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1997-10-30
|
Damping rate for transverse gluons with finite soft momentum in hot QCD
|
We calculate the damping rate for transverse gluons with {\nineti finite}
soft momentum to leading order in perturbative hot QCD. The internal momenta of
the one-loop contributing diagrams are soft. This means we have to use
effective vertices and propagators which incorporate the so-called hard thermal
loops. We expand the damping rate in powers of the incoming momentum and argue
that the series ought to converge within a finite radius of convergence. We
contrast such a behavior with the one obtained from a previous calculation that
produced a logarithmic behavior, a calculation based on letting the gluon
momentum come from the hard limit down towards the interior of the soft region.
This difference in behavior may point to interesting physics around some
`critical' region.
|
9710549v2
|
1998-07-21
|
An infrared singularity in the damping rate for longitudinal gluons in hot QCD
|
We calculate $\gamma_l(0)$, the damping rate for longitudinal on-shell gluons
with zero momentum in hot QCD using the hard-thermal-loop (htl) scheme. We find
it to be divergent in the infrared, which means that in this scheme
$\gamma_l(0)$ is different from $\gamma_t(0)$, the corresponding damping rate
for transverse gluons which is known to be finite. This result suggests that
the htl scheme is infrared sensitive and thus may need to be improved upon in
this sector. We discuss this issue after we present our calculation.
|
9807439v2
|
1998-09-25
|
Damping rates in the MSSM and electroweak baryogenesis
|
We present an analysis of the thermalization rate of Higgsinos and winos
based on the imaginary part of the two-point Green function in the {\it
unbroken} phase of the MSSM. We use improved propagators including resummation
of hard thermal loops and the thermalization rate is computed at the one-loop
level in the high temperature approximation. We find that the damping is
typically dominated by scattering with gauge bosons, resulting in a damping
rate of about $\gamma_{\Ht}\simeq 0.025T$, $\gamma_{\Wt}\simeq 0.065T$. The
contribution from scattering with scalars is relatively small. Implications for
baryogenesis are also discussed.
|
9809529v1
|
2006-10-27
|
The soft fermion dispersion relation at next-to-leading order in hot QED
|
We study next-to-leading order contributions to the soft static fermion
dispersion relation in hot QED. We derive an expression for the complete
next-to-leading order contribution to the retarded fermion self-energy. The
real and imaginary parts of this expression give the next-to-leading order
contributions to the mass and damping rate of the fermionic quasi-particle.
Many of the terms that are expected to contribute according to the traditional
power counting argument are actually subleading. We explain why the power
counting method over estimates the contribution from these terms. For the
electron damping rate in QED we obtain: $\gamma_{QED} = \frac{e^2
T}{4\pi}(2.70)$. We check our method by calculating the next-to-leading order
contribution to the damping rate for the case of QCD with two flavours and
three coulours. Our result agrees with the result obtained previously in the
literature. The numerical evaluation of the nlo contribution to the mass is
left to a future publication.
|
0610372v1
|
2007-03-26
|
Preheating and Affleck-Dine leptogenesis after thermal inflation
|
Previously, we proposed a model of low energy Affleck-Dine leptogenesis in
the context of thermal inflation. The lepton asymmetry is generated at the end
of thermal inflation, which occurs at a relatively low energy scale with the
Hubble parameter somewhere in the range $1 \keV \lesssim H \lesssim 1 \MeV$.
Thus Hubble damping will be ineffective in bringing the Affleck-Dine field into
the lepton conserving region near the origin, leaving the possibility that the
lepton number could be washed out. Previously, we suggested that preheating
could damp the amplitude of the Affleck-Dine field allowing conservation of the
lepton number. In this paper, we demonstrate numerically that preheating does
efficiently damp the amplitude of the Affleck-Dine field and that the lepton
number is conserved as the result. In addition to demonstrating a crucial
aspect of our model, it also opens the more general possibility of low energy
Affleck-Dine baryogenesis.
|
0703275v1
|
1996-03-14
|
Dissipation and Topologically Massive Gauge Theories in Pseudoeuclidean Plane
|
In the pseudo-euclidean metrics Chern-Simons gauge theory in the infrared
region is found to be associated with dissipative dynamics. In the infrared
limit the Lagrangian of 2+1 dimensional pseudo-euclidean topologically massive
electrodynamics has indeed the same form of the Lagrangian of the damped
harmonic oscillator. On the hyperbolic plane a set of two damped harmonic
oscillators, each other time-reversed, is shown to be equivalent to a single
undamped harmonic oscillator. The equations for the damped oscillators are
proven to be the same as the ones for the Lorentz force acting on two particles
carrying opposite charge in a constant magnetic field and in the electric
harmonic potential. This provides an immediate link with Chern-Simons-like
dynamics of Bloch electrons in solids propagating along the lattice plane with
hyperbolic energy surface. The symplectic structure of the reduced theory is
finally discussed in the Dirac constrained canonical formalism.
|
9603092v1
|
2002-08-31
|
Neutrino damping rate at finite temperature and density
|
A first principle derivation is given of the neutrino damping rate in
real-time thermal field theory. Starting from the discontinuity of the neutrino
self energy at the two loop level, the damping rate can be expressed as
integrals over space phase of amplitudes squared, weighted with statistical
factors that account for the possibility of particle absorption or emission
from the medium. Specific results for a background composed of neutrinos,
leptons, protons and neutrons are given. Additionally, for the real part of the
dispersion relation we discuss the relation between the results obtained from
the thermal field theory, and those obtained by the thermal average of the
forward scattering amplitude.
|
0209006v1
|
2004-10-20
|
Ergodicity for the weakly damped stochastic non-linear Schrödinger equations
|
We study a damped stochastic non-linear Schr\"{o}dinger (NLS) equation driven
by an additive noise. It is white in time and smooth in space. Using a coupling
method, we establish convergence of the Markovian transition semi-group toward
a unique invariant probability measure. This kind of method was originally
developped to prove exponential mixing for strongly dissipative equations such
as the Navier-Stokes equations. We consider here a weakly dissipative equation,
the damped nonlinear Schr\"{o}dinger equation in the one dimensional cubic
case. We prove that the mixing property holds and that the rate of convergence
to equilibrium is at least polynomial of any power.
|
0410443v2
|
2006-07-30
|
Non-autonomous dynamics of wave equations with nonlinear damping and critical nonlinearity
|
The authors consider non-autonomous dynamical behavior of wave-type
evolutionary equations with nonlinear damping and critical nonlinearity. These
type of waves equations are formulated as non-autonomous dynamical systems
(namely, cocycles). A sufficient and necessary condition for the existence of
pullback attractors is established for norm-to-weak continuous non-autonomous
dynamical systems, in terms of pullback asymptotic compactness or pullback
$\kappa-$contraction criteria. A technical method for verifying pullback
asymptotic compactness, via contractive functions, is devised. These results
are then applied to the wave-type evolutionary equations with nonlinear damping
and critical nonlinearity, to obtain the existence of pullback attractors. The
required pullback asymptotic compactness for the existence of pullback
attractors is fulfilled by some new a priori estimates for concrete wave type
equations arising from applications. Moreover, the pullback
$\kappa-$contraction criterion for the existence of pullback attractors is of
independent interest.
|
0607774v3
|
2000-09-28
|
Quantization of Damped Harmonic Oscillator, Thermal Field Theories and q-Groups
|
We study the canonical quantization of the damped harmonic oscillator by
resorting to the realization of the q-deformation of the Weyl-Heisenberg
algebra (q-WH) in terms of finite difference operators. We relate the damped
oscillator hamiltonian to the q-WH algebra and to the squeezing generator of
coherent states theory. We also show that the q-WH algebra is the natural
candidate to study thermal field theory. The well known splitting, in the
infinite volume limit, of the space of physical states into unitarily
inequivalent representations of the canonical commutation relations is briefly
commented upon in relation with the von Neumann theorem in quantum mechanics
and with q-WH algebra.
|
0009036v1
|
2001-11-14
|
Soliton-radiation coupling in the parametrically driven, damped nonlinear Schrödinger equation
|
We use the Riemann-Hilbert problem to study the interaction of the soliton
with radiation in the parametrically driven, damped nonlinear Schr\"odinger
equation. The analysis is reduced to the study of a finite-dimensional
dynamical system for the amplitude and phase of the soliton and the complex
amplitude of the long-wavelength radiation. In contrast to previously utilised
Inverse Scattering-based perturbation techniques, our approach is valid for
arbitrarily large driving strengths and damping coefficients. We show that,
contrary to suggestions made in literature, the complexity observed in the
soliton's dynamics cannot be accounted for just by its coupling to the
long-wavelength radiation.
|
0111034v1
|
2002-02-12
|
Landau Damping and Coherent Structures in Narrow-Banded 1+1 Deep Water Gravity Waves
|
We study the nonlinear energy transfer around the peak of the spectrum of
surface gravity waves by taking into account nonhomogeneous effects. In the
narrow-banded approximation the kinetic equation resulting from a
nonhomogeneous wave field is a Vlasov-Poisson type equation which includes at
the same time the random version of the Benjamin-Feir instability and the
Landau damping phenomenon. We analytically derive the values of the Phillips'
constant $\alpha$ and the enhancement factor $\gamma$ for which the
narrow-banded approximation of the JONSWAP spectrum is unstable. By performing
numerical simulations of the nonlinear Schr\"{o}dinger equation we check the
validity of the prediction of the related kinetic equation. We find that the
effect of Landau damping is to suppress the formation of coherent structures.
The problem of predicting freak waves is briefly discussed.
|
0202026v1
|
2005-10-24
|
Stability of a nonlinear oscillator with random damping
|
A noisy damping parameter in the equation of motion of a nonlinear oscillator
renders the fixed point of the system unstable when the amplitude of the noise
is sufficiently large. However, the stability diagram of the system can not be
predicted from the analysis of the moments of the linearized equation. In the
case of a white noise, an exact formula for the Lyapunov exponent of the system
is derived. We then calculate the critical damping for which the {\em
nonlinear} system becomes unstable. We also characterize the intermittent
structure of the bifurcated state above threshold and address the effect of
temporal correlations of the noise by considering an Ornstein-Uhlenbeck noise.
|
0510063v1
|
2006-10-20
|
Vibration of Generalized Double Well Oscillators
|
We have applied the Melnikov criterion to examine a global homoclinic
bifurcation and transition to chaos in a case of a double well dynamical system
with a nonlinear fractional damping term and external excitation. The usual
double well Duffing potential having a negative square term and positive
quartic term has been generalized to a double well potential with a negative
square term and a positive one with an arbitrary real exponent $q > 2$. We have
also used a fractional damping term with an arbitrary power $p$ applied to
velocity which enables one to cover a wide range of realistic damping factors:
from dry friction $p \to 0$ to turbulent resistance phenomena $p=2$.
Using perturbation methods we have found a critical forcing amplitude $\mu_c$
above which the system may behave chaotically. Our results show that the
vibrating system is less stable in transition to chaos for smaller $p$
satisfying an exponential scaling low. The critical amplitude $\mu_c$ as an
exponential function of $p$.
The analytical results have been illustrated by numerical simulations using
standard nonlinear tools such as
Poincare maps and the maximal Lyapunov exponent. As usual for chosen system
parameters we have identified a chaotic motion above the critical Melnikov
amplitude $\mu_c$.
|
0610052v1
|
1998-06-18
|
Relativity Damps OPEP in Nuclear Matter
|
Using a relativistic Dirac-Brueckner analysis the OPEP contribution to the
ground state energy of nuclear matter is studied. In the study the pion is
derivative-coupled. We find that the role of the tensor force in the saturation
mechanism is substantially reduced compared to its dominant role in a usual
nonrelativistic treatment. We show that the damping of derivative-coupled OPEP
is actually due to the decrease of $M^*/M$ with increasing density. We point
out that if derivative-coupled OPEP is the preferred form of nuclear effective
lagrangian nonrelativistic treatment of nuclear matter is in trouble. Lacking
the notion of $M^*$ it cannot replicate the damping. We suggest an examination
of the feasibility of using pseudoscalar coupled $\pi$N interaction before
reaching a final conclusion about nonrelativistic treatment of nuclear matter.
|
9806054v1
|
1999-07-05
|
Damping of IVGDR - Fermi-liquid or Fermi-gas ?
|
Collisional relaxation rates of collective modes in nuclei are calculated
using the Levinson equation for the reduced density matrix with a memory
dependent collision term. Linearizing the collision integral two contribution
have to be distinguished, the one from the quasiparticle energy and the one
from occupation factors. The first one yields the known Landau formula of zero
sound damping and the second one leads to the Fermi gas model of Ref.1 with the
additional factor 3 in front of the frequencies. Adding both contribution we
obtain a final relaxation rate for the Fermi liquid model. Calculations of the
temperature dependence of the damping rates and of the shape evolution of IVGDR
are in good agreement with the experiment and show only minor differences
between both models.
|
9907012v1
|
2001-01-08
|
Collisional Damping of Giant Monopole and Quadrupole Resonances
|
Collisional damping widths of giant monopole and quadrupole excitations for
$^{120}$Sn and $^{208}$Pb at zero and finite temperatures are calculated within
Thomas-Fermi approximation by employing the microscopic in-medium
cross-sections of Li and Machleidt and the phenomenological Skyrme and Gogny
forces, and are compared with each other. The results for the collisional
widths of giant monopole and quadrupole vibrations at zero temperature as a
function of the mass number show that the collisional damping of giant monopole
vibrations accounts for about 30-40% of the observed widths at zero
temperature, while for giant quadrupole vibrations it accounts for only 20-30%
of the observed widths of zero temperature.
|
0101016v1
|
1996-12-08
|
Towards a Simple Model of Compressible Alfvenic Turbulence
|
A simple model collisionless, dissipative, compressible MHD (Alfvenic)
turbulence in a magnetized system is investigated. In contrast to more familiar
paradigms of turbulence, dissipation arises from Landau damping, enters via
nonlinearity, and is distributed over all scales. The theory predicts that two
different regimes or phases of turbulence are possible, depending on the ratio
of steepening to damping coefficient (m_1/m_2). For strong damping
(|m_1/m_2|<1), a regime of smooth, hydrodynamic turbulence is predicted. For
|m_1/m_2|>1, steady state turbulence does not exist in the hydrodynamic limit.
Rather, spikey, small scale structure is predicted.
|
9612005v2
|
1998-10-01
|
Mode-coupling and nonlinear Landau damping effects in auroral Farley-Buneman turbulence
|
The fundamental problem of Farley-Buneman turbulence in the auroral
$E$-region has been discussed and debated extensively in the past two decades.
In the present paper we intend to clarify the different steps that the auroral
$E$-region plasma has to undergo before reaching a steady state. The
mode-coupling calculation, for Farley-Buneman turbulence, is developed in order
to place it in perspective and to estimate its magnitude relative to the
anomalous effects which arise through the nonlinear wave-particle interaction.
This nonlinear effect, known as nonlinear ``Landau damping'' is due to the
coupling of waves which produces other waves which in turn lose energy to the
bulk of the particles by Landau damping. This leads to a decay of the wave
energy and consequently a heating of the plasma. An equation governing the
evolution of the field spectrum is derived and a physical interpration for each
of its terms is provided.
|
9810062v1
|
2000-08-20
|
Fabrication and Tolerance Issues and their Influence on Multi-Bunch Bbu and Emittance Dilution in the Construction of X-Band RDDS Linacs for the NLC
|
The main linacs of the Next Linear Collider (NLC) will contain several
thousand X-band RDDS (Rounded Damped Detuned Structures). The transverse
wakefield in the structures is reduced by detuning the modal frequencies such
that they destructively interfere and by four damping manifolds per structure
which provide weak damping. Errors in the fabrication of the individual cells
and in the alignment of the cells will reduce the cancellation of the modes.
Here, we calculate the tolerances on random errors in the synchronous
frequencies of the cells and the cell-to-cell alignment.
|
0008198v1
|
2003-09-17
|
A New Damping Mechanism in Non-linear Bubble Dynamics
|
Non-linear equations of radial motion of a gas bubble in a compressible
viscous liquid have been modified considering effects of viscosity and
compressibility more complete than all previous works. A new set of equations
has been derived including new terms resulted from consideration of the
viscosity and compressibility not only at the bubble interface, but also in the
bulk of liquid. The new equations are two non-linear coupled equations, which
can not be merged into one equation unlike all previously derived equations.
Numerical calculations have been performed considering effects of heat and mass
transfer at the bubble interface. The results indicate that the new terms
exhibit an important damping role at the collapse, so that their consideration
dramatically weakens the bubble rebounds after the collapse. Dependence of this
new damping mechanism to amplitude and frequency of the deriving pressure has
been investigated.
|
0309080v1
|
2003-11-26
|
Eigenvector Expansion and Petermann Factor for Ohmically Damped Oscillators
|
Correlation functions $C(t) \sim <\phi(t)\phi(0)>$ in ohmically damped
systems such as coupled harmonic oscillators or optical resonators can be
expressed as a single sum over modes $j$ (which are not power-orthogonal), with
each term multiplied by the Petermann factor (PF) $C_j$, leading to "excess
noise" when $|C_j| > 1$. It is shown that $|C_j| > 1$ is common rather than
exceptional, that $|C_j|$ can be large even for weak damping, and that the PF
appears in other processes as well: for example, a time-independent
perturbation $\sim\ep$ leads to a frequency shift $\sim \ep C_j$. The
coalescence of $J$ ($>1$) eigenvectors gives rise to a critical point, which
exhibits "giant excess noise" ($C_j \to \infty$). At critical points, the
divergent parts of $J$ contributions to $C(t)$ cancel, while time-independent
perturbations lead to non-analytic shifts $\sim \ep^{1/J}$.
|
0311127v2
|
2004-04-02
|
DAFNE injection system upgrade
|
High luminosity in DAFNE needs very high electron and positron currents
stored. A full energy (510 MeV) injection system composed by a full energy
electron and positron linac and an accumulator-damping ring is presently used.
The electron and positron beams, alternatively accelerated by the linac, are
injected and stacked in the accumulator with high efficiency thanks to its
large acceptance and short damping time. The damped beams are extracted and
transferred to the main ring through a long transfer line that has been built
inside already existing buildings. The refill time of the collider is limited
by the transfer line set-up change between the two different beams modes. In
this paper a transfer line modification is proposed in order to reduce the
switch time. A possible injection scheme for the main rings is also described.
|
0404010v1
|
2004-05-05
|
Langmuir wave self-focusing versus decay instability
|
Electron trapping in a finite amplitude Langmuir wave (LW) leads to a
frequency shift, \Delta\omega_{TP} < 0, and reduced Landau damping. These may
lead to modulational instability. Its growth rate and damping threshold, due to
escape of trapped electrons at rate \nu, are calculated for the first time in
the short wavelength regime. If the background plasma is in thermal
equilibrium, it is shown that this trapped particle modulational instability
(TPMI) is not possible when k \lambda_D > 0.46, while for 0.33 < k \lambda_D <
0.46, TPMI requires that the fluctuation wavevector have a component
perpendicular to k, the LW wavevector, with \lambda_D the electron Debye
length. Its nonlinear evolution leads to self-focusing. Comparison is made with
a re-evaluated LW ion acoustic decay instability (LDI): compared to classical
estimates, the new LDI threshold is lowered by primary LW \Delta\omega_{TP}
since frequency matching leads to wavenumber and hence damping reduction of the
daughter LW. For parameters estimates relevant to a recent stimulated Raman
scatter experiment (Kline et al., submitted to PRL), the LDI and TPMI
thresholds cross in the range 0.28 < k \lambda_D < 0.34, consistent with the
observed LDI regime change. However, if \nu exceeds a critical value, estimated
to be order 1% of the electron plasma frequency, then TPMI is not possible at
any wavenumber.
|
0405015v1
|
2005-06-16
|
Mesoscale Quantization and Self-Organized Stability
|
In the world of technology, one of the most important forms of friction is
that of rolling friction. Yet it is one of the least studied of all the known
forms of energy dissipation. In the present experiments we investigate the
oscillatory free-decay of a rigid cube, whose side-length is less than the
diameter of the rigid cylinder on which it rests. The resulting free-decay is
one of harmonic motion with damping. The non-dissipative character of the
oscillation yields to a linear differential equation; however, the damping is
found to involve more than a deterministic nonlinearity. Dominated by rolling
friction, the damping is sensitive to the material properties of the contact
surfaces. For `clean' surfaces of glass on glass, the decay shows features of
mesoscale quantization and self-organized stability.
|
0506143v1
|
2006-10-31
|
Ultimate parameters of the photon collider at the ILC
|
At linear colliders, the e+e- luminosity is limited by beam-collision
effects, which determine the required emittances of beams in damping rings
(DRs). While in gamma-gamma collisions at the photon collider, these effects
are absent, and so smaller emittances are desirable. In present damping rings
designs, nominal DR parameters correspond to those required for e+e-
collisions. In this note, I would like to stress once again that as soon as we
plan the photon-collider mode of ILC operation, the damping-ring emittances are
dictated by the photon-collider requirements--namely, they should be as small
as possible. This can be achieved by adding more wigglers to the DRs; the
incremental cost is easily justified by a considerable potential improvement of
the gamma-gamma luminosity. No expert analysis exists as of yet, but it seems
realistic to obtain a factor five increase of the gamma-gamma luminosity
compared to the ``nominal'' DR design.
|
0610285v1
|
2006-04-27
|
On the weak solutions of the McKendrick equation: Existence of demography cycles
|
We develop the qualitative theory of the solutions of the McKendrick partial
differential equation of population dynamics. We calculate explicitly the weak
solutions of the McKendrick equation and of the Lotka renewal integral equation
with time and age dependent birth rate. Mortality modulus is considered age
dependent. We show the existence of demography cycles. For a population with
only one reproductive age class, independently of the stability of the weak
solutions and after a transient time, the temporal evolution of the number of
individuals of a population is always modulated by a time periodic function.
The periodicity of the cycles is equal to the age of the reproductive age
class, and a population retains the memory from the initial data through the
amplitude of oscillations. For a population with a continuous distribution of
reproductive age classes, the amplitude of oscillation is damped. The
periodicity of the damped cycles is associated with the age of the first
reproductive age class. Damping increases as the dispersion of the fertility
function around the age class with maximal fertility increases. In general, the
period of the demography cycles is associated with the time that a species
takes to reach the reproductive maturity.
|
0604035v2
|
1999-03-05
|
Exact Diagonalization of Two Quantum Models for the Damped Harmonic Oscillator
|
The damped harmonic oscillator is a workhorse for the study of dissipation in
quantum mechanics. However, despite its simplicity, this system has given rise
to some approximations whose validity and relation to more refined descriptions
deserve a thorough investigation. In this work, we apply a method that allows
us to diagonalize exactly the dissipative Hamiltonians that are frequently
adopted in the literature. Using this method we derive the conditions of
validity of the rotating-wave approximation (RWA) and show how this approximate
description relates to more general ones. We also show that the existence of
dissipative coherent states is intimately related to the RWA. Finally, through
the evaluation of the dynamics of the damped oscillator, we notice an important
property of the dissipative model that has not been properly accounted for in
previous works; namely, the necessity of new constraints to the application of
the factorizable initial conditions.
|
9903022v2
|
1999-04-06
|
Nonclassical correlations in damped quantum solitons
|
Using cumulant expansion in Gaussian approximation, the internal quantum
statistics of damped soliton-like pulses in Kerr media are studied numerically,
considering both narrow and finite bandwidth spectral pulse components. It is
shown that the sub-Poissonian statistics can be enhanced, under certain
circumstances, by absorption, which damps out some destructive interferences.
Further, it is shown that both the photon-number correlation and the
correlation of the photon-number variance between different pulse components
can be highly nonclassical even for an absorbing fiber. Optimum frequency
windows are determined in order to realize strong nonclassical behavior, which
offers novel possibilities of using solitons in optical fibers as a source of
nonclassically correlated light beams.
|
9904017v2
|
1999-04-19
|
Quantum theory of fluctuations in a cold damped accelerometer
|
We present a quantum network approach to real high sensitivity measurements.
Thermal and quantum fluctuations due to active as well as passive elements are
taken into account. The method is applied to the analysis of the capacitive
accelerometer using the cold damping technique, developed for fundamental
physics in space by ONERA and the ultimate limits of this instrument are
discussed. It is confirmed in this quantum analysis that the cold damping
technique allows one to control efficiently the test mass motion without
degrading the noise level.
|
9904073v2
|
2000-07-04
|
Stochastic limit approximation for rapidly decaying systems
|
The stochastic limit approximation method for ``rapid'' decay is presented,
where the damping rate \gamma is comparable to the system frequency \Omega,
i.e., \gamma \sim \Omega, whereas the usual stochastic limit approximation is
applied only to the weak damping situation \gamma << \Omega. The key formulas
for rapid decay are very similar to those for weak damping, but the dynamics is
quite different. From a microscopic Hamiltonian, the spin-boson model, a Bloch
equation containing two independent time scales is derived. This is a useful
method to extract the minimal dissipative dynamics at high temperature kT >>
\hbar\Omega and the master equations obtained are of the Lindblad form even for
the Caldeira-Leggett model. The validity of the method is confirmed by
comparing the master equation derived through this method with the exact one.
|
0007007v2
|
2000-08-01
|
Full mechanical characterization of a cold damped mirror
|
We describe an experiment in which we have used a cold damping feedback
mechanism to reduce the thermal noise of a mirror around its mechanical
resonance frequency. The monitoring of the brownian motion of the mirror allows
to apply an additional viscous force without any thermal fluctuations
associated. This scheme has been experimentally implemented with the radiation
pressure of an intensity-modulated laser beam. Large noise reductions, up to 30
dB, have been obtained. We have also checked the mechanical response of the
cold damped mirror, and monitored its transient evolution between the cooled
regime and the room temperature equilibrium. A simple theoretical model allows
to fully explain the experimental results. A possible application to the active
cooling of the violin modes in a gravitational-wave interferometer is
discussed.
|
0008004v1
|
2003-11-05
|
Exact decoherence to pointer states in free open quantum systems is universal
|
In this paper it is shown that exact decoherence to minimal uncertainty
Gaussian pointer states is generic for free quantum particles coupled to a heat
bath. More specifically, the paper is concerned with damped free particles
linearly coupled under product initial conditions to a heat bath at arbitrary
temperature, with arbitrary coupling strength and spectral densities covering
the Ohmic, subohmic, and supraohmic regime. Then it is true that there exists a
time t_c such that for times t>t_c the state can always be exactly represented
as a mixture (convex combination) of particular minimal uncertainty Gaussian
states, regardless of and independent from the initial state. This exact
`localisation' is hence not a feature specific to high temperatures and weak
damping limit, but is rather a generic property of damped free particles.
|
0311022v3
|
2004-07-30
|
Kraus representation of damped harmonic oscillator and its application
|
By definition, the Kraus representation of a harmonic oscillator suffering
from the environment effect, modeled as the amplitude damping or the phase
damping, is directly given by a simple operator algebra solution. As examples
and applications, we first give a Kraus representation of a single qubit whose
computational basis states are defined as bosonic vacuum and single particle
number states. We further discuss the environment effect on qubits whose
computational basis states are defined as the bosonic odd and even coherent
states. The environment effects on entangled qubits defined by two different
kinds of computational basis are compared with the use of fidelity.
|
0407263v2
|
2005-01-31
|
The non dissipative damping of the Rabi oscillations as a "which-path" information
|
Rabi oscillations may be viewed as an interference phenomenon due to a
coherent superposition of different quantum paths, like in the Young's two-slit
experiment. The inclusion of the atomic external variables causes a non
dissipative damping of the Rabi oscillations. More generally, the atomic
translational dynamics induces damping in the correlation functions which
describe non classical behaviors of the field and internal atomic variables,
leading to the separability of these two subsystems. We discuss on the
possibility of interpreting this intrinsic decoherence as a "which-way"
information effect and we apply to this case a quantitative analysis of the
complementarity relation as introduced by Englert [Phys. Rev. Lett.
\textbf{77}, 2154 (1996)].
|
0501181v1
|
2006-01-12
|
Driven harmonic oscillator as a quantum simulator for open systems
|
We show theoretically how a driven harmonic oscillator can be used as a
quantum simulator for non-Markovian damped harmonic oscillator. In the general
framework, the results demonstrate the possibility to use a closed system as a
simulator for open quantum systems. The quantum simulator is based on sets of
controlled drives of the closed harmonic oscillator with appropriately tailored
electric field pulses. The non-Markovian dynamics of the damped harmonic
oscillator is obtained by using the information about the spectral density of
the open system when averaging over the drives of the closed oscillator. We
consider single trapped ions as a specific physical implementation of the
simulator, and we show how the simulator approach reveals new physical insight
into the open system dynamics, e.g. the characteristic quantum mechanical
non-Markovian oscillatory behavior of the energy of the damped oscillator,
usually obtained by the non-Lindblad-type master equation, can have a simple
semiclassical interpretation.
|
0601081v2
|
2006-07-31
|
Nonadiabatic Transitions for a Decaying Two-Level-System: Geometrical and Dynamical Contributions
|
We study the Landau-Zener Problem for a decaying two-level-system described
by a non-hermitean Hamiltonian, depending analytically on time. Use of a
super-adiabatic basis allows to calculate the non-adiabatic transition
probability P in the slow-sweep limit, without specifying the Hamiltonian
explicitly. It is found that P consists of a ``dynamical'' and a
``geometrical'' factors. The former is determined by the complex adiabatic
eigenvalues E_(t), only, whereas the latter solely requires the knowledge of
\alpha_(+-)(t), the ratio of the components of each of the adiabatic
eigenstates. Both factors can be split into a universal one, depending only on
the complex level crossing points, and a nonuniversal one, involving the full
time dependence of E_(+-)(t). This general result is applied to the
Akulin-Schleich model where the initial upper level is damped with damping
constant $\gamma$. For analytic power-law sweeps we find that Stueckelberg
oscillations of P exist for gamma smaller than a critical value gamma_c and
disappear for gamma > gamma_c. A physical interpretation of this behavior will
be presented by use of a damped harmonic oscillator.
|
0607221v1
|
2007-05-05
|
Damped Corrections to Inflationary Spectra from a Fluctuating Cutoff
|
We reconsider trans-Planckian corrections to inflationary spectra by taking
into account a physical effect which has been overlooked and which could have
important consequences. We assume that the short length scale characterizing
the new physics is endowed with a finite width, the origin of which could be
found in quantum gravity. As a result, the leading corrections responsible for
superimposed osillations in the CMB temperature anisotropies are generically
damped by the blurring of the UV scale. To determine the observational
ramifications of this damping, we compare it to that which effectively occurs
when computing the angular power spectrum of temperature anisotropies. The
former gives an overall change of the oscillation amplitudes whereas the latter
depends on the angular scale. Therefore, in principle they could be
distinguished. In any case, the observation of superimposed oscillations would
place tight constraint on the variance of the UV cutoff.
|
0705.0747v1
|
2007-05-10
|
Magnetization oscillations induced by a spin-polarized current in a point-contact geometry: mode hopping and non-linear damping effects
|
In this paper we study magnetization excitations induced in a thin extended
film by a spin-polarized dc-current injected through a point contact in the
current-perpendicular-to-plane (CPP) geometry. Using full-scale micromagnetic
simulations, we demonstrate that in addition to the oscillations of the
propagating wave type, there exist also two localized oscillation modes. The
first localized mode has a relatively homogeneous magnetization structure of
its kernel and corresponds to the so called 'bullet' predicted analytically by
Slavin and Tiberkevich (Phys. Rev. Lett., 95 (2005) 237201). Magnetization
pattern of the second localized mode kernel is highly inhomogeneous, leading to
a much smaller power of magnetoresistance oscillations caused by this mode. We
have also studied the influence of a non-linear damping for this system and
have found the following main qualitative effects: (i) the appearance of
frequency jumps within the existence region of the propagating wave mode and
(ii) the narrowing of the current region where the 'bullet' mode exists, until
this mode completely disappears for a sufficiently strong non-linear damping.
|
0705.1515v1
|
2007-05-27
|
Amplitude Damping for single-qubit System with single-qubit mixed-state Environment
|
We study a generalized amplitude damping channel when environment is
initially in the single-qubit mixed state. Representing the affine
transformation of the generalized amplitude damping by a three-dimensional
volume, we plot explicitly the volume occupied by the channels simulatable by a
single-qubit mixed-state environment. As expected, this volume is embedded in
the total volume by the channels which is simulated by two-qubit enviroment.
The volume ratio is approximately 0.08 which is much smaller than 3/8, the
volume ratio for generalized depolarizing channels.
|
0705.3952v3
|
2007-06-01
|
The geometrical quantity in damped wave equations on a square
|
The energy in a square membrane $\Omega$ subject to constant viscous damping
on a subset $\omega\subset \Omega$ decays exponentially in time as soon as
$\omega$ satisfies a geometrical condition known as the "Bardos-Lebeau-Rauch"
condition. The rate $\tau(\omega)$ of this decay satisfies $\tau(\omega)= 2
\min(-\mu(\omega), g(\omega))$ (see Lebeau [Math. Phys. Stud. 19 (1996)
73-109]). Here $\mu(\omega)$ denotes the spectral abscissa of the damped wave
equation operator and $g(\omega)$ is a number called the geometrical quantity
of $\omega$ and defined as follows. A ray in $\Omega$ is the trajectory
generated by the free motion of a mass-point in $\Omega$ subject to elastic
reflections on the boundary. These reflections obey the law of geometrical
optics. The geometrical quantity $g(\omega)$ is then defined as the upper limit
(large time asymptotics) of the average trajectory length. We give here an
algorithm to compute explicitly $g(\omega)$ when $\omega$ is a finite union of
squares.
|
0706.0172v1
|
2007-06-08
|
Kinetic-Ion Simulations Addressing Whether Ion Trapping Inflates Stimulated Brillouin Backscattering Reflectivities
|
An investigation of the possible inflation of stimulated Brillouin
backscattering (SBS) due to ion kinetic effects is presented using
electromagnetic particle simulations and integrations of three-wave
coupled-mode equations with linear and nonlinear models of the nonlinear ion
physics. Electrostatic simulations of linear ion Landau damping in an ion
acoustic wave, nonlinear reduction of damping due to ion trapping, and
nonlinear frequency shifts due to ion trapping establish a baseline for
modeling the electromagnetic SBS simulations. Systematic scans of the laser
intensity have been undertaken with both one-dimensional particle simulations
and coupled-mode-equations integrations, and two values of the electron-to-ion
temperature ratio (to vary the linear ion Landau damping) are considered. Three
of the four intensity scans have evidence of SBS inflation as determined by
observing more reflectivity in the particle simulations than in the
corresponding three-wave mode-coupling integrations with a linear ion-wave
model, and the particle simulations show evidence of ion trapping.
|
0706.1236v1
|
2007-06-29
|
Driving-dependent damping of Rabi oscillations in two-level semiconductor systems
|
We propose a mechanism to explain the nature of the damping of Rabi
oscillations with increasing driving-pulse area in localized semiconductor
systems, and have suggested a general approach which describes a coherently
driven two-level system interacting with a dephasing reservoir. Present
calculations show that the non-Markovian character of the reservoir leads to
the dependence of the dephasing rate on the driving-field intensity, as
observed experimentally. Moreover, we have shown that the damping of Rabi
oscillations might occur as a result of different dephasing mechanisms for both
stationary and non-stationary effects due to coupling to the environment.
Present calculated results are found in quite good agreement with available
experimental measurements.
|
0706.4372v1
|
2007-08-06
|
Collisionsless amplifying of longitudinal electron waves in two-stream plasma
|
To better understanding the principal features of collisionless
damping/growing plasma waves we have implemented a demonstrative calculation
for the simplest cases of electron waves in two-stream plasmas with the
delta-function type electron velocity distribution function of each of the
streams with velocities v(1) and v(2). The traditional dispersion equation is
reduced to an algebraic 4th order equation, for which numerical solutions are
presented for a variant of equal stream densities. In the case of uniform
half-infinite slab one finds two dominant type solutions: non-damping forward
waves and forward complex conjugated exponentially both damping and growing
waves. Beside it in this case there is no necessity of calculation any
logarithmically divergent indefinite integrals. The possibility of wave
amplifying might be useful in practical applications.
|
0708.0767v1
|
2007-08-09
|
The Highly Damped Quasinormal Modes of Extremal Reissner-Nordström and Reissner-Nordström-de Sitter Black Holes
|
We analyze in detail the highly damped quasinormal modes of $D$-dimensional
extremal Reissner-Nordstr$\ddot{\rm{o}}$m and
Reissner-Nordstr$\ddot{\rm{o}}$m-de Sitter black holes. We only consider the
extremal case where the event horizon and the Cauchy inner horizon coincide. We
show that, even though the topology of the Stokes/anti-Stokes lines in the
extremal case is different than the non-extremal case, the highly damped
quasinormal mode frequencies of extremal black holes match exactly with the
extremal limit of the non-extremal black hole quasinormal mode frequencies.
|
0708.1333v2
|
2007-08-28
|
Resonantly damped surface and body MHD waves in a solar coronal slab with oblique propagation
|
The theory of magnetohydrodynamic (MHD) waves in solar coronal slabs in a
zero-$\beta$ configuration and for parallel propagation of waves does not allow
the existence of surface waves. When oblique propagation of perturbations is
considered both surface and body waves are able to propagate. When the
perpendicular wave number is larger than a certain value, the body kink mode
becomes a surface wave. In addition, a sausage surface mode is found below the
internal cut-off frequency. When non-uniformity in the equilibrium is included,
surface and body modes are damped due to resonant absorption. In this paper,
first, a normal-mode analysis is performed and the period, the damping rate,
and the spatial structure of eigenfunctions are obtained. Then, the
time-dependent problem is solved, and the conditions under which one or the
other type of mode is excited are investigated.
|
0708.3783v1
|
2007-09-11
|
Teleportation of qubit states through dissipative channels: Conditions for surpassing the no-cloning limit
|
We investigate quantum teleportation through dissipative channels and
calculate teleportation fidelity as a function of damping rates. It is found
that the average fidelity of teleportation and the range of states to be
teleported depend on the type and rate of the damping in the channel. Using the
fully entangled fraction, we derive two bounds on the damping rates of the
channels: one is to beat the classical limit and the second is to guarantee the
non-existence of any other copy with better fidelity. Effect of the initially
distributed maximally entangled state on the process is presented; and the
concurrence and the fully entangled fraction of the shared states are
discussed. We intend to show that prior information on the dissipative channel
and the range of qubit states to be teleported is helpful for the evaluation of
the success of teleportation, where success is defined as surpassing the
fidelity limit imposed by the fidelity of 1-to-2 optimal cloning machine for
the specific range of qubits.
|
0709.1662v1
|
2007-10-03
|
Global stability of travelling fronts for a damped wave equation with bistable nonlinearity
|
We consider the damped wave equation \alpha u_tt + u_t = u_xx - V'(u) on the
whole real line, where V is a bistable potential. This equation has travelling
front solutions of the form u(x,t) = h(x-st) which describe a moving interface
between two different steady states of the system, one of which being the
global minimum of V. We show that, if the initial data are sufficiently close
to the profile of a front for large |x|, the solution of the damped wave
equation converges uniformly on R to a travelling front as t goes to plus
infinity. The proof of this global stability result is inspired by a recent
work of E. Risler and relies on the fact that our system has a Lyapunov
function in any Galilean frame.
|
0710.0794v1
|
2007-12-19
|
Cosmic String Dynamics and Evolution in Warped Spacetime
|
We study the dynamics and evolution of Nambu-Goto strings in a warped
spacetime, where the warp factor is a function of the internal coordinates
giving rise to a `throat' region. The microscopic equations of motion for
strings in this background include potential and friction terms, which attract
the strings towards the bottom of the warping throat. However, by considering
the resulting macroscopic equations for the velocities of strings in the
vicinity of the throat, we note the absence of enough classical damping to
guarantee that the strings actually reach the warped minimum and stabilise
there. Instead, our classical analysis supports a picture in which the strings
experience mere deflections and bounces around the tip, rather than strongly
damped oscillations. Indeed, 4D Hubble friction is inefficient in the internal
dimensions and there is no other classical mechanism known, which could provide
efficient damping. These results have potentially important implications for
the intercommuting probabilities of cosmic superstrings.
|
0712.3224v2
|
2007-12-20
|
The Critical Exponent of the Fractional Langevin Equation is $α_c\approx 0.402$
|
We investigate the dynamical phase diagram of the fractional Langevin
equation and show that critical exponents mark dynamical transitions in the
behavior of the system. For a free and harmonically bound particle the critical
exponent $\alpha_c= 0.402\pm 0.002$ marks a transition to a non-monotonic
under-damped phase. The critical exponent $\alpha_{R}=0.441...$ marks a
transition to a resonance phase, when an external oscillating field drives the
system. Physically, we explain these behaviors using a cage effect, where the
medium induces an elastic type of friction. Phase diagrams describing the
under-damped, the over-damped and critical frequencies of the fractional
oscillator, recently used to model single protein experiments, show behaviors
vastly different from normal.
|
0712.3407v1
|
2008-01-24
|
Particle Acceleration by Fast Modes in Solar Flares
|
We address the problem of particle acceleration in solar flares by fast modes
which may be excited during the reconnection and undergo cascade and are
subjected to damping. We extend the calculations beyond quasilinear
approximation and compare the acceleration and scattering by transit time
damping and gyroresonance interactions. We find that the acceleration is
dominated by the so called transit time damping mechanism. We estimate the
total energy transferred into particles, and show that our approach provides
sufficiently accurate results We compare this rate with energy loss rate.
Scattering by fast modes appears to be sufficient to prevent the protons from
escaping the system during the acceleration. Confinement of electrons, on the
other hand, requires the existence of plasma waves. Electrons can be
accelerated to GeV energies through the process described here for solar flare
conditions.
|
0801.3786v2
|
2008-02-07
|
Analysis of squeal noise and mode coupling instabilities including damping and gyroscopic effects
|
This paper deals with an audible disturbance known as automotive clutch
squeal noise from the viewpoint of friction-induced mode coupling instability.
Firstly, an auto-coupling model is presented showing a non-conservative
circulatory effect originating from friction forces. Secondly, the stability of
an equilibrium is investigated by determining the eigenvalues of the system
linearized equations. The effects of the circulatory and gyroscopic actions are
examined analytically and numerically to determine their influence on the
stability region. Separate and combined effects are analysed with and without
structural damping and important information is obtained on the role of each
parameter and their interactions regarding overall stability. Not only is
structural damping shown to be of primary importance, as reported in many
previous works, this article also highlights a particular relationship with
gyroscopic effects. A method of optimizing both the stability range and its
robustness with respect to uncertainty on system parameters is discussed after
which practical design recommendations are given.
|
0802.0923v1
|
2008-02-12
|
Nonlinear Saturation of g-modes in Proto-Neutron Stars: Quieting the Acoustic Engine
|
According to Burrows et al.'s acoustic mechanism for core-collapse supernova
explosions, the primary, l=1, g-mode in the core of the proto-neutron star is
excited to an energy of ~ 10^{50} ergs and damps by the emission of sound
waves. Here we calculate the damping of the primary mode by the parametric
instability, i.e., by nonlinear, 3-mode coupling between the low-order primary
mode and pairs of high-order g-modes. We show that the primary mode is strongly
coupled to highly resonant, neutrino damped pairs with n>10; such short
wavelength interactions cannot be resolved in the simulations. We find that the
parametric instability saturates the primary mode energy at ~10^{48} ergs, well
below the energy needed to drive an explosion. We therefore conclude that
acoustic power is unlikely to be energetically significant in core-collapse
supernova explosions.
|
0802.1522v3
|
2008-02-21
|
Gas Damping Coefficient Research for MEMS Comb Linear Vibration Gyroscope
|
Silicon-MEMS gyroscope is an important part of MEMS (Micro Electrical
Mechanical System). There are some disturb ignored in traditional gyroscope
that must be evaluated newly because of its smaller size (reach the level of
micron). In these disturb, the air pressure largely influences the performance
of MEMS gyroscope. Different air pressure causes different gas damping
coefficient for the MEMS comb linear vibration gyroscope and different gas
damping coefficient influences the quality factor of the gyroscope directive.
The quality factor influences the dynamic working bandwidth of the MEMS comb
linear vibration gyroscope, so it is influences the output characteristic of
the MEMS comb linear vibration gyroscope. The paper shows the relationship
between the air pressure and the output amplified and phase of the detecting
axis through analyzing the air pressure influence on the MEMS comb linear
vibration gyroscope. It discusses the influence on the frequency distribute and
quality factor of the MEMS comb linear vibration gyroscope for different air
pressure.
|
0802.3048v1
|
2008-03-03
|
Damped harmonic oscillator interpretation of the soft-state power spectra of Cyg X-1
|
We develop a model of an accretion disc in which the variability induced at a
given radius is governed by a damped harmonic oscillator at the corresponding
epicyclic frequency. That variability induces both linear and non-linear
responses in the locally emitted radiation. The total observed variability of a
source is the sum of these contributions over the disc radius weighted by the
energy dissipation rate at each radius. It is shown that this simple model,
which effectively has only three parameters including the normalization, can
explain the range of the power spectra observed from Cyg X-1 in the soft state.
Although a degeneracy between the black hole mass and the strength of the
damping does not allow a unique determination of the mass, we can still
constrain it to <16--20 solar masses. We also show that our model preserves the
observed linear rms-flux relationship even in the presence of the non-linear
flux response.
|
0803.0238v2
|
2008-03-05
|
The Secular Evolution of a Close Ring-Satellite System: The Excitation of Spiral Density Waves at a Nearby Gap Edge
|
The Lagrange planetary equations are used to study to secular evolution of a
small, eccentric satellite that orbits within a narrow gap in a broad,
self-gravitating planetary ring. These equations show that the satellite's
secular perturbations of the ring will excite a very long-wavelength spiral
density wave that propagates away from the gap's outer edge. The amplitude of
these waves, as well as their dispersion relation, are derived here. That
dispersion relation reveals that a planetary ring can sustain two types of
density waves: long waves that, in Saturn's A ring, would have wavelengths of
order 100 km, and short waves that tend to be very nonlinear and are expected
to quickly damp. The excitation of these waves also transports angular momentum
from the ring to the satellite in a way that damps the satellite's eccentricity
e, which also tends to reduce the amplitude of subsequent waves. The rate of
eccentricity damping due to this wave action is then compared to the rates at
which the satellite's Lindblad and corotation resonances alter the satellite's
e. These results are then applied to the gap-embedded Saturnian satellites Pan
and Daphnis, and the long-term stability of their eccentricities is assessed.
|
0803.0576v1
|
2008-03-06
|
Hypersound damping in vitreous silica measured by picosecond acoustics
|
The attenuation of longitudinal acoustic phonons up to frequencies nearing
250 GHz is measured in vitreous silica with a picosecond optical technique.
Taking advantage of interferences on the probe beam, difficulties encountered
in early pioneering experiments are alleviated. Sound damping at 250 GHz and
room temperature is consistent with relaxation dominated by anharmonic
interactions with the thermal bath, extending optical Brillouin scattering
data. Our result is at variance with claims of a recent deep-UV experiment
which reported a rapid damping increase beyond 100 GHz. A comprehensive picture
of the frequency dependence of sound attenuation in $v$-SiO$_2$ can be
proposed.
|
0803.0832v1
|
2008-03-07
|
Resonance distribution in open quantum chaotic systems
|
In order to study the resonance spectra of chaotic cavities subject to some
damping (which can be due to absorption or partial reflection at the
boundaries), we use a model of damped quantum maps. In the high-frequency
limit, the distribution of (quantum) decay rates is shown to cluster near a
``typical'' value, which is larger than the classical decay rate of the
corresponding damped ray dynamics. The speed of this clustering may be quite
slow, which could explain why it has not been detected in previous numerical
data.
|
0803.1075v4
|
2008-04-03
|
Single flux quantum circuits with damping based on dissipative transmission lines
|
We propose and demonstrate the functioning of a special Rapid Single Flux
Quantum (RSFQ) circuit with frequency-dependent damping. This damping is
achieved by shunting individual Josephson junctions by pieces of open-ended RC
transmission lines. Our circuit includes a toggle flip-flop cell, Josephson
transmission lines transferring single flux quantum pulses to and from this
cell, as well as DC/SFQ and SFQ/DC converters. Due to the desired
frequency-dispersion in the RC line shunts which ensures sufficiently low noise
at low frequencies, such circuits are well-suited for integrating with the
flux/phase Josephson qubit and enable its efficient control.
|
0804.0442v1
|
2008-05-14
|
Reconciling results of LSND, MiniBooNE and other experiments with soft decoherence
|
We propose an explanation of the LSND signal via quantum-decoherence of the
mass states, which leads to damping of the interference terms in the
oscillation probabilities. The decoherence parameters as well as their energy
dependence are chosen in such a way that the damping affects only oscillations
with the large (atmospheric) $\Delta m^2$ and rapidly decreases with the
neutrino energy. This allows us to reconcile the positive LSND signal with
MiniBooNE and other null-result experiments. The standard explanations of
solar, atmospheric, KamLAND and MINOS data are not affected. No new particles,
and in particular, no sterile neutrinos are needed. The LSND signal is
controlled by the 1-3 mixing angle $\theta_{13}$ and, depending on the degree
of damping, yields $0.0014 < \sin^2\theta_{13} < 0.034$ at $3\sigma$. The
scenario can be tested at upcoming $\theta_{13}$ searches: while the comparison
of near and far detector measurements at reactors should lead to a null-result
a positive signal for $\theta_{13}$ is expected in long-baseline accelerator
experiments. The proposed decoherence may partially explain the results of
Gallium detector calibrations and it can strongly affect supernova neutrino
signals.
|
0805.2098v1
|
2008-06-02
|
Observations of Solar Doppler Shift Oscillations with the EUV Imaging Spectrometer on Hinode
|
Damped Doppler shift oscillations have been observed in emission lines from
ions formed at flare temperatures with the Solar Ultraviolet Measurements of
Emitted Radiation spectrometer on the Solar and Heliospheric Observatory and
with the Bragg Crystal Spectrometer on Yohkoh. This Letter reports the
detection of low-amplitude damped oscillations in coronal emission lines formed
at much lower temperatures observed with the EUV Imaging Spectrometer on the
Hinode satellite. The oscillations have an amplitude of about 2 km/s, and a
period of around 35 min. The decay times show some evidence for a temperature
dependence with the lowest temperature of formation emission line (Fe XII
195.12 Angstroms) exhibiting a decay time of about 43 min, while the highest
temperature of formation emission line (Fe XV 284.16 Angstroms) shows no
evidence for decay over more than two periods of the oscillation. The data
appear to be consistent with slow magnetoacoustic standing waves, but may be
inconsistent with conductive damping.
|
0806.0265v1
|
2008-07-07
|
Using squeezed field to preserve two-atom entanglement against spontaneous emissions
|
Tunable interaction between two atoms in a cavity is realized by interacting
the two atoms with an extra controllable single-mode squeezed field. Such a
controllable interaction can be further used to control entanglement between
the two atoms against amplitude damping decoherence caused by spontaneous
emissions. For the independent amplitude damping decoherence channel,
entanglement will be lost completely without controls, while it can be
partially preserved by the proposed strategy. For the collective amplitude
damping decoherence channel, our strategy can enhance the entanglement compared
with the uncontrolled case when the entanglement of the uncontrolled stationary
state is not too large.
|
0807.0965v2
|
2008-07-17
|
Connecting high-redshift galaxy populations through observations of local Damped Lyman Alpha dwarf galaxies
|
I report on observations of the z=0.01 dwarf galaxy SBS1543+593 which is
projected onto the background QSO HS1543+5921. As a star-forming galaxy first
noted in emission, this dwarf is playing a pivotal role in our understanding of
high-redshift galaxy populations, because it also gives rise to a Damped Lyman
Alpha system. This enabled us to analyze, for the first time, the chemical
abundance of $\alpha$ elements in a Damped Lyman Alpha galaxy using both,
emission and absorption diagnostics. We find that the abundances agree with one
another within the observational uncertainties. I discuss the implications of
this result for the interpretation of high-redshift galaxy observations. A
catalog of dwarf-galaxy--QSO projections culled from the Sloan Digital Sky
Survey is provided to stimulate future work.
|
0807.2853v1
|
2008-07-23
|
Damped driven coupled oscillators: entanglement, decoherence and the classical limit
|
The interaction of (two-level) Rydberg atoms with dissipative QED cavity
fields can be described classically or quantum mechanically, even for very low
temperatures and mean number of photons, provided the damping constant is large
enough. We investigate the quantum-classical border, the entanglement and
decoherence of an analytically solvable model, analog to the atom-cavity
system, in which the atom (field) is represented by a (driven and damped)
harmonic oscillator. The maximum value of entanglement is shown to depend on
the initial state and the dissipation-rate to coupling-constant ratio. While in
the original model the atomic entropy never grows appreciably (for large
dissipation rates), in our model it reaches a maximum before decreasing.
Although both models predict small values of entanglement and dissipation, for
fixed times of the order of the inverse of the coupling constant and large
dissipation rates, these quantities decrease faster, as a function of the ratio
of the dissipation rate to the coupling constant, in our model.
|
0807.3715v1
|
2008-07-26
|
A Monte Carlo Method for Modeling Thermal Damping: Beyond the Brownian-Motion Master Equation
|
The "standard" Brownian motion master equation, used to describe thermal
damping, is not completely positive, and does not admit a Monte Carlo method,
important in numerical simulations. To eliminate both these problems one must
add a term that generates additional position diffusion. He we show that one
can obtain a completely positive simple quantum Brownian motion, efficiently
solvable, without any extra diffusion. This is achieved by using a stochastic
Schroedinger equation (SSE), closely analogous to Langevin's equation, that has
no equivalent Markovian master equation. Considering a specific example, we
show that this SSE is sensitive to nonlinearities in situations in which the
master equation is not, and may therefore be a better model of damping for
nonlinear systems.
|
0807.4211v3
|
2008-07-31
|
Finite-dimensional attractors for the quasi-linear strongly-damped wave equation
|
We present a new method of investigating the so-called quasi-linear strongly
damped wave equations $$ \partial_t^2u-\gamma\partial_t\Delta_x u-\Delta_x
u+f(u)= \nabla_x\cdot \phi'(\nabla_x u)+g $$ in bounded 3D domains. This method
allows us to establish the existence and uniqueness of energy solutions in the
case where the growth exponent of the non-linearity $\phi$ is less than 6 and
$f$ may have arbitrary polynomial growth rate. Moreover, the existence of a
finite-dimensional global and exponential attractors for the solution semigroup
associated with that equation and their additional regularity are also
established. In a particular case $\phi\equiv0$ which corresponds to the
so-called semi-linear strongly damped wave equation, our result allows to
remove the long-standing growth restriction $|f(u)|\leq C(1+ |u|^5)$.
|
0807.5078v1
|
2008-08-01
|
Field-Driven Domain-Wall Dynamics in GaMnAs Films with Perpendicular Anisotropy
|
We combine magneto-optical imaging and a magnetic field pulse technique to
study domain wall dynamics in a ferromagnetic (Ga,Mn)As layer with
perpendicular easy axis. Contrary to ultrathin metallic layers, the depinning
field is found to be smaller than the Walker field, thereby allowing for the
observation of the steady and precessional flow regimes. The domain wall width
and damping parameters are determined self-consistently. The damping, 30 times
larger than the one deduced from ferromagnetic resonance, is shown to
essentially originate from the non-conservation of the magnetization modulus.
An unpredicted damping resonance and a dissipation regime associated with the
existence of horizontal Bloch lines are also revealed.
|
0808.0119v1
|
2008-08-11
|
Effect of frequency and temperature on microwave-induced magnetoresistance oscillations in two-dimensional electron systems
|
Experimental results on microwave-induced magnetoresistance oscillation in
two-dimensional electron systems show a similar behavior of these systems
regarding temperature and microwave frequency. It is found that these
oscillations tend to quench when frequency or temperature increase, approaching
magnetoresistance to the response of the dark system. In this work we show that
this experimental behavior can be addressed on the same theoretical basis.
Microwave radiation forces the electron orbits to move back and forth being
damped by interaction with the lattice. We show that this damping depends
dramatically on microwave frequency and also on temperature. An increase in
frequency or temperature gives rise to an increase in the lattice damping
producing eventually a quenching effect in the magnetoresistance oscillations.
|
0808.1489v1
|
2008-11-13
|
Higher order energy decay rates for damped wave equations with variable coefficients
|
Under appropriate assumptions the energy of wave equations with damping and
variable coefficients $c(x)u_{tt}-\hbox{div}(b(x)\nabla u)+a(x)u_t =h(x)$ has
been shown to decay. Determining the rate of decay for the higher order
energies involving the $k$th order spatial and time derivatives has been an
open problem with the exception of some sparse results obtained for $k=1,2,3$.
We establish estimates that optimally relate the higher order energies with the
first order energy by carefully analyzing the effects of linear damping. The
results concern weighted (in time) and also pointwise (in time) energy decay
estimates. We also obtain $L^\infty$ estimates for the solution $u$. As an
application we compute explicit decay rates for all energies which involve the
dimension $n$ and the bounds for the coefficients $a(x)$ and $b(x)$ in the case
$c (x)=1$ and $h(x)=0.$
|
0811.2159v1
|
2009-01-12
|
Nonlinear Wigner solid transport over superfluid helium under AC conditions
|
Nonlinear transport properties of the two-dimensional Wigner solid of surface
electrons on superfluid helium are studied for alternating current conditions.
For time-averaged quantities like Fourier coefficients, the field-velocity
characteristics are shown to be qualitatively different as compared to that
found in the DC theory. For a spatially uniform current we found a general
solution for the field-velocity relationship which appears to be strongly
dependent on the current frequency. If the current frequency is much lower than
the ripplon damping parameter, the Bragg-Cherenkov resonances which appear at
high enough drift velocities acquire a distinctive saw-tooth shape with long
right-side tails independent of small damping. For current frequencies which
are close or higher than the ripplon damping coefficient, the interference of
ripplons excited at different time intervals results in a new oscillatory (in
drift velocity) regime of Bragg-Cherenkov scattering.
|
0901.1508v1
|
2009-01-14
|
Brownian motion with respect to time-changing Riemannian metrics, applications to Ricci flow
|
We generalize Brownian motion on a Riemannian manifold to the case of a
family of metrics which depends on time. Such questions are natural for
equations like the heat equation with respect to time dependent Laplacians
(inhomogeneous diffusions). In this paper we are in particular interested in
the Ricci flow which provides an intrinsic family of time dependent metrics. We
give a notion of parallel transport along this Brownian motion, and establish a
generalization of the Dohrn-Guerra or damped parallel transport, Bismut
integration by part formulas, and gradient estimate formulas. One of our main
results is a characterization of the Ricci flow in terms of the damped parallel
transport. At the end of the paper we give an intrinsic definition of the
damped parallel transport in terms of stochastic flows, and derive an intrinsic
martingale which may provide information about singularities of the flow.
|
0901.1999v2
|
2009-01-15
|
The sound damping constant for generalized theories of gravity
|
The near-horizon metric for a black brane in Anti-de Sitter (AdS) space and
the metric near the AdS boundary both exhibit hydrodynamic behavior. We
demonstrate the equivalence of this pair of hydrodynamic systems for the sound
mode of a conformal theory. This is first established for Einstein's gravity,
but we then show how the sound damping constant will be modified, from its
Einstein form, for a generalized theory. The modified damping constant is
expressible as the ratio of a pair of gravitational couplings that are
indicative of the sound-channel class of gravitons. This ratio of couplings
differs from both that of the shear diffusion coefficient and the shear
viscosity to entropy ratio. Our analysis is mostly limited to conformal
theories but suggestions are made as to how this restriction might eventually
be lifted.
|
0901.2191v1
|
2009-01-26
|
Damping of sound waves in superfluid nucleon-hyperon matter of neutron stars
|
We consider sound waves in superfluid nucleon-hyperon matter of massive
neutron-star cores. We calculate and analyze the speeds of sound modes and
their damping times due to the shear viscosity and non-equilibrium weak
processes of particle transformations. For that, we employ the dissipative
relativistic hydrodynamics of a superfluid nucleon-hyperon mixture, formulated
recently [M.E. Gusakov and E.M. Kantor, Phys. Rev. D78, 083006 (2008)]. We
demonstrate that the damping times of sound modes calculated using this
hydrodynamics and the ordinary (nonsuperfluid) one, can differ from each other
by several orders of magnitude.
|
0901.4108v1
|
2009-03-02
|
Attenuation and damping of electromagnetic fields: Influence of inertia and displacement current
|
New results for attenuation and damping of electromagnetic fields in rigid
conducting media are derived under the conjugate influence of inertia due to
charge carriers and displacement current. Inertial effects are described by a
relaxation time for the current density in the realm of an extended Ohm's law.
The classical notions of poor and good conductors are rediscussed on the basis
of an effective electric conductivity, depending on both wave frequency and
relaxation time. It is found that the attenuation for good conductors at high
frequencies depends solely on the relaxation time. This means that the
penetration depth saturates to a minimum value at sufficiently high
frequencies. It is also shown that the actions of inertia and displacement
current on damping of magnetic fields are opposite to each other. That could
explain why the classical decay time of magnetic fields scales approximately as
the diffusion time. At very small length scales, the decay time could be given
either by the relaxation time or by a fraction of the diffusion time, depending
whether inertia or displacement current, respectively, would prevail on
magnetic diffusion.
|
0903.0210v1
|
2009-04-06
|
Scrutinizing single-qubit quantum channels: Theory and experiment with trapped ions
|
We report experimental implementation of various types of qubit channels
using an individual trapped ion. We analyzed experimental data and we performed
tomographic reconstruction of quantum channels based on these data.
Specifically, we studied phase damping channels, where the damping acts either
in the xy-plane of the Bloch sphere or in an arbitrary plane that includes the
origin of the Bloch sphere. We also experimentally realized and consequently
analyzed quantum channels that in addition to phase damping affect also a
polarization rotation. We used three reconstruction schemes for estimation of
quantum channels from experimental data: (1) a linear inverse method, (2) a
maximum likelihood estimation, and (3) a constrained maximum likelihood
estimation. We took into account realistic experimental conditions where
imperfect test-state preparations and biased measurements are incorporated into
the estimation schemes. As a result we found that imperfections present in the
process of preparation of test states and as well as in measurements of the
considered ion trap system do not limit the control of the implementation of
the desired channel. Even imperfect preparation of test state and subsequent
measurements still provide sufficient resources for the complete
quantum-channel tomography.
|
0904.0923v1
|
2009-05-13
|
Time-dependent barrier passage of Two-dimensional non-Ohmic damping system
|
The time-dependent barrier passage of an anomalous damping system is studied
via the generalized Langevin equation (GLE) with non-Ohmic memory damping
friction tensor and corresponding thermal colored noise tensor describing a
particle passing over the saddle point of a two-dimensional quadratic potential
energy surface. The time-dependent passing probability and transmission
coefficient are analytically obtained by using of the reactive flux method. The
long memory aspect of friction is revealed to originate a non-monotonic
$\delta$(power exponent of the friction) dependence of the passing probability,
the optimal incident angle of the particle and the steady anomalous
transmission coefficient. In the long time limit a bigger steady transmission
coefficient is obtained which means less barrier recrossing than the
one-dimensional case.
|
0905.2074v1
|
2009-06-04
|
Viscous cavity damping of a microlever in a simple fluid
|
We consider the problem of oscillation damping in air of a thermally actuated
microlever as it is gradually approached towards an infinite wall in parallel
geometry. As the gap is decreased from 20 nm down to 400 nm, we observe the
increasing damping of the lever Brownian motion in the fluid laminar regime.
This manifests itself as a linear decrease with distance of the lever quality
factor accompanied by a dramatic softening of its resonance, and eventually
leads to the freezing of the CL oscillation. We are able to quantitatively
explain this behavior by analytically solving the Navier-Stokes equation with
perfect slip boundary conditions. Our findings may have implications for
microfluidics and micro- nano-electromechanical applications.
|
0906.0782v1
|
2009-06-19
|
Wakefield damping for the CLIC crab cavity
|
A crab cavity is required in the CLIC to allow effective head-on collision of
bunches at the IP. A high operating frequency is preferred as the deflection
voltage required for a given rotation angle and the RF phase tolerance for a
crab cavity are inversely proportional to the operating frequency. The short
bunch spacing of the CLIC scheme and the high sensitivity of the crab cavity to
dipole kicks demand very high damping of the inter-bunch wakes, the major
contributor to the luminosity loss of colliding bunches. This paper
investigates the nature of the wakefields in the CLIC crab cavity and the
possibility of using various damping schemes to suppress them effectively.
|
0906.3593v1
|
2009-07-06
|
Non-Fermi liquid behavior due to U(1) gauge field in two dimensions
|
We study the damping rate of massless Dirac fermions due to the U(1) gauge
field in (2+1)-dimensional quantum electrodynamics. In the absence of a Maxwell
term for the gauge field, the fermion damping rate
$\mathrm{Im}\Sigma(\omega,T)$ is found to diverge in both perturbative and
self-consistent results. In the presence of a Maxwell term, there is still
divergence in the perturbative results for $\mathrm{Im}\Sigma(\omega,T)$. Once
the Maxwell term is included into the self-consistent equations for fermion
self-energy and vacuum polarization functions, the fermion damping rate is free
of divergence and exhibits non-Fermi liquid behavior:
$\mathrm{Im}\Sigma(\omega,T) \propto \mathrm{max}(\sqrt{\omega},\sqrt{T})$.
|
0907.1022v3
|
2009-07-30
|
Gas damping force noise on a macroscopic test body in an infinite gas reservoir
|
We present a simple analysis of the force noise associated with the
mechanical damping of the motion of a test body surrounded by a large volume of
rarefied gas. The calculation is performed considering the momentum imparted by
inelastic collisions against the sides of a cubic test mass, and for other
geometries for which the force noise could be an experimental limitation. In
addition to arriving at an accurated estimate, by two alternative methods, we
discuss the limits of the applicability of this analysis to realistic
experimental configurations in which a test body is surrounded by residual gas
inside an enclosure that is only slightly larger than the test body itself.
|
0907.5375v2
|
2009-08-19
|
Nonlinear viscoelastic wave propagation: an extension of Nearly Constant Attenuation (NCQ) models
|
Hysteretic damping is often modeled by means of linear viscoelastic
approaches such as "nearly constant Attenuation (NCQ)" models. These models do
not take into account nonlinear effects either on the stiffness or on the
damping, which are well known features of soil dynamic behavior. The aim of
this paper is to propose a mechanical model involving nonlinear viscoelastic
behavior for isotropic materials. This model simultaneously takes into account
nonlinear elasticity and nonlinear damping. On the one hand, the shear modulus
is a function of the excitation level; on the other, the description of
viscosity is based on a generalized Maxwell body involving non-linearity. This
formulation is implemented into a 1D finite element approach for a dry soil.
The validation of the model shows its ability to retrieve low amplitude ground
motion response. For larger excitation levels, the analysis of seismic wave
propagation in a nonlinear soil layer over an elastic bedrock leads to results
which are physically satisfactory (lower amplitudes, larger time delays, higher
frequency content).
|
0908.2715v2
|
2009-08-26
|
Influence of an external magnetic field on forced turbulence in a swirling flow of liquid metal
|
We report an experimental investigation on the influence of an external
magnetic field on forced 3D turbulence of liquid gallium in a closed vessel. We
observe an exponential damping of the turbulent velocity fluctuations as a
function of the interaction parameter N (ratio of Lorentz force over inertial
terms of the Navier-Stokes equation). The flow structures develop some
anisotropy but do not become bidimensional. From a dynamical viewpoint, the
damping first occurs homogeneously over the whole spectrum of frequencies. For
larger values of N, a very strong additional damping occurs at the highest
frequencies. However, the injected mechanical power remains independent of the
applied magnetic field. The simultaneous measurement of induced magnetic field
and electrical potential differences shows a very weak correlation between
magnetic field and velocity fluctuations. The observed reduction of the
fluctuations is in agreement with a previously proposed mechanism for the
saturation of turbulent dynamos and with the order of magnitude of the Von
Karman Sodium dynamo magnetic field.
|
0908.3821v1
|
2009-09-30
|
Electronic damping of molecular motion at metal surfaces
|
A method for the calculation of the damping rate due to electron-hole pair
excitation for atomic and molecular motion at metal surfaces is presented. The
theoretical basis is provided by Time Dependent Density Functional Theory
(TDDFT) in the quasi-static limit and calculations are performed within a
standard plane-wave, pseudopotential framework. The artificial periodicity
introduced by using a super-cell geometry is removed to derive results for the
motion of an isolated atom or molecule, rather than for the coherent motion of
an ordered over-layer. The algorithm is implemented in parallel, distributed
across both ${\bf k}$ and ${\bf g}$ space, and in a form compatible with the
CASTEP code. Test results for the damping of the motion of hydrogen atoms above
the Cu(111) surface are presented.
|
0909.5495v1
|
2009-10-14
|
Constraint on the growth factor of the cosmic structure from the damping of the baryon acoustic oscillation signature
|
We determine a constraint on the growth factor by measuring the damping of
the baryon acoustic oscillations in the matter power spectrum using the Sloan
Digital Sky Survey luminous red galaxy sample. The damping of the BAO is
detected at the one sigma level. We obtain \sigma_8D_1(z=0.3) =
0.42^{+0.34}_{-0.28} at the 1\sigma statistical level, where \sigma_8 is the
root mean square overdensity in a sphere of radius 8h^{-1}Mpc and D_1(z) is the
growth factor at redshift z. The above result assumes that other parameters are
fixed and the cosmology is taken to be a spatially flat cold dark matter
universe with the cosmological constant.
|
0910.2513v1
|
2009-10-27
|
On the Interpretation of Magnetic Helicity Signatures in the Dissipation Range of Solar Wind Turbulence
|
Measurements of small-scale turbulent fluctuations in the solar wind find a
non-zero right-handed magnetic helicity. This has been interpreted as evidence
for ion cyclotron damping. However, theoretical and empirical evidence suggests
that the majority of the energy in solar wind turbulence resides in low
frequency anisotropic kinetic Alfven wave fluctuations that are not subject to
ion cyclotron damping. We demonstrate that a dissipation range comprised of
kinetic Alfven waves also produces a net right-handed fluctuating magnetic
helicity signature consistent with observations. Thus, the observed magnetic
helicity signature does not necessarily imply that ion cyclotron damping is
energetically important in the solar wind.
|
0910.5023v1
|
2009-12-08
|
Coupling Photosphere and Corona: Linear and Turbulent Regimes
|
In a recent work Grappin et al. [1] have shown that low- frequency movements
can be transmitted from one footpoint to the other along a magnetic loop, thus
mimicking a friction effect of the corona on the photosphere, and invalidating
the line-tying approximation. We consider here successively the effect of high
frequencies and turbulent damping on the process. We use a very simple
atmospheric model which allows to study analytically the laminar case, and to
study the turbulent case both using simple phenomenological arguments and a
more sophisticated turbulence model [2]. We find that, except when turbulent
damping is such that all turbulence is damped during loop traversal, coupling
still occurs between distant footpoints, and moreover the coronal field induced
by photospheric movements saturates at finite values.
|
0912.1497v1
|
2009-12-16
|
The role of $r$-mode damping in the thermal evolution of neutron stars
|
The thermal evolution of neutron stars (NSs) is investigated by coupling with
the evolution of $\textit{r}$-mode instability that is described by a second
order model.The heating effect due to shear viscous damping of the
$\textit{r}$-modes enables us to understand the high temperature of two young
pulsars (i.e., PSR B0531+21 and RX J0822-4300) in the framework of the simple
$npe$ NS model, without superfluidity or exotic particles.Moreover, the light
curves predicted by the model within an acceptable parameter regime may
probably cover all of the young and middle-aged pulsars in the $\lg
T_s^{\infty}-\lg t$ panel, and an artificially strong $p$ superfluidity invoked
in some early works is not needed here. Additionally, by considering the
radiative viscous damping of the $\textit{r}$-modes, a surprising extra cooling
effect is found, which can even exceed the heating effect sometimes although
plays an ignorable role in the thermal history.
|
0912.3052v1
|
2009-12-25
|
Noisy non-transitive quantum games
|
We study the effect of quantum noise in 3 by 3 entangled quantum games. By
considering different noisy quantum channels we analyze that how a two-player,
three-strategy Rock-Scissor-Paper game is influenced by the quantum noise. We
consider the winning non-transitive strategies R, S and P such as R beats S, S
beats P, and P beats R. The game behaves as a noiseless game for maximum value
of the quantum noise parameter. It is seen that Alice's payoff is heavily
influenced by the depolarizing noise as compared to the amplitude damping
noise. Depolarizing channel causes a monotonic decrease in players payoffs as
we increase the amount of of quantum noise. In case of amplitude damping
channel, the Alice's payoff function reaches its minimum for alpha=0.5 and is
symmetrical. This means that larger values of quantum noise influence the game
weakly. On the other hand, phase damping channel does not influence the game's
payoff. Furthermore, the game's Nash equilibrium and non-transitive character
of the game are not affected under the influence of quantum noise.
|
0912.4961v1
|
2010-01-26
|
Damping in high-frequency metallic nanomechanical resonators
|
We have studied damping in polycrystalline Al nanomechanical resonators by
measuring the temperature dependence of their resonance frequency and quality
factor over a temperature range of 0.1 - 4 K. Two regimes are clearly
distinguished with a crossover temperature of 1 K. Below 1 K we observe a
logarithmic temperature dependence of the frequency and linear dependence of
damping that cannot be explained by the existing standard models. We attribute
these phenomena to the effect of the two-level systems characterized by the
unexpectedly long (at least two orders of magnitude longer) relaxation times
and discuss possible microscopic models for such systems. We conclude that the
dynamics of the two-level systems is dominated by their interaction with
one-dimensional phonon modes of the resonators.
|
1001.4612v1
|
2010-04-28
|
Inviscid dynamical structures near Couette flow
|
Consider inviscid fluids in a channel {-1<y<1}. For the Couette flow
v_0=(y,0), the vertical velocity of solutions to the linearized Euler equation
at v_0 decays in time. At the nonlinear level, such inviscid damping has not
been proved. First, we show that in any (vorticity) H^{s}(s<(3/2)) neighborhood
of Couette flow, there exist non-parallel steady flows with arbitrary minimal
horizontal period. This implies that nonlinear inviscid damping is not true in
any (vorticity) H^{s}(s<(3/2)) neighborhood of Couette flow and for any
horizontal period. Indeed, the long time behavior in such neighborhoods are
very rich, including nontrivial steady flows, stable and unstable manifolds of
nearby unstable shears. Second, in the (vorticity) H^{s}(s>(3/2)) neighborhood
of Couette, we show that there exist no non-parallel steadily travelling flows
v(x-ct,y), and no unstable shears. This suggests that the long time dynamics in
H^{s}(s>(3/2)) neighborhoods of Couette might be much simpler. Such contrasting
dynamics in H^{s} spaces with the critical power s=(3/2) is a truly nonlinear
phenomena, since the linear inviscid damping near Couette is true for any
initial vorticity in L^2.
|
1004.5149v1
|
2010-06-14
|
Parallel electric field amplification by phase-mixing of Alfven waves
|
Previous numerical studies have identified "phase mixing" of low-frequency
Alfven waves as a mean of parallel electric field amplification and
acceleration of electrons in a collisionless plasma. Theoretical explanations
are given of how this produces an amplification of the parallel electric field,
and as a consequence, also leads to enhanced collisionless damping of the wave
by energy transfer to the electrons. Our results are based on the properties of
the Alfven waves in a warm plasma which are obtained from drift-kinetic theory,
in particular, the rate of their electron Landau damping. Phase mixing in a
collisionless low-$\beta$ plasma proceeds in a manner very similar to the
visco-resistive case, except for the fact that electron Landau damping is the
primary energy dissipation channel. The time and length scales involved are
evaluated. We also focus on the evolution of the parallel electric field and
calculate its maximum value in the course of its amplification.
|
1006.2729v1
|
2010-07-19
|
Anomalously large damping of long-wavelength quasiparticles caused by long-range interaction
|
We demonstrate that long-range interaction in a system can lead to a very
strong interaction between long-wavelength quasiparticles and make them heavily
damped. In particular, we discuss magnon spectrum using 1/S expansion in 3D
Heisenberg ferromagnet (FM) with arbitrary small dipolar forces at T<<T_C. We
obtain that a fraction of long-wavelength magnons with energies e_k<T has
anomalously large damping G_k (ratio G_k/e_k reaches 0.3 for certain k). This
effect is observed both in quantum and classical FMs. Remarkably, this result
contradicts expectation of the quasiparticle concept according which a weakly
excited state of a many-body system can be represented as a collection of
weakly interacting elementary excitations. Particular materials are pointed out
which are suitable for corresponding experiments.
|
1007.3081v2
|
2010-07-29
|
The Quasinormal Mode Spectrum of a Kerr Black Hole in the Eikonal Limit
|
It is well established that the response of a black hole to a generic
perturbation is characterized by a spectrum of damped resonances, called
quasinormal modes; and that, in the limit of large angular momentum ($l \gg
1$), the quasinormal mode frequency spectrum is related to the properties of
unstable null orbits. In this paper we develop an expansion method to explore
the link. We obtain new closed-form approximations for the lightly-damped part
of the spectrum in the large-$l$ regime. We confirm that, at leading order in
$l$, the resonance frequency is linked to the orbital frequency, and the
resonance damping to the Lyapunov exponent, of the relevant null orbit. We go
somewhat further than previous studies to establish (i) a spin-dependent
correction to the frequency at order $1 / l$ for equatorial ($m = \pm l$)
modes, and (ii) a new result for polar modes ($m = 0$). We validate the
approach by testing the closed-form approximations against frequencies obtained
numerically with Leaver's method.
|
1007.5097v1
|
2010-08-30
|
Caldeira-Leggett Model, Landau Damping, and the Vlasov-Poisson System
|
The Caldeira-Leggett Hamiltonian (Eq. (1) below) describes the interaction of
a discrete harmonic oscillator with a continuous bath of harmonic oscillators.
This system is a standard model of dissipation in macroscopic low temperature
physics, and has applications to superconductors, quantum computing, and
macroscopic quantum tunneling. The similarities between the Caldeira-Leggett
model and the linearized Vlasov-Poisson equation are analyzed, and it is shown
that the damping in the Caldeira-Leggett model is analogous to that of Landau
damping in plasmas [1]. An invertible linear transformation [2, 3] is presented
that converts solutions of the Caldeira-Leggett model into solutions of the
linearized Vlasov-Poisson system.
|
1008.5190v1
|
2010-09-09
|
A number-conserving linear response study of low-velocity ion stopping in a collisional magnetized classical plasma
|
The results of a theoretical investigation on the low-velocity stopping power
of the ions moving in a magnetized collisional plasma are presented. The
stopping power for an ion is calculated employing linear response theory using
the dielectric function approach. The collisions, which leads to a damping of
the excitations in the plasma, is taken into account through a
number-conserving relaxation time approximation in the linear response
function. In order to highlight the effects of collisions and magnetic field we
present a comparison of our analytical and numerical results obtained for a
nonzero damping or magnetic field with those for a vanishing damping or
magnetic field. It is shown that the collisions remove the anomalous friction
obtained previously [Nersisyan et al., Phys. Rev. E 61, 7022 (2000)] for the
collisionless magnetized plasmas at low ion velocities. One of major objectives
of this study is to compare and contrast our theoretical results with those
obtained through a novel diffusion formulation based on Dufty-Berkovsky
relation evaluated in magnetized one-component plasma models framed on target
ions and electrons.
|
1009.1700v1
|
2010-10-03
|
A High Phase Advance Damped and Detuned Structure for the Main Linacs of Clic
|
The main accelerating structures for the CLIC are designed to operate at an
average accelerating gradient of 100 MV/m. The accelerating frequency has been
optimised to 11.994 GHz with a phase advance of 2{\pi}/3 of the main
accelerating mode. The moderately damped and detuned structure (DDS) design is
being studied as an alternative to the strongly damped WDS design. Both these
designs are based on the nominal accelerating phase advance. Here we explore
high phase advance (HPA) structures in which the group velocity of the rf
fields is reduced compared to that of standard (2{\pi}/3) structures. The
electrical breakdown strongly depends on the fundamental mode group velocity.
Hence it is expected that electrical breakdown is less likely to occur in the
HPA structures. We report on a study of both the fundamental and dipole modes
in a CLIC_DDS_HPA structure, designed to operate at 5{\pi}/6 phase advance per
cell. Higher order dipole modes in both the standard and HPA structures are
also studied.
|
1010.0438v1
|
2010-10-23
|
Environmental influences on Quantum Monty Hall problem
|
We reformulate the quantum Monty Hall problem in the presence of decoherence.
The decoherence destroys the fairness of the game. A new Nash equilibrium for a
particular strategy profile in the presence of decoherence emerges. It is shown
that in the presence of decoherence under the action of amplitude damping
channel, Bob's winning probability is always higher than three-forth,
irrespective of Alice's strategy, if he does not switch to the other door and
always wins for a fully decohered case of the channel. Depolarizing channel
damps up Bob's winning probability and gets better off if he sticks to his
current selection. Phase damping channel leaves the winning probability
unaffected. Unlike the classical and the quantum forms of the game, Bob's
dominant strategy in the presence of decoherence is not switching.
|
1010.4875v2
|
2010-12-14
|
Controlling transfer of quantum correlations among bi-partitions of a composite quantum system by combining noisy environments
|
The correlation dynamics is investigated for various bi-partitions of a
composite system consisting of two qubits, and two independent and
non-identical noisy environments. The two qubits have no direct interaction
with each other and locally interact with their environments. Classical and
quantum correlations including entanglement are initially prepared only between
the two qubits. We find that, contrary to the identical noisy environment case,
the entanglement and quantum correlation transfer directions can be controlled
by combining different noisy environments. The amplitude damping environment
determines whether there exists entanglement transfer among the bi-partitions
of a composite system. When one qubit is coupled to an amplitude damping
environment but another one to a bit-flip one, we find a very interesting
result that all the quantum and classical correlations, and even the
entanglement, originally existing between the qubits, can be completely
transferred without any loss to the qubit coupled to the bit-flip environment
and the amplitude-damping environment. We also notice that it is possible to
distinguish the quantum correlation from the classical correlation and
entanglement by combining different noisy environments.
|
1012.3033v1
|
2010-12-22
|
Viscous damping of r-modes: Small amplitude instability
|
We study the viscous damping of r-modes of compact stars and analyze in
detail the regions where small amplitude modes are unstable to the emission of
gravitational radiation. We present general expressions for the viscous damping
times for arbitrary forms of interacting dense matter and derive general
semi-analytic results for the boundary of the instability region. These results
show that many aspects, like in particular the physically important minima of
the instability boundary, are surprisingly insensitive to detailed microscopic
properties of the considered form of matter. Our general expressions are
applied to the cases of hadronic stars, strange stars, and hybrid stars, and we
focus on equations of state that are compatible with the recent measurement of
a heavy compact star. We find that hybrid stars with a sufficiently small core
can "masquerade" as neutron stars and feature an instability region that is
indistinguishable from that of a neutron star, whereas neutron stars with a
core density high enough to allow direct Urca reactions feature a notch on the
right side of the instability region.
|
1012.4883v2
|
2010-12-27
|
Phenomenology of Current-Induced Dynamics in Antiferromagnets
|
We derive a phenomenological theory of current-induced staggered
magnetization dynamics in antiferromagnets. The theory captures the reactive
and dissipative current-induced torques and the conventional effects of
magnetic fields and damping. A Walker ansatz describes the dc current-induced
domain-wall motion when there is no dissipation. If magnetic damping and
dissipative torques are included, the Walker ansatz remains robust when the
domain-wall moves slowly. As in ferromagnets, the domain-wall velocity is
proportional to the ratio between the dissipative-torque and the magnetization
damping. In addition, a current-driven antiferromagnetic domain-wall acquires a
net magnetic moment.
|
1012.5655v2
|
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