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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 |
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 |
2012-01-30 | 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 |
2012-02-18 | Dynamics of multi-modes maximum entangled coherent state over amplitude damping channel | The dynamics of maximum entangled coherent state travels through an amplitude
damping channel is investigated. For small values of the transmissivity rate
the travelling state is very fragile to this noise channel, where it suffers
from the phase flip error with high probability. The entanglement decays
smoothly for larger values of the transmissivity rate and speedily for smaller
values of this rate. As the number of modes increases, the travelling state
over this noise channel loses its entanglement hastily. The odd and even states
vanish at the same value of the field intensity. | 1202.4089v1 |
2012-03-02 | Damping-Antidamping Effect on Comets Motion | We make an observation about Galilean transformation on a 1-D mass variable
systems which leads us to the right way to deal with mass variable systems.
Then using this observation, we study two-bodies gravitational problem where
the mass of one of the bodies varies and suffers a damping-antidamping effect
due to star wind during its motion. For this system, a constant of motion, a
Lagrangian and a Hamiltonian are given for the radial motion, and the period of
the body is studied using the constant of motion of the system. Our theoretical
results are applied to Halley's comet. | 1203.0495v2 |
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 |
2012-03-09 | Collective Light Emission of a Finite Size Atomic Chain | Radiative properties of collective electronic states in a one dimensional
atomic chain are investigated. Radiative corrections are included with
emphasize put on the effect of the chain size through the dependence on both
the number of atoms and the lattice constant. The damping rates of collective
states are calculated in considering radiative effects for different values of
the lattice constant relative to the atomic transition wave length. Especially
the symmetric state damping rate as a function of the number of the atoms is
derived. The emission pattern off a finite linear chain is also presented. The
results can be adopted for any chain of active material, e.g., a chain of
semiconductor quantum dots or organic molecules on a linear matrix. | 1203.2094v1 |
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 |
2012-08-21 | 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 |
2012-09-07 | Quantum Damped Harmonic Oscillator | In this chapter we treat the quantum damped harmonic oscillator, and study
mathematical structure of the model, and construct general solution with any
initial condition, and give a quantum counterpart in the case of taking
coherent state as an initial condition.
This is a simple and good model of Quantum Mechanics with dissipation which
is important to understand real world, and readers will get a powerful weapon
for Quantum Physics. | 1209.1437v1 |
2012-10-08 | Comment on "Thermal fluctuations of magnetic nanoparticles" [arXiv:1209.0298] | We comment on some misleading and biased statements appearing in the
manuscript arXiv:1209.0298 ("Thermal fluctuations of magnetic nanoparticles")
about the use of the damped Landau-Lifshitz equation and the kinetic Langer
theory for the calculation of the relaxation rate of magnetic nanoclusters. We
reiterate simple scientific arguments, part of which is well known to the whole
community, demonstrating that the authors' criticisms are unfounded and that
they overstate the issue of damping in the Landau-Lifshitz equation with no
unanimous experimental evidence. | 1210.2436v1 |
2012-10-10 | Phonon momentum and damping of mechanical resonators | The concept of physical momentum associated to phonons in a crystal,
complemented with some fundamental reasoning, implies measurable effects in
crystals even at a macroscopic scale. We show that, in close analogy with the
transfer of momentum in the kinetic theory of gases, physical momentum carried
by of phonons couples the thermal and the velocity field in a vibrating
crystal. Therefore an heat flow applied to a vibrating crystal can sustain or
damp the oscillation, depending on the interplay between the temperature and
the velocity gradient. We derive the general equations of this effect and show
that its experimental confirmation is within reach of current technology. | 1210.2847v1 |
2012-10-12 | HTS wiggler concept for a damping ring | Magnetic design proposed for a damping ring (DR) is based on second
generation HTS cabling technology applied to the DC windings with a yoke and
mu-metal-shimmed pole to achieve ~2T high-quality field within a 86 mm gap and
32-40 cm period. Low levels of current densities (~90-100A/mm2) provide a
robust, reliable operation of the wiggler at higher heat loads, up to LN2
temperatures with long leads, enhanced flexibility for the cryostats and
infrastructure in harsh radiation environment, and reduced failure rate
compared to the baseline SC ILC DR wiggler design at very competitive cost. | 1210.3648v1 |
2012-10-23 | Dynamic response of open cell dry foams | We study the mechanical response of an open cell dry foam subjected to
periodic forcing using experiments and theory. Using the measurements of the
static and dynamic stress-strain relationship, we derive an over-damped model
of the foam, as a set of infinitesimal non-linear springs, where the damping
term depends on the local foam strain. We then analyse the properties of the
foam when subjected to large amplitudes periodic stresses and determine the
conditions for which the foam becomes optimally absorbing. | 1210.6229v1 |
2012-10-31 | Quantum discord of Bell cat-states under amplitude damping | The evolution of pairwise quantum correlations of Bell cat-states under
amplitude damping is examined using the concept of quantum discord which goes
beyond entanglement. A closed expression of the quantum discord is explicitly
derived. We used of the Koashi-Winter relation. A relation which facilitates
the optimization process of the conditional entropy. We also discuss the
temporal evolution of bipartite quantum correlations under a dephasing channel
and compare the behaviors of quantum discord and entanglement whose properties
are characterized through the concurrence. | 1210.8309v1 |
2012-10-31 | Upsilon suppression in PbPb collisions at the LHC | We suggest that the combined effect of screening, gluon-induced dissociation,
collisional damping, and reduced feed-down explains most of the sequential
suppression of Upsilon(nS) states that has been observed in PbPb relative to pp
collisions at sqrt(s_NN) = 2.76 TeV. The suppression is thus a clear, albeit
indirect, indication for the presence of a QGP. The Upsilon(1S) ground state
suppression is essentially due to reduced feed-down, collisional damping and
gluodissociation, whereas screening prevails for the suppression of the excited
states. | 1210.8366v2 |
2012-11-04 | The Threshold between Effective and Noneffective Damping for Semilinear Waves | In this paper we study the global existence of small data solutions to the
Cauchy problem for the semilinear wave equation with scale-invariant damping.
We obtain estimates for the solution and its energy with the same decay rate of
the linear problem. We extend our results to a model with polynomial speed of
propagation and to a model with an exponential speed of propagation. | 1211.0731v2 |
2012-11-10 | Heavy quark quenching from RHIC to LHC and the consequences of gluon damping | In this contribution to the Quark Matter 2012 conference, we study whether
energy loss models established for RHIC energies to describe the quenching of
heavy quarks can be applied at LHC with the same success. We also benefit from
the larger $p_T$-range accessible at this accelerator to test the impact of
gluon damping on observables such as the nuclear modification factor. | 1211.2281v1 |
2012-11-30 | Local feedback stabilisation to a non-stationary solution for a damped non-linear wave equation | We study a damped semi-linear wave equation in a bounded domain with smooth
boundary. It is proved that any sufficiently smooth solution can be stabilised
locally by a finite-dimensional feedback control supported by a given open
subset satisfying a geometric condition. The proof is based on an investigation
of the linearised equation, for which we construct a stabilising control
satisfying the required properties. We next prove that the same control
stabilises locally the non-linear problem. | 1211.7202v1 |
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 |
2013-04-04 | Pais-Uhlenbeck Oscillator with a Benign Friction Force | It is shown that the Pais-Uhlenbeck oscillator with damping, considered by
Nesterenko, is a special case of a more general oscillator that has not only a
first order, but also a third order friction term. If the corresponding damping
constants, \alpha\ and \beta, are both positive and below certain critical
values, then the system is stable. In particular, if \alpha = - \beta, then we
have the unstable Nesterenko's oscillator | 1304.1325v2 |
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 |
2013-08-30 | 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 |
2013-11-22 | Complexity of the minimum-time damping of a physical pendulum | We study the minimum-time damping of a physical pendulum by means of a
bounded control. In the similar problem for a linear oscillator each optimal
trajectory possesses a finite number of control switchings from the maximal to
the minimal value. If one considers simultaneously all optimal trajectories
with any initial state, the number of switchings can be arbitrary large. We
show that for the nonlinear pendulum there is a uniform bound for the switching
number for all optimal trajectories. We find asymptotics for this bound as the
control amplitude goes to zero. | 1311.5729v1 |
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 |
2014-01-04 | Entanglement and quantum teleportation via decohered tripartite entangled states | The entanglement behavior of two classes of multi-qubit system, GHZ and GHZ
like states passing through a generalized amplitude damping channel is
discussed. Despite this channel causes degradation of the entangled properties
and consequently their abilities to perform quantum teleportation, one can
always improve the lower values of the entanglement and the fidelity of the
teleportrd state by controlling on Bell measurements, analyzer angle and
channel's strength. Using GHZ-like state within a generalized amplitude damping
channel is much better than using the normal GHZ-state, where the decay rate of
entanglement and the fidelity of the teleported states are smaller than those
depicted for GHZ state. | 1401.0796v1 |
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 |
2014-02-21 | Weakly damped acoustic plasmon mode in transition metal dichalcogenides with Zeeman splitting | We analyze the effect of a strong Zeeman field on the spectrum of collective
excitations of monolayer transition metal dichalcogenides. The combination of
the Dresselhaus type spin orbit coupling and an external Zeeman field result in
the lifting of the valley degeneracy in the valence band of these crystals. We
show that this lifting of the valley degeneracy manifests in the appearance of
an additional plasmon mode with linear in wavenumber dispersion along with the
standard square root in wavenumber mode. Despite this novel mode being subject
to the Landau damping, it corresponds to a well defined quasiparticle peak in
the spectral function of the electron gas. | 1402.5274v1 |
2014-04-18 | On the Instability and Critical Damping Conditions, $kτ= 1/e$ and $kτ= π/2$ of the equation $\dotθ = -k θ(t-τ)$ | In this note, I show that it is possible to use elementary mathematics,
instead of the machinery of Lambert function, Laplace Transform, or numerics,
to derive the instability condition, $k \tau = \pi/2$, and the critical damping
condition, $k\tau = 1/e$, for the time-delayed equation $\dot{\theta} = -k
\theta(t-\tau)$. I hope it will be useful for the new comers to this equation,
and perhaps even to the experts if this is a simpler method compared to other
versions. | 1404.4763v1 |
2014-04-22 | Nonlinear-damped Duffing oscillators having finite time dynamics | A class of modified Duffing oscillator differential equations, having
nonlinear damping forces, are shown to have finite time dynamics, i.e., the
solutions oscillate with only a finite number of cycles, and, thereafter, the
motion is zero. The relevance of this feature is briefly discussed in
relationship to the mathematical modeling, analysis, and estimation of
parameters for the vibrations of carbon nano-tubes and graphene sheets, and
macroscopic beams and plates. | 1404.5596v1 |
2014-05-01 | On the collapse of trial solutions for a damped-driven non-linear Schrödinger equation | We consider the focusing 2D non-linear Schr\"odinger equation, perturbed by a
damping term, and driven by multiplicative noise. We show that a physically
motivated trial solution does not collapse for any admissible initial condition
although the exponent of the non-linearity is critical. Our method is based on
the construction of a global solution to a singular stochastic Hamiltonian
system used to connect trial solution and Schr\"odinger equation. | 1405.0151v3 |
2014-05-02 | Dynamic phase diagram of dc-pumped magnon condensates | We study the effects of nonlinear dynamics and damping by phonons on a system
of interacting electronically pumped magnons in a ferromagnet. The nonlinear
effects are crucial for constructing the dynamic phase diagram, which describes
how "swasing" and Bose-Einstein condensation emerge out of the
quasiequilibrated thermal cloud of magnons. We analyze the system in the
presence of magnon damping and interactions, demonstrating the continuous onset
of stable condensates as well as hysteretic transitions. | 1405.0522v1 |
2014-05-05 | Finite time extinction for nonlinear Schrodinger equation in 1D and 2D | We consider a nonlinear Schrodinger equation with power nonlinearity, either
on a compact manifold without boundary, or on the whole space in the presence
of harmonic confinement, in space dimension one and two. Up to introducing an
extra superlinear damping to prevent finite time blow up, we show that the
presence of a sublinear damping always leads to finite time extinction of the
solution in 1D, and that the same phenomenon is present in the case of small
mass initial data in 2D. | 1405.0995v1 |
2014-05-16 | Investigation of Power-Law Damping/Dissipative Forces | The properties of a one space-dimension, one particle dynamical system under
the influence of a purely dissipative force are investigated. Assuming this
force depends only on the velocity, it is demonstrated, in contrast to the case
of linear damping, that there exist dissipative forces for which the particle
\textquotedblleft stops" in a finite time. It is also shown, by an explicit
example, that other dissipative forces exist such that they produce dynamics in
which the particle achieves zero velocity only after an infinite distance has
been traveled. Possible applications of these results to more complex
situations are discussed. | 1405.4062v1 |
2014-06-02 | Nonlinear coupler operating on Werner-like states - entanglement creation, its enhancement and preservation | We discuss a model of two nonlinear Kerr-like oscillators, mutually coupled
and excited by parametric process. We show that the system's evolution,
starting from Werner-like states, remains closed within a small set of two-mode
n-photon states the system, and pure two-qubit entangled state can be
generated. For some initial Werner-like states delayed entanglement generation
can be observed. We investigate the influence of two damping mechanisms on the
system's evolution. We show that for the both cases, the entanglement can
survive despite the presence of damping, and the effects of sudden entanglement
death and its rebirth can appear in the system. | 1406.0414v1 |
2014-06-10 | A determining form for the damped driven Nonlinear Schrödinger Equation- Fourier modes case | In this paper we show that the global attractor of the 1D damped, driven,
nonlinear Schr\"odinger equation (NLS) is embedded in the long-time dynamics of
a determining form. The determining form is an ordinary differential equation
in a space of trajectories $X=C_b^1(\mathbb{R}, P_mH^2)$ where $P_m$ is the
$L^2$-projector onto the span of the first $m$ Fourier modes. There is a
one-to-one identification with the trajectories in the global attractor of the
NLS and the steady states of the determining form. We also give an improved
estimate for the number of the determining modes. | 1406.2626v1 |
2014-08-20 | Initial Layer and Relaxation Limit of Non-Isentropic Compressible Euler Equations with Damping | In this paper, we study the relaxation limit of the relaxing Cauchy problem
for non-isentropic compressible Euler equations with damping in
multi-dimensions. We prove that the velocity of the relaxing equations
converges weakly to that of the relaxed equations, while other variables of the
relaxing equations converges strongly to the corresponding variables of the
relaxed equations. We show that as relaxation time approaches 0, there exists
an initial layer for the ill-prepared data, the convergence of the velocity is
strong outside the layer; while there is no initial layer for the well-prepared
data, the convergence of the velocity is strong near t=0. | 1408.4784v1 |
2014-08-26 | Exponential decay for the damped wave equation in unbounded domains | We study the decay of the semigroup generated by the damped wave equation in
an unbounded domain. We first prove under the natural geometric control
condition the exponential decay of the semigroup. Then we prove under a weaker
condition the logarithmic decay of the solutions (assuming that the initial
data are smoother). As corollaries, we obtain several extensions of previous
results of stabilisation and control. | 1408.6054v2 |
2014-10-03 | Relaxation of regularity for the Westervelt equation by nonlinear damping with application in acoustic-acoustic and elastic-acoustic coupling | In this paper we show local (and partially global) in time existence for the
Westervelt equation with several versions of nonlinear damping. This enables us
to prove well-posedness with spatially varying $L_\infty$-coefficients, which
includes the situation of interface coupling between linear and nonlinear
acoustics as well as between linear elasticity and nonlinear acoustics, as
relevant, e.g., in high intensity focused ultrasound (HIFU) applications. | 1410.0797v1 |
2014-10-13 | Vortex gyration mediated by spin waves driven by an out-of-plane oscillating magnetic field | In this letter we address the vortex core dynamics involved in gyration
excitation and damping change by out-of-plane oscillating magnetic fields. When
the vortex core is at rest under the effect of in-plane bias magnetic fields,
the spin waves excited by the perpendicular magnetic field can induce obvious
vortex gyration. When simultaneously excite spin waves and vortex gyrotropic
motion, the gyration damping changes. Analysis of the system energy allows us
to explain the origin of the spin-wave-mediated vortex gyration. | 1410.3230v1 |
2014-10-23 | Non-equilibrium thermodynamics approach to open quantum systems | Open quantum systems are studied from the thermodynamical point of view
unifying the principle of maximum informational entropy and the hypothesis of
relaxation times hierarchy. The result of the unification is a non-Markovian
and local in time master equation that provides a direct connection of
dynamical and thermodynamical properties of open quantum systems. The power of
the approach is illustrated with the application to the damped harmonic
oscillator and the damped driven two-level system resulting in analytical
expressions for the non-Markovian and non-equilibrium entropy and inverse
temperature. | 1410.6312v2 |
2014-10-27 | Linear Inviscid Damping for Monotone Shear Flows | In this article, we prove linear stability, scattering and inviscid damping
with optimal decay rates for the linearized 2D Euler equations around a large
class of strictly monotone shear flows, $(U(y),0)$, in a periodic channel under
Sobolev perturbations. Here, we consider the settings of both an infinite
periodic channel of period $L$, $\mathbb{T}_{L}\times \mathbb{R}$, as well as a
finite periodic channel, $\mathbb{T}_{L} \times [0,1]$, with impermeable walls.
The latter setting is shown to not only be technically more challenging, but to
exhibit qualitatively different behavior due to boundary effects. | 1410.7341v2 |
2014-11-08 | Damping of liquid sloshing by foams: from everyday observations to liquid transport | We perform experiments on the sloshing dynamics of liquids in a rectangular
container submitted to an impulse. We show that when foam is placed on top of
the liquid the oscillations of the free interface are significantly damped. The
ability to reduce sloshing and associated splashing could find applications in
numerous industrial processes involving liquid transport. | 1411.2123v1 |
2014-11-17 | A geometric mesh smoothing algorithm related to damped oscillations | We introduce a smoothing algorithm for triangle, quadrilateral, tetrahedral
and hexahedral meshes whose centerpiece is a simple geometric triangle
transformation. The first part focuses on the mathematical properties of the
element transformation. In particular, the transformation gives rise directly
to a continuous model given by a system of coupled damped oscillations. Derived
from this physical model, adaptive parameters are introduced and their benefits
presented. The second part discusses the mesh smoothing algorithm based on the
element transformation and its numerical performance on example meshes. | 1411.4390v3 |
2014-12-05 | Exponential dephasing of oscillators in the Kinetic Kuramoto Model | We study the kinetic Kuramoto model for coupled oscillators with coupling
constant below the synchronization threshold. We manage to prove that, for any
analytic initial datum, if the interaction is small enough, the order parameter
of the model vanishes exponentially fast, and the solution is asymptotically
described by a free flow. This behavior is similar to the phenomenon of Landau
damping in plasma physics. In the proof we use a combination of techniques from
Landau damping and from abstract Cauchy-Kowalewskaya theorem. | 1412.1923v1 |
2014-12-23 | Selftrapping triggered by losses in cavity QED | In a coupled cavity QED network model, we study the transition from a
localized super fluid like state to a delocalized Mott insulator like state,
triggered by losses. Without cavity losses, the transition never takes place.
Further, if one measures the quantum correlations between the polaritons via
the negativity, we find a critical cavity damping constant, above which the
negativity displays a single peak in the same time region where the transition
takes place. Additionally, we identify two regions in the parameter space,
where below the critical damping, oscillations of the initial localized state
are observed along with a multipeaked negativity, while above the critical
value, the oscillations die out and the transition is witnessed by a neat
single peaked negativity. | 1412.7495v1 |
2015-01-07 | Two-photon lasing by a superconducting qubit | We study the response of a magnetic-field-driven superconducting qubit
strongly coupled to a superconducting coplanar waveguide resonator. We observed
a strong amplification/damping of a probing signal at different resonance
points corresponding to a one and two-photon emission/absorption. The sign of
the detuning between the qubit frequency and the probe determines whether
amplification or damping is observed. The larger blue detuned driving leads to
two-photon lasing while the larger red detuning cools the resonator. Our
experimental results are in good agreement with the theoretical model of qubit
lasing and cooling at the Rabi frequency. | 1501.01543v1 |
2015-02-02 | Enhanced oscillation lifetime of a Bose-Einstein condensate in the 3D/1D crossover | We have measured the damped motion of a trapped Bose-Einstein condensate,
oscillating with respect to a thermal cloud. The cigar-shaped trapping
potential provides enough transverse confinement that the dynamics of the
system are intermediate between three-dimensional and one-dimensional. We find
that oscillations persist for longer than expected for a three-dimensional gas.
We attribute this to the suppressed occupation of transverse momentum states,
which are essential for damping. | 1502.00430v2 |
2015-02-03 | Nonequilibrium dynamics of an ultracold dipolar gas | We study the relaxation and damping dynamics of an ultracold, but not quantum
degenerate, gas consisting of dipolar particles. These simulations are
performed using a direct simulation Monte Carlo method and employing the highly
anisotropic differential cross section of dipoles in the Wigner threshold
regime. We find that both cross-dimensional relaxation and damping of breathing
modes occur at rates that are strongly dependent on the orientation of the
dipole moments relative to the trap axis. The relaxation simulations are in
excellent agreement with recent experimental results in erbium. The results
direct our interest toward a less explored regime in dipolar gases where
interactions are dominated by collision processes rather than mean-field
interactions. | 1502.00960v1 |
2015-02-01 | On the Stability of Cylindrical Tangential Discontinuity, Generation and Damping of Helical Waves | Stability of cylindrical interface between two ideal incompressible fluids,
including the magnetic field, surface tension and gravitational field is
studied in linear approximation. We found that helical waves arising both in
plasma comet tails and on the vertical cylindrical water jet in the air are
described by the same dispersion equation where the comet tail magnetic field
plays the same stabilizing role as surface tension for water jet. Hence they
represent the same phenomenon of Kelvin-Helmholtz instability. Thus helical
waves in comet tails and astrophysical jets may be simulated in the laboratory.
The resonance nature of the Kelvin- instability damping is demonstrated. | 1502.00989v1 |
2015-03-04 | On the Lewis-Riesenfeld (Dodonov-Man'ko) invariant method | We revise the Lewis-Riesenfeld invariant method for solving the quantum
time-dependent harmonic oscillator in light of the Quantum Arnold
Transformation previously introduced and its recent generalization to the
Quantum Arnold-Ermakov-Pinney Transformation. We prove that both methods are
equivalent and show the advantages of the Quantum Arnold-Ermakov-Pinney
transformation over the Lewis-Riesenfeld invariant method. We show that, in the
quantum time-dependent and damped harmonic oscillator, the invariant proposed
by Dodonov & Man'ko is more suitable and provide some examples to illustrate
it, focusing on the damped case. | 1503.01371v1 |
2015-03-06 | On the strongly damped wave equation with constraint | A weak formulation for the so-called "semilinear strongly damped wave
equation with constraint" is introduced and a corresponding notion of solution
is defined. The main idea in this approach consists in the use of duality
techniques in Sobolev-Bochner spaces, aimed at providing a suitable
"relaxation" of the constraint term. A global in time existence result is
proved under the natural condition that the initial data have finite "physical"
energy. | 1503.01911v1 |
2015-03-23 | Spin-Orbit Torques in Two-Dimensional Rashba Ferromagnets | Magnetization dynamics in single-domain ferromagnets can be triggered by
charge current if spin-orbit coupling is sufficiently strong. We apply
functional Keldysh theory to investigate Rashba spin-orbit torques in metallic
two-dimensional ferromagnets. A reactive, anti-damping-like spin-orbit torque
as well as a dissipative, field-like torque are calculated microscopically, to
the leading order in the spin-orbit interaction strength. By calculating the
first vertex correction we show that the intrinsic anti-damping-like torque
vanishes unless the scattering rates are spin-dependent. | 1503.06872v2 |
2015-04-18 | Global Dirichlet Heat Kernel Estimates for Symmetric Lévy Processes in Half-space | In this paper, we derive explicit sharp two-sided estimates for the Dirichlet
heat kernels of a large class of symmetric (but not necessarily rotationally
symmetric) L\'evy processes on half spaces for all $t>0$. These L\'evy
processes may or may not have Gaussian component. When L\'evy density is
comparable to a decreasing function with damping exponent $\beta$,our estimate
is explicit in terms of the distance to the boundary, the L\'evy exponent and
the damping exponent $\beta$ of L\'evy density. | 1504.04673v2 |
2015-05-05 | The transition from the classical to the quantum regime in nonlinear Landau damping | Starting from the Wigner-Moyal equation coupled to Poisson's equation, a
simplified set of equations describing nonlinear Landau damping of Langmuir
waves is derived. This system is studied numerically, with a particular focus
on the transition from the classical to the quantum regime. In the quantum
regime several new features are found. This includes a quantum modified bounce
frequency, and the discovery that bounce-like amplitude oscillations can take
place even in the absence of trapped particles. The implications of our results
are discussed. | 1505.01381v1 |
2015-05-08 | The amplification of weak measurements under quantum noise | The influence of outside quantum noises on the amplification of weak
measurements is investigated. Three typical quantum noises are discussed. The
maximum values of the pointer's shifts decrease sharply with the strength of
the depolarizing channel and phase damping. In order to obtain significant
amplified signals, the preselection quantum systems must be kept away from the
two quantum noises. Interestingly, the amplification effect is immune to the
amplitude damping noise. | 1505.01911v1 |
2015-05-27 | Local energy decay and smoothing effect for the damped Schr{ö}dinger equation | We prove the local energy decay and the smoothing effect for the damped
Schr{\"o}dinger equation on R^d. The self-adjoint part is a Laplacian
associated to a long-range perturbation of the flat metric. The proofs are
based on uniform resolvent estimates obtained by the dissipative Mourre method.
All the results depend on the strength of the dissipation which we consider. | 1505.07200v1 |
2015-06-01 | Local decay for the damped wave equation in the energy space | We improve a previous result about the local energy decay for the damped wave
equation on R^d. The problem is governed by a Laplacian associated with a long
range perturbation of the flat metric and a short range absorption index. Our
purpose is to recover the decay O(t^{--d+$\epsilon$}) in the weighted energy
spaces. The proof is based on uniform resolvent estimates, given by an improved
version of the dissipative Mourre theory. In particular we have to prove the
limiting absorption principle for the powers of the resolvent with inserted
weights. | 1506.00377v1 |
2015-06-03 | Giant Phonon Anomaly associated with Superconducting Fluctuations in the Pseudogap Phase of Cuprates | The opening of the pseudogap in underdoped cuprates breaks up the Fermi
surface, which may lead to a breakup of the d-wave order parameter into two
subband amplitudes and a low energy Leggett mode due to phase fluctuations
between them. This causes a large increase in the temperature range of
superconducting fluctuations with an overdamped Leggett mode. Almost resonant
scattering of inter-subband phonons to a state with a pair of Leggett modes
causes anomalously strong damping. In the ordered state, the Leggett mode
develops a finite energy, suppressing the anomalous phonon damping but leading
to an anomaly in the phonon dispersion. | 1506.01258v1 |
2015-06-06 | On higher regularity for the Westervelt equation with strong nonlinear damping | We show higher interior regularity for the Westervelt equation with strong
nonlinear damping term of the $q$-Laplace type. Secondly, we investigate an
interface coupling problem for these models, which arise, e.g., in the context
of medical applications of high intensity focused ultrasound in the treatment
of kidney stones. We show that the solution to the coupled problem exhibits
piecewise $H^2$ regularity in space, provided that the gradient of the acoustic
pressure is essentially bounded in space and time on the whole domain. This
result is of importance in numerical approximations of the present problem, as
well as in gradient based algorithms for finding the optimal shape of the
focusing acoustic lens in lithotripsy. | 1506.02125v1 |
2015-06-08 | Intermode-coupling modulation in the fermion-boson model: heating effects in the BCS regime | Heating induced by an oscillating modulation of the interaction strength in
an atomic Fermion pair condensate is analyzed. The coupled fermion-boson model,
generalized by incorporating a time-dependent intermode coupling through a
magnetic Feshbach resonance, is applied. The dynamics is analytically
characterized in a perturbative scheme. The results account for experimental
findings which have uncovered a damped and delayed response of the condensate
to the modulation. The delay is due to the variation of the quasiparticle
energies and the subsequent relaxation of the condensate. The detected damping
results from the excitations induced by a nonadiabatic modulation: for driving
frequencies larger than twice the pairing gap, quasiparticles are generated,
and, consequently, heating sets in. | 1506.02612v1 |
2015-06-22 | N-body description of Debye shielding and Landau damping | This paper brings further insight into the recently published N-body
description of Debye shielding and Landau damping [Escande D F, Elskens Y and
Doveil F 2014 Plasma Phys. Control. Fusion 57 025017]. Its fundamental equation
for the electrostatic potential is derived in a simpler and more rigorous way.
Various physical consequences of the new approach are discussed, and this
approach is compared with the seminal one by Pines and Bohm [Pines D and Bohm D
1952 Phys. Rev. 85 338--353]. | 1506.06468v2 |
2015-07-23 | Millisecond newly born pulsars as efficient accelerators of electrons | The newly born millisecond pulsars are investigated as possible energy
sources for creating ultra-high energy electrons. The transfer of energy from
the star rotation to high energy electrons takes place through the Landau
damping of centrifugally driven (via a two stream instability) electrostatic
Langmuir waves. Generated in the bulk magnetosphere plasma, such waves grow to
high amplitudes, and then damp, very effectively, on relativistic electrons
driving them to even higher energies. We show that the rate of transfer of
energy is so efficient that no energy losses might affect the mechanism of
particle acceleration; the electrons might achieve energies of the order of
10^{18}eV for parameters characteristic of a young star. | 1507.06415v1 |
2015-07-28 | Stability of solutions to nonlinear wave equations with switching time-delay | In this paper we study well-posedness and asymptotic stability for a class of
nonlinear second-order evolution equations with intermittent delay damping.
More precisely, a delay feedback and an undelayed one act alternately in time.
We show that, under suitable conditions on the feedback operators, asymptotic
stability results are available. Concrete examples included in our setting are
illustrated. We give also stability results for an abstract model with
alternate positive-negative damping, without delay. | 1507.07787v1 |
2015-08-10 | Theory of the strongly-damped quantum harmonic oscillator | We analyse the properties of a strongly-damped quantum harmonic oscillator by
means of an exact diagonalisation of the full Hamiltonian, including both the
oscillator and the reservoir degrees of freedom to which it is coupled. Many of
the properties of the oscillator, including its steady-state properties and
entanglement with the reservoir can be understood and quantified in terms of a
simple probability density, which we may associate with the ground-state
frequency spectrum of the oscillator. | 1508.02442v1 |
2015-08-20 | Bump-on-tail instability of twisted excitations in rotating cold atomic clouds | We develop a kinetic theory for twisted density waves (phonons), carrying a
finite amount of orbital angular momentum, in large magneto optical traps,
where the collective processes due to the exchange of scattered photons are
considered. Explicit expressions for the dispersion relation and for the
kinetic (Landau) damping are derived and contributions from the orbital angular
momentum are discussed. We show that for rotating clouds, exhibiting
ring-shaped structures, phonons carrying orbital angular momentum can cross the
instability threshold and grow out of noise, while the usual plane wave
solutions are kinetically damped. | 1508.05127v1 |
2015-09-30 | Approximation of Invariant Measure for Damped Stochastic Nonlinear Schrödinger Equation via an Ergodic Numerical Scheme | In order to inherit numerically the ergodicity of the damped stochastic
nonlinear Schr\"odinger equation with additive noise, we propose a fully
discrete scheme, whose spatial direction is based on spectral Galerkin method
and temporal direction is based on a modification of the implicit Euler scheme.
We not only prove the unique ergodicity of the numerical solutions of both
spatial semi-discretization and full discretization, but also present error
estimations on invariant measures, which gives order $2$ in spatial direction
and order ${\frac12}$ in temporal direction. | 1509.09148v2 |
2015-10-02 | Cavity and HOM Coupler Design for CEPC | In this paper we will show a cavity and higher order mode (HOM) coupler
designing scheme for the Circular Electron-Positron Collider (CEPC) main ring.
The cavity radio frequency (RF) design parameters are showed in this paper. The
HOM power is calculated based on the beam parameters in the Preliminary
Conceptual Design Report (Pre-CDR). The damping results of the higher order
modes (HOMs) and same order modes (SOMs) show that they are reached the damping
requirements for beam stability. | 1510.00467v1 |
2015-11-08 | Upper semicontinuity of pullback attractors for damped wave equations | In this paper, we study the upper semicontinuity of pullback attractors for a
strongly damped wave equation. In particular, under some proper assumptions, we
prove that, the pullback attractor $\{A_\varepsilon(t)\}_{t\in\mathbb R}$} of
Eq.(1.1) with $\varepsilon\in[0,1]$ satisfies that for any $[a,b]\subset\mathbb
R$ and $\varepsilon_0\in[0,1]$, $\lim_{\varepsilon\to\varepsilon_0}
\sup_{t\in[a,b]} \mathrm{dist}_{H_0^1\times L^2} (A_\varepsilon(t),
A_{\varepsilon_0}(t))=0$, and $\cup_{t\in[a,b]} \cup_{\varepsilon\in[0,1]}
A_\varepsilon(t)$ is precompact in $H_0^1 (\Omega) \times L^2(\Omega)$. | 1511.02481v2 |
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