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1.
Evidence is presented that diffusion drives colliding many-particle systems at relativistic energies from the initial δ–functions
in rapidity towards the equilibrium distribution. Analytical solutions of a linear Fokker-Planck equation represent rapidity
spectra for participant protons in central heavy-ion collisions at SPS-energies accurately. Thermal equilibrium in the interaction
region is not attained, nonequilibrium features persist and can account for the broad rapidity spectra.
Received: 24 November 1998 / Revised version: 20 February 1999 相似文献
2.
E.V. Votyakov A. De Martino D.H.E. Gross 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):593-603
We investigate the statistical equilibrium properties of a system of classical particles interacting via Newtonian gravity, enclosed in a three-dimensional spherical volume. Within a mean-field approximation, we derive an equation
for the density profiles maximizing the microcanonical entropy and solve it numerically. At low angular momenta, i.e. for a slowly rotating system, the well-known gravitational collapse “transition” is recovered. At higher angular momenta,
instead, rotational symmetry can spontaneously break down giving rise to more complex equilibrium configurations, such as
double-clusters (“double stars”). We analyze the thermodynamics of the system and the stability of the different equilibrium
configurations against rotational symmetry breaking, and provide the global phase diagram.
Received 8 July 2002 Published online 15 October 2002
RID="a"
ID="a"e-mail: demartino@hmi.de 相似文献
3.
Recent experiments have demonstrated that the dynamics in liquids close to the glass transition temperature is strongly heterogeneous.
The characteristic size of these heterogeneities has been measured to be a few nanometers at T
g. We extend here a recent model for describing the heterogeneous nature of the dynamics which allows both to derive this length
scale and the right orders of magnitude of the heterogeneities of the dynamics close to the glass transition. Our model allows
then to interpret quantitatively small probes diffusion experiments.
Received 29 March 2002 and Received in final form 11 November 2002
RID="a"
ID="a"e-mail: long@lps.u-psud.fr 相似文献
4.
S. Mossa E. La Nave F. Sciortino P. Tartaglia 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):351-355
The equation of state for a liquid in equilibrium, written in the potential energy landscape formalism, is generalized to
describe out-of-equilibrium conditions. The hypothesis that during aging the system explores basins associated to equilibrium
configurations is the key ingredient in the derivation. Theoretical predictions are successfully compared with data from molecular
dynamics simulations of different aging processes, such as temperature and pressure jumps.
Received 7 August 2002 / Received in final form 8 October 2002
Published online 19 December 2002
RID="a"
ID="a"Present address: Laboratoire de Physique Théorique des Liquides, Université Pierre et Marie Curie, 4 place Jussieu, Paris 75005, France e-mail:
mossa@lptl.jussieu.fr 相似文献
5.
A.K. Chattopadhyay 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):567-576
We study the dynamics of a growing crystalline facet where the growth mechanism is controlled by the geometry of the local
curvature. A continuum model, in (2+1) dimensions, is developed in analogy with the Kardar-Parisi-Zhang (KPZ) model is considered
for the purpose. Following standard coarse graining procedures, it is shown that in the large time, long distance limit, the
continuum model predicts a curvature independent KPZ phase, thereby suppressing all explicit effects of curvature and local
pinning in the system, in the “perturbative” limit. A direct numerical integration of this growth equation, in 1+1 dimensions,
supports this observation below a critical parametric range, above which generic instabilities, in the form of isolated pillared
structures lead to deviations from standard scaling behaviour. Possibilities of controlling this instability by introducing
statistically “irrelevant" (in the sense of renormalisation groups) higher ordered nonlinearities have also been discussed.
Received 23 April 2002 / Received in final form 24 July 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: akc@mpipks-dresden.mpg.de 相似文献
6.
Z.F. Huang S. Solomon 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(4):601-607
We study by theoretical analysis and by direct numerical simulation the dynamics of a wide class of asynchronous stochastic
systems composed of many autocatalytic degrees of freedom. We describe the generic emergence of truncated power laws in the
size distribution of their individual elements. The exponents α of these power laws are time independent and depend only on
the way the elements with very small values are treated. These truncated power laws determine the collective time evolution
of the system. In particular the global stochastic fluctuations of the system differ from the normal Gaussian noise according
to the time and size scales at which these fluctuations are considered. We describe the ranges in which these fluctuations
are parameterized respectively by: the Lévy regime α < 2, the power law decay with large exponent ( α > 2), and the exponential
decay. Finally we relate these results to the large exponent power laws found in the actual behavior of the stock markets
and to the exponential cut-off detected in certain recent measurement.
Received 29 July 2000 and Received in final form 25 September 2000 相似文献
7.
C.M. Horowitz E.V. Albano 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):563-569
The relationship between a microscopic parameter p, that is related to the probability of choosing a mechanism of deposition, and the stochastic equation for the interface's
evolution is studied for two different models. It is found that in one model, that is similar to ballistic deposition, the
corresponding stochastic equation can be represented by a Kardar-Parisi-Zhang (KPZ) equation where both λ and ν depend on
p in the following way: ν(p) = νp and λ(p) = λp
3/2. Furthermore, in the other studied model, which is similar to random deposition with relaxation, the stochastic equation
can be represented by an Edwards-Wilkinson (EW) equation where ν depends on p according to ν(p) = νp
2. It is expected that these results will help to find a framework for the development of stochastic equations starting from
microscopic details of growth models.
Received 26 August 2002 / Received in final form 20 November 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: ealbano@inifta.unlp.edu.ar 相似文献
8.
9.
J. Le Cochec F. Ladieu 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(1):13-26
We have calculated the real part of the nonlinear dielectric susceptibility of amorphous insulators in the kHz range, by using the two-level system model
and a nonperturbative numerical quantum approach. At low temperature T, it is first shown that the standard two-level model should lead to a decrease of when the measuring field E is raised, since raising E increases the population of the upper level and induces Rabi oscillations cancelling the ones induced from the ground level.
This predicted E-induced decrease of is at odds with experiments. However, a better, though still not perfect, agreement with low-frequency experimental nonlinear data is
recovered if, in our fully quantum simulations, interactions between defects are taken into account by a new relaxation rate
whose efficiency increases as , as was proposed recently by Burin et al. [Phys. Rev. Lett. 86, 5616 (2001)]. In this approach, the behavior of at low T is mainly explained by the efficiency of this new relaxation channel. Since a quantitative understanding of glasses is still missing, we finally discuss experiments whose results should yield a refined understanding
of this new relaxation mechanism: i) a completely new nonlinear behavior should be found for samples whose thickness is ≃
10 nm; ii) a decrease of nonequilibrium effects should be found when E is increased.
Received 19 September 2002 / Received in final form 4 December 2002 Published online 14 March 2003 相似文献
10.
Nonlinear dielectric response of antiferroelectric liquid crystals has been studied in the smectic Cα* (SmCα*) phase. The linear dielectric spectrum shows a single relaxation of Debye type and its relaxation frequency is as high as
one hundred kHz. The profile of the third-order nonlinear dielectric spectrum varies in complex fashion with temperature.
In the vicinity of the SmA-SmCα* phase transition, experimentally obtained nonlinear spectra are well described by those calculated with phenomenological
theory of Landau type. The soft mode of the SmCα* phase shows critical slowing-down near the transition temperature. In the lower-temperature region of the SmCα* phase, the contribution from the soft mode of the SmCα* phase reduces and the other relaxation mode with Debye-type spectrum appears at several hundred Hz in the nonlinear spectrum.
The appearance of this low-frequency mode suggests that the cooperative fluctuation of directors over long range exists in
the SmCα* phase.
Received 19 April 2002 and Received in final form 23 July 2002
RID="a"
ID="a"e-mail: kimura@exp.t.u-tokyo.ac.jp 相似文献
11.
R. Percacci A. Vespignani 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):411-414
Measurements and data analysis have proved very effective in the study of the Internet's physical fabric and have shown heterogeneities
and statistical fluctuations extending over several orders of magnitude. Here we focus on the relationship between the Round-Trip-Time
(RTT) and the geographical distance. We define dimensionless variables that contain information on the quality of Internet
connections finding that their probability distributions are characterized by a slow power-law decay signalling the presence
of scale-free features. These results point out the extreme heterogeneity of Internet delay since the transmission speed between
different points of the network exhibits very large fluctuations. The associated scaling exponents appear to have fairly stable
values in different data sets and thus define an invariant characteristic of the Internet that might be used in the future
as a benchmark of the overall state of “health” of the Internet.
Received 25 January 2003 Published online 7 May 2003 相似文献
12.
S. Aumaître S. Fauve S. McNamara P. Poggi 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):449-460
We consider three examples of dissipative dynamical systems involving many degrees of freedom, driven far from equilibrium
by a constant or time dependent forcing. We study the statistical properties of the injected and dissipated power as well
as the fluctuations of the total energy of these systems. The three systems under consideration are: a shell model of turbulence,
a gas of hard spheres colliding inelastically and excited by a vibrating piston, and a Burridge-Knopoff spring-block model.
Although they involve different types of forcing and dissipation, we show that the statistics of the injected power obey the
“fluctuation theorem" demonstrated in the case of time reversible dissipative systems maintained at constant total energy,
or in the case of some stochastic processes. Although this may be only a consequence of the theory of large deviations, this
allows a possible definition of “temperature" for a dissipative system out of equilibrium. We consider how this “temperature"
scales with the energy and the number of degrees of freedom in the different systems under consideration.
Received 26 June 2000 and Received in final form 24 October 2000 相似文献
13.
The spatial confinement of a fluctuation spectrum leads to forces at the confining boundaries. While electromagnetic (EM)
fluctuations lead to the well-known dispersion forces, the acoustic analogy has widely been neglected. We show that the strength
of the forces resulting from confined acoustic modes may be of the same order of magnitude as van der Waals forces. Additionally,
the predicted scaling behavior is identical to the non-retarded case of the EM fluctuations. Our results suggest that dewetting
experiments using polymer films are strongly influenced by the acoustic dispersion forces.
Received 5 March 2002 and Received in final form 21 May 2002 相似文献
14.
M. Johansson A.M. Morgante S. Aubry G. Kopidakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):279-283
Modulational instability of travelling plane waves is often considered as the first step in the formation of intrinsically
localized modes (discrete breathers) in anharmonic lattices. Here, we consider an alternative mechanism for breather formation,
originating in oscillatory instabilities of spatially periodic or quasiperiodic nonlinear standing waves (SWs). These SWs
are constructed for Klein-Gordon or Discrete Nonlinear Schr?dinger lattices as exact time periodic and time reversible multibreather
solutions from the limit of uncoupled oscillators, and merge into harmonic SWs in the small-amplitude limit. Approaching the
linear limit, all SWs with nontrivial wave vectors (0 < Q < π) become unstable through oscillatory instabilities, persisting for arbitrarily small amplitudes in infinite lattices.
The dynamics resulting from these instabilities is found to be qualitatively different for wave vectors smaller than or larger
than π/2, respectively. In one regime persisting breathers are found, while in the other regime the system thermalizes.
Received 6 October 2001 / Received in final form 1st March 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: mjn@ifm.liu.se 相似文献
15.
Y. Jiang O. Jedrkiewicz S. Minardi P. DiTrapani A. Mosset E. Lantz F. Devaux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):521-526
The pixel by pixel calibration of a scientific CCD camera allows Poissonian statistics of the spatial fluctuations of an uniform
enlightening to be retrieved in the full range of the camera dynamic. The procedure works efficiently for thermal as well
as for laser sources, provided that the wavelength and the coherence properties of the source are chosen in order to avoid
the formation of equal thickness fringes in the chip (etaloning effect). Calibration allows also the comparison at the shot
noise level of images recorded at different places on the chip.
Received 9 September 2002 / Received in final form 16 October 2002 Published online 21 January 2003 相似文献
16.
I.M. Mladenov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):327-330
The general shape equation describing the forms of vesicles is a highly nonlinear partial differential equation for which
only a few explicit solutions are known. These solvable cases are briefly reviewed and a new analytical solution which represents
the class of the constant mean curvature surfaces is described. Pearling states of the tubular fluid membranes can be explained
as a continuous deformation preserving membrane mean curvature.
Received 2 February 2002 / Received in final form 4 February 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: mladenov@obzor.bio21.bas.bg 相似文献
17.
S. Villain-Guillot C. Josserand 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):305-309
We develop a new technique describing the non linear growth of interfaces. We apply this analytical approach to the one dimensional
Cahn-Hilliard equation. The dynamics is captured through a solvability condition performed over a particular family of quasi-static
solutions. The main result is that the dynamics along this particular class of solutions can be expressed in terms of a simple
ordinary differential equation. The density profile of the stationary regime found at the end of the non-linear growth is
also well characterized. Numerical simulations are compared in a satisfactory way with the analytical results through three
different fitting methods and asymptotic dynamics are well recovered, even far from the region where the approximations hold.
Received 16 October 2001 / Received in final form 15 March 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: josseran@lmm.jussieu.fr
RID="b"
ID="b"UMR CNRS 7607 相似文献
18.
Mattioni L Wittmer JP Baschnagel J Barrat JL Luijten E 《The European physical journal. E, Soft matter》2003,10(4):369-385
Correlations in the motion of reptating polymers in a melt are investigated by means of Monte Carlo simulations of the three-dimensional
slithering-snake version of the bond-fluctuation model. Surprisingly, the slithering-snake dynamics becomes inconsistent with
classical reptation predictions at high chain overlap (created either by chain length N or by the volume fraction φ of occupied lattice sites), where the relaxation times increase much faster than expected. This
is due to the anomalous curvilinear diffusion in a finite time window whose upper bound (N) is set by the density of chain ends φ/N. Density fluctuations created by passing chain ends allow a reference polymer to break out of the local cage of immobile
obstacles created by neighboring chains. The dynamics of dense solutions of “snakes” at t ≪ is identical to that of a benchmark system where all chains but one are frozen. We demonstrate that the subdiffusive dynamical
regime is caused by the slow creeping of a chain out of its correlation hole. Our results are in good qualitative agreement
with the activated-reptation scheme proposed recently by Semenov and Rubinstein (Eur. Phys. J. B, 1 (1998) 87). Additionally, we briefly comment on the relevance of local relaxation pathways within a slithering-snake scheme.
Our preliminary results suggest that a judicious choice of the ratio of local to slithering-snake moves is crucial to equilibrate
a melt of long chains efficiently.
Received: 18 December 2002 / Accepted: 3 April 2003 / Published online: 12 May 2003
RID="a"
ID="a"e-mail: jwittmer@dpm.univ-lyon1.fr
RID="b"
ID="b"Current address: University of Illinois at Urbana-Champaign. 相似文献
19.
S. Longhi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):57-66
Multiphase patterns are found in a mean-field model of a singly-resonant optical parametric oscillator that converts a pump
field at frequency 3ω into signal and idler fields at frequencies 2ω and ω. A complex Ginzburg-Landau equation without diffusion
and with a quadratic phase-sensitive nonlinear term is derived under single-longitudinal and paraxial propagation approximations.
Owing to the phase-matched multistep parametric process ω + ω = 2ω, phase locking of the resonated signal field is possible
with three distinct phase states. Three-armed rotating spirals, target patterns and light filamentation are found by a numerical
analysis of the mean-field equation.
Received 19 April 2001 and Received in final form 21 June 2001 相似文献
20.
S.E. Guidoni H.O. Mártin C.M. Aldao 《The European physical journal. E, Soft matter》2002,7(3):291-295
We present a one-dimensional Monte Carlo simulation for the diffusion motion of a chain of N beads. We found that the scaling exponent for the viscosity can be smaller or greater than 3. This anomalous behavior cannot be attributed to the diffusivity scaling or the length fluctuations but is due to the chain dynamics details
during diffusion in which the end beads play the key role. The viscosity exponent 3 and its expected relation with the diffusivity
exponent are recovered in the asymptotic regime (N ↦∞).
Received 24 September 2001 and Received in final form 28 January 2002 相似文献