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2023-03-30 | Fate of entanglement in magnetism under Lindbladian or non-Markovian dynamics and conditions for their transition to Landau-Lifshitz-Gilbert classical dynamics | It is commonly assumed in spintronics and magnonics that localized spins
within antiferromagnets are in the N\'{e}el ground state (GS), as well as that
such state evolves, when pushed out of equilibrium by current or external
fields, according to the Landau-Lifshitz-Gilbert (LLG) equation viewing
localized spins as classical vectors of fixed length. On the other hand, the
true GS of antiferromagnets is highly entangled, as confirmed by very recent
neutron scattering experiments witnessing their entanglement. Although GS of
ferromagnets is always unentangled, their magnonic low-energy excitation are
superpositions of many-body spin states and, therefore, entangled. In this
study, we initialize quantum Heisenberg ferro- or antiferromagnetic chains
hosing localized spins $S=1/2$, $S=1$ or $S=5/2$ into unentangled pure state
and then evolve them by quantum master equations (QMEs) of Lindblad or
non-Markovian type, derived by coupling localized spins to a bosonic bath (such
as due to phonons) or by using additional ``reaction coordinate'' in the latter
case. The time evolution is initiated by applying an external magnetic field,
and entanglement of time-evolving {\em mixed} quantum states is monitored by
computing its logarithmic negativity. We find that non-Markovian dynamics
maintains some degree of entanglement, which shrinks the length of the vector
of spin expectation values, thereby making the LLG equation inapplicable.
Conversely, Lindbladian (i.e., Markovian) dynamics ensures that entanglement
goes to zero, thereby enabling quantum-to-classical (i.e., to LLG) transition
in all cases -- $S=1/2$, $S=1$ and $S=5/2$ ferromagnet or $S=5/2$
antiferromagnet -- {\em except} for $S=1/2$ and $S=1$ antiferromagnet. We also
investigate the stability of entangled antiferromagnetic GS upon suddenly
coupling it to the bosonic bath. | 2303.17596v3 |
2024-02-07 | Item-Level Heterogeneous Treatment Effects of Selective Serotonin Reuptake Inhibitors (SSRIs) on Depression: Implications for Inference, Generalizability, and Identification | In analysis of randomized controlled trials (RCTs) with patient-reported
outcome measures (PROMs), Item Response Theory (IRT) models that allow for
heterogeneity in the treatment effect at the item level merit consideration.
These models for ``item-level heterogeneous treatment effects'' (IL-HTE) can
provide more accurate statistical inference, allow researchers to better
generalize their results, and resolve critical identification problems in the
estimation of interaction effects. In this study, we extend the IL-HTE model to
polytomous data and apply the model to determine how the effect of selective
serotonin reuptake inhibitors (SSRIs) on depression varies across the items on
a depression rating scale. We first conduct a Monte Carlo simulation study to
assess the performance of the polytomous IL-HTE model under a range of
conditions. We then apply the IL-HTE model to item-level data from 28 RCTs
measuring the effect of SSRIs on depression using the 17-item Hamilton
Depression Rating Scale (HDRS-17) and estimate potential heterogeneity by
subscale (HDRS-6). Our results show that the IL-HTE model provides more
accurate statistical inference, allows for generalizability of results to
out-of-sample items, and resolves identification problems in the estimation of
interaction effects. Our empirical application shows that while the average
effect of SSRIs on depression is beneficial (i.e., negative) and statistically
significant, there is substantial IL-HTE, with estimates of the standard
deviation of item-level effects nearly as large as the average effect. We show
that this substantial IL-HTE is driven primarily by systematically larger
effects on the HDRS-6 subscale items. The IL-HTE model has the potential to
provide new insights for the inference, generalizability, and identification of
treatment effects in clinical trials using patient reported outcome measures. | 2402.04487v1 |
1995-02-16 | Lyman alpha Emission from High-Redshift Galaxies | We summarise the results of a deep search for Lyman alpha emission from
star-forming regions associated with damped Lyman alpha absorption systems and
conclude that the Lyman alpha luminosity of high redshift galaxies is generally
less than 10^(42) erg/s . We also present a newly discovered case, in the field
of the QSO Q2059-360, where the emission is unusually strong, possibly because
the damped system is close in redshift to the QSO. | 9502076v1 |
1995-10-12 | Limits on diffusive shock acceleration in dense and incompletely ionised media | The limits imposed on diffusive shock acceleration by upstream ion-neutral
Alfven wave damping, and by ionisation and Coulomb losses of low energy
particles, are calculated. Analytic solutions are given for the steady upstream
wave excitation problem with ion-neutral damping and the resulting escaping
upstream flux calculated. The time dependent problem is discussed and numerical
solutions presented. Finally the significance of these results for possible
observational tests of shock acceleration in supernova remnants is discussed. | 9510066v2 |
1995-11-28 | Damping of GRR instability by direct URCA reactions | The role of direct URCA reactions in damping of the gravitational radiation
driven instability is discussed. The temperature at which bulk viscosity
suppresses completely this instability is calculated.
The results are obtained analytically using recent calculations performed in
the case of bulk viscosity due to the modified URCA processes (Lindblom 1995;
Yoshida & Eriguchi 1995).
The bulk viscosity caused by direct URCA reactions is found to reduce
significantly the region of temperatures and rotation frequencies where a
neutron star is subject to GRR instability. | 9511136v1 |
1997-10-31 | Abundances in Damped Lyman-alpha Systems and Chemical Evolution of High Redshift Galaxies | Recent abundance measurements in damped Lyman-alpha galaxies, supplemented
with unpublished Keck observations, are discussed. The metallicity distribution
with cosmic time is examined for clues about the degree of enrichment, the
onset of initial star formation, and the nature of the galxies. The relative
abundances of the elements are compared with the abundnce pattern in Galactic
halo stars and in the Sun, taking into account of the effects of dust
depletion, in order to gain insight into the stellar processes and the time
scales by which the enrichment occurred. | 9710370v1 |
1998-05-08 | Exploring the Damped Lyman-alpha Clouds with AXAF | The High Energy Transmission Grating (HETG) Spectrometer on the Advanced
X-ray Astrophysics Facility (AXAF) (scheduled for launch in August, 1998) will
provide a new tool for the study of absorption in the X-ray spectra of high
redshift quasars due to the material along the line of sight. In this paper we
try to explore the possibility of using AXAF HETG to detect resonance
absorption lines from the Damped Lyman-alpha (DLA) clouds. | 9805110v1 |
1998-05-28 | Photon Damping of Waves in Accretion Disks | MHD turbulence is generally believed to have two important functions in
accretion disks: it transports angular momentum outward, and the energy in its
shortest wavelength modes is dissipated into the heat that the disks radiate.
In this paper we examine a pair of mechanisms which may play an important role
in regulating the amplitude and spectrum of this turbulence: photon diffusion
and viscosity. We demonstrate that in radiation pressure-dominated disks,
photon damping of compressive MHD waves is so rapid that it likely dominates
all other dissipation mechanisms. | 9805358v1 |
1998-06-11 | Damping of differential rotation in neutron stars | We derive the transport relaxation times for quasiparticle-vortex scattering
processes via nuclear force, relevant for the damping of differential rotation
of superfluids in the quantum liquid core of a neutron star. The proton
scattering off the neutron vortices provides the dominant resistive force on
the vortex lattice at all relevant temperatures in the phase where neutrons
only are in the paired state. If protons are superconducting, a small fraction
of hyperons and resonances in the normal state would be the dominant source of
friction on neutron and proton vortex lattices at the core temperatures $T\ge
10^{7}$ K. | 9806156v1 |
1999-03-10 | Elemental abundances at early times: the nature of Damped Lyman-alpha systems | The distribution of element abundances with redshift in Damped Ly-alpha (DLA)
systems can be adequately reproduced by the same model reproducing the halo and
disk components of the Milky Way Galaxy at different galactocentric distances:
DLA systems are well represented by normal spiral galaxies in their early
evolutionary stages. | 9903150v1 |
1999-07-26 | Are Damped Ly-alpha Systems Large, Galactic Disks ? | The hypothesis that the Damped Ly-alpha systems (DLAs) are large, galactic
disks (Milky Way sized) is tested by confronting predictions of models of the
formation and evolution of (large) disk galaxies with observations, in
particular the Zinc abundance distribution with neutral hydrogen column density
found for DLAs. A pronounced mismatch is found strongly hinting that the
majority of DLAs may not be large, galactic disks. | 9907349v1 |
1999-11-25 | Probing Solar Convection | In the solar convection zone acoustic waves are scattered by turbulent sound
speed fluctuations. In this paper the scattering of waves by convective cells
is treated using Rytov's technique. Particular care is taken to include
diffraction effects which are important especially for high-degree modes that
are confined to the surface layers of the Sun. The scattering leads to damping
of the waves and causes a phase shift. Damping manifests itself in the width of
the spectral peak of p-mode eigenfrequencies. The contribution of scattering to
the line widths is estimated and the sensitivity of the results on the assumed
spectrum of the turbulence is studied. Finally the theoretical predictions are
compared with recently measured line widths of high-degree modes. | 9911469v1 |
1999-12-14 | The Gas Reservoir for present day Galaxies : Damped Ly-alpha Absorption Systems | We present results from an ongoing search for galaxy counterparts of a
subgroup of Quasar Absorption Line Systems called Damped Ly-alpha Absorbers
(DLAs). DLAs have several characteristics that make them essential in the
process of understanding how galaxies formed in the early universe and evolved
to the galaxies we see today in the local universe.
Finally we compare DLAs with recent findings of a population of starforming
galaxies at high redshifts, so called Lyman-break galaxies. | 9912268v1 |
2000-06-22 | Nuclear Reaction Rates in a Plasma: The Effect of Highly Damped Modes | The fluctuation-dissipation theorem is used to evaluate the screening factor
of nuclear reactions due to the electromagnetic fluctuations in a plasma. We
show that the commonly used Saltpeter factor is obtained if only fluctuations
near the plasma eigenfrequency are assumed to be important (\omega \sim
\omega_{pe}\ll T (\hbar=k_{B}=1)). By taking into account all the fluctuations,
the highly damped ones, with \omega >\omega_{pe}, as well as those with
\omega\leq\omega_{pe}, we find that nuclear reaction rates are higher than
those obtained using the Saltpeter factor, for many interesting plasmas. | 0006326v1 |
2001-01-13 | Measuring Feedback in Damped Lyman Alpha Systems | We measure feedback (heating rates) in damped Lyman alpha systems from the
cooling rate of the neutral gas. Since cooling occurs through [C II] 158 micron
emission, we infer cooling from C II^{*} 1335.7 absorption lines detected with
HIRES on the Keck I telescope. The inferred heating rates are about 30 times
lower than for the Galaxy ISM. At z = 2.8, the implied star formation rate per
unit area is 10^{-2.4+-0.3} solar masses per kpc^{2} per year, and the the star
formation rate per unit comoving volume is 10^{-0.8+-0.2} solar masses per
Mpc^{3} per year. This is the first measurement of star formation rates in
objects likely to be the progenitors of current galaxies. | 0101218v1 |
2001-04-18 | The First Detection of Cobalt in a Damped Lyman Alpha System | We present the first ever detection of Cobalt in a Damped Lyman Alpha system
(DLA) at z = 1.92. In addition to providing important clues to the star
formation history of these high redshift galaxies, we discuss how studying the
Co abundance in DLAs may also help to constrain models of stellar
nucleosynthesis in a regime not probed by Galactic stars. | 0104301v1 |
2001-05-09 | Nuclear reaction rates and energy in stellar plasmas : The effect of highly damped modes | The effects of the highly damped modes in the energy and reaction rates in a
plasma are discussed. These modes, with wavenumbers $k \gg k_{D}$, even being
only weakly excited, with less than $k_{B}T$ per mode, make a significant
contribution to the energy and screening in a plasma. When the de Broglie
wavelength is much less than the distance of closest approach of thermal
electrons, a classical analysis of the plasma can | 0105153v1 |
2001-07-03 | The HI Content and Extent of Low Surface Brightness Galaxies - Could LSB Galaxies be Responsible for Damped Ly-alpha Absorption? | Low surface brightness galaxies, those galaxies with a central surface
brightness at least one magnitude fainter than the night sky, are often not
included in discussions of extragalactic gas at z < 0.1. In this paper we
review many of the properties of low surface brightness galaxies, including
recent studies which indicate low surface brightness systems may contribute far
more to the local HI luminosity function than previously thought. Additionally,
we use the known (HI) gas properties of low surface brightness galaxies to
consider their possible contribution to nearby damped Lyman-alpha absorbers. | 0107064v1 |
2001-09-10 | H_2 molecules in damped systems | Damped Lyman alpha systems seen in the spectra of high-z QSOs arise in
high-density neutral gas in which molecular hydrogen (H_2) should be
conspicuous. Systematic searches to detect the H_2 lines redshifted into the
Lyman alpha forest at <3400\AA are now possible thanks to the unique
capabilities of UVES on the VLT. Here we summarise the present status of our on
going programme to search for H_2 in DLAs, discuss the physical conditions in
the systems where H_2 is detected and the implications of non-detections. | 0109155v1 |
2001-10-23 | A scaling law of interstellar depletions as a tool for abundance studies of Damped Ly alpha systems | An analytical expression is presented that allows dust depletions to be
estimated in different types of interstellar environments, including Damped Ly
alpha systems. The expression is a scaling law of a reference depletion pattern
and takes into account the possibility that the dust chemical composition may
vary as a function of the dust-to-metals ratio and of the intrinsic abundances
of the medium. Preliminary tests and applications of the proposed scaling law
are briefly reported. | 0110499v1 |
2002-09-23 | Outflows in Galaxies and Damped Ly-alpha System | Although quasar absorbers, and in particular Damped Lyman-alpha systems
(DLAs) have proven a valuable tool to study the early Universe, their exact
nature is so far poorly constrained. It has been suggested that outflows in
galaxies might account for at least part of the DLA population. Observational
evidences and models in support of this hypothesis are reviewed, including
recent observations of Lyman Break Galaxies (LBGs). Observational
counter-arguments and theoretical limitations are also given. Finally,
implications of such a model for the environment of galaxies at high-redshifts
are discussed. | 0209463v1 |
2004-03-15 | The Damping Wing of the Gunn-Peterson Absorption and Lyman-Alpha Emitters in the Pre-Reionization Era | We use a numerical simulation of cosmological reionization to estimate the
likelihood of detecting Lyman-alpha emitting galaxies during the
pre-reionization era. We show that it is possible to find galaxies even at z~9
that are barely affected by the dumping wing of the Gunn-Peterson absorption
from the neutral IGM outside of their HII regions. The damping wing becomes
rapidly more significant at z>9, but even at z>10 is it not inconceivable
(although quite hard) to see a Lyman-alpha emission line from a star-forming
galaxy. | 0403345v1 |
2005-05-28 | Cosmic ray transport in MHD turbulence | Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call
for revisions in the picture of cosmic ray transport. In this paper we use
recently obtained scaling laws for MHD modes to obtain the scattering frequency
for cosmic rays. We account for the turbulence cutoff arising from both
collisional and collisionless damping. We obtain the scattering rate and show
that fast modes provide the dominant contribution to cosmic ray scattering for
the typical interstellar conditions in spite of the fact that fast modes are
subjected to damping. We determine how the efficiency of the scattering depends
on the characteristics of ionized media, e.g. plasma $\beta$. We show that
streaming instability is suppressed by the ambient MHD turbulence. | 0505575v1 |
2005-06-22 | A Damped Ly-alpha Absorption-line System in an Apparent Void at Redshift 2.38 | We study the contents of an apparent void in the distribution of Ly-alpha
emitting galaxies at redshift 2.38. We show that this void is not empty, but
contains a damped Ly-alpha absorption-line system, seen in absorption against
background QSO 2138-4427. Imaging does not reveal any galaxy associated with
this absorption-line system, but it contains metals (Fe/H ~ -1.3), and its
large velocity range (~ 180 km/s) implies a significant mass. | 0506525v1 |
2005-08-08 | Fluorescence in damp air and comments on the radiative life time | Photon yields in damp air excited by an electron using a Sr90 $\beta$ source
are compared withthose in dry air. Water vapors considerably reduce the yields,
however, a further study is needed to evaluate the effects on the energy
estimation of ultrahigh-energy cosmic rays. The relation of fluorescence
efficiency to the life time of de-excitation by radiation is discussed. | 0508183v1 |
2006-08-17 | Electron thermal conductivity owing to collisions between degenerate electrons | We calculate the thermal conductivity of electrons produced by
electron-electron Coulomb scattering in a strongly degenerate electron gas
taking into account the Landau damping of transverse plasmons. The Landau
damping strongly reduces this conductivity in the domain of ultrarelativistic
electrons at temperatures below the electron plasma temperature. In the inner
crust of a neutron star at temperatures T < 1e7 K this thermal conductivity
completely dominates over the electron conductivity due to electron-ion
(electron-phonon) scattering and becomes competitive with the the electron
conductivity due to scattering of electrons by impurity ions. | 0608371v1 |
2006-09-19 | Dust, Metals and Diffuse Interstellar Bands in Damped Lyman Alpha Systems | Although damped Lyman alpha (DLA) systems are usually considered metal-poor,
it has been suggested that this could be due to observational bias against
metal-enriched absorbers. I review recent surveys to quantify the particular
issue of dust obscuration bias and demonstrate that there is currently no
compelling observational evidence to support a widespread effect due to
extinction. On the other hand, a small sub-set of DLAs may be metal-rich and I
review some recent observations of these metal-rich absorbers and the detection
of diffuse interstellar bands in one DLA at z ~ 0.5. | 0609530v1 |
2006-11-08 | Comments on Viscous Damping of Non-Adiabatic MHD Waves in an Unbounded Solar Coronal Plasma by Kumar and Kumar | Considering thermal conduction, compressive viscosity and optically thin
radiation as damping mechanisms for MHD waves, we derive a six-order general
dispersion relation. We point out a fundamental flaw in the derivation of
five-order dispersion relation by Kumar and Kumar (2006) who adopt as a basis
vector. The correct definition of the motion in the x-z plane (2-D vector
space) stems from the two independent variables, namely . | 0611252v2 |
2007-01-10 | Non-gaussianity in fluctuations from warm inflation | The scalar mode density perturbations in a the warm inflationary scenario are
analysed with a view to predicting the amount of non-gaussianity produced by
this scenario. The analysis assumes that the inflaton evolution is strongly
damped by the radiation, with damping terms that are temperature independent.
Entropy fluctuations during warm inflation play a crucial role in generating
non-gaussianity and result in a distinctive signal which should be observable
by the Planck satellite. | 0701302v2 |
1998-05-22 | WKB for a damped spin | The master equation for a damped spin well known from the theory of
superradiance, is written as a finite-difference equation and solved by a
WKB-like method. The propagator thus obtained looks like the van Vleck
propagator of a certain classical Hamiltonian system with one degree of
freedom. A new interpretation is provided of the temporal broadening of
initially sharp probability distributions as the analogue of the spreading of
the quantum mechanical wave packet. | 9805018v1 |
1998-11-04 | Cascades of energy and helicity in the GOY shell model of turbulence | The effect of extreme hyperviscous damping, $\nu k_n^p, p=\infty$ is studied
numerically in the GOY shell model of turbulence. It has resently been
demonstrated [Leveque and She, Phys. Rev. Lett, 75,2690 (1995)] that the
inertial range scaling in the GOY model is non-universal and depending on the
viscous damping. The present study shows that the deviation from Kolmogorov
scaling is due to the cascade of the second inviscid invariant. This invariant
is non-positive definite and in this sense analogous to the helicity of 3D
turbulent flow. | 9811009v1 |
1994-02-04 | Effects of Disorder in a Dilute Bose Gas | We discuss the effects of a weak random external potential on the properties
of the dilute Bose gas at zero temperature. The results recently obtained by
Huang and Meng for the depletion of the condensate and of the superfluid
density are recovered. Results for the shift of the velocity of sound as well
as for its damping due to collisions with the external field are presented. The
damping of phonons is calculated also for dense superfluids. (submitted to
Phys.Rev.B) | 9402015v1 |
1997-02-13 | Comment on "Collective Excitations of a Bose-Einstein Condensate in a Magnetic Trap" | We calculate the damping rate of collective excitations for a nearly pure
Bose-Einstein condensate regarding the recent experiments in MIT [M.-O. Mews et
al, Phys. Rev. Lett. 77, 988 (1996)]. The decay time of collective excitations
obtained in our theoretical calculations agrees well with their experimental
result. We argue that the damping of collective excitations is due to thermal
contributions rather than interactions between collective modes. | 9702122v1 |
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 |
1998-12-02 | 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 |
1999-06-15 | 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 |
2000-09-13 | 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 |
2003-11-21 | 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 |
2005-12-03 | 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 |
2004-10-06 | 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 |
1994-09-22 | 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 |
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 |
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