ZWG817/Abstract · Datasets at Hugging Face

publicationDate stringlengths 1 2.79k	title stringlengths 1 36.5k ⌀	abstract stringlengths 1 37.3k ⌀	id stringlengths 9 47
2003-11-06	Perturbation-induced radiation by the Ablowitz-Ladik soliton	An efficient formalism is elaborated to analytically describe dynamics of the Ablowitz-Ladik soliton in the presence of perturbations. This formalism is based on using the Riemann-Hilbert problem and provides the means of calculating evolution of the discrete soliton parameters, as well as shape distortion and perturbation-induced radiation effects. As an example, soliton characteristics are calculated for linear damping and quintic perturbations.	0311010v1
2004-04-26	Nonlinear stability of oscillatory wave fronts in chains of coupled oscillators	We present a stability theory for kink propagation in chains of coupled oscillators and a new algorithm for the numerical study of kink dynamics. The numerical solutions are computed using an equivalent integral equation instead of a system of differential equations. This avoids uncertainty about the impact of artificial boundary conditions and discretization in time. Stability results also follow from the integral version. Stable kinks have a monotone leading edge and move with a velocity larger than a critical value which depends on the damping strength.	0404044v1
2004-10-15	Comment on "Soliton ratchets induced by excitation of internal modes"	Very recently Willis et al. [Phys. Rev. E {\bf 69}, 056612 (2004)] have used a collective variable theory to explain the appearance of a nonzero energy current in an ac driven, damped sine-Gordon equation. In this comment, we prove rigorously that the time-averaged energy current in an ac driven nonlinear Klein-Gordon system is strictly zero.	0410021v1
2005-02-25	A kinetic approach to Bose-Einstein condensates: self-phase modulation and Bogoliubov oscillations	A kinetic approach to the Bose-Einstein condensates (BECs) is proposed, based on the Wigner-Moyal equation (WME). In the quasi-classical limit, the WME reduces to the particle number conservation equation. Two examples of application are: i) a self-phase modulation of a BE condensate beam where we show that part of the beam is decelerated and eventually stops as a result of the gradient of the effective self-potential; ii) the derivation of a kinetic dispersion relation for sound waves in the BECs, including a collisionless Landau damping.	0502059v1
2006-01-14	Chaotic Vibration of a Quarter-Car Model Excited by the Road Surface Profile	The Melnikov criterion is used to examine a global homoclinic bifurcation and transition to chaos in the case of a quarter car model excited kinematically by the road surface profile. By analyzing the potential an analytic expression is found for the homoclinic orbit. By introducing an harmonic excitation term and damping as perturbations, the critical Melnikov amplitude of the road surface profile is found, above which the system can vibrate chaotically.	0601030v1
2006-01-14	Transition to Chaos in the Self-Excited System with a Cubic Double Well Potential and Parametric Forcing	We examine the Melnikov criterion for a global homoclinic bifurcation and a possible transition to chaos in case of a single degree of freedom nonlinear oscillator with a symmetric double well nonlinear potential. The system was subjected simultaneously to parametric periodic forcing and self excitation via negative damping term. Detailed numerical studies confirm the analytical predictions and show that transitions from regular to chaotic types of motion are often associated with increasing the energy of an oscillator and its escape from a single well.	0601032v1
2006-07-19	Energy flux fluctuations in a finite volume of turbulent flow	The flux of turbulent kinetic energy from large to small spatial scales is measured in a small domain B of varying size R. The probability distribution function of the flux is obtained using a time-local version of Kolmogorov's four-fifths law. The measurements, made at a moderate Reynolds number, show frequent events where the flux is backscattered from small to large scales, their frequency increasing as R is decreased. The observations are corroborated by a numerical simulation based on the motion of many particles and on an explicit form of the eddy damping.	0607044v1
2006-08-09	Statistical properties of the continuum Salerno model	The statistical properties of the Salerno model is investigated. In particular, a comparison between the coherent and partially coherent wave modes is made for the case of a random phased wave packet. It is found that the random phased induced spectral broadening gives rise to damping of instabilities, but also a broadening of the instability region in quasi-particle momentum space. The results can be of significance for condensation of magnetic moment bosons in deep optical lattices.	0608016v1
2006-10-18	Whitham method for Benjamin-Ono-Burgers equation and dispersive shocks in internal waves in deep fluid	The Whitham modulation equations for the parameters of a periodic solution are derived using the generalized Lagrangian approach for the case of damped Benjamin-Ono equation. The structure of the dispersive shock in internal wave in deep water is considered by this method.	0610039v1
2007-03-28	Quasi-Patterns in a Model of Multi-Resonantly Forced Chemical Oscillations	Multi-frequency forcing of systems undergoing a Hopf bifurcation to spatially homogeneous oscillations is investigated using a complex Ginzburg-Landau equation that systematically captures weak forcing functions that simultaneously hit the 1:1-, the 1:2-, and the 1:3-resonance. Weakly nonlinear analysis shows that generically the forcing function can be tuned such that resonant triad interactions with weakly damped modes stabilize subharmonic quasipatterns with 4-fold and 5-fold rotational symmetry. In simulations starting from random initial conditions domains of these quasi-patterns compete and yield complex, slowly ordering patterns.	0703059v1
2001-06-09	Conditions for Isoscaling in Nuclear Reactions	Isoscaling, where ratios of isotopes emitted from two reactions exhibit an exponential dependence on the neutron and proton number of the isotope, has been observed over a variety of reactions including evaporation, strongly damped binary collision, and multifragmentation. The conditions for isoscaling to occur as well as the conditions when isoscaling fails are investigated.	0106009v1
1992-12-25	Chaotic Behavior in Warm Deformed Nuclei Induced by Residual Two-Body Interactions	Band mixing calculations in rapidly rotating well-deformed nuclei are presented, investigating the properties of energy levels and rotational transitions as a function of excitation energy. Substantial fragmentation of E2 transitions is found for $E_x \gsim$ 800 keV above yrast, which represents the onset of rotational damping. Above $E_x \approx $ 2 MeV, energy levels and E2 strengths display fluctuations typical of quantum chaotic systems, which are determined by the high multipole components of the two-body residual interaction.	9212015v1
1993-07-07	Color Diffusion and Conductivity in a Quark-Gluon Plasma	Color diffusion is shown to be an important dissipative property of quark-gluon plasmas that rapidly damps collective color modes. We derive the characteristic color relaxation time scale, $t_c\approx (3\alpha_s T \log(m_E/m_M ))^{-1}$, showing its sensitivity to the ratio of the static color electric and magnetic screening masses. This leads to a surprisingly small color conductivity, $\sigma_c\approx 2 T/\log(m_E/m_M)$, which in fact vanishes in the semi-classical (1-loop) limit.	9307007v1
1994-04-18	Vibrations versus collisions and the iterative structure of two-body dynamics	We adopt a truncated version of two-body dynamics by neglecting three-body correlations, as is supported by microscopic numerical calculations. Introducing orthogonal channel correlations for the pp- and the ph-channel and integrating the latter in terms of vibrational RPA-states we derive a retarded two-body equation. Its solution is nonperturbative with respect to loops, ladders and mixed contributions. In the stationary limit we obtain an equation for a generalised effective interaction which iterates both the G-matrix and the polarisation matrix. An in-medium scattering approach transparently demonstrates the collisional damping of the vibrations.	9404020v1
1994-07-01	Friedel Oscillations in Relativistic Nuclear Matter	We calculate the low-momentum N-N effective potential obtained in the OBE approximation, inside a nuclear plasma at finite temperature, as described by the relativistic $ \sigma $-$ \omega $ model. We analyze the screening effects on the attractive part of the potential in the intermediate range as density or temperature increase. In the long range the potential shows Friedel-like oscillations instead of the usual exponential damping. These oscillations arise from the sharp edge of the Fermi surface and should be encountered in any realistic model of nuclear matter.	9407002v1
1995-12-19	Macroscopic Features of Light Heavy-Ion Fission Reactions	Global macroscopic features observed in the fully-damped binary processes in light di-nuclear systems, such as limiting angular momenta, mean total kinetic energies and energy thresholds for fusion-fission processes (''fission thresholds") are presented. Their deduced systematics are consistent with that obtained for heavier systems and follow a fusion-fission picture which can be described by a realistic rotating liquid drop model considering diffuse-surface and finite-nuclear-range effects.	9512025v1
1995-12-28	Classical and Quantal Irregular Scatterings with Complex Target	One-dimensional scattering by a target with two internal degrees of freedom is investigated. The damping of resonance peaks and the associated appearance of the fluctuating background in the quantum inelastic scattering amplitudes are found. Examination of the analog classical system reveals a disorderly reaction function, which is then related to the quantum amplitude through a semiclassical argument.	9512038v1
1996-03-21	Time development of a density perturbation in the unstable nuclear matter	We present the solution of the time development of an unstable initial density perturbation in the linearized Vlasov equation, completing the previous analysis in the literature. The additional contributions found are usually damped and can be neglected at large times in the unstable region. The work clarifies also the problem of the normalization of the solution with respect to the initial perturbation of the density.	9603029v2
1997-02-12	A self-consistent treatment of the dynamics of stable and unstable collective modes	We address the dynamics of damped collective modes in terms of first and second moments. The modes are introduced in a self-consistent fashion with the help of a suitable application of linear response theory. Quantum effects in the fluctuations are governed by diffusion coefficients D_{\mu\nu}. The latter are obtained through a fluctuation dissipation theorem generalized to allow for a treatment of unstable modes. Numerical evaluations of the D_{\mu\nu} are presented. We discuss briefly how this picture may be used to describe global motion within a locally harmonic approximation.	9702029v1
1998-07-27	Isovector Vibrations in Nuclear Matter at Finite Temperature	We consider the propagation and damping of isovector excitations in heated nuclear matter within the Landau Fermi-liquid theory. Results obtained for nuclear matter are applied to calculate the Giant Dipole Resonance (GDR) at finite temperature in heavy spherical nuclei within Steinwedel and Jensen model. The centroid energy of the GDR slightly decreases with increasing temperature and the width increases as $T^2$ for temperatures $T < 5$ MeV in agreement with recent experimental data for GDR in $^{208}$Pb and $^{120}$Sn. The validity of the method for other Fermi fluids is finally suggested.	9807070v1
1998-09-03	Relaxation of fast collective motion in heated nuclei	The damping of the collective vibrations in hot nuclei is studied within the semiclassical Vlasov-Landau kinetic theory. The extention of the method of independent sources of dissipation is used to allow for irreversible energy transfer by chaos weighted wall formula. The expressions for the intrinsic width of the giant multipole resonances are obtained. The interplay between the one-body and the two-body channels which contribute to the formation of the intrinsic width in nuclei is discussed.	9809010v1
1998-09-04	An investigation of interplay between dissipation mechanisms in heated Fermi systems by means of radiative strength functions	A simple analytical expression for the gamma-decay strength function is derived with microcanonical ensemble for initial excited states. The approach leads to both a non-zero limit of the strength function for vanishing gamma-ray energy and a partial breakdown of Brink hypothesis. It is shown that the low energy behaviour of the gamma-decay strength functions is governed by the energy behavior of the damping width. It may provides a new tool for study of the interplay between different relaxation mechanisms of the collective excitations.	9809012v1
1998-09-11	Damping of giant resonances in asymmetric nuclear matter	The giant collective modes in asymmetric nuclear matter are investigated within a dynamic relaxation time approximation. We derive a coupled dispersion relation and show that two sources of coupling appear: (i) a coupling of isoscalar and isovector modes due to different mean-fields acting and (ii) an explicit new coupling in asymmetric matter due to collisional interaction. We show that the latter one is responsible for a new mode arising besides isovector and isoscalar modes.	9809035v1
1998-10-01	Giant Octupole Resonance Simulation	Using a pseudo-particle technique we simulate large-amplitude isoscalar giant octupole excitations in a finite nuclear system. Dependent on the initial conditions we observe either clear octupole modes or over-damped octupole modes which decay immediately into quadrupole ones. This shows clearly a behavior beyond linear response. We propose that octupole modes might be observed in central collisions of heavy ions.	9810005v3
1998-10-14	Finite Temperature Nuclear Response in Extended Random-Phase Approximation	The nuclear collective response at finite temperature is investigated for the first time in the quantum framework of the small amplitude limit of the extended TDHF approach, including a non-Markovian collision term. It is shown that the collision width satisfies a secular equation. By employing a Skyrme force, the isoscalar monopole, isovector dipole and isoscalar quadrupole excitations in $^{40}Ca$ are calculated and important quantum features are pointed out. The collisional damping due to decay into incoherent 2p-2h states is small at low temperatures but increases rapidly at higher temperatures.	9810042v1
1999-05-07	Influence of damping on the excitation of the double giant resonance	We study the effect of the spreading widths on the excitation probabilities of the double giant dipole resonance. We solve the coupled-channels equations for the excitation of the giant dipole resonance and the double giant dipole resonance. Taking Pb+Pb collisions as example, we study the resulting effect on the excitation amplitudes, and cross sections as a function of the width of the states and of the bombarding energy.	9905018v2
2000-03-15	Double giant dipole resonances in time-dependent density-matrix theory	The strength functions of the DGDRs in 16O and 40Ca are calculated using an extended version of TDHF known as the time-dependent density-matrix theory (TDDM). The calculations are done in a self-consistent manner, in which the same Skyrme force as that used for the mean-field potential is used as the residual interaction to calculate two-body correlations. It is found that the DGDR in 16O has a large width due to the Landau damping, although the centroid energy of the DGDR is close to twice the energy of the GDR calculated in RPA. The DGDR in 40Ca is found more harmonic than that in 16O.	0003034v2
2001-06-28	Description of Double Giant Dipole Resonance within the Phonon Damping Model	In a recent Letter [1] an overall agreement with the experimental data for the excitation of the single and double giant dipole resonances in relativistic heavy ion collision in 136Xe and 208Pb nuclei has been reported. We point out that this agreement is achieved by a wrong calculation of the DGDR excitation mechanism. We also argue that the agreement with the data for the widths of resonances is achieved by an unrealistically large value of a model parameter. [1] Nguyen Dinh Dang, Vuong Kim Au, and Akito Arima, Phys. Rev. Lett. 85 (2000) 1827.	0106065v1
2001-11-08	Note on the Deformed Boson Scheme in Time-Dependent Variational Method	The Holstein-Primakoff representation for the su(2)-algebra is derived in the deformed boson scheme. The following two points are discussed : (i) connection between a simple Hamiltonian and the Hamiltonian obeying the su(2)-algebra such as Lipkin model and (ii) derivation of the Hamiltonian for describing the damped and amplified motion for the su(2)-boson model.	0111029v1
2002-10-15	Non-Markovian Collision Integral in Fermi-systems	The non-Markovian collision integral is obtained on the base of the Kadanoff-Baym equations for Green functions in a form with allowance for small retardation effects. The collisional relaxation times and damping width of the giant isovector dipole resonances in nuclear matter are calculated. For an infinite Fermi liquid the dependence of the relaxation times on the collective vibration frequency and the temperature corresponds to the Landau's prescription.	0210046v1
2003-04-07	Mean first passage time for fission potentials having structure	A schematic model of over-damped motion is presented which permits one to calculate the mean first passage time for nuclear fission. Its asymptotic value may exceed considerably the lifetime suggested by Kramers rate formula, which applies only to very special, favorable potentials and temperatures. The additional time obtained in the more general case is seen to allow for a considerable increment in the emission of light particles.	0304022v1
2003-09-05	Pairing effect on the giant dipole resonance width at low temperature	The width of the giant dipole resonance (GDR) at finite temperature T in Sn-120 is calculated within the Phonon Damping Model including the neutron thermal pairing gap determined from the modified BCS theory. It is shown that the effect of thermal pairing causes a smaller GDR width at T below 2 MeV as compared to the one obtained neglecting pairing. This improves significantly the agreement between theory and experiment including the most recent data point at T = 1 MeV.	0309010v1
2003-12-19	Response in the continuum for light deformed neutron-rich nuclei	The time-dependent Hartree-Fock calculation with a full Skyrme energy functional has been carried out on the three-dimensional Cartesian lattice space to study E1 giant dipole resonances (GDR) in light nuclei. The outgoing boundary condition for the continuum states is treated by the absorbing complex potential. The calculation for GDR in O-16 suggests a significant influence of the residual interaction associated with time-odd densities in the Skyrme functional. We also predict a large damping for superdeformed Be-14 at the neutron drip line.	0312089v1
2004-11-18	Nuclear giant resonances	This talk presents the recent status of theoretical and experimental studies of giant resonances in nuclei with the emphasis on: (1) charge-exchange Gamow-Teller resonance, (2) multiple-phonon resoanances, (3) giant dipole resonances in highly excited nuclei, and (4) pygmy dipole resonances in neutron rich nuclei. In particular, the description of these resonances within the framework of the phonon damping model is discussed in detail.	0411073v1
1996-06-04	Direct Hopf Bifurcation in Parametric Resonance of Hybridized Waves	We study parametric resonance of interacting waves having the same wave vector and frequency. In addition to the well-known period-doubling instability we show that under certain conditions the instability is caused by a Hopf bifurcation leading to quasiperiodic traveling waves. It occurs, for example, if the group velocities of both waves have different signs and the damping is weak. The dynamics above the threshold is briefly discussed. Examples concerning ferromagnetic spin waves and surface waves of ferro fluids are discussed.	9605006v1
1999-05-27	Impurity-induced stabilization of solitons in arrays of parametrically driven nonlinear oscillators	Chains of parametrically driven, damped pendula are known to support soliton-like clusters of in-phase motion which become unstable and seed spatiotemporal chaos for sufficiently large driving amplitudes. We show that the pinning of the soliton on a "long" impurity (a longer pendulum) expands dramatically its stability region whereas "short" defects simply repel solitons producing effective partition of the chain. We also show that defects may spontaneously nucleate solitons.	9905009v1
1999-11-19	Origin of Multikinks in Dispersive Nonlinear Systems	We develop {\em the first analytical theory of multikinks} for strongly {\em dispersive nonlinear systems}, considering the examples of the weakly discrete sine-Gordon model and the generalized Frenkel-Kontorova model with a piecewise parabolic potential. We reveal that there are no $2\pi$-kinks for this model, but there exist {\em discrete sets} of $2\pi N$-kinks for all N>1. We also show their bifurcation structure in driven damped systems.	9911006v1
1998-02-04	The steady state of a pumped and damped atom laser	This paper has been withdrawn, as further work has shown that an atom laser as described by the model herein does not have a steady state, so it doesn't matter much what it would look like.	9802008v2
1998-02-20	Phase Dynamics of Bose-Einstein Condensates: Losses versus Revivals	In the absence of losses the phase of a Bose-Einstein condensate undergoes collapses and revivals in time due to elastic atomic interactions. As experiments necessarily involve inelastic collisions, we develop a model to describe the phase dynamics of the condensates in presence of collisional losses. We find that a few inelastic processes are sufficient to damp the revivals of the phase. For this reason the observability of phase revivals for present experimental conditions is limited to condensates with a few hundreds of atoms.	9802040v1
1998-02-25	Radiation Reaction fields for an accelerated dipole for scalar and electromagnetic radiation	The radiation reaction fields are calculated for an accelerated changing dipole in scalar and electromagnetic radiation fields. The acceleration reaction is shown to alter the damping of a time varying dipole in the EM case, but not the scalar case. In the EM case, the dipole radiation reaction field can exert a force on an accelerated monopole charge associated with the accelerated dipole. The radiation reaction of an accelerated charge does not exert a torque on an accelerated magnetic dipole, but an accelerated dipole does exert a force on the charge. The technique used is that originally developed by Penrose for non-singular fields and extended by the author for an accelerated monopole charge.	9802047v1
1998-03-27	Semiclassical spin damping: Superradiance revisited	A well known description of superradiance from pointlike collections of many atoms involves the dissipative motion of a large spin. The pertinent ``superradiance master equation'' allows for a formally exact solution which we subject to a semiclassical evaluation. The clue is a saddle-point approximation for an inverse Laplace transform. All previous approximate treatments, disparate as they may appear, are encompassed in our systematic formulation. A byproduct is a hitherto unknown rigorous relation between coherences and probabilities. Our results allow for generalizations to spin dynamics with chaos in the classical limit.	9803041v1
1999-12-24	Differential criterion of a bubble collapse in viscous liquids	The present work is devoted to a model of bubble collapse in a Newtonian viscous liquid caused by an initial bubble wall motion. The obtained bubble dynamics described by an analytic solution significantly depends on the liquid and bubble parameters. The theory gives two types of bubble behavior: collapse and viscous damping. This results in a general collapse condition proposed as the sufficient differential criterion. The suggested criterion is discussed and successfully applied to the analysis of the void and gas bubble collapses.	9912050v1
1999-12-27	Rutherford Scattering with Retardation	Numerical solutions for Sommerfeld model in nonrelativistic case are presented for the scattering of a spinless extended charged body in a static Coulomb field of a fixed point charge. It is shown that differential cross section for extended body preserves the form of the Rutherford result with multiplier, not equal to one (as in classical case), but depending on the size of Sommerfeld particle. Also the effect of capture by attractive center is found out for Sommerfeld particle. The origin of this effect lies in radiation damping.	9912051v2
2000-08-04	A Variational Approach in the Dissipative Nonlinear Schrödinger Equation	The properties of pulse propagation in a nonlinear fiber including linear damped term added in the usual nonlinear Schr\"odinger equation is analyzed analytically. We apply variational modified approach based on the lagrangian that describe the dynamic of system and with a trial function we obtain a solution which is more accuracy when compared with a pertubative solution. As a result, the problem of pulse propagation in a fiber with loss can be described in good agreement with exact results.	0008011v1
2000-12-21	Intrabeam Scattering Analysis of ATF Beam Data Taken in April 2000	In April 2000 the single bunch energy spread, bunch length, horizontal emittance, and vertical emittance were measured as functions of current in KEK's ATF damping ring. In this report the measurement results are analyzed in light of intrabeam scattering theory. The measurements are found to be relatively consistent with theory, although the measured effects appear to be stronger than theory. In addition, the factor of 3 growth in vertical emittance at a current of 3 mA does not seem to be supported.	0012055v1
2001-03-09	Trapping oscillations, discrete particle effects and kinetic theory of collisionless plasma	Effects induced by the finite number $N$ of particles on the evolution of a monochromatic electrostatic perturbation in a collisionless plasma are investigated. For growth as well as damping of a single wave, discrete particle numerical simulations show a $N$-dependent long time behavior which differs from the numerical errors incurred by vlasovian approaches and follows from the pulsating separatrix crossing dynamics of individual particles.	0103025v1
2001-05-30	Impedance Analysis of Bunch Length Measurements at the ATF Damping Ring	We present energy spread and bunch length measurements at the Accelerator Test Facility (ATF) at KEK, as functions of current, for different ring rf voltages, and with the beam both on and off the coupling resonance. We fit the on-coupling bunch shapes to those of an impedance model consisting of a resistor and an inductor connected in series. We find that the fits are reasonably good, but that the resulting impedance is unexpectedly large.	0105102v1
2001-12-14	Active Vibration Suppression R&D for the NLC	The nanometer scale beam sizes at the interaction point in linear colliders limit the allowable motion of the final focus magnets. We have constructed a prototype system to investigate the use of active vibration damping to control magnet motion. Inertial sensors are used to measure the position of a test mass, and a DSP based system provides feedback using electrostatic pushers. Simulation and experimental results for the control of a mechanically simple system are presented.	0112042v1
2002-04-15	Laser-Generated Ultrashort Multi-Megagauss Magnetic Pulses in Plasmas	We demonstrate ultrashort (6 ps), multi-Megagauss (27 MG) magnetic pulses generated upon interaction of an intense laser pulse (10^{16} Wcm^-2, 100 fs) with a solid target. The temporal evolution of these giant fields generated near the high density critical layer is obtained with the highest resolution reported so far. Particle-in-cell simulations and phenomenological modeling is used to explain the results. The first direct observations of anomalously rapid damping of plasma shielding currents produced in response to the hot electron currents penetrating the bulk plasma are presented.	0204039v1
2002-04-29	Neutral Plasma Oscillations at Zero Temperature	We use cold plasma theory to calculate the response of an ultracold neutral plasma to an applied rf field. The free oscillation of the system has a continuous spectrum and an associated damped quasimode. We show that this quasimode dominates the driven response. We use this model to simulate plasma oscillations in an expanding ultracold neutral plasma, providing insights into the assumptions used to interpret experimental data [Phys. Rev. Lett. 85, 318 (2000)].	0204084v1
2002-09-04	Vortex Ring Reconnections	We investigate numerically the Navier-Stokes dynamics of reconnecting vortex rings at small $Re$ number. We find that reconnections are dissipative due to the smoothing of vorticity gradients at reconnection kinks and to the formation of secondary structures of stretched anti-parallel vorticity which transfer kinetic energy to small scales where it is subsequently dissipated efficiently. In addition, the relaxation of the reconnection kinks excites Kelvin waves which due to strong damping are of low wavenumber and affect directly only large scale properties of the flow.	0209014v1
2002-11-05	Analise Termodinamica da aceleracao de uma massa	We analyse the acceleration of a mass with a simple structure taking into account Thermodynamics. Two situations are analysed. The first one for the application of a localized force to a point of the mass. The second one for the application of a force to the entire mass. The two situations are not equivalent. For the first situation we have an increase of temperature of the mass, resulting from an internal damping, during a transient.	0211021v1
2003-05-30	A Sum Rule for Nonlinear Optical Susceptibilities	It is explicitly shown, for optical processes arbitrarily comprising two-, three- or four-photon interactions, that the sum over all matter states of any optical susceptibility is exactly zero. The result remains true even in frequency regions where damping is prominent. Using a quantum electrodynamical framework to render the photonic nature of the fundamental interactions, the result emerges in the form of a traceless operator in Hilbert space. The generality of the sum rule and its significance as a thermodynamic limit are discussed, and the applicability to real systems is assessed.	0305131v1
2003-10-16	Ionization of clusters in intense laser pulses through collective electron dynamics	The motion of electrons and ions in medium-sized rare gas clusters (1000 atoms) exposed to intense laser pulses is studied microscopically by means of classical molecular dynamics using a hierarchical tree code. Pulse parameters for optimum ionization are found to be wavelength dependent. This resonant behavior is traced back to a collective electron oscillation inside the charged cluster. It is shown that this dynamics can be well described by a driven and damped harmonic oscillator allowing for a clear discrimination against other energy absorption mechanisms.	0310073v1
2003-11-14	Transverse modulational instability of partially incoherent soliton stripes	Based on the Wigner distribution approach, an analysis of the effect of partial incoherence on the transverse instability of soliton structures in nonlinear Kerr media is presented. It is explicitly shown, that for a Lorentzian incoherence spectrum the partial incoherence gives rise to a damping which counteracts, and tends to suppress, the transverse instability growth. However, the general picture is more complicated and it is shown that the effect of the partial incoherence depends crucially on the form of the incoherence spectrum. In fact, for spectra with finite rms-width, the partial incoherence may even increase both the growth rate and the range of unstable, transverse wave numbers.	0311068v1
2004-02-13	Ion energy balance during fast wave heating in TORE SUPRA	Direct coupling of the fast magnetosonic wave to the electrons has been studied on the tokamak TORE SUPRA. Preliminary experiments were dedicated to optimise the scenario for Fast Wave Electron Heating (FWEH) and Current Drive (FWCD). In a first part, thermal kinetic and diamagnetic energy are compared when fast wave is applied to the plasma in two different regimes: 1/ the minority hydrogen heating scenario (ICRH), 2/ the direct electron damping. Effects of ion resonant layers, marginally present in the plasma in the later regime (FWEH), is then presented and discussed.	0402067v1
2004-04-14	Earthquakes temporal occurrence: a statistical study	The distribution of inter-occurrence time between seismic events is a quantity of great interest in seismic risk assessment. We evaluate this distribution for different models of earthquakes occurrence and follow two distinct approaches: The non homogeneous Poissonian and the non Poissonian one. In all cases we obtain either a power law or a power law damped by an exponential factor behaviour. This feature of the distribution makes impossible any prediction of earthquakes occurrence. Nevertheless it suggests the interpretation of the earthquake occurrence phenomenon as due to some non-linear dynamics to be further investigated.	0404068v1
2004-07-14	Exponential versus linear amplitude decay in damped oscillators	We comment of the widespread belief among some undergraduate students that the amplitude of any harmonic oscillator in the presence of any type of friction, decays exponentially in time. To dispel that notion, we compare the amplitude decay for a harmonic oscillator in the presence of (i) viscous friction and (ii) dry friction. It is shown that, in the first case, the amplitude decays exponentially with time while in the second case, it decays linearly with time.	0407080v1
2004-10-21	Kinetic effects in strong Langmuir turbulence	Kinetic effects with regard to a one dimensional Langmuir soliton-like pulse are investigated. Though thus far mainly transit-time accelerations have been investigated regarding strong Langmuir turbulence, it is found that ponderomotive reflections (generalized nonlinear Landau damping) may play important roles also. The former may diffuse fast electrons up to relativistic energies, while the latter reflects slow electrons as well as ions that have speeds comparable with the group velocity of the pulse, and tend to form flat-top electron distributions at and around the quasi-soliton.	0410179v2
2005-01-07	Velocity-Space Diffusion in a Perpendicularly Propagating Electrostatic Wave	The motion of ions in the fields B = B_0 zhat and E = E_0 yhat cos(k_perp y - omega t) is considered. When omega >> Omega_i and v_perp > omega/k_perp, the equations of motion may be reduced to a set of difference equations. These equations exhibit stochastic behavior when E_0 exceeds a threshold. The diffusion coefficient above the threshold is determined. Far above the threshold, ion Landau damping is recovered. Extension of the method to include parallel propagation is outlined.	0501035v1
2005-02-02	Swinging of two-dimensional solitons in harmonic and Bessel optical lattices	We consider parametric amplification of two-dimensional spatial soliton swinging in longitudinally modulated harmonic and Bessel lattices in Kerr-type saturable medium. We show that soliton center oscillations along different axes in two-dimensional lattices are coupled, which give rise to a number of interesting propagation scenarios including periodic damping and excitation of soliton oscillations along perpendicular axes, selective amplification of soliton swinging along one of transverse axes and enhancement of soliton spiraling.	0502009v1
2005-09-13	A Landau fluid model for warm collisionless plasmas	A Landau fluid model for a collisionless electron-proton magnetized plasma, that accurately reproduces the dispersion relation and the Landau damping rate of all the magnetohydrodynamic waves, is presented. It is obtained by an accurate closure of the hydrodynamic hierarchy at the level of the fourth order moments, based on linear kinetic theory. It retains non-gyrotropic corrections to the pressure and heat flux tensors up to the second order in the ratio between the considered frequencies and the ion cyclotron frequency.	0509091v1
2005-10-13	An illustrative experiment on electromagnetic oscillations	It is the purpose of this manuscript to place an illustrative demonstration on the measurement of damped electromagnetic oscillations for a RLC circuit that it is easy to set in any physics laboratory equipped with PASCO technologies and USB Electrical PASPort sensors together with standard electrical components. The results of recording the electrical voltage with DATA Studio software have a very good agreement with performed simulations from MULTISIM software and/or standard calculations from theory. Our students and instructors enjoy of the experiment for their simplicity set up in addition to the instructive oscillations.	0510122v1
2005-12-20	Coupled atomic-molecular condensates in a double-well potential: decaying molecular oscillations	We present a four-mode model that describes coherent photo-association (PA) in a double-well Bose-Einstein condensate, focusing on the $average$ molecular populations in certain parameters. Our numerical results predict an interesting strong-damping effect of molecular oscillations by controlling the particle tunnellings and PA light strength, which may provide a promising way for creating a stable molecular condensate via coherent PA in a magnetic double-well potential.	0512184v2
2007-02-21	Liquid-infiltrated photonic crystals: Ohmic dissipation and broadening of modes	The pronounced light-matter interactions in photonic crystals make them interesting as opto-fludic "building blocks" for lab-on-a-chip applications. We show how conducting electrolytes cause dissipation and smearing of the density-of-states, thus altering decay dynamics of excited bio-molecules dissolved in the electrolyte. Likewise, we find spatial damping of propagating modes, of the order dB/cm, for naturally occurring electrolytes such as drinking water or physiological salt water.	0702176v1
2004-04-08	Mathematical Analysis and Simulations of the Neural Circuit for Locomotion in Lamprey	We analyze the dynamics of the neural circuit of the lamprey central pattern generator (CPG). This analysis provides insights into how neural interactions form oscillators and enable spontaneous oscillations in a network of damped oscillators, which were not apparent in previous simulations or abstract phase oscillator models. We also show how the different behaviour regimes (characterized by phase and amplitude relationships between oscillators) of forward/backward swimming, and turning, can be controlled using the neural connection strengths and external inputs.	0404012v1
2005-08-11	Time Reversal of the Increasing Geometrical Progression of the Population of a Simple Biological Specie	In this work we consider time reversal of the increasing geometrical progression of the population of a simple biological species without any enemies (predators) in the appropriate environment with unlimited resources (food, territory, etc.). It is shown that such time reversal corresponds to appearance of the cannibalism, i.e. self-predaciousness or self-damping phenomena which can be described by a type of difference Verhulst equation.	0508011v1
1996-06-11	Condensate fluctuations of a trapped, ideal Bose gas	For a non-self-interacting Bose gas with a fixed, large number of particles confined to a trap, as the ground state occupation becomes macroscopic, the condensate number fluctuations remain micrscopic. However, this is the only significant aspect in which the grand canonical description differs from canonical or microcanonical in the thermodynamic limit. General arguments and estimates including some vanishingly small quantities are compared to explicit, fixed-number calculations for 10^2 to 10^6 particles.	9606009v2
1996-11-27	A precision test of decoherence	The motion of a charged particle over a conducting plate is damped by Ohmic resistance to image currents. This interaction between the particle and the plate must also produce decoherence, which can be detected by examining interference patterns made by diffracted particle beams which have passed over the plate. Because the current densities within the plate decay rapidly with the height of the particle beam above it, the strength of decoherence should be adjustable across a wide range, allowing one to probe the full range of quantum through classical behaviour.	9611049v2
1997-03-16	Least-squares inversion for density-matrix reconstruction	We propose a method for reconstruction of the density matrix from measurable time-dependent (probability) distributions of physical quantities. The applicability of the method based on least-squares inversion is - compared with other methods - very universal. It can be used to reconstruct quantum states of various systems, such as harmonic and and anharmonic oscillators including molecular vibrations in vibronic transitions and damped motion. It also enables one to take into account various specific features of experiments, such as limited sets of data and data smearing owing to limited resolution. To illustrate the method, we consider a Morse oscillator and give a comparison with other state-reconstruction methods suggested recently.	9703026v1
1997-04-02	Approximate quantum error correction can lead to better codes	We present relaxed criteria for quantum error correction which are useful when the specific dominant noise process is known. These criteria have no classical analogue. As an example, we provide a four-bit code which corrects for a single amplitude damping error. This code violates the usual Hamming bound calculated for a Pauli description of the error process, and does not fit into the GF(4) classification.	9704002v1
1997-04-08	Measured Quantum Dynamics of a Trapped Ion	The measurement process is taken into account in the dynamics of trapped ions prepared in nonclassical motional states. The induced decoherence is shown to manifest itself both in the inhibition of the internal population dynamics and in a damping of the vibrational motion without classical counterpart. Quantitative comparison with present experimental capabilities is discussed, leading to a proposal for the verification of the predicted effects.	9704016v1
1997-09-09	Quantum gravity and the problem of measurement	We discuss some arguments in favour of the proposal that the quantum correlations contained in the pure state-vector evolving according to Schoedinger equation can be eliminated by the action of multiply connected wormholes during measurement. We devise a procedure to obtain a proper master equation which governes the changes of the reduced density matrix of matter fields interacting with doubly connected wormholes. It is shown that this master equation predicts an appropriate damping of the off-diagonal correlations contained in the state vector.	9709018v1
1998-04-06	Field Oscillations in a Micromaser with Injected Atomic Coherence	The electric field in a lossless, regularly-pumped micromaser with injected atomic coherence can undergo a period 2 oscillations in the steady state. The field changes its value after a single atom passes through the micromaser cavity, but returns to its original value after a second atom travels through. We give a simple explanation for this phenomenon in terms of tangent and cotangent states. We also examine the effect of cavity damping on this steady state.	9804017v1
1998-09-14	Macroscopically distinct quantum superposition states as a bosonic code for amplitude damping	We show how macroscopically distinct quantum superposition states (Schroedinger cat states) may be used as logical qubit encodings for the correction of spontaneous emission errors. Spontaneous emission causes a bit flip error which is easily corrected by a standard error correction circuit. The method works arbitrarily well as the distance between the amplitudes of the superposed coherent states increases.	9809037v2
1998-09-27	Quantum Dynamics of Topological Singularities: Feynman's Influence Functional Approach	Starting from the microscopic theory of Bardeen-Cooper-Schrieffer (BCS) for the fermionic superfluids, we show that the vortex dynamics can be followed naturally by extending Feynman's influence functional approach to incorporate the transverse force. There is a striking mutual independence of the transverse and longitudinal influences: The former has the topological origin and is insensitive to details, while the latter corresponds to the well-known damping kernel depending on details.	9809080v1
1998-11-14	Two-atom dark states in electromagnetic cavities	The center-of-mass motion of two two-level atoms coupled to a single damped mode of an electromagnetic resonator is investigated. For the case of one atom being initially excited and the cavity mode in the vacuum state it is shown that the atomic time evolution is dominated by the appearance of dark states. These states, in which the initial excitation is stored in the internal atomic degrees of freedom and the atoms become quantum mechanically entangled, are almost immune against photon loss from the cavity. Various properties of the dark states within and beyond the Raman-Nath approximation of atom optics are worked out.	9811035v1
1998-12-17	Coherence properties of the stochastic oscillator	An oscillator with stochastic frequency is discussed as a model for evaluating the quantum coherence properties of a physical system. It is found that the choice of jump statistics has to be considered with care if unphysical consequences are to be avoided. We investigate one such model, evaluate the damping it causes, the decoherence rate and the correlations it results in and the properties of the state for asymptotically long times. Also the choice of initial state is discussed and its effect on the time evolution of the correlations.	9812045v1
1999-04-14	Quantum Langevin theory of excess noise	In an earlier work [P. J. Bardroff and S. Stenholm], we have derived a fully quantum mechanical description of excess noise in strongly damped lasers. This theory is used here to derive the corresponding quantum Langevin equations. Taking the semi-classical limit of these we are able to regain the starting point of Siegman's treatment of excess noise [Phys. Rev. A 39, 1253 (1989)]. Our results essentially constitute a quantum derivation of his theory and allow some generalizations.	9904060v1
1999-05-04	Post-Markov master equation for the dynamics of open quantum systems	A systematic first-order correction to the standard Markov master equation for open quantum systems interacting with a bosonic bath is presented. It extends the Markov Lindblad master equation to the more general case of non-Markovian evolution. The meaning and applications of our `post'-Markov master equation are illustrated with several examples, including a damped two-level atom, the spin-boson model and the quantum Brownian motion model. Limitations of the Markov approximation, the problem of positivity violation and initial slips are also discussed.	9905006v1
1999-06-18	Zeno effect preventing Rabi transitions onto an unstable energy level	We consider a driven 2-level system with one level showing spontaneous decay to an otherwise uncoupled third level. Rabi transitions to the unstable level are strongly damped. This simple configuration can be used to demonstrate and to explore the quantum Zeno effect leading to a freezing of the system to the initial level. A comparison with repeated projection measurements is given. A treatment within a phenomenological theory of continuous measurements is sketched. The system visualizes the important role of null measurements (negative result measurements) and may serve as a good example for a truly continuous measurement.	9906068v1
1999-06-29	Non dissipative decoherence of Rabi oscillations	We present a simple theoretical description of two recent experiments where damping of Rabi oscillations, which cannot be attributed to dissipative decoherence, has been observed. This is obtained considering the evolution time or the Hamiltonian as random variables and then averaging the usual unitary evolution on a properly defined, model-independent, probability distribution.	9906115v3
1999-07-30	Quantum trajectories for Brownian motion	We present the stochastic Schroedinger equation for the dynamics of a quantum particle coupled to a high temperature environment and apply it the dynamics of a driven, damped, nonlinear quantum oscillator. Apart from an initial slip on the environmental memory time scale, in the mean, our result recovers the solution of the known non-Lindblad quantum Brownian motion master equation. A remarkable feature of our approach is its localization property: individual quantum trajectories remain localized wave packets for all times, even for the classically chaotic system considered here, the localization being stronger the smaller $\hbar$.	9907100v1
2000-03-30	Stochastic dynamics of electronic wave packets in fluctuating laser fields	The dynamics of a laser-excited Rydberg electron under the influence of a fluctuating laser field are investigated. Rate equations are developed which describe these dynamics in the limit of large laser bandwidths for arbitrary types of laser fluctuations. These equations apply whenever all coherent effects have already been damped out. The range of validity of these rate equations is investigated in detail for the case of phase fluctuations. The resulting asymptotic power laws are investigated which characterize the long time dynamics of the laser-excited Rydberg electron and it is shown to which extent these power laws depend on details of the laser spectrum.	0003139v1
2000-07-12	Single photon generation by pulsed excitation of a single dipole	The fluorescence of a single dipole excited by an intense light pulse can lead to the generation of another light pulse containing a single photon. The influence of the duration and energy of the excitation pulse on the number of photons in the fluorescence pulse is studied. The case of a two-level dipole with strongly damped coherences is considered. The presence of a metastable state leading to shelving is also investigated.	0007037v1
2000-08-22	Effective Hamiltonian Approach to the Master Equation	A method of exactly solving the master equation is presented in this letter. The explicit form of the solution is determined by the time evolution of a composite system including an auxiliary system and the open system in question. The effective Hamiltonian governing the time evolution of the composed system are derived from the master equation. Two examples, the dissipative two-level system and the damped harmonic oscillator, are presented to illustrate the solving procedure. PACS number(s): 05.30.-d, 05.40.+j, 42.50.Ct	0008090v1
2001-01-01	Quantum-Liouville and Langevin Equations for Gravitational Radiation Damping	From a forward--backward path integral, we derive a master equation for the emission and absorption of gravitons by a massive quantum object in a heat bath of gravitons. Such an equation could describe collapse phenomena of dense stars. We also present a useful approximate Langevin equation for such a system.	0101006v1
2001-02-26	Bateman's dual system revisited: I. Quantization, geometric phase and relation with the ground-state energy of the linear harmonic oscillator	By using the Feynman-Hibbs prescription for the evolution amplitude, we quantize the system of a damped harmonic oscillator coupled to its time-reversed image, known as Bateman's dual system. The time-dependent quantum states of such a system are constructed and discussed entirely in the framework of the classical theory. The corresponding geometric (Pancharatnam) phase is calculated and found to be directly related to the ground-state energy of the 1D linear harmonic oscillator to which the 2D system reduces under appropriate constraint.	0102128v2
2001-03-14	Decoherence effects of motion-induced radiation	The radiation pressure coupling with vacuum fluctuations gives rise to energy damping and decoherence of an oscillating particle. Both effects result from the emission of pairs of photons, a quantum effect related to the fluctuations of the Casimir force. We discuss different alternative methods for the computation of the decoherence time scale. We take the example of a spherical perfectly-reflecting particle, and consider the zero and high temperature limits. We also present short general reviews on decoherence and dynamical Casimir effect.	0103083v1
2001-04-27	Time Evolution of tunneling and decoherence: soluble model	Decoherence effects associated to the damping of a tunneling two-level system are shown to dominate the tunneling probability at short times in strong coupling regimes in the context of a soluble model. A general decomposition of tunneling rates in dissipative and unitary parts is implemented. Master equation treatments fail to describe the model system correctly when more than a single relaxation time is involved.	0104132v1
2001-08-01	Heating and decoherence suppression using decoupling techniques	We study the application of decoupling techniques to the case of a damped vibrational mode of a chain of trapped ions, which can be used as a quantum bus in linear ion trap quantum computers. We show that vibrational heating could be efficiently suppressed using appropriate ``parity kicks''. We also show that vibrational decoherence can be suppressed by this decoupling procedure, even though this is generally more difficult because the rate at which the parity kicks have to applied increases with the effective bath temperature.	0108007v3
2001-11-29	Field quantization for chaotic resonators with overlapping modes	Feshbach's projector technique is employed to quantize the electromagnetic field in optical resonators with an arbitray number of escape channels. We find spectrally overlapping resonator modes coupled due to the damping and noise inflicted by the external radiation field. For wave chaotic resonators the mode dynamics is determined by a non--Hermitean random matrix. Upon including an amplifying medium, our dynamics of open-resonator modes may serve as a starting point for a quantum theory of random lasing.	0111156v2
2001-12-08	Quantum oscillations without quantum coherence	We study numerically the damping of quantum oscillations and the increase of entropy with time in model spin systems decohered by a spin bath. In some experimentally relevant cases, the oscillations of considerable amplitude can persist long after the entropy has saturated near its maximum, i.e. when the system has been decohered almost completely. Therefore, the pointer states of the system demonstrate non-trivial dynamics. The oscillations exhibit slow power-law decay, rather than exponential or Gaussian, and may be observable in experiments.	0112053v1
2001-12-10	Temporal Oscillations of Nonlinear Faraday Rotation in Coherently Driven Media	New phenomenon of temporal oscillations of nonlinear Faraday rotation in a driven four-level system is predicted. We show that in this system with one upper level, under the conditions of electromagnetically induced transparency created by a strong coupling field, the polarization rotation of weak probe light exhibits slowly damped oscillations with a frequency proportional to the strength of an applied magnetic field. This opens up an alternate way to sensitive magnetometric measurements. Applications in low-light nonlinear optics such as photon entanglement are feasible.	0112058v1
2001-12-31	Resonances and spectral properties of detuned OPO pumped by fluctuating sources	Twin beam fluctuations are analyzed for detuned and mismatched OPO configurations. Resonances and frequency responses to the quantum noise sources (quantum and pump amplitude/phase fluctuations) are examined as functions of cavity decay rates, excitation parameter and detuning. The dependence of self- and mutual correlations of beam amplitudes and phases on detuning, mismatch and damping parameters is discussed.	0112180v2
2002-03-04	Stationary cantilever vibrations in the oscillating cantilever-driven adiabatic reversals -- magnetic resonance force microscopy technique	We consider theoretically the novel technique in magnetic resonance force microscopy which is called ``oscillating cantilever-driven adiabatic reversals''. We present analytical and numerical analysis for the stationary cantilever vibrations in this technique. For reasonable values of parameters we estimate the resonant frequency shift as 6Hz per the Bohr magneton. We analyze also the regime of small oscillations of the paramagnetic moment near the transversal plane and the frequency shift of the damped cantilever vibrations.	0203013v1
2002-05-17	Embedding dissipation and decoherence in unitary evolution schemes	Dissipation and decoherence, and the evolution from pure to mixed states in quantum physics are handled through master equations for the density matrix. By embedding elements of this matrix in a higher-dimensional Liouville-Bloch equation, the methods of unitary integration are adapted to solve for the density matrix as a function of time, including the non-unitary effects of dissipation and decoherence. The input requires only solutions of classical, initial value time-dependent equations. Results are illustrated for a damped driven two-level system.	0205113v3
2002-05-31	Invitation to quantum dynamical semigroups	The theory of quantum dynamical semigroups within the mathematically rigorous framework of completely positive dynamical maps is reviewed. First, the axiomatic approach which deals with phenomenological constructions and general mathematical structures is discussed. Then basic derivation schemes of the constructive approach including singular coupling, weak coupling and low density limits are presented in their higly simplified versions. Two-level system coupled to a heat bath, damped harmonic oscillator, models of decoherence, quantum Brownian particle and Bloch-Boltzmann equations are used as illustrations of the general theory. Physical and mathematical limitations of the quantum open system theory, the validity of Markovian approximation and alternative approaches are discussed also.	0205188v1
2002-06-14	An Inverse-Problem Approach to Designing Photonic Crystals for Cavity QED Experiments	Photonic band gap (PBG) materials are attractive for cavity QED experiments because they provide extremely small mode volumes and are monolithic, integratable structures. As such, PBG cavities are a promising alternative to Fabry-Perot resonators. However, the cavity requirements imposed by QED experiments, such as the need for high Q (low cavity damping) and small mode volumes, present significant design challenges for photonic band gap materials. Here, we pose the PBG design problem as a mathematical inversion and provide an analytical solution for a two-dimensional crystal. We then address a planar (2D crystal with finite thickness) structure using numerical techniques.	0206094v1
2002-06-17	Damped Bloch oscillations of cold atoms in optical lattices	The paper studies Bloch oscillations of cold neutral atoms in the optical lattice. The effect of spontaneous emission on the dynamics of the system is analyzed both analytically and numerically. The spontaneous emission is shown to cause (i) the decay of Bloch oscillations with the decrement given by the rate of spontaneous emission and (ii) the diffusive spreading of the atoms with a diffusion coefficient depending on {\em both} the rate of spontaneous emission and the Bloch frequency.	0206108v1

2003-11-06

Perturbation-induced radiation by the Ablowitz-Ladik soliton

An efficient formalism is elaborated to analytically describe dynamics of the Ablowitz-Ladik soliton in the presence of perturbations. This formalism is based on using the Riemann-Hilbert problem and provides the means of calculating evolution of the discrete soliton parameters, as well as shape distortion and perturbation-induced radiation effects. As an example, soliton characteristics are calculated for linear damping and quintic perturbations.

0311010v1

2004-04-26

Nonlinear stability of oscillatory wave fronts in chains of coupled oscillators

We present a stability theory for kink propagation in chains of coupled oscillators and a new algorithm for the numerical study of kink dynamics. The numerical solutions are computed using an equivalent integral equation instead of a system of differential equations. This avoids uncertainty about the impact of artificial boundary conditions and discretization in time. Stability results also follow from the integral version. Stable kinks have a monotone leading edge and move with a velocity larger than a critical value which depends on the damping strength.

0404044v1

2004-10-15

Comment on "Soliton ratchets induced by excitation of internal modes"

Very recently Willis et al. [Phys. Rev. E {\bf 69}, 056612 (2004)] have used a collective variable theory to explain the appearance of a nonzero energy current in an ac driven, damped sine-Gordon equation. In this comment, we prove rigorously that the time-averaged energy current in an ac driven nonlinear Klein-Gordon system is strictly zero.

0410021v1

2005-02-25

A kinetic approach to Bose-Einstein condensates: self-phase modulation and Bogoliubov oscillations

A kinetic approach to the Bose-Einstein condensates (BECs) is proposed, based on the Wigner-Moyal equation (WME). In the quasi-classical limit, the WME reduces to the particle number conservation equation. Two examples of application are: i) a self-phase modulation of a BE condensate beam where we show that part of the beam is decelerated and eventually stops as a result of the gradient of the effective self-potential; ii) the derivation of a kinetic dispersion relation for sound waves in the BECs, including a collisionless Landau damping.

0502059v1

2006-01-14

Chaotic Vibration of a Quarter-Car Model Excited by the Road Surface Profile

The Melnikov criterion is used to examine a global homoclinic bifurcation and transition to chaos in the case of a quarter car model excited kinematically by the road surface profile. By analyzing the potential an analytic expression is found for the homoclinic orbit. By introducing an harmonic excitation term and damping as perturbations, the critical Melnikov amplitude of the road surface profile is found, above which the system can vibrate chaotically.

0601030v1

2006-01-14

Transition to Chaos in the Self-Excited System with a Cubic Double Well Potential and Parametric Forcing

We examine the Melnikov criterion for a global homoclinic bifurcation and a possible transition to chaos in case of a single degree of freedom nonlinear oscillator with a symmetric double well nonlinear potential. The system was subjected simultaneously to parametric periodic forcing and self excitation via negative damping term. Detailed numerical studies confirm the analytical predictions and show that transitions from regular to chaotic types of motion are often associated with increasing the energy of an oscillator and its escape from a single well.

0601032v1

2006-07-19

Energy flux fluctuations in a finite volume of turbulent flow

The flux of turbulent kinetic energy from large to small spatial scales is measured in a small domain B of varying size R. The probability distribution function of the flux is obtained using a time-local version of Kolmogorov's four-fifths law. The measurements, made at a moderate Reynolds number, show frequent events where the flux is backscattered from small to large scales, their frequency increasing as R is decreased. The observations are corroborated by a numerical simulation based on the motion of many particles and on an explicit form of the eddy damping.

0607044v1

2006-08-09

Statistical properties of the continuum Salerno model

The statistical properties of the Salerno model is investigated. In particular, a comparison between the coherent and partially coherent wave modes is made for the case of a random phased wave packet. It is found that the random phased induced spectral broadening gives rise to damping of instabilities, but also a broadening of the instability region in quasi-particle momentum space. The results can be of significance for condensation of magnetic moment bosons in deep optical lattices.

0608016v1

2006-10-18

Whitham method for Benjamin-Ono-Burgers equation and dispersive shocks in internal waves in deep fluid

The Whitham modulation equations for the parameters of a periodic solution are derived using the generalized Lagrangian approach for the case of damped Benjamin-Ono equation. The structure of the dispersive shock in internal wave in deep water is considered by this method.

0610039v1

2007-03-28

Quasi-Patterns in a Model of Multi-Resonantly Forced Chemical Oscillations

Multi-frequency forcing of systems undergoing a Hopf bifurcation to spatially homogeneous oscillations is investigated using a complex Ginzburg-Landau equation that systematically captures weak forcing functions that simultaneously hit the 1:1-, the 1:2-, and the 1:3-resonance. Weakly nonlinear analysis shows that generically the forcing function can be tuned such that resonant triad interactions with weakly damped modes stabilize subharmonic quasipatterns with 4-fold and 5-fold rotational symmetry. In simulations starting from random initial conditions domains of these quasi-patterns compete and yield complex, slowly ordering patterns.

0703059v1

2001-06-09

Conditions for Isoscaling in Nuclear Reactions

Isoscaling, where ratios of isotopes emitted from two reactions exhibit an exponential dependence on the neutron and proton number of the isotope, has been observed over a variety of reactions including evaporation, strongly damped binary collision, and multifragmentation. The conditions for isoscaling to occur as well as the conditions when isoscaling fails are investigated.

0106009v1

1992-12-25

Chaotic Behavior in Warm Deformed Nuclei Induced by Residual Two-Body Interactions

Band mixing calculations in rapidly rotating well-deformed nuclei are presented, investigating the properties of energy levels and rotational transitions as a function of excitation energy. Substantial fragmentation of E2 transitions is found for $E_x \gsim$ 800 keV above yrast, which represents the onset of rotational damping. Above $E_x \approx $ 2 MeV, energy levels and E2 strengths display fluctuations typical of quantum chaotic systems, which are determined by the high multipole components of the two-body residual interaction.

9212015v1

1993-07-07

Color Diffusion and Conductivity in a Quark-Gluon Plasma

Color diffusion is shown to be an important dissipative property of quark-gluon plasmas that rapidly damps collective color modes. We derive the characteristic color relaxation time scale, $t_c\approx (3\alpha_s T \log(m_E/m_M ))^{-1}$, showing its sensitivity to the ratio of the static color electric and magnetic screening masses. This leads to a surprisingly small color conductivity, $\sigma_c\approx 2 T/\log(m_E/m_M)$, which in fact vanishes in the semi-classical (1-loop) limit.

9307007v1

1994-04-18

Vibrations versus collisions and the iterative structure of two-body dynamics

We adopt a truncated version of two-body dynamics by neglecting three-body correlations, as is supported by microscopic numerical calculations. Introducing orthogonal channel correlations for the pp- and the ph-channel and integrating the latter in terms of vibrational RPA-states we derive a retarded two-body equation. Its solution is nonperturbative with respect to loops, ladders and mixed contributions. In the stationary limit we obtain an equation for a generalised effective interaction which iterates both the G-matrix and the polarisation matrix. An in-medium scattering approach transparently demonstrates the collisional damping of the vibrations.

9404020v1

1994-07-01

Friedel Oscillations in Relativistic Nuclear Matter

We calculate the low-momentum N-N effective potential obtained in the OBE approximation, inside a nuclear plasma at finite temperature, as described by the relativistic $ \sigma $-$ \omega $ model. We analyze the screening effects on the attractive part of the potential in the intermediate range as density or temperature increase. In the long range the potential shows Friedel-like oscillations instead of the usual exponential damping. These oscillations arise from the sharp edge of the Fermi surface and should be encountered in any realistic model of nuclear matter.

9407002v1

1995-12-19

Macroscopic Features of Light Heavy-Ion Fission Reactions

Global macroscopic features observed in the fully-damped binary processes in light di-nuclear systems, such as limiting angular momenta, mean total kinetic energies and energy thresholds for fusion-fission processes (''fission thresholds") are presented. Their deduced systematics are consistent with that obtained for heavier systems and follow a fusion-fission picture which can be described by a realistic rotating liquid drop model considering diffuse-surface and finite-nuclear-range effects.

9512025v1

1995-12-28

Classical and Quantal Irregular Scatterings with Complex Target

One-dimensional scattering by a target with two internal degrees of freedom is investigated. The damping of resonance peaks and the associated appearance of the fluctuating background in the quantum inelastic scattering amplitudes are found. Examination of the analog classical system reveals a disorderly reaction function, which is then related to the quantum amplitude through a semiclassical argument.

9512038v1

1996-03-21

Time development of a density perturbation in the unstable nuclear matter

We present the solution of the time development of an unstable initial density perturbation in the linearized Vlasov equation, completing the previous analysis in the literature. The additional contributions found are usually damped and can be neglected at large times in the unstable region. The work clarifies also the problem of the normalization of the solution with respect to the initial perturbation of the density.

9603029v2

1997-02-12

A self-consistent treatment of the dynamics of stable and unstable collective modes

We address the dynamics of damped collective modes in terms of first and second moments. The modes are introduced in a self-consistent fashion with the help of a suitable application of linear response theory. Quantum effects in the fluctuations are governed by diffusion coefficients D_{\mu\nu}. The latter are obtained through a fluctuation dissipation theorem generalized to allow for a treatment of unstable modes. Numerical evaluations of the D_{\mu\nu} are presented. We discuss briefly how this picture may be used to describe global motion within a locally harmonic approximation.

9702029v1

1998-07-27

Isovector Vibrations in Nuclear Matter at Finite Temperature

We consider the propagation and damping of isovector excitations in heated nuclear matter within the Landau Fermi-liquid theory. Results obtained for nuclear matter are applied to calculate the Giant Dipole Resonance (GDR) at finite temperature in heavy spherical nuclei within Steinwedel and Jensen model. The centroid energy of the GDR slightly decreases with increasing temperature and the width increases as $T^2$ for temperatures $T < 5$ MeV in agreement with recent experimental data for GDR in $^{208}$Pb and $^{120}$Sn. The validity of the method for other Fermi fluids is finally suggested.

9807070v1

1998-09-03

Relaxation of fast collective motion in heated nuclei

The damping of the collective vibrations in hot nuclei is studied within the semiclassical Vlasov-Landau kinetic theory. The extention of the method of independent sources of dissipation is used to allow for irreversible energy transfer by chaos weighted wall formula. The expressions for the intrinsic width of the giant multipole resonances are obtained. The interplay between the one-body and the two-body channels which contribute to the formation of the intrinsic width in nuclei is discussed.

9809010v1

1998-09-04

An investigation of interplay between dissipation mechanisms in heated Fermi systems by means of radiative strength functions

A simple analytical expression for the gamma-decay strength function is derived with microcanonical ensemble for initial excited states. The approach leads to both a non-zero limit of the strength function for vanishing gamma-ray energy and a partial breakdown of Brink hypothesis. It is shown that the low energy behaviour of the gamma-decay strength functions is governed by the energy behavior of the damping width. It may provides a new tool for study of the interplay between different relaxation mechanisms of the collective excitations.

9809012v1

1998-09-11

Damping of giant resonances in asymmetric nuclear matter

The giant collective modes in asymmetric nuclear matter are investigated within a dynamic relaxation time approximation. We derive a coupled dispersion relation and show that two sources of coupling appear: (i) a coupling of isoscalar and isovector modes due to different mean-fields acting and (ii) an explicit new coupling in asymmetric matter due to collisional interaction. We show that the latter one is responsible for a new mode arising besides isovector and isoscalar modes.

9809035v1

1998-10-01

Giant Octupole Resonance Simulation

Using a pseudo-particle technique we simulate large-amplitude isoscalar giant octupole excitations in a finite nuclear system. Dependent on the initial conditions we observe either clear octupole modes or over-damped octupole modes which decay immediately into quadrupole ones. This shows clearly a behavior beyond linear response. We propose that octupole modes might be observed in central collisions of heavy ions.

9810005v3

1998-10-14

Finite Temperature Nuclear Response in Extended Random-Phase Approximation

The nuclear collective response at finite temperature is investigated for the first time in the quantum framework of the small amplitude limit of the extended TDHF approach, including a non-Markovian collision term. It is shown that the collision width satisfies a secular equation. By employing a Skyrme force, the isoscalar monopole, isovector dipole and isoscalar quadrupole excitations in $^{40}Ca$ are calculated and important quantum features are pointed out. The collisional damping due to decay into incoherent 2p-2h states is small at low temperatures but increases rapidly at higher temperatures.

9810042v1

1999-05-07

Influence of damping on the excitation of the double giant resonance

We study the effect of the spreading widths on the excitation probabilities of the double giant dipole resonance. We solve the coupled-channels equations for the excitation of the giant dipole resonance and the double giant dipole resonance. Taking Pb+Pb collisions as example, we study the resulting effect on the excitation amplitudes, and cross sections as a function of the width of the states and of the bombarding energy.

9905018v2

2000-03-15

Double giant dipole resonances in time-dependent density-matrix theory

The strength functions of the DGDRs in 16O and 40Ca are calculated using an extended version of TDHF known as the time-dependent density-matrix theory (TDDM). The calculations are done in a self-consistent manner, in which the same Skyrme force as that used for the mean-field potential is used as the residual interaction to calculate two-body correlations. It is found that the DGDR in 16O has a large width due to the Landau damping, although the centroid energy of the DGDR is close to twice the energy of the GDR calculated in RPA. The DGDR in 40Ca is found more harmonic than that in 16O.

0003034v2

2001-06-28

Description of Double Giant Dipole Resonance within the Phonon Damping Model

In a recent Letter [1] an overall agreement with the experimental data for the excitation of the single and double giant dipole resonances in relativistic heavy ion collision in 136Xe and 208Pb nuclei has been reported. We point out that this agreement is achieved by a wrong calculation of the DGDR excitation mechanism. We also argue that the agreement with the data for the widths of resonances is achieved by an unrealistically large value of a model parameter. [1] Nguyen Dinh Dang, Vuong Kim Au, and Akito Arima, Phys. Rev. Lett. 85 (2000) 1827.

0106065v1

2001-11-08

Note on the Deformed Boson Scheme in Time-Dependent Variational Method

The Holstein-Primakoff representation for the su(2)-algebra is derived in the deformed boson scheme. The following two points are discussed : (i) connection between a simple Hamiltonian and the Hamiltonian obeying the su(2)-algebra such as Lipkin model and (ii) derivation of the Hamiltonian for describing the damped and amplified motion for the su(2)-boson model.

0111029v1

2002-10-15

Non-Markovian Collision Integral in Fermi-systems

The non-Markovian collision integral is obtained on the base of the Kadanoff-Baym equations for Green functions in a form with allowance for small retardation effects. The collisional relaxation times and damping width of the giant isovector dipole resonances in nuclear matter are calculated. For an infinite Fermi liquid the dependence of the relaxation times on the collective vibration frequency and the temperature corresponds to the Landau's prescription.

0210046v1

2003-04-07

Mean first passage time for fission potentials having structure

A schematic model of over-damped motion is presented which permits one to calculate the mean first passage time for nuclear fission. Its asymptotic value may exceed considerably the lifetime suggested by Kramers rate formula, which applies only to very special, favorable potentials and temperatures. The additional time obtained in the more general case is seen to allow for a considerable increment in the emission of light particles.

0304022v1

2003-09-05

Pairing effect on the giant dipole resonance width at low temperature

The width of the giant dipole resonance (GDR) at finite temperature T in Sn-120 is calculated within the Phonon Damping Model including the neutron thermal pairing gap determined from the modified BCS theory. It is shown that the effect of thermal pairing causes a smaller GDR width at T below 2 MeV as compared to the one obtained neglecting pairing. This improves significantly the agreement between theory and experiment including the most recent data point at T = 1 MeV.

0309010v1

2003-12-19

Response in the continuum for light deformed neutron-rich nuclei

The time-dependent Hartree-Fock calculation with a full Skyrme energy functional has been carried out on the three-dimensional Cartesian lattice space to study E1 giant dipole resonances (GDR) in light nuclei. The outgoing boundary condition for the continuum states is treated by the absorbing complex potential. The calculation for GDR in O-16 suggests a significant influence of the residual interaction associated with time-odd densities in the Skyrme functional. We also predict a large damping for superdeformed Be-14 at the neutron drip line.

0312089v1

2004-11-18

Nuclear giant resonances

This talk presents the recent status of theoretical and experimental studies of giant resonances in nuclei with the emphasis on: (1) charge-exchange Gamow-Teller resonance, (2) multiple-phonon resoanances, (3) giant dipole resonances in highly excited nuclei, and (4) pygmy dipole resonances in neutron rich nuclei. In particular, the description of these resonances within the framework of the phonon damping model is discussed in detail.

0411073v1

1996-06-04

Direct Hopf Bifurcation in Parametric Resonance of Hybridized Waves

We study parametric resonance of interacting waves having the same wave vector and frequency. In addition to the well-known period-doubling instability we show that under certain conditions the instability is caused by a Hopf bifurcation leading to quasiperiodic traveling waves. It occurs, for example, if the group velocities of both waves have different signs and the damping is weak. The dynamics above the threshold is briefly discussed. Examples concerning ferromagnetic spin waves and surface waves of ferro fluids are discussed.

9605006v1

1999-05-27

Impurity-induced stabilization of solitons in arrays of parametrically driven nonlinear oscillators

Chains of parametrically driven, damped pendula are known to support soliton-like clusters of in-phase motion which become unstable and seed spatiotemporal chaos for sufficiently large driving amplitudes. We show that the pinning of the soliton on a "long" impurity (a longer pendulum) expands dramatically its stability region whereas "short" defects simply repel solitons producing effective partition of the chain. We also show that defects may spontaneously nucleate solitons.

9905009v1

1999-11-19

Origin of Multikinks in Dispersive Nonlinear Systems

We develop {\em the first analytical theory of multikinks} for strongly {\em dispersive nonlinear systems}, considering the examples of the weakly discrete sine-Gordon model and the generalized Frenkel-Kontorova model with a piecewise parabolic potential. We reveal that there are no $2\pi$-kinks for this model, but there exist {\em discrete sets} of $2\pi N$-kinks for all N>1. We also show their bifurcation structure in driven damped systems.

9911006v1

1998-02-04

The steady state of a pumped and damped atom laser

This paper has been withdrawn, as further work has shown that an atom laser as described by the model herein does not have a steady state, so it doesn't matter much what it would look like.

9802008v2

1998-02-20

Phase Dynamics of Bose-Einstein Condensates: Losses versus Revivals

In the absence of losses the phase of a Bose-Einstein condensate undergoes collapses and revivals in time due to elastic atomic interactions. As experiments necessarily involve inelastic collisions, we develop a model to describe the phase dynamics of the condensates in presence of collisional losses. We find that a few inelastic processes are sufficient to damp the revivals of the phase. For this reason the observability of phase revivals for present experimental conditions is limited to condensates with a few hundreds of atoms.

9802040v1

1998-02-25

Radiation Reaction fields for an accelerated dipole for scalar and electromagnetic radiation

The radiation reaction fields are calculated for an accelerated changing dipole in scalar and electromagnetic radiation fields. The acceleration reaction is shown to alter the damping of a time varying dipole in the EM case, but not the scalar case. In the EM case, the dipole radiation reaction field can exert a force on an accelerated monopole charge associated with the accelerated dipole. The radiation reaction of an accelerated charge does not exert a torque on an accelerated magnetic dipole, but an accelerated dipole does exert a force on the charge. The technique used is that originally developed by Penrose for non-singular fields and extended by the author for an accelerated monopole charge.

9802047v1

1998-03-27

Semiclassical spin damping: Superradiance revisited

A well known description of superradiance from pointlike collections of many atoms involves the dissipative motion of a large spin. The pertinent ``superradiance master equation'' allows for a formally exact solution which we subject to a semiclassical evaluation. The clue is a saddle-point approximation for an inverse Laplace transform. All previous approximate treatments, disparate as they may appear, are encompassed in our systematic formulation. A byproduct is a hitherto unknown rigorous relation between coherences and probabilities. Our results allow for generalizations to spin dynamics with chaos in the classical limit.

9803041v1

1999-12-24

Differential criterion of a bubble collapse in viscous liquids

The present work is devoted to a model of bubble collapse in a Newtonian viscous liquid caused by an initial bubble wall motion. The obtained bubble dynamics described by an analytic solution significantly depends on the liquid and bubble parameters. The theory gives two types of bubble behavior: collapse and viscous damping. This results in a general collapse condition proposed as the sufficient differential criterion. The suggested criterion is discussed and successfully applied to the analysis of the void and gas bubble collapses.

9912050v1

1999-12-27

Rutherford Scattering with Retardation

Numerical solutions for Sommerfeld model in nonrelativistic case are presented for the scattering of a spinless extended charged body in a static Coulomb field of a fixed point charge. It is shown that differential cross section for extended body preserves the form of the Rutherford result with multiplier, not equal to one (as in classical case), but depending on the size of Sommerfeld particle. Also the effect of capture by attractive center is found out for Sommerfeld particle. The origin of this effect lies in radiation damping.

9912051v2

2000-08-04

A Variational Approach in the Dissipative Nonlinear Schrödinger Equation

The properties of pulse propagation in a nonlinear fiber including linear damped term added in the usual nonlinear Schr\"odinger equation is analyzed analytically. We apply variational modified approach based on the lagrangian that describe the dynamic of system and with a trial function we obtain a solution which is more accuracy when compared with a pertubative solution. As a result, the problem of pulse propagation in a fiber with loss can be described in good agreement with exact results.

0008011v1

2000-12-21

Intrabeam Scattering Analysis of ATF Beam Data Taken in April 2000

In April 2000 the single bunch energy spread, bunch length, horizontal emittance, and vertical emittance were measured as functions of current in KEK's ATF damping ring. In this report the measurement results are analyzed in light of intrabeam scattering theory. The measurements are found to be relatively consistent with theory, although the measured effects appear to be stronger than theory. In addition, the factor of 3 growth in vertical emittance at a current of 3 mA does not seem to be supported.

0012055v1

2001-03-09

Trapping oscillations, discrete particle effects and kinetic theory of collisionless plasma

Effects induced by the finite number $N$ of particles on the evolution of a monochromatic electrostatic perturbation in a collisionless plasma are investigated. For growth as well as damping of a single wave, discrete particle numerical simulations show a $N$-dependent long time behavior which differs from the numerical errors incurred by vlasovian approaches and follows from the pulsating separatrix crossing dynamics of individual particles.

0103025v1

2001-05-30

Impedance Analysis of Bunch Length Measurements at the ATF Damping Ring

We present energy spread and bunch length measurements at the Accelerator Test Facility (ATF) at KEK, as functions of current, for different ring rf voltages, and with the beam both on and off the coupling resonance. We fit the on-coupling bunch shapes to those of an impedance model consisting of a resistor and an inductor connected in series. We find that the fits are reasonably good, but that the resulting impedance is unexpectedly large.

0105102v1

2001-12-14

Active Vibration Suppression R&D for the NLC

The nanometer scale beam sizes at the interaction point in linear colliders limit the allowable motion of the final focus magnets. We have constructed a prototype system to investigate the use of active vibration damping to control magnet motion. Inertial sensors are used to measure the position of a test mass, and a DSP based system provides feedback using electrostatic pushers. Simulation and experimental results for the control of a mechanically simple system are presented.

0112042v1

2002-04-15

Laser-Generated Ultrashort Multi-Megagauss Magnetic Pulses in Plasmas

We demonstrate ultrashort (6 ps), multi-Megagauss (27 MG) magnetic pulses generated upon interaction of an intense laser pulse (10^{16} Wcm^-2, 100 fs) with a solid target. The temporal evolution of these giant fields generated near the high density critical layer is obtained with the highest resolution reported so far. Particle-in-cell simulations and phenomenological modeling is used to explain the results. The first direct observations of anomalously rapid damping of plasma shielding currents produced in response to the hot electron currents penetrating the bulk plasma are presented.

0204039v1

2002-04-29

Neutral Plasma Oscillations at Zero Temperature

We use cold plasma theory to calculate the response of an ultracold neutral plasma to an applied rf field. The free oscillation of the system has a continuous spectrum and an associated damped quasimode. We show that this quasimode dominates the driven response. We use this model to simulate plasma oscillations in an expanding ultracold neutral plasma, providing insights into the assumptions used to interpret experimental data [Phys. Rev. Lett. 85, 318 (2000)].

0204084v1

2002-09-04

Vortex Ring Reconnections

We investigate numerically the Navier-Stokes dynamics of reconnecting vortex rings at small $Re$ number. We find that reconnections are dissipative due to the smoothing of vorticity gradients at reconnection kinks and to the formation of secondary structures of stretched anti-parallel vorticity which transfer kinetic energy to small scales where it is subsequently dissipated efficiently. In addition, the relaxation of the reconnection kinks excites Kelvin waves which due to strong damping are of low wavenumber and affect directly only large scale properties of the flow.

0209014v1

2002-11-05

Analise Termodinamica da aceleracao de uma massa

We analyse the acceleration of a mass with a simple structure taking into account Thermodynamics. Two situations are analysed. The first one for the application of a localized force to a point of the mass. The second one for the application of a force to the entire mass. The two situations are not equivalent. For the first situation we have an increase of temperature of the mass, resulting from an internal damping, during a transient.

0211021v1

2003-05-30

A Sum Rule for Nonlinear Optical Susceptibilities

It is explicitly shown, for optical processes arbitrarily comprising two-, three- or four-photon interactions, that the sum over all matter states of any optical susceptibility is exactly zero. The result remains true even in frequency regions where damping is prominent. Using a quantum electrodynamical framework to render the photonic nature of the fundamental interactions, the result emerges in the form of a traceless operator in Hilbert space. The generality of the sum rule and its significance as a thermodynamic limit are discussed, and the applicability to real systems is assessed.

0305131v1

2003-10-16

Ionization of clusters in intense laser pulses through collective electron dynamics

The motion of electrons and ions in medium-sized rare gas clusters (1000 atoms) exposed to intense laser pulses is studied microscopically by means of classical molecular dynamics using a hierarchical tree code. Pulse parameters for optimum ionization are found to be wavelength dependent. This resonant behavior is traced back to a collective electron oscillation inside the charged cluster. It is shown that this dynamics can be well described by a driven and damped harmonic oscillator allowing for a clear discrimination against other energy absorption mechanisms.

0310073v1

2003-11-14

Transverse modulational instability of partially incoherent soliton stripes

Based on the Wigner distribution approach, an analysis of the effect of partial incoherence on the transverse instability of soliton structures in nonlinear Kerr media is presented. It is explicitly shown, that for a Lorentzian incoherence spectrum the partial incoherence gives rise to a damping which counteracts, and tends to suppress, the transverse instability growth. However, the general picture is more complicated and it is shown that the effect of the partial incoherence depends crucially on the form of the incoherence spectrum. In fact, for spectra with finite rms-width, the partial incoherence may even increase both the growth rate and the range of unstable, transverse wave numbers.

0311068v1

2004-02-13

Ion energy balance during fast wave heating in TORE SUPRA

Direct coupling of the fast magnetosonic wave to the electrons has been studied on the tokamak TORE SUPRA. Preliminary experiments were dedicated to optimise the scenario for Fast Wave Electron Heating (FWEH) and Current Drive (FWCD). In a first part, thermal kinetic and diamagnetic energy are compared when fast wave is applied to the plasma in two different regimes: 1/ the minority hydrogen heating scenario (ICRH), 2/ the direct electron damping. Effects of ion resonant layers, marginally present in the plasma in the later regime (FWEH), is then presented and discussed.

0402067v1

2004-04-14

Earthquakes temporal occurrence: a statistical study

The distribution of inter-occurrence time between seismic events is a quantity of great interest in seismic risk assessment. We evaluate this distribution for different models of earthquakes occurrence and follow two distinct approaches: The non homogeneous Poissonian and the non Poissonian one. In all cases we obtain either a power law or a power law damped by an exponential factor behaviour. This feature of the distribution makes impossible any prediction of earthquakes occurrence. Nevertheless it suggests the interpretation of the earthquake occurrence phenomenon as due to some non-linear dynamics to be further investigated.

0404068v1

2004-07-14

Exponential versus linear amplitude decay in damped oscillators

We comment of the widespread belief among some undergraduate students that the amplitude of any harmonic oscillator in the presence of any type of friction, decays exponentially in time. To dispel that notion, we compare the amplitude decay for a harmonic oscillator in the presence of (i) viscous friction and (ii) dry friction. It is shown that, in the first case, the amplitude decays exponentially with time while in the second case, it decays linearly with time.

0407080v1

2004-10-21

Kinetic effects in strong Langmuir turbulence

Kinetic effects with regard to a one dimensional Langmuir soliton-like pulse are investigated. Though thus far mainly transit-time accelerations have been investigated regarding strong Langmuir turbulence, it is found that ponderomotive reflections (generalized nonlinear Landau damping) may play important roles also. The former may diffuse fast electrons up to relativistic energies, while the latter reflects slow electrons as well as ions that have speeds comparable with the group velocity of the pulse, and tend to form flat-top electron distributions at and around the quasi-soliton.

0410179v2

2005-01-07

Velocity-Space Diffusion in a Perpendicularly Propagating Electrostatic Wave

The motion of ions in the fields B = B_0 zhat and E = E_0 yhat cos(k_perp y - omega t) is considered. When omega >> Omega_i and v_perp > omega/k_perp, the equations of motion may be reduced to a set of difference equations. These equations exhibit stochastic behavior when E_0 exceeds a threshold. The diffusion coefficient above the threshold is determined. Far above the threshold, ion Landau damping is recovered. Extension of the method to include parallel propagation is outlined.

0501035v1

2005-02-02

Swinging of two-dimensional solitons in harmonic and Bessel optical lattices

We consider parametric amplification of two-dimensional spatial soliton swinging in longitudinally modulated harmonic and Bessel lattices in Kerr-type saturable medium. We show that soliton center oscillations along different axes in two-dimensional lattices are coupled, which give rise to a number of interesting propagation scenarios including periodic damping and excitation of soliton oscillations along perpendicular axes, selective amplification of soliton swinging along one of transverse axes and enhancement of soliton spiraling.

0502009v1

2005-09-13

A Landau fluid model for warm collisionless plasmas

A Landau fluid model for a collisionless electron-proton magnetized plasma, that accurately reproduces the dispersion relation and the Landau damping rate of all the magnetohydrodynamic waves, is presented. It is obtained by an accurate closure of the hydrodynamic hierarchy at the level of the fourth order moments, based on linear kinetic theory. It retains non-gyrotropic corrections to the pressure and heat flux tensors up to the second order in the ratio between the considered frequencies and the ion cyclotron frequency.

0509091v1

2005-10-13

An illustrative experiment on electromagnetic oscillations

It is the purpose of this manuscript to place an illustrative demonstration on the measurement of damped electromagnetic oscillations for a RLC circuit that it is easy to set in any physics laboratory equipped with PASCO technologies and USB Electrical PASPort sensors together with standard electrical components. The results of recording the electrical voltage with DATA Studio software have a very good agreement with performed simulations from MULTISIM software and/or standard calculations from theory. Our students and instructors enjoy of the experiment for their simplicity set up in addition to the instructive oscillations.

0510122v1

2005-12-20

Coupled atomic-molecular condensates in a double-well potential: decaying molecular oscillations

We present a four-mode model that describes coherent photo-association (PA) in a double-well Bose-Einstein condensate, focusing on the $average$ molecular populations in certain parameters. Our numerical results predict an interesting strong-damping effect of molecular oscillations by controlling the particle tunnellings and PA light strength, which may provide a promising way for creating a stable molecular condensate via coherent PA in a magnetic double-well potential.

0512184v2

2007-02-21

Liquid-infiltrated photonic crystals: Ohmic dissipation and broadening of modes

The pronounced light-matter interactions in photonic crystals make them interesting as opto-fludic "building blocks" for lab-on-a-chip applications. We show how conducting electrolytes cause dissipation and smearing of the density-of-states, thus altering decay dynamics of excited bio-molecules dissolved in the electrolyte. Likewise, we find spatial damping of propagating modes, of the order dB/cm, for naturally occurring electrolytes such as drinking water or physiological salt water.

0702176v1

2004-04-08

Mathematical Analysis and Simulations of the Neural Circuit for Locomotion in Lamprey

We analyze the dynamics of the neural circuit of the lamprey central pattern generator (CPG). This analysis provides insights into how neural interactions form oscillators and enable spontaneous oscillations in a network of damped oscillators, which were not apparent in previous simulations or abstract phase oscillator models. We also show how the different behaviour regimes (characterized by phase and amplitude relationships between oscillators) of forward/backward swimming, and turning, can be controlled using the neural connection strengths and external inputs.

0404012v1

2005-08-11

Time Reversal of the Increasing Geometrical Progression of the Population of a Simple Biological Specie

In this work we consider time reversal of the increasing geometrical progression of the population of a simple biological species without any enemies (predators) in the appropriate environment with unlimited resources (food, territory, etc.). It is shown that such time reversal corresponds to appearance of the cannibalism, i.e. self-predaciousness or self-damping phenomena which can be described by a type of difference Verhulst equation.

0508011v1

1996-06-11

Condensate fluctuations of a trapped, ideal Bose gas

For a non-self-interacting Bose gas with a fixed, large number of particles confined to a trap, as the ground state occupation becomes macroscopic, the condensate number fluctuations remain micrscopic. However, this is the only significant aspect in which the grand canonical description differs from canonical or microcanonical in the thermodynamic limit. General arguments and estimates including some vanishingly small quantities are compared to explicit, fixed-number calculations for 10^2 to 10^6 particles.

9606009v2

1996-11-27

A precision test of decoherence

The motion of a charged particle over a conducting plate is damped by Ohmic resistance to image currents. This interaction between the particle and the plate must also produce decoherence, which can be detected by examining interference patterns made by diffracted particle beams which have passed over the plate. Because the current densities within the plate decay rapidly with the height of the particle beam above it, the strength of decoherence should be adjustable across a wide range, allowing one to probe the full range of quantum through classical behaviour.

9611049v2

1997-03-16

Least-squares inversion for density-matrix reconstruction

We propose a method for reconstruction of the density matrix from measurable time-dependent (probability) distributions of physical quantities. The applicability of the method based on least-squares inversion is - compared with other methods - very universal. It can be used to reconstruct quantum states of various systems, such as harmonic and and anharmonic oscillators including molecular vibrations in vibronic transitions and damped motion. It also enables one to take into account various specific features of experiments, such as limited sets of data and data smearing owing to limited resolution. To illustrate the method, we consider a Morse oscillator and give a comparison with other state-reconstruction methods suggested recently.

9703026v1

1997-04-02

Approximate quantum error correction can lead to better codes

We present relaxed criteria for quantum error correction which are useful when the specific dominant noise process is known. These criteria have no classical analogue. As an example, we provide a four-bit code which corrects for a single amplitude damping error. This code violates the usual Hamming bound calculated for a Pauli description of the error process, and does not fit into the GF(4) classification.

9704002v1

1997-04-08

Measured Quantum Dynamics of a Trapped Ion

The measurement process is taken into account in the dynamics of trapped ions prepared in nonclassical motional states. The induced decoherence is shown to manifest itself both in the inhibition of the internal population dynamics and in a damping of the vibrational motion without classical counterpart. Quantitative comparison with present experimental capabilities is discussed, leading to a proposal for the verification of the predicted effects.

9704016v1

1997-09-09

Quantum gravity and the problem of measurement

We discuss some arguments in favour of the proposal that the quantum correlations contained in the pure state-vector evolving according to Schoedinger equation can be eliminated by the action of multiply connected wormholes during measurement. We devise a procedure to obtain a proper master equation which governes the changes of the reduced density matrix of matter fields interacting with doubly connected wormholes. It is shown that this master equation predicts an appropriate damping of the off-diagonal correlations contained in the state vector.

9709018v1

1998-04-06

Field Oscillations in a Micromaser with Injected Atomic Coherence

The electric field in a lossless, regularly-pumped micromaser with injected atomic coherence can undergo a period 2 oscillations in the steady state. The field changes its value after a single atom passes through the micromaser cavity, but returns to its original value after a second atom travels through. We give a simple explanation for this phenomenon in terms of tangent and cotangent states. We also examine the effect of cavity damping on this steady state.

9804017v1

1998-09-14

Macroscopically distinct quantum superposition states as a bosonic code for amplitude damping

We show how macroscopically distinct quantum superposition states (Schroedinger cat states) may be used as logical qubit encodings for the correction of spontaneous emission errors. Spontaneous emission causes a bit flip error which is easily corrected by a standard error correction circuit. The method works arbitrarily well as the distance between the amplitudes of the superposed coherent states increases.

9809037v2

1998-09-27

Quantum Dynamics of Topological Singularities: Feynman's Influence Functional Approach

Starting from the microscopic theory of Bardeen-Cooper-Schrieffer (BCS) for the fermionic superfluids, we show that the vortex dynamics can be followed naturally by extending Feynman's influence functional approach to incorporate the transverse force. There is a striking mutual independence of the transverse and longitudinal influences: The former has the topological origin and is insensitive to details, while the latter corresponds to the well-known damping kernel depending on details.

9809080v1

1998-11-14

Two-atom dark states in electromagnetic cavities

The center-of-mass motion of two two-level atoms coupled to a single damped mode of an electromagnetic resonator is investigated. For the case of one atom being initially excited and the cavity mode in the vacuum state it is shown that the atomic time evolution is dominated by the appearance of dark states. These states, in which the initial excitation is stored in the internal atomic degrees of freedom and the atoms become quantum mechanically entangled, are almost immune against photon loss from the cavity. Various properties of the dark states within and beyond the Raman-Nath approximation of atom optics are worked out.

9811035v1

1998-12-17

Coherence properties of the stochastic oscillator

An oscillator with stochastic frequency is discussed as a model for evaluating the quantum coherence properties of a physical system. It is found that the choice of jump statistics has to be considered with care if unphysical consequences are to be avoided. We investigate one such model, evaluate the damping it causes, the decoherence rate and the correlations it results in and the properties of the state for asymptotically long times. Also the choice of initial state is discussed and its effect on the time evolution of the correlations.

9812045v1

1999-04-14

Quantum Langevin theory of excess noise

In an earlier work [P. J. Bardroff and S. Stenholm], we have derived a fully quantum mechanical description of excess noise in strongly damped lasers. This theory is used here to derive the corresponding quantum Langevin equations. Taking the semi-classical limit of these we are able to regain the starting point of Siegman's treatment of excess noise [Phys. Rev. A 39, 1253 (1989)]. Our results essentially constitute a quantum derivation of his theory and allow some generalizations.

9904060v1

1999-05-04

Post-Markov master equation for the dynamics of open quantum systems

A systematic first-order correction to the standard Markov master equation for open quantum systems interacting with a bosonic bath is presented. It extends the Markov Lindblad master equation to the more general case of non-Markovian evolution. The meaning and applications of our `post'-Markov master equation are illustrated with several examples, including a damped two-level atom, the spin-boson model and the quantum Brownian motion model. Limitations of the Markov approximation, the problem of positivity violation and initial slips are also discussed.

9905006v1

1999-06-18

Zeno effect preventing Rabi transitions onto an unstable energy level

We consider a driven 2-level system with one level showing spontaneous decay to an otherwise uncoupled third level. Rabi transitions to the unstable level are strongly damped. This simple configuration can be used to demonstrate and to explore the quantum Zeno effect leading to a freezing of the system to the initial level. A comparison with repeated projection measurements is given. A treatment within a phenomenological theory of continuous measurements is sketched. The system visualizes the important role of null measurements (negative result measurements) and may serve as a good example for a truly continuous measurement.

9906068v1

1999-06-29

Non dissipative decoherence of Rabi oscillations

We present a simple theoretical description of two recent experiments where damping of Rabi oscillations, which cannot be attributed to dissipative decoherence, has been observed. This is obtained considering the evolution time or the Hamiltonian as random variables and then averaging the usual unitary evolution on a properly defined, model-independent, probability distribution.

9906115v3

1999-07-30

Quantum trajectories for Brownian motion

We present the stochastic Schroedinger equation for the dynamics of a quantum particle coupled to a high temperature environment and apply it the dynamics of a driven, damped, nonlinear quantum oscillator. Apart from an initial slip on the environmental memory time scale, in the mean, our result recovers the solution of the known non-Lindblad quantum Brownian motion master equation. A remarkable feature of our approach is its localization property: individual quantum trajectories remain localized wave packets for all times, even for the classically chaotic system considered here, the localization being stronger the smaller $\hbar$.

9907100v1

2000-03-30

Stochastic dynamics of electronic wave packets in fluctuating laser fields

The dynamics of a laser-excited Rydberg electron under the influence of a fluctuating laser field are investigated. Rate equations are developed which describe these dynamics in the limit of large laser bandwidths for arbitrary types of laser fluctuations. These equations apply whenever all coherent effects have already been damped out. The range of validity of these rate equations is investigated in detail for the case of phase fluctuations. The resulting asymptotic power laws are investigated which characterize the long time dynamics of the laser-excited Rydberg electron and it is shown to which extent these power laws depend on details of the laser spectrum.

0003139v1

2000-07-12

Single photon generation by pulsed excitation of a single dipole

The fluorescence of a single dipole excited by an intense light pulse can lead to the generation of another light pulse containing a single photon. The influence of the duration and energy of the excitation pulse on the number of photons in the fluorescence pulse is studied. The case of a two-level dipole with strongly damped coherences is considered. The presence of a metastable state leading to shelving is also investigated.

0007037v1

2000-08-22

Effective Hamiltonian Approach to the Master Equation

A method of exactly solving the master equation is presented in this letter. The explicit form of the solution is determined by the time evolution of a composite system including an auxiliary system and the open system in question. The effective Hamiltonian governing the time evolution of the composed system are derived from the master equation. Two examples, the dissipative two-level system and the damped harmonic oscillator, are presented to illustrate the solving procedure. PACS number(s): 05.30.-d, 05.40.+j, 42.50.Ct

0008090v1

2001-01-01

Quantum-Liouville and Langevin Equations for Gravitational Radiation Damping

From a forward--backward path integral, we derive a master equation for the emission and absorption of gravitons by a massive quantum object in a heat bath of gravitons. Such an equation could describe collapse phenomena of dense stars. We also present a useful approximate Langevin equation for such a system.

0101006v1

2001-02-26

Bateman's dual system revisited: I. Quantization, geometric phase and relation with the ground-state energy of the linear harmonic oscillator

By using the Feynman-Hibbs prescription for the evolution amplitude, we quantize the system of a damped harmonic oscillator coupled to its time-reversed image, known as Bateman's dual system. The time-dependent quantum states of such a system are constructed and discussed entirely in the framework of the classical theory. The corresponding geometric (Pancharatnam) phase is calculated and found to be directly related to the ground-state energy of the 1D linear harmonic oscillator to which the 2D system reduces under appropriate constraint.

0102128v2

2001-03-14

Decoherence effects of motion-induced radiation

The radiation pressure coupling with vacuum fluctuations gives rise to energy damping and decoherence of an oscillating particle. Both effects result from the emission of pairs of photons, a quantum effect related to the fluctuations of the Casimir force. We discuss different alternative methods for the computation of the decoherence time scale. We take the example of a spherical perfectly-reflecting particle, and consider the zero and high temperature limits. We also present short general reviews on decoherence and dynamical Casimir effect.

0103083v1

2001-04-27

Time Evolution of tunneling and decoherence: soluble model

Decoherence effects associated to the damping of a tunneling two-level system are shown to dominate the tunneling probability at short times in strong coupling regimes in the context of a soluble model. A general decomposition of tunneling rates in dissipative and unitary parts is implemented. Master equation treatments fail to describe the model system correctly when more than a single relaxation time is involved.

0104132v1

2001-08-01

Heating and decoherence suppression using decoupling techniques

We study the application of decoupling techniques to the case of a damped vibrational mode of a chain of trapped ions, which can be used as a quantum bus in linear ion trap quantum computers. We show that vibrational heating could be efficiently suppressed using appropriate ``parity kicks''. We also show that vibrational decoherence can be suppressed by this decoupling procedure, even though this is generally more difficult because the rate at which the parity kicks have to applied increases with the effective bath temperature.

0108007v3

2001-11-29

Field quantization for chaotic resonators with overlapping modes

Feshbach's projector technique is employed to quantize the electromagnetic field in optical resonators with an arbitray number of escape channels. We find spectrally overlapping resonator modes coupled due to the damping and noise inflicted by the external radiation field. For wave chaotic resonators the mode dynamics is determined by a non--Hermitean random matrix. Upon including an amplifying medium, our dynamics of open-resonator modes may serve as a starting point for a quantum theory of random lasing.

0111156v2

2001-12-08

Quantum oscillations without quantum coherence

We study numerically the damping of quantum oscillations and the increase of entropy with time in model spin systems decohered by a spin bath. In some experimentally relevant cases, the oscillations of considerable amplitude can persist long after the entropy has saturated near its maximum, i.e. when the system has been decohered almost completely. Therefore, the pointer states of the system demonstrate non-trivial dynamics. The oscillations exhibit slow power-law decay, rather than exponential or Gaussian, and may be observable in experiments.

0112053v1

2001-12-10

Temporal Oscillations of Nonlinear Faraday Rotation in Coherently Driven Media

New phenomenon of temporal oscillations of nonlinear Faraday rotation in a driven four-level system is predicted. We show that in this system with one upper level, under the conditions of electromagnetically induced transparency created by a strong coupling field, the polarization rotation of weak probe light exhibits slowly damped oscillations with a frequency proportional to the strength of an applied magnetic field. This opens up an alternate way to sensitive magnetometric measurements. Applications in low-light nonlinear optics such as photon entanglement are feasible.

0112058v1

2001-12-31

Resonances and spectral properties of detuned OPO pumped by fluctuating sources

Twin beam fluctuations are analyzed for detuned and mismatched OPO configurations. Resonances and frequency responses to the quantum noise sources (quantum and pump amplitude/phase fluctuations) are examined as functions of cavity decay rates, excitation parameter and detuning. The dependence of self- and mutual correlations of beam amplitudes and phases on detuning, mismatch and damping parameters is discussed.

0112180v2

2002-03-04

Stationary cantilever vibrations in the oscillating cantilever-driven adiabatic reversals -- magnetic resonance force microscopy technique

We consider theoretically the novel technique in magnetic resonance force microscopy which is called ``oscillating cantilever-driven adiabatic reversals''. We present analytical and numerical analysis for the stationary cantilever vibrations in this technique. For reasonable values of parameters we estimate the resonant frequency shift as 6Hz per the Bohr magneton. We analyze also the regime of small oscillations of the paramagnetic moment near the transversal plane and the frequency shift of the damped cantilever vibrations.

0203013v1

2002-05-17

Embedding dissipation and decoherence in unitary evolution schemes

Dissipation and decoherence, and the evolution from pure to mixed states in quantum physics are handled through master equations for the density matrix. By embedding elements of this matrix in a higher-dimensional Liouville-Bloch equation, the methods of unitary integration are adapted to solve for the density matrix as a function of time, including the non-unitary effects of dissipation and decoherence. The input requires only solutions of classical, initial value time-dependent equations. Results are illustrated for a damped driven two-level system.

0205113v3

2002-05-31

Invitation to quantum dynamical semigroups

The theory of quantum dynamical semigroups within the mathematically rigorous framework of completely positive dynamical maps is reviewed. First, the axiomatic approach which deals with phenomenological constructions and general mathematical structures is discussed. Then basic derivation schemes of the constructive approach including singular coupling, weak coupling and low density limits are presented in their higly simplified versions. Two-level system coupled to a heat bath, damped harmonic oscillator, models of decoherence, quantum Brownian particle and Bloch-Boltzmann equations are used as illustrations of the general theory. Physical and mathematical limitations of the quantum open system theory, the validity of Markovian approximation and alternative approaches are discussed also.

0205188v1

2002-06-14

An Inverse-Problem Approach to Designing Photonic Crystals for Cavity QED Experiments

Photonic band gap (PBG) materials are attractive for cavity QED experiments because they provide extremely small mode volumes and are monolithic, integratable structures. As such, PBG cavities are a promising alternative to Fabry-Perot resonators. However, the cavity requirements imposed by QED experiments, such as the need for high Q (low cavity damping) and small mode volumes, present significant design challenges for photonic band gap materials. Here, we pose the PBG design problem as a mathematical inversion and provide an analytical solution for a two-dimensional crystal. We then address a planar (2D crystal with finite thickness) structure using numerical techniques.

0206094v1

2002-06-17

Damped Bloch oscillations of cold atoms in optical lattices

The paper studies Bloch oscillations of cold neutral atoms in the optical lattice. The effect of spontaneous emission on the dynamics of the system is analyzed both analytically and numerically. The spontaneous emission is shown to cause (i) the decay of Bloch oscillations with the decrement given by the rate of spontaneous emission and (ii) the diffusive spreading of the atoms with a diffusion coefficient depending on {\em both} the rate of spontaneous emission and the Bloch frequency.

0206108v1