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2009-03-08 | Enhancement of transmission rates in quantum memory channels with damping | We consider the transfer of quantum information down a single-mode quantum
transmission line. Such quantum channel is modeled as a damped harmonic
oscillator, the interaction between the information carriers -a train of N
qubits- and the oscillator being of the Jaynes-Cummings kind. Memory effects
appear if the state of the oscillator is not reset after each channel use. We
show that the setup without resetting is convenient in order to increase the
transmission rates, both for the transfer of quantum and classical private
information. Our results can be applied to the micromaser. | 0903.1424v1 |
2009-03-15 | A variational approach to strongly damped wave equations | We discuss a Hilbert space method that allows to prove analytical
well-posedness of a class of linear strongly damped wave equations. The main
technical tool is a perturbation lemma for sesquilinear forms, which seems to
be new. In most common linear cases we can furthermore apply a recent result
due to Crouzeix--Haase, thus extending several known results and obtaining
optimal analyticity angle. | 0903.2599v2 |
2009-03-30 | Damping of Exciton Rabi Rotations by Acoustic Phonons in Optically Excited InGaAs/GaAs Quantum Dots | We report experimental evidence identifying acoustic phonons as the principal
source of the excitation-induced-dephasing (EID) responsible for the intensity
damping of quantum dot excitonic Rabi rotations. The rate of EID is extracted
from temperature dependent Rabi rotation measurements of the ground-state
excitonic transition, and is found to be in close quantitative agreement with
an acoustic-phonon model. | 0903.5278v2 |
2009-05-13 | Landau damping | In this note we present the main results from the recent work
hal-00376547/arXiv:0904.2760, which for the first time establish Landau damping
in a nonlinear context. | 0905.2167v2 |
2009-05-13 | Amortissement Landau | Dans cette note nous pr\'esentons les principaux r\'esultats du r\'ecent
travail hal-00376547/arXiv:0904.2760, o\`u le ph\'enom\`ene d'amortissement
Landau est pour la premi\`ere fois \'etabli dans un contexte non lin\'eaire.
-----
In this note we present the main results from the recent work hal-00376547 /
arXiv:0904.2760, which for the first time establish Landau damping in a
nonlinear context. | 0905.2168v2 |
2009-06-27 | Effect of Bohm potential on a charged gas | Bohm's interpretation of Quantum Mechanics leads to the derivation of a
Quantum Kinetic Equation (QKE): in the present work, propagation of waves in
charged quantum gases is investigated starting from this QKE. Dispersion
relations are derived for fully and weakly degenerate fermions and bosons
(these latter above critical temperature), and the differences underlined. Use
of a kinetic equation permits investigation of "Landau-type" damping: it is
found that the presence of damping in fermion gases is dependent upon the
degree of degeneracy, whereas it is always present in boson gases. In fully
degenerate fermions a phenomenon appears that is akin to the "zero sound"
propagation. | 0906.5061v1 |
2009-09-11 | Energy decay for the damped wave equation under a pressure condition | We establish the presence of a spectral gap near the real axis for the damped
wave equation on a manifold with negative curvature. This results holds under a
dynamical condition expressed by the negativity of a topological pressure with
respect to the geodesic flow. As an application, we show an exponential decay
of the energy for all initial data sufficiently regular. This decay is governed
by the imaginary part of a finite number of eigenvalues close to the real axis. | 0909.2093v1 |
2009-09-12 | Signature of smooth transition from diabatic to adiabatic states in heavy-ion fusion reactions at deep subbarrier energies | We propose a novel extension of the standard coupled-channels framework for
heavy-ion reactions in order to analyze fusion reactions at deep subbarrier
incident energies. This extension simulates a smooth transition between the
diabatic two-body and the adiabatic one-body states. To this end, we damp
gradually the off-diagonal part of the coupling potential, for which the
position of the onset of the damping varies for each eigen channel. We show
that this model accounts well for the steep falloff of the fusion cross
sections for the $^{16}$O+$^{208}$Pb, $^{64}$Ni+$^{64}$Ni, and
$^{58}$Ni+$^{58}$Ni reactions. | 0909.2298v1 |
2009-10-05 | Construction of quasi-periodic response solutions in forced strongly dissipative systems | We consider a class of ordinary differential equations describing
one-dimensional quasiperiodically forced systems in the presence of large
damping. We give a fully constructive proof of the existence of response
solutions, that is quasi-periodic solutions which have the same frequency
vector as the forcing. This requires dealing with a degenerate implicit
function equation: we prove that the latter has a unique solution, which can be
explicitly determined. As a by-product we obtain an explicit estimate of the
minimal size of the damping coefficient. | 0910.0746v1 |
2009-10-14 | Plasmon-phonon Strongly-Coupled Mode in Epitaxial Graphene | We report the dispersion measurements, using angle-resolved reflection
electron-energy-loss-spectroscopy (AREELS), on two-dimensional (2D) plasmons in
single and multilayer graphene which couple strongly to surface optical phonon
(FK phonon) modes of silicon carbide substrate. The coupled modes show discrete
dispersion behaviors in the single and bilayer graphene. With increasing
graphene layers on SiC(0001), a transition from plasmon-like dispersion to
phonon-like dispersion is observed. For plasmon-like modes, the dispersion is
strongly damped by electron-hole pair excitations at entering single-particle
continuum, while phonon-like mode is undamped. In the region free of coupling,
the graphene 2D plasmon exhibits acoustic behavior with linear dispersion with
slope and damping determined by the Fermi surface topology. | 0910.2735v1 |
2009-10-23 | Collective Enhancement and Suppression of Excitation Decay in Optical Lattices | We calculate radiative lifetimes of collective electronic excitations of
atoms in an infinite one dimensional lattice. The translational symmetry along
the lattice restricts the photon wave vector component parallel to the lattice
to the exciton wave number and thus the possible emission directions. The
resulting radiation damping rate and emission pattern of the exciton strongly
deviates from independent atom. For some wave numbers and polarizations the
excitons superradiantly decay very fast, while other excitons show zero
radiation damping rate and form propagating meta-stable excitations. Such
states could be directly coupled via tailored evanescent fields from a nearby
fiber. | 0910.4501v1 |
2009-10-24 | Global Attractor for Weakly Damped Forced KdV Equation in Low Regularity on T | In this paper we consider the long time behavior of the weakly damped, forced
Korteweg-de Vries equation in the Sololev spaces of the negative indices in the
periodic case. We prove that the solutions are uniformly bounded in
$\dot{H}^s(\T)$ for $s>-\dfrac{1}{2}$. Moreover, we show that the solution-map
possesses a global attractor in $\dot{H}^s(\T)$ for $s>-\dfrac{1}{2}$, which is
a compact set in $H^{s+3}(\T)$. | 0910.4652v1 |
2009-11-12 | A new perspective on supersymmetric inflation | We consider supersymmetric inflation with the hybrid-type potential. In the
absence of the symmetry that forbids Hubble-induced mass terms, the inflaton
mass will be as large as the Hubble scale during inflation. We consider
gravitational decay of the trigger field as the least decay mode and find that
the damping caused by the dissipation can dominate the friction of the inflaton
when the heavy trigger field is coupled to the inflaton. The dissipative
damping provides a solution to the traditional $\eta$ problem without
introducing additional symmetry and interactions. Considering the spatial
inhomogeneities of the dissipative coefficient, we find that modulated
inflation (modulation of the inflaton velocity) can create significant
curvature perturbations. | 0911.2350v1 |
2009-12-15 | Distillability sudden death in qutrit-qutrit systems under amplitude damping | Recently it has been discovered that certain two-qutrit entangled states
interacting with global and/or multi-local decoherence undergo distillability
sudden death (DSD). We investigate this phenomenon for qutrit-qutrit systems
interacting with statistically independent zero-temperature reservoirs. We show
that certain initially prepared free-entangled states become bound-entangled in
a finite time due to the action of Markovian dissipative environment. Moreover,
in contrast with local dephasing, simple local unitary transformations can
completely avoid distillability sudden death under amplitude damping. | 0912.2868v1 |
2009-12-15 | Global Controllability of Multidimensional Rigid Body by Few Torques | We study global controllability of 'rotating' multidimensional rigid body
(MRB) controlled by application of few torques. Study by methods of geometric
control requires analysis of algebraic structure introduced by the quadratic
term of Euler-Frahm equation. We discuss problems, which arise in the course of
this analysis, and establish several global controllability criteria for damped
and non damped cases. | 0912.2900v1 |
2010-02-05 | Damping Effect of Electromagnetic Radiation and Time-Dependent Schrodinger Equation | The inexactness of the time-dependent Schr\"odinger equation of a charged
particle in an external electromagnetic field is discussed in terms of the
damping effect of the radiation. A possible improvement is to add a nonlinear
term representing this effect to the linear Schr\"odinger equation. Conditions
for the nonlinear term are investigated and it is demonstrated that the
obtained nonlinear Schr\"odinger equation may present state evolutions similar
to the wave-function reduction and transitions between stationary states. | 1002.1116v3 |
2010-02-05 | Uniform stabilization in weighted Sobolev spaces for the KdV equation posed on the half-line | Studied here is the large-time behavior of solutions of the Korteweg-de Vries
equation posed on the right half-line under the effect of a localized damping.
Assuming as in \cite{linares-pazoto} that the damping is active on a set
$(a_0,+\infty)$ with $a_0>0$, we establish the exponential decay of the
solutions in the weighted spaces $L^2((x+1)^mdx)$ for $m\in \N ^*$ and
$L^2(e^{2bx}dx)$ for $b>0$ by a Lyapunov approach. The decay of the spatial
derivatives of the solution is also derived. | 1002.1127v1 |
2010-03-28 | Giant magnetic broadening of ferromagnetic resonance in a GMR Co/Ag/Co/Gd quadlayer | Both magnetic-resonance damping and the giant magnetoresistance effect have
been predicted to be strongly affected by the local density of states in thin
ferromagnetic films. We employ the antiferromagnetic coupling between Co and Gd
to provide a spontaneous change from parallel to antiparallel alignment of two
Co films. A sharp increase in magnetic damping accompanies the change from
parallel to antiparallel alignment, analogous to resistivity changes in giant
magnetoresistance. | 1003.5344v1 |
2010-05-21 | Quantization of the Damped Harmonic Oscillator Revisited | We return to the description of the damped harmonic oscillator by means of a
closed quantum theory with a general assessment of previous works, in
particular the Bateman-Caldirola-Kanai model and a new model recently proposed
by one of the authors. We show the local equivalence between the two models and
argue that latter has better high energy behavior and is naturally connected to
existing open-quantum-systems approaches. | 1005.4096v1 |
2010-06-09 | Dispersion and damping of two-dimensional dust acoustic waves: Theory and Simulation | A two-dimensional generalized hydrodynamics (GH) model is developed to study
the full spectrum of both longitudinal and transverse dust acoustic waves (DAW)
in strongly coupled complex (dusty) plasmas, with memory-function-formalism
being implemented to enforce high-frequency sum rules. Results are compared
with earlier theories (such as quasi-localized charge approximation and its
extended version) and with a self-consistent Brownian dynamics simulation. It
is found that the GH approach provides good account, not only for dispersion
relations, but also for damping rates of the DAW modes in a wide range of
coupling strengths, an issue hitherto not fully addressed for dusty plasmas. | 1006.1799v1 |
2010-07-01 | Finite time extinction by nonlinear damping for Schrodinger equation | We consider the Schrodinger equation on a compact manifold, in the presence
of a nonlinear damping term, which is homogeneous and sublinear. For initial
data in the energy space, we construct a weak solution, defined for all
positive time, which is shown to be unique. In the one-dimensional case, we
show that it becomes zero in finite time. In the two and three-dimensional
cases, we prove the same result under the assumption of extra regularity on the
initial datum. | 1007.0077v2 |
2010-07-07 | Spin drag Hall effect in a rotating Bose mixture | We show that in a rotating two-component Bose mixture, the spin drag between
the two different spin species shows a Hall effect. This spin drag Hall effect
can be observed experimentally by studying the out-of-phase dipole mode of the
mixture. We determine the damping of this mode due to spin drag as a function
of temperature. We find that due to Bose stimulation there is a strong
enhancement of the damping for temperatures close to the critical temperature
for Bose-Einstein condensation. | 1007.1088v1 |
2010-08-30 | Synthesis of electrical networks interconnecting PZT actuators to damp mechanical vibrations | This paper proves that it is possible to damp mechanical vibrations of some
beam frames by means of piezoelectric actuators interconnected via passive
networks. We create a kind of electromechanical wave guide where the electrical
velocity group equals the mechanical one thus enabling an electromechanical
energy transfer. Numerical simulations are presented which prove the technical
feasibility of proposed device | 1008.5112v1 |
2010-10-05 | Damping of dHvA oscillations and vortex-lattice disorder in the peak-effect region of strong type-II superconductors | The phenomenon of magnetic quantum oscillations in the superconducting state
poses several questions that still defy satisfactory answers. A key
controversial issue concerns the additional damping observed in the vortex
state. Here, we show results of \mu SR, dHvA, and SQUID magnetization
measurements on borocarbide superconductors, indicating that a sharp drop
observed in the dHvA amplitude just below H_{c2} is correlated with enhanced
disorder of the vortex lattice in the peak-effect region, which significantly
enhances quasiparticle scattering by the pair potential. | 1010.0929v1 |
2010-10-21 | Classical behavior of strongly correlated Fermi systems near a quantum critical point. Transport properties | The low-temperature kinetics of the strongly correlated electron liquid
inhabiting a solid is analyzed. It is demonstrated that a softly damped branch
of transverse zero sound emerges when several bands cross the Fermi surface
simultaneously near a quantum critical point at which the density of states
diverges. Suppression of the damping of this branch occurs due to a mechanism
analogous to that affecting the phonon mode in solids at room temperature,
giving rise to a classical regime of transport at extremely low temperatures in
the strongly correlated Fermi system. | 1010.4547v1 |
2010-10-26 | Open Quantum Systems in Noninertial Frames | We study the effects of decoherence on the entanglement generated by Unruh
effect in noninertial frames by using bit flip, phase damping and depolarizing
channels. It is shown that decoherence strongly influences the initial state
entanglement. The entanglement sudden death can happens irrespective of the
acceleration of the noninertial frame under the action of phase flip and phase
damping channels. It is investigated that an early sudden death happens for
large acceleration under the depolarizing environment. Moreover, the
entanglement increases for a highly decohered phase flip channel. | 1010.5395v1 |
2010-11-17 | Faint Resonantly Scattered Lyman Alpha Emission from the Absorption Troughs of Damped Lyman Alpha Systems at z ~ 3 | We demonstrate that the Lyman alpha emission in the absorption troughs of a
large sample of stacked damped Lyman alpha absorption systems (DLAS) presented
by Rahmani et al (2010) is consistent with the spectral profiles and
luminosities of a recently detected population of faint Lyman alpha emitters at
z ~ 3. This result supports the suggestion that the faint emitters are to be
identified with the host galaxies of DLAS at these redshifts. | 1011.4061v1 |
2010-12-19 | Quantum damping of Fermi-Pasta-Ulam revivals in ultracold Bose gases | We propose an experimental scheme for studying the Fermi-Pasta-Ulam (FPU)
phenomenon in a quantum mechanical regime using ultracold atoms. Specifically,
we suggest and analyze a setup of one-dimensional Bose gases confined into an
optical lattice. The strength of quantum fluctuations is controlled by tuning
the number of atoms per lattice sites (filling factor). By simulating the
real-time dynamics of the Bose-Hubbard model by means of the exact numerical
method of time-evolving block decimation, we investigate the effects of quantum
fluctuations on the FPU recurrence and show that strong quantum fluctuations
cause significant damping of the FPU oscillation. | 1012.4159v1 |
2010-12-21 | Pullback attractors for a singularly nonautonomous plate equation | We consider the family of singularly nonautonomous plate equation with
structural damping \[ u_{tt} + a(t,x)u_{t} + (- \Delta) u_{t} + (-\Delta)^{2} u
+ \lambda u = f(u), \] in a bounded domain $\Omega \subset \R^n$, with Navier
boundary conditions. When the nonlinearity $f$ is dissipative we show that this
problem is globally well posed in $H^2_0(\Omega) \times L^2(\Omega)$ and has a
family of pullback attractors which is upper-semicontinuous under small
perturbations of the damping $a$. | 1012.4749v1 |
2010-12-30 | On rotational solutions for elliptically excited pendulum | The author considers the planar rotational motion of the mathematical
pendulum with its pivot oscillating both vertically and horizontally, so the
trajectory of the pivot is an ellipse close to a circle. The analysis is based
on the exact rotational solutions in the case of circular pivot trajectory and
zero gravity. The conditions for existence and stability of such solutions are
derived. Assuming that the amplitudes of excitations are not small while the
pivot trajectory has small ellipticity the approximate solutions are found both
for high and small linear damping. Comparison between approximate and numerical
solutions is made for different values of the damping parameter. | 1101.0062v1 |
2011-01-28 | Entanglement between two atoms in a damping Jaynes-Cummings model | The entanglement between two atoms in a damping Jaynes-Cummings model is
investigated with different decay coefficients of the atoms from the upper
level to other levels under detuning between the atomic frequency and the
quantized light field frequency. The results indicate that the larger the decay
coefficient is, the more quickly the entanglement decays. The detuning enhances
the entanglement's average value at long times. More importantly, the results
show that the so-called sudden death effect can be avoided by enhancing the
detuning or the decay coefficient. | 1101.5522v1 |
2011-03-10 | Laser-like vibrational instability in rectifying molecular conductors | We study the damping of molecular vibrations due to electron-hole pair
excitations in donor-acceptor(D-A) type molecular rectifiers. At finite voltage
additional non-equilibrium electron-hole pair excitations involving both
electrodes become possible, and contribute to the stimulated emission and
absorption of phonons. We point out a generic mechanism for D-A molecules,
where the stimulated emission can dominate beyond a certain voltage due to
inverted position of the D and A quantum resonances. This leads to
current-driven amplification (negative damping) of the phonons similar to
laser-action. We investigate the effect in realistic molecular rectifier
structures using first principles calculations. | 1103.1990v1 |
2011-03-11 | Spin Transport in Polaronic and Superfluid Fermi Gases | We present measurements of spin transport in ultracold gases of fermionic
lithium-6 in a mixture of two spin states at a Feshbach resonance. In
particular, we study the spin dipole mode, where the two spin components are
displaced from each other against a harmonic restoring force. We prepare a
highly-imbalanced, or polaronic, spin mixture with a spin dipole excitation and
observe strong, unitarity limited damping of the spin dipole mode. In gases
with small spin imbalance, below the Pauli limit for superfluidity, we observe
strongly damped spin flow despite the presence of a superfluid core. | 1103.2337v1 |
2011-03-14 | Tidal Evolution of a Secularly Interacting Planetary System | In a multi-planet system, a gradual change in one planet's semi-major axis
will affect the eccentricities of all the planets, as angular momentum is
distributed via secular interactions. If tidal dissipation in the planet is the
cause of the change in semi-major axis, it also damps that planet's
eccentricity, which in turn also contributes to the evolution of all the
eccentricities. Formulae quantifying the combined effects on the whole system
due to semi-major axis changes, as well as eccentricity damping, are derived
here for a two-planet system. The CoRoT 7 system is considered as an example. | 1103.2794v1 |
2011-03-30 | Damping in quantum love affairs | In a series of recent papers we have used an operatorial technique to
describe stock markets and, in a different context, {\em love affairs} and
their time evolutions. The strategy proposed so far does not allow any dumping
effect. In this short note we show how, within the same framework, a strictly
non periodic or quasi-periodic effect can be introduced in the model by
describing in some details a linear Alice-Bob love relation with damping. | 1103.5907v1 |
2011-04-03 | Spatially confined Bloch oscillations in semiconductor superlattices | In a semiconductor superlattice with long scattering times, damping of Bloch
oscillations due to scattering is so small that convective nonlinearities may
compensate it and Bloch oscillations persist even in the hydrodynamic regime.
In this case, numerical solutions show that there are stable Bloch oscillations
confined to a region near the collector with inhomogeneous field, charge,
current density and energy density profiles. These Bloch oscillations disappear
when damping due to inelastic collisions becomes sufficiently strong. | 1104.0429v2 |
2011-04-06 | Observed damping of the slow magnetoacoustic mode | Spectroscopic and stereoscopic imaging observations of slow magnetoacoustic
wave propagation within a coronal loop are investigated to determine the decay
length scale of the slow magnetoacoustic mode in three dimensions and the
density profile within the loop system. The slow wave is found to have an
e-folding decay length scale of $20,000^{+4000}_{-3000}$km with a uniform
density profile along the loop base. These observations place quantitive
constraints on the modelling of wave propagation within coronal loops.
Theoretical forward modelling suggests that magnetic field line divergence is
the dominant damping factor and thermal conduction is insufficient, given the
observed parameters of the coronal loop temperature, density and wave mode
period. | 1104.1100v1 |
2011-04-17 | Stochastic Wave Equations with Nonlinear Damping and Source Terms | In this paper, we discuss an initial boundary value problem for the
stochastic wave equation involving the nonlinear damping term $|u_t|^{q-2}u_t$
and a source term of the type $|u|^{p-2}u$. We firstly establish the local
existence and uniqueness of solution by the Galerkin approximation method and
show that the solution is global for $q\geq p$. Secondly, by an appropriate
energy inequality, the local solution of the stochastic equations will blow up
with positive probability or explosive in energy sense for $p>q$. | 1104.3279v2 |
2011-05-07 | Cooperative scattering measurement of coherence in a spatially modulated Bose gas | Correlations of a Bose gas released from an optical lattice are measured
using superradiant scattering. Conditions are chosen so that after initial
incident light pumping at the Bragg angle for diffraction, due to matter wave
amplification and mode competition, superradiant scattering into the Bragg
diffracted mode is preponderant. A temporal analysis of the superradiant
scattering gain reveals periodical oscillations and damping due to the initial
lack of coherence between lattice sites. Such damping is used for
characterizing first order spatial correlations in our system with a precision
of one lattice period. | 1105.1425v1 |
2011-06-09 | Hamiltonian of mean force for damped quantum systems | We consider a quantum system linearly coupled to a reservoir of harmonic
oscillators. For finite coupling strengths, the stationary distribution of the
damped system is not of the Gibbs form, in contrast to standard thermodynamics.
With the help of the quantum Hamiltonian of mean force, we quantify this
deviation exactly for a harmonic oscillator and provide approximations in the
limit of high and low temperatures, and weak and strong couplings. Moreover, in
the semiclassical regime, we use the quantum Smoluchowski equation to obtain
results valid for any potential. We, finally, give a physical interpretation of
the deviation in terms of the initial system-reservoir coupling. | 1106.1775v1 |
2011-06-17 | Current effect on magnetization oscillations in a ferromagnet - antiferromagnet junction | Spin-polarized current effect is studied on the static and dynamic
magnetization of the antiferromagnet in a ferromagnet - antiferromagnet
junction. The macrospin approximation is generalized to antiferromagnets.
Canted antiferromagnetic configuration and resulting magnetic moment are
induced by an external magnetic field. The resonance frequency and damping are
calculated, as well as the threshold current density corresponding to
instability appearance. A possibility is shown of generating low-damping
magnetization oscillations in terahertz range. The fluctuation effect is
discussed on the canted antiferromagnetic configuration. | 1106.3519v1 |
2011-06-23 | Dissipation evidence for the quantum damped harmonic oscillator via pseudo-bosons | It is known that a self-adjoint, time-independent hamiltonian can be defined
for the quantum damped harmonic oscillator. We show here that the two vacua
naturally associated to this operator, when expressed in terms of
pseudo-bosonic lowering and raising operators, appear to be non
square-integrable. This fact is interpreted as the evidence of the dissipation
effect of the classical oscillator at a purely quantum level. | 1106.4638v1 |
2011-07-15 | Aspects of General Relativity: Pseudo-Finsler extensions, Quasi-normal frequencies and Multiplication of tensorial distributions | This thesis is based on three different projects, all of them are directly
linked to the classical general theory of relativity, but they might have
consequences for quantum gravity as well. The first chapter deals with
pseudo-Finsler geometric extensions of the classical theory, these being ways
of naturally representing high-energy Lorentz symmetry violations. The second
chapter deals with the problem of highly damped quasi-normal modes related to
different types of black hole spacetimes. Besides the astrophysical meaning of
the quasi-normal modes, there are conjectures about the link between the highly
damped modes and black hole thermodynamics. The third chapter is related to the
topic of multiplication of tensorial distributions. | 1107.2978v1 |
2011-08-08 | Synchrotron radiation damping, intrabeam scattering and beam-beam simulations for HE-LHC | The proposed High-Energy LHC project presents an unusual combination of
strong synchrotron radiation (SR) damping and intrabeam scattering (IBS), which
is not seen in present-day hadron colliders. The subject of investigation
reported in this paper was the simulation of beam-beam effect for the HE-LHC
parameters. Parameters of SR and IBS are calculated, and the luminosity
evolution is simulated in the absence of beambeam interaction. Then, a
weak-strong numerical simulation is used to predict the effect of beam-beam
interaction on particle losses and emittance evolution. | 1108.1644v1 |
2011-09-08 | On the attenuation coefficient of monomode periodic waveguides | It is widely accepted that, on ensemble average, the transmission T of guided
modes decays exponentially with the waveguide length L due to small
imperfections, leading to the important figure of merit defined as the
attenuation-rate coefficient alpha = -<ln(T)>/L. In this letter, we evidence
that the exponential-damping law is not valid in general for periodic monomode
waveguides, especially as the group velocity decreases. This result that
contradicts common beliefs and experimental practices aiming at measuring alpha
is supported by a theoretical study of light transport in the limit of very
small imperfections, and by numerical results obtained for two waveguide
geometries that offer contrasted damping behaviours. | 1109.1642v1 |
2011-09-09 | Delocalization of slowly damped eigenmodes on Anosov manifolds | We look at the properties of high frequency eigenmodes for the damped wave
equation on a compact manifold with an Anosov geodesic flow. We study
eigenmodes with spectral parameters which are asymptotically close enough to
the real axis. We prove that such modes cannot be completely localized on
subsets satisfying a condition of negative topological pressure. As an
application, one can deduce the existence of a "strip" of logarithmic size
without eigenvalues below the real axis under this dynamical assumption on the
set of undamped trajectories. | 1109.1909v2 |
2011-10-18 | Life times and chirality of spin-waves in antiferromagnetic and ferromagnetic FeRh: time depedent density functional theory perspective | The study of the spin excitations in antiferromagnetic (AFM) and
ferromagnetic (FM) phases of FeRh is reported. We demonstrate that although the
Fe atomic moments are well defined there is a number of important phenomena
absent in the Heisenberg description: Landau damping of spin waves, large Rh
moments induced by the AFM magnons, the formation of the optical magnons
terminated by Stoner excitations. We relate the properties of the spin-wave
damping to the features of the Stoner continuum and compare the chirality of
the spin excitations in AFM, FM and paramagnetic (PM) systems. | 1110.3913v1 |
2011-10-21 | Environment-Assisted Error Correction of Single-Qubit Phase Damping | Open quantum system dynamics of random unitary type may in principle be fully
undone. Closely following the scheme of environment-assisted error correction
proposed by Gregoratti and Werner [M. Gregoratti and R. F. Werner, J. Mod. Opt.
50(6), 915-933 (2003)], we explicitly carry out all steps needed to invert a
phase-damping error on a single qubit. Furthermore, we extend the scheme to a
mixed-state environment. Surprisingly, we find cases for which the uncorrected
state is closer to the desired state than any of the corrected ones. | 1110.4806v1 |
2011-11-01 | Damping of tensor modes in inflation | We discuss the damping of tensor modes due to anisotropic stress in
inflation. The effect is negligible in standard inflation and may be
significantly large in inflation models that involve drastic production of
free-streaming particles. | 1111.0295v3 |
2011-11-04 | Global uniform asymptotic stabilization and k-exponential trajectory tracking of underactuated surface ships with non-diagonal inertia/damping matrices | In this work, we investigate the state stabilization and trajectory tracking
problems of underactuated surface ships with full state model of having
non-diagonal inertia and damping matrices. By combining the novel state
transformations, the direct Lyapunov approach, and the nonlinear time-varying
tools, the stabilization and the trajectory tracking controllers are developed
respectively guaranteeing global uniform asymptotic convergence of the state to
the desired set point and global exponential convergence to the desired
reference trajectory via mild persistent exciting conditions. Simulation
examples are given to illustrate the effectiveness of the proposed control
schemes. | 1111.1029v1 |
2011-11-15 | Finite Size Effects of the Surface States in a Lattice Model of Topological Insulator | Energy gap and wave function in thin films of topological insulator is
studied, based on tight--binding model. It is revealed that thickness
dependence of the magnitude of energy gap is composed of damping and
oscillation. The damped behavior originates from the presence of gapless
surface Dirac cone in the infinite thickness limit. On the other hand, the
oscillatory behavior stems from electronic properties in the thin thickness
limit. | 1111.3528v2 |
2011-11-23 | Pumping the eccentricity of exoplanets by tidal effect | Planets close to their host stars are believed to undergo significant tidal
interactions, leading to a progressive damping of the orbital eccentricity.
Here we show that, when the orbit of the planet is excited by an outer
companion, tidal effects combined with gravitational interactions may give rise
to a secular increasing drift on the eccentricity. As long as this secular
drift counterbalances the damping effect, the eccentricity can increase to high
values. This mechanism may explain why some of the moderate close-in exoplanets
are observed with substantial eccentricity values. | 1111.5486v1 |
2011-11-30 | Shear viscosity and damping of collective modes in a two-dimensional Fermi gas | We compute the shear viscosity of a two dimensional Fermi gas interacting via
a short range potential with scattering length $a_{2d}$ in kinetic theory. We
find that kinetic theory predicts that the shear viscosity to entropy density
ratio of a strongly interacting two dimensional gas is comparable to that of
the three dimensional unitary gas. We use our results to compute the damping of
collective modes in a trapped Fermi gas, and compare to experimental data
recently obtained in E. Vogt et al., arXiv:1111.1173. | 1111.7242v2 |
2011-12-13 | Drastically suppressing the error of ballistic readout of qubits | The thermal jitter of transmission of magnetic flux quanta in long Josephson
junctions is studied. While for large-to-critical damping and small values of
bias current the physically obvious dependence of the jitter versus length
$\sigma\sim\sqrt{L}$ is confirmed, for small damping starting from the
experimentally relevant $\alpha=0.03$ and below strong deviation from
$\sigma\sim\sqrt{L}$ is observed, up to nearly complete independence of the
jitter versus length, which is exciting from fundamental point of view, but
also intriguing from the point of view of possible applications. | 1112.2805v1 |
2011-12-15 | Diffusion-Induced Oscillations of Extended Defects | From a simple model for the driven motion of a planar interface under the
influence of a diffusion field we derive a damped nonlinear oscillator equation
for the interface position. Inside an unstable regime, where the damping term
is negative, we find limit-cycle solutions, describing an oscillatory
propagation of the interface. In case of a growing solidification front this
offers a transparent scenario for the formation of solute bands in binary
alloys, and, taking into account the Mullins-Sekerka instability, of banded
structures. | 1112.3669v1 |
2011-12-31 | Stability of cnoidal waves in the parametrically driven nonlinear Schrödinger equation | The parametrically driven, damped nonlinear Schr\"odinger equation has two
cn- and two dn-wave solutions. We show that one pair of the cn and dn solutions
is unstable for any combination of the driver's strength, dissipation
coefficient and spatial period of the wave; this instability is against
periodic perturbations. The second dn-wave solution is shown to be unstable
against antiperiodic perturbations --- in a certain region of the parameter
space. We also consider quasiperiodic perturbations with long modulation
wavelength, in the limit where the driving strength is only weakly exceeding
the damping coefficient. | 1201.0263v1 |
2012-01-03 | Dynamics of DNA Bubble in Viscous Medium | The damping effect to the DNA bubble is investigated within the
Peyrard-Bishop model. In the continuum limit, the dynamics of the bubble of DNA
is described by the damped nonlinear Schrodinger equation and studied by means
of variational method. It is shown that the propagation of solitary wave
pattern is not vanishing in a non-viscous system. Inversely, the solitary wave
vanishes soon as the viscous force is introduced. | 1201.0689v2 |
2012-01-18 | Magnetohydrodynamic Waves in Partially Ionized Prominence Plasmas | Prominences or filaments are cool clouds of partially ionized plasma living
in the solar corona. Ground- and space-based observations have confirmed the
presence of oscillatory motions in prominences and they have been interpreted
in terms of magnetohydrodynamic (MHD) waves. Existing observational evidence
points out that these oscillatory motions are damped in short spatial and
temporal scales by some still not well known physical mechanism(s). Since
prominences are partially ionized plasmas, a potential mechanism able to damp
these oscillations could be ion-neutral collisions. Here, we will review the
work done on the effects of partial ionization on MHD waves in prominence
plasmas. | 1201.3752v1 |
2012-01-26 | Inhomogeneous spin diffusion in traps with cold atoms | The spin diffusion and damped oscillations are studied in the collision of
two spin polarized clouds of cold atoms with resonant interactions. The strong
density dependence of the diffusion coefficient leads to inhomogeneous spin
diffusion that changes from central to surface spin flow as the temperature
increases. The inhomogeneity and the smaller finite trap size significantly
reduce the spin diffusion rate at low temperatures. The resulting spin
diffusion rates, spin drag and initial damped oscillations are compatible with
measurements at low to high temperatures for resonant attractive interactions
but are incompatible with a metastable ferromagnetic phase. | 1201.5526v2 |
2012-01-30 | Volatility-dependent damping of evaporation-driven Bénard-Marangoni instability | The interface between a pure liquid and its vapor is usually close to
saturation temperature, hence strongly hindering any thermocapillary flow. In
contrast, when the gas phase contains an inert gas such as air,
surface-tension-driven convection is easily observed. We here reconcile these
two facts by studying the corresponding crossover experimentally, as a function
of a new dimensionless number quantifying the degree of damping of interfacial
temperature fluctuations. Critical conditions are in convincing agreement with
a simple nonlocal one-sided model, in quite a range of evaporation rates. | 1201.6334v1 |
2012-03-03 | Necessary and sufficient conditions of freezing phenomena of quantum discord under phase damping | We investigate the freezing phenomenon of quantum discord occurring in phase
damping noise processes. By relating the expression of the time variation of
the discord to the convex function of relative entropy, we obtain the necessary
and sufficient conditions of the phenomenon for standard Bell-diagonal states.
These conditions are applicable also to the phenomenon occurring in a
non-Markovian dephasing process. Moreover, we show that the same condition and
phenomenon coincide in a new sort of Bell-diagonal states beyond the standard
form. | 1203.0650v3 |
2012-03-06 | Universal anomalous diffusion of weakly damped particles | We show that anomalous diffusion arises in two different models for the
motion of randomly forced and weakly damped particles: one is a generalisation
of the Ornstein-Uhlenbeck process with a random force which depends on position
as well as time, the other is a generalisation of the Chandrasekhar-Rosenbluth
model of stellar dynamics, encompassing non-Coulombic potentials. We show that
both models exhibit anomalous diffusion of position $x$ and momentum $p$ with
the same exponents: $<x^2> \sim C_x t^2$ and $<p^2> \sim C_p t^{2/5}$. We are
able to determine the prefactors $C_x$, $C_p$ analytically. | 1203.1354v1 |
2012-03-13 | Monopoles in ferromagnetic metals | The aim of this short review is to give an introduction to monopoles and to
present theoretical derivation of two particular monopoles in ferromagnetic
metals, a hedgehog monopole and a spin damping monopole. Spin damping monopoles
can be generated in simple systems such as a junction of a ferromagnet and a
heavy element with strong spin-orbit interaction such as Pt. This monopole is
essential in coupling electronics with magnetism, and is thus expected to play
an essential role in spintronics. | 1203.2709v1 |
2012-03-16 | Report from KEK (High gradient study results from Nextef) | Most up-to-date high gradient test of the CLIC prototype structures as of
September 2011 is described in this report. The "T24" undamped structure showed
fast processing time, still-decreasing breakdown rate and its breakdown rate
was estimated to be as low as the CLIC requirement. The "TD24" damped structure
showed not so excellent high gradient performance as undamped "T24" but the
characteristics was much improved than the damped "TD18" structure with higher
magnetic field. Further R&D is needed and we present some of the present
efforts at KEK. | 1203.3626v1 |
2012-03-30 | Energy decay rates for solutions of the wave equation with linear damping in exterior domain | In this paper we study the behavior of the energy of solutions of the wave
equation with localized damping in exterior domain. We assume that the damper
is positive at infinity. Under the Geometric Control Condition of Bardos et al
(1992), we prove that: 1) The total energy decay like O(1/t) and L^2-norm is
bounded for the solutions with initial data in (H_{0}^{1},L^{2}). 2) The total
energy and the square of the L^2-norm, repectively, decay like O(1/t^{2}) and
O(1/t) for a kind of the weighted initial data. | 1203.6780v4 |
2012-04-03 | Modification in Silling's Peridynamic Formulation of Elasticity Theory for Discontinuities and Long-Range Forces | We suggest modified version of Silling's peridynamic equation of motion
within the framework of Silling's peridynamics formulation (J. Mech. Phys.
Solids {\bf 48}, pp.175-209, 2000) of elasticity theory. The modified equation
contains an additional damping force term. This term can eliminate artificial
oscillations in displacement field at large values of time as predicted by
Silling's peridynamic equation. | 1204.0612v2 |
2012-04-06 | Experimental signatures of the quantum-classical transition in a nanomechanical oscillator modeled as a damped driven double-well problem | We demonstrate robust and reliable signatures for the transition from quantum
to classical behavior in the position probability distribution of a damped
double-well system using the Qunatum State Diffusion approach to open quantum
systems. We argue that these signatures are within experimental reach, for
example in a doubly-clamped nanomechanical beam. | 1204.1397v1 |
2012-05-31 | The impact of fill patterns on the fast ion instability in the ILC damping ring | The ions produced via collisional ionization of the residual gas molecules in
vacuum pipe with the circulating electron beam have deleterious effect on the
beam properties and may become a limiting factor for the machine's performance.
For the electron damping ring of the International Linear Collider (ILC), the
ion instability is noticeable due to the ultra-low beam emittance with many
bunches operation. In this paper, the different beam fill patterns are
investigated and their effects on the fast ion instability are discussed. The
simulations show that the mini train fill patterns can reduce the growth of the
fast ion instability significantly. | 1205.6977v1 |
2012-06-11 | Damping and decoherence of Fock states in a nanomechanical resonator due to two level systems | We numerically investigate the decay of initial quantum Fock states and their
superpositions for a mechanical resonator mode coupled to an environment
comprising interacting, damped tunneling two level system (TLS) defects. The
cases of one, three, and six near resonant, interacting TLS's are considered in
turn and it is found that the resonator displays Ohmic bath like decay behavior
with as few as three TLS's. | 1206.2200v1 |
2012-07-13 | Magnetic relaxation in bilayers of yttrium iron garnet/platinum due to the dynamic coupling at the interface | We show that in ferromagnetic (FM)/normal metal (NM) bilayers the dynamic
coupling at the interface transfers an additional magnetic relaxation from the
heavily damped motion of the conduction electron spins in the NM layer to the
FM spins. While the FM relaxation rates due to two-magnon scattering and spin
pumping decrease rapidly with increasing FM film thickness, the damping due to
the dynamic coupling does not depend on the FM film thickness. The proposed
mechanism explains the very large broadening of ferromagnetic resonance lines
in thick films of yttrium iron garnet after deposition of a Pt layer. | 1207.3330v1 |
2012-07-23 | Quantum interference induced by initial system-environment correlations | We investigate the quantum interference induced by a relative phase in the
correlated initial state of a system which consists in a two-level atom
interacting with a damped mode of the radiation field. We show that the initial
relative phase has significant effects on both the evolution of the atomic
excited-state population and the information flow between the atom and the
reservoir, as quantified by the trace distance. Furthermore, by considering two
two-level atoms interacting with a common damped mode of the radiation field,
we highlight how initial relative phases can affect the subsequent entanglement
dynamics. | 1207.5474v1 |
2012-07-31 | An analytic description of the damping of gravitational waves by free streaming neutrinos | We provide an analytic solution to the general wavelength
integro-differential equation describing the damping of tensor modes of
gravitational waves due to free streaming neutrinos in the early universe. Our
result is expressed as a series of spherical Bessel functions whose
coefficients are functions of the reduced wave number $Q$. | 1207.7285v4 |
2012-08-21 | Dancing bunches as Van Kampen modes | Van Kampen modes are eigen-modes of Jeans-Vlasov equation. Their spectrum
consists of continuous and, possibly, discrete parts. Onset of a discrete van
Kampen mode means emergence of a coherent mode without any Landau damping;
thus, even a tiny couple-bunch wake is sufficient to drive instability.
Longitudinal instabilities observed at Tevatron, RHIC and SPS can be explained
as loss of Landau damping (LLD), which is shown here to happen at fairly low
impedances. For repulsive wakes and single-harmonic RF, LLD is found to be
extremely sensitive to steepness of the bunch distribution function at small
amplitudes. Based on that, a method of beam stabilization is suggested. | 1208.4338v1 |
2012-08-22 | Polynomial stabilization of some dissipative hyperbolic systems | We study the problem of stabilization for the acoustic system with a
spatially distributed damping. Imposing various hypotheses on the structural
properties of the damping term, we identify either exponential or polynomial
decay of solutions with growing time. Expo- nential decay rate is shown by
means of a time domain approach, reducing the problem to an observability
inequality to be verified for solutions of the associated conservative problem.
In addition, we show a polynomial stabilization result, where the proof uses a
frequency domain method and combines a contradiction argument with the
multiplier technique to carry out a special analysis for the resolvent. | 1208.4485v1 |
2012-12-06 | The physics of business cycles and inflation | We analyse four consecutive cycles observed in the USA for employment and
inflation. They are driven by three oil price shocks and an intended interest
rate shock. Non-linear coupling between the rate equations for consumer
products as prey and consumers as predators provides the required instability,
but its natural damping is too high for spontaneous cycles. Extending the
Lotka-Volterra equations with a small term for collective anticipation yields a
second analytic solution without damping. It predicts the base period, phase
shifts, and the sensitivity to shocks for all six cyclic variables correctly. | 1212.1282v1 |
2012-12-13 | CMB Distortions from Damping of Acoustic Waves Produced by Cosmic Strings | We study diffusion damping of acoustic waves in the photon-baryon fluid due
to cosmic strings, and calculate the induced $\mu$- and $y$-type spectral
distortions of the cosmic microwave background. For cosmic strings with tension
within current bounds, their contribution to the spectral distortions is
subdominant compared to the distortions from primordial density perturbations. | 1212.3283v2 |
2013-01-21 | Asymptotic parabolicity for strongly damped wave equations | For $S$ a positive selfadjoint operator on a Hilbert space, \[
\frac{d^2u}{dt}(t) + 2 F(S)\frac{du}{dt}(t) + S^2u(t)=0 \] describes a class of
wave equations with strong friction or damping if $F$ is a positive Borel
function. Under suitable hypotheses, it is shown that \[ u(t)=v(t)+ w(t) \]
where $v$ satisfies \[ 2F(S)\frac{dv}{dt}(t)+ S^2v(t)=0 \] and \[
\frac{w(t)}{\|v(t)\|} \rightarrow 0, \; \text{as} \; t \rightarrow +\infty. \]
The required initial condition $v(0)$ is given in a canonical way in terms of
$u(0)$, $u'(0)$. | 1301.4979v1 |
2013-02-04 | Gravity waves on the surface of topological superfluid 3He-B | We have observed waves on the free surface of 3He-B sample at temperatures
below 0.2mK. The waves are excited by vibrations of the cryostat and detected
by coupling the surface to the Bose-Einstein condensate of magnon
quasiparticles in the superfluid. The two lowest gravity-wave modes in our
cylindrical container are identified. Damping of the waves increases with
temperature linearly with the density of thermal quasiparticles, as expected.
Additionally finite damping of the waves in the zero-temperature limit and
enhancement of magnetic relaxation of magnon condensates by the surface waves
are observed. We discuss whether the latter effects may be related to Majorana
fermions bound to the surface of the topological superfluid. | 1302.0764v1 |
2013-02-12 | On the fractional damped oscillators and fractional forced oscillators | In this paper, we use the fractional calculus to discuss the fractional
mechanics, where the time derivative is replaced with the fractional derivative
of order $\nu$. We deal with the motion of a body in a resisting medium where
the retarding force is assumed to be proportional to the fractional velocity
which is obtained by acting the fractional derivative on the position. The
fractional harmonic oscillator problem, fractional damped oscillator problem
and fractional forced oscillator problem are also studied. | 1302.2847v1 |
2013-02-25 | Optimal damping algorithm for unrestricted Hartree-Fock calculations | We have developed a couple of optimal damping algorithms (ODAs) for
unrestricted Hartree-Fock (UHF) calculations of open-shell molecular systems. A
series of equations were derived for both concurrent and alternate
constructions of alpha- and beta-Fock matrices in the integral-direct
self-consistent-field (SCF) procedure. Several test calculations were performed
to check the convergence behaviors. It was shown that the concurrent algorithm
provides better performance than does the alternate one. | 1302.6099v1 |
2013-03-08 | Entanglement of Open Quantum Systems in Noninertial Frames | We study the effects of decoherence on the entanglement generated by Unruh
effect in accelerated frames by using various combinations of an amplitude
damping channel, a phase damping channel and a depolarizing channel in the form
of multilocal and collective environments. Using concurrence as entanglement
quantifier, we show that the occurrence of entanglement sudden death (ESD)
depends on different combinations of the channels. The ESD can be avoided under
a particular configuration of the channels. We show that the channels can be
used to distinguish between a moving and a stationary frame. | 1303.2034v1 |
2013-03-21 | Glued trees algorithm under phase damping | We study the behaviour of the glued trees algorithm described by Childs et
al. in [STOC `03, Proc. 35th ACM Symposium on Theory of Computing (2004) 59]
under decoherence. We consider a discrete time reformulation of the continuous
time quantum walk protocol and apply a phase damping channel to the coin state,
investigating the effect of such a mechanism on the probability of the walker
appearing on the target vertex of the graph. We pay particular attention to any
potential advantage coming from the use of weak decoherence for the spreading
of the walk across the glued trees graph. | 1303.5319v2 |
2013-05-13 | Guaranteed convergence of the Kohn-Sham equations | A sufficiently damped iteration of the Kohn-Sham equations with the exact
functional is proven to always converge to the true ground-state density,
regardless of the initial density or the strength of electron correlation, for
finite Coulomb systems. We numerically implement the exact functional for
one-dimensional continuum systems and demonstrate convergence of the damped KS
algorithm. More strongly correlated systems converge more slowly. | 1305.2967v2 |
2013-06-25 | Decoherence effects in the quantum qubit flip game using Markovian approximation | We are considering a quantum version of the penny flip game, whose
implementation is influenced by the environment that causes decoherence of the
system. In order to model the decoherence we assume Markovian approximation of
open quantum system dynamics. We focus our attention on the phase damping,
amplitude damping and amplitude raising channels. Our results show that the
Pauli strategy is no longer a Nash equilibrium under decoherence. We attempt to
optimize the players' control pulses in the aforementioned setup to allow them
to achieve higher probability of winning the game compared to the Pauli
strategy. | 1306.5957v1 |
2013-07-06 | The 3-dimensional oscillon equation | On a bounded three-dimensional smooth domain, we consider the generalized
oscillon equation with Dirichlet boundary conditions, with time-dependent
damping and time-dependent squared speed of propagation. Under structural
assumptions on the damping and the speed of propagation, which include the
relevant physical case of reheating phase of inflation, we establish the
existence of a pullback global attractor of optimal regularity, and
finite-dimensionality of the kernel sections. | 1307.1777v1 |
2013-07-17 | Functional inequalities on path space over a non-compact Riemannian manifold | We prove the existence of the O-U Dirichlet form and the damped O-U Dirichlet
form on path space over a general non-compact Riemannian manifold which is
complete and stochastically complete. We show a weighted log-Sobolev inequality
for the O-U Dirichlet form and the (standard) log-Sobolev inequality for the
damped O-U Dirichlet form. In particular, the Poincar\'e inequality (and the
super Poincar\'e inequality) can be established for the O-U Dirichlet form on
path space over a class of Riemannian manifolds with unbounded Ricci
curvatures. Moreover, we construct a large class of quasi-regular local
Dirichlet forms with unbounded random diffusion coefficients on the path space
over a general non-compact manifold. | 1307.4482v2 |
2013-08-30 | A conservative, skew-symmetric Finite Difference Scheme for the compressible Navier--Stokes Equations | We present a fully conservative, skew-symmetric finite difference scheme on
transformed grids. The skew-symmetry preserves the kinetic energy by first
principles, simultaneously avoiding a central instability mechanism and
numerical damping. In contrast to other skew-symmetric schemes no special
averaging procedures are needed. Instead, the scheme builds purely on
point-wise operations and derivatives. Any explicit and central derivative can
be used, permitting high order and great freedom to optimize the scheme
otherwise. This also allows the simple adaption of existing finite difference
schemes to improve their stability and damping properties. | 1308.6672v1 |
2013-09-09 | Classical and quantum capacities of a fully correlated amplitude damping channel | We study information transmission over a fully correlated amplitude damping
channel acting on two qubits. We derive the single-shot classical channel
capacity and show that entanglement is needed to achieve the channel best
performance. We discuss the degradability properties of the channel and
evaluate the quantum capacity for any value of the noise parameter. We finally
compute the entanglement-assisted classical channel capacity. | 1309.2219v3 |
2013-09-13 | Polarization hydrodynamics in a one-dimensional polariton condensate | We study the hydrodynamics of a nonresonantly-pumped polariton condensate in
a quasi-one-dimensional quantum wire taking into account the spin degree of
freedom. We clarify the relevance of the Landau criterion for superfluidity in
this dissipative two-component system. Two Cherenkov-like critical velocities
are identified corresponding to the opening of different channels of radiation:
one of (damped) density fluctuations and another of (weakly damped)
polarization fluctuations. We determine the drag force exerted onto an external
obstacle and propose experimentally measurable consequences of the specific
features of the fluctuations of polarization. | 1309.3494v1 |
2013-09-26 | Imperfect geometric control and overdamping for the damped wave equation | We consider the damped wave equation on a manifold with imperfect geometric
control. We show the sub-exponential energy decay estimate in
\cite{Chr-NC-erratum} is optimal in the case of one hyperbolic periodic
geodesic. We show if the equation is overdamped, then the energy decays
exponentially. Finally we show if the equation is overdamped but geometric
control fails for one hyperbolic periodic geodesic, then nevertheless the
energy decays exponentially. | 1309.6967v1 |
2013-10-01 | Scalar filed evolution and area spectrum for Lovelock-AdS black holes | We study the modes of evolution of massless scalar fields in the
asymptotically AdS spacetime surrounding maximally symmetric black holes of
large and intermediate size in the Lovelock model. It is observed that all
modes are purely damped at higher orders. Also, the rate of damping is seen to
be independent of order at higher dimensions. The asymptotic form of these
frequencies for the case of large black holes is found analytically. Finally,
the area spectrum for such black holes is found from these asymptotic modes. | 1310.0159v2 |
2013-10-16 | Perturbative quantum damping of cosmological expansion | Perturbative quantum gravity in the framework of the Schwinger-Keldysh
formalism is applied to compute lowest-order corrections to the actual
expansion of the Universe described in terms of the spatially flat
Friedman-Lematre-Robertson-Walker solution. The classical metric is
approximated by a third order polynomial perturbation around the Minkowski
metric. It is shown that the quantum contribution to the classical expansion,
although extremely small, has damping properties (quantum friction), i.e. it
slows down the expansion. | 1310.4308v2 |
2013-10-27 | Loss of non-Gaussianity for damped photon-subtracted thermal states | We investigate non-Gaussianity properties for a set of classical one-mode
states obtained by subtracting photons from a thermal state. Three
distance-type degrees of non-Gaussianity used for these states are shown to
have a monotonic behaviour with respect to their mean photon number. Decaying
of their non-Gaussianity under damping is found to be consistently described by
the distance-type measures considered here. We also compare the dissipative
evolution of non-Gaussianity when starting from $M$-photon-subtracted and
$M$-photon-added thermal states | 1310.7229v1 |
2013-10-27 | Landau damping effects and evolutions of energy spread in small isochronous ring | This paper presents the Landau damping effects on the microwave instability
of a coasting long bunch in an isochronous ring due to finite energy spread and
emittance. Our two-dimensional (2D) dispersion relation gives more accurate
predictions of the microwave instability growth rates of short-wavelength
perturbations than the conventional 1D formula. The long-term evolution of
energy spread is also studied by measurements and simulations. | 1310.7253v3 |
2013-10-28 | Robustness of multiparticle entanglement: specific entanglement classes and random states | We investigate the robustness of genuine multiparticle entanglement under
decoherence. We consider different kinds of entangled three- and four-qubit
states as well as random pure states. For amplitude damping noise, we find that
the W-type states are most robust, while other states are not more robust than
generic states. For phase damping noise the GHZ state is the most robust state,
and for depolarizing noise several states are significantly more robust than
random states. | 1310.7336v2 |
2013-12-16 | Local Energy Decay for the Damped Wave Equation | We prove local energy decay for the damped wave equation on R^d. The problem
which we consider is given by a long range metric perturbation of the Euclidean
Laplacian with a short range absorption index. Under a geometric control
assumption on the dissipation we obtain an almost optimal polynomial decay for
the energy in suitable weighted spaces. The proof relies on uniform estimates
for the corresponding "resolvent", both for low and high frequencies. These
estimates are given by an improved dissipative version of Mourre's commutators
method. | 1312.4483v1 |
2013-12-23 | Photonic tuning of quasi-particle decay in a superfluid | We show that the damping rate of elementary excitations of hybrid systems
close to a phase transition can undergo a remarkable resonance like enhancement
before mode softening takes place. In particular, we consider the friction of a
collective density wave in a homogeneous superfluid of weakly interacting
bosonic atoms coupled to the electromagnetic field of a single mode optical
resonator. Here the Beliaev damping can thus be controlled by an external laser
drive and be enhanced by several orders of magnitude. | 1312.6719v1 |
2014-02-11 | New approach for Damping in a squeezed bath and its time evolution through Complete Class of Gaussian Quasi-distributions | By virtue of the thermal entangled states representation of density operator
and using dissipative interaction picture we solve the master equation of a
driven damped harmonic oscillator in a squeezed bath. We show that the
essential part of the dynamics can be expressed by the convolution of initial
Wigner function with a special kind of normalized Gaussian in phase space and
relate the dynamics with the change of Gaussian ordering of density operator. | 1402.2545v1 |
2014-02-11 | New approach for solving master equations of density operator for the Jaynes Cummings Model with Cavity Damping | By introducing thermal entangled state representation which can map master
equations of density operator in quantum statistics as state vector evolution
equations and using dissipative interaction picture we solve the master
equation of J-C model with cavity damping. In addition we derive the Wigner
function for density operator when the atom is initially in the up state and
the cavity mode is in coherent state. | 1402.2556v1 |
2014-02-19 | Superfluid Bloch dynamics in an incommensurate lattice | We investigate the interplay of disorder and interactions in the accelerated
transport of a Bose-Einstein condensate through an incommensurate optical
lattice. We show that interactions can effectively cancel the damping of Bloch
oscillations due to the disordered potential and we provide a simple model to
qualitatively capture this screening effect. We find that the characteristic
interaction energy, above which interactions and disorder cooperate to enhance,
rather than reduce, the damping of Bloch oscillations, coincides with the
average disorder depth. This is consistent with results of a mean-field
simulation. | 1402.4830v1 |
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