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2007-05-25 | The Secular Evolution of a Close Ring-Satellite System: The Excitation of Spiral Bending Waves at a Nearby Gap Edge | The secular perturbations exerted by an inclined satellite orbiting in a gap
in a broad planetary ring tends to excite the inclinations of the nearby ring
particles, and the ring's self-gravity can allow that disturbance to propagate
away in the form of a spiral bending wave. The amplitude of this spiral bending
wave is determined, as well as the wavelength, which shrinks as the waves
propagate outwards due to the effects of the central planet's oblateness. The
excitation of these bending waves also damps the satellite's inclination I.
This secular I damping is also compared to the inclination excitation that is
due to the satellite's many other vertical resonances in the ring, and the
condition for inclination damping is determined. The secular I damping is
likely responsible for confining the orbits of Saturn's two known gap-embedded
moons, Pan and Daphnis, to the ring plane. | 0705.3797v1 |
2007-06-15 | Anticorrelation between temperature and fluctuations in moderately damped Josephson junctions | We study the influence of dissipation on the switching current statistics of
moderately damped Josephson junctions. Different types of both low- and high-
$T_c$ junctions with controlled damping are studied. The damping parameter of
the junctions is tuned in a wide range by changing temperature, magnetic field,
gate voltage, introducing a ferromagnetic layer or in-situ capacitive shunting.
A paradoxical collapse of switching current fluctuations occurs with increasing
$T$ in all studied junctions. The phenomenon critically depends on dissipation
in the junction and is explained by interplay of two counteracting consequences
of thermal fluctuations, which on the one hand assist in premature switching
into the resistive state and on the other hand help in retrapping back to the
superconducting state. This is one of the rare examples of anticorrelation
between temperature and fluctuation amplitude of a physically measurable
quantity. | 0706.2248v1 |
2007-08-06 | Collisionless damping of electron waves in non-Maxwellian plasma | In this paper we have criticized the so-called Landau damping theory. We have
analyzed solutions of the standard dispersion equations for longitudinal
(electric) and transversal (electromagnetic and electron) waves in
half-infinite slab of the uniform collisionless plasmas with non-Maxwellian and
Maxwellian-like electron energy distribution functions. One considered the most
typical cases of both the delta-function type distribution function (the plasma
stream with monochromatic electrons) and distribution functions, different from
Maxwellian ones as with a surplus as well as with a shortage in the Maxwellian
distribution function tail. It is shown that there are present for the
considered cases both collisionless damping and also non-damping electron waves
even in the case of non-Maxwellian distribution function. | 0708.0748v5 |
2007-08-14 | Preliminary Results on Vibration Damping Properties of Nanoscale-Reinforced Composite Materials | The focus in this paper is an analysis of existing state of the arts directed
toward the development of the next generation of vibration damping systems. The
research work concentrates on an investigation related to
nanoparticles/fibres/tubes-reinforced materials and coatings dynamic
characterization and modeling of the fundamental phenomena that control
relationships between structure and damping/mechanical properties of the
materials. We simulated composite materials using finite element and mesh free
methods, using a hollow shell representation of the individual nanotube/fiber.
Results of the research work will provide a platform for the development of
nanoparticle-reinforced damping materials that are light-weight, vibration and
shock resistant. The outcome of the research work is expected to have
wide-ranging technical benefits with direct relevance to industry in areas of
transportation (aerospace, automotive, rail), electronics and civil
infrastructure development. | 0708.1821v1 |
2007-08-18 | Non-Riemannian geometrical asymmetrical damping stresses on the Lagrange instability of shear flows | It is shown that the physical interpretation of Elie Cartan three-dimensional
space torsion as couple asymmetric stress, has the effect of damping,
previously Riemannian unstable Couette planar shear flow, leading to stability
of the flow in the Lagrangean sense. Actually, since the flow speed is
inversely proportional to torsion, it has the effect of causing a damping in
the planar flow atenuating the instability effect. In this sense we may say
that Cartan torsion induces shear viscous asymmetric stresses in the fluid,
which are able to damp the instability of the flow. The stability of the flow
is computed from the sectional curvature in non-Riemannian three-dimensional
manifold. Marginal stability is asssumed by making the sectional non-Riemannian
curvature zero, which allows us to determine the speeds of flows able to induce
this stability. The ideas discussed here show that torsion plays the
geometrical role of magnetic field in hydromagnetic instability of Couette
flows recently investigated by Bonnano and Urpin (PRE, (2007,in press) can be
extended and applied to plastic flows with microstructure defects. Recently
Riemannian asymmetric stresses in magnetohydrodynamics (MHD) have been
considered by Billig (2004). | 0708.2467v1 |
2007-12-07 | State transition of a non-Ohmic damping system in a corrugated plane | Anomalous transport of a particle subjected to non-Ohmic damping of the power
$\delta$ in a tilted periodic potential is investigated via Monte Carlo
simulation of generalized Langevin equation. It is found that the system
exhibits two relative motion modes: the locking state and the running state.
Under the surrounding of sub-Ohmic damping ($0<\delta<1$), the particle should
transfer into a running state from a locking state only when local minima of
the potential vanish; hence the particle occurs a synchronization oscillation
in its mean displacement and mean square displacement (MSD). In particular, the
two motion modes are allowed to coexist in the case of super-Ohmic damping
($1<\delta<2$) for moderate driving forces, namely, where exists double centers
in the velocity distribution. This induces the particle having faster
diffusion, i.e., its MSD reads $<\Delta x^2(t)> = 2D^{(\delta)}_{eff}
t^{\delta_{eff}}$. Our result shows that the effective power index
$\delta_{\textmd{eff}}$ can be enhanced and is a nonmonotonic function of the
temperature and the driving force. The mixture effect of the two motion modes
also leads to a breakdown of hysteresis loop of the mobility. | 0712.1070v1 |
2007-12-25 | The damped Pinney equation and its applications to dissipative quantum mechanics | The work considers the damped Pinney equation, defined as the model arising
when a linear in velocity damping term is included in the Pinney equation. In
the general case the resulting equation does not admit Lie point symmetries or
is reducible to a simpler form by any obvious coordinate transformation. In
this context the method of Kuzmak-Luke is applied to derive a perturbation
solution, for weak damping and slow time-dependence of the frequency function.
The perturbative and numerical solutions are shown to be in good agreement. The
results are applied to examine the time-evolution of Gaussian shaped
wave-functions in the Kostin formulation of dissipative quantum mechanics. | 0712.4083v3 |
2008-01-01 | Non-linear equations for electron waves in Maxwellian low-collision ion-electron plasmas | The before described general principles and methodology of calculating
electron wave propagation in homogeneous isotropic half-infinity slab of
Maxwellian plasma with indefinite but in principal value sense taken integrals
in characteristic equations, and the use of 2D Laplace transform method are
applied to an evaluation of collision damping decrements of plane electron
longitudinal and transverse waves. Damping decrement tends to infinity when the
wave frequency tends to electron Langmuir frequency from above values. We
considered recurrent relations for amplitudes of the overtones which form in
their sum the all solution of the plasma wave non-linear equations including
collision damping and quadratic (non-linear) terms. Collisionless damping at
frequencies more the Langmuir one is possible only in non-Maxwellian plasmas. | 0801.0286v2 |
2008-02-22 | Radiative Damping and Functional Differential Equations | We propose a general technique to solve the classical many-body problem with
radiative damping. We modify the short-distance structure of Maxwell
electrodynamics. This allows us to avoid runaway solutions as if we had a
covariant model of extended particles. The resulting equations of motion are
functional differential equations (FDEs) rather than ordinary differential
equations. Using recently developed numerical techniques for stiff FDEs, we
solve these equations for the one-body central force problem with radiative
damping with a view to benchmark our new approach. Our results indicate that
locally the magnitude of radiation damping may be well approximated by the
standard third-order expression but the global properties of our solutions are
dramatically different. We comment on the two body problem and applications to
quantum field theory and quantum mechanics. | 0802.3390v2 |
2008-04-24 | Analytic approximate seismology of transversely oscillating coronal loops | We present an analytic approximate seismic inversion scheme for damped
transverse coronal loop oscillations based on the thin tube and thin boundary
approximation for computing the period and the damping time. Asymptotic
expressions for the period and damping rate are used to illustrate the process
of seismological inversion in a simple and easy to follow manner. The inversion
procedure is formulated in terms of two simple functions, which are given by
simple closed expressions. The analytic seismic inversion shows that an
infinite amount of 1-dimensional equilibrium models can reproduce the observed
periods and damping times. It predicts a specific range of allowable values for
the Alfven travel time and lower bounds for the density contrast and the
inhomogeneity length scale. When the results of the present analytic seismic
inversion are compared with those of a previous numerical inversion, excellent
agreement is found up to the point that the analytic seismic inversion emerges
as a tool for validating results of numerical inversions. Actually it helped us
to identify and correct inaccuracies in a previous numerical investigation. | 0804.3877v1 |
2009-01-08 | Grand-mother clocks and quiet lasers | Galileo noted in the 16th century that the period of oscillation of a
pendulum is almost independent of the amplitude. However, such a pendulum is
damped by air friction. The latter may be viewed as resulting from air
molecules getting in contact with the pendulum. It follows that air friction,
not only damps the oscillation, but also introduces randomness. In the
so-called ``grand-mother'' clock, discovered by Huygens in the 18th century,
damping is compensated for, on the average, by an escapement mechanism driven
by a falling weight. The purpose of this paper is to show that such a clock is,
in its idealized form, a quiet oscillator. By ``quiet'' we mean that in spite
of the randomness introduced by damping, the dissipated power (viewed as the
oscillator output) does not fluctuate slowly. Comparison is made with quiet
laser oscillators discovered theoretically in 1984. Because the input power
does not fluctuate in both the mechanical oscillator and the quiet laser
oscillator, the output power does not fluctuate at small Fourier frequencies,
irrespectively of the detailed mechanisms involved. | 0901.0983v1 |
2009-01-15 | Interaction of fast charged projectiles with two-dimensional electron gas: Interaction and disorder effects | The results of a theoretical investigation on the stopping power of ions
moving in a disordered two-dimensional degenerate electron gas are presented.
The stopping power for an ion is calculated employing linear response theory
using the dielectric function approach. The disorder, which leads to a damping
of plasmons and quasiparticles in the electron gas, is taken into account
through a relaxation time approximation in the linear response function. The
stopping power for an ion is calculated in both the low- and high-velocity
limits. In order to highlight the effects of damping we present a comparison of
our analytical and numerical results, in the case of point-like ions, obtained
for a non-zero damping with those for a vanishing damping. It is shown that the
equipartition sum rule first formulated by Lindhard and Winther for
three-dimensional degenerate electron gas does not necessarily hold in
two-dimensions. We have generalized this rule introducing an effective
dielectric function. In addition some new results for two-dimensional
interacting electron gas have been obtained. In this case the
exchange-correlation interactions of electrons are considered via
local-field-corrected dielectric function. | 0901.2249v1 |
2009-02-01 | Non-Markovian Analysis of the Phase Damped Jaynes-Cummings Model in the Presence of a Classical Homogeneous Gravitational Field | In this paper, the non-Markovian dissipative dynamics of the phase damped
Jaynes-Cummings model in the presence of a classical homogeneous gravitational
field will be analyzed. The model consists of a moving two-level atom
simultaneously exposed to the gravitational field and a single-mode traveling
radiation field in the presence of a non-Markovian phase damping mechanism.
First, the non-Markovian master equation for the reduced density operator of
the system in terms of a Hamiltonian describing the atom-field interaction in
the presence of a homogeneous gravitational field will be presented. Then, the
super-operator technique will be generalized and an exact solution of the
non-Markovian master equation will be obtained. Assuming that initially the
radiation field is prepared in a Glauber coherent state and the two-level atom
is in the excited state, the non-Markovian effects on the temporal evolution of
collapses and revivals of the atomic population inversion and photon counting
statistics of the radiation field in the presence of both the phase damping and
a homogeneous gravitational field will be investigated. | 0902.0114v1 |
2009-05-04 | Models of Damped Oscillators in Quantum Mechanics | We consider several models of the damped oscillators in nonrelativistic
quantum mechanics in a framework of a general approach to the dynamics of the
time-dependent Schroedinger equation with variable quadratic Hamiltonians. The
Green functions are explicitly found in terms of elementary functions and the
corresponding gauge transformations are discussed. The factorization technique
is applied to the case of a shifted harmonic oscillator. The time-evolution of
the expectation values of the energy related operators is determined for two
models of the quantum damped oscillators under consideration. The classical
equations of motion for the damped oscillations are derived for the
corresponding expectation values of the position operator. | 0905.0507v6 |
2009-05-28 | Resonant Nonlinear Damping of Quantized Spin Waves in Ferromagnetic Nanowires | We use spin torque ferromagnetic resonance to measure the spectral properties
of dipole-exchange spin waves in permalloy nanowires. Our measurements reveal
that geometric confinement has a profound effect on the damping of spin waves
in the nanowire geometry. The damping parameter of the lowest-energy quantized
spin wave mode depends on applied magnetic field in a resonant way and exhibits
a maximum at a field that increases with decreasing nanowire width. This
enhancement of damping originates from a nonlinear resonant three-magnon
confluence process allowed at a particular bias field value determined by
quantization of the spin wave spectrum in the nanowire geometry. | 0905.4699v2 |
2009-06-01 | Effect of Decoherence in Ekert-Protocol | We have examined the effect of the decoherence in the Ekert91 quantum
cryptographic protocol. In order to explore this issue we have introduced two
major decoherences, the depolarizing channel and the generalized amplitude
damping, between the singlet source and one of the legitimate users. It is
shown that the depolarizing channel disentangles the quantum channel more
easily than the generalized amplitude damping. This fact indicates that the
Ekert protocol is more robust to the generalized amplitude damping. We also
have computed the Bell inequality to check the robustness or weakness of the
Ekert91 protocol. Computation of the Bell inequality also confirms the
robustness of the Ekert91 protocol to the generalized amplitude damping
compared to the depolarizing channel. | 0906.0233v1 |
2009-08-05 | Surface plasmon lifetime in metal nanoshells | The lifetime of localized surface plasmon plays an important role in many
aspects of plasmonics and its applications. In small metal nanostructures, the
dominant mechanism restricting plasmon lifetime is size-dependent Landau
damping. We performed quantum-mechanical calculations of Landau damping for the
bright surface plasmon mode in a metal nanoshell. In contrast to the
conventional model based on the electron surface scattering, we found that the
damping rate decreases as the nanoshell thickness is reduced. The origin of
this behavior is traced to the spatial distribution of plasmon local field
inside the metal shell. We also found that, due to interference of electron
scattering amplitudes from nanoshell's two metal surfaces, the damping rate
exhibits pronounced quantum beats with changing shell thickness. | 0908.0647v3 |
2009-08-12 | Coarse Grained Simulations of a Small Peptide: Effects of Finite Damping and Hydrodynamic Interactions | In the coarse grained Brownian Dynamics simulation method the many solvent
molecules are replaced by random thermal kicks and an effective friction acting
on the particles of interest. For Brownian Dynamics the friction has to be so
strong that the particles' velocities are damped much faster than the duration
of an integration timestep. Here we show that this conceptual limit can be
dropped with an analytic integration of the equations of damped motion. In the
resulting Langevin integration scheme our recently proposed approximate form of
the hydrodynamic interactions between the particles can be incorparated
conveniently, leading to a fast multi-particle propagation scheme, which
captures more of the short-time and short-range solvent effects than standard
BD. Comparing the dynamics of a bead-spring model of a short peptide, we
recommend to run simulations of small biological molecules with the Langevin
type finite damping and to include the hydrodynamic interactions. | 0908.1685v1 |
2009-09-01 | Quantum Stackelberg duopoly in the presence of correlated noise | We study the influence of entanglement and correlated noise using correlated
amplitude damping, depolarizing and phase damping channels on the quantum
Stackelberg duopoly. Our investigations show that under the action of amplitude
damping channel a critical point exists for unentangled initial state as well,
at which firms get equal payoffs. The game becomes a follower advantage game
when the channel is highly decohered. Two critical points corresponding to two
values of the entanglement angle are found in the presence of correlated noise.
Within the range of these limits of entanglement angle, the game is follower
advantage game. In case of depolarizing channel, the payoffs of the two firms
are strongly influenced by the memory parameter. The presence of quantum memory
ensures the existence of Nash equilibrium for the entire range of decoherence
and entanglement parameters for both the channels. A local maximum in the
payoffs is observed which vanishes as the channel correlation increases.
Moreover, under the influence of depolarizing channel, the game is always a
leader advantage game. Furthermore, it is seen that phase damping channel does
not effect the outcome of the game. | 0909.0063v2 |
2009-09-04 | Second sound dipole mode in a partially Bose-Einstein condensed gas | We study the second sound dipole mode in a partially Bose-Einstein condensed
gas. This mode is excited by spatially separating and releasing the
center-of-mass of the Bose-Einstein condensate (BEC) with respect to the
thermal cloud, after which the equilibration is observed. The oscillation
frequency and the damping rate of this mode is studied for different harmonic
confinements and temperatures. The measured damping rates close to the
collisionless regime are found to be in good agreement with Landau damping. For
increasing hydrodynamicity of the cloud we observe an increase of the damping. | 0909.0886v1 |
2009-12-30 | Finite dimensional attractor for a composite system of wave/plate equations with localised damping | The long-term behaviour of solutions to a model for acoustic-structure
interactions is addressed; the system is comprised of coupled semilinear wave
(3D) and plate equations with nonlinear damping and critical sources. The
questions of interest are: existence of a global attractor for the dynamics
generated by this composite system, as well as dimensionality and regularity of
the attractor. A distinct and challenging feature of the problem is the
geometrically restricted dissipation on the wave component of the system. It is
shown that the existence of a global attractor of finite fractal dimension --
established in a previous work by Bucci, Chueshov and Lasiecka (Comm. Pure
Appl. Anal., 2007) only in the presence of full interior acoustic damping --
holds even in the case of localised dissipation. This nontrivial generalization
is inspired by and consistent with the recent advances in the study of wave
equations with nonlinear localised damping. | 0912.5464v2 |
2010-02-12 | Features of ion acoustic waves in collisional plasmas | The effects of friction on the ion acoustic (IA) wave in fully and partially
ionized plasmas are studied. In a quasi-neutral electron-ion plasma the
friction between the two species cancels out exactly and the wave propagates
without any damping. If the Poisson equation is used instead of the
quasi-neutrality, however, the IA wave is damped and the damping is dispersive.
In a partially ionized plasma, the collisions with the neutrals modify the IA
wave beyond recognition. For a low density of neutrals the mode is damped. Upon
increasing the neutral density, the mode becomes first evanescent and then
reappears for a still larger number of neutrals. A similar behavior is obtained
by varying the mode wave-length. The explanation for this behavior is given. In
an inhomogeneous plasma placed in an external magnetic field, and for
magnetized electrons and un-magnetized ions, the IA mode propagates in any
direction and in this case the collisions make it growing on the account of the
energy stored in the density gradient. The growth rate is angle dependent. A
comparison with the collision-less kinetic density gradient driven IA
instability is also given. | 1002.2502v1 |
2010-02-18 | Damping mechanisms for oscillations in solar prominences | Small amplitude oscillations are a commonly observed feature in
prominences/filaments. These oscillations appear to be of local nature, are
associated to the fine structure of prominence plasmas, and simultaneous flows
and counterflows are also present. The existing observational evidence reveals
that small amplitude oscillations, after excited, are damped in short spatial
and temporal scales by some as yet not well determined physical mechanism(s).
Commonly, these oscillations have been interpreted in terms of linear
magnetohydrodynamic (MHD) waves, and this paper reviews the theoretical damping
mechanisms that have been recently put forward in order to explain the observed
attenuation scales. These mechanisms include thermal effects, through
non-adiabatic processes, mass flows, resonant damping in non-uniform media, and
partial ionization effects. The relevance of each mechanism is assessed by
comparing the spatial and time scales produced by each of them with those
obtained from observations. Also, the application of the latest theoretical
results to perform prominence seismology is discussed, aiming to determine
physical parameters in prominence plasmas that are difficult to measure by
direct means. | 1002.3489v2 |
2010-03-07 | Theory of plasmon decay in dense plasmas and warm dense matter | The decay of the Langmuir waves in dense plasmas is not accurately predicted
by the prevalent Landau damping theory. A dielectric function theory is
introduced, predicting much higher damping than the Landau damping theory. This
strong damping is in better agreement with the experimentally observed data in
metals. It is shown that the strong plasmon decay leads to the existence of a
parameter regime where the backward Raman scattering is unstable while the
forward Raman scattering is stable. This regime may be used to create intense
x-ray pulses, by means of the the backward Raman compression. The optimal pulse
duration and intensity is estimated. | 1003.1523v2 |
2010-03-16 | Justification of the symmetric damping model of the dynamical Casimir effect in a cavity with a semiconductor mirror | A "microscopic" justification of the "symmetric damping" model of a quantum
oscillator with time-dependent frequency and time-dependent damping is given.
This model is used to predict results of experiments on simulating the
dynamical Casimir effect in a cavity with a photo-excited semiconductor mirror.
It is shown that the most general bilinear time-dependent coupling of a
selected oscillator (field mode) to a bath of harmonic oscillators results in
two equal friction coefficients for the both quadratures, provided all the
coupling coefficients are proportional to a single arbitrary function of time
whose duration is much shorter than the periods of all oscillators. The choice
of coupling in the rotating wave approximation form leads to the "mimimum
noise" model of the quantum damped oscillator, introduced earlier in a pure
phenomenological way. | 1003.3061v2 |
2010-05-23 | Constraining phases of quark matter with studies of r-mode damping in neutron stars | The r-mode instability in rotating compact stars is used to constrain the
phase of matter at high density. The color-flavor-locked phase with kaon
condensation (CFL-K0) and without (CFL) is considered in the temperature range
10^8K < T <10^{11} K. While the bulk viscosity in either phase is only
effective at damping the r-mode at temperatures T > 10^{11} K, the shear
viscosity in the CFL-K0 phase is the only effective damping agent all the way
down to temperatures T > 10^8 K characteristic of cooling neutron stars.
However, it cannot keep the star from becoming unstable to gravitational wave
emission for rotation frequencies f ~ 56-11 Hz at T ~ 10^8-10^9 K. Stars
composed almost entirely of CFL or CFL-K0 matter are ruled out by observation
of rapidly rotating neutron stars, indicating that dissipation at the
quark-hadron interface or nuclear crust interface must play a key role in
damping the instability. | 1005.4161v1 |
2010-07-07 | Observational evidence of resonantly damped propagating kink waves in the solar corona | In this Letter we establish clear evidence for the resonant absorption
damping mechanism by analyzing observational data from the novel Coronal
Multi-Channel Polarimeter (CoMP). This instrument has established that in the
solar corona there are ubiquitous propagating low amplitude ($\approx$1 km
s$^{-1}$) Alfv\'{e}nic waves with a wide range of frequencies. Realistically
interpreting these waves as the kink mode from magnetohydrodynamic (MHD) wave
theory, they should exhibit a frequency dependent damping length due to
resonant absorption, governed by the TGV relation showing that transversal
plasma inhomogeneity in coronal magnetic flux tubes causes them to act as
natural low-pass filters. It is found that observed frequency dependence on
damping length (up to about 8 mHz) can be explained by the kink wave
interpretation and furthermore, the spatially averaged equilibrium parameter
describing the length scale of transverse plasma density inhomogeneity over a
system of coronal loops is consistent with the range of values estimated from
TRACE observations of standing kink modes. | 1007.1080v1 |
2010-07-12 | Variable damping and coherence in a high-density magnon gas | We report on the fast relaxation behavior of a high-density magnon gas
created by a parametric amplification process. The magnon gas is probed using
the technique of spin-wave packet recovery by parallel parametric pumping.
Experimental results show a damping behavior which is in disagreement with both
the standard model of exponential decay and with earlier observations of
non-linear damping. In particular, the inherent magnon damping is found to
depend upon the presence of the parametric pumping field. A phenomenological
model which accounts for the dephasing of the earlier injected magnons is in
good agreement with the experimental data. | 1007.1895v3 |
2010-07-21 | A low-power circuit for piezoelectric vibration control by synchronized switching on voltage sources | In the paper, a vibration damping system powered by harvested energy with
implementation of the so-called SSDV (synchronized switch damping on voltage
source) technique is designed and investigated. In the semi-passive approach,
the piezoelectric element is intermittently switched from open-circuit to
specific impedance synchronously with the structural vibration. Due to this
switching procedure, a phase difference appears between the strain induced by
vibration and the resulting voltage, thus creating energy dissipation. By
supplying the energy collected from the piezoelectric materials to the
switching circuit, a new low-power device using the SSDV technique is proposed.
Compared with the original self-powered SSDI (synchronized switch damping on
inductor), such a device can significantly improve its performance of vibration
control. Its effectiveness in the single-mode resonant damping of a composite
beam is validated by the experimental results. | 1007.3596v1 |
2010-10-24 | Long-time dynamics in plate models with strong nonlinear damping | We study long-time dynamics of a class of abstract second order in time
evolution equations in a Hilbert space with the damping term depending both on
displacement and velocity. This damping represents the nonlinear strong
dissipation phenomenon perturbed with relatively compact terms. Our main result
states the existence of a compact finite dimensional attractor. We study
properties of this attractor. We also establish the existence of a fractal
exponential attractor and give the conditions that guarantee the existence of a
finite number of determining functionals. In the case when the set of
equilibria is finite and hyperbolic we show that every trajectory is attracted
by some equilibrium with exponential rate. Our arguments involve a recently
developed method based on the "compensated" compactness and quasi-stability
estimates. As an application we consider the nonlinear Kirchhoff, Karman and
Berger plate models with different types of boundary conditions and strong
damping terms. Our results can be also applied to the nonlinear wave equations. | 1010.4991v1 |
2010-11-05 | Effects of Turbulence, Eccentricity Damping, and Migration Rate on the Capture of Planets into Mean Motion Resonance | Pairs of migrating extrasolar planets often lock into mean motion resonance
as they drift inward. This paper studies the convergent migration of giant
planets (driven by a circumstellar disk) and determines the probability that
they are captured into mean motion resonance. The probability that such planets
enter resonance depends on the type of resonance, the migration rate, the
eccentricity damping rate, and the amplitude of the turbulent fluctuations.
This problem is studied both through direct integrations of the full 3-body
problem, and via semi-analytic model equations. In general, the probability of
resonance decreases with increasing migration rate, and with increasing levels
of turbulence, but increases with eccentricity damping. Previous work has shown
that the distributions of orbital elements (eccentricity and semimajor axis)
for observed extrasolar planets can be reproduced by migration models with
multiple planets. However, these results depend on resonance locking, and this
study shows that entry into -- and maintenance of -- mean motion resonance
depends sensitively on migration rate, eccentricity damping, and turbulence. | 1011.1486v1 |
2010-11-21 | Quasi-normal frequencies: Semi-analytic results for highly damped modes | Black hole highly-damped quasi-normal frequencies (QNFs) are very often of
the form (offset)} + i n (gap). We have investigated the genericity of this
phenomenon for the Schwarzschild--deSitter (SdS) black hole by considering a
model potential that is piecewise Eckart (piecewise Poeschl-Teller), and
developing an analytic ``quantization condition'' for the highly-damped
quasi-normal frequencies. We find that the (offset) + i n(gap) behaviour is
common but not universal, with the controlling feature being whether or not the
ratio of the surface gravities is a rational number. We furthermore observed
that the relation between rational ratios of surface gravities and periodicity
of QNFs is very generic, and also occurs within different analytic approaches
applied to various types of black hole spacetimes. These observations are of
direct relevance to any physical situation where highly-damped quasi-normal
modes are important. | 1011.4634v1 |
2011-03-09 | Nonlinear damping in mechanical resonators based on graphene and carbon nanotubes | Carbon nanotubes and graphene allow fabricating outstanding nanomechanical
resonators. They hold promise for various scientific and technological
applications, including sensing of mass, force, and charge, as well as the
study of quantum phenomena at the mesoscopic scale. Here, we have discovered
that the dynamics of nanotube and graphene resonators is in fact highly exotic.
We propose an unprecedented scenario where mechanical dissipation is entirely
determined by nonlinear damping. As a striking consequence, the quality factor
Q strongly depends on the amplitude of the motion. This scenario is radically
different from that of other resonators, whose dissipation is dominated by a
linear damping term. We believe that the difference stems from the reduced
dimensionality of carbon nanotubes and graphene. Besides, we exploit the
nonlinear nature of the damping to improve the figure of merit of
nanotube/graphene resonators. | 1103.1788v1 |
2011-05-03 | Entanglement in a Bipartite Gaussian State | To examine the loss of entanglement in a two-particle Gaussian system, we
couple it to an environment and use the Non-Rotating Wave master equation to
study the system's dynamics. We also present a derivation of this equation. We
consider two different types of evolution. Under free evolution we find that
entanglement is lost quickly between the particles. When a harmonic potential
is added between the particles, two very different behaviours can be observed,
namely in the over and under-damped cases respectively, where the strength of
the damping is determined by how large the coupling to the bath is with respect
to the frequency of the potential. In the over-damped case, we find that the
entanglement vanishes at even shorter times than it does in the free evolution.
In the (very) under-damped case, we observe that the entanglement does not
vanish. Instead it oscillates towards a stable value. | 1105.0564v1 |
2011-06-15 | Plasma damping effects on the radiative energy loss of relativistic particles | The energy loss of a relativistic charge undergoing multiple scatterings
while traversing an infinite, polarizable and absorptive plasma is
investigated. Polarization and damping mechanisms in the medium are
phenomenologically modelled by a complex index of refraction. Apart from the
known Ter-Mikaelian effect related to the dielectric polarization of matter, we
find an additional, substantial reduction of the energy loss due to damping of
radiation. The observed effect is more prominent for larger damping and/or
larger energy of the charge. A conceivable analog of this phenomenon in QCD
could influence the study of jet quenching phenomena in ultra-relativistic
heavy-ion collisions at RHIC and LHC. | 1106.2856v3 |
2011-09-12 | Reduction of compressibility and parallel transfer by Landau damping in turbulent magnetized plasmas | Three-dimensional numerical simulations of decaying turbulence in a
magnetized plasma are performed using a so-called FLR-Landau fluid model which
incorporates linear Landau damping and finite Larmor radius (FLR) corrections.
It is shown that compared to simulations of compressible Hall-MHD, linear
Landau damping is responsible for significant damping of magnetosonic waves,
which is consistent with the linear kinetic theory. Compressibility of the
fluid and parallel energy cascade along the ambient magnetic field are also
significantly inhibited when the beta parameter is not too small. In contrast
with Hall-MHD, the FLR-Landau fluid model can therefore correctly describe
turbulence in collisionless plasmas such as the solar wind, providing an
interpretation for its nearly incompressible behavior. | 1109.2636v1 |
2011-09-24 | Existence of weak solutions for the generalized Navier-Stokes equations with damping | In this work we consider the generalized Navier-Stoke equations with the
presence of a damping term in the momentum equation. % The problem studied here
derives from the set of equations which govern the isothermal flow of
incompressible, homogeneous and non-Newtonian fluids. % For the generalized
Navier-Stokes problem with damping, we prove the existence of weak solutions by
using regularization techniques, the theory of monotone operators and
compactness arguments together with the local decomposition of the pressure and
the Lipschitz-truncation method. The existence result proved here holds for any
$q>\frac{2N}{N+2}$ and any $\sigma>1$, where $q$ is the exponent of the
diffusion term and $\sigma$ is the exponent which characterizes the damping
term. | 1109.5217v1 |
2011-11-14 | New Electrodynamics of Pulsars | We have recently proposed that Force-Free Electrodynamics (FFE) does not
apply to pulsars -- pulsars should be described by the high-conductivity limit
of Strong-Field Electrodynamics (SFE), which predicts an order-unity damping of
the Poynting flux, while FFE postulates zero damping. The strong damping result
has not been accepted by several pulsar experts, who claim that FFE basically
works and the Poynting flux damping can be arbitrarily small.
Here we consider a thought experiment -- cylindrical periodic pulsar. We show
that FFE is incapable of describing this object, while SFE predictions are
physically plausible. The intrinsic breakdown of FFE should mean that the FFE
description of the singular current layer (the only region of magnetosphere
where FFE and the high-conductivity SFE differ) is incorrect. Then the
high-conductivity SFE should be the right theory for real pulsars too, and the
pure-FFE description of pulsars should be discarded. | 1111.3377v1 |
2011-12-20 | Dynamics of DNA breathing in the Peyrard-Bishop model with damping and external force | The impact of damping effect and external forces to the DNA breathing is
investigated within the Peyrard-Bishop model. In in the continuum limit, the
dynamics of the breathing of DNA is described by the forced-damped nonlinear
Schrodinger equation and studied by means of variational method. The analytical
solutions are obtained for special cases. It is shown that the breather
propagation is decelerated in the presence of damping factor without the
external force, while the envelope velocity and the amplitude increase
significantly with the presence of external force. It is particularly found
that the higher harmonic terms are enhanced when the periodic force is applied.
It is finally argued that the external force accelerates the DNA breathing. | 1112.4715v1 |
2012-01-31 | Parametric amplification and self-oscillation in a nanotube mechanical resonator | A hallmark of mechanical resonators made from a single nanotube is that the
resonance frequency can be widely tuned. Here, we take advantage of this
property to realize parametric amplification and self-oscillation. The gain of
the parametric amplification can be as high as 18.2 dB and tends to saturate at
high parametric pumping due to nonlinear damping. These measurements allow us
to determine the coefficient of the linear damping force. The corresponding
damping rate is lower than the one obtained from the lineshape of the resonance
(without pumping), supporting the recently reported scenario that describes
damping in nanotube resonators by a nonlinear force. The possibility to combine
nanotube resonant mechanics and parametric amplification holds promise for
future ultra-low force sensing experiments. | 1201.6557v1 |
2012-04-03 | Inhomogeneity of the phase space of the damped harmonic oscillator under Levy noise | The damped harmonic oscillator under symmetric L\'{e}vy white noise shows
inhomogeneous phase space, which is in contrast to the homogeneous one of the
same oscillator under the Gaussian white noise, as shown in a recent paper [I.
M. Sokolov, W. Ebeling, and B. Dybiec, Phys. Rev. E \textbf{83}, 041118
(2011)]. The inhomogeneity of the phase space shows certain correlation between
the coordinate and the velocity of the damped oscillator under symmetric
L\'{e}vy white noise. In the present work we further explore the physical
origin of these distinguished features and find that it is due to the
combination of the damped effect and heavy tail of the noise. We demonstrate
directly this in the reduced coordinate $\tilde{x}$ versus velocity $\tilde{v}$
plots and identify the physics of the anti-association of the coordinate and
velocity. | 1204.0593v2 |
2012-06-20 | Metadamping: An emergent phenomenon in dissipative metamaterials | We theoretically demonstrate the concept of metadamping in dissipative
metamaterials. We consider an infinite mass-spring chain with repeated local
resonators and a statically equivalent periodic chain whose wave propagation
characteristics are based on Bragg scattering. For each system we introduce
identical viscous damping (dashpot) elements and compare the damping ratio
associated with all Bloch modes. We find that the locally resonant metamaterial
exhibits higher dissipation overall which indicates a damping emergence
phenomena due to the presence of local resonance. We conclude our investigation
by quantifying the degree of emergent damping as a function of the long-wave
speed of sound in the medium or the static stiffness. | 1206.4577v2 |
2012-07-12 | Spin Damping in an RF Atomic Magnetometer | Under negative feedback, the quality factor Q of a radio-frequency
magnetometer can be decreased by more than two orders of magnitude, so that any
initial perturbation of the polarized spin system can be rapidly damped,
preparing the magnetometer for detection of the desired signal. We find that
noise is also suppressed under such spin-damping, with a characteristic
spectral response corresponding to the type of noise; therefore magnetic,
photon-shot, and spin-projection noise can be measured distinctly. While the
suppression of resonant photon-shot noise implies the closed-loop production of
polarization-squeezed light, the suppression of resonant spin-projection noise
does not imply spin-squeezing, rather simply the broadening of the noise
spectrum with Q. Furthermore, the application of spin-damping during
phase-sensitive detection suppresses both signal and noise in such a way as to
increase the sensitivity bandwidth. We demonstrate a three-fold increase in the
magnetometer's bandwidth while maintaining 0.3 fT/\surdHz sensitivity. | 1207.2842v1 |
2012-07-12 | Damping of phase fluctuations in superfluid Bose gases | Using Popov's hydrodynamic approach we derive an effective Euclidean action
for the long-wavelength phase fluctuations of superfluid Bose gases in D
dimensions. We then use this action to calculate the damping of phase
fluctuations at zero temperature as a function of D. For D >1 and wavevectors |
k | << 2 mc (where m is the mass of the bosons and c is the sound velocity) we
find that the damping in units of the phonon energy E_k = c | k | is to leading
order gamma_k / E_k = A_D (k_0^D / 2 pi rho) (| k | / k_0)^{2 D -2}, where rho
is the boson density and k_0 =2 mc is the inverse healing length. For D -> 1
the numerical coefficient A_D vanishes and the damping is proportional to an
additional power of |k | /k_0; a self-consistent calculation yields in this
case gamma_k / E_k = 1.32 (k_0 / 2 pi rho)^{1/2} |k | / k_0. In one dimension,
we also calculate the entire spectral function of phase fluctuations. | 1207.3002v3 |
2012-08-27 | The properties of non-thermal X-ray filaments in young supernova remnants | Context. Young supernova remnants (SNRs) exhibit narrow filaments of
non-thermal X-ray emission whose widths can be limited either by electron
energy losses or damping of the magnetic field. Aims. We want to investigate
whether or not different models of these filaments can be observationally
tested. Methods. Using observational parameters of four historical remnants, we
calculate the filament profiles and compare the spectra of the filaments with
those of the total non-thermal emission. For that purpose, we solve an
one-dimensional stationary transport equation for the isotropic differential
number density of the electrons. Results. We find that the difference between
the spectra of filament and total non-thermal emission above 1 keV is more
pronounced in the damping model than in the energy-loss model. Conclusions. A
considerable damping of the magnetic field can result in an observable
difference between the spectra of filament and total non-thermal emission, thus
potentially permitting an observational discrimination between the energy-loss
model and the damping model of the X-ray filaments. | 1208.5322v1 |
2012-12-18 | Thermal activation at moderate-to-high and high damping: finite barrier effects and force spectroscopy | We study the thermal escape problem in the moderate-to-high and high damping
regime of a system with a parabolic barrier. We present a formula that matches
our numerical results accounting for finite barrier effects, and compare it
with previous works. We also show results for the full damping range. We
quantitatively study some aspects on the relation between mean first passage
time and the definition of a escape rate. To finish we apply our results and
considerations in the framework of force spectroscopy problems. We study the
differences on the predictions using the different theories and discuss the
role of $\gamma \dot{F}$ as the relevant parameter at high damping. | 1212.4290v2 |
2013-01-18 | Interfacial roughening in non-ideal fluids: Dynamic scaling in the weak- and strong-damping regime | Interfacial roughening denotes the nonequilibrium process by which an
initially flat interface reaches its equilibrium state, characterized by the
presence of thermally excited capillary waves. Roughening of fluid interfaces
has been first analyzed by Flekkoy and Rothman [Phys. Rev. Lett. 75, 260
(1995)], where the dynamic scaling exponents in the weakly damped case in two
dimensions were found to agree with the Kardar-Parisi-Zhang universality class.
We extend this work by taking into account also the strong-damping regime and
perform extensive fluctuating hydrodynamics simulations in two dimensions using
the Lattice Boltzmann method. We show that the dynamic scaling behavior is
different in the weakly and strongly damped case. | 1301.4468v2 |
2013-02-02 | Achieving the Quantum Ground State of a Mechanical Oscillator using a Bose-Einstein Condensate with Back-Action and Cold Damping feedback schemes | We present a detailed study to show the possibility of approaching the
quantum ground-state of a hybrid optomechanical quantum device formed by a
Bose-Einstein condensate (BEC) confined inside a high-finesse optical cavity
with an oscillatory end mirror. Cooling is achieved using two experimentally
realizable schemes: back-action cooling and cold damping quantum feedback
cooling. In both the schemes, we found that increasing the two body atom-atom
interaction brings the mechanical oscillator to its quantum ground state. It
has been observed that back-action cooling is more effective in the good cavity
limit while the cold damping cooling scheme is more relevant in the bad cavity
limit. It is also shown that in the cold damping scheme, the device is more
efficient in the presence of BEC than in the absence of BEC. | 1302.0339v1 |
2013-02-27 | Resonantly damped oscillations of elliptically shaped stratified emerging coronal loops | The effects of both elliptical shape and stage of emergence of the coronal
loop on the resonant absorption of standing kink oscillations are studied. To
do so, a typical coronal loop is modeled as a zero-beta longitudinally
stratified cylindrical magnetic flux tube. We developed the connection formulae
for the resonant absorption of standing transversal oscillations of a coronal
loop with an elliptical shape, at various stages of its emergence. Using the
connection formulae, the dispersion relation is derived and solved numerically
to obtain the frequencies and damping rates of the fundamental and
first-overtone kink modes. Our numerical results show that both the elliptical
shape and stage of emergence of the loop alter the frequencies and damping
rates of the tube as well as the ratio of frequencies of the fundamental and
its first-overtone modes. However, the ratio of the oscillation frequency to
the damping rate is not affected by the tube shape and stage of its emergence
and also is independent of the density stratification parameter. | 1302.6884v1 |
2013-02-28 | Damping of Quantum Vibrations Revealed in Deep Sub-barrier Fusion | We demonstrate that when two colliding nuclei approach each other, their
quantum vibrations are damped near the touching point. We show that this
damping is responsible for the fusion hindrance phenomena measured in the deep
sub-barrier fusion reactions. To show those, we for the first time apply the
random-phase-approximation (RPA) method to the two-body $^{16}$O + $^{16}$O and
$^{40}$Ca + $^{40}$Ca systems. We calculate the octupole transition strengths
for the two nuclei adiabatically approaching each other. The calculated
transition strength drastically decreases near the touching point, strongly
suggesting the vanishing of the quantum couplings between the relative motion
and the vibrational intrinsic degrees of freedom of each nucleus. Based on this
picture, we also calculate the fusion cross section for the $^{40}$Ca +
$^{40}$Ca system using the coupled-channel method with the damping factor
simulating the vanishing of the couplings. The calculated results reproduce
well the experimental data, indicating that the smooth transition from the
sudden to adiabatic processes indeed occurs in the deep sub-barrier fusion
reactions. | 1302.7115v2 |
2013-03-14 | Microwave-assisted switching of a nanomagnet: analytical determination of the optimal microwave field | We analytically determine the optimal microwave field that allows for the
magnetization reversal of a nanomagnet modeled as a macrospin. This is done by
minimizing the total injected energy. The results are in good agreement with
the fields obtained numerically using the optimal control theory. For typical
values of the damping parameter, a weak microwave field is sufficient to induce
switching through a resonant process. The optimal field is orthogonal to the
magnetization direction at any time and modulated both in amplitude and
frequency. The dependence of the pulse shape on the applied field and damping
parameter is interpreted. The total injected energy is found to be
proportionnal to the energy barrier between the initial state and the saddle
point and to the damping parameter. This result may be used as a means for
probing the damping parameter in real nanoparticles. | 1303.3501v4 |
2013-04-05 | Nonlocal Gravity: Damping of Linearized Gravitational Waves | In nonlocal general relativity, linearized gravitational waves are damped as
they propagate from the source to the receiver in the Minkowski vacuum.
Nonlocal gravity is a generalization of Einstein's theory of gravitation in
which nonlocality is due to the gravitational memory of past events. That
nonlocal gravity is dissipative is demonstrated in this paper within certain
approximation schemes. The gravitational memory drag leads to the decay of the
amplitude of gravitational waves given by the exponential damping factor exp
(-t/\tau), where $\tau$ depends on the kernel of nonlocal gravity. The damping
time $\tau$ is estimated for gravitational waves of current observational
interest and is found to be of the order of, or longer than, the age of the
universe. | 1304.1769v1 |
2013-07-29 | Damping of Primordial Gravitational Waves from Generalized Sources | It has been shown that a cosmological background with an anisotropic stress
tensor, appropriate for a free streaming thermal neutrino background, can damp
primordial gravitational waves after they enter the horizon, and can thus
affect the CMB B-mode polarization signature due to such tensor modes. Here we
generalize this result, and examine the sensitivity of this effect to non-zero
neutrino masses, extra neutrino species, and also a possible relativistic
background of axions from axion strings. In particular, additional neutrinos
with cosmologically interesting neutrino masses at the O(1) eV level will
noticeably reduce damping compared to massless neutrinos for gravitational wave
modes with $k\tau_0 \approx 100-200$, where $\tau_0 \approx 2/H_0$ and $H_0$ is
the present Hubble parameter, while an axion background would produce a
phase-dependent damping distinct from that produced by neutrinos. | 1307.7571v1 |
2013-08-08 | Small global solutions to the damped two-dimensional Boussinesq equations | The two-dimensional (2D) incompressible Euler equations have been thoroughly
investigated and the resolution of the global (in time) existence and
uniqueness issue is currently in a satisfactory status. In contrast, the global
regularity problem concerning the 2D inviscid Boussinesq equations remains
widely open. In an attempt to understand this problem, we examine the damped 2D
Boussinesq equations and study how damping affects the regularity of solutions.
Since the damping effect is insufficient in overcoming the difficulty due to
the "vortex stretching", we seek unique global small solutions and the efforts
have been mainly devoted to minimizing the smallness assumption. By positioning
the solutions in a suitable functional setting (more precisely the homogeneous
Besov space $\mathring{B}^1_{\infty,1}$), we are able to obtain a unique global
solution under a minimal smallness assumption. | 1308.1723v1 |
2013-08-21 | Approximate quantum error correction for generalized amplitude damping errors | We present analytic estimates of the performances of various approximate
quantum error correction schemes for the generalized amplitude damping (GAD)
qubit channel. Specifically, we consider both stabilizer and nonadditive
quantum codes. The performance of such error-correcting schemes is quantified
by means of the entanglement fidelity as a function of the damping probability
and the non-zero environmental temperature. The recovery scheme employed
throughout our work applies, in principle, to arbitrary quantum codes and is
the analogue of the perfect Knill-Laflamme recovery scheme adapted to the
approximate quantum error correction framework for the GAD error model. We also
analytically recover and/or clarify some previously known numerical results in
the limiting case of vanishing temperature of the environment, the well-known
traditional amplitude damping channel. In addition, our study suggests that
degenerate stabilizer codes and self-complementary nonadditive codes are
especially suitable for the error correction of the GAD noise model. Finally,
comparing the properly normalized entanglement fidelities of the best
performant stabilizer and nonadditive codes characterized by the same length,
we show that nonadditive codes outperform stabilizer codes not only in terms of
encoded dimension but also in terms of entanglement fidelity. | 1308.4582v2 |
2013-12-18 | Radiative damping and synchronization in a graphene-based terahertz emitter | We investigate the collective electron dynamics in a recently proposed
graphene-based terahertz emitter under the influence of the radiative damping
effect, which is included self-consistently in a molecular dynamics approach.
We show that under appropriate conditions synchronization of the dynamics of
single electrons takes place, leading to a rise of the oscillating component of
the charge current. The synchronization time depends dramatically on the
applied dc electric field and electron scattering rate, and is roughly
inversely proportional to the radiative damping rate that is determined by the
carrier concentration and the geometrical parameters of the device. The
emission spectra in the synchronized state, determined by the oscillating
current component, are analyzed. The effective generation of higher harmonics
for large values of the radiative damping strength is demonstrated. | 1312.5193v1 |
2014-02-13 | On the Convergence of Approximate Message Passing with Arbitrary Matrices | Approximate message passing (AMP) methods and their variants have attracted
considerable recent attention for the problem of estimating a random vector
$\mathbf{x}$ observed through a linear transform $\mathbf{A}$. In the case of
large i.i.d. zero-mean Gaussian $\mathbf{A}$, the methods exhibit fast
convergence with precise analytic characterizations on the algorithm behavior.
However, the convergence of AMP under general transforms $\mathbf{A}$ is not
fully understood. In this paper, we provide sufficient conditions for the
convergence of a damped version of the generalized AMP (GAMP) algorithm in the
case of quadratic cost functions (i.e., Gaussian likelihood and prior). It is
shown that, with sufficient damping, the algorithm is guaranteed to converge,
although the amount of damping grows with peak-to-average ratio of the squared
singular values of the transforms $\mathbf{A}$. This result explains the good
performance of AMP on i.i.d. Gaussian transforms $\mathbf{A}$, but also their
difficulties with ill-conditioned or non-zero-mean transforms $\mathbf{A}$. A
related sufficient condition is then derived for the local stability of the
damped GAMP method under general cost functions, assuming certain strict
convexity conditions. | 1402.3210v3 |
2014-03-28 | Strichartz estimates and smooth attractors for a sub-quintic wave equation with fractional damping in bounded domains | The work is devoted to Dirichlet problem for sub-quintic semi-linear wave
equation with damping damping term of the form $(-\Delta)^\alpha\partial_t u$,
$\alpha\in(0,\frac{1}{2})$, in bounded smooth domains of $\Bbb R^3$. It appears
that to prove well-posedness and develop smooth attractor theory for the
problem we need additional regularity of the solutions, which does not follow
from the energy estimate. Considering the original problem as perturbation of
the linear one the task is reduced to derivation of Strichartz type estimate
for the linear wave equation with fractional damping, which is the main feature
of the work. Existence of smooth exponential attractor for the natural
dynamical system associated with the problem is also established. | 1403.7476v1 |
2014-05-16 | Damping of Confined Modes in a Ferromagnetic Thin Insulating Film: Angular Momentum Transfer Across a Nanoscale Field-defined Interface | We observe a dependence of the damping of a confined mode of precessing
ferromagnetic magnetization on the size of the mode. The micron-scale mode is
created within an extended, unpatterned YIG film by means of the intense local
dipolar field of a micromagnetic tip. We find that damping of the confined mode
scales like the surface-to-volume ratio of the mode, indicating an interfacial
damping effect (similar to spin pumping) due to the transfer of angular
momentum from the confined mode to the spin sink of ferromagnetic material in
the surrounding film. Though unexpected for insulating systems, the measured
intralayer spin-mixing conductance $g_{\uparrow \downarrow} = 5.3 \times
10^{19} {\rm m}^{-2}$ demonstrates efficient intralayer angular momentum
transfer. | 1405.4203v2 |
2014-06-03 | Persistently damped transport on a network of circles | In this paper we address the exponential stability of a system of transport
equations with intermittent damping on a network of $N \geq 2$ circles
intersecting at a single point $O$. The $N$ equations are coupled through a
linear mixing of their values at $O$, described by a matrix $M$. The activity
of the intermittent damping is determined by persistently exciting signals, all
belonging to a fixed class. The main result is that, under suitable hypotheses
on $M$ and on the rationality of the ratios between the lengths of the circles,
such a system is exponentially stable, uniformly with respect to the
persistently exciting signals. The proof relies on an explicit formula for the
solutions of this system, which allows one to track down the effects of the
intermittent damping. | 1406.0731v4 |
2014-06-06 | Damping of quasiparticles in a Bose-Einstein condensate coupled to an optical cavity | We present a general theory for calculating the damping rate of elementary
density wave excitations in a Bose-Einstein condensate strongly coupled to a
single radiation field mode of an optical cavity. Thereby we give a detailed
derivation of the huge resonant enhancement in the Beliaev damping of a density
wave mode, predicted recently by K\'onya et al., Phys.~Rev.~A 89, 051601(R)
(2014). The given density-wave mode constitutes the polariton-like soft mode of
the self-organization phase transition. The resonant enhancement takes place,
both in the normal and ordered phases, outside the critical region. We show
that the large damping rate is accompanied by a significant frequency shift of
this polariton mode. Going beyond the Born-Markov approximation and determining
the poles of the retarded Green's function of the polariton, we reveal a strong
coupling between the polariton and a collective mode in the phonon bath formed
by the other density wave modes. | 1406.1669v1 |
2014-08-18 | Kirchhoff equations with strong damping | We consider Kirchhoff equations with strong damping, namely with a friction
term which depends on a power of the "elastic" operator. We address local and
global existence of solutions in two different regimes depending on the
exponent in the friction term.
When the exponent is greater than 1/2, the dissipation prevails, and we
obtain global existence in the energy space assuming only degenerate
hyperbolicity and continuity of the nonlinear term. When the exponent is less
than 1/2, we assume strict hyperbolicity and we consider a phase space
depending on the continuity modulus of the nonlinear term and on the exponent
in the damping. In this phase space we prove local existence, and global
existence if initial data are small enough.
The regularity we assume both on initial data and on the nonlinear term is
weaker than in the classical results for Kirchhoff equations with standard
damping.
Proofs exploit some recent sharp results for the linearized equation and
suitably defined interpolation spaces. | 1408.3908v1 |
2014-08-28 | A convergent method for linear half-space kinetic equations | We give a unified proof for the well-posedness of a class of linear
half-space equations with general incoming data and construct a Galerkin method
to numerically resolve this type of equations in a systematic way. Our main
strategy in both analysis and numerics includes three steps: adding damping
terms to the original half-space equation, using an inf-sup argument and
even-odd decomposition to establish the well-posedness of the damped equation,
and then recovering solutions to the original half-space equation. The proposed
numerical methods for the damped equation is shown to be quasi-optimal and the
numerical error of approximations to the original equation is controlled by
that of the damped equation. This efficient solution to the half-space problem
is useful for kinetic-fluid coupling simulations. | 1408.6630v4 |
2014-09-02 | Damping effects in hole-doped graphene: the relaxation-time approximation | The dynamical conductivity of interacting multiband electronic systems
derived in Ref.[1] is shown to be consistent with the general form of the Ward
identity. Using the semiphenomenological form of this conductivity formula, we
have demonstrated that the relaxation-time approximation can be used to
describe the damping effects in weakly interacting multiband systems only if
local charge conservation in the system and gauge invariance of the response
theory are properly treated. Such a gauge-invariant response theory is
illustrated on the common tight-binding model for conduction electrons in
hole-doped graphene. The model predicts two distinctly resolved maxima in the
energy-loss-function spectra. The first one corresponds to the intraband
plasmons (usually called the Dirac plasmons). On the other hand, the second
maximum ($\pi$ plasmon structure) is simply a consequence of the van Hove
singularity in the single-electron density of states. The dc resistivity and
the real part of the dynamical conductivity are found to be well described by
the relaxation-time approximation, but only in the parametric space in which
the damping is dominated by the direct scattering processes. The ballistic
transport and the damping of Dirac plasmons are thus the questions that require
abandoning the relaxation-time approximation. | 1409.0621v1 |
2014-10-13 | Relaxation damping in oscillating contacts | If a contact of two purely elastic bodies with no sliding (infinite
coefficient of friction) is subjected to superimposed oscillations in the
normal and tangential directions, then a specific damping appears, that is not
dependent on friction or dissipation in the material. We call this effect
"relaxation damping". The rate of energy dissipation due to relaxation damping
is calculated in a closed analytic form for arbitrary axially-symmetric
contacts. In the case of equal frequency of normal and tangential oscillations,
the dissipated energy per cycle is proportional to the square of the amplitude
of tangential oscillation and to the absolute value of the amplitude of normal
oscillation, and is dependent on the phase shift between both oscillations. In
the case of low frequency tangential motion with superimposed high frequency
normal oscillations, the system acts as a tunable linear damper. Generalization
of the results for macroscopically planar, randomly rough surfaces is
discussed. | 1410.3238v1 |
2014-11-13 | Maximal correlation between flavor entanglement and oscillation damping due to localization effects | Localization effects and quantum decoherence driven by the mass-eigenstate
wave packet propagation are shown to support a statistical correlation between
quantum entanglement and damped oscillations in the scenario of three-flavor
quantum mixing for neutrinos. Once the mass-eigenstates that support flavor
oscillations are identified as three-{\em qubit} modes, a decoherence scale can
be extracted from correlation quantifiers, namely the entanglement of formation
and the logarithmic negativity. Such a decoherence scale is compared with the
coherence length of damped oscillations. Damping signatures exhibited by flavor
transition probabilities as an effective averaging of the oscillating terms are
then explained as owing to loss of entanglement between mass modes involved in
the relativistic propagation. | 1411.3634v1 |
2015-01-20 | Damping of long wavelength collective modes in spinor Bose-Fermi mixtures | Using an effective field theory we describe the low energy bosonic
excitations in a three dimensional ultra-cold mixture of spin-1 bosons and
spin-1/2 fermions. We establish an interesting fermionic excitation induced
generic damping of the usual undamped long wavelength bosonic collective
Goldstone modes. Two states with bosons forming either a ferromagnetic or polar
superfluid are studied. The linear dispersion of the bosonic Bogoliubov
excitations is preserved with a renormalized sound velocity. For the polar
superfluid we find both gapless modes (density and spin) are damped, whereas in
the ferromagnetic superfluid we find the density (spin) mode is (not) damped.
We argue quite generally that this holds for any mixture of bosons and fermions
that are coupled through at least a density-density interaction. We discuss the
implications of our many-body interaction results for experiments on Bose-Fermi
mixtures. | 1501.05015v2 |
2015-01-27 | Non-linear fluctuation effects in dynamics of freely suspended film | Long-scale dynamic fluctuation phenomena in freely suspended films is
analyzed. We consider isotropic films that, say, can be pulled from bulk
smectic A liquid crystals. The key feature of such objects is possibility of
bending deformations of the film. The bending (also known as flexular) mode
turns out to be anomalously weakly attenuated. In the harmonic approximation
there is no viscous-like damping of the bending mode, proportional to q^2 (q is
the wave vector of the mode), since it is forbidden by the rotational symmetry.
Therefore the bending mode is strongly affected by non-linear dynamic
fluctuation effects. We calculate the dominant fluctuation contributions to the
damping of the bending mode due to its coupling to the in-plane viscous mode,
that restores the viscous-like q^2 damping of the bending mode. Our
calculations are performed in the framework of the perturbation theory where
the coupling of the modes is assumed to be small, then the bending mode damping
is relatively weak. We discuss our results in the context of existing
experiments and numeric simulations of the freely suspended films and propose
possible experimental observations of our predictions. | 1501.06703v1 |
2015-07-21 | Onboard Calibration Circuit for the Front-end Electronics of DAMPE BGO Calorimeter | An onboard calibration circuit has been designed for the front-end
electronics (FEE) of DAMPE BGO Calorimeter. It is mainly composed of a 12 bit
DAC, an operation amplifier and an analog switch. Test results showed that a
dynamic range of 0 ~ 30 pC with a precision of 5 fC was achieved, which meets
the requirements of the front-end electronics. Furthermore, it is used to test
the trigger function of the FEEs. The calibration circuit has been implemented
and verified by all the environmental tests for both Qualification Model and
Flight Model of DAMPE. The DAMPE satellite will be launched at the end of 2015
and the calibration circuit will perform onboard calibration in space. | 1507.05862v1 |
2015-07-30 | Reservoir interactions during Bose-Einstein condensation: modified critical scaling in the Kibble-Zurek mechanism of defect formation | As a test of the Kibble-Zurek mechanism (KZM) of defect formation, we
simulate the Bose-Einstein condensation transition in a toroidally confined
Bose gas using the stochastic projected Gross-Pitaevskii equation (SPGPE), with
and without the energy-damping reservoir interaction. Energy-damping alters the
scaling of the winding number distribution with the quench time - a departure
from the universal KZM theory that relies on equilibrium critical exponents.
Numerical values are obtained for the correlation-length critical exponent
$\nu$ and the dynamical critical exponent $z$ for each variant of reservoir
interaction theory. The energy-damping reservoir interactions cause significant
modification of the dynamical critical exponent of the phase transition, whilst
preserving the essential KZM critical scaling behavior. Comparison of numerical
and analytical two-point correlation functions further illustrates the effect
of energy damping on the correlation length during freeze out. | 1507.08357v1 |
2015-08-23 | Melnikov chaos in a modified Rayleigh-Duffing oscillator with $ φ^6$ potential | The chaotic behavior of the modified Rayleigh-Duffing oscillator with $
\phi^6$ potential and external excitation which modeles ship rolling motions
are investigated both analytically and numerically. Melnikov method is applied
and the conditions for the existence of homoclinic and heteroclinic chaos are
obtained. The effects of nonlinear damping on roll motion of ships are analyzed
in detail. As it is known, nonlinear roll damping is a very important parameter
in estimating ship reponses. The predictions are tested numerical simulations
based on the basin of attraction. We conclude that certains quadratic damping
effects are contrary to cubic damping effect. | 1508.05664v1 |
2015-09-23 | Quantum Error-Correcting Codes for Qudit Amplitude Damping | Traditional quantum error-correcting codes are designed for the depolarizing
channel modeled by generalized Pauli errors occurring with equal probability.
Amplitude damping channels model, in general, the decay process of a multilevel
atom or energy dissipation of a bosonic system at zero temperature. We discuss
quantum error-correcting codes adapted to amplitude damping channels for higher
dimensional systems (qudits). For multi-level atoms, we consider a natural kind
of decay process, and for bosonic systems,we consider the qudit amplitude
damping channel obtained by truncating the Fock basis of the bosonic modes to a
certain maximum occupation number. We construct families of
single-error-correcting quantum codes that can be used for both cases. Our
codes have larger code dimensions than the previously known
single-error-correcting codes of the same lengths. Additionally, we present
families of multi-error correcting codes for these two channels, as well as
generalizations of our construction technique to error-correcting codes for the
qutrit $V$ and $\Lambda$ channels. | 1509.06829v1 |
2015-10-09 | Determining form and data assimilation algorithm for weakly damped and driven Korteweg-de Vries equaton- Fourier modes case | We show that the global attractor of a weakly damped and driven Korteweg-de
Vries equation (KdV) is embedded in the long-time dynamics of an ordinary
differential equation called a determining form. In particular, there is a
one-to-one identification of the trajectories in the global attractor of the
damped and driven KdV and the steady state solutions of the determining form.
Moreover, we analyze a data assimilation algorithm (down-scaling) for the
weakly damped and driven KdV. We show that given a certain number of low
Fourier modes of a reference solution of the KdV equation, the algorithm
recovers the full reference solution at an exponential rate in time. | 1510.02730v1 |
2015-10-27 | Remarks on 1-D Euler Equations with Time-Decayed Damping | We study the 1-d isentropic Euler equations with time-decayed damping
\begin{equation} \left\{ \begin{aligned} &\partial_t \rho+\partial_x(\rho u)=0,
\\ &\partial_t(\rho u)+ \partial_x(\rho
u^2)+\partial_xp(\rho)=-\frac{\mu}{1+t}\rho u,\\
&\rho|_{t=0}=1+\varepsilon\rho_0(x),u|_{t=0}=\varepsilon u_0(x). \end{aligned}
\right. \nonumber \end{equation}
This work is inspired by a recent work of F. Hou, I. Witt and H.C. Yin
\cite{Hou01}. In \cite{Hou01}, they proved a global existence and blow-up
result of 3-d irrotational Euler flow with time-dependent damping. In the 1-d
case, we will prove a different result when the damping decays of order $-1$
with respect to the time $t$. More precisely, when $\mu>2$, we prove the global
existence of the 1-d Euler system. While when $0\leq\mu\leq2 $, we will prove
the blow up of $C^1$ solutions. | 1510.08115v1 |
2016-01-04 | Generalized Bloch's theorem for viscous metamaterials: Dispersion and effective properties based on frequencies and wavenumbers that are simultaneously complex | It is common for dispersion curves of damped periodic materials to be based
on real frequencies versus complex wavenumbers or, conversely, real wavenumbers
versus complex frequencies. The former condition corresponds to harmonic wave
motion where a driving frequency is prescribed and where attenuation due to
dissipation takes place only in space alongside spatial attenuation due to
Bragg scattering. The latter condition, on the other hand, relates to free wave
motion admitting attenuation due to energy loss only in time while spatial
attenuation due to Bragg scattering also takes place. Here, we develop an
algorithm for 1D systems that provides dispersion curves for damped free wave
motion based on frequencies and wavenumbers that are permitted to be
simultaneously complex. This represents a generalized application of Bloch's
theorem and produces a dispersion band structure that fully describes all
attenuation mechanisms, in space and in time. The algorithm is applied to a
viscously damped mass-in-mass metamaterial exhibiting local resonance. A
frequency-dependent effective mass for this damped infinite chain is also
obtained. | 1601.00683v1 |
2016-02-05 | Protecting entanglement from correlated amplitude damping channel using weak measurement and quantum measurement reversal | Based on the quantum technique of weak measurement, we propose a scheme to
protect the entanglement from correlated amplitude damping decoherence. In
contrast to the results of memoryless amplitude damping channel, we show that
the memory effects play a significant role in the suppression of entanglement
sudden death and protection of entanglement under severe decoherence. Moreover,
we find that the initial entanglement could be drastically amplified by the
combination of weak measurement and quantum measurement reversal even under the
correlated amplitude damping channel. The underlying mechanism can be
attributed to the probabilistic nature of weak measurements. | 1602.01998v1 |
2016-04-29 | Nonlinear Landau damping of wave envelopes in a quantum plasma | The nonlinear theory of Landau damping of electrostatic wave envelopes (WEs)
is revisited in a quantum electron-positron (EP) pair plasma. Starting from a
Wigner-Moyal equation coupled to the Poisson equation and applying the multiple
scale technique, we derive a nonlinear Schr{\"o}dinger (NLS) equation which
governs the evolution of electrostatic WEs. It is shown that the coefficients
of the NLS equation, including the nonlocal nonlinear term, which appears due
to the resonant particles having group velocity of the WEs, are significantly
modified by the particle dispersion. The effects of the quantum parameter $H$
(the ratio of the plasmon energy to the thermal energy densities), associated
with the particle dispersion, are examined on the Landau damping rate of
carrier waves, as well as on the modulational instability of WEs. It is found
that the Landau damping rate and the decay rate of the solitary wave amplitude
are greatly reduced compared to their classical values $(H=0)$. | 1604.08751v4 |
2016-05-02 | Three types of nonlinear resonances | We analyse different types of nonlinear resonances in a weakly damped Duffing
oscillator using bifurcation theory techniques. In addition to (i) odd
subharmonic resonances found on the primary branch of symmetric periodic
solutions with the forcing frequency and (ii) even subharmonic resonances due
to symmetry-broken periodic solutions that bifurcate off the primary branch and
also oscillate at the forcing frequency, we uncover (iii) novel resonance type
due to isolas of periodic solutions that are not connected to the primary
branch. These occur between odd and even resonances, oscillate at a fraction of
the forcing frequency, and give rise to a complicated resonance `curve' with
disconnected elements and high degree of multistability. We use bifurcation
continuation to compute resonance tongues in the plane of the forcing frequency
vs. the forcing amplitude for different but fixed values of the damping rate.
In this way, we demonstrate that identified here isolated resonances explain
the intriguing structure of "patchy tongues" observed for week damping and link
it to a seemingly unrelated phenomenon of "bifurcation superstructure"
described for moderate damping. | 1605.00858v2 |
2016-07-21 | The Noisy Oscillator : Random Mass and Random Damping | The problem of a linear damped noisy oscillator is treated in the presence of
two multiplicative sources of noise which imply a random mass and random
damping. The additive noise and the noise in the damping are responsible for an
influx of energy to the oscillator and its dissipation to the surrounding
environment. A random mass implies that the surrounding molecules not only
collide with the oscillator but may also adhere to it, thereby changing its
mass. We present general formulas for the first two moments and address the
question of mean and energetic stabilities. The phenomenon of stochastic
resonance, i.e. the expansion due to the noise of a system response to an
external periodic signal, is considered for separate and joint action of two
sources of noise and their characteristics. | 1607.06289v2 |
2016-09-06 | JRSP of three-particle state via three tripartite GHZ class in quantum noisy channels | We present a scheme for joint remote state preparation (JRSP) of
three-particle state via three tripartite Greenberger-Horne-Zeilinger (GHZ)
entangled states as the quantum channel linking the parties. We use eight-qubit
mutually orthogonal basis vector as measurement point of departure. The
likelihood of success for this scheme has been found to be $1/8$. However, by
putting some special cases into consideration, the chances can be ameliorated
to $1/4$ and $1$. The effects of amplitude-damping noise, phase-damping noise
and depolarizing noise on this scheme have been scrutinized and the analytical
derivations of fidelities for the quantum noisy channels have been presented.
We found that for $0.55\leq\eta\leq1$, the states conveyed through depolarizing
channel lose more information than phase-damping channel while the information
loss through amplitude damping channel is most minimal. | 1609.01538v3 |
2016-09-22 | Damping of nonlinear standing kink oscillations: a numerical study | We aim to study the standing fundamental kink mode of coronal loops in the
nonlinear regime, investigating the changes in energy evolution in the
cross-section and oscillation amplitude of the loop which are related to
nonlinear effects, in particular to the development of the Kelvin-Helmholtz
instability (KHI). We run idea, high-resolution three-dimensional (3D)
magnetohydrodynamics (MHD) simulations, studying the influence of the initial
velocity amplitude and the inhomogeneous layer thickness. We model the coronal
loop as a straight, homogeneous magnetic flux tube with an outer inhomogeneous
layer, embedded in a straight, homogeneous magnetic field. We find that, for
low amplitudes which do not allow for the KHI to develop during the simulated
time, the damping time agrees with the theory of resonant absorption. However,
for higher amplitudes, the presence of KHI around the oscillating loop can
alter the loop's evolution, resulting in a significantly faster damping than
predicted by the linear theory in some cases. This questions the accuracy of
seismological methods applied to observed damping profiles, based on linear
theory. | 1609.06883v1 |
2016-09-28 | Nonlinear damping and dephasing in nanomechanical systems | We present a microscopic theory of nonlinear damping and dephasing of
low-frequency eigenmodes in nano- and micro-mechanical systems. The mechanism
of the both effects is scattering of thermally excited vibrational modes off
the considered eigenmode. The scattering is accompanied by energy transfer of
$2\hbar\omega_0$ for nonlinear damping and is quasieleastic for dephasing. We
develop a formalism that allows studying both spatially uniform systems and
systems with a strong nonuniformity, which is smooth on the typical wavelength
of thermal modes but not their mean free path. The formalism accounts for the
decay of thermal modes, which plays a major role in the nonlinear damping and
dephasing. We identify the nonlinear analogs of the Landau-Rumer,
thermoelastic, and Akhiezer mechanisms and find the dependence of the
relaxation parameters on the temperature and the geometry of a system. | 1609.08714v1 |
2016-09-24 | Parametric Landau damping of space charge modes | Landau damping is the mechanism of plasma and beam stabilization; it arises
through energy transfer from collective modes to the incoherent motion of
resonant particles. Normally this resonance requires the resonant particle's
frequency to match the collective mode frequency. We have identified an
important new damping mechanism, {\it parametric Landau damping}, which is
driven by the modulation of the mode-particle interaction. This reveals new
possibilities for stability control through manipulation of both particle and
mode-particle coupling spectra. We demonstrate the existence of parametric
Landau damping in a simulation of transverse coherent modes of bunched
accelerator beams with space charge. | 1609.09393v3 |
2017-01-08 | Decentralized Robust Control for Damping Inter-area Oscillations in Power Systems | As power systems become more and more interconnected, the inter-area
oscillations has become a serious factor limiting large power transfer among
different areas. Underdamped (Undamped) inter-area oscillations may cause
system breakup and even lead to large-scale blackout. Traditional damping
controllers include Power System Stabilizer (PSS) and Flexible AC Transmission
System (FACTS) controller, which adds additional damping to the inter-area
oscillation modes by affecting the real power in an indirect manner. However,
the effectiveness of these controllers is restricted to the neighborhood of a
prescribed set of operating conditions. In this paper, decentralized robust
controllers are developed to improve the damping ratios of the inter-area
oscillation modes by directly affecting the real power through the turbine
governing system. The proposed control strategy requires only local signals and
is robust to the variations in operation condition and system topology. The
effectiveness of the proposed robust controllers is illustrated by detailed
case studies on two different test systems. | 1701.02036v1 |
2017-01-18 | Ion beam test results of the Plastic Scintillator Detector of DAMPE | The DArk Matter Particle Explorer (DAMPE) is one of the four satellites
within Strategic Pioneer Research Program in Space Science of the Chinese
Academy of Science (CAS). DAMPE can detect electrons, photons and ions in a
wide energy range (5 GeV to 10 TeV) and ions up to iron (100GeV to 100 TeV).
Plastic Scintillator Detector (PSD) is one of the four payloads in DAMPE,
providing e/{\gamma} separation and charge identification up to Iron. An ion
beam test was carried out for the Qualification Model of PSD in CERN with
40GeV/u Argon primary beams. The Birk's saturation and charge resolution of PSD
were investigated. | 1701.04947v2 |
2017-01-18 | DAMPE space mission: first data | The DAMPE (DArk Matter Particle Explorer) satellite was launched on December
17, 2015 and started its data taking operation a few days later.
DAMPE has a large geometric factor ($\sim~0.3\ m^2\ sr$) and provides good
tracking, calorimetric and charge measurements for electrons, gammas rays and
nuclei. This will allow precise measurement of cosmic ray spectra from tens of
$GeV$ up to about $100\ TeV$. In particular, the energy region between $1-100\
TeV$ will be explored with higher precision compared to previous experiments.
The various subdetectors allow an efficient identification of the electron
signal over the large (mainly proton-induced) background. As a result, the
all-electron spectrum will be measured with excellent resolution from few $GeV$
up to few $TeV$, thus giving the opportunity to identify possible contribution
of nearby sources. A report on the mission goals and status is presented,
together with the on-orbit detector performance and the first data coming from
space. | 1701.05046v1 |
2017-01-25 | Control Allocation for Wide Area Coordinated Damping | In this work, a modal-based sparse control allocation (CA) is proposed for
coordinated and fault-tolerant wide-area damping controllers (WADCs). In our
proposed method, the supervisory CA only communicates with necessary actuators
to achieve the required damping performance and in case of actuator failures
(e.g., due to loss of communication or scheduling), capabilities of the
remaining actuators are fully used before the nominal performance is degraded.
This method offers the advantages of modular design where WADC is initially
designed to achieve satisfactory damping without the detailed knowledge of
actuators. In the next step, CA is designed to manage actuator failures and
limitations without the need to redesign the nominal WADC. The proposed
approach is applied to a modified $286$-bus Western Electricity Coordinating
Council (WECC) system to verify the feasibility on a complex power system.
Simulation results indicate the effectiveness of the proposed method in
coordinating multiple actuators and building resiliency. | 1701.07456v1 |
2017-04-30 | Comparison of dynamic mechanical properties of non-superheated and superheated A357 alloys | The influence of superheat treatment on the microstructure and dynamic
mechanical properties of A357 alloys has been investigated. The study of
microstructure was performed by the optical microscope. Dynamic mechanical
properties (storage modulus, loss modulus, and damping capacity) were measured
by the dynamic mechanical analyzer (DMA). Microstructure showed coarser and
angular eutectic Si particles with larger {\alpha}-Al dendrites in the
non-superheated A357 alloy. In contrast, finer and rounded eutectic Si
particles together with smaller and preferred oriented {\alpha}-Al dendrites
have been observed in the superheated A357 alloy. Dynamic mechanical properties
showed an increasing trend of loss modulus and damping capacity meanwhile a
decreasing trend of storage modulus at elevated temperatures for superheated
and non-superheated A357 alloys. The high damping capacity of superheated A357
has been ascribed to the grain boundary damping at elevated temperatures. | 1705.00350v1 |
2017-05-19 | Improving two - qubit state teleportation affected by amplitude damping noise based on choosing appropriate quantum channel | We consider two qubit teleportation via quantum channel affected by amplitude
damping noise. Addressing the same problem, X. Hu, Y. Gu, Q. Gong and G. Guo
[Phys. Rev. A 81, 054302, (2010)] recently showed that in presence of noise,
subjecting more qubits in quantum channel to amplitude damping can increase the
fidelity of teleportation protocol. However, in this paper, by making some
adjustments on quantum channel, we obtain teleportation fidelity which is even
higher than one in the case of X. Hu et al. Moreover, our strategy is simpler
than quantum distillation and compared to using weak measurement, it is
deterministic. Furthermore, explicit analysis of fidelity is provided, we show
that in general, choosing appropriate quantum channel enhances the ability of
teleportation better and negates the fact that more amplitude damping noise
more quality. | 1705.07064v2 |
2017-05-27 | Charge reconstruction study of the DAMPE Silicon-Tungsten Tracker with ion beams | The DArk Matter Particle Explorer (DAMPE) is one of the four satellites
within Strategic Pioneer Research Program in Space Science of the Chinese
Academy of Science (CAS). DAMPE can detect electrons, photons in a wide energy
range (5 GeV to 10 TeV) and ions up to iron (100GeV to 100 TeV).
Silicon-Tungsten Tracker (STK) is one of the four subdetectors in DAMPE,
providing photon-electron conversion, track reconstruction and charge
identification for ions. Ion beam test was carried out in CERN with 60GeV/u
Lead primary beams. Charge reconstruction and charge resolution of STK
detectors were investigated. | 1705.09791v1 |
2017-08-05 | Dynamic Sensitivity Study of MEMS Capacitive Acceleration Transducer Based on Analytical Squeeze Film Damping and Mechanical Thermoelasticity Approaches | The dynamic behavior of a capacitive micro-electro-mechanical (MEMS)
accelerometer is evaluated by using a theoretical approach which makes use of a
squeeze film damping (SFD) model and ideal gas approach. The study investigates
the performance of the device as a function of the temperature, from 228 K to
398 K, and pressure, from 20 to 1000 Pa, observing the damping gas trapped
inside de mechanical transducer. Thermoelastic properties of the silicon bulk
are considered for the entire range of temperature. The damping gases
considered are Air, Helium and Argon. The global behavior of the system is
evaluated considering the electro-mechanical sensitivity (SEM) as the main
figure of merit in frequency domain. The results show the behavior of the main
mechanism losses of SFD, as well as the dynamic sensitivity of the MEMS
transducer system, and are in good agreement with experimental dynamic results
behavior. | 1708.01812v1 |
2017-10-09 | Time-dependent propagation speed vs strong damping for degenerate linear hyperbolic equations | We consider a degenerate abstract wave equation with a time-dependent
propagation speed. We investigate the influence of a strong dissipation, namely
a friction term that depends on a power of the elastic operator.
We discover a threshold effect. If the propagation speed is regular enough,
then the damping prevails, and therefore the initial value problem is
well-posed in Sobolev spaces. Solutions also exhibit a regularizing effect
analogous to parabolic problems. As expected, the stronger is the damping, the
lower is the required regularity.
On the contrary, if the propagation speed is not regular enough, there are
examples where the damping is ineffective, and the dissipative equation behaves
as the non-dissipative one. | 1710.03602v1 |
2017-10-17 | Entropic uncertainty relation under quantum channels with memory | Recently, Xu et al. [Phys. Rev. A 86, 012113(2012)] explored the behavior of
the entropic uncertainty relation under the influence of local unital and
nonunital noisy channels for a class of Bell-diagonal states. We here reform
their results and investigate the entropic uncertainty relation under the
influence of unital and nonunital noisy channels with memory. Different types
of noisy channels with memory, such as amplitude damping channel(nonunitary),
phase-damping and depolarizing channels(unitary) have been taken into account.
Some analytical or numerical results are presented. The effect of channels with
memory on dynamics of the entropic uncertainties (or their lower bounds) has
been discussed in detail. Compare with previous results, our results show that,
the entropic uncertainties (or their lower bounds) subjecting to amplitude
damping channel with memory will be reduced at first and then be lifted with
the memory coefficient of channel $\mu$ increasing, however they will be only
reduced under phase-damping and depolarizing channels with memory. Especially,
in the limit of $\mu\rightarrow1$, the entropic uncertainties (or their lower
bounds) could be well protected and immune to decoherence of channle. Moreover,
the mechanism behind these phenomena are also explored by using the purity of
state. | 1710.06344v1 |
2017-10-31 | Improving mechanical sensor performance through larger damping | Mechanical resonances are used in a wide variety of devices; from smart phone
accelerometers to computer clocks and from wireless communication filters to
atomic force microscope sensors. Frequency stability, a critical performance
metric, is generally assumed to be tantamount to resonance quality factor (the
inverse of the linewidth and of the damping). Here we show that frequency
stability of resonant nanomechanical sensors can generally be made independent
of quality factor. At high bandwidths, we show that quality factor reduction is
completely mitigated by increases in signal to noise ratio. At low bandwidths,
strikingly, increased damping leads to better stability and sensor resolution,
with improvement proportional to damping. We confirm the findings by
demonstrating temperature resolution of 50 \mu K at 200 Hz bandwidth. These
results open the door for high performance ultrasensitive resonant sensors in
gaseous or liquid environments, single cell nanocalorimetry, nanoscale gas
chromatography, and atmospheric pressure nanoscale mass spectrometry. | 1710.11280v1 |
2017-11-30 | The electron-flavored Z'-portal dark matter and the DAMPE cosmic ray excess | The DAMPE experiment has recently reported strong indications for the
existence of an excess of high-energy electrons and positrons. If interpreted
in terms of the annihilation of dark matter, the DAMPE result restricts the
dark matter mass and possible annihilation channels to a few case. In this
paper we explain the DAMPE result with the electron-flavored $Z^\prime$-portal
fermionic dark matter. We show that the Dirac dark matter scenario is promising
to explain the excess via the process $\bar \chi \chi \to\mathbf{Z}'\to \bar e
e$. The reduced annihilation cross section is limited in a range of
$10^{-26}\sim 10^{-24}~{\rm cm^3 s^{-1}}$ to interpret the excess. | 1711.11182v2 |
2018-04-15 | Reevaluation of radiation reaction and consequences for light-matter interactions at the nanoscale | In the context of electromagnetism and nonlinear optical interactions damping
is generally introduced as a phenomenological, viscous term that dissipates
energy, proportional to the temporal derivative of the polarization. Here, we
follow the radiation reaction method presented in [G. W. Ford and R. F.
O'Connell, Phys. Lett. A, 157, 217 (1991)], which applies to non-relativistic
electrons of finite size, to introduce an explicit reaction force in the
Newtonian equation of motion, and derive a hydrodynamic equation that offers
new insight on the influence of damping in generic plasmas, metal-based and/or
dielectric structures. In these settings, we find new damping-dependent linear
and nonlinear source terms that suggest the damping coefficient is proportional
to the local charge density, and nonlocal contributions that stem from the
spatial derivative of the magnetic field and discuss the conditions that could
modify both linear and nonlinear electromagnetic responses. | 1804.05369v1 |
2018-04-30 | Wave-like blow-up for semilinear wave equations with scattering damping and negative mass term | In this paper we establish blow-up results and lifespan estimates for
semilinear wave equations with scattering damping and negative mass term for
subcritical power, which is the same as that of the corresponding problem
without mass term, and also the same as that of the corresponding problem
without both damping and mass term. For this purpose, we have to use the
comparison argument twice, due to the damping and mass term, in additional to a
key multiplier. Finally, we get the desired results by an iteration argument. | 1804.11073v3 |
2018-06-01 | Fluctuation-damping of isolated, oscillating Bose-Einstein condensates | Experiments on the nonequilibrium dynamics of an isolated Bose-Einstein
condensate (BEC) in a magnetic double-well trap exhibit a puzzling divergence:
While some show dissipation-free Josephson oscillations, others find strong
damping. Such damping in isolated BECs cannot be understood on the level of the
coherent Gross-Pitaevskii dynamics. Using the Keldysh functional-integral
formalism, we describe the time-dependent system dynamics by means of a
multi-mode BEC coupled to fluctuations (single-particle excitations) beyond the
Gross-Pitaevskii saddle point. We find that the Josephson oscillations excite
an excess of fluctuations when the effective Josephson frequency,
$\tilde{\omega}_J$, is in resonance with the effective fluctuation energy,
$\tilde{\varepsilon}_m$, where both, $\tilde{\omega}_J$ and
$\tilde{\varepsilon}_m$, are strongly renormalized with respect to their
noninteracting values. Evaluating and using the model parameters for the
respective experiments describes quantitatively the presence or absence of
damping. | 1806.00376v2 |
2018-06-05 | Decoherence assisted spin squeezing generation in superposition of tripartite GHZ and W states | In the present paper, we study spin squeezing under decoherence in the
superposition of tripartite maximally entangled GHZ and W states. Here we use
amplitude damping, phase damping and depolarisation channel. We have
investigated the dynamics of spin squeezing with the interplay of superposition
and decoherence parameters with different directions of the mean spin vector.
We have found the mixture of GHZ and W states is robust against spin squeezing
generation for amplitude damping and phase damping channels for certain
directions of the mean spin vector. However, the depolarisation channel
performs well for spin squeezing generation and generates permanent spin
squeezing in the superposition of GHZ and W states. | 1806.01730v1 |
2018-07-31 | Dark Matter Particle Explorer observations of high-energy cosmic ray electrons plus positrons and their physical implications | The DArk Matter Particle Explorer (DAMPE) is a satellite-borne, high-energy
particle and $\gamma$-ray detector, which is dedicated to indirectly detecting
particle dark matter and studying high-energy astrophysics. The first results
about precise measurement of the cosmic ray electron plus positron spectrum
between 25 GeV and 4.6 TeV were published recently. The DAMPE spectrum reveals
an interesting spectral softening around $0.9$ TeV and a tentative peak around
$1.4$ TeV. These results have inspired extensive discussion. The detector of
DAMPE, the data analysis, and the first results are introduced. In particular,
the physical interpretations of the DAMPE data are reviewed. | 1807.11638v1 |
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