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1999-02-01
|
Numerical Study of Inhomogeneous Pre-Big-Bang Inflationary Cosmology
|
We study numerically the inhomogeneous pre-big-bang inflation in a
spherically symmetric space-time. We find that a large initial inhomogeneity
suppresses the onset of the pre-big-bang inflation. We also find that even if
the pre-big-bang inflationary stage is realized, the initial inhomogeneities
are not homogenized. Namely, during the pre-big-bang inflation
``hairs''(irregularities) do not fall, in sharp contrast to the usual
(potential energy dominated) inflation where initial inhomogeneity and
anisotropy are damped and thus the resulting universe is less sensitive to
initial conditions.
|
9902003v1
|
1999-02-09
|
Quantum gravitational processes in a hot ultrarelativistic gas and their effect on the isotropic Universe evolution
|
The variant of quasiclassical (half-quantum) theory of gravity in strong
gravitational field is presented. The exact solution of the problem of the
renormalized energy-momentum tensor calculation is performed in terms of
non-local operator-signed function. The procedure of quasilocalization is
proposed, which leads to the equations of non-equilibrium thermodynamics for
temperature and curvature. The effects of induced particle creation and media
polarization are taking into account and used to solve the problem of
non-Einstein's branches damping. The problem of Universe creation from
"nothing" is also discussed.
|
9902023v1
|
1999-05-17
|
Parametric resonant acceleration of particles by gravitational waves
|
We study the resonant interaction of charged particles with a gravitational
wave propagating in the non-empty interstellar space in the presence of a
uniform magnetic field. It is found that this interaction can be cast in the
form of a parametric resonance problem which, besides the main resonance,
allows for the existence of many secondary ones. Each of them is associated
with a non-zero resonant width, depending on the amplitude of the wave and the
energy density of the interstellar plasma. Numerical estimates of the
particles' energisation and the ensuing damping of the wave are given.
|
9905054v1
|
1999-08-27
|
Double cosmic walls in Teleparallel Gravity
|
An example is given of a plane topological torsion defect representing a
cosmic wall double wall in teleparallel gravity.The parallel planar walls
undergone a repulsive gravitational force due to Cartan torsion.This is the
first example of a non-Riemannian double cosmic wall.It is shown that the walls
oscillate with a speed that depends on torsion and on the surface density of
the wall.Cartan torsion acts also as a damping force reducing the speed of
oscillation when it is stronger.
|
9908070v1
|
1999-09-30
|
Does a dynamical system lose energy by emitting gravitational waves?
|
We note that Eddington's radiation damping calculation of a spinning rod
fails to account for the complete mass integral as given by Tolman. The missing
stress contributions precisely cancel the standard rate given by the
'quadrupole formula'. This indicates that while the usual 'kinetic' term can
properly account for dynamical changes in the source, the actual mass is
conserved. Hence gravity waves are not carriers of energy in vacuum. This
supports the hypothesis that energy including the gravitational contribution is
confined to regions of non-vanishing energy-momentum tensor $T_{ik}$.
PACS numbers: 04.20.Cv, 04.30.-w
|
9909095v1
|
2000-01-07
|
Transition from inspiral to plunge in binary black hole coalescences
|
Combining recent techniques giving non-perturbative re-summed estimates of
the damping and conservative parts of the two-body dynamics, we describe the
transition between the adiabatic phase and the plunge, in coalescing binary
black holes with comparable masses moving on quasi-circular orbits. We give
initial dynamical data for numerical relativity investigations, with a fraction
of an orbit left, and provide, for data analysis purposes, an estimate of the
gravitational wave-form emitted throughout the inspiral, plunge and coalescence
phases.
|
0001013v2
|
2000-02-22
|
On the experimental foundations of the Maxwell equations
|
We begin by reviewing the derivation of generalized Maxwell equations from an
operational definition of the electromagnetic field and the most basic notions
of what constitutes a dynamical field theory. These equations encompass the
familiar Maxwell equations as a special case but, in other cases, can predict
birefringence, charge non-conservation, wave damping and other effects that the
familiar Maxwell equations do not. It follows that observational constraints on
such effects can restrict the dynamics of the electromagnetic field to be very
like the familiar Maxwellian dynamics, thus, providing an empirical foundation
for the Maxwell equations. We discuss some specific observational results that
contribute to that foundation.
|
0002075v1
|
2001-06-06
|
Black Hole Decay Rates in Large Extra Dimensions
|
We study the evaporation of black holes in space-times with extra dimensions
of size L. We show that the luminosity is greatly damped when the horizon
becomes smaller than L and black holes born with an initial size smaller than L
are almost stable. This effect is due to the dependence of both the occupation
number density of Hawking quanta and the grey-body factor of a black hole on
the dimensionality of space.
|
0106018v1
|
2001-11-29
|
Decoherence and gravitational backgrounds
|
We study the decoherence process associated with the scattering of stochastic
gravitational waves. We discuss the case of macroscopic systems, such as the
planetary motion of the Moon around the Earth, for which gravitational
scattering is found to dominate decoherence though it has a negligible
influence on damping. This contrast is due to the very high effective
temperature of the background of gravitational waves in our galactic
environment.
|
0111105v1
|
2002-08-13
|
Orbital evolution of a test particle around a black hole: higher-order corrections
|
We study the orbital evolution of a radiation-damped binary in the extreme
mass ratio limit, and the resulting waveforms, to one order beyond what can be
obtained using the conservation laws approach. The equations of motion are
solved perturbatively in the mass ratio (or the corresponding parameter in the
scalar field toy model), using the self force, for quasi-circular orbits around
a Schwarzschild black hole. This approach is applied for the scalar model.
Higher-order corrections yield a phase shift which, if included, may make
gravitational-wave astronomy potentially highly accurate.
|
0208034v1
|
2003-01-21
|
Quasinormal modes of the near extremal Schwarzschild-de Sitter black hole
|
We present an exact expression for the quasinormal modes of scalar,
electromagnetic and gravitational perturbations of a near extremal
Scwarzschild-de Sitter black hole and we show why a previous approximation
holds exactly in this near extremal regime. In particular, our results give the
asymptotic behavior of the quasinormal frequencies for highly damped modes,
which as recently attracted much attention due to the proposed identification
of its real part with the Barbero-Immirzi parameter.
|
0301078v2
|
2003-03-03
|
Quasinormal modes of Kerr black holes: The determination of the quasinormal frequencies with a new technique
|
We compute the quasinormal frequencies of rotating black holes using the
continued fraction method first proposed by Leaver. The main difference with
former works, is that our results are obtained by a new numerical technique
which avoids the use of two dimensional root-finding routines. The technique is
applied to evaluate the angular eigenvalues of Teukolsky's angular equation.
This method allow us to calculate both the slowly and the rapidly damped
quasinormal frequencies with excellent accuracy.
|
0303011v1
|
2003-09-18
|
Analytic determination of the asymptotic quasi-normal mode spectrum of small Schwarzschild-de Sitter black holes
|
Following the monodromy technique performed by Motl and Neitzke, we consider
the analytic determination of the highly damped (asymptotic) quasi-normal modes
of small Schwarzschild-de Sitter (SdS) black holes. We comment the result as
compared to the recent numerical data of Konoplya and Zhidenko.
|
0309090v2
|
2004-02-11
|
Electronic contribution to the oscillations of a gravitational antenna
|
We carefully analyse the contribution to the oscillations of a metallic
gravitational antenna due to the interaction between the electrons of the bar
and the incoming gravitational wave. To this end, we first derive the total
microscopic Hamiltonian of the wave-antenna system and then compute the
contribution to the attenuation factor due to the electron-graviton
interaction. As compared to the ordinary damping factor, which is due to the
electron viscosity, this term turns out to be totally negligible. This result
confirms that the only relevant mechanism for the interaction of a
gravitational wave with a metallic antenna is its direct coupling with the bar
normal modes.
|
0402048v1
|
2004-09-10
|
A Nonlinear Coupling Network to Simulate the Development of the r-mode Instablility in Neutron Stars I. Construction
|
R-modes of a rotating neutron star are unstable because of the emission of
gravitational radiation. We explore the saturation amplitudes of these modes
determined by nonlinear mode-mode coupling. Modelling the star as
incompressible allows the analytic computation of the coupling coefficients.
All couplings up to n=30 are obtained, and analytic values for the shear
damping and mode normalization are presented. In a subsequent paper we perform
numerical simulations of a large set of coupled modes.
|
0409048v1
|
2004-10-06
|
Quasinormal modes in time-dependent black hole background
|
We have studied the evolution of the massless scalar field propagating in
time-dependent charged Vaidya black hole background. A generalized tortoise
coordinate transformation were used to study the evolution of the massless
scalar field. It is shown that, for the slowest damped quasinormal modes, the
approximate formulae in stationary Reissner-Nordstr\"{o}m black hole turn out
to be a reasonable prescription, showing that results from quasinormal mode
analysis are rather robust.
|
0410025v2
|
2004-11-26
|
Gravitational wave interactions with magnetized plasmas
|
Gravitational waves (GWs) propagating through a uniformly magnetized plasma
interact directly with the magnetic field and excite magnetohydrodynamic (MHD)
waves with both electromagnetic and matter components. We study this process
for arbitrary geometry in the MHD approximation and find that all three
fundamental MHD modes -- slow and fast magnetosonic, and Alfven -- are excited
depending on both the polarization of the GW and the orientation of the ambient
magnetic field. The latter two modes can interact coherently with the GW
resulting in damping of the GW and linear growth of the plasma waves.
|
0411128v1
|
2005-01-30
|
Quasinormal modes in Schwarschild black holes due to arbitrary spin fields
|
The Newman-Penrose formalism is used to deal with the massless scalar,
neutrino, electromagnetic, gravitino and gravitational quasinormal modes (QNMs)
in Schwarzschild black holes in a united form. The quasinormal mode frequencies
evaluated by using the 3rd-order WKB potential approximation show that the
boson perturbations and the fermion perturbations behave in a contrary way for
the variation of the oscillation frequencies with spin, while this is no longer
true for the damping's, which variate with $s$ in a same way both for boson and
fermion perturbations.
|
0501098v2
|
2005-04-28
|
The ringing wormholes
|
We investigate the response of the traversable wormholes to the external
perturbations through finding their characteristic frequencies and time-domain
profiles. The considered solution describes traversable wormholes between the
branes in the two brane Randall-Sundrum model and was previously found within
Einstein gravity with a conformally coupled scalar field. The evolution of
perturbations of a wormhole is similar to that of a black hole and represents
damped oscillations (ringing) at intermediately late times, which are
suppressed by power law tails (proportional to t^{-2} for monopole
perturbations) at asymptotically late times.
|
0504139v1
|
2005-05-31
|
Quasinormal modes of Rarita-Schwinger field in Reissner-Nordström black hole spacetimes
|
The Newman-Penrose formalism is used to deal with the quasinormal
modes(QNM's) of Rarita-Schwinger perturbations outside a Reissner-Nordstr\"{o}m
black hole. We obtain four kinds of possible expressions of effective
potentials, which are proved to be of the same spectra of quasinormal mode
frequencies. The quasinormal mode frequencies evaluated by the WKB potential
approximation show that, similar to those for Dirac perturbations, the real
parts of the frequencies increase with the charge $Q$ and decrease with the
mode number $n$, while the dampings almost keep unchanged as the charge
increases.
|
0505161v1
|
2005-11-16
|
Quasinormal modes of a black hole surrounded by quintessence
|
Using the third-order WKB approximation, we evaluate the quasinormal
frequencies of massless scalar field perturbation around the black hole which
is surrounded by the static and spherically symmetric quintessence. Our result
shows that due to the presence of quintessence, the scalar field damps more
rapidly. Moreover, we also note that the quintessential state parameter
$\epsilon$ (the ratio of pressure $p_q$ to the energy density $\rho_q$) play an
important role for the quasinormal frequencies. As the state parameter
$\epsilon$ increases the real part increases and the absolute value of the
imaginary part decreases. This means that the scalar field decays more slowly
in the larger $\epsilon$ quintessence case.
|
0511085v1
|
2006-12-01
|
Quasinormal modes of a Schwarzschild black hole surrounded by free static spherically symmetric quintessence: Electromagnetic perturbations
|
In this paper, we evaluated the quasinormal modes of electromagnetic
perturbation in a Schwarzschild black hole surrounded by the static spherically
symmetric quintessence by using the third-order WKB approximation when the
quintessential state parameter $ w_{q}$ in the range of $-1/3<w_{q}<0$. Due to
the presence of quintessence, Maxwell field damps more slowly. And when at
$-1<w_{q}<-1/3$, it is similar to the black hole solution in the ds/Ads
spacetime. The appropriate boundary conditions need to be modified.
|
0612010v2
|
1998-10-09
|
A Technique of Direct Tension Measurement of a Strung Fine Wire
|
We present a new technique of direct measurement of wire tensions in wire
chambers. A specially designed circuit plucks the wire using the Lorentz force
and measures the frequency of damped transverse oscillations of the wire. The
technique avoids the usual time-consuming necessity of tuning circuit parameter
to a resonance. It allows a fast and convenient determination of tensions and
is straightforward to implement.
|
9810023v1
|
1999-11-24
|
Chiral Gauge Theory on Lattice with Domain Wall Fermions
|
We investigate a U(1) lattice chiral gauge theory with domain wall fermions
and compact gauge fixing. In the reduced model limit, our perturbative and
numerical investigations show that there exist no extra mirror chiral modes.
The longitudinal gauge degrees of freedom have no effect on the free domain
wall fermion spectrum consisting of opposite chiral modes at the domain wall
and at the anti-domain wall which have an exponentially damped overlap.
|
9911029v3
|
2004-03-22
|
What can Lattice QCD theorists learn from NMR spectroscopists?
|
Euclidean-time hadron correlation functions computed in Lattice QCD (LQCD)
are modeled by a sum of decaying exponentials, reminiscent of the exponentially
damped sinusoid models of free induction decay (FID) in Nuclear Magnetic
Resonance (NMR) spectroscopy. We present our initial progress in studying how
data modeling techniques commonly used in NMR perform when applied to LQCD
data.
|
0403023v2
|
1992-04-10
|
Resummation in a Hot Scalar Field Theory
|
A resummed perturbative expansion is used to obtain the self-energy in the
high-temperature \(g^2\phi^4\) field theory model up to order $g^4$. From this
the zero momentum pole of the effective propagator is evaluated to determine
the induced thermal mass and damping rate for the bosons in the plasma to order
$g^3$. The calculations are performed in the imaginary time formalism and a
simple diagrammatic analysis is used to identify the relevant diagrams at each
order. Results are compared with similar real-time calculations found in the
literature.
|
9204216v1
|
1993-05-11
|
High Temperature Response Functions and the Non-Abelian Kubo Formula
|
We describe the relationship between time-ordered and retarded response
functions in a plasma. We obtain an expression, including the proper
$i\epsilon$-prescription, for the induced current due to hard thermal loops in
a non-Abelian theory, thus giving the non-Abelian generalization of the Kubo
formula. The result is closely related to the eikonal for a Chern-Simons theory
and is relevant for a gauge-invariant description of Landau damping in the
quark-gluon plasma at high temperature.
|
9305241v1
|
1993-06-09
|
Is the scalar meson seen in CELLO data on $γγ\rightarrowπ^+π^-$ ?
|
We analyze the CELLO angular distributions
$\gamma\gamma\rightarrow\pi^+\pi^-$ with the unitary model \cite{KS-86} for
helicity 2 amplitude. In contrast to previous analysis \cite{CELLO} we do not
see any QED damping. The obtained S--wave does not contradict to low--energy
theorem and demonstrates more clealy the resonance--like behaviour near 1.3
Gev.
|
9306249v1
|
1993-07-27
|
Dynamical Growth Rate of a Diffuse Interface in First Order Phase Transitions
|
We compute the dynamical prefactor in the nucleation rate of bubbles or
droplets in first order phase transitions for the case where both viscous
damping and thermal dissipation are significant. This result, which generalizes
previous work on nucleation, may be applied to study the growth of bubbles or
droplets in condensed matter systems as well as in heavy ion collisions and in
the expansion of the early universe.
|
9307348v1
|
1993-11-23
|
Perturbative Hot Gauge Theories - Recent Results
|
Current results in high temperature gauge theories obtained in the context of
the perturbative method of resumming hard thermal loops are reviewed. Beyond
leading order properties of the gluon excitation, and the recent
(controversial) calculations of the damping rates are discussed. QCD
predictions on plasma signatures are exemplified by the thermal production
rates of energetic as well as soft photons. [Talk given at the 3rd Workshop on
Thermal Field Theories and their Applications, August 15--27, 1993, Banff,
Alberta, Canada]
|
9311343v1
|
1994-06-10
|
QCD Transport Theory
|
Because of the long range of the gauge interactions, the collective behaviour
of quarks and gluons plays a decisive role in the transport processes.
Collective effects, like Debye screening and Landau damping, remove the
unphysical infrared divergences of the transport cross-sections and provide
finite relaxation rates. I review here a theory of the plasma collective
excitations that has been recently developed. It is based on kinetic equations
derived from the general QCD Dyson-Schwinger equations, in the weak coupling
limit. I present new, truly non-abelian, collective excitations, which
correspond to nonlinear color oscillations of the QCD plasma.
|
9406277v1
|
1994-08-08
|
Gluon Decay as a Mechanism for Strangeness Production in a Quark-Gluon Plasma
|
A calculation of thermal gluon decay shows that this process contributes
significantly to strangeness production in a quark-gluon plasma. Our analysis
does not support recent claims that this is the dominant process. In our
calculations we take into account the resummed form of the transverse and
longitudinal parts of the gluon propagator following the Braaten-Pisarski
method. Our results are subject to the uncertainty concerning the estimate of
the damping rate entering the effective gluon propagator.
|
9408249v1
|
1994-12-02
|
High Harmonic Configurations of Cosmic Strings: An Analysis of Self-Intersections
|
A general formulation for describing odd-harmonic cosmic strings is developed
and used to determine the self-intersection properties of high-harmonic loops.
This is important because loop formation mechanisms produce high-harmonic
components (kinks) which can only be eliminated very slowly by gravitational
radiation, damping by the dense surrounding plasma in the era of string
formation, or by the expansion of the Universe. For the class of loops examined
it has been found that in the high-harmonic limit, essentially all cosmic loops
self-intersect.
|
9412216v2
|
1995-03-19
|
SELF-ENERGY PECULIARITIES OF THE HOT GAUGE THEORY AFTER SYMMETRY BREAKING
|
A tensor representation of the gluon propagator is found within covariant
gauges for a non-Abelian theory after symmetry breaking due to $<A_0>\ne 0$ and
the exact equations which determine the dispersion laws of plasma excitations
are explicitly obtained. In the high temperature region and fixing the Feynman
gauge we solved these equations and found the damping of the plasma
oscillations and the shifting of their frequency. The phase transition of a
gauge symmetry restoration is estimated to be $\alpha_c(T) \approx{4/3}$.
|
9503379v1
|
1995-03-21
|
EFFECTS OF SHADOWING IN DOUBLE POMERON EXCHANGE PROCESSES
|
The effects of shadowing in double Pomeron exchange processes are
investigated within an eikonal approach with a Gaussian input. Damping factors
due to screening are calculated for this process and compared with the factors
obtained for total, elastic and single diffraction cross sections. Our main
conclusion is that counting rate calculations, of various double Pomeron
exchange processes (without screening corrections) such as heavy quark and
Higgs production are reduced by a factor of 5 in the LHC energy range, when
screening corrections are applied.
|
9503394v1
|
1996-03-09
|
Nucleons at Finite Temperature
|
The nucleon mass shift is calculated using chiral counting arguments and a
virial expansion, without and with the $\Delta$. At all temperatures, the mass
shift and damping rate are dominated by the $\Delta$. Our results are compared
with the empirical analysis of Leutwyler and Smilga, as well as results from
heavy baryon chiral perturbation theory in the large $N_{c}$ (number of color)
limit. We show that unitarity implies that the concepts of thermal shifts are
process dependent.
|
9603257v1
|
1996-03-25
|
Fermion Scattering at a Phase Wave
|
We study fermion reflection at a phase wave which is formed during a bubble
collision in a first order phase transition. We calculate the reflection and
the transmission coefficients by solving the Dirac equation with the phase wave
background. Using the results we analyze the damping and the velocity of the
wave.
|
9603401v2
|
1996-08-23
|
The effect of Silk damping on primordial magnetic fields
|
We study the effects of plasma viscosity on the dynamics of primordial
magnetic fields by simulating magnetohydrodynamics in the early universe by
appropriate non-linear cascade models. We find numerically that even in the
presence of large kinetic viscosity, magnetic energy is transferred to large
length scales. There are indications, however, that the inverse cascade stops
at a given time which depends on the magnitude of viscosity. For realistic
viscosities we do not find equipartition between magnetic and kinetic energies.
|
9608422v1
|
1997-02-04
|
Chiral Dynamics with Quark Degrees of Freedom
|
Possibility to detect DCC fluctuations is discussed. It is shown that
interactions with quark background and dissipative effects due to interactions
in the chiral field may result in damping of fluctuations. Since the magnitude
of fluctuations depends strongly on the initial state and speed of chiral phase
transition accurate evaluation of all modifying processes is required to
predict observability of DCCs.
|
9702246v1
|
1998-08-17
|
Hot QED beyond ladder graphs
|
At finite temperature a breakdown of the hard thermal loop expansion arises
whenever external momenta are light-like or tend to very soft scales. A
resummation of ladder graphs is important in these cases where the effects of
infrared or light-cone singularities are enhanced. We show that in hot QED
another class of diagrams is also relevant at leading order due to long range
magnetic interactions and therefore recent studies about ladder expansions need
to be corrected. A general cancellation of the hard modes damping effects still
occurs near the light-cone or in the infrared region. The validity of an
improved version of the hard thermal loop resummation scheme is discussed.
|
9808344v1
|
1998-09-01
|
Dynamical screening away from equilibrium: hard photon production and collisional energy loss
|
We investigate the production rate for hard real photons and the collisional
energy loss in the quark-gluon plasma away from chemical equilibrium. Applying
the Hard-Thermal-Loop resummation scheme away from equilibrium, we can show
that Landau damping provides dynamical screening for both fermion and boson
exchange present in the two quantities.
|
9809214v2
|
1998-09-24
|
Infrared and light-cone limit in hot QED
|
In hot gauge theories a breakdown of the hard thermal loop expansion occurs
for light-like external momenta or in the infrared region. In QED where a
resummation of ladder diagrams is usually advocated, it is shown that long
range magnetic interations involve a broader set of graphs. The consequence is
a generalized compensation of the hard modes damping terms at leading order in
the infrared limit and near the light-cone. The relevance of the so-called
improved hard thermal loop resummation scheme is discussed.
|
9809516v2
|
1999-02-11
|
Hard-thermal-loop Resummation of the Free Energy of a Hot Gluon Plasma
|
We calculate the free energy of a hot gluon plasma to leading order in
hard-thermal-loop perturbation theory. Effects associated with screening, gluon
quasiparticles, and Landau damping are resummed to all orders. The ultraviolet
divergences generated by the hard-thermal-loop propagator corrections can be
cancelled by a temperature-independent counterterm. The deviation of the
hard-thermal-loop free energy from lattice QCD results for T > 2 T_c has the
correct sign and roughly the correct magnitude to be accounted for by
next-to-leading order corrections.
|
9902327v2
|
1999-07-13
|
Inplication of percolation of colour strings on multiplicities, correlations and the transverse momentum
|
In the colour string model the impact of string percolation on
multiplicities, their long-range correlations and average transverse momentum
is studied. The multiplicities are shown to be damped by a simple factor which
follows from the percolation theory. A clear signature of the phase transition
is found to be a behaviour of the correlations for intensive observables, such
as average transverse momentum, which can be detected in the high-energy heavy
ion collisions.
|
9907332v1
|
1999-08-11
|
Hard-thermal-loop Resummation of the Free Energy of a Hot Quark-Gluon Plasma
|
The quark contribution to the free energy of a hot quark-gluon plasma is
calculated to leading order in hard-thermal-loop (HTL) perturbation theory.
This method selectively resums higher order corrections associated with plasma
effects, such as screening, quasiparticles, and Landau damping. Comparing to
the weak-coupling expansion of QCD, the error in the one-loop HTL free energy
is of order alpha_s, but the large alpha_s^(3/2) correction from QCD plasma
effects is included exactly.
|
9908323v2
|
1999-08-16
|
Hard-thermal-loop resummed pressure of a degenerate quark-gluon plasma
|
We compute the pressure of a finite density quark-gluon plasma at zero
temperature to leading order in hard-thermal-loop perturbation theory, which
includes the fermionic excitations and Landau damping. The result is compared
with the weak-coupling expansion for finite positive chemical potential $\mu$
through order $\alpha_s^2$ and with a quasiparticle model with a mass depending
on $\mu$.
|
9908372v3
|
1999-09-22
|
Dynamical Manifestation of the Goldstone Phenomenon at 1-loop
|
We have calculated the damping rate $\Gamma (|{\bf k}|)$ for classical
on-shell Goldstone modes of the O(2) symmetric scalar fields propagating in a
thermal medium of the broken symmetry phase taking into account the effect of
the explicit symmetry breaking. The result of the one-loop analysis can be
expanded around $\Gamma (0)$, which depends non-analytically on the parameter
of the explicit symmetry breaking, h. $\Gamma (0)$ vanishes when $h\to 0$,
demonstrating in this way the absence of the restoring force, when the
equilibrium direction of the symmetry breaking is modulated homogeneously.
|
9909474v1
|
1999-12-29
|
Recent Development on Collective Neutrino Interactions
|
Quantum Field Theory is applied to study an electron plasma under an intense
neutrino flux. The dispersion relation of the longitudinal waves is derived and
the damping rate is calculated. It is shown that in the case of Supernova
emission the neutrinos are not collimated enough to cause plasma instabilities
associated to a strong neutrino resonance effect.
|
9912533v1
|
2000-02-11
|
Dispersion Laws for Goldstone Bosons in a Color Superconductor
|
The effective action for Goldstone bosons in the color-flavor locking phase
of dense QCD is analyzed. Interaction terms and higher derivatives in the
effective action appear to be controlled by different scales. At energies of
order of the superconducting gap, the derivative expansion breaks down, while
interactions still remain suppressed. The effective action valid at energies
and momenta comparable to the gap is derived. Dispersion laws following from
this action are such that the energy of Goldstone bosons is always smaller than
the gap in the quasiparticle spectrum, and Goldstone bosons always propagate
without damping.
|
0002123v2
|
2000-10-16
|
New Developments and Applications of Thermal Field Theory
|
The lecture provides an introduction to thermal field theory and its
applications to the physics of the quark-gluon plasma, possibly created in
relativistic heavy ion collisions. In particular the Hard Thermal Loop
resummation technique, providing a consistent perturbative description of
relativistic, high-temperature plasmas is introduced. Using this method
interesting quantities of the quark-gluon plasma (damping rates, energy loss,
photon and dilepton production) are discussed. Furthermore recent developments
on non-equilibrium field theory, which are relevant for high-energy heavy ion
physics, are presented.
|
0010164v1
|
2000-12-20
|
Equivalence between Gaussian averaged neutrino oscillations and neutrino decoherence
|
In this paper, we show that a Gaussian averaged neutrino oscillation model is
equivalent to a neutrino decoherence model. Without loss of generality, the
analysis is performed with two neutrino flavors. We also estimate the damping
(or decoherence) parameter for atmospheric neutrinos and compare it to earlier
obtained results.
|
0012272v2
|
2001-01-05
|
Instabilities in neutrino-plasma density waves
|
One examines the interaction and possible resonances between supernova
neutrinos and electron plasma waves. The neutrino phase space distribution and
its boundary regions are analyzed in detail. It is shown that the boundary
regions are too wide to produce non-linear resonant effects. The growth or
damping rates induced by neutrinos are always proportional to the neutrino flux
and $G_{{\rm F}}^{2}$.
|
0101054v2
|
2001-01-28
|
High-temperature, classical, real-time dynamics of non-abelian gauge theories as seen by a computer
|
We test at the electroweak scale the recently proposed elaborate theoretical
scenario for real-time dynamics of non-abelian gauge theories at high
temperature. We see no sign of the predicted behavior. This indicates that
perturbative concepts like color conductivity and Landau damping might be
irrelevant at temperatures corresponding to the electroweak scale.
|
0101309v1
|
2001-12-03
|
Crystalline Color Superconductivity in Dense Matter
|
In this talk I discuss a recently proposed color superconducting phase of
asymmetric quark matter where the up and down quark have different chemical
potential, being in chemical equilibrium with electrons. Using Schwinger-Dyson
equations derived from an effective theory of low-energy quasiparticles, a
critical coupling for LOFF phase is estimated for both the case of an effective
four Fermi interaction and Landau-damped one gluon exchange.
|
0112028v1
|
2001-12-10
|
Non-Abelian Medium Effects in Quark-Gluon Plasma
|
Based on the kinetic theory, the non-Abelian medium property of hot
Quark-Gluon Plasma is investigated. The nonlinearity of the plasma comes from
two aspects: The nonlinear wave-wave interaction and self-interaction of color
field. The non-Abelian color permittivity is obtained by expanding the kinetic
equations to third order. As an application, the nonlinear Landau damping rate
and the nonlinear eigenfrequency shift are calculated in the longwave length
limit.
|
0112128v1
|
2004-03-20
|
Hard gluon damping in hot QCD
|
The gluon collisional width in hot QCD plasmas is discussed with emphasis on
temperatures near $T_c$, where the coupling is large. Considering its effect on
the entropy, which is known from lattice calculations, it is argued that the
width, which in the perturbative limit is given by $\gamma \sim g^2 \ln(1/g)
T$, should be sizeable at intermediate temperatures but has to be small close
to $T_c$. Implications of these results for several phenomenologically relevant
quantities, such as the energy loss of hard jets, are pointed out.
|
0403225v1
|
2004-08-28
|
Thermal Effects on Pure and Hybrid Inflation
|
This paper discusses models of inflation based on global supersymmetry. It is
shown that there are parameter ranges, consisent with observational
constraints, for which warm inflation occurs and supergravity effects can be
neglected. There is no need for any fine tuning of parameters. The thermal
corrections to the inflaton potential are calculated and found to be
unimportant.
|
0408323v3
|
2004-09-23
|
Hard parton damping in hot QCD
|
The gluon and quark collisional widths in hot QCD plasmas are discussed with
emphasis on temperatures near Tc, where the coupling is large. Considering the
effect on the entropy, which is known from lattice calculations, it is argued
that the width of the partons, which in the perturbative limit is given by
gamma ~ g^2 ln(1/g) T, should be sizeable at intermediate temperatures but has
to be small close to Tc. This behavior implies a substantial reduction of the
radiative energy loss of jets near Tc.
|
0409270v1
|
2004-12-20
|
Role of the gluons in the color screening in a QCD plasma
|
The color screening in a QCD plasma, that was studied in a formulation making
evident similarities and differences with the electric case, is continued by
taking into account the contributions of real gluons. The results, which
include a numerical analysis not previously performed, show a damping of the
correlation function which, if not exponential, does not differ very much from
that form.
The role of the temperature, which affect both the population and the
dynamics of the quark-gluon system, is found to be relevant.
|
0412287v1
|
2005-07-13
|
Feedback effects on the pairing interaction in color superconductors near the transition temperature
|
We examine the role that the gap dependence of the pairing interaction plays
in the gap equation for a weakly coupled uniform superfluid of three-flavor
massless quarks near the transition temperature T_c. We find that the feedback
effects on Landau-damped transverse gluons mediating the pairing interaction
alter the gap magnitude in a way dependent on the color structure of the gap.
We estimate corrections by these effects to the parameters characterizing the
fourth order terms in the Ginzburg-Landau free energy and ensure the stability
of a color-flavor locked state near T_c.
|
0507161v1
|
2005-08-31
|
Study of the gluon propagator in the large-N_f limit at finite temperature and chemical potential for weak and strong couplings
|
At finite temperature and chemical potential, the leading-order
(hard-thermal-loop) contributions to the gauge-boson propagator lead to
momentum-dependent thermal masses for propagating quasiparticles as well as
dynamical screening and Landau damping effects. We compare the
hard-thermal-loop propagator with the complete large-N_f gluon propagator, for
which the usually subleading contributions, such as a finite width of
quasiparticles, can be studied at nonperturbatively large effective coupling.
We also study quantitatively the effect of Friedel oscillations in
low-temperature electrostatic screening.
|
0508317v1
|
2006-02-24
|
Shear Viscosity of Hot QED at Finite Density from Kubo Formula
|
Within the framework of finite temperature field theory this paper discusses
the shear viscosity of hot QED plasma through Kubo formula at one-loop skeleton
diagram level with a finite chemical potential. The effective widths(damping
rates) are introduced to regulate the pinch singularities. The finite chemical
potential, which enhances the contributions to the shear viscosity from the
electrons while suppresses those from the photons, finally gives a positive
contribution compared to the pure temperature environment. The result agrees
with that from the kinetics theory qualitatively.
|
0602221v1
|
2006-10-27
|
Chiral transition and mesonic excitations for quarks with thermal masses
|
We study the effect of a thermal quark mass, m_T, on the chiral phase
transition and mesonic excitations in the light quark sector at finite
temperature in a simple chirally-symmetric model. We show that while nonzero
m_T lowers the chiral condensate, the chiral transition remains of second
order. It is argued that the mesonic excitations have large decay rate at
energies below 2m_T, owing to the Landau damping of the quarks and the van Hove
singularities of the collective modes.
|
0610374v3
|
1993-06-01
|
Transport Properties of Solitons
|
We calculate in this article the transport coefficients which characterize
the dynamics of solitons in quantum field theory using the methods of
dissipative quantum systems. We show how the damping and diffusion coefficients
of soliton-like excitations can be calculated using the integral functional
formalism. The model obtained in this article has new features which cannot be
obtained in the standard models of dissipation in quantum mechanics.
|
9306007v1
|
1994-03-23
|
Hard Thermal Loops, Chern-Simons Theory and the Quark-Gluon Plasma
|
The generating functional for hard thermal loops in QCD is important in
setting up a resummed perturbation theory. I review how this functional is
related to the eikonal for a Chern-Simons theory, and using an auxiliary field,
to the gauged WZNW-action. The induced current due to hard thermal loops,
properly incorporating damping effects, is also briefly discussed. (Invited
talk at the Third Worshop on Thermal Field Theories, Banff, Canada, August,
1993.)
|
9403145v1
|
1994-04-21
|
Wigner distribution function and entropy of the damped harmonic oscillator within the theory of open quantum systems
|
The harmonic oscillator with dissipation is studied within the framework of
the Lindblad theory for open quantum systems. By using the Wang-Uhlenbeck
method, the Fokker-Planck equation, obtained from the master equation for the
density operator, is solved for the Wigner distribution function, subject to
either the Gaussian type or the $\delta$-function type of initial conditions.
The obtained Wigner functions are two-dimensional Gaussians with different
widths. Then a closed expression for the density operator is extracted. The
entropy of the system is subsequently calculated and its temporal behaviour
shows that this quantity relaxes to its equilibrium value.
|
9404129v1
|
1995-02-07
|
QUANTUM DISSIPATION AND QUANTUM NOISE
|
We derive the exact action for a damped mechanical system ( and the special
case of the linear oscillator) from the path integral formulation of the
quantum Brownian motion problem developed by Schwinger and by Feynman and
Vernon. The doubling of the phase-space degrees of freedom for dissipative
systems and thermal field theories is discussed and the initial values of the
doubled variables are related to quantum noise effects.
|
9502044v1
|
1995-03-21
|
QUANTUM DISSIPATION AND QUANTUM GROUPS
|
We discuss the r\^ole of quantum deformation of Weyl-Heisenberg algebra in
dissipative systems and finite temperature systems. We express the time
evolution generator of the damped harmonic oscillator and the generator of
thermal Bogolubov transformations in terms of operators of the quantum
Weyl-Heisenberg algebra. The quantum parameter acts as a label for the
unitarily inequivalent representations of the canonical commutation relations
in which the space of the states splits in the infinite volume limit.
|
9503136v1
|
1996-08-27
|
Thermalization and Lyapunov Exponents in the Yang-Mills-Higgs Theory
|
We investigate thermalization processes occurring at different time scales in
the Yang-Mills-Higgs system at high temperatures. We determine the largest
Lyapunov exponent associated with the gauge fields and verify its relation to
the perturbatively calculated damping rate of a static gauge boson.
|
9608181v1
|
1998-12-22
|
String Propagation in Bianchi Type I models: Dynamical anisotropy Damping and Consequences
|
A generic ansatz is introduced which provides families of exact solutions to
the equations of motion and constraints for null-strings in Bianchi type I
cosmological models. This is achieved irrespective of the form of the metric.
Within classes of dilaton cosmologies a backreaction mapping relation is
established where the null string leads to more or less anisotropic members of
the family. The equations of motion and constraints for the generic model are
casted in their first order form and integrated both analytically and
numerically.
|
9812198v1
|
2000-08-10
|
Perturbative Noncommutative Quantum Gravity
|
We study perturbative noncommutative quantum gravity by expanding the
gravitational field about a fixed classical background. A calculation of the
one loop gravitational self-energy graph reveals that only the non-planar
graviton loops are damped by oscillating internal momentum dependent factors.
The noncommutative quantum gravity perturbation theory is not renormalizable
beyond one loop for matter-free gravity and all loops for matter interactions.
Comments are made about the nonlocal gravitational interactions produced by the
noncommutative spacetime geometry.
|
0008089v2
|
2000-10-03
|
Damped harmonic oscillators in the holomorphic representation
|
Quantum dynamical semigroups are applied to the study of the time evolution
of harmonic oscillators, both bosonic and fermionic. Explicit expressions for
the density matrices describing the states of these systems are derived using
the holomorphic representation. Bosonic and fermionic degrees of freedom are
then put together to form a supersymmetric oscillator; the conditions that
assure supersymmetry invariance of the corresponding dynamical equations are
explicitly derived.
|
0010013v1
|
2000-11-28
|
Non-Anticommutative Quantum Gravity
|
A calculation of the one loop gravitational self-energy graph in
non-anticommutative quantum gravity reveals that graviton loops are damped by
internal momentum dependent factors in the modified propagator and the vertex
functions. The non-anticommutative quantum gravity perturbation theory is
finite for matter-free gravity and for matter interactions.
|
0011259v2
|
2002-10-14
|
Time-reversal violation as loop-antiloop symmetry breaking: the Bessel equation, group contraction and dissipation
|
We show that the Bessel equation can be cast, by means of suitable
transformations, into a system of two damped/amplified parametric oscillator
equations. The relation with the group contraction mechanism is analyzed and
the breakdown of loop-antiloop symmetry due to group contraction manifests
itself as violation of time-reversal symmetry. A preliminary discussion of the
relation between some infinite dimensional loop-algebras, such as the
Virasoro-like algebra, and the Euclidean algebras e(2) and e(3) is also
presented.
|
0210129v1
|
2002-11-09
|
One-Loop Effective Action on Rotational Spacetime: Zeta-Function Regularization and Schwinger Perturbative Expansion
|
The zeta-function regularization method is used to evaluate the renormalized
effective action for massless conformally coupling scalar field propagating in
a closed Friedman spacetime perturbed by a small rotation. To the second order
of the rotational parameter in the model spacetime the analytic form of the
effective action is obtained with the help of the Schwinger perturbation
formula. After investigating the time evolution of the rotational parameter we
find that the quantum field effect can produce an effect which damps the
cosmological rotational in the early universe.
|
0211079v1
|
2003-06-01
|
Asymptotic Quasinormal Frequencies of d-dimensional Schwarzschild Black Holes
|
We determine the quasinormal frequencies for all gravitational perturbations
of the d-dimensional Schwarzschild black hole, in the infinite damping limit.
Using the potentials for gravitational perturbations derived recently by
Ishibashi and Kodama, we show that in all cases the asymptotic real part of the
frequency is proportional to the Hawking temperature with a coefficient of log
3. Via the correspondence principle, this leads directly to an equally spaced
entropy spectrum. We comment on the possible implications for the spacing of
eigenvalues of the Virasoro generator in the associated near-horizon conformal
algebra.
|
0306004v2
|
2005-02-15
|
Linear Cosmological Perturbations in D-brane Gases
|
We consider linear cosmological perturbations on the background of a D-brane
gas in which the compact dimensions and the dilaton are stabilized. We focus on
long wavelength fluctuations and find that there are no instabilities. In
particular, the perturbation of the internal space performs damped oscillations
and decays in time. Therefore, the stabilization mechanism based on D-brane
gases in string theory remains valid in the presence of linearized
inhomogeneities.
|
0502133v2
|
2006-10-09
|
Links. Relating different physical systems through the common QFT algebraic structure
|
In this report I review some aspects of the algebraic structure of QFT
related with the doubling of the degrees of freedom of the system under study.
I show how such a doubling is related to the characterizing feature of QFT
consisting in the existence of infinitely many unitarily inequivalent
representations of the canonical (anti-)commutation relations and how this is
described by the q-deformed Hopf algebra. I consider several examples, such as
the damped harmonic oscillator, the quantum Brownian motion, thermal field
theories, squeezed states, classical-to-quantum relation, and show the
analogies, or links, among them arising from the common algebraic structure of
the q-deformed Hopf algebra.
|
0610094v1
|
2006-11-21
|
Gravitational spectrum of black holes in the Einstein-Aether theory
|
Evolution of gravitational perturbations, both in time and frequency domains,
is considered for a spherically symmetric black hole in the non-reduced
Einstein-Aether theory. It is shown that real oscillation frequency and damping
rate are larger for the Einstein-Aether black hole than for the Schwarzschild
black hole. This may provide an opportunity to observe aether in the
forthcoming experiments with new generation of gravitational antennas.
|
0611226v2
|
1996-11-27
|
Symmetry breaking perturbations and strange attractors
|
The asymmetrically forced, damped Duffing oscillator is introduced as a
prototype model for analyzing the homoclinic tangle of symmetric dissipative
systems with \textit{symmetry breaking} disturbances. Even a slight fixed
asymmetry in the perturbation may cause a substantial change in the asymptotic
behavior of the system, e.g. transitions from two sided to one sided strange
attractors as the other parameters are varied. Moreover, slight asymmetries may
cause substantial asymmetries in the relative size of the basins of attraction
of the unforced nearly symmetric attracting regions. These changes seems to be
associated with homoclinic bifurcations. Numerical evidence indicates that
\textit{strange attractors} appear near curves corresponding to specific
secondary homoclinic bifurcations. These curves are found using analytical
perturbational tools.
|
9611217v1
|
2000-04-10
|
Penalty approximation for non smooth constraints in vibroimpact
|
We examine the penalty approximation of the free motion of a material point
in an angular domain; we choose an over-damped penalty, and we prove that if
the first impact point is not at the vertex, then, the limit of the
approximation exists and is described by Moreau's rule for anelastic impacts.
The proofs rely on validated asymptotics and use some classical tools in the
theory of dynamical systems.
|
0004054v1
|
2004-12-22
|
Adaptation and nonlinear parametrization: nonlinear dynamics prospective
|
We consider adaptive control problem in presence of nonlinear parametrization
of uncertainties in the model. It is shown that despite traditional approaches
require for domination in the control loop during adaptation, it is not often
necessary to use such energy inefficient compensators it in wide range of
applications. In particular, we show that recently introduced adaptive control
algorithms in finite form which are applicable to monotonic parameterized
systems can be extended to general smooth non-monotonic parametrization. These
schemes do not require any damping or domination in control inputs.
|
0412444v1
|
2006-05-31
|
Subgeometric rates of convergence of f-ergodic strong Markov processes
|
We provide a condition for f-ergodicity of strong Markov processes at a
subgeometric rate. This condition is couched in terms of a supermartingale
property for a functional of the Markov process. Equivalent formulations in
terms of a drift inequality on the extended generator and on the resolvent
kernel are given. Results related to (f,r)-regularity and to moderate deviation
principle for integral (bounded) functional are also derived. Applications to
specific processes are considered, including elliptic stochastic differential
equation, Langevin diffusions, hypoelliptic stochastic damping Hamiltonian
system and storage models.
|
0605791v1
|
2007-02-13
|
Integral Equations in the Theory of Levy Processes
|
In this article we consider the Levy processes and the corresponding
semigroup. We represent the generator of this semigroup in a convolution form.
Using the obtained convolution form and the theory of integral equations we
investigate the properties of a wide class of Levy processes (potential,
quasi-potential, the probability of the Levy process remaining within the given
domain, long time behavior, stable processes). We analyze in detail a number of
concrete examples of the Levy processes (stable processes, the variance damped
Levy processes, the variance gamma processes, the normal Gaussian process, the
Meixner process, the compound Poisson process).
|
0702378v1
|
2000-01-03
|
Slow Motion of Charges Interacting Through the Maxwell Field
|
We study the Abraham model for $N$ charges interacting with the Maxwell
field. On the scale of the charge diameter, $R_{\phi}$, the charges are a
distance $\eps^{-1}R_{\phi}$ apart and have a velocity $\sqrt{\eps} c$ with
$\eps$ a small dimensionless parameter. We follow the motion of the charges
over times of the order $\eps^{-3/2}R_{\phi}/c$ and prove that on this time
scale their motion is well approximated by the Darwin Lagrangian. The mass is
renormalized. The interaction is dominated by the instantaneous Coulomb forces,
which are of the order $\eps^{2}$. The magnetic fields and first order
retardation generate the Darwin correction of the order $\eps^{3}$. Radiation
damping would be of the order $\eps^{7/2}$.
|
0001002v1
|
2001-02-07
|
Post-Coulombian Dynamics at Order 1.5
|
We study the dynamics of N charges interacting with the Maxwell field. If
their initial velocities are small compared to the velocity of light, c, then
in lowest order their motion is governed by the static Coulomb Lagrangian. We
investigate higher order corrections with an explicit control on the error
terms. The Darwin correction, order (v/c)^2, has been proved previously. In
this contribution we obtain the dissipative corrections due to radiation
damping, which are of order (v/c)^3 relative to the Coulomb dynamics. If all
particles have the same charge-to-mass ratio, the dissipation would vanish at
that order.
|
0102004v1
|
2000-02-23
|
Dynamics of Kinks in One- and Two- Dimensional Hyperbolic Models with Quasi-Discrete Nonlinearities
|
We study the evolution of fronts in the Klein-Gordon equation when the
nonlinear term is non-homogeneous. Extending previous works on homogeneous
nonlinear terms, we describe the derivation of an equation governing the front
motion, which is strongly nonlinear, and, for the two-dimensional case,
generalizes the damped Born-Infeld equation. We study the motion of one- and
two-dimensional fronts, finding that the dynamics is richer than in the
homogeneous reaction term case.
|
0002043v1
|
2000-04-20
|
Spontaneous pattern formation in driven nonlinear lattice
|
We demonstrate the spontaneous formation of spatial patterns in
a damped, ac-driven cubic Klein-Gordon
lattice. These
patterns are composed of arrays of intrinsic localized modes
characteristic for nonlinear lattices. We analyze the modulation
instability leading to this spontaneous pattern formation. Our
calculation of the modulational instability is applicable in one
and two-dimensional lattices, however in the analyses of the
emerging patterns we concentrate particularly on the two-dimensional case.
|
0004035v1
|
2000-08-18
|
Correlations and fluctuations of matrix elements and cross sections
|
The fluctuations and correlations of matrix elements of cross sections are
investigated in open systems that are chaotic in the classical limit. The form
of the correlation functions is discussed within a statistical analysis and
tested in calculations for a damped quantum kicked rotator. We briefly comment
on the modifications expected for systems with slowly decaying correlations, a
typical feature in mixed phase spaces.
|
0008023v1
|
2001-04-26
|
Statistical Theory for Incoherent Light Propagation in Nonlinear Media
|
A novel statistical approach based on the Wigner transform is proposed for
the description of partially incoherent optical wave dynamics in nonlinear
media. An evolution equation for the Wigner transform is derived from a
nonlinear Schrodinger equation with arbitrary nonlinearity. It is shown that
random phase fluctuations of an incoherent plane wave lead to a Landau-like
damping effect, which can stabilize the modulational instability. In the limit
of the geometrical optics approximation, incoherent, localized, and stationary
wave-fields are shown to exist for a wide class of nonlinear media.
|
0104063v2
|
2001-06-13
|
Power fluctuations in a driven damped chaotic pendulum
|
In this paper we investigate the power fluctuations in a driven, dampted
pendulum. When the motion of the pendulum is chaotic, the average power
supplied by the driving force is equal to the average dissipated power only for
an infinite long time period. We measure the fluctuations of the supplied power
during a time equal to the period of the driving force. Negative power
fluctuations occur and we estimate their probability. In a chaotic state the
histogram of the power distribution is broad and continuous although bounded.
For a value of the power not too close to the edge of the distribution the
Fluctuation Theorem of Gallavotti and Cohen is approximately satisfied.
|
0106016v1
|
2001-07-06
|
Soliton ratchets
|
The mechanism underlying the soliton ratchet, both in absence and in presence
of noise, is investigated. We show the existence of an asymmetric internal mode
on the soliton profile which couples, trough the damping in the system, to the
soliton translational mode. Effective soliton transport is achieved when the
internal mode and the external force are phase locked. We use as working model
a generalized double sine-Gordon equation. The phenomenon is expected to be
valid for generic soliton systems.
|
0107011v1
|
2001-07-18
|
Effects of Transport Memory and Nonlinear Damping in a Generalized Fisher's Equation
|
Memory effects in transport require, for their incorporation into reaction
diffusion investigations, a generalization of traditional equations. The
well-known Fisher's equation, which combines diffusion with a logistic
nonlinearity, is generalized to include memory effects and traveling wave
solutions of the equation are found. Comparison is made with alternate
generalization procedures.
|
0107043v1
|
2002-03-05
|
Broken symmetries and pattern formation in two-frequency forced Faraday waves
|
We exploit the presence of approximate (broken) symmetries to obtain general
scaling laws governing the process of pattern formation in weakly damped
Faraday waves. Specifically, we consider a two-frequency forcing function and
trace the effects of time translation, time reversal and Hamiltonian structure
for three illustrative examples: hexagons, two-mode superlattices, and two-mode
rhomboids. By means of explicit parameter symmetries, we show how the size of
various three-wave resonant interactions depends on the frequency ratio m:n and
on the relative temporal phase of the two driving terms. These symmetry-based
predictions are verified for numerically calculated coefficients, and help
explain the results of recent experiments.
|
0203004v1
|
2002-03-09
|
One-fluid description of turbulently flowing suspension
|
We suggested a one-fluid model of a turbulent dilute suspension which
accounts for the ``two-way'' fluid-particle interactions by $k$-dependent
effective density of suspension and additional damping term in the
Navier-Stokes equation. We presented analytical description of the particle
modification of turbulence including scale invariant suppression of a small $k$
part of turbulent spectrum (independent of the particle response time) and
possible enhancemenent of large $k$ region [up to the factor $(1+\phi)^{2/3}$].
Our results are in agreement with qualitative picture of isotropic homogeneous
turbulence of dilute suspensions previously observed in laboratory and
numerical experiments.
|
0203016v1
|
2002-04-11
|
Lorenz deterministic diffusion
|
The Lorenz 1963 dynamical system is known to reduce in the steady state to a
one-dimensional motion of a classical particle subjected to viscous damping in
a past history-dependent potential field. If the potential field is substituted
by a periodic function of the position, the resulting system shows a rich
dynamics where (standard) diffusive behaviours, ballistc motions and trapping
take place by varying the model control parameters. This system permits to
highlight the intimate relation between chaos and long-time deterministic
diffusion.
|
0204020v1
|
2002-12-30
|
Parametrically Driven Dark Solitons
|
We show that unlike the bright solitons, the parametrically driven kinks are
immune from instabilities for all dampings and forcing amplitudes; they can
also form stable bound states. In the undamped case, the two types of stable
kinks and their complexes can travel with nonzero velocities.
|
0212052v1
|
2003-03-31
|
Anholonomy and Geometrical Localization in Dynamical Systems
|
We characterize the geometrical and topological aspects of a dynamical system
by associating a geometric phase with a phase space trajectory. Using the
example of a nonlinear driven damped oscillator, we show that this phase is
resilient to fluctuations, responds to all bifurcations in the system, and also
finds new geometric transitions. Enriching the phase space description is a
novel phenomenon of ``geometrical localization'' which manifests itself as a
significant deviation from planar dynamics over a short time interval.
|
0303071v1
|
2003-08-05
|
Variational method for finding periodic orbits in a general flow
|
A variational principle for determining unstable periodic orbits of flows as
well as unstable spatio-temporally periodic solutions of extended systems is
proposed and implemented. An initial loop approximating a periodic solution is
evolved in the space of loops toward a true periodic solution by a minimization
of local errors along the loop. The ``\descent'' partial differential equation
that governs this evolution is an infinitesimal step version of the damped
Newton-Raphson iteration. The feasibility of the method is demonstrated by its
application to the H\'enon-Heiles system, the circular restricted three-body
problem, and the Kuramoto-Sivashinsky system in a weakly turbulent regime.
|
0308008v1
|
2003-09-08
|
Gibbs attractor: a chaotic nearly Hamiltonian system, driven by external harmonic force
|
A chaotic autonomous Hamiltonian systems, perturbed by small damping and
small external force, harmonically dependent on time, can acquire a strange
attractor with properties similar to that of the canonical distribution - the
Gibbs attractor. The evolution of the energy in such systems can be described
as the energy diffusion. For the nonlinear Pullen - Edmonds oscillator with two
degrees of freedom the properties of the Gibbs attractor and their dependence
on parameters of the perturbation are studied both analytically and
numerically.
|
0309026v1
|
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