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2016-05-27
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Scalar field quasinormal frequencies of Reissner-Nordström black hole surrounded by quintessence by using he continued fraction method
|
We evaluate the quasinormal modes of massless scalar field around
Reissner-Nordstr$\ddot{\text{o}}$m black hole surrounded by a static and
spherically symmetric quintessence by using the continued fraction method. The
appropriate Frobenius series for three special cases of the quintessence
parameter $ \epsilon = -1/3, -2/3$ and $-1$ are derived successfully. We show
that the variation of quasinormal frequencies with charge of the black hole and
the quintessential parameters. The numerical results show that quintessence
field decreases oscillation frequencies of all angular momentum $l$ modes and
increases the damping time of $l>0$ modes.
|
1606.00703v3
|
2016-06-06
|
Weak invariants of time-dependent quantum dissipative systems
|
The concept of weak invariant is introduced. Then, the weak invariants
associated with time-dependent quantum dissipative systems are discussed in the
context of master equations of the Lindblad type. In particular, with the help
of the su(1,1) Lie-algebraic structure, the weak invariant is explicitly
constructed for the quantum damped harmonic oscillator with the time-dependent
frequency and friction coefficient. This generalizes the Lewis-Riesenfeld
invariant to the case of nonunitary dynamics in the Markovian approximation.
|
1606.01767v4
|
2016-06-09
|
Stabilization of second order nonlinear equations with variable delay
|
For a wide class of second order nonlinear non-autonomous models, we
illustrate that combining proportional state control with the feedback that is
proportional to the derivative of the chaotic signal, allows to stabilize
unstable motions of the system. The delays are variable, which leads to more
flexible controls permitting delay perturbations; only delay bounds are
significant for stabilization by a delayed control. The results are applied to
the sunflower equation which has an infinite number of equilibrium points.
|
1606.03045v1
|
2016-06-09
|
Infrared behavior of dipolar Bose systems at low temperatures
|
We rigorously discuss the infrared behavior of the uniform three dimensional
dipolar Bose systems. In particular, it is shown that low-temperature physics
of the system is controlled by two parameters, namely isothermal
compressibility and intensity of the dipole-dipole interaction. By using
hydrodynamic approach we calculate the spectrum and damping of low-lying
excitations and analyze infrared behavior of the one-particle Green's function.
The low-temperature corrections to the anisotropic superfluid density as well
as condensate depletion are found. Additionally we derive equations of the
two-fluid hydrodynamics for dipolar Bose systems and calculate velocities of
first and second sound.
|
1606.03047v2
|
2016-06-30
|
Skyrmion dynamics in a chiral magnet driven by periodically varying spin currents
|
In this work, we investigated the spin dynamics in a slab of chiral magnets
induced by an alternating (ac) spin current. Periodic trajectories of the
skyrmion in real space are discovered under the ac current as a result of the
Magnus and viscous forces, which originate from the Gilbert damping, the spin
transfer torque, and the $ \beta $-nonadiabatic torque effects. The results are
obtained by numerically solving the Landau-Lifshitz-Gilbert equation and can be
explained by the Thiele equation characterizing the skyrmion core motion.
|
1606.09326v2
|
2016-07-07
|
Two-well atomic Bose-Hubbard analogues of optical cavities
|
We propose and analyse analogs of optical cavities for atoms using two-well
Bose-Hubbard models with pumping and losses. With one well pumped, we find that
both the mean-field dynamics and the quantum statistics show a quantitative
dependence on the choice of damped well. Both the systems we analyse remain far
from equilibrium, preserving good coherence between the wells in the
steady-state. We find a small degree of quadrature squeezing and mode
entanglement for some parameter regimes. Due to recent experimental advances,
it should be possible to demonstrate the effects we investigate and predict.
|
1607.01911v1
|
2016-07-10
|
Gravitational Waves in Effective Quantum Gravity
|
In this short paper we investigate quantum gravitational effects on
Einstein's equations using effective field theory techniques. We consider the
leading order quantum gravitational correction to the wave equation. Besides
the usual massless mode, we find a pair of modes with complex masses. These
massive particles have a width and could thus lead to a damping of
gravitational waves if excited in violent astrophysical processes producing
gravitational waves such as e.g. black hole mergers. We discuss the
consequences for gravitational wave events such as GW 150914 recently observed
by the Advanced LIGO collaboration.
|
1607.02773v1
|
2016-07-11
|
A bifurcation analysis for the Lugiato-Lefever equation
|
The Lugiato-Lefever equation is a cubic nonlinear Schr\"odinger equation,
including damping, detuning and driving, which arises as a model in nonlinear
optics. We study the existence of stationary waves which are found as solutions
of a four-dimensional reversible dynamical system in which the evolutionary
variable is the space variable. Relying upon tools from bifurcation theory and
normal forms theory, we discuss the codimension 1 bifurcations. We prove the
existence of various types of steady solutions, including spatially localized,
periodic, or quasi-periodic solutions.
|
1607.02862v1
|
2016-08-08
|
An analytic technique for the solutions of nonlinear oscillators with damping using the Abel Equation
|
Using the Chiellini condition for integrability we derive explicit solutions
for a generalized system of Riccati equations $\ddot{x}+\alpha
x^{2n+1}\dot{x}+x^{4n+3}=0$ by reduction to the first-order Abel equation
assuming the parameter $\alpha\ge 2\sqrt{2(n+1)}$. The technique, which was
proposed by Harko \textit{et al}, involves use of an auxiliary system of
first-order differential equations sharing a common solution with the Abel
equation. In the process analytical proofs of some of the conjectures made
earlier on the basis of numerical investigations in \cite{SJKB} is provided.
|
1608.02324v1
|
2016-08-11
|
Phenomenological plasmon broadening and relation to the dispersion
|
Pragmatic ways of including lifetime broadening of collective modes in the
electron liquid are critically compared. Special focus lies on the impact of
the damping parameter onto the dispersion. It is quantitatively exemplified for
the two-dimensional case, for both, the charge (`sheet'-)plasmon and the
spin-density plasmon. The predicted deviations fall within the resolution
limits of advanced techniques.
|
1608.03432v1
|
2016-08-16
|
Quasistatic contact problem with unilateral constraint for elastic-viscoplastic materials
|
This paper consists of two parts. In the first part we prove the unique
solvability for the abstract variational-hemivariational inequality with
history-dependent operator. The proof is based on the existing result for the
static variational-hemivariational inequality and a fixed point argument. In
the second part, we consider a mathematical model which describes quasistatic
frictional contact between a deformable body and a rigid foundation. In the
model the material behaviour is modelled by an elastic-viscoplastic
constitutive law. The contact is described with a normal damped response,
unilateral constraint and memory term. In the analysis of this model we use the
abstract result from the first part of the paper.
|
1608.04660v1
|
2016-08-27
|
Plasma dynamics of a laser filamentation-guided spark
|
We investigate experimentally the plasma dynamics of a centimeter-scale,
laser filamentation-guided spark discharge. Using electrical and optical
diagnostics to study monopolar discharges with varying current pulses we show
that plasma decay is dominated by free electron recombination if the current
decay time is shorter than the recombination characteristic time. In the
opposite case, the plasma electron density closely follows the current
evolution. We demonstrate that this criterion holds true in the case of damped
AC sparks, and that alternative current is the best option to achieve a long
plasma lifetime for a given peak current.
|
1608.07677v1
|
2016-09-01
|
A mathematical consideration of vortex thinning in 2D turbulence
|
In two dimensional turbulence, vortex thinning process is one of the
attractive mechanism to explain inverse energy cascade in terms of vortex
dynamics. By direct numerical simulation to the two-dimensional Navier-Stokes
equations with small-scale forcing and large-scale damping, Xiao-Wan-Chen-Eyink
(2009) found an evidence that inverse energy cascade may proceed with the
vortex thinning mechanism. The aim of this paper is to analyze the
vortex-thinning mechanism mathematically (using the incompressible Euler
equations), and give a mathematical evidence that large-scale vorticity gains
energy from small-scale vorticity due to the vortex-thinning process.
|
1609.00107v1
|
2016-09-22
|
Primordial density and BAO reconstruction
|
We present a new method to reconstruct the primordial (linear) density field
using the estimated nonlinear displacement field. The divergence of the
displacement field gives the reconstructed density field. We solve the
nonlinear displacement field in the 1D cosmology and show the reconstruction
results. The new reconstruction algorithm recovers a lot of linear modes and
reduces the nonlinear damping scale significantly. The successful 1D
reconstruction results imply the new algorithm should also be a promising
technique in the 3D case.
|
1609.07041v1
|
2016-09-26
|
Transverse Magneto-Optical Kerr Effect in Active Magneto-Plasmonic Structures
|
We propose a novel method to enhance the transverse magneto-optical Kerr
effect (TMOKE) in the magneto-plasmonic (MP) nanostructures by means of the
active dielectric layer. We report the theoretical analysis of the
magnetoplasmonic structure with a ferromagnetic dielectric doped with
rear-earth ions (Nd3+) as the example of a gain layer. The enhancement takes
place near the surface plasmon polariton (SPP) resonances of the
nanostructures. The stimulated emission of the dopants in the field of SPP wave
partially compensates its losses. It is shown that due to a decrease of SPP
damping a Q-factor of the MP resonance increases and the TMOKE is increased in
comparison with the passive nanostructure.
|
1609.07883v1
|
2016-09-30
|
Stochastic pure state representation for open quantum systems
|
We show that the usual master equation formalism of Markovian open quantum
systems is completely equivalent to a certain state vector formalism. The state
vector of the system satisfies a given frictional Schr\"odinger equation except
for random instant transitions of discrete nature. Hasse's frictional
Hamiltonian is recovered for the damped harmonic oscillator.
|
1609.09636v1
|
2016-10-27
|
Direct-dynamical entanglement-discord relations
|
In this article, by considering Bell-diagonal two-qubit initial states
submitted to local dynamics generated by the phase damping, bit flip, phase
flip, bit-phase flip, and depolarizing channels, we report some elegant
direct-dynamical relations between geometric measures of entanglement and
discord. The complex scenario appearing already in this simplified case study
indicates that similarly simple relation shall hardly be found in more general
situations.
|
1610.09030v2
|
2016-10-31
|
Pseudo steady-state non-Gaussian EPR-steering of massive particles in pumped and damped Bose-Hubbard dimers
|
We propose and analyse a pumped Bose-Hubbard dimer as a source of
continuous-variable Einstein-Podolsky-Rosen (EPR) steering with non-Gaussian
statistics. We use the truncated Wigner representation to calculate third and
fourth order cumulants, finding clear signals of non-Gaussianity. We also
calculate the products of inferred quadrature variances which indicate that
states demonstrating the EPR paradox are present. Our proposed experimental
configuration is extrapolated from current experimental techniques and adds
another possibility to the current toolbox of quantum atom optics.
|
1610.09820v1
|
2016-11-04
|
Quantum correlations and entanglement in a model comprised of a short chain of nonlinear oscillators
|
We discuss a model comprised of a chain of three Kerr-like nonlinear
oscillators pumped by two modes of external coherent field. We show that the
system can be treated as nonlinear quantum scissors and behave as a three-qubit
model. For such situation, different types of tripartite entangled states can
be generated, even when damping effects are present in the system. Some amount
of such entanglement can survive even in a long-time limit. The flow of
bipartite entanglement between subsystems of the model and relations among
first-order correlations, second-order correlations, and the entanglement are
discussed.
|
1611.01334v1
|
2016-11-10
|
Unifying Suspension and Granular flows near Jamming
|
Rheological properties of dense flows of hard particles are singular as one
approaches the jamming threshold where flow ceases, both for granular flows
dominated by inertia, and for over-damped suspensions. Concomitantly, the
lengthscale characterizing velocity correlations appears to diverge at jamming.
Here we review a theoretical framework that gives a scaling description of
stationary flows of frictionless particles. Our analysis applies both to
suspensions and inertial flows of hard particles. We report numerical results
in support of the theory, and show the phase diagram that results when friction
is added, delineating the regime of validity of the frictionless theory.
|
1611.03243v1
|
2016-11-23
|
Interchange instability and transport in matter-antimatter plasmas
|
Symmetric electron-positron plasmas in inhomogeneous magnetic fields are
intrinsically subject to interchange instability and transport. Scaling
relations for the propagation velocity of density blob perturbations relevant
to transport in isothermal magnetically confined electron-positron plasmas are
deduced, including damping effects when Debye lengths are large compared to
Larmor radii. The relations are verified by nonlinear full-F gyrofluid
computations. Results are in favour of sufficient magnetic confinement for
planned electron-positron plasma experiments. The model is generalised to other
matter-antimatter plasmas. Magnetised electron-positron-proton-antiproton
plasmas are susceptible to interchange driven local matter-antimatter
separation, which can be expected to impede (so far unrealised) sustained
laboratory magnetic confinement.
|
1611.07836v1
|
2016-12-01
|
Superfluidity in Bose-Hubbard circuits
|
A semiclassical theory is provided for the metastability regime-diagram of
atomtronic superfluid circuits. Such circuits typically exhibit
high-dimensional chaos; and non-linear resonances that couple the Bogoliubov
excitations manifest themselves. Contrary to the expectation these resonances
do not originate from the familiar Beliaev and Landau damping terms. Rather,
they are described by a variant of the Cherry Hamiltonian of celestial
mechanics. Consequently we study the induced decay process, and its dependence
on the number of sites and of condensed particles.
|
1612.00251v2
|
2016-12-03
|
The formation of long-lived high-correlated states of light and polarization in high-quality semiconductor microcavity at the resonant laser excitation
|
The correlation function of radiation from a high-quality semiconductor
microcavity at the resonant laser excitation demonstrates oscillations with
surprisingly long-period and damping times of a nanosecond range. It was shown
that the oscillations are not attributed to weak Rabi interaction between
long-lived exciton states and intracavity electromagnetic field. The study of a
response with high spectral resolution had revealed that the oscillations arise
if a spectral position as well as a period of longitudinal laser modes is
similar to modulation components of a microcavity transmission spectrum.
|
1612.00954v1
|
2016-12-05
|
Perturbative dissipation dynamics of a weakly driven Jaynes-Cummings system
|
We generalize a microscopic master equation method to study the dissipation
dynamics of Jaynes-Cummings two-level system with a weak external driving.
Using perturbative analysis to extend the damping bases theory, we derive the
corrected Rabi oscillation and vaccum Rabi splitting analytically. The
evolution of the decoherence factor of the weakly driven system reveals that
the off-diagonal density matrix elements are oscillating at a frequency
dependent on the driving strength and the initial population inversion. For
highly-inverted systems at the weak-driving limit, this frequency reduces to
twice the value for the non-driven system, showing the dissipation dynamics
unable to be discovered using more conventional approaches.
|
1612.01248v1
|
2016-12-06
|
On renormalised solution for thermomechanical problem in perfect - plasticity
|
We consider the quasi-static evolution of the thermo-plasticity model in
which the evolution equation law for the inelastic strain is given by the
Prandtl-Reuss flow rule. The thermal part of the Cauchy stress tensor is not
linearised in the neighbourhood of a references temperature. This nonlinear
thermal part imposed to add a damping term to the balance of the momentum,
which can be interpreted as external forces acting on the material. In general
the dissipation term occurring in the heat equation is integrable function only
and the standard methods can not be applied. Combining truncation techniques
and Boccardo-Gallou\"et approach with monotone methods we prove an existence of
renormalised solutions.
|
1612.01886v1
|
2016-12-16
|
Relaxation mechanism driven by spin angular momentum absorption throughout antiferromagnetic phase transition in NiFe surface oxides
|
We report an alternative mechanism for the physical origin of the
temperature-dependent ferromagnetic relaxation of Permalloy (NiFe) thin films.
Through spin-pumping experiments, we demonstrate that the peak in the
temperature-dependence of NiFe damping can be understood in terms of enhanced
spin angular momentum absorption at the magnetic phase transition in
antiferromagnetic surface-oxidized layers. These results suggest new avenues
for the investigation of an incompletely-understood phenomenon in physics.
|
1612.05556v1
|
2016-12-16
|
On the rotationally driven pevatron in the centre of the Milky Way
|
Based on the collective linear and nonlinear processes in a magnetized plasma
surrounding the black hole at the galactic center (GC), an acceleration
mechanism is proposed to explain the recent detection/discovery of PeV protons.
In a two stage process, the gravitation energy is first converted to the
electrical energy in fast growing Langmuir waves, and then the electrical
energy is transformed to the particle kinetic energy through Landau damping of
waves. It is shown that, for the characteristics parameters of GC plasma,
proton energy can be boosted upto 5PeV.
|
1612.05591v1
|
2016-12-26
|
Microscopic derivation of the hydrodynamics of active-Brownian-particle suspensions
|
We derive the hydrodynamic equations of motion for a fluid of active
particles described by under- damped Langevin equations that reduce to the
Active-Brownian-Particle model, in the overdamped limit. The contraction into
the hydrodynamic description is performed by locally averaging the par- ticle
dynamics with the non-equilibrium many-particle probability density, whose
formal expression is found in the physically relevant limit of high-friction
through a multiple-time-scale analysis. This approach permits to identify the
conditions under which self-propulsion can be subsumed into the fluid stress
tensor and thus to define systematically and unambiguously the local pressure
of the active fluid.
|
1612.08404v1
|
2016-12-29
|
Anomalous temperature-dependent heat transport in one-dimensional momentum-conserving systems with soft-type interparticle interaction
|
We here numerically investigate the heat transport behavior in a
one-dimensional lattice with a soft-type (ST) anharmonic interparticle
interaction. It is found that with the increase of system's temperature, while
the introduction of ST anharmonicity softens phonons and decreases their
velocities, this type of nonlinearity like its counterpart of hard type (HT),
can still not be able to fully damp the longest wave phonons. Therefore, an
anomalous temperature dependent heat transport with certain scaling properties
similarly to those in the Fermi-Pasta-Ulam like systems with HT interactions
can be seen. Our detailed examination from simulations well verify this
temperature dependent behavior.
|
1612.09080v2
|
2017-01-01
|
Analysis of a remarkable singularity in a nonlinear DDE
|
In this work we investigate the dynamics of the nonlinear DDE
(delay-differential equation)
x''(t)+x(t-T)+x(t)^3=0
where T is the delay. For T=0 this system is conservative and exhibits no
limit cycles. For T>0, no matter how small, an infinite number of limit cycles
exist, their amplitudes going to infinity in the limit as T approaches zero.
We investigate this situation in three ways: 1) Harmonic Balance, 2)
Melnikov's integral, and 3) Adding damping to regularize the singularity.
|
1701.00201v1
|
2017-01-12
|
Molecular Plasmonics: strong coupling at the low molecular density limit
|
We study the strong coupling between the molecular excited state and the
plasmonic modes of silver hole arrays with a resonant frequency very close to
the asymptotic line of the plasmonic dispersion relation, at the nonlinear
regime. We demonstrate that the strong coupling regime can be achieved between
the two sub-systems at low molecular densities with negligible damping of the
electromagnetic field. Our results are supported by rigorous numerical
simulations showing that the strong coupling is observed when the molecular
transition lies within the nonlinear regime of the dispersion relation rather
than the linear regime.
|
1701.03402v2
|
2017-01-22
|
Super quantum discord for general two qubit X states
|
The exact solutions of the super quantum discord are derived for general two
qubit X states in terms of a one-variable function. Several exact solutions of
the super quantum discord are given for the general X-state over nontrivial
regions of a seven dimensional manifold. It is shown that the super quantum
discord of the X state may increase or decreases under the phase damping
channel.
|
1701.06177v2
|
2017-01-26
|
Navier-Stokes-Voigt equations with memory in 3D lacking instantaneous kinematic viscosity
|
We consider a Navier-Stokes-Voigt fluid model where the instantaneous
kinematic viscosity has been completely replaced by a memory term incorporating
hereditary effects, in presence of Ekman damping. The dissipative character of
our model is weaker than the one where hereditary and instantaneous viscosity
coexist, previously studied by Gal and Tachim-Medjo. Nevertheless, we prove the
existence of a regular exponential attractor of finite fractal dimension under
rather sharp assumptions on the memory kernel.
|
1701.07845v1
|
2017-01-28
|
Quantum discord protection of a two-qutrit V-type atomic system from decoherence by partially collapsing measurements
|
In this paper, by exploiting the weak measurement and quantum measurement re-
versal (WMQMR) procedure, we propose a scheme to show how one can protect the
geometric quantum discord (GQD) of a two-qutrit V-type atomic system each of
which interacts with a dissipative reservoir independently. We examine the
scheme for the GQD of the initial two-qutrit Werner and Horodecki states for
different classes of weak mea- surement strengthes. It is found out that the
presented protocol enables us to suppress decoherence due to the amplitude
damping (AD) channel and preserve the quantum dis- cord of the two-qutrit
system successfully.
|
1701.08278v2
|
2017-02-03
|
Global existence and decay rate of strong solution to incompressible Oldroyd type model equations
|
This paper investigates the global existence and the decay rate in time of a
solution to the Cauchy problem for an incompressible Oldroyd model with a
deformation tensor damping term. There are three major results. The first is
the global existence of the solution for small initial data. Second, we derive
the sharp time decay of the solution in $L^{2}-$norm. Finally, the sharp time
decay of the solution of higher order Sobolev norms is obtained.
|
1702.00902v2
|
2017-02-05
|
Hydrodynamic fluctuations near a critical endpoint and Hanbury Brown-Twiss interferometry
|
The field of high energy nuclear collisions has witnessed a surge of interest
in the role played by hydrodynamic fluctuations. Hydrodynamic fluctuations may
have significant effects on matter created in heavy-ion accelerators whose
trajectories in the plane of temperature versus chemical potential pass near a
possible critical endpoint. We extend previous studies to explore the impact of
these fluctuations on Hanbury Brown-Twiss interferometry of identical hadrons.
With an appropriately defined correlation function we find that the
fluctuations increase substantially when the trajectory passes near a critical
endpoint, and also displays a damped oscillatory behavior in the rapidity
distance $\Delta y$ unlike that originating from initial-state fluctuations.
|
1702.01368v1
|
2017-02-20
|
The HTL resumed propagators in the light cone gauge
|
The expression of the HTL resumed gluon propagator in the light cone gauge is
derived. In the real time mechanism, using the Mandelstam Leibbrant
prescription of $(n\cdot K)^{-1}$, we calculate the transverse and longitudinal
parts of the gluon HTL self-energy and prove the transverse and longitudinal
parts do not have divergence. We also calculate the quark self energy in the
HTL approximation, and find it gauge independent. We analytically calculate the
damping rates of the hard quark and gluon with this HTL resumed gluon
propagator.
|
1702.05890v2
|
2017-02-27
|
Magnetization reversal by superconducting current in $\varphi_0$ Josephson junctions
|
We study magnetization reversal in a $\varphi_0$ Josephson junction with
direct coupling between magnetic moment and Josephson current. Our simulations
of magnetic moment dynamics show that by applying an electric current pulse, we
can realize the full magnetization reversal. We propose different protocols of
full magnetization reversal based on the variation of the Josephson junction
and pulse parameters, particularly, electric current pulse amplitude, damping
of magnetization and spin-orbit interaction. We discuss experiments which can
probe the magnetization reversal in $\varphi_0$-junctions.
|
1702.08394v4
|
2017-03-02
|
Integrable RCS as a proposed replacement for Fermilab Booster
|
Integrable optics is an innovation in particle accelerator design that
potentially enables a greater betatron tune spread and damps collective
instabilities. An integrable rapid-cycling synchrotron (RCS) would be an
effective replacement for the Fermilab Booster, as part of a plan to reach
multi-MW beam power at 120 GeV for the Fermilab high-energy neutrino program.
We provide an example integrable lattice with features of a modern RCS -
dispersion-free drifts, low momentum compaction factor, superperiodicity,
chromaticity correction, bounded beta functions, and separate-function magnets.
|
1703.00952v1
|
2017-03-03
|
Spin-orbit effective fields in Pt/GdFeCo bilayers
|
In the increasing interests on spin-orbit torque (SOT) with various magnetic
materials, we investigated SOT in rare earth-transition metal ferrimagnetic
alloys. The harmonic Hall measurements were performed in Pt/GdFeCo bilayers to
quantify the effective fields resulting from the SOT. It is found that the
damping-like torque rapidly increases near the magnetization compensation
temperature TM of the GdFeCo, which is attributed to the reduction of the net
magnetic moment.
|
1703.00995v1
|
2017-03-06
|
Antibunching in an optomechanical oscillator
|
We theoretically analyze antibunching of the phonon field in an
optomechanical oscillator employ- ing the membrane-in-the-middle geometry. More
specifically, a single-mode mechanical oscillator is quadratically coupled to a
single-mode cavity field in the regime in which the cavity dissipation is a
dominant source of damping, and adiabatic elimination of the cavity field leads
to an effective cubic nonlinearity for the mechanics. We show analytically in
the weak coupling regime that the mechan- ics displays a chaotic phonon field
for small optomechanical cooperativity, whereas an antibunched single-phonon
field appears for large optomechanical cooperativity. This opens the door to
control of the second-order correlation function of a mechanical oscillator in
the weak coupling regime.
|
1703.01706v1
|
2017-03-07
|
Dark matter kinetic decoupling with a light particle
|
We argue that the acoustic damping of the matter power spectrum is not a
generic feature of the kinetic decoupling of dark matter, but even the
enhancement can be realized depending on the nature of the kinetic decoupling
when compared to that in the standard cold dark matter model. We consider a
model that exhibits a ${\it sudden}$ kinetic decoupling and investigate
cosmological perturbations in the ${\it standard}$ cosmological background
numerically in the model. We also give an analytic discussion in a simplified
setup. Our results indicate that the nature of the kinetic decoupling could
have a great impact on small scale density perturbations.
|
1703.02338v1
|
2017-03-22
|
A review on Asteroseismology
|
Over the last decade, thanks to the successful space missions launched to
detect stellar pulsations, Asteroseismology has produced an extraordinary
revolution in astrophysics, unveiling a wealth of results on structural
properties of stars over a large part of the H-R diagram. Particularly
impressive has been the development of Asteroseismology for stars showing
solar-like oscillations, which are excited and intrinsically damped in stars
with convective envelopes. Here I will review on the modern era of
Asteroseismology with emphasis on results obtained for solar-like stars and
discuss its potential for the advancement of stellar physics.
|
1703.07604v2
|
2017-03-30
|
Behavior of the impurity atom in a weakly-interacting Bose gas
|
We studied the properties of a single impurity atom immersed in a dilute Bose
condensate at low temperatures. In particular, we perturbatively obtained the
momentum dependence of the impurity spectrum and damping. By means of the
Brillouin-Wigner perturbation theory we also calculated the self-energy both
for attractive and repulsive polaron in the long-wavelength limit. The
stability problem of the impurity atom in a weakly-interacting Bose gas is also
examined.
|
1703.10390v1
|
2017-03-31
|
A Fourier-Chebyshev Spectral Method for Cavitation Computation in Nonlinear Elasticity
|
A Fourier-Chebyshev spectral method is proposed in this paper for solving the
cavitation problem in nonlinear elasticity. The interpolation error for the
cavitation solution is analyzed, the elastic energy error estimate for the
discrete cavitation solution is obtained, and the convergence of the method is
proved. An algorithm combined a gradient type method with a damped quasi-Newton
method is applied to solve the discretized nonlinear equilibrium equations.
Numerical experiments show that the Fourier-Chebyshev spectral method is
efficient and capable of producing accurate numerical cavitation solutions.
|
1703.10939v1
|
2017-07-13
|
Clock frequency estimation under spontaneous emission
|
We investigate the quantum dynamics of a driven two-level system under
spontaneous emission and its application in clock frequency estimation. By
using a Lindblad equation to describe the system, we analytically obtain its
exact solutions, which show three different regimes: Rabi oscillation, damped
oscillation and overdamped decay. From the analytical solutions, we explore how
the spontaneous emission affects the clock frequency estimation. We find that,
under a modest spontaneous emission rate, the transition frequency can still be
inferred from the Rabi oscillation. Our results provide potential practical
applications in frequency measurement and quantum control under decoherence.
|
1707.03958v1
|
2017-07-20
|
Fluid structure system with boundary conditions involving the pressure
|
We study a coupled fluid-structure system involving boundary conditions on
the pressure. The fluid is described by the incompressible Navier--Stokes
equations in a 2D rectangular type domain where the upper part of the domain is
described by a damped Euler--Bernoulli beam equation. Existence and uniqueness
of local strong solutions without assumptions of smallness on the initial data
is proved.
|
1707.06382v2
|
2017-07-25
|
The Effect of Electron Lens as Landau Damping Device on Single Particle Dynamics in HL-LHC
|
An electron lens can serve as an effective mechanism for suppressing coherent
instabilities in high intensity storage rings through nonlinear amplitude
dependent betatron tune shift. However, the addition of a strong localized
nonlinear focusing element to the accelerator lattice may lead to undesired
effects in particle dynamics. We evaluate the effect of a Gaussian electron
lens on single particle motion in HL-LHC using numerical tracking simulations,
and compare the results to the case when an equal tune spread is generated by
conventional octupole magnets.
|
1707.08239v1
|
2017-08-11
|
Gradient expansion formalism for generic spin torques
|
We propose a new quantum-mechanical formalism to calculate spin torques based
on the gradient expansion, which naturally involves spacetime gradients of the
magnetization and electromagnetic fields. We have no assumption in the
small-amplitude formalism or no difficulty in the SU($2$) gauge transformation
formalism. As a representative, we calculate the spin renormalization, Gilbert
damping, spin-transfer torque, and $\beta$-term in a three-dimensional
ferromagnetic metal with nonmagnetic and magnetic impurities being taken into
account within the self-consistent Born approximation. Our results serve as a
first-principles formalism for spin torques.
|
1708.03424v1
|
2017-08-21
|
Fundamental models in nonlinear acoustics part I. Analytical comparison
|
This work is concerned with the study of fundamental models from nonlinear
acoustics. In Part~I, a hierarchy of nonlinear damped wave equations arising in
the description of sound propagation in thermoviscous fluids is deduced. In
particular, a rigorous justification of two classical models, the Kuznetsov and
Westervelt equations, retained as limiting systems for consistent initial data,
is given. Numerical comparisons that confirm and complement the theoretical
results are provided in Part~II.
|
1708.06099v1
|
2017-09-07
|
Short Wavelength Geodesic Acoustic Mode Excitation by Energetic Particles
|
Taking the collisionless damping of geodesic acoustic mode (GAM) as an
example, the physics processes underlying wave particle resonances in the short
wavelength limit are clarified. As illus- trative application, GAM excitation
by energetic particles in short wavelength limit is investigated assuming a
single pitch angle slowing-down fast ion equilibrium distribution function.
Conditions for this energetic particle-induced GAM (EGAM) to be unstable are
discussed.
|
1709.02085v1
|
2017-09-12
|
Convex approximations of quantum channels
|
We address the problem of optimally approximating the action of a desired and
unavailable quantum channel $\Phi $ having at our disposal a single use of a
given set of other channels $\{\Psi_i \}$. The problem is recast to look for
the least distinguishable channel from $\Phi $ among the convex set $\sum_i p_i
\Psi_i$, and the corresponding optimal weights $\{ p_i \}$ provide the optimal
convex mixing of the available channels $\{\Psi_i \}$. For single-qubit
channels we study specifically the cases where the available convex set
corresponds to covariant channels or to Pauli channels, and the desired target
map is an arbitrary unitary transformation or a generalized damping channel.
|
1709.03805v1
|
2017-09-18
|
Explicit Backbone Curves from Spectral Submanifolds of Forced-Damped Nonlinear Mechanical Systems
|
Spectral submanifolds (SSMs) have recently been shown to provide exact and
unique reduced-order models for nonlinear unforced mechanical vibrations. Here
we extend these results to periodically or quasiperiodically forced mechanical
systems, obtaining analytic expressions for forced responses and backbone
curves on modal (i.e. two-dimensional) time dependent SSMs. A judicious choice
of the parameterization of these SSMs allows us to simplify the reduced
dynamics considerably. We demonstrate our analytical formulae on three
numerical examples and compare them to results obtained from available normal
form methods.
|
1709.05947v3
|
2017-09-25
|
Orbital-Free Density-Functional Theory Simulations of Displacement Cascade in Aluminum
|
Here, we report orbital-free density-functional theory (OF DFT) molecular
dynamics simulations of the displacement cascade in aluminum. The electronic
effect is our main concern. The displacement threshold energies are calculated
using OF DFT and classical molecular dynamics (MD) and the comparison reveals
the role of charge bridge. Compared to MD simulation, the displacement spike
from OF DFT has a lower peak and shorter duration time, which is attributed to
the effect of electronic damping. The charge density profiles clearly display
the existence of depleted zones, vacancy and interstitial clusters. And it is
found that the energy exchanges between ions and electrons are mainly
contributed by the kinetic energies.
|
1709.08288v1
|
2017-09-27
|
Damped Casimir radiation and photon correlation measurements
|
An effective toy model for an ideal one-dimensional nonstationary cavity is
taken to be the starting point to derive a fitting markovian master equation
for the corresponding leaky cavity. In the regime where the generation of
photons via the dynamical Casimir effect is bounded, the master equation thus
constructed allows us to investigate the effects of decoherence on the average
number of Casimir photons and their quantum fluctuations through the
second-order correlation function.
|
1709.09685v1
|
2017-10-06
|
Markovian master equation for nonlinear systems
|
Within the f-deformed oscillator formalism, we derive a Markovian master
equation for the description of the damped dynamics of nonlinear systems that
interact with their environment. The applicability of this treatment to the
particular case of a Morse-like oscillator interacting with a thermal field is
illustrated, and the decay of quantum coherence in such a system is analyzed in
terms of the evolution on phase space of its nonlinear coherent states via the
Wigner function.
|
1710.02251v1
|
2017-10-07
|
On the De Gregorio modification of the Constantin-Lax-Majda Model
|
We study a modification due to De Gregorio of the Constantin-Lax-Majda (CLM)
model $\omega_t = \omega H\omega$ on the unit circle. The De Gregorio equation
is $\omega_t+u \omega_x-u_x\omega =0, u_x = H\omega.$ In contrast with the CLM
model, numerical simulations suggest that the solutions of the De Gregorio
model with smooth initial data exist globally for all time, and generically
converge to equilibria when $t\to\pm\infty$, in a way resembling inviscid
damping. We prove that such a behavior takes place near a manifold of
equilibria.
|
1710.02737v1
|
2017-10-12
|
A Locking-free DP-Q2-P1 MFEM for Incompressible Nonlinear Elasticity Problems
|
A mixed finite element method (MFEM), using dual-parametric piecewise
bi-quadratic and affine (DP-Q2-P1) finite element approximations for the
deformation and the pressure like Lagrange multiplier respectively, is
developed and analyzed for the numerical computation of incompressible
nonlinear elasticity problems with large deformation gradient, and a damped
Newton method is applied to solve the resulted discrete problem. The method is
proved to be locking free and stable. The accuracy and efficiency of the method
are illustrated by numerical experiments on some typical cavitation problems.
|
1710.04445v2
|
2017-10-23
|
An infinite dimensional Duffing-like evolution equation with linear dissipation and an asymptotically small source term
|
We consider an abstract nonlinear second order evolution equation, inspired
by some models for damped oscillations of a beam subject to external loads or
magnetic fields, and shaken by a transversal force. When there is no external
force, the system has three stationary positions, two stable and one unstable,
and all solutions are asymptotic for $t$ large to one of these stationary
solutions.We show that this pattern extends to the case where the external
force is bounded and small enough, in the sense that solutions can exhibit only
three different asymptotic behaviors.
|
1710.08159v1
|
2017-10-26
|
The effects of retardation on the topological plasmonic chain: plasmonic edge states beyond the quasistatic limit
|
We study a one-dimensional plasmonic system with non-trivial topology: a
chain of metallic nanoparticles with alternating spacing, which is the
plasmonic analogue to the Su-Schreiffer-Heeger model. We extend previous
efforts by including long range hopping with retardation and radiative damping,
which leads to a non-Hermitian Hamiltonian with frequency dependence. We
calculate band structures numerically and show that topological features such
as quantised Zak phase persist due to chiral symmetry. This predicts parameters
leading to topologically protected edge modes, which allows for positioning of
disorder-robust hotspots at topological interfaces, opening up novel
nanophotonics applications.
|
1710.09782v1
|
2017-10-30
|
Is a doubly quantized vortex dynamically unstable in uniform superfluids?
|
We revisit the fundamental problem of the splitting instability of a doubly
quantized vortex in uniform single-component superfluids at zero temperature.
We analyze the system-size dependence of the excitation frequency of a doubly
quantized vortex through large-scale simulations of the Bogoliubov--de Gennes
equation, and find that the system remains dynamically unstable even in the
infinite-system-size limit. Perturbation and semi-classical theories reveal
that the splitting instability radiates a damped oscillatory phonon as an
opposite counterpart of a quasi-normal mode.
|
1710.10810v2
|
2017-10-30
|
Breathers as Metastable States for the Discrete NLS equation
|
We study metastable motions in weakly damped Hamiltonian systems. These are
believed to inhibit the transport of energy through Hamiltonian, or nearly
Hamiltonian, systems with many degrees of freedom. We investigate this question
in a very simple model in which the breather solutions that are thought to be
responsible for the metastable states can be computed perturbatively to an
arbitrary order. Then, using a modulation hypothesis, we derive estimates for
the rate at which the system drifts along this manifold of periodic orbits and
verify the optimality of our estimates numerically.
|
1710.10999v2
|
2017-11-01
|
Optical two-photon nonlinear waves in two-dimensional materials
|
A theory of an optical two-photon breather in a graphene monolayer (or
graphene-like two-dimensional material) is constructed. The system of the
material equations for two-photon transitions and the wave equation for
transverse magnetic polarized modes of the surface plasmon polaritons are shown
to reduce to the nonlinear Schr\"odinger equation with damping. Explicit
analytical expressions for a surface small intensity two-photon breather
(0$\pi$ pulse) of self-induced transparency are obtained. It is shown that the
optical conductivity of graphene reduces the amplitude of the surface
two-photon nonlinear wave during the propagation. The one-photon and two-photon
breathers in graphene are compared and have obtained that the differences
between their parameters are significant.
|
1711.00343v1
|
2017-11-02
|
Polaron in the dilute critical Bose condensate
|
The properties of impurity immersed in the dilute $D$-dimensional Bose gas at
temperatures close to the second-order phase transition point are considered.
Particularly by means of the $1/N$-expansion we calculated the leading-order
polaron energy and the damping rate in the limit of vanishing boson-boson
interaction. It is show that the perturbative effective mass and the
quasiparticle residue diverge logarithmically in the long-length limit
signalling the non-analytic behavior of impurity spectrum and a non-pole
structure of a polaron Green's function in the infrared region, respectively.
|
1711.00712v2
|
2017-11-09
|
Stationary Distributions of Second Order Stochastic Evolution Equations with Memory in Hilbert Spaces
|
In this paper, we consider stationarity of a class of second-order stochastic
evolution equations with memory, driven by Wiener processes or Levy jump
processes, in Hilbert spaces. The strategy is to formulate by reduction some
first-order systems in connection with the stochastic equations under
investigation. We develop asymptotic behavior of dissipative second-order
equations and then apply them to time delay systems through
Gearhart-Pruss-Greiner's theorem. The stationary distribution of the system
under consideration is the projection on the first coordinate of the
corresponding stationary results of a lift-up stochastic system without delay
on some product Hilbert space. Last, an example of stochastic damped delay wave
equations with memory is presented to illustrate our theory.
|
1711.03448v1
|
2017-11-12
|
On the stabilization of a hyperbolic Stokes system under geometric control condition
|
In this paper, we study the stabilization problem for a hyperbolic type
Stokes system posed on a bounded domain. We show that when the damping effects
are restricted to a subdomain satisfying the geometrical control condition the
system decays exponentially. The result is a consequence of a new quasi-mode
estimate for the Stokes system.
|
1711.04301v2
|
2017-11-21
|
Electrostatic stability of electron-positron plasmas in dipole geometry
|
The electrostatic stability of electron-positron plasmas is investigated in
the point-dipole and Z-pinch limits of dipole geometry. The kinetic dispersion
relation for sub-bounce-frequency instabilities is derived and solved. For the
zero-Debye-length case, the stability diagram is found to exhibit singular
behavior. However, when the Debye length is non-zero, a fluid mode appears,
which resolves the observed singularity, and also demonstrates that both the
temperature and density gradients can drive instability. It is concluded that a
finite Debye length is necessary to determine the stability boundaries in
parameter space. Landau damping is investigated at scales sufficiently smaller
than the Debye length, where instability is absent.
|
1711.08021v1
|
2017-11-22
|
Fluctuations through a Vibrating Bounce
|
We study the evolution of cosmological perturbations in a non-singular
bouncing cosmology with a bounce phase which has superimposed oscillations of
the scale factor. We identify length scales for which the final spectrum of
fluctuations obtains imprints of the non-trivial bounce dynamics. These
imprints in the spectrum are manifested in the form of damped oscillation
features at scales smaller than a characteristic value and an increased
reddening of the spectrum at all the scales as the number of small bounces
increases.
|
1711.08370v1
|
2017-11-23
|
Speeding up Thermalisation via Open Quantum System Variational Optimisation
|
Optimizing open quantum system evolution is an important step on the way to
achieving quantum computing and quantum thermodynamic tasks. In this article,
we approach optimisation via variational principles and derive an open quantum
system variational algorithm explicitly for Lindblad evolution in Liouville
space. As an example of such control over open system evolution, we control the
thermalisation of a qubit attached to a thermal Lindbladian bath with a damping
rate $\gamma$. Since thermalisation is an asymptotic process and the
variational algorithm we consider is for fixed time, we present a way to
discuss the potential speedup of thermalisation that can be expected from such
variational algorithms.
|
1711.08776v1
|
2017-11-28
|
Pulsations in close binaries from the BRITE point of view
|
Using BRITE photometric data for several close binary systems we address the
problem of damping pulsations in close binary systems due to proximity effects.
Because of small number statistics, no firm conclusion is given, but we find
pulsations in three relatively close binaries. The pulsations in these binaries
have, however, very low amplitudes.
|
1711.10344v1
|
2017-12-12
|
Non-Gaussianity of multiple photon subtracted thermal states in terms of compound-Poisson photon number distribution parameters: theory and experiment
|
The multiphoton-subtracted thermal states are an interesting example of
quantum states of light which are both classical and non-Gaussian. All the
properties of such states can be described by just two parameters of
compound-Poisson photon number distribution. The non-Gaussianity dependency on
these parameters has been calculated numerically and analytically. The loss of
non-Gaussianity during the optical damping has been also studied
experimentally.
|
1712.04174v2
|
2017-12-15
|
Dynamically tunable metamaterial analogue of electromagnetically induced transparency with graphene in the terahertz regime
|
A novel mechanism to realize dynamically tunable electromagnetically induced
transparency (EIT) analogue in the terahertz (THz) regime is proposed. By
putting the electrically controllable monolayer graphene under the dark
resonator, the amplitude of the EIT resonance in the metal-based metamaterial
can be modulated substantially via altering the Fermi level of graphene. The
amplitude modulation can be attributed to the change in the damping rate of the
dark mode caused by the recombination effect of the conductive graphene. This
work provides an alternative way to achieve tunable slow light effect and has
potential applications in THz wireless communications.
|
1712.05525v1
|
2017-12-15
|
Frequency decay for Navier-Stokes stationary solutions
|
We consider stationary Navier-Stokes equations in R 3 with a regular external
force and we prove exponential frequency decay of the solutions. Moreover, if
the external force is small enough, we give a pointwise exponential frequency
decay for such solutions according to the K41 theory. If a damping term is
added to the equation, a pointwise decay is obtained without the smallness
condition over the force.
|
1712.05753v1
|
2017-12-16
|
Approximation of a damped Euler-Bernoulli beam model in the Loewner framework
|
The Loewner framework for model order reduction is applied to the class of
infinite-dimension systems. The transfer function of such systems is irrational
(as opposed to linear systems, whose transfer function is rational) and can be
expressed as an infinite series of rational functions. The main advantage of
the method is the fact that reduced orders models are constructed using only
input-output measurements. The procedure can be directly applied to the
original transfer function or to the one obtained from the finite element
discretization of the PDE. Significantly better results are obtained when using
it directly, as it is presented in the experiments section.
|
1712.06031v1
|
2017-12-18
|
Wave propagation through an elastically-asymmetric architected material
|
A one-dimensional wave propagation through elastically asymmetric media is
investigated. A class of metamaterials possessing an arbitrary elastic
asymmetry is proposed. This asymmetry results in different wave speeds of
tensile and compressive components of elastic waves. The faster component can
overtake the slower one resulting in their dissipative annihilation through
energy cascades. Efficient absorbing assemblies are presented and analysed
numerically. The length of the asymmetric part needed to damp a harmonic signal
is determined analytically and validated numerically. Transmission properties
for random self-affine wave-packets are studied: a universal scaling for the
transmission factor variation with the length of the asymmetric part was
established.
|
1712.06294v2
|
2017-12-19
|
Polaron in dilute 2D Bose gas at low temperatures
|
The properties of a Bose polaron immersed in a dilute two-dimensional medium
at finite temperatures are discussed. Assuming that the impurity is
weakly-coupled to the bath particles we have perturbatively calculated the
polaron energy, effective mass, quasiparticle residue and damping rate. The
parameters of impurity spectrum are found to be well-defined in the whole
temperature region whereas the pole structure of the impurity Green's function
is visible only at absolute zero. At any finite temperatures the quasiparticle
residue is logarithmically divergent signalling of the branch-cut behavior of
the polaron propagator.
|
1712.06978v1
|
2017-12-28
|
On well-posedness of Ericksen-Leslie's parabolic-hyperbolic liquid crystal model in compressible flow
|
We study the Ericksen-Leslie's parabolic-hyperbolic liquid crystal model in
compressible flow. Inspired by our study for incompressible case
\cite{Jiang-Luo-arXiv-2017} and some techniques from compressible Navier-Stokes
equations, we prove the local-in-time existence of the classical solution to
the system with finite initial energy, under some constraints on the Leslie
coefficients which ensure the basic energy law is dissipative. Furthermore,
with an additional assumption on the coefficients which provides a damping
effect, and the smallness of the initial energy, the global classical solution
can be established.
|
1712.09799v1
|
2017-12-29
|
A note on the nonlinear Schrödinger equation in a general domain
|
We consider the Cauchy problem for nonlinear Schr\"odinger equations in a
general domain $\Omega\subset\mathbb{R}^N$. Construction of solutions has been
only done by classical compactness method in previous results. Here, we
construct solutions by a simple alternative approach. More precisely, solutions
are constructed by proving that approximate solutions form a Cauchy sequence in
some Banach space. We discuss three different types of nonlinearities: power
type nonlinearities, logarithmic nonlinearities and damping nonlinearities.
|
1712.10239v2
|
2018-01-23
|
On degenerate circular and shear flows: the point vortex and power law circular flows
|
We consider the problem of asymptotic stability and linear inviscid damping
for perturbations of a point vortex and similar degenerate circular flows.
Here, key challenges include the lack of strict monotonicity and the necessity
of working in weighted Sobolev spaces whose weights degenerate as the radius
tends to zero or infinity. Prototypical examples are given by circular flows
with power law singularities or zeros as $r\downarrow 0$ or $r \uparrow
\infty$.
|
1801.07371v1
|
2018-01-25
|
Arbitrary-order functionally fitted energy-diminishing methods for gradient systems
|
It is well known that for gradient systems in Euclidean space or on a
Riemannian manifold, the energy decreases monotonically along solutions. In
this letter we derive and analyse functionally fitted energy-diminishing
methods to preserve this key property of gradient systems. It is proved that
the novel methods are unconditionally energy-diminishing and can achieve
damping for very stiff gradient systems. We also show that the methods can be
of arbitrarily high order and discuss their implementations. A numerical test
is reported to illustrate the efficiency of the new methods in comparison with
three existing numerical methods in the literature.
|
1801.08484v1
|
2018-01-27
|
Decay of Benjamin - Ono solitons under the influence of dissipation
|
The adiabatic decay of Benjamin - Ono algebraic solitons is studied when the
influence of various types of small dissipation and radiative losses due to
large scale Coriolis dispersion are taken into consideration. The physically
most important dissipations are studied, Rayleigh and Reynolds dissipation,
Landau damping, dissipation in a laminar boundary layer and Chezy friction on a
rough bottom. The decay laws for the soliton parameters, that is amplitude,
velocity and width, are found in analytical form and are compared with the
results of direct numerical modelling.
|
1801.09088v1
|
2018-01-28
|
Decay of Kadomtsev - Petviashvili lumps in dissipative media
|
The decay of Kadomtsev - Petviashvili lumps is considered for a few typical
dissipations - Rayleigh dissipation, Reynolds dissipation, Landau damping,
Chezy bottom friction, viscous dissipation in the laminar boundary layer, and
radiative losses caused by large-scale dispersion. It is shown that the
straight-line motion of lumps is unstable under the influence of dissipation.
The lump trajectories are calculated for two most typical models of dissipation
- the Rayleigh and Reynolds dissipations. A comparison of analytical results
obtained within the framework of asymptotic theory with the direct numerical
calculations of the Kadomtsev - Petviashvili equation is presented. Good
agreement between the theoretical and numerical results is obtained.
|
1801.09175v1
|
2018-03-03
|
Long time instability of the Couette flow in low Gevrey spaces
|
We prove the instability of the Couette flow if the disturbances is less
smooth than the Gevrey space of class 2. This shows that this is the critical
regularity for this problem since it was proved in [5] that stability and
inviscid damping hold for disturbances which are smoother than the Gevrey space
of class 2. A big novelty is that this critical space is due to an instability
mechanism which is completely nonlinear and is due to some energy cascade.
|
1803.01246v1
|
2018-03-11
|
Uniform and non-uniform thermal switching of magnetic particles
|
The pulse-noise approach to systems of classical spins weakly interacting
with the bath has been applied to study thermally-activated escape of magnetic
nanoparticles over the uniform and nonuniform energy barriers at intermediate
and low damping. The validity of approximating a single-domain particle by a
single spin is investigated. Barriers for a non-uniform escape of elongated
particles for the uniaxial model with transverse and longitudinal field have
been worked out. Pulse-noise computations have been done for finite magnetic
chains. The linear stability of the uniform barrier state has been
investigated. The crossover between uniform and nonuniform barrier states has
been studied with the help of the variational approach.
|
1803.03988v1
|
2018-03-19
|
Dynamics of a Magnetic Needle Magnetometer: Sensitivity to Landau-Lifshitz-Gilbert Damping
|
An analysis of a single-domain magnetic needle in the presence of an external
magnetic field ${\bf B}$ is carried out with the aim of achieving a high
precision magnetometer. We determine the uncertainty $\Delta B$ of such a
device due to Gilbert dissipation and the associated internal magnetic field
fluctuations that gives rise to diffusion of the magnetic needle axis direction
${\bf n}$ and the needle orbital angular momentum. The levitation of the
magnetic needle in a magnetic trap and its stability are also analyzed.
|
1803.10064v2
|
2018-03-31
|
Point-source dispersion of quasi-neutrally-buoyant inertial particles
|
We analyze the evolution of the distribution, both in the phase space and in
the physical space, of inertial particles released by a spatially-localized
(punctual) source and advected by an incompressible flow. The difference in
mass density between fluid and particles is assumed as small, and represents
the basic parameter for a regular perturbative expansion. By means of
analytical techniques such as Hermitianization, we derive a chain of equations
of the advection--diffusion--reaction type, easily solvable at least
numerically. Our procedure provides results also for finite particle inertia,
away from the over-damped limit of quasi-tracer dynamics.
|
1804.00186v1
|
2018-04-04
|
Dynamics of measurement induced nonlocality under decoherence
|
Measurement Induced Nonlocality (MIN) captures nonlocal effects of a quantum
state due to local von Neumann projective measurements, is a bonafide measure
of quantum correlation between constituents of a composite system. In this
paper, we study the dynamical behavior of entanglement (measured by
concurrence), Hilber-Schmidt MIN and fidelity based MIN (FMIN) under local
noisy channels such as hybrid (consists of bit, phase, bit and phase flip),
generalized amplitude damping (GAD) and depolarizing channels for the initial
Bell diagonal state. We observed that while sudden death of entanglement occur
in hybrid and GAD channels, MIN and FMIN are more robust against such noise.
Finally, we demonstrate the revival of MIN and FMIN after a dark point of time
against depolarizing noise.
|
1804.01248v1
|
2018-04-04
|
Integer partition manifolds and phonon damping in one dimension
|
We develop a quantum model based on the correspondence between energy
distribution between harmonic oscillators and the partition of an integer
number. A proper choice of the interaction Hamiltonian acting within this
manifold of states allows us to examine both the quantum typicality and the
non-exponential relaxation in the same system. A quantitative agreement between
the field-theoretical calculations and the exact diagonalization of the
Hamiltonian is demonstrated.
|
1804.01374v1
|
2018-04-16
|
Searching for light from a dark matter clump
|
The DAMPE experiment has recently reported an electron spectrum that can be
explained by dark matter annihilation into charged lepton pairs in a nearby
dark matter clump. The accompanying bremsstrahlung may yield a gamma-ray excess
with a known spectral shape that extends over an angular scale of
$O(10^\circ)$. We show that such an excess is not present in Fermi-LAT data.
|
1804.05792v2
|
2018-04-18
|
Further results on the asymptotic behavior of a 2D overhead crane with input delays: Exponential convergence
|
This article is concerned with the asymptotic behavior of a 2D overhead
crane. Taking into account the presence of a delay in the boundary, and
assuming that no displacement term appears in the system, a distributed
(interior) damping feedback law is proposed in order to compensate the effect
of the delay. Then, invoking the frequency domain method, the solutions of the
closed-loop system are proved to converge exponentially to a stationary
position. This improves the recent result obtained by
Al-Musallam-Ammari-Chentouf, where the rate of convergence is at most of
polynomial type.
|
1804.06765v1
|
2018-04-24
|
An Invariant-region-preserving (IRP) Limiter to DG Methods for Compressible Euler Equations
|
We introduce an explicit invariant-region-preserving limiter applied to DG
methods for compressible Euler equations. The invariant region considered
consists of positivity of density and pressure and a maximum principle of a
specific entropy. The modified polynomial by the limiter preserves the cell
average, lies entirely within the invariant region and does not destroy the
high order of accuracy for smooth solutions. Numerical tests are presented to
illustrate the properties of the limiter. In particular, the tests on Riemann
problems show that the limiter helps to damp the oscillations near
discontinuities.
|
1804.08814v1
|
2018-05-04
|
Resonance overlap and non-linear velocity spread in Hamiltonian beam-plasma systems
|
We analyze some specific features of the beam-plasma instability. In
particular, non-perturbative effects in the dispersion relation are studied
when the standard perturbative inverse Landau damping treatment breaks down. We
also elucidate how only the global distortion of the profile rather than the
clump width is truly predictive of resonance overlap at saturation.
|
1805.01821v2
|
2018-05-07
|
Implementation of Stochastic Quasi-Newton's Method in PyTorch
|
In this paper, we implement the Stochastic Damped LBFGS (SdLBFGS) for
stochastic non-convex optimization. We make two important modifications to the
original SdLBFGS algorithm. First, by initializing the Hessian at each step
using an identity matrix, the algorithm converges better than original
algorithm. Second, by performing direction normalization we could gain stable
optimization procedure without line search. Experiments on minimizing a 2D
non-convex function shows that our improved algorithm converges better than
original algorithm, and experiments on the CIFAR10 and MNIST datasets show that
our improved algorithm works stably and gives comparable or even better testing
accuracies than first order optimizers SGD, Adagrad, and second order
optimizers LBFGS in PyTorch.
|
1805.02338v1
|
2018-05-27
|
Global Well-Posedness of a 3D MHD Model in Porous Media
|
In this paper we show the global well-posedness of solutions to a
three-dimensional magnetohydrodynamical (MHD) model in porous media. Compared
to the classical MHD equations, our system involves a nonlinear damping term in
the momentum equations due to the "Brinkman-Forcheimer-extended-Darcy" law of
flow in porous media.
|
1805.10661v2
|
2018-06-13
|
Canonical Models of Dielectric Response
|
The interaction of electromagnetic fields with a solid is characterized by
several interconnected response functions: the dielectric function
$\varepsilon(\omega)$, index of refraction $N(\omega)$, conductivity
$\sigma(\omega)$, and optical impedance $Z(\omega)$. Here we utilize three
canonical models of dielectric response -- the damped harmonic oscillator,
Debye polarization response, and the Drude model -- to discuss these four
optical response functions. Special emphasis is devoted to the response of a
Drude metal. Our main focus is on electromagnetic wave propagation through a
material. We also discuss the relaxation of charge fluctuations within the
context of the three canonical models of response.
|
1806.05158v1
|
2018-06-20
|
Mean Field Analysis of Personalized PageRank with Implications for Local Graph Clustering
|
We analyse a mean-field model of Personalized PageRank on the Erdos-Renyi
random graph containing a denser planted Erdos-Renyi subgraph. We investigate
the regimes where the values of Personalized PageRank concentrate around the
mean-field value. We also study the optimization of the damping factor, the
only parameter in Personalized PageRank. Our theoretical results help to
understand the applicability of Personalized PageRank and its limitations for
local graph clustering.
|
1806.07640v1
|
2018-06-24
|
Existence of time-periodic strong solutions to a fluid-structure system
|
We study a nonlinear coupled fluid-structure system modelling the blood flow
through arteries. The fluid is described by the incompressible Navier-Stokes
equations in a 2D rectangular domain where the upper part depends on a
structure satisfying a damped Euler-Bernoulli beam equation. The system is
driven by time-periodic source terms on the inflow and outflow boundaries. We
prove the existence of time-periodic strong solutions for this problem under
smallness assumptions for the source terms.
|
1806.09173v1
|
2018-09-04
|
Thermal noise in complex systems
|
We present a method to calculate the power spectral density of Brownian noise
in complex optomechanical systems using Levin's approach of virtual pressure
and present first mechanical loss measurements for high-purity GaAs over a wide
temperature range from 7 K to 250 K. The loss reveals three Debye loss peaks.
Each peak corresponds to an Arrhenius-like relaxation process with activation
energies of 17.9 meV, 65.4 meV and 123 meV respectively. Additional light
induced damping was observed for photon energies below and above the
fundamental gap of GaAs in contrast to observations by Okamoto et al.
|
1809.10720v1
|
2018-11-06
|
Chaotic Synchronization between Atomic Clocks
|
We predict synchronization of the chaotic dynamics of two atomic ensembles
coupled to a heavily damped optical cavity mode. The atoms are dissipated
collectively through this mode and pumped incoherently to achieve a macroscopic
population of the cavity photons. Even though the dynamics of each ensemble are
chaotic, their motions repeat one another. In our system, chaos first emerges
via quasiperiodicity and then synchronizes. We identify the signatures of
synchronized chaos, chaos, and quasiperiodicity in the experimentally
observable power spectra of the light emitted by the cavity.
|
1811.02148v2
|
2018-11-06
|
Nonlinear Dynamics Semi-classical Model of Quantum Spin
|
A nonlinear dynamics semi-classical model is used to show that standard
quantum spin analysis can be obtained. The model includes a classically driven
nonlinear differential equation with dissipation and a semi-classical
interpretation of the torque on a spin magnetic moment in the presence of a
realistic magnetic field, which will represent two equilibrium positions. The
highly complicated driven nonlinear dissipative semi-classical model is used to
introduce chaos, which is necessary to produce the correct statistical quantum
results. The resemblance between this semi-classical spin model and the
thoroughly studied classical driven-damped nonlinear pendulum are shown and
discussed.
|
1811.02645v1
|
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