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1997-08-14
|
Landau damping in dilute Bose gases
|
Landau damping in weakly interacting Bose gases is investigated by means of
perturbation theory. Our approach points out the crucial role played by
Bose-Einstein condensation and yields an explicit expression for the decay rate
of elementary excitations in both uniform and non uniform gases. Systematic
results are derived for the phonon width in homogeneous gases interacting with
repulsive forces. Special attention is given to the low and high temperature
regimes.
|
9708104v1
|
1997-11-07
|
Coulomb suppression of NMR coherence peak in fullerene superconductors
|
The suppressed NMR coherence peak in the fullerene superconductors is
explained in terms of the dampings in the superconducting state induced by the
Coulomb interaction between conduction electrons. The Coulomb interaction,
modelled in terms of the onsite Hubbard repulsion, is incorporated into the
Eliashberg theory of superconductivity with its frequency dependence considered
self-consistently at all temperatures. The vertex correction is also included
via the method of Nambu. The frequency dependent Coulomb interaction induces
the substantial dampings in the superconducting state and, consequently,
suppresses the anticipated NMR coherence peak of fullerene superconductors as
found experimentally.
|
9711060v2
|
1997-12-09
|
The Sound of Sonoluminescence
|
We consider an air bubble in water under conditions of single bubble
sonoluminescence (SBSL) and evaluate the emitted sound field nonperturbatively
for subsonic gas-liquid interface motion. Sound emission being the dominant
damping mechanism, we also implement the nonperturbative sound damping in the
Rayleigh-Plesset equation for the interface motion. We evaluate numerically the
sound pulse emitted during bubble collapse and compare the nonperturbative and
perturbative results, showing that the usual perturbative description leads to
an overestimate of the maximal surface velocity and maximal sound pressure. The
radius vs. time relation for a full SBSL cycle remains deceptively unaffected.
|
9712097v1
|
1998-07-02
|
Linear systems with adiabatic fluctuations
|
We consider a dynamical system subjected to weak but adiabatically slow
fluctuations of external origin. Based on the ``adiabatic following''
approximation we carry out an expansion in \alpha/|\mu|, where \alpha is the
strength of fluctuations and 1/|\mu| refers to the time scale of evolution of
the unperturbed system to obtain a linear differential equation for the average
solution. The theory is applied to the problems of a damped harmonic oscillator
and diffusion in a turbulent fluid. The result is the realization of
`renormalized' diffusion constant or damping constant for the respective
problems. The applicability of the method has been critically analyzed.
|
9807031v1
|
1998-12-02
|
Vortex lattice melting and the damping of the dHvA oscillations in the mixed state
|
Phase fluctuations in the superconducting order parameter, which are
responsible for the melting of the Abrikosov vortex lattice below the mean
field $H_{c2}$, are shown to dramatically enhance the scattering of
quasi-particles by the fluctuating pair potential, thus leading to enhanced
damping of the dHvA oscillations in the liquid mixed state. This effect is
shown to quantitatively account for the detailed field dependence of the dHvA
amplitude observed recently in the mixed state of a Quasi 2D organic SC.
|
9812040v1
|
1999-01-19
|
Damping of Growth Oscillations
|
Computer simulations and scaling theory are used to investigate the damping
of oscillations during epitaxial growth on high-symmetry surfaces. The
crossover from smooth to rough growth takes place after the deposition of
(D/F)^\delta monolayers, where D and F are the surface diffusion constant and
the deposition rate, respectively, and the exponent \delta=2/3 on a
two-dimensional surface. At the transition, layer-by-layer growth becomes
desynchronized on distances larger than a layer coherence length proportional
l^2, where l is a typical distance between two-dimensional islands in the
submonolayer region of growth.
|
9901178v1
|
1999-06-15
|
Temperature-induced resonances and Landau damping of collective modes in Bose-Einstein condensed gases in spherical traps
|
Interaction between collective monopole oscillations of a trapped
Bose-Einstein condensate and thermal excitations is investigated by means of
perturbation theory. We assume spherical symmetry to calculate the matrix
elements by solving the linearized Gross-Pitaevskii equations. We use them to
study the resonances of the condensate induced by temperature when an external
perturbation of the trapping frequency is applied and to calculate the Landau
damping of the oscillations.
|
9906214v1
|
1999-08-03
|
Kinetic Theory of Collective Modes in Atomic Clouds above the Bose-Einstein Transition Temperature
|
We calculate frequencies and damping rates of the lowest collective modes of
a dilute Bose gas confined in an anisotropic trapping potential above the
Bose-Einstein transition temperature. From the Boltzmann equation with a
simplified collision integral we derive a general dispersion relation that
interpolates between the collisionless and hydrodynamic regimes. In the case of
axially symmetric traps we obtain explicit expressions for the frequencies and
damping rates of the lowest modes in terms of a phenomenological collision
time. Our results are compared with microscopic calculations and experiments.
|
9908043v1
|
1999-09-01
|
Normal Fermi Liquid Behavior of Quasiholes in the Spin-Polaron Model for Copper Oxides
|
Based on the t-J model and the self-consistent Born approximation, the
damping of quasiparticle hole states near the Fermi surface is calculated in a
low doping regime. Renormalization of spin-wave excitations due to hole doping
is taken into account. The damping is shown to be described by a familiar form
$\text{Im}\Sigma({\bf k}^{\prime},\epsilon)\propto (\epsilon^{2}/
\epsilon_{F})\ln(\epsilon/ \epsilon_{F})$ characteristic of the 2-dimensional
Fermi liquid, in contrast with the earlier statement reported by Li and Gong
[Phys. Rev. B {\bf 51}, 6343 (1995)] on the marginal Fermi liquid behavior of
quasiholes.
|
9909020v1
|
1999-12-01
|
Impurity relaxation mechanism for dynamic magnetization reversal in a single domain grain
|
The interaction of coherent magnetization rotation with a system of two-level
impurities is studied. Two different, but not contradictory mechanisms, the
`slow-relaxing ion' and the `fast-relaxing ion' are utilized to derive a system
of integro-differential equations for the magnetization. In the case that the
impurity relaxation rate is much greater than the magnetization precession
frequency, these equations can be written in the form of the Landau-Lifshitz
equation with damping. Thus the damping parameter can be directly calculated
from these microscopic impurity relaxation processes.
|
9912014v1
|
2000-02-16
|
Dissipative dynamics of Bose condensates in optical cavities
|
We study the zero temperature dynamics of Bose-Einstein condensates in driven
high-quality optical cavities in the limit of large atom-field detuning. We
calculate the stationary ground state and the spectrum of coupled atom and
field mode excitations for standing wave cavities as well as for travelling
wave cavities. Finite cavity response times lead to damping or controlled
amplification of these excitations. Analytic solutions in the Lamb-Dicke
expansion are in good agreement with numerical results for the full problem and
show that oscillation frequencies and the corresponding damping rates are
qualitatively different for the two cases.
|
0002247v1
|
2000-03-27
|
Effect of memory and dynamical chaos in long Josephson junctions
|
A long Josephson junction in a constant external magnetic field and in the
presence of a dc bias current is investigated. It is shown that the system,
simulated by the sine-Gorgon equation, "remembers" a rapidly damping initial
perturbation and final asymptotic states are determined exactly with this
perturbation. Numerical solving of the boundary sine-Gordon problem and
calculations of Lyapunov indices show that this system has a memory even when
it is in a state of dynamical chaos, i.e., dynamical chaos does not destroy
initial information having a character of rapidly damping perturbation.
|
0003421v1
|
2000-09-13
|
Oscillations of the superconducting order parameter in a ferromagnet
|
Planar tunneling spectroscopy reveals damped oscillations of the
superconducting order parameter induced into a ferromagnetic thin film by the
proximity effect. The oscillations are due to the finite momentum transfer
provided to Cooper pairs by the splitting of the spin up and down bands in the
ferromagnet. As a consequence, for negative values of the superconducting order
parameter the tunneling spectra are capsized ("$\pi$-state"). The oscillations'
damping and period are set by the same length scale, which depends on the spin
polarization.
|
0009192v1
|
2000-09-29
|
Damping and revivals of collective oscillations in a finite-temperature model of trapped Bose-Einstein condensation
|
We utilize a two-gas model to simulate collective oscillations of a
Bose-Einstein condensate at finite temperatures. The condensate is described
using a generalized Gross-Pitaevskii equation, which is coupled to a thermal
cloud modelled by a Monte Carlo algorithm. This allows us to include the
collective dynamics of both the condensed and non-condensed components
self-consistently. We simulate quadrupolar excitations, and measure the damping
rate and frequency as a function of temperature. We also observe revivals in
condensate oscillations at high temperatures, and in the thermal cloud at low
temperature. Extensions of the model to include non-equilibrium effects and
describe more complex phenomena are discussed.
|
0009468v1
|
2001-04-18
|
Effective rate equations for the over-damped motion in fluctuating potentials
|
We discuss physical and mathematical aspects of the over-damped motion of a
Brownian particle in fluctuating potentials. It is shown that such a system can
be described quantitatively by fluctuating rates if the potential fluctuations
are slow compared to relaxation within the minima of the potential, and if the
position of the minima does not fluctuate. Effective rates can be calculated;
they describe the long-time dynamics of the system. Furthermore, we show the
existence of a stationary solution of the Fokker-Planck equation that describes
the motion within the fluctuating potential under some general conditions. We
also show that a stationary solution of the rate equations with fluctuating
rates exists.
|
0104330v1
|
2001-09-05
|
Spin Excitations in a Fermi Gas of Atoms
|
We have experimentally investigated a spin excitation in a quantum degenerate
Fermi gas of atoms. In the hydrodynamic regime the damping time of the
collective excitation is used to probe the quantum behavior of the gas. At
temperatures below the Fermi temperature we measure up to a factor of 2
reduction in the excitation damping time. In addition we observe a strong
excitation energy dependence for this quantum statistical effect.
|
0109098v2
|
2001-10-09
|
Freezing of a Stripe Liquid
|
The existence of a stripe-liquid phase in a layered nickelate,
La(1.725)Sr(0.275)NiO(4), is demonstrated through neutron scattering
measurements. We show that incommensurate magnetic fluctuations evolve
continuously through the charge-ordering temperature, although an abrupt
decrease in the effective damping energy is observed on cooling through the
transition. The energy and momentum dependence of the magnetic scattering are
parametrized with a damped-harmonic-oscillator model describing overdamped
spin-waves in the antiferromagnetic domains defined instantaneously by charge
stripes.
|
0110191v2
|
2001-12-13
|
Magnon softening and damping in the ferromagnetic manganites due to orbital correlations
|
We present a theory for spin excitations in ferromagnetic metallic manganites
and demonstrate that orbital fluctuations have strong effects on the magnon
dynamics in the case these compounds are close to a transition to an orbital
ordered state. In particular we show that the scattering of the spin
excitations by low-lying orbital modes with cubic symmetry causes both the
magnon softening and damping observed experimentally.
|
0112252v2
|
2002-01-16
|
Quantum Spin dynamics of the Bilayer Ferromagnet La(1.2)Sr(1.8)Mn2O7
|
We construct a theory of spin wave excitations in the bilayer manganite
La(1.2)Sr(1.8)Mn2O7 based on the simplest possible double-exchange model, but
including leading quantum corrections to the spin wave dispersion and damping.
Comparison is made with recent inelastic neutron scattering experiments. We
find that quantum effects account for some part of the measured damping of spin
waves, but cannot by themselves explain the observed softening of spin waves at
the zone boundary. Furthermore a doping dependence of the total spin wave
dispersion and the optical spin wave gap is predicted.
|
0201269v1
|
2002-02-21
|
Dynamics of a Bose-Einstein condensate at finite temperature in an atomoptical coherence filter
|
The macroscopic coherent tunneling through the barriers of a periodic
potential is used as an atomoptical filter to separate the condensate and the
thermal components of a $^{87}$Rb mixed cloud. We condense in the combined
potential of a laser standing-wave superimposed on the axis of a cigar-shape
magnetic trap and induce condensate dipole oscillation in the presence of a
static thermal component. The oscillation is damped due to interaction with the
thermal fraction and we investigate the role played by the periodic potential
in the damping process.
|
0202369v1
|
2002-03-11
|
A Damping of the de Haas-van Alphen Oscillations in the superconducting state
|
Deploying a recently developed semiclassical theory of quasiparticles in the
superconducting state we study the de Haas-van Alphen effect. We find that the
oscillations have the same frequency as in the normal state but their amplitude
is reduced. We find an analytic formulae for this damping which is due to
tunnelling between semiclassical quasiparticle orbits comprising both
particle-like and hole-like segments. The quantitative predictions of the
theory are consistent with the available data.
|
0203224v1
|
2002-03-26
|
Measurement induced quantum-classical transition
|
A model of an electrical point contact coupled to a mechanical system
(oscillator) is studied to simulate the dephasing effect of measurement on a
quantum system. The problem is solved at zero temperature under conditions of
strong non-equilibrium in the measurement apparatus. For linear coupling
between the oscillator and tunneling electrons, it is found that the oscillator
dynamics becomes damped, with the effective temperature determined by the
voltage drop across the junction. It is demonstrated that both the quantum
heating and the quantum damping of the oscillator manifest themselves in the
current-voltage characteristic of the point contact.
|
0203521v3
|
2002-07-04
|
Fluctuations and correlations in hexagonal optical patterns
|
We analyze the influence of noise in transverse hexagonal patterns in
nonlinear Kerr cavities. The near field fluctuations are determined by the
neutrally stable Goldstone modes associated to translational invariance and by
the weakly damped soft modes. However these modes do not contribute to the far
field intensity fluctuations which are dominated by damped perturbations with
the same wave vectors than the pattern. We find strong correlations between the
intensity fluctuations of any arbitrary pair of wave vectors of the pattern.
Correlation between pairs forming 120 degrees is larger than between pairs
forming 180 degrees, contrary to what a naive interpretation of emission in
terms of twin photons would suggest.
|
0207127v2
|
2002-09-19
|
Damping of long-wavelength collective excitations in quasi-onedimensional Fermi liquids
|
The imaginary part of the exchange-correlation kernel in the longitudinal
current-current response function of a quasi-onedimensional Fermi liquid is
evaluated by an approximate decoupling in the equation of motion for the
current density, which accounts for processes of excitation of two
particle-hole pairs. The two-pair spectrum determines the intrinsic damping
rate of long-wavelength collective density fluctuations, which is calculated
and contrasted with a result previously obtained for a clean Luttinger liquid.
|
0209455v1
|
2002-11-05
|
Magnetic fluctuations and resonant peak in cuprates: a microscopic theory
|
The theory for the dynamical spin susceptibility within the t-J model is
developed, as relevant for the resonant magnetic peak and normal-state magnetic
response in superconducting (SC) cuprates. The analysis is based on the
equations of motion for spins and the memory-function presentation of magnetic
response where the main damping of the low-energy spin collective mode comes
from the decay into fermionic degrees of freedom. It is shown that the damping
function at low doping is closely related to the c-axis optical conductivity.
The analysis reproduces doping-dependent features of the resonant magnetic
scattering.
|
0211090v1
|
2002-11-20
|
Damping of Nodal Fermions Caused by a Dissipative Mode
|
Using a $d_{x^2 - y^2}$ superconductor in 2+1 dimensions we show that the
Nambu Goldstone fluctuations are replaced by dissipative excitations. We find
that the nodal quasi-particles damping is caused by the strong dissipative
excitations near the nodal points. As a result we find that the scattering
rates are linear in frequency and not cubic as predicted in the literature for
the ``d'' wave superconductors. Our results explain the recent angle resolved
photoemission spectroscopy and optical conductivity in the BSCCO high $T_c$
compounds.
|
0211440v1
|
2003-05-27
|
Dynamics of a classical gas including dissipative and mean field effects
|
By means of a scaling ansatz, we investigate an approximated solution of the
Boltzmann-Vlasov equation for a classical gas. Within this framework, we derive
the frequencies and the damping of the collective oscillations of a
harmonically trapped gas and we investigate its expansion after release of the
trap. The method is well suited to studying the collisional effects taking
place in the system and in particular to discussing the crossover between the
hydrodynamic and the collisionless regimes. An explicit link between the
relaxation times relevant for the damping of the collective oscillations and
for the expansion is established.
|
0305624v1
|
2003-07-21
|
Chaotic scattering of a quantum particle weakly coupled to a very complicated background
|
Effect of a complicated many-body environment is analyzed on the chaotic
motion of a quantum particle in a mesoscopic ballistic structure. The dephasing
and absorption phenomena are treated on the same footing in the framework of a
model which is free of the ambiguities inherent to earlier models. The
single-particle doorway resonance states excited via an external channel are
damped not only because of the escape onto such channels but also due to
ulterior population of long-lived background states, the resulting internal
damping being uniquely characterized by the spreading width. On the other hand,
the formation of the fine-structure resonances strongly enhances the delay time
fluctuations thus broadening the delay time distribution.
|
0307496v1
|
2003-09-24
|
Landau Damping in a 2D Electron Gas with Imposed Quantum Grid
|
Dielectric properties of semiconductor substrate with imposed two dimensional
(2D) periodic grid of quantum wires or nanotubes (quantum crossbars, QCB) are
studied. It is shown that a capacitive contact between QCB and semiconductor
substrate does not destroy the Luttinger liquid character of the long wave QCB
excitations. However, the dielectric losses of a substrate surface are
drastically modified due to diffraction processes on the QCB superlattice.
QCB-substrate interaction results in additional Landau damping regions of the
substrate plasmons. Their existence, form and the density of losses are
strongly sensitive to the QCB lattice constant.
|
0309546v2
|
2003-11-21
|
Self-stabilised fractality of sea-coasts through damped erosion
|
Erosion of rocky coasts spontaneously creates irregular seashores. But the
geometrical irregularity, in turn, damps the sea-waves, decreasing the average
wave amplitude. There may then exist a mutual self-stabilisation of the waves
amplitude together with the irregular morphology of the coast. A simple model
of such stabilisation is studied. It leads, through a complex dynamics of the
earth-sea interface, to the appearance of a stationary fractal seacoast with
dimension close to 4/3. Fractal geometry plays here the role of a morphological
attractor directly related to percolation geometry.
|
0311509v1
|
2003-12-10
|
Exciton-LO-phonon dynamics in InAs/GaAs quantum dots: Effects of zone-edge phonon damping
|
The dynamics of an exciton-LO-phonon system after an ultrafast optical
excitation in an InAs/GaAs quantum dot is studied theoretically. Influence of
anharmonic phonon damping and its interplay with the phonon dispersion is
analyzed. The signatures of the zone-edge decay process in the absorption
spectrum and time evolution are highlighted, providing a possible way of
experimental investigation on phonon anharmonicity effects.
|
0312256v2
|
2004-01-13
|
Vortex waves and the onset of turbulence in $^3$He-B
|
In a recent experiment Finne et al. discovered an intrinsic condition for the
onset of quantum turbulence in $^3$He-B, that q=alpha/(1-alpha')<1, where alpha
and alpha' are mutual friction parameters. The authors argued that this
condition corresponds to Kelvin waves which are marginally damped, so for q>1
Kelvin waves cannot grow in amplitude and trigger vortex reconnections and
turbulence. By analysing both axisymmetric and non-axisymmetric modes of
oscillations of a rotating superfluid, we confirm that in the long axial
wavelength limit the simple condition q=1 is indeed the crossover between
damped and propagating Kelvin waves.
|
0401212v1
|
2004-01-28
|
Long lived acoustic vibrational modes of an embedded nanoparticle
|
Classical continuum elastic calculations show that the acoustic vibrational
modes of an embedded nanoparticle can be lightly damped even when the
longitudinal plane wave acoustic impedances $Z_o=\rho v_L$ of the nanoparticle
and the matrix are the same. It is not necessary for the matrix to be less
dense or softer than the nanoparticle in order to have long lived vibrational
modes. Continuum boundary conditions do not always accurately reflect the
microscropic nature of the interface between nanoparticle and matrix, and a
multi-layer model of the interface reveals the possibility of additional
reduction of mode damping.
|
0401579v2
|
2004-07-20
|
Dynamics of a trapped ultracold two-dimensional atomic gas
|
This article is devoted to the study of two-dimensional Bose gases
harmonically confined. We first summarize their equilibrium properties. For
such a gas above the critical temperature, we also derive the frequencies and
the damping of the collective oscillations and we investigate its expansion
after releasing of the trap. The method is well suited to study the collisional
effects taking place in the system and in particular to discuss the crossover
between the hydrodynamic and the collisionless regimes. We establish the link
between the relaxation times relevant for the damping of the collective
oscillations and for the time-of-flight expansion. We also evaluate the
collision rate and its relationship with the relaxation time.
|
0407522v1
|
2004-12-06
|
Thermal wave packets induced by attosecond laser pulses
|
In this paper the dynamics of the interaction of attosecond laser pulses with
matter is investigated. It will be shown that the master equation: modified
Klein-Gordon equation describes the propagation of the heatons. Heatons are the
thermal wave packets. When the duration of the laser pulsees \delta t is of the
order of attosecond the heaton-thermal wave packets are nondispersive objects.
For \delta t \to \infty, the heatons are damped with damping factor of the
order of relaxation time for thermal processes.
Key words: Temperature fields; Attosecond laser pulses; Heatons; Modified
Klein-Gordon equation.
|
0412126v1
|
2005-04-12
|
Nonlinear response and discrete breather excitation in driven micro-mechanical cantilever arrays
|
We explain the origin of the generation of discrete breathers (DBs) in
experiments on damped and driven micromechanical cantilever arrays (M.Sato et
al. Phys. Rev. Lett. {\bf 90}, 044102, 2003). Using the concept of the
nonlinear response manifold (NLRM) we provide a systematic way to find the
optimal parameter regime in damped and driven lattices where DBs exist. Our
results show that DBs appear via a new instability of the NLRM different from
the anticipated modulational instability (MI) known for conservative systems.
We present several ways of exciting DBs, and compare also to experimental
studies of exciting and destroying DBs in antiferromagnetic layered systems.
|
0504298v1
|
2005-05-14
|
Monopole Oscillations and Dampings in Boson and Fermion Mixture in the Time-Dependent Gross-Pitaevskii and Vlasov Equations
|
We construct a dynamical model for the time evolution of the boson-fermion
coexistence system. The dynamics of bosons and fermions are formulated with the
time-dependent Gross-Pitaevsky equation and the Vlasov equation. We thus study
the monopole oscillation in the bose-fermi mixture. We find that large damping
exists for fermion oscillations in the mixed system even at zero temperature.
|
0505357v1
|
2005-10-13
|
Superconducting Flywheel Model for Energy Storage Applications
|
In order to explore the complexity and diversity of the flywheels' dynamics,
we have developed the real-physics computer model of a universal mechanical
rotor. Due to an arbitrary external force concept, the model can be adjusted to
operate identical to the real experimental prototype. Taking the high-speed
magnetic rotor on superconducting bearings as the prototype, the law for the
energy loss in real high temperature superconducting bearings has been derived.
Varying the laws of damping and elasticity in the system, we have found a way
to effectively damp the parasitic resonances and minimize the loss of energy
storage.
|
0510346v1
|
2005-11-05
|
Ratchet Effect in Magnetization Reversal of Stoner Particles
|
A new strategy is proposed aimed at substantially reducing the minimal
magnetization switching field for a Stoner particle. Unlike the normal method
of applying a static magnetic field which must be larger than the magnetic
anisotropy, a much weaker field, proportional to the damping constant in the
weak damping regime, can be used to switch the magnetization from one state to
another if the field is along the motion of the magnetization. The concept is
to constantly supply energy to the particle from the time-dependent magnetic
field to allow the particle to climb over the potential barrier between the
initial and the target states.
|
0511135v1
|
2005-12-03
|
Apparent vibrational side-bands in pi-conjugated systems: the case of distyrylbenzene
|
The photoluminescence (PL) spectra of dilute solution and single crystals of
distyrylbenzene show unique temperature dependent vibronic structures. The
characteristic single frequency progression at high temperatures is modulated
by a low frequency progression series at low temperatures. None of the series
side band modes corresponds to any of the distyrylbenzene Raman frequencies. We
explain these PL properties using a time dependent model with temperature
dependent damping, in which the many-mode system is effectively transformed to
two- and then to a single "apparent" mode as damping increases.
|
0512067v1
|
2006-05-26
|
Thermo-Plasma Polariton within Scaling Theory of Single-Layer Graphene
|
Electrodynamics of single-layer graphene is studied in the scaling regime. At
any finite temperature, there is a weakly damped collective thermo-plasma
polariton mode whose dispersion and wavelength dependent damping is determined
analytically. The electric and magnetic fields associated with this mode decay
exponentially in the direction perpendicular to the graphene layer, but unlike
the surface plasma polariton modes of metals, the decay length and the mode
frequency are strongly temperature dependent. This may lead to new ways of
generation and manipulation of these modes.
|
0605642v1
|
2006-12-18
|
Shear viscosity and damping for a Fermi gas in the unitarity limit
|
The shear viscosity of a two-component Fermi gas in the normal phase is
calculated as a function of temperature in the unitarity limit, taking into
account strong-coupling effects that give rise to a pseudogap in the spectral
density for single-particle excitations. The results indicate that recent
measurements of the damping of collective modes in trapped atomic clouds can be
understood in terms of hydrodynamics, with a decay rate given by the viscosity
integrated over an effective volume of the cloud.
|
0612460v2
|
2007-02-07
|
Damping of antiferromagnetic spin waves by valence fluctuations in the double layer perovskite YBaFe2O5
|
Inelastic neutron scattering experiments show that spin dynamics in the
charge ordered insulating ground state of the double-layer perovskite YBaFe2O5
is well described in terms of eg superexchange interactions. Above the Verwey
transition at TV = 308 K, t2g double exchange-type conduction within
antiferromagnetic FeO2--BaO--FeO2 double layers proceeds by an electron hopping
process that requires a spin flip of the five-fold coordinated Fe ions, costing
an energy 5<J>S^2 of approximately 0.1 eV. The hopping process disrupts
near-neighbor spin correlations, leading to massive damping of zone-boundary
spin waves.
|
0702181v1
|
2007-02-20
|
Spin Drag and Spin-Charge Separation in Cold Fermi Gases
|
Low-energy spin and charge excitations of one-dimensional interacting
fermions are completely decoupled and propagate with different velocities.
These modes however can decay due to several possible mechanisms. In this paper
we expose a new facet of spin-charge separation: not only the speeds but also
the damping rates of spin and charge excitations are different. While the
propagation of long-wavelength charge excitations is essentially ballistic,
spin propagation is intrinsically damped and diffusive. We suggest that cold
Fermi gases trapped inside a tight atomic waveguide offer the opportunity to
measure the spin-drag relaxation rate that controls the broadening of a spin
packet.
|
0702466v1
|
1996-07-23
|
Quasinormal modes of nearly extreme Reissner-Nordstrom black holes
|
We present detailed calculations of the quasinormal modes of
Reissner-Nordstrom black holes. While the first few, slowly damped, modes
depend on the charge of the black hole in a relatively simple way, we find that
the rapidly damped modes show several peculiar features. The higher modes
generally spiral into the value for the extreme black hole as the charge
increases. We also discuss the possible existence of a purely imaginary mode
for the Schwarzschild black hole: Our data suggest that there is a quasinormal
mode that limits to $\omega M = -2i$ as $Q\to 0$.
|
9607054v1
|
1996-08-22
|
Gravitational Ionization: A Chaotic Net in the Kepler System
|
The long term nonlinear dynamics of a Keplerian binary system under the
combined influences of gravitational radiation damping and external tidal
perturbations is analyzed. Gravitational radiation reaction leads the binary
system towards eventual collapse, while the external periodic perturbations
could lead to the ionization of the system via Arnold diffusion. When these two
opposing tendencies nearly balance each other, interesting chaotic behavior
occurs that is briefly studied in this paper. It is possible to show that
periodic orbits can exist in this system for sufficiently small damping.
Moreover, we employ the method of averaging to investigate the phenomenon of
capture into resonance.
|
9608054v1
|
1999-11-11
|
Inertial Control of the VIRGO Superattenuator
|
The VIRGO superattenuator (SA) is effective in depressing the seismic noise
below the thermal noise level above 4 Hz. On the other hand, the residual
mirror motion associated to the SA normal modes can saturate the dynamics of
the interferometer locking system. This motion is reduced implementing a
wideband (DC-5 Hz) multidimensional control (the so called inertial damping)
which makes use of both accelerometers and position sensors and of a DSP
system. Feedback forces are exerted by coil-magnet actuators on the top of the
inverted pendulum. The inertial damping is successful in reducing the mirror
motion within the requirements. The results are presented.
|
9911044v1
|
2002-04-29
|
Schwarzschild black holes and propagation of electromagnetic and gravitational waves
|
Disturbing of a spacetime geometry may result in the appearance of an
oscillating and damped radiation - the so-called quasinormal modes. Their
periods of oscillations and damping coefficients carry unique information about
the mass and the angular momentum, that would allow one to identify the source
of the gravitational field. In this talk we present recent bounds on the
diffused energy, applicable to the Schwarzschild spacetime, that give also
rough estimates of the energy of excited quasinormal modes.
|
0204086v1
|
2002-10-30
|
Massive charged scalar field in a Reissner-Nordstrom black hole background: quasinormal ringing
|
We compute characteristic (quasinormal) frequencies corresponding to decay of
a massive charged scalar field in a Reissner-Nordstrom black hole background.
It proves that, contrary to the behavior at very late times, at the stage of
quasinormal ringing the neutral perturbations will damp slower than the charged
ones. In the limit of the extremal black hole the damping rate of charged and
neutral perturbations coincides. Possible connection of this with the critical
collapse in a massive scalar electrodynamics is discussed.
|
0210105v3
|
2003-03-20
|
Dirac Quasi-Normal Modes in Schwarzschild Black Hole Spacetimes
|
We evaluate both the massless and the massive Dirac quasi-normal mode
frequencies in the Schwarzschild black hole spacetime using the WKB
approximation. For the massless case, we find that, similar to those for the
integral spin fields, the real parts of the frequencies increase with the
angular momentum number $\kappa$, while the imaginary parts or the dampings
increase with the mode number $n$ for fixed $\kappa$. For the massive case, the
oscillation frequencies increase with the mass $m$ of the field, while the
dampings decrease. Fields with higher masses will therefore decay more slowly.
|
0303078v1
|
2003-07-31
|
Effects of electrical charging on the mechanical Q of a fused silica disk
|
We report on the effects of an electrical charge on mechanical loss of a
fused silica disk. A degradation of Q was seen that correlated with charge on
the surface of the sample. We examine a number of models for charge damping,
including eddy current damping and loss due to polarization. We conclude that
rubbing friction between the sample and a piece of dust attracted by the
charged sample is the most likely explanation for the observed loss.
|
0308001v1
|
2004-09-15
|
Rippled Cosmological Dark Matter from Damped Oscillating Newton Constant
|
Let the reciprocal Newton 'constant' be an apparently non-dynamical
Brans-Dicke scalar field damped oscillating towards its General Relativistic
VEV. We show, without introducing additional matter fields or dust, that the
corresponding cosmological evolution averagely resembles, in the Jordan frame,
the familiar dark radiation -> dark matter -> dark energy domination sequence.
The fingerprints of our theory are fine ripples, hopefully testable, in the FRW
scale factor; they die away at the General Relativity limit. The possibility
that the Brans-Dicke scalar also serves as the inflaton is favorably examined.
|
0409059v2
|
2004-10-06
|
Thermoelastic-damping noise from sapphire mirrors in a fundamental-noise-limited interferometer
|
We report the first high-precision interferometer using large sapphire
mirrors, and we present the first direct, broadband measurements of the
fundamental thermal noise in these mirrors. Our results agree well with the
thermoelastic-damping noise predictions of Braginsky, et al. [Phys. Lett. A
264, 1(1999)] and Cerdonio, et al.[Phys. Rev. D 63, 082003 (2001)], which have
been used to predict the astrophysical reach of advanced interferometric
gravitational wave detectors.
|
0410028v1
|
2004-10-28
|
Gravitational waves from neutron stars described by modern EOS
|
The frequencies and damping times of neutron star (and quark star)
oscillations have been computed using the most recent equations of state
available in the literature. We find that some of the empirical relations that
connect the frequencies and damping times of the modes to the mass and radius
of the star, and that were previously derived in the literature need to be
modified.
|
0410140v1
|
2005-06-08
|
Resonant growth of stellar oscillations by incident gravitational waves
|
Stellar oscillation under the combined influences of incident gravitational
wave and radiation loss is studied in a simple toy model. The star is
approximated as a uniform density ellipsoid in the Newtonian gravity including
radiation damping through quadrupole formula. The time evolution of the
oscillation is significantly controlled by the incident wave amplitude $h$,
frequency $\nu$ and damping time $\tau$. If a combination $ h \nu \tau $
exceeds a threshold value, which depends on the resonance mode, the resonant
growth is realized.
|
0506047v1
|
2006-11-28
|
Massive scalar field quasinormal modes of a Schwarzschild black hole surrounded by quintessence
|
We present the quasinormal frequencies of the massive scalar field in the
background of a Schwarzchild black hole surrounded by quintessence with the
third-order WKB method. The mass of the scalar field $u$ plays an important
role in studying the quasinormal frequencies, the real part of the frequencies
increases linearly as mass $u$ increases, while the imaginary part in absolute
value decreases linearly which leads to damping more slowly and the frequencies
having a limited value. Moreover, owing to the presence of the quintessence,
the massive scalar field damps more slowly.
|
0611146v2
|
1992-09-24
|
Non-Abelian Boltzmann Equation for Mixing and Decoherence
|
We consider particle oscillations and their damping in second-quantized form.
We find that the damping or "decoherence" may be described by a Boltzmann-like
collision integral with "non-abelian blocking factors" (fermions). Earlier
results are generalized in that the momentum degrees of freedom are included
and that the mixing equations become intrinsically non-linear at high
densities.
|
9209276v1
|
1993-06-03
|
The heavy fermion damping rate puzzle
|
: We examine again the problem of the damping rate of a moving heavy fermion
in a hot plasma within the resummed perturbative theory of Pisarski and
Braaten. The ansatz for its evaluation which relates it to the imaginary part
of the fermion propagator pole in the framework of a self-consistent approach
is critically analyzed. As already pointed out by various authors, the only way
to define the rate is through additional implementation of magnetic screening.
We show in detail how the ansatz works in this case and where we disagree with
other authors. We conclude that the self-consistent approach is not
satisfactory.
|
9306219v1
|
1993-09-03
|
Damping Rate of a Fermion in a Medium
|
We examine the relation between the damping rate of a massless, chiral
fermion that propagates in a medium, and the rate $\Gamma$ of approach to
equilibrium. It is proven that these quantities are equal, by showing that they
are given by the same formula in terms of the imaginary part of the self-energy
evaluated at the energy of the propagating fermion mode. This result is valid
provided $\Gamma$ is defined by using the appropriate wave functions of the
mode.
|
9309225v2
|
1994-03-22
|
On the Damping Rate of a Fast Fermion in Hot QED
|
The self-consistent determination of the damping rate of a fast moving
fermion in a hot QED plasma is reexamined. We argue how a detailed
investigation of the analytic properties of the retarded fermion Green's
function motivated by the cutting rules at finite temperature may resolve
ambiguities related to the proper definition of the mass-shell condition.
|
9403335v1
|
1994-09-12
|
Fermion damping rate in a hot medium
|
In principle every excitation acquires a finite lifetime in a hot system.
This nonzero spectral width is calculated self-consistently for massive
fermions coupled to massless scalar, vector and pseudoscalar bosons. It is
shown that the self-consistent summation of the corresponding Fock diagram for
fermions eliminates all infrared divergences although the bosons are not
screened at all. Our solutions for the fermion damping rate are analytical in
the coupling constant, but not analytical in the temperature parameter around
T=0.
|
9409280v2
|
1994-09-22
|
Lyapunov Exponent and Plasmon Damping Rate in Nonabelian Gauge Theories
|
We explain why the maximal positive Lyapunov exponent of classical SU($N$)
gauge theory coincides with (twice) the damping rate of a plasmon at rest in
the leading order of thermal gauge theory. [This is a substantially revised and
expanded version of the manuscript.]
|
9409392v2
|
1994-12-20
|
Baryogenesis and damping in nonminimal electroweak models
|
We study the effect of damping on the generation of baryon asymmetry of the
Universe in the standard model of the eletroweak theory with simple extensions
of the Higgs sector. The propagation of quarks of masses up to about 5 GeV are
considered, taking into account their markedly different dispersion relations
due to interaction with the hot electroweak plasma. It is argued that the
contribution of the b quark can be comparable to that of the t quark calculated
earlier.
|
9412330v1
|
1998-10-07
|
Classical Kinetic Theory of Landau Damping for Self-interacting Scalar Fields in the Broken Phase
|
The classical kinetic theory of one-component self-interacting scalar fields
is formulated in the broken symmetry phase and applied to the phenomenon of
Landau damping. The domain of validity of the classical approach is found by
comparing with the result of a 1-loop quantum calculation.
|
9810278v2
|
1999-08-02
|
Plasma wave instabilities induced by neutrinos
|
Quantum field theory is applied to study the interaction of an electron
plasma with an intense neutrino flux. A connection is established between the
field theory results and classical kinetic theory. The dispersion relation and
damping rate of the plasma longitudinal waves are derived in the presence of
neutrinos. It is shown that Supernova neutrinos are never collimated enough to
cause non-linear effects associated with a neutrino resonance. They only induce
neutrino Landau damping, linearly proportional to the neutrino flux and
$G_{\mathrm{F}}^{2}$.
|
9908206v2
|
1999-09-27
|
Radiation Damping at a Bubble Wall
|
The first order phase transition proceeds via nucleation and growth of true
vacuum bubbles. When charged particles collide with the bubble they could
radiate electromagnetic wave. We show that, due to an energy loss of the
particles by the radiation, the damping pressure acting on the bubble wall
depends on the velocity of the wall even in a thermal equilibrium state.
|
9909521v1
|
1999-10-08
|
Lifetime of Collective Isospin Rotations of a Quantum Meson Field
|
We calculate the lifetime of the collective isospin rotating solutions which
have been found recently in the case a quantum N-component meson field with
exact O(N) symmetry. For this purpose we take into account the small breaking
of the O(N) symmetry associated to the non vanishing mass of the pion. This
term induces a coupling between collective rotations and intrinsic meson
excitations. We evaluate the associated damping time in the framework of linear
response theory. We find damping times of the order of 100 fm/c, i.e.
substantially longer than reaction times.
|
9910276v1
|
2000-02-08
|
Finite pion width effects on the rho-meson and di-lepton spectra
|
Within a field theoretical model where all damping width effects are treated
self-consistently we study the changes of the spectral properties of rho-mesons
due to the finite damping width of the pions in dense hadronic matter at finite
temperature. The corresponding effects in the di-lepton yields are presented.
Some problems concerning the self consistent treatment of vector or gauge
bosons are discussed.
|
0002087v1
|
2000-08-31
|
Damping of very soft moving quarks in high-temperature QCD
|
We determine the analytic expression of the damping rates for very soft
moving quarks in an expansion to second order in powers of their momentum in
the context of QCD at high temperature. The calculation is performed using the
hard-thermal-loop-summed perturbation scheme. We describe the range of validity
of the expansion and make a comparison with other calculations, particularly
those using a magnetic mass as a shield from infrared sensitivity. We discuss
the possible occurrence of infrared divergences in our results and argue that
they are due to magnetic sensitivity.
|
0008335v1
|
2000-09-27
|
Damping of the HERA effect in DIS?
|
The drastic rise of the proton structure function F_2(x,Q^2) when the
Bj\"orken variable x decreases, seen at HERA for a large span of Q^2, negative
values for the 4-momentum transfer, may be damped when Q^2 increases beyond
several hundreds GeV^2. A new data analysis and a comparison with recent models
for the proton structure function is proposed to discuss this phenomenon in
terms of the derivative \partial ln F_2(x,Q^2)/\partial ln(1/x).
|
0009313v2
|
2001-12-13
|
Time evolution in linear response: Boltzmann equations and beyond
|
In this work a perturbative linear response analysis is performed for the
time evolution of the quasi-conserved charge of a scalar field. One can find
two regimes, one follows exponential damping, where the damping rate is shown
to come from quantum Boltzmann equations. The other regime (coming from
multiparticle cuts and products of them) decays as power law. The most
important, non-oscillating contribution in our model comes from a 4-particle
intermediate state and decays as 1/t^3. These results may have relevance for
instance in the context of lepton number violation in the Early Universe.
|
0112188v1
|
2002-04-26
|
Oscillation damping of chiral string loops
|
Chiral cosmic string loop tends to the stationary (vorton) configuration due
to the energy loss into the gravitational and electromagnetic radiation. We
describe the asymptotic behaviour of near stationary chiral loops and their
fading to vortons. General limits on the gravitational and electromagnetic
energy losses by near stationary chiral loops are found. For these loops we
estimate the oscillation damping time. We present solvable examples of
gravitational radiation energy loss by some chiral loop configurations. The
analytical dependence of string energy with time is found in the case of the
chiral ring with small amplitude radial oscillations.
|
0204304v1
|
2002-09-21
|
Infrared Sensitivity in Damping Rate for Very Soft Moving Fermions in Finite Temperature QED
|
We calculate the fermion damping rate to second order in powers of the
external momentum $p$ in the context of QED at finite temperature using the
hard-thermal-loop (HTL) summation scheme. We find that the coefficient of order
$p^{2}$ is divergent in the infrared whereas the two others are finite. This
result suggests that the htl-based pertubation is infrared sensitive at
next-to-leading order.
|
0209246v1
|
2004-02-06
|
Critical Behavior of Damping Rate for Plasmon with Finite Momentum in φ^4 Theory
|
Applying thermal renormalization group (TRG) equations to $\phi^4$ theory
with spontaneous breaking symmetry, we investigate the critical behavior of the
damping rate for the plasmons with finite momentum at the symmetry-restoring
phase transition. From the TRG equation the IR cutoff provided by the external
momentum leads to that the momentum-dependent coupling constant stops running
in the critical region. As the result, the critical slowing down phenomenon
reflecting the inherently IR effect doesn't take place at the critical point
for the plasmon with finite external momentum.
|
0402069v2
|
2005-11-22
|
Ultrasoft Quark Damping in Hot QCD
|
We determine the quark damping rates in the context of next-to-leading order
hard-thermal-loop summed perturbation of high-temperature QCD where weak
coupling is assumed. The quarks are ultrasoft. Three types of divergent
behavior are encountered: infrared, light-cone and at specific points
determined by the gluon energies. The infrared divergence persists and is
logarithmic whereas the two others are circumvented.
|
0511258v1
|
2006-03-10
|
Numerical Approach to Multi Dimensional Phase Transitions
|
We present an algorithm to analyze numerically the bounce solution of
first-order phase transitions. Our approach is well suited to treat phase
transitions with several fields. The algorithm consists of two parts. In the
first part the bounce solution without damping is determined, in which case
energy is conserved. In the second part the continuation to the physically
relevant case with damping is performed. The presented approach is numerically
stable and easily implemented.
|
0603081v2
|
1994-06-22
|
Damped quantum harmonic oscillator: density operator and related quantities
|
A closed expression for the density operator of the damped harmonic
oscillator is extracted from the master equation based on the Lindblad theory
for open quantum systems. The entropy and effective temperature of the system
are subsequently calculated and their temporal behaviour is surveyed by showing
how these quantities relax to their equilibrium values. The entropy for a state
characterized by a Wigner distribution function which is Gaussian in form is
found to depend only on the variance of the distribution function.
|
9406142v1
|
1997-05-09
|
Radiation Damping of a BPS Monopole; an Implication to S-duality
|
The radiation reaction of a BPS monopole in the presence of incident
electromagnetic waves as well as massless Higgs waves is analyzed classically.
The reactive forces are compared to those of $W$ boson that is interpreted as a
dual partner of the BPS monopole. It is shown that the damping of acceleration
is dual to each other, while in the case of finite size effects the duality is
broken explicitly. Their implications on the duality are discussed.
|
9705059v2
|
1997-07-02
|
The Asymptotic Method Developed from Weak Turbulent Theory and the Nonlinear Permeability and Damping Rate in QGP
|
With asymptotic method developed from weak turbulent theory, the kinetic
equations for QGP are expanded in fluctuation field potential $A^T_\mu $.
Considering the second-order and third-order currents, we derive the nonlinear
permeability tensor function from Yang-Mills field equation, and find that the
third-order current is more important in turbulent theory. The nonlinear
permeability formulae for longitudinal color oscillations show that the
non-Abelian effects are more important than the Abelian-like effects. To
compare with other works, we give the numerical result of the damping rate for
the modes with zero wave vector.
|
9707052v1
|
2005-04-07
|
Continuous area spectrum in regular black hole
|
We investigate highly damped quasinormal modes of regular black hole coupled
to nonlinear electrodynamics. Using the WKB approximation combined with
complex-integration technique, we show that the real part of the frequency
disappears in the highly damped limit. If we use the Bohr's correspondence
principle, the area spectrum of this black hole is continuous. We discuss its
implication in the loop quantum gravity.
|
0504059v2
|
2005-05-16
|
Supersymmetrization of the Radiation Damping
|
We construct a supersymmetrized version of the model to the radiation damping
\cite{03} introduced by the present authors \cite{ACWF}. We dicuss its
symmetries and the corresponding conserved Noether charges. It is shown this
supersymmetric version provides a supersymmetric generalization of the Galilei
algebra obtained in \cite{ACWF}. We have shown that the supersymmetric action
can be splited into dynamically independent external and internal sectors.
|
0505142v1
|
1999-08-16
|
Topological Entropy and epsilon-Entropy for Damped Hyperbolic Equations
|
We study damped hyperbolic equations on the infinite line. We show that on
the global attracting set $G$ the $\epsilon$-entropy (per unit length) exists
in the topology of $W^{1,\infty}$. We also show that the topological entropy
per unit length of $G$ exists. These results are shown using two main
techniques: Bounds in bounded domains in position space and for large momenta,
and a novel submultiplicativity argument in $W^{1,\infty}$.
|
9908080v1
|
2003-11-28
|
Uniform stability of damped nonlinear vibrations of an elastic string
|
Here we are concerned about uniform stability of damped nonlinear transverse
vibrations of an elastic string fixed at its two ends. The vibrations governed
by nonlinear integro-differential equation of Kirchoff type, is shown to
possess energy uniformly bounded by exponentially decaying function of time.
The result is achieved by considering an energy-like Lyapunov functional for
the system.
|
0311527v1
|
2005-07-06
|
On stability and stabilization of elastic systems by time-variant feedback
|
We study a class of elastic systems described by a (hyperbolic) partial
differential equation. Our working example is the equation of a vibrating
string subject to linear disturbance. The main goal is to establish conditions
for stabilization and asymptotic stabilization by applying a fast oscillating
control to the string. In the first situation studied we assume that system is
subject to a damping force; next we consider the system without damping. We
extend the tools of high-order averaging and of chronological calculus for
studying stability of this distributed parameter system.
|
0507123v1
|
2006-01-13
|
Attractors for damped hyperbolic equations on arbitrary unbounded domains
|
We prove existence of global attractors for damped hyperbolic equations of
the form $$\aligned \eps u_{tt}+\alpha(x) u_t+\beta(x)u- \sum_{ij}(a_{ij}(x)
u_{x_j})_{x_i}&=f(x,u),\quad x\in \Omega, t\in[0,\infty[, u(x,t)&=0,\quad x\in
\partial \Omega, t\in[,\infty[.\endaligned$$ on an unbounded domain $\Omega$,
without smoothness assumptions on $\beta(\cdot)$, $a_{ij}(\cdot)$, $f(\cdot,u)$
and $\partial\Omega$, and $f(x,\cdot)$ having critical or subcritical growth.
|
0601319v3
|
2007-02-07
|
Finite time blow-up results for the damped wave equations with arbitrary initial energy in an inhomogeneous medium
|
In this paper we consider the long time behavior of solutions of the initial
value problem for the damped wave equation of the form \begin{eqnarray*}
u_{tt}-\rho(x)^{-1}\Delta u+u_t+m^2u=f(u) \end{eqnarray*} with some $\rho(x)$
and $f(u)$ on the whole space $\R^n$ ($n\geq 3$).
For the low initial energy case, which is the non-positive initial energy,
based on concavity argument we prove the blow up result. As for the high
initial energy case, we give out sufficient conditions of the initial datum
such that the corresponding solution blows up in finite time.
|
0702190v1
|
2007-03-09
|
Analyticity and Riesz basis property of semigroups associated to damped vibrations
|
Second order equations of the form $z'' + A_0 z + D z'=0$ in an abstract
Hilbert space are considered. Such equations are often used as a model for
transverse motions of thin beams in the presence of damping. We derive various
properties of the operator matrix $A$ associated with the second order problem
above. We develop sufficient conditions for analyticity of the associated
semigroup and for the existence of a Riesz basis consisting of eigenvectors and
associated vectors of $A$ in the phase space.
|
0703247v1
|
2007-03-21
|
Existence and asymptotic behavior of $C^1$ solutions to the multidimensional compressible Euler equations with damping
|
In this paper, the existence and asymptotic behavior of $C^1$ solutions to
the multidimensional compressible Euler equations with damping on the framework
of Besov space are considered. We weaken the regularity requirement of the
initial data, and improve the well-posedness results of Sideris-Thomases-Wang
(Comm.P.D.E. 28 (2003) 953). The global existence lies on a crucial a-priori
estimate which is proved by the spectral localization method. The main analytic
tools are the Littlewood-Paley decomposition and Bony's para-product formula.
|
0703621v1
|
2000-12-22
|
The Vlasov-Poisson system with radiation damping
|
We set up and analyze a model of radiation damping within the framework of
continuum mechanics, inspired by a model of post-Newtonian hydrodynamics due to
Blanchet, Damour and Schaefer. In order to simplify the problem as much as
possible we replace the gravitational field by the electromagnetic field and
the fluid by kinetic theory. We prove that the resulting system has a
well-posed Cauchy problem globally in time for general initial data and in all
solutions the fields decay to zero at late times. In particular, this means
that the model is free from the runaway solutions which frequently occur in
descriptions of radiation reaction.
|
0012041v1
|
2003-01-17
|
Quantum mechanics of damped systems
|
We show that the quantization of a simple damped system leads to a
self-adjoint Hamiltonian with a family of complex generalized eigenvalues. It
turns out that they correspond to the poles of energy eigenvectors when
continued to the complex energy plane. Therefore, the corresponding generalized
eigenvectors may be interpreted as resonant states. We show that resonant
states are responsible for the irreversible quantum dynamics of our simple
model.
|
0301024v3
|
2003-07-23
|
Quantum Mechanics of Damped Systems II. Damping and Parabolic Potential Barrier
|
We investigate the resonant states for the parabolic potential barrier known
also as inverted or reversed oscillator. They correspond to the poles of
meromorphic continuation of the resolvent operator to the complex energy plane.
As a byproduct we establish an interesting relation between parabolic cylinder
functions (representing energy eigenfunctions of our system) and a class of
Gel'fand distributions used in our recent paper.
|
0307047v1
|
2001-07-02
|
Pattern formation and localization in the forced-damped FPU lattice
|
We study spatial pattern formation and energy localization in the dynamics of
an anharmonic chain with quadratic and quartic intersite potential subject to
an optical, sinusoidally oscillating field and a weak damping. The
zone-boundary mode is stable and locked to the driving field below a critical
forcing that we determine analytically using an approximate model which
describes mode interactions. Above such a forcing, a standing modulated wave
forms for driving frequencies below the band-edge, while a ``multibreather''
state develops at higher frequencies. Of the former, we give an explicit
approximate analytical expression which compares well with numerical data. At
higher forcing space-time chaotic patterns are observed.
|
0107002v1
|
2003-06-16
|
On the influence of noise on chaos in nearly Hamiltonian systems
|
The simultaneous influence of small damping and white noise on Hamiltonian
systems with chaotic motion is studied on the model of periodically kicked
rotor. In the region of parameters where damping alone turns the motion into
regular, the level of noise that can restore the chaos is studied. This
restoration is created by two mechanisms: by fluctuation induced transfer of
the phase trajectory to domains of local instability, that can be described by
the averaging of the local instability index, and by destabilization of motion
within the islands of stability by fluctuation induced parametric modulation of
the stability matrix, that can be described by the methods developed in the
theory of Anderson localization in one-dimensional systems.
|
0306024v1
|
2003-07-30
|
Faraday Wave Pattern Selection Via Multi-Frequency Forcing
|
We use symmetry considerations to investigate how damped modes affect pattern
selection in multi-frequency forced Faraday waves. We classify and tabulate the
most important damped modes and determine how the corresponding resonant triad
interactions depend on the forcing parameters. The relative phase of the
forcing terms may be used to enhance or suppress the nonlinear interactions. We
compare our predictions with numerical results and discuss their implications
for recent experiments. Our results suggest how to design multi-frequency
forcing functions that favor chosen patterns in the lab.
|
0307056v1
|
2004-10-11
|
Nodal two-dimensional solitons in nonlinear parametric resonance
|
The parametrically driven damped nonlinear Schr\"odinger equation serves as
an amplitude equation for a variety of resonantly forced oscillatory systems on
the plane. In this note, we consider its nodal soliton solutions. We show that
although the nodal solitons are stable against radially-symmetric perturbations
for sufficiently large damping coefficients, they are always unstable to
azimuthal perturbations. The corresponding break-up scenarios are studied using
direct numerical simulations. Typically, the nodal solutions break into
symmetric "necklaces" of stable nodeless solitons.
|
0410012v1
|
2004-10-21
|
Stabilization mechanism for two-dimensional solitons in nonlinear parametric resonance
|
We consider a simple model system supporting stable solitons in two
dimensions. The system is the parametrically driven damped nonlinear
Schr\"odinger equation, and the soliton stabilises for sufficiently strong
damping. The purpose of this note is to elucidate the stabilisation mechanism;
we do this by reducing the partial differential equation to a
finite-dimensional dynamical system. Our conclusion is that the negative
feedback loop occurs via the enslaving of the soliton's phase, locked to the
driver, to its amplitude and width.
|
0410044v1
|
2006-01-14
|
Vibration of the Duffing Oscillator: Effect of Fractional Damping
|
We have applied the Melnikov criterion to examine a global homoclinic
bifurcation and transition to chaos in a case of the Duffing system with
nonlinear fractional damping and external excitation.
Using perturbation methods we have found a critical forcing amplitude above
which the system may behave chaotically.
The results have been verified by numerical simulations using standard
nonlinear tools as
Poincare maps and a Lyapunov exponent. Above the critical Melnikov amplitude
$\mu_c$, which is the sufficient condition of a global homoclinic bifurcation,
we have observed the region with a transient chaotic motion.
|
0601033v1
|
2006-10-22
|
Response of a Magneto-Rheological Fluid Damper Subjected to Periodic Forcing in a High Frequency Limit
|
We explored vibrations of a single-degree of freedom oscillator with a
magneto-rheological damper subjected to kinematic excitations. Using fast and
slow scales decoupling procedure we derived an effective damping coefficient in
the limit of high frequency excitation. Damping characteristics, as functions
of velocity, change considerably especially by terminating the singular
non-smoothness points. This effect was more transparent for a larger control
parameter which was defined as the product of the excitation amplitude and its
frequency.
|
0610055v1
|
2006-11-02
|
Solitons in strongly driven discrete nonlinear Schrödinger-type models
|
Discrete solitons in the Ablowitz-Ladik (AL) and discrete nonlinear
Schr\"odinger (DNLS) equations with damping and strong rapid drive are
investigated. The averaged equations have the forms of the parametric AL and
DNLS equations. A new type of parametric bright discrete soliton and cnoidal
waves are found and the stability properties are analyzed. The analytical
predictions of the perturbed inverse scattering transform are confirmed by the
numerical simulations of the AL and DNLS equations with rapidly varying drive
and damping.
|
0611004v1
|
2006-11-26
|
On the Lagrangian and Hamiltonian description of the damped linear harmonic oscillator
|
Using the modified Prelle- Singer approach, we point out that explicit time
independent first integrals can be identified for the damped linear harmonic
oscillator in different parameter regimes. Using these constants of motion, an
appropriate Lagrangian and Hamiltonian formalism is developed and the resultant
canonical equations are shown to lead to the standard dynamical description.
Suitable canonical transformations to standard Hamiltonian forms are also
obtained. It is also shown that a possible quantum mechanical description can
be developed either in the coordinate or momentum representations using the
Hamiltonian forms.
|
0611048v1
|
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