scalar field in a near-extremal Kerr black hole spacetime
|
The fundamental resonances of near-extremal Kerr black holes due to massive
scalar perturbations are derived {\it analytically}. We show that there exists
a critical mass parameter, $\mu_c$, below which increasing the mass $\mu$ of
the field increases the oscillation frequency $\Re(\omega)$ of the resonance.
On the other hand, above the critical field mass increasing the mass $\mu$
increases the damping rate $\Im(\omega)$ of the mode. We confirm our analytical
results by numerical computations.
|
1109.4080v1
|
2011-09-26
|
Gauge-flation and Cosmic No-Hair Conjecture
|
Gauge-flation, inflation from non-Abelian gauge fields, was introduced in
[1,2]. In this work, we study the cosmic no-hair conjecture in gauge-flation.
Starting from Bianchi-type I cosmology and through analytic and numeric studies
we demonstrate that the isotropic FLRW inflation is an attractor of the
dynamics of the theory and that the anisotropies are damped within a few
e-folds, in accord with the cosmic no-hair conjecture.
|
1109.5573v2
|
2011-09-26
|
A possible statistical mechanism of anomalous neutrino velocity in OPERA experiment?
|
The set of kinetic equations describing the process of conversion of a beam
of protons into mesons and then to neutrinos is solved. The asymptotic
evolution of the density profile of neutrinos is essentially the same as that
obtained in the previous version of the note for a simple model of uniformly
damped wave-packet. It shows again that the recently reported "superluminal
neutrinos" could be considered as a purely statistical effect due to the fact
that the detected neutrinos represent a biased sample of initial protons.
|
1109.5727v2
|
2011-09-28
|
Local solvability and loss of smoothness of the Navier-Stokes-Maxwell equations with large initial data
|
Existence of local-in-time unique solution and loss of smoothness of full
Magnet-Hydro-Dynamics system (MHD) is considered for periodic initial data. The
result is proven using Fujita-Kato's method in $\ell^1$ based (for the Fourier
coefficients) functional spaces enabling us to easily estimate nonlinear terms
in the system as well as solutions to Maxwells's equations. A loss of
smoothness result is shown for the velocity and magnetic field. It comes from
the damped-wave operator which does not have any smoothing effect.
|
1109.6089v1
|
2011-10-02
|
On exponential decay rate of semigroup associated with second order linear differential equation in Hilbert space with strong damping operator
|
We obtain estimate of the exponential decay rate of semigroup associated with
second order linear differential equation $u"+Du'+Au=0$ in Hilbert space. We
assume that $A$ is a selfadjoint positive definite operator, $D$ is an
accretive sectorial operator and $\Ree D\geq\delta A$, $\delta>0$. We obtain a
location of the spectrum of a pencil associated with linear differential
equation.
|
1110.0167v1
|
2011-10-11
|
Parabolic inverse convection-diffusion-reaction problem solved using an adaptive parametrization
|
This paper investigates the solution of a parabolic inverse problem based
upon the convection-diffusion-reaction equation, which can be used to estimate
both water and air pollution. We will consider both known and unknown source
location: while in the first case the problem is solved using a projected
damped Gauss-Newton, in the second one it is ill-posed and an adaptive
parametrization with time localization will be adopted to regularize it. To
solve the optimization loop a model reduction technique (Proper Orthogonal
Decomposition) is used.
|
1110.2376v1
|
2011-10-23
|
Hard x-ray or gamma ray laser by a dense electron beam
|
A coherent x-ray or gamma ray can be created from a dense electron beam
propagating through an intense laser undulator. It is analyzed by using the
Landau damping theory which suits better than the conventional linear analysis
for the free electron laser, as the electron beam energy spread is high. The
analysis suggests that the currently available physical parameters would enable
the generation of the coherent gamma ray of up to 100 keV. The electron quantum
diffraction suppresses the FEL action, by which the maximum radiation energy to
be generated is limited.
|
1110.5077v2
|
2011-10-30
|
Dissipation of micro-cantilevers as a function of air pressure and metallic coating
|
In this letter, we characterize the internal dissipation of coated
micro-cantilevers through their mechanical thermal noise. Using a home-made
interferometric setup, we achieve a resolution down to 1E-14m/rtHz in the
measurement of their deflection. With the use of the fluctuation dissipation
theorem and of the Kramers-Kronig relations, we rebuilt the full mechanical
response function from the measured noise spectrum, and investigate frequency
dependent dissipation as a function of the air pressure and of the nature of
the metallic coatings. Using different thicknesses of gold coatings, we discuss
the source of the internal viscoelastic damping.
|
1110.6629v1
|
2011-11-02
|
Bucket Shaking Stops Bunch Oscillations In The Tevatron
|
Bunches in the Tevatron are known to exhibit longitudinal oscillations which
persist indefinitely. These oscillations are colloquially called "dancing
bunches". Although the dancing bunches do not cause single bunch emittance
growth or beam loss at injection, it leads to bunch lengthening at collisions.
In operations, a longitudinal damper has been built which stops this dance and
damps out coupled bunch modes. Recent theoretical work predicts that the dance
can also be stopped by an appropriate change in the bunch distribution. This
paper shows the Tevatron experiments which support this theory.
|
1111.0612v1
|
2011-11-10
|
Exponential suppression of interlayer conductivity in very anisotropic quasi-two-dimensional compounds in high magnetic field
|
It is shown that in rather strong magnetic field the interlayer electron
conductivity is exponentially damped by the Coulomb barrier arising from the
formation of polaron around each localized electron state. The theoretical
model is developed to describe this effect, and the calculation of the
temperature and field dependence of interlayer magnetoresistance is performed.
The results obtained agree well with the experimental data in GaAs/AlGaAs
heterostructures and in strongly anisotropic organic metals. The proposed
theory allows to use the experiments on interlayer magnetoresistance to
investigate the electron states, localized by magnetic field and disorder.
|
1111.2432v1
|
2011-11-13
|
Fractional oscillator
|
We consider the fractional oscillator being a generalization of the
conventional linear oscillator in the framework of fractional calculus. It is
interpreted as an ensemble average of ordinary harmonic oscillators governed by
stochastic time arrow. The intrinsic absorption of the fractional oscillator
results from the full contribution of the harmonic oscillators' ensemble: these
oscillators differs a little from each other in frequency so that each response
is compensated by an antiphase response of another harmonic oscillator. This
allows to draw a parallel in the dispersion analysis for the media described by
the fractional oscillator and the ensemble of ordinary harmonic oscillators
with damping. The features of this analysis are discussed.
|
1111.3060v1
|
2011-11-25
|
Teleporting the one-qubit state via two-level atoms with spontaneous emission
|
We study quantum teleportation via two two-level atoms coupled collectively
to a multimode vacuum field and prepared initially in different atomic states.
We concentrated on influence of the spontaneous emission, collective damping
and dipole-dipole interaction of the atoms on fidelity dynamics of quantum
teleportation and obtained the region of spatial distance between the two atoms
over which the state can be teleported nonclassically. Moreover, we showed
through concrete examples that entanglement of the channel state is the
prerequisite but not the only essential quantity for predicting the
teleportation fidelity.
|
1111.5964v1
|
2011-12-02
|
An application of nonlinear supratransmission to the propagation of binary signals in weakly damped, mechanical systems of coupled oscillators
|
In the present article, we simulate the propagation of binary signals in
semi-infinite, mechanical chains of coupled oscillators harmonically driven at
the end, by making use of the recently discovered process of nonlinear
supratransmission. Our numerical results ---which are based on a brand-new
computational technique with energy-invariant properties--- show an efficient
and reliable transmission of information.
|
1112.0583v1
|
2011-12-06
|
Fragmentation of electric dipole strength in N=82 isotones
|
Fragmentation of the dipole strength in the N=82 isotones 140Ce, 142Nd and
144Sm is calculated using the second random-phase approximation (SRPA). In
comparison with the result of the random-phase approximation (RPA), the SRPA
provides the additional damping of the giant dipole resonance and the
redistribution of the low-energy dipole strength. Properties of the low-energy
dipole states are significantly changed by the coupling to
two-particle-two-hole (2p2h) states, which are also sensitive to the
correlation among the 2p2h states. Comparison with available experimental data
shows a reasonable agreement for the low-energy E1 strength distribution.
|
1112.1231v1
|
2011-12-06
|
Generalized hidden Kerr/CFT
|
We construct a family of vector fields that generate local symmetries in the
solution space of low frequency massless field perturbations in the general
Kerr geometry. This yields a one-parameter family of SL(2,R)x SL(2,R) algebras.
We identify limits in which the SL(2,R)xSL(2,R) algebra contracts to an SL(2,R)
symmetry of the Schwarzschild background. We note that for a particular value
of our new free parameter, the symmetry algebra generates the quasinormal mode
spectrum of a Kerr black hole in the large damping limit, suggesting a
connection between the hidden conformal symmetry and a fundamental CFT
underlying the quantum Kerr black hole.
|
1112.1431v2
|
2011-12-11
|
Shear viscosity and spin diffusion coefficient of a two-dimensional Fermi gas
|
Using kinetic theory, we calculate the shear viscosity and the spin diffusion
coefficient as well as the associated relaxation times for a two-component
Fermi gas in two dimensions, as a function of temperature, coupling strength,
polarization, and mass ratio of the two components. It is demonstrated that the
minimum value of the viscosity decreases with the mass ratio, since Fermi
blocking becomes less efficient. We furthermore analyze recent experimental
results for the quadrupole mode of a 2D gas in terms of viscous damping
obtaining a qualitative agreement using no fitting parameters.
|
1112.2395v2
|
2011-12-12
|
On the vanishing electron-mass limit in plasma hydrodynamics in unbounded media
|
We consider the zero-electron-mass limit for the Navier-Stokes-Poisson system
in unbounded spatial domains. Assuming smallness of the viscosity coefficient
and ill-prepared initial data, we show that the asymptotic limit is represented
by the incompressible Navier-Stokes system, with a Brinkman damping, in the
case when viscosity is proportional to the electron-mass, and by the
incompressible Euler system provided the viscosity is dominated by the electron
mass. The proof is based on the RAGE theorem and dispersive estimates for
acoustic waves, and on the concept of suitable weak solutions for the
compressible Navier-Stokes system.
|
1112.2562v1
|
2011-12-14
|
Quenched Slonczewski-Windmill in Spin-Torque Vortex-Oscillators
|
We present a combined analytical and numerical study on double-vortex
spin-torque nano-oscillators and describe a mechanism that suppresses the
windmill modes. The magnetization dynamics is dominated by the gyrotropic
precession of the vortex in one of the ferromagnetic layers. In the other layer
the vortex gyration is strongly damped. The dominating layer for the
magnetization dynamics is determined by the current polarity. Measurements on
Fe/Ag/Fe nano-pillars support these findings. The results open up a new
perspective for building high quality-factor spin-torque oscillators operating
at selectable, well-separated frequency bands.
|
1112.3163v1
|
2011-12-14
|
Beam cavity interaction
|
We begin by giving a description of the rf generator-cavity-beam coupled
system in terms of basic quantities. Taking beam loading and cavity detuning
into account, expressions for the cavity impedance as seen by the generator and
as seen by the beam are derived. Subsequently methods of beam-loading
compensation by cavity detuning, rf feedback, and feed-forward are described.
Examples of digital rf phase and amplitude control for the special case of
superconducting cavities are also given. Finally, a dedicated phase loop for
damping synchrotron oscillations is discussed.
|
1112.3203v1
|
2011-12-17
|
Asymmetric ac fluxon depinning in a Josephson junction array: A highly discrete limit
|
Directed motion and depinning of topological solitons in a strongly discrete
damped and biharmonically ac-driven array of Josephson junctions is studied.
The mechanism of the depinning transition is investigated in detail. We show
that the depinning process takes place through chaotization of an initially
standing fluxon periodic orbit. Detailed investigation of the Floquet
multipliers of these orbits shows that depending on the depinning parameters
(either the driving amplitude or the phase shift between harmonics) the
chaotization process can take place either along the period-doubling scenario
or due to the type-I intermittency.
|
1112.4083v1
|
2011-12-20
|
Effects of helical magnetic fields on the cosmic microwave background
|
A complete numerical calculation of the temperature anisotropies and
polarization of the cosmic microwave background (CMB) in the presence of a
stochastic helical magnetic field is presented which includes the contributions
due to scalar, vector and tensor modes. The correlation functions of the
magnetic field contributions are calculated numerically including a Gaussian
window function to effectively cut off the magnetic field spectrum due to
damping. Apart from parity-even correlations the helical nature of the magnetic
field induces parity-odd correlations between the E- and B-mode of polarization
(EB) as well as between temperature (T) and the polarization B-mode (TB).
|
1112.4797v1
|
2011-12-23
|
Dynamical revival of phase coherence in a many-boson system
|
We study the quantum dynamics of cold Bose atoms in a double well. It is
shown that self-trapping, as well as population oscillations are common
phenomena associated to nonlinear interactions. For larger $U/t$,
multi-particle tunneling is damped and the quantum dynamics is dominated by the
single-particle tunneling. The many-body system can be effectively described in
a truncated Fock space. It exhibits coherence-decoherence oscillations in the
temporal evolution. We predict a novel phenomenon of dynamical revival and
collapse of matter wave fields in optical lattices in regimes near the
superfluid-Mott insulator phase boundary.
|
1112.5494v1
|
2012-01-15
|
Triviality of the 2D stochastic Allen-Cahn equation
|
We consider the stochastic Allen-Cahn equation driven by mollified space-time
white noise. We show that, as the mollifier is removed, the solutions converge
weakly to 0, independently of the initial condition. If the intensity of the
noise simultaneously converges to 0 at a sufficiently fast rate, then the
solutions converge to those of the deterministic equation. At the critical
rate, the limiting solution is still deterministic, but it exhibits an
additional damping term.
|
1201.3089v1
|
2012-01-24
|
Transverse modes and instabilities of a bunched beam with space charge and resistive wall impedance
|
Transverse instability of a bunched beam is investigated with synchrotron
oscillations, space charge, and resistive wall wakefield taken into account.
Boxcar model is used for all-round analysis, and Gaussian distribution is
invoked for details. The beam spectrum, instability growth rate and effects of
chromaticity are studied in a wide range of parameters, both with head-tail and
collective bunch interactions included. Effects of the internal bunch
oscillations on the of collective instabilities is investigated thoroughly.
Landau damping caused by the space charge tune spread is discussed, and the
instability thresholds of different modes of Gaussian bunch are estimated.
|
1201.5110v1
|
2012-02-03
|
Cavity Dynamical Casimir Effect in the presence of a three-level atom
|
We consider the scenario in which a damped three-level atom in the ladder or
V configurations is coupled to a single cavity mode whose vacuum state is
amplified by dint of the dynamical Casimir effect. We obtain approximate
analytical expressions and exact numerical results for the time-dependent
probabilities, demonstrating that the presence of the third level modifies the
photon statistics and its population can serve as a witness of photon
generation from vacuum.
|
1202.0772v2
|
2012-02-11
|
Statistical reliability and path diversity based PageRank algorithm improvements
|
In this paper we present new improvement ideas of the original PageRank
algorithm. The first idea is to introduce an evaluation of the statistical
reliability of the ranking score of each node based on the local graph property
and the second one is to introduce the notion of the path diversity. The path
diversity can be exploited to dynamically modify the increment value of each
node in the random surfer model or to dynamically adapt the damping factor. We
illustrate the impact of such modifications through examples and simple
simulations.
|
1202.2393v1
|
2012-02-20
|
Detectable inertial effects on Brownian transport through narrow pores
|
We investigate the transport of suspended Brownian particles dc driven along
corrugated narrow channels in a regime of finite damping. We demonstrate that
inertial corrections cannot be neglected as long as the width of the channel
bottlenecks is smaller than an appropriate particle diffusion length, which
depends on both, the temperature and the strength of the dc drive. Therefore,
transport through sufficiently narrow constrictions turns out to be sensitive
to the viscosity of the suspension fluid. Applications to colloidal systems are
discussed.
|
1202.4362v2
|
2012-02-21
|
Discrete solitons in coupled active lasing cavities
|
We examine the existence and stability of discrete spatial solitons in
coupled nonlinear lasing cavities (waveguide resonators), addressing the case
of active defocusing media, where the gain exceeds damping in the low-amplitude
limit. A new family of stable localized structures is found: these are bright
and grey cavity solitons representing the connections between homogeneous and
inhomogeneous states. Solitons of this type can be controlled by the discrete
diffraction and are stable when the bistability of homogenous states is absent.
|
1202.4660v2
|
2012-02-26
|
On the Fitzhugh-Nagumo model
|
The initial value problem P0, in all of the space, for the spatio - temporal
FitzHugh - Nagumo equations is analyzed. When the reaction kinetics of the
model can be outlined by means of piecewise linear approximations, then the
solution of P0 is explicitly obtained. For periodic initial data are possible
damped travelling waves and their speed of propagation is evaluated. The
results imply applications also to the non linear case.
|
1202.5783v1
|
2012-02-27
|
Second-order Price Dynamics: Approach to Equilibrium with Perpetual Arbitrage
|
The notion that economies should normally be in equilibrium is by now
well-established; equally well-established is that economies are almost never
precisely in equilibrium. Using a very general formulation, we show that under
dynamics that are second-order in time a price system can remain away from
equilibrium with permanent and repeating opportunities for arbitrage, even when
a damping term drives the system towards equilibrium. We also argue that
second-order dynamic equations emerge naturally when there are heterogeneous
economic actors, some behaving as active and knowledgeable arbitrageurs, and
others using heuristics. The essential mechanism is that active arbitrageurs
are able to repeatedly benefit from the suboptimal heuristics that govern most
economic behavior.
|
1202.5926v1
|
2012-03-02
|
Prospects for transient gravitational waves at r-mode frequencies associated with pulsar glitches
|
Glitches in pulsars are likely to trigger oscillation modes in the fluid
interior of neutron stars. We examined these oscillations specifically at
r-mode frequencies. The excited r-modes will emit gravitational waves and can
have long damping time scales O(minutes - days). We use simple estimates of how
much energy the glitch might put into the r-mode and assess the detectability
of the emitted gravitational waves with future interferometers.
|
1203.0401v1
|
2012-03-14
|
Probabilistic representation of fundamental solutions to $\frac{\partial u}{\partial t} = κ_m \frac{\partial^m u}{\partial x^m}$
|
For the fundamental solutions of heat-type equations of order $n$ we give a
general stochastic representation in terms of damped oscillations with
generalized gamma distributed parameters. By composing the pseudo-process $X_n$
related to the higher-order heat-type equation with positively skewed stable
r.v.'s $T^j_{1/3}$, $j=1,2, ..., n$ we obtain genuine r.v.'s whose explicit
distribution is given for $n=3$ in terms of Cauchy asymmetric laws. We also
prove that $X_3(T^1_{1/3}(...(T^n_{(1/3)}(t))...))$ has a stable asymmetric
law.
|
1203.3133v1
|
2012-03-15
|
Quantum-memory-assisted entropic uncertainty principle under noise
|
The measurement outcomes of two incompatible observables on a particle can be
precisely predicted when it is maximally entangled with a quantum memory, as
quantified recently [Nature Phys. 6, 659 (2010)]. We explore the behavior of
the uncertainty relation under the influence of local unital and nonunital
noisy channels. While the unital noises only increase the amount of
uncertainty, the amplitude-damping nonunital noises may amazingly reduce the
amount of uncertainty in the long-time limit. This counterintuitive phenomenon
could be justified by different competitive mechanisms between quantum
correlations and the minimal missing information after local measurement.
|
1203.3331v1
|
2012-03-15
|
Conditions for the freezing phenomena of geometric measure of quantum discord for arbitrary two-qubit X states under non-dissipative dephasing noises
|
We study the dynamics of geometric measure of quantum discord (GMQD) under
the influences of two local phase damping noises. Consider the two qubits
initially in arbitrary X-states, we find the necessary and sufficient
conditions for which GMQD is unaffected for a finite period. It is further
shown that such results also hold for the non-Markovian dephasing process.
|
1203.3356v2
|
2012-03-16
|
Dynamical Casimir Effect in two-atom cavity QED
|
We study analytically and numerically the dynamical Casimir effect in a
cavity containing two stationary 2-level atoms that interact with the resonance
field mode via the Tavis-Cummings Hamiltonian. We determine the modulation
frequencies for which the field and atomic excitations are generated and study
the corresponding dynamical behaviors in the absence of damping. It is shown
that the two-atom setup allows for monitoring of photon generation without
interrupting the growth, and different entangled states can be generated during
the process.
|
1203.3776v2
|
2012-03-20
|
Role of Bose Statistics in Crystallization and Quantum Jamming
|
Indistinguishability of particles is a major factor destabilizing crystalline
order in Bose systems. We describe this effect in terms of damped
quasi-particle modes and in the dual language of Feynman paths, and illustrate
it by first-principle simulations of dipolar bosons and bulk condensed
helium-four. The first major implication is that, contrary to conventional
wisdom, zero-point motion alone cannot prevent helium-four crystallization at
low temperature, at saturated vapour pressure. Secondly, Bose statistics leads
to quantum jamming at finite temperature, dramatically enhancing the
metastability of superfluid glasses. Only studies of indistinguishable
particles can reliably address these issues.
|
1203.4447v2
|
2012-03-30
|
Escape rate of an active Brownian particle over a potential barrier
|
We study the dynamics of an active Brownian particle with a nonlinear
friction function located in a spatial cubic potential. For strong but finite
damping, the escape rate of the particle over the spatial potential barrier
shows a nonmonotonic dependence on the noise intensity. We relate this behavior
to the fact that the active particle escapes from a limit cycle rather than
from a fixed point and that a certain amount of noise can stabilize the sojourn
of the particle on this limit cycle.
|
1203.6814v1
|
2012-04-05
|
Phase space reduction of the one-dimensional Fokker-Planck (Kramers) equation
|
A pointlike particle of finite mass m, moving in a one-dimensional viscous
environment and biased by a spatially dependent force, is considered. We
present a rigorous mapping of the Fokker-Planck equation, which determines
evolution of the particle density in phase space, onto the spatial coordinate
x. The result is the Smoluchowski equation, valid in the overdamped limit,
m->0, with a series of corrections expanded in powers of m. They are determined
unambiguously within the recurrence mapping procedure. The method and the
results are interpreted on the simplest model with no field and on the damped
harmonic oscillator.
|
1204.1145v1
|
2012-04-20
|
A Reanalysis of the Hydrodynamic Theory of Fluid, Polar-Ordered Flocks
|
I reanalyze the hydrodynamic theory of fluid, polar ordered flocks. I find
new linear terms in the hydrodynamic equations which slightly modify the
anisotropy, but not the scaling, of the damping of sound modes. I also find
that the nonlinearities allowed {\it in equilibrium} do not stabilize long
ranged order in spatial dimensions $d=2$; in accord with the Mermin-Wagner
theorem. Nonequilibrium nonlinearities {\it do} stabilize long ranged order in
$d=2$, as argued by earlier work. Some of these were missed by earlier work; it
is unclear whether or not they change the scaling exponents in $d=2$.
|
1204.4527v1
|
2012-04-26
|
Dynamics of a nano-scale rotor driven by single-electron tunneling
|
We investigate theoretically the dynamics and the charge transport properties
of a rod-shaped nano-scale rotor, which is driven by a similar mechanism as the
nanomechanical single-electron transistor (NEMSET). We show that a static
electric potential gradient can lead to self-excitation of oscillatory or
continuous rotational motion. The relevant parameters of the device are
identified and the dependence of the dynamics on these parameters is studied.
We further discuss how the dynamics is related to the measured current through
the device. Notably, in the oscillatory regime, we find a negative differential
conductance. The current-voltage characteristics can be used to infer details
of the surrounding environment which is responsible for damping.
|
1204.5918v1
|
2012-04-26
|
Avalanches in Strained Amorphous Solids: Does Inertia Destroy Critical Behavior?
|
Simulations are used to determine the effect of inertia on athermal shear of
a two-dimensional binary Lennard-Jones glass. In the quasistatic limit, shear
occurs through a series of rapid avalanches. The distribution of avalanches is
analyzed using finite-size scaling with thousands to millions of particles.
Inertia takes the system to a new underdamped universality class rather than
driving the system away from criticality. Scaling exponents are determined for
the underdamped and overdamped limits and a critical damping that separates the
two regimes. Systems are in the overdamped universality class even when most
vibrational modes are underdamped.
|
1204.5965v1
|
2012-04-29
|
Coherent phonon dynamics at the martensitic phase transition of Ni_2MnGa
|
We use time-resolved optical reflectivity to study the laser stimulated
dynamics in the magnetic shape memory alloy Ni_2MnGa. We observe two coherent
optical phonons, at 1.2 THz in the martensite phase and at 0.7 THz in the
pre-martensite phase, which we interpret as a zone-folded acoustic phonon and a
heavily damped amplitudon respectively. In the martensite phase the martensitic
phase transition can be induced by a fs laser pulse on a timescale of a few ps.
|
1204.6463v1
|
2012-05-01
|
Entangling homogeneously broadened matter qubits in the weak-coupling cavity-QED regime
|
In distributed quantum information processing, flying photons entangle matter
qubits confined in cavities. However, when a matter qubit is homogeneously
broadened, the strong-coupling regime of cavity QED is typically required,
which is hard to realize in actual experimental setups. Here, we show that a
high-fidelity entanglement operation is possible even in the weak-coupling
regime in which dampings (dephasing, spontaneous emission, and cavity leakage)
overwhelm the coherent coupling between a qubit and the cavity. Our proposal
enables distributed quantum information processing to be performed using much
less demanding technology than previously.
|
1205.0060v1
|
2012-05-04
|
State-independent teleportation of an atomic state between two cavities
|
A scheme is presented for the teleportation of an unknown atomic state
between two separated cavities. The scheme involves two interaction-detection
cycles and uses resonantly coupled atoms with an additional ground state not
coupled to the cavity field. Remarkably, the damping of one basis state is
balanced by that of the other basis state and the state with photon loss in the
first interaction-detection cycle is eliminated by the second cycle. Therefore,
the fidelity of teleportation is independent of the teleported state and
insensitive to the atomic spontaneous emission, cavity decay, and detection
inefficiency, which is obviously in contrast to the original scheme by Bose et
al. Phys. Rev. Lett. 83 5158 (1999).
|
1205.0981v1
|
2012-05-07
|
Spin and charge transport in material with spin-dependent conductivity
|
The spin and charge transport in materials with spin-dependent conductivity
has been studied. It was shown that there is a charge accumulation along spin
diffusion in a ferromagnetic metal, which causes a shortening of the spin
diffusion length. It was shown that there is a substantial interaction between
the drift and diffusion currents in semiconductors. The effects of gain/damping
of a spin current by a charge current and the existence of a threshold spin
current in a semiconductor were described. Because of the substantial
magnitude, these new spintronics effect might be used for new designs of
efficient spintronic devices. The influence of a spin drain on spin transport
was discussed.
|
1205.1278v1
|
2012-05-24
|
SASE FEL Storage Ring
|
We explore the possibility of operating a SASE FEL with a Storage Ring. We
use a semi-analytical model to obtain the evolution inside the undulator by
taking into account the interplay on the laser dynamics due to the induced
energy spread and to the radiation damping. We obtain the Renieri's limit for
the stationary output power and discuss the possibility of including in our
model the effect of the beam instabilities.
|
1205.5445v1
|
2012-05-27
|
Effective dynamics of stochastic wave equation with a random dynamical boundary condition
|
This work is devoted to the effective macroscopic dynamics of a weakly damped
stochastic nonlinear wave equation with a random dynamical boundary condition.
The white noises are taken into account not only in the model equation defined
on a domain perforated with small holes, but also in the dynamical boundary
condition on the boundaries of the small holes. An effective homogenized,
macroscopic model is derived in the sense of probability distribution, which is
a new stochastic wave equation on a unified domain, without small holes, with a
usual static boundary condition.
|
1205.5948v1
|
2012-05-29
|
Predecoherence: before Decoherence and Collapse
|
Predecoherence, as its name indicates, is the same physical effect as
decoherence, originating in the same interactions with an environment,
injecting also incoherence and breaking unitarity. But whereas decoherence acts
immediately after a measurement, predecoherence is acting long before. It is
also a very strong effect and its main properties are established in this
paper, including generation, transport, damping, and stationary level. A
mechanism for objectification, or wave function collapse, is also proposed as
consisting in a perturbation by predecoherence of the intricacy between a
measuring system and a measured one. The theory is made explicit on a special
example and the quantitative results are found sensible.
|
1205.6390v1
|
2012-05-29
|
An iterative domain decomposition method for free boundary problems with nonlinear flux jump constraint
|
In this paper we design an iterative domain decomposition method for free
boundary problems with nonlinear flux jump condition. Our approach is related
to damped Newton's methods. The proposed scheme requires, in each iteration,
the approximation of the flux on (both sides of) the free interface. We present
a Finite Element implementation of our method. The numerical implementation
uses harmonically deformed triangulations to inexpensively generate finite
element meshes in subdomains. We apply our method to a simplified model for jet
flows in pipes and to a simple magnetohydrodynamics model. Finally, we present
numerical examples studying the convergence of our scheme.
|
1205.6429v1
|
2012-05-30
|
Defeating entanglement sudden death by a single local filtering
|
Genuine multipartite entanglement of a quantum system can be partially
destroyed by local decoherence. Is it possible to retrieve the entanglement to
some extent by a single local operation? The answer to this question depends
very much on the type of initial genuine entanglement. For initially pure W and
cluster states and if the decoherence is given by generalized amplitude
damping, the answer is shown to be positive. In this case, the entanglement
retrieving is achieved just by redistributing the remained entanglement of the
system.
|
1205.6601v1
|
2012-06-22
|
Finite-size scaling in the quantum phase transition of the open-system Dicke-model
|
Laser-driven Bose-Einstein condensate of ultracold atoms loaded into a lossy
high-finesse optical resonator exhibits critical behavior and, in the
thermodynamic limit, a phase transition between stationary states of different
symmetries. The system realizes an open-system variant of the celebrated
Dicke-model. We study the transition for a finite number of atoms by means of a
Hartree-Fock-Bogoliubov method adapted to a damped-driven open system. The
finite-size scaling exponents are determined and a clear distinction between
the non-equilibrium and the equilibrium quantum criticality is found.
|
1206.5131v1
|
2012-06-27
|
Domain wall propagation through spin wave emission
|
We theoretically study field-induced domain wall (DW) motion in an
electrically insulating ferromagnet with hard- and easy-axis anisotropies. DWs
can propagate along a dissipationless wire through spin wave emission locked
into the known soliton velocity at low fields. In the presence of damping, the
mode appears before the Walker breakdown field for strong out-of-plane magnetic
anisotropy, and the usual Walker rigid-body propagation mode becomes unstable
when the field is between the maximal-DW-speed field and Walker breakdown
field.
|
1206.6244v1
|
2012-07-10
|
The missing asymptotic sector of rotating black-hole spectroscopy
|
The rotation of a black hole splits its spectrum in two, yet only one sector
is known in the highly-damped regime. We find the second, at least partly
oblate sector, with quasinormal modes approaching the total reflection
frequencies \omega(n>>1) ~ m\Omega - 2\pi iT(n-s), where \Omega and T are the
horizon angular velocity and temperature, s is the field spin, and m is an
azimuthal eigenvalue. Some physical implications are discussed.
|
1207.2460v1
|
2012-07-22
|
Asymptotic dynamics of the alternate degrees of freedom for a two-mode system: an analytically solvable model
|
The composite systems can be non-uniquely decomposed into parts (subsystems).
Not all decompositions (structures) of a composite system are equally
physically relevant. In this paper we answer on theoretical ground why it may
be so. We consider a pair of mutually un-coupled modes in the phase space
representation that are subjected to the independent quantum amplitude damping
channels. By investigating asymptotic dynamics of the degrees of freedom, we
find that the environment is responsible for the structures non-equivalence.
Only one structure is distinguished by both locality of the environmental in
uence on its subsystems and a classical-like description.
|
1207.5260v1
|
2012-07-24
|
Van Kampen modes for bunch longitudinal motion
|
Conditions for existence, uniqueness and stability of bunch steady states are
considered. For the existence uniqueness problem, simple algebraic equations
are derived, showing the result both for the action and Hamiltonian domain
distributions. For the stability problem, van Kampen theory is used. Emerging
of discrete van Kampen modes show either loss of Landau damping, or
instability. This method can be applied for an arbitrary impedance, RF shape
and beam distribution function Available areas on intensity-emittance plane are
shown for resistive wall wake and single harmonic, bunch shortening and bunch
lengthening RF configurations.
|
1207.5826v1
|
2012-07-30
|
A Nonlinear Dynamics Characterization of The Scrape-off Layer Plasma Fluctuations
|
A stochastic differential equation for the plasma density dynamics is
derived, consistent with the experimentally measured distribution and the
theoretical quadratic nonlinearity. The plasma density is driven by a
multiplicative Wiener process and evolves on the turbulence correlation time
scale, while the linear growth is quadratically damped by the fluctuation
level. The sensitivity of intermittency to the nonlinear dynamics is
investigated by analyzing the Langevin representation of two intermittent
distributions, showing the agreement between the quadratic nonlinearity and the
gamma distribution.
|
1207.6981v2
|
2012-08-03
|
Scaling of the Rényi entropies in gapped quantum spin systems: Entanglement-driven order beyond symmetry breaking
|
We investigate the scaling of the R\'enyi $\alpha$-entropies in
one-dimensional gapped quantum spin models. We show that the block entropies
with $\alpha > 2$ violate the area law monotonicity and exhibit damped
oscillations. Depending on the existence of a factorized ground state, the
oscillatory behavior occurs either below factorization or it extends
indefinitely. The anomalous scaling corresponds to an entanglement-driven order
that is independent of ground-state degeneracy and is revealed by a nonlocal
order parameter defined as the sum of the single-copy entanglement over all
blocks.
|
1208.0735v1
|
2012-09-01
|
Radiative energy loss of relativistic charged particles in absorptive media
|
We determine the energy loss spectrum per time-interval of a relativistic
charge traversing a dispersive medium. Polarization and absorption effects in
the medium are modelled via a complex index of refraction. We find that the
spectrum amplitude becomes exponentially damped due to absorption mechanisms.
Taking explicitly the effect of multiple scatterings on the charge trajectory
into account, we confirm results obtained in a previous work.
|
1209.0077v1
|
2012-09-01
|
Approximation of the random inertial manifold of singularly perturbed stochastic wave equations
|
By applying Rohlin's result on the classification of homomorphisms of
Lebesgue space, the random inertial manifold of a stochastic damped nonlinear
wave equations with singular perturbation is proved to be approximated almost
surely by that of a stochastic nonlinear heat equation which is driven by a new
Wiener process depending on the singular perturbation parameter. This
approximation can be seen as the Smolukowski--Kramers approximation as time
goes to infinity. However, as time goes infinity, the approximation changes
with the small parameter, which is different from the approximation on a finite
interval.
|
1209.0090v1
|
2012-09-03
|
Focusing in Multiwell Potentials: Applications to Ion Channels
|
We investigate out of equilibrium stationary distributions induced by a
stochastic dichotomous noise on double and multi-well models for ion channels.
Ion-channel dynamics is analyzed both through over-damped Langevin equations
and master equations. As a consequence of the external stochastic noise, we
prove a non trivial focusing effect, namely the probability distribution is
concentrated only on one state of the multi-well model. We also show that this
focusing effect, which occurs at physiological conditions, cannot be predicted
by a simple master equation approach.
|
1209.0505v2
|
2012-09-05
|
Dynamical excitations in the collision of 2D Bose-Einstein condensates
|
We carry out simulations of the collision of two components of an
adiabatically divided, quasi-2D BEC. We identify under, over and critically
damped regimes in the dipole oscillations of the components according to the
balance of internal and centre-of-mass (c.m.) energies of the components and
investigate the creation of internal excitations. We distinguish the behaviour
of this system from previous studies of quasi-1D BEC's. In particular we note
that the nature of the internal excitations is only essentially sensitive to an
initial phase difference between the components in the overdamped regime.
|
1209.0840v2
|
2012-09-10
|
Trajectory trapping and the evolution of drift turbulence beyond the quasilinear stage
|
Test modes on turbulent magnetized plasmas are studied taking into account
the ion trapping that characterizes the E x B drift in the background
turbulence. We show that trappyng provides the physical mechanism for the
formation of large scale potential structures (inverse cascade) observed in
drift turbulence. Trapping combined with the motion of the potential with the
diamagnetic velocity determines ion flows in opposite directions, which reduce
the growth rate and eventually damps the drift modes. It also determine
transitory zonal flow modes in connection with compressibility effect due to
the polarization drift in the background turbulence.
|
1209.2083v1
|
2012-09-14
|
Skyrmion Dynamics in Multiferroic Insulator
|
Recent discovery of Skyrmion crystal phase in insulating multiferroic
compound Cu$_2$OSeO$_3$ calls for new ways and ideas to manipulate the
Skyrmions in the absence of spin transfer torque from the conduction electrons.
It is shown here that the position-dependent electric field, pointed along the
direction of the average induced dipole moment of the Skyrmion, can induce the
Hall motion of Skyrmion with its velocity orthogonal to the field gradient.
Finite Gilbert damping produces longitudinal motion. We find a rich variety of
resonance modes excited by a.c. electric field.
|
1209.3120v1
|
2012-09-15
|
Cavity Optomechanics with a Bose-Einstein Condensate: Normal Mode Splitting
|
We study the normal mode splitting in a system consisting of a Bose Einstein
condensates (BECs) trapped inside a Fabry Perot cavity driven by a single mode
laser field. We analyze the variations in frequency and damping rate of the
collective density excitation of a BEC imparted by the optical field. We study
the occurrence of normal mode splitting which appears as consequences of the
hybridization of the fluctuations of the intracavity field and the condensate
mode. It is shown that normal mode splitting vanishes for weak coupling between
the condensate mode and the intracavity field. Moreover, we investigate the
normal mode splitting in the transmission spectrum of the cavity field.
|
1209.3354v1
|
2012-09-19
|
Entropy evolution law in a laser process
|
For the first time, we obtain the entropy variation law in a laser process
after finding the Kraus operator of the master equation describing the laser
process with the use of the entangled state representation. The behavior of
entropy is determined by the competition of the gain and damping in the laser
process. The photon number evolution formula is also obtained.
|
1209.4149v2
|
2012-09-26
|
Impact of r-modes on the cooling of neutron stars
|
Studying the frequency and temperature evolution of a compact star can give
us valuable information about the microscopic properties of the matter inside
the star. In this paper we study the effect of dissipative reheating of a
neutron star due to r-mode oscillations on its temperature evolution. We find
that there is still an impact of an r-mode phase on the temperature long after
the star has left the instability region and the r-mode is damped completely.
With accurate temperature measurements it may be possible to detect this trace
of a previous r-mode phase in observed pulsars.
|
1209.5962v1
|
2012-10-10
|
Dissipation-Assisted Quantum Information Processing with Trapped Ions
|
We introduce a scheme to perform dissipation-assisted quantum information
processing in ion traps considering realistic decoherence rates, for example,
due to motional heating. By means of continuous sympathetic cooling, we
overcome the trap heating, and show that the damped vibrational excitations can
still be exploited to mediate coherent interactions as well as collective
dissipative effects. We describe how to control their relative strength
experimentally, allowing for protocols of coherent or dissipative generation of
entanglement. This scheme can be scaled to larger ion registers for coherent or
dissipative many-body quantum simulations.
|
1210.2860v3
|
2012-10-12
|
Bulk-like viscosity and shear thinning during dynamic compression of a nanoconfined liquid
|
The viscosity of liquids under nanoconfinement remains controversial. Reports
range from spontaneous solidification to no change in the viscosity at all.
Here, we present thorough measurements with a small-amplitude linear atomic
force microscopy technique and careful consideration of the confinement
geometry, to show that in a weakly interacting liquid, average viscosity
remains bulk like, except for strong shear thinning once the liquid is confined
to less than four molecular layers. Overlaid over this bulk-like viscous
behavior are stiffness and damping oscillations, indicating non-continuum
behavior, as well as an elastic response when the liquid is allowed to order in
the confinement gap.
|
1210.3540v1
|
2012-10-14
|
Quasinormal frequencies using the hidden conformal symmetry of the Schwarzschild black hole
|
We show that the hidden conformal symmetry of the Schwarzschild black hole is
realized from the AdS$_2$ sector of the AdS$_2\times S^2$, but not from the
Rindler spacetime which is the genuine near-horizon geometry of the
Schwarzschild black hole. This implies that purely imaginary quasinormal
frequencies obtained using the hidden conformal symmetry is not suitable for
describing the largely damped modes around the Schwarzschild black hole.
|
1210.3760v2
|
2012-10-18
|
Giant dipole resonance in $^{201}$Tl at low temperature
|
The thermal pairing gap obtained by embedding the exact solutions of the
pairing problem into the canonical ensemble is employed to calculate the width
and strength function of the giant dipole resonance (GDR) within the phonon
damping model. The results of calculations describe reasonably well the data
for the GDR width as well as the GDR linearized strength function, recently
obtained for $^{201}$Tl in the temperature region between 0.8 and 1.2 MeV,
which other approaches that neglect the effect of non-vanishing thermal pairing
fail to describe.
|
1210.5011v1
|
2012-10-19
|
A kinetic model of radiating electrons
|
A kinetic theory is developed to describe radiating electrons whose motion is
governed by the Lorentz-Dirac equation. This gives rise to a generalized Vlasov
equation coupled to an equation for the evolution of the physical submanifold
of phase space. The pathological solutions of the 1-particle theory may be
removed by expanding the latter equation in powers of $\tau := q^2/ 6\pi m$.
The radiation-induced change in entropy is explored, and its physical origin is
discussed. As a simple demonstration of the theory, the radiative damping rate
of longitudinal plasma waves is calculated.
|
1210.5467v1
|
2012-10-22
|
Excitations in a quantum spin liquid with random bonds
|
We present results of inelastic neutron scattering study on two bond
disordered quasi twodimensional quantum magnets
(C$_4$H$_12$N$_2$)Cu$_2$(Cl$_{1-x}$Br$_x$)$_6$ with x=0.035 and 0.075. We
observe the increase of spin gap, reduction of magnon bandwidth and a decrease
of magnon lifetimes compared to x=0 sample. Additional magnon damping is
observed at higher energies away from zone center which is found to follow the
density of single particle states.
|
1210.5899v1
|
2012-10-23
|
Solution of electric-field-driven tight-binding lattice in contact with fermion reservoir
|
Electrons in tight-binding lattice driven by DC electric field dissipate
their energy through on-site fermionic thermostats. Due to the translational
invariance in the transport direction, the problem can be block-diagonalized.
We solve this time-dependent quadratic problem and demonstrate that the problem
has an oscillatory steady-state. The steady-state occupation number shows that
the Fermi surface disappears for any damping from the thermostats and any
finite electric field. Despite the lack of momentum scattering, the
conductivity takes the same form as the semi-classical Ohmic expression from
the relaxation-time approximation.
|
1210.6297v2
|
2012-10-27
|
Magnet traveling through a conducting pipe: a variation on the analytical approach
|
We present an analytical study of magnetic damping. In particular, we
investigate the dynamics of a cylindrical neodymium magnet as it moves through
a conducting tube. Owing to the very high degree of uniformity of the
magnetization for neodymium magnets, we are able to provide completely
analytical results for the EMF generated in the pipe, and the consequent
retarding force. Our analytical expressions are shown to have excellent
agreement with experimental observations.
|
1210.7796v1
|
2012-11-01
|
Quantum and classical dissipation of charged particles
|
A Hamiltonian approach is presented to study the two dimensional motion of
damped electric charges in time dependent electromagnetic fields. The classical
and the corresponding quantum mechanical problems are solved for particular
cases using canonical transformations applied to Hamiltonians for a particle
with variable mass. The Green's function is constructed and, from it, the
motion of a Gaussian wave packet is studied in detail.
|
1211.0067v2
|
2012-11-01
|
Oscillatory dynamics and non-markovian memory in dissipative quantum systems
|
The nonequilibrium dynamics of a small quantum system coupled to a
dissipative environment is studied. We show that (1) the oscillatory dynamics
close to a coherent-to-incoherent transition is surprisingly different from the
one of the classical damped harmonic oscillator and that (2) non-markovian
memory plays a prominent role in the time evolution after a quantum quench.
|
1211.0293v3
|
2012-11-12
|
Spinning dust radiation: a review of the theory
|
This article reviews the current status of theoretical modeling of electric
dipole radiation from spinning dust grains. The fundamentally simple problem of
dust grain rotation appeals to a rich set of concepts of classical and quantum
physics, owing the the diversity of processes involved. Rotational excitation
and damping rates through various mechanisms are discussed, as well as methods
of computing the grain angular momentum distribution function. Assumptions on
grain properties are reviewed. The robustness of theoretical predictions now
seems mostly limited by the uncertainties regarding the grains themselves,
namely their abundance, dipole moments, size and shape distribution.
|
1211.2748v1
|
2012-11-15
|
Voltage-controlled surface plasmon-polaritons in double graphene layer structures
|
We study the spectra and damping of surface plasmon-polaritons in double
graphene layer structures. It is shown that application of bias voltage between
layers shifts the edge of plasmon absorption associated with the interband
transitions. This effect could be used in efficient plasmonic modulators. We
reveal the influence of spatial dispersion of conductivity on plasmonic spectra
and show that it results in the shift of cutoff frequency to the higher values.
|
1211.3629v2
|
2012-11-25
|
Realignment Entanglement Criterion for Continuous Bipartite Symmetric Quantum States
|
The separability of bipartite non-Gaussian states is studied by applying the
realignment criterion with the technique of functional analysis. The
realignment criterion is given as one inequality in contrast to the infinitive
number of inequalities based on the moments. We give the necessary and
sufficient condition of inseparability for non-Gaussian states prepared by
photon subtraction or addition from symmetric Gaussian states. The entanglement
criterion of non-Gaussian states evolved in thermal noise and amplitude damping
environment is also obtained.
|
1211.5725v2
|
2012-12-07
|
Well-posedness and stabilization of a model system for long waves posed on a quarter plane
|
In this paper we are concerned with a initial boundary-value problem for a
coupled system of two KdV equations, posed on the positive half line, under the
effect of a localized damping term. The model arises when modeling the
propagation of long waves generated by a wave maker in a channel. It is shown
that the solutions of the system are exponential stable and globally well-posed
in the weighted space $L^2(e^{2bx}dx)$ for $b>0$. The stabilization problem is
studied using a Lyapunov approach while the well-posedness result is obtained
combining fixed point arguments and energy type estimates.
|
1212.1602v1
|
2012-12-07
|
Molecular Dynamics and OKMC Study of Radiation Induced Motion of Voids and He Bubbles in BCC Iron
|
We show that voids adjacent to radiation damage cascades can be moved in
their entirety by several lattice spacings. This is done using molecular
dynamics cascade simulations in iron at energies of 1-5 keV. The effect of this
mechanism is studied further using an OKMC code and shows enhancement of void
diffusion by 2 orders of magnitude from 1x10^-22 cm^2/s to 3x10^-20 cm^2/s.
Repeating the study on He bubbles shows that the movement is damped by the
presence of helium in the void.
|
1212.1652v2
|
2012-12-17
|
Soft Mode in cubic PbTiO3 by Hyper-Raman Scattering
|
Hyper-Raman scattering experiments allowed collecting the spectra of the
lowest F1u-symmetry mode of PbTiO3 crystal in the paraelectric phase up to 930K
as well as down to about 1K above the phase transition. It is realized that
this mode is fully responsible for the Curie-Weiss behavior of its dielectric
permittivity above Tc. Near the phase transition, this phonon frequency softens
down to 17 cm-1 and its spectrum can be well modeled as a response of a single
damped harmonic oscillator. It is concluded that PbTiO3 constitutes a clean
example of a soft mode-driven ferroelectric system.
|
1212.3982v1
|
2012-12-26
|
Entropy production in open quantum systems: exactly solvable qubit models
|
We present analytical results for the time-dependent information entropy in
exactly solvable two-state (qubit) models. The first model describes dephasing
(decoherence) in a qubit coupled to a bath of harmonic oscillators. The entropy
production for this model in the regimes of "complete" and "incomplete"
decoherence is discussed. As another example, we consider the damped
Jaynes-Cummings model describing a spontaneous decay of a two-level system into
the field vacuum. It is shown that, for all strengths of coupling, the open
system passes through the mixed state with the maximum information entropy.
|
1212.6135v1
|
2012-12-12
|
Expectation Propogation for approximate inference in dynamic Bayesian networks
|
We describe expectation propagation for approximate inference in dynamic
Bayesian networks as a natural extension of Pearl s exact belief
propagation.Expectation propagation IS a greedy algorithm, converges IN many
practical cases, but NOT always.We derive a DOUBLE - loop algorithm, guaranteed
TO converge TO a local minimum OF a Bethe free energy.Furthermore, we show that
stable fixed points OF (damped) expectation propagation correspond TO local
minima OF this free energy, but that the converse need NOT be the CASE .We
illustrate the algorithms BY applying them TO switching linear dynamical
systems AND discuss implications FOR approximate inference IN general Bayesian
networks.
|
1301.0572v1
|
2013-01-09
|
Spectral function of the Bloch-Nordsieck model at finite temperature
|
In this paper we determine the exact fermionic spectral function of the
Bloch-Nordsieck model at finite temperature. Analytic results are presented for
some special parameters, for other values we have numerical results. The
spectral function is finite and normalizable for any nonzero temperature
values. The real time dependence of the retarded Green's function is power-like
for small times and exhibits exponential damping for large times. Treating the
temperature as an infrared regulator, we can also give a safe interpretation of
the zero temperature result.
|
1301.1803v1
|
2013-01-09
|
Quantum Refrigerator
|
We consider fault-tolerant quantum computation in the context where there are
no fresh ancilla qubits available during the computation, and where the noise
is due to a general quantum channel. We show that there are three classes of
noisy channels: In the first, typified by the depolarizing channel, computation
is only possible for a logarithmic time. In the second class, of which the
dephasing channel is an example, computation is possible for polynomial time.
The amplitude damping channel is an example of the third class, and for this
class of channels, it is possible to compute for an exponential time in the
number of qubits available.
|
1301.1995v1
|
2013-01-14
|
Direct transition from quantum escape to phase diffusion regime in YBaCuO biepitaxial Josephson Junctions
|
Dissipation encodes interaction of a quantum system with the environment and
regulates the activation regimes of a Brownian particle. We have engineered
grain boundary biepitaxial YBaCuO junctions to drive a direct transition from
quantum activated running state to phase diffusion regime. The cross-over to
the quantum regime is tuned by the magnetic field and dissipation is encoded in
a fully consistent set of junction parameters. To unravel phase dynamics in
moderately damped systems is of general interest for advances in the
comprehension of retrapping phenomena and in view of quantum hybrid technology.
|
1301.3162v1
|
2013-01-18
|
Nonlinear dynamical systems and linearly forced isotropic turbulence
|
In this paper, we present an extensive study of linearly forced isotropic
turbulence. By using an analytical method, we identified two parametric choices
that are new to our knowledge. We proved that the underlying nonlinear
dynamical system for linearly forced isotropic turbulence is the general case
of a cubic Lienard equation with linear damping (Dumortier and Rousseau 1990).
|
1301.4383v2
|
2013-01-28
|
Comparison of f-Q scaling in wineglass and radial modes in ring resonators
|
Low phase noise MEMS oscillators necessitate resonators with high f-Q.
Resonators achieving high f-Q (mechanical frequency-quality factor product)
close to the thermo-elastic damping (TED) limit have been demonstrated at
expense of feed-through. Here we present a study comparing frequency scaling of
quality factors of wineglass and radial modes in a ring resonator using an
opto-mechanical two port transmission measurement. Higher harmonics of the
wineglass mode show an increasing trend in the f-Q product, as compared to a
saturation of f-Q for radial modes. The measured f-Q of 5.11e13Hz at 9.82GHz in
air at room temperature for a wineglass mode is close to the highest measured
values in silicon resonators.
|
1301.6564v1
|
2013-02-08
|
Comparison of quantum and classical relaxation in spin dynamics
|
The classical Landau-Lifshitz equation with damping term has been derived
from the time evolution of a quantum mechanical wave function under the
assumption of a non-hermitian Hamilton operator. Further, the trajectory of a
classical spin $\mathrm{S}$ has been compared with the expectation value of the
spin operator $\mathrm{\hat{S}}$. A good agreement between classical and
quantum mechanical trajectories can be found for Hamiltonians linear in
$\mathrm{\hat{S}}$ respectively $\mathrm{S}$. Quadratic or higher order terms
in the Hamiltonian result in a disagreement.
|
1302.1985v1
|
2013-02-20
|
Convergence to Gibbs equilibrium - unveiling the mystery
|
We consider general hamiltonian systems with quadratic interaction potential
and $N<\infty$ degrees of freedom, only $m$ of which have contact with external
world, that is subjected to damping and random stationary external forces. We
show that, as $t\to\infty$, already for $m=1$, the unique limiting distribution
exists for almost all interactions. Moreover, it is Gibbs if the external force
is the white noise, but typically not Gibbs for gaussian processes with smooth
trajectories. This conclusion survives also in the thermodynamic limit
$N\to\infty$.
|
1302.4832v2
|
2013-02-20
|
Doping Induced Spin State Transition in LaCoO3: Dynamical Mean-Field Study
|
Hole and electron doped LaCoO3 is studied using dynamical mean-field theory.
The one-particle spectra are analyzed and compared to the available
experimental data, in particular the x-ray absorption spectra. Analyzing the
temporal spin-spin correlation functions we find the atomic intermediate spin
state is not important for the observed Curie-Weiss susceptibility. Contrary to
the commonly held view about the roles played by the t2g and eg electrons we
find narrow quasiparticle bands of t2g character crossing the Fermi level
accompanied by strongly damped eg excitations.
|
1302.4925v2
|
2013-02-20
|
Quantum speed limit for non-Markovian dynamics
|
We derive a Margolus-Levitin type bound on the minimal evolution time of an
arbitrarily driven open quantum system. We express this quantum speed limit
time in terms of the operator norm of the nonunitary generator of the dynamics.
We apply these results to the damped Jaynes-Cummings model and demonstrate that
the corresponding bound is tight. We further show that non-Markovian effects
can speed up quantum evolution and therefore lead to a smaller quantum speed
limit time.
|
1302.5069v2
|
2013-02-21
|
Flow Vorticity in Peripheral High Energy Heavy Ion Collisions
|
The vorticity development is studied in the reaction plane of peripheral
relativistic heavy ion reactions where the initial state has substantial
angular momentum. The earlier predicted rotation effect and Kelvin Helmholtz
Instability, lead to significant initial vorticity and circulation. In low
viscosity QGP this vorticity remains still significant at the time of freeze
out of the system, even if damping due to the explosive expansion and the
dissipation decreases the vorticity and circulation. In the reaction plane the
vorticity arises from the initial angular momentum, and it is stronger than in
the transverse plane where vorticity is caused by random fluctuations only.
|
1302.5310v1
|
2013-02-21
|
Gravity-related wave function collapse: Is superfluid He exceptional?
|
The gravity-related model of spontaneous wave function collapse, a longtime
hypothesis, damps the massive Schr\"odinger Cat states in quantum theory. We
extend the hypothesis and assume that spontaneous wave function collapses are
responsible for the emergence of Newton interaction. Superfluid helium would
then show significant and testable gravitational anomalies.
|
1302.5364v1
|
2013-02-28
|
Deterministic macroscopic quantum superpositions of motion via quadratic optomechanical coupling
|
We propose a scheme to prepare macroscopic quantum superpositions of motion
in optomachanical nano- or micromechanical oscillators quadratically coupled to
an intracavity field. The nonlinear optomechanical coupling leads to an
effective degenerate three-wave mixing interaction between the mechanical and
cavity modes. The quantum superpositions result from the combined effects of
the interaction and cavity dissipation. We show analytically and confirm
numerically that various deterministic quantum superpositions can be achieved,
depending on initial mechanical state. The effect of mechanical damping is also
studied in detail via the negativity of the Wigner function. The present scheme
can be realized in various optomechanical systems with current technology.
|
1302.7087v1
|
2013-03-06
|
Beam loading
|
We begin by giving a description of the radio-frequency generator-cavity-beam
coupled system in terms of basic quantities. Taking beam loading and cavity
detuning into account, expressions for the cavity impedance as seen by the
generator and as seen by the beam are derived. Subsequently methods of
beam-loading compensation by cavity detuning, radio-frequency feedback and
feedforward are described. Examples of digital radio-frequency phase and
amplitude control for the special case of superconducting cavities are also
given. Finally, a dedicated phase loop for damping synchrotron oscillations is
discussed.
|
1303.1358v1
|
2013-03-18
|
On decay and blow-up of solutions for a singular nonlocal viscoelastic problem with a nonlinear source term
|
In this paper we consider a singular nonlocal viscoelastic problem with a
nonlinear source term and a possible damping term. We proved that if the
initial data enter into the stable set, the solution exists globally and decays
to zero with a more general rate, and if the initial data enter into the
unstable set, the solution with non-positive initial energy as well as positive
initial energy blows up in finite time. These are achieved by using the
potential well theory, the modified convexity method and the perturbed energy
method.
|
1303.4246v1
|
2013-03-19
|
Complexity and simplicity of plasmas
|
This paper has two main parts. The first one presents a direct path from
microscopic dynamics to Debye screening, Landau damping and collisional
transport. It shows there is more simplicity in microscopic plasma physics than
previously thought. The second part is more subjective. It describes some
difficulties in facing plasma complexity in general, suggests an inquiry about
the methods used empirically to tackle complex systems, discusses the teaching
of plasma physics as a physics of complexity, and proposes new directions to
face the inflation of information.
|
1303.4613v2
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.