共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Pumir V.V. Barelko 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(1):137-145
Fast self sustained waves of chemical or phase transformations, observed in several contexts in condensed matter effectively
result in “gasless detonation". The phenomenon is modelled by coupling the reaction diffusion equation, describing chemical
or phase transformations, and the wave equation, describing elastic perturbations. The coupling considered in this work involves
(i) a dependence of the sound velocity on the chemical (phase) field, and (ii) the destruction of the initial chemical equilibrium
when the strain exceeds a critical value (strain induced phase transition). Both the case of an initially unstable state (first
order kinetics) and metastable state (second order kinetics) are considered. An exhaustive analytic and numerical study of
travelling waves reveals the existence of supersonic modes of transformations. The practically important problem of ignition
of fast waves by mechanical perturbation is investigated. With the present model, the critical strain necessary to ignite
gasless detonation by local perturbations is determined.
Received 18 November 1999 相似文献
2.
A. Pumir V.V. Barelko 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):379-383
Fast self sustained waves (autowaves) associated with chemical or phase transformations are observed in many situations in
condensed matter. They are governed neither by diffusion of matter or heat (as in combustion processes) nor by a travelling
shock wave (as in gaseous detonation). Instead, they result from a coupling between phase transformation and the stress field,
and may be classified as gasless detonation autowaves in solids. We propose a simple model to describe these regimes. The
model rests on the classical equations of elastic deformations in a 1-dimensional solid bar, with the extra assumption that
the phase (chemical) transformation induces a change of the sound velocity. The transformations are assumed to occur through
a chain branched mechanism, which starts when the mechanical stress exceeds a given threshold. Our investigation shows that
supersonic autowaves exist in this model. In the absence of diffusion (dissipation factor, losses), a continuum of travelling
wave solutions is found. In the presence of diffusion, a steady state supersonic wave solution is found, along with a slower
wave controlled by diffusion.
Received 15 October 1998 相似文献
3.
F. Leyvraz H. Larralde D. P. Sanders 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):57-61
A definition of metastable states applicable to arbitrary finite
state Markov processes satisfying detailed balance is discussed. In
particular, we identify a crucial condition that distinguishes
genuine metastable states from other types of slowly decaying modes
and which leads to properties similar to those postulated in the
restricted ensemble approach [1]. The intuitive physical
meaning of this condition is simply that the total equilibrium
probability of finding the system in the metastable state is
negligible. As a concrete application of our formalism we present
preliminary results on a 2D kinetic Ising model. 相似文献
4.
R. Cafiero A. Valleriani J.L. Vega 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(4):405-408
We study the behavior under perturbations in the, recently introduced, Bak-Sneppen model with deterministic updating. We focus
our attention on the damage-spreading features and show that the value of the growth exponent for the distance, , coincides with that of the random updating Bak-Sneppen model. Moreover, we generalize this analysis by considering a broader
set of initial perturbations for which the value of is preserved.
Received: 24 June 1998 / Accepted: 9 July 1998 相似文献
5.
R. Cafiero A. Valleriani J.L. Vega 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):505-508
We study the behavior under perturbations of the Parallel Bak-Sneppen model (PBS) in 1+1 dimension, which has been shown to
belong to the universality class of Directed Percolation (DP) in 1+1 dimensions [#!SD96!#]. We focus our attention on the
damage-spreading features of the PBS model with both random and deterministic updating, which are studied and compared to
the known results for the extremal Bak-Sneppen model (BS) and for DP. For both random and deterministic updating, we observe
a power law growth of the Hamming distance. In addition, we compute analytically the asymptotic plateau reached by the distance
after the growing phase.
Received: 24 September 1998 / Revised: 17 November 1998 / Accepted: 19 November
1998 相似文献
6.
F.A. Tamarit S.A. Cannas C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(4):545-548
We consider biological evolution as described within the Bak and Sneppen 1993 model. We exhibit, at the self-organized critical
state, a power-law sensitivity to the initial conditions, calculate the associated exponent, and relate it to the recently
introduced nonextensive thermostatistics. The scenario which here emerges without tuning strongly reminds of that of the tuned onset of chaos in say logistic-like one-dimensional maps. We also calculate the dynamical exponent z.
Received: 5 November 1997 / Received in final form: 11 November 1997 / Accepted: 19 November 1997 相似文献
7.
Anomalous scaling in the Zhang model 总被引:2,自引:0,他引:2
R. Pastor-Satorras A. Vespignani 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):197-200
We apply the moment analysis technique to analyze large scale simulations of the Zhang sandpile model. We find that this model
shows different scaling behavior depending on the update mechanism used. With the standard parallel updating, the Zhang model
violates the finite-size scaling hypothesis, and it also appears to be incompatible with the more general multifractal scaling
form. This makes impossible its affiliation to any one of the known universality classes of sandpile models. With sequential
updating, it shows scaling for the size and area distribution. The introduction of stochasticity into the toppling rules of
the parallel Zhang model leads to a scaling behavior compatible with the Manna universality class.
Received 8 August 2000 and Received in final form 4 October 2000 相似文献
8.
R.E. Nettleton 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(3):429-437
Robertson has found a projection operator which, applied to the Liouville equation, yields an exact equation for , the information-theoretic phase-space distribution. If the Robertson equation is multiplied by a set [0pt]{} of functions representing physical fluxes, odd under momentum reversal and even under configuration inversion, a set of
evolution equations is obtained for time-dependent ensemble averages which are variables of extended thermodynamics. In earlier work, a perturbation calculation was developed, assuming just
one variable , for an operator [0pt] occurring in the Robertson equation. This calculation is extended here to the case where there are variables. The coefficients in the evolution equations depend on {} and explicitly on time t at short times. It is shown here that these coefficients exhibit Onsager symmetry at long times, after the transient explicit
t-dependence has disappeared, to .
Received 13 September 1999 and Received in final form 4 April 2000 相似文献
9.
Y. Chen S.H. Guo Z.B. Li S. Marculescu L. Schülke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):289-296
The renormalisation group approach is applied to the study of the short-time critical behaviour of the d-dimensional Ginzburg-Landau model with long-range interaction of the form in momentum space. Firstly the system is quenched from a high temperature to the critical temperature and then relaxes to
equilibrium within the model A dynamics. The asymptotic scaling laws and the initial slip exponents and of the order parameter and the response function respectively, are calculated to the second order in .
Received 9 June 2000 and Received in final form 2 August 2000 相似文献
10.
Olson Reichhardt CJ Reichhardt C Bishop AR 《The European physical journal. E, Soft matter》2007,22(1):11-15
Motivated by recent experiments on colloidal systems with
competing attractive and repulsive interactions,
we simulate a two-dimensional system of colloids
with competing interactions that can undergo fragmentation.
In the absence of any
other confining potential, the colloids can form stable clusters
depending on the strength of the short range attractive term.
By suddenly changing the strength of one of the interaction
terms we
find a rich variety of fragmentation behavior which is affected
by the existence of “magic” cluster numbers.
Such soft matter systems can
be used to construct artificial nuclei. 相似文献
11.
H.M. Ohlenbusch T. Aste B. Dubertret N. Rivier 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):211-220
We analyze the structure of two dimensional disordered cellular systems generated by extensive computer simulations. These
cellular structures are studied as topological trees rooted on a central cell or as closed shells arranged concentrically
around a germ cell. We single out the most significant parameters that characterize statistically the organization of these
patterns. Universality and specificity in disordered cellular structures are discussed.
Received: 23 September 1997 / Received in final form: 14 January 1998
/ Accepted: 29 January 1998 相似文献
12.
Tamás S. Bíró 《Physics letters. A》2008,372(8):1174-1179
We study the process of equilibration between two non-extensive subsystems in the framework of a particular non-extensive Boltzmann equation. We have found that even subsystems with different non-extensive properties achieve a common equilibrium distribution. We extract the thermodynamic temperature from final energy distributions in a particular case. 相似文献
13.
R. E. Nettleton 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(2):287-292
Jaynesian statistical inference is used to predict that steady, non-uniform Couette flow in a simple liquid will generate
a heat flux proportional to the gradient of the square of the strain-rate when the temperature gradient is negligible. The
heat flux is divided into phonon and self-diffusion components, with the latter coupling to the elastic strain and inelastic
strain-rate. Operators for all these are substituted into the information-theoretic phase-space distribution. By taking moments
of an exact equation for this distribution derived by Robertson, one obtains an evolution equation for the self-diffusion
component of the heat flux which, in a steady state, predicts shear-driven heat flow.
Received 10 September 1998 相似文献
14.
J.-C. Lasjaunias K. Biljaković D. Starešinić P. Monceau S. Takasaki J. Yamada S.-I. Nakatsuji H. Anzai 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):541-550
We report on specific heat measurements of the quasi-one-dimensional organic salt (TMTSF)2AsF6 in its spin density wave state between 75 mK and 7 K. Similarly to (TMTSF)2PF6, we find discontinuities in the lattice contribution at 1.9 K an d 3.5 K ascribed to sub-spin density wave phases. Time-dependent
effects due to dynamics of low-energy excitations in metastable states occur only below 0.2 K which yields an activation energy
for the equilibrium energy relaxation process of 0.34 K, 4-5 times smaller than found for (TMTSF)2PF6. Finally the reduction of the low-energy excitations contribution to the specific heat in comparison to PF6 reveals an intermediate cubic-like regime between 0.25 and 0.5 K that we tentatively describe as the phason contribution
of the incommensurate spin density wave modulation.
Received: 17 March 1998 / Revised: 27 July 1998 / Accepted: 22 September 1998 相似文献
15.
Y. Kafri D. Biron M.R. Evans D. Mukamel 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):669-676
The coarsening process in a class of driven systems is studied. These systems have previously been shown to exhibit phase
separation and slow coarsening in one dimension. We consider generalizations of this class of models to higher dimensions.
In particular we study a system of three types of particles that diffuse under local conserving dynamics in two dimensions.
Arguments and numerical studies are presented indicating that the coarsening process in any number of dimensions is logarithmically
slow in time. A key feature of this behavior is that the interfaces separating the various growing domains are macroscopically
smooth (well approximated by a Fermi function). This implies that the coarsening mechanism in one dimension is readily extendible
to higher dimensions.
Received 3 April 2000 相似文献
16.
17.
S. Ispolatov P.L. Krapivsky S. Redner 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):267-276
A model for the evolution of the wealth distribution in an economically interacting population is introduced, in which a specified
amount of assets are exchanged between two individuals when they interact. The resulting wealth distributions are determined
for a variety of exchange rules. For “random” exchange, either individual is equally likely to gain in a trade, while “greedy”
exchange, the richer individual gains. When the amount of asset traded is fixed, random exchange leads to a Gaussian wealth
distribution, while greedy exchange gives a Fermi-like scaled wealth distribution in the long-time limit. Multiplicative processes
are also investigated, where the amount of asset exchanged is a finite fraction of the wealth of one of the traders. For random
multiplicative exchange, a steady state occurs, while in greedy multiplicative exchange a continuously evolving power law
wealth distribution arises.
Received: 13 August 1997 / Revised: 31 December 1997 / Accepted: 26
January 1998 相似文献
18.
E. Katzav 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):137-140
In the paper the role of long range interactions on the
growth of a volume conserving surface is studied using the Nonlocal
Conserved Kardar-Parisi-Zhang (NCKPZ) equation. It is shown that
previous theoretical predictions are inconsistent with an exact
one-dimensional result. This serves as a motivation for construction
of a Self-Consistent Expansion (SCE) that recovers the exact
one-dimensional result, and gives the scaling exponents in higher
dimensions as well. A possible application of this result to
colloidal systems is discussed. 相似文献
19.
B. Drossel K. Dahmen 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(4):485-496
We report studies of the behaviour of a single driven domain wall in the 2-dimensional non-equilibrium zero temperature random-field
Ising model, closely above the depinning threshold. It is found that even for very weak disorder, the domain wall moves through
the system in percolative fashion. At depinning, the fraction of spins that are flipped by the proceeding avalanche vanishes
with the same exponent as the infinite percolation cluster in percolation theory. With decreasing disorder strength, however, the size of the critical
region decreases. Our numerical simulation data appear to reflect a crossover behaviour to an exponent at zero disorder strength. The conclusions of this paper strongly rely on analytical arguments. A scaling theory in terms
of the disorder strength and the magnetic field is presented that gives the values of all critical exponent except for one,
the value of which is estimated from scaling arguments.
Received: 13 February 1998 / Accepted: 30 March 1998 相似文献
20.
K. Schenk B. Drossel S. Clar F. Schwabl 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):177-185
We study finite-size effects in the self-organized critical forest-fire model by numerically evaluating the tree density and
the fire size distribution. The results show that this model does not display the finite-size scaling seen in conventional
critical systems. Rather, the system is composed of relatively homogeneous patches of different tree densities, leading to
two qualitatively different types of fires: those that span an entire patch and those that do not. As the system size becomes
smaller, the system contains less patches, and finally becomes homogeneous, with large density fluctuations in time.
Received 24 April 1999 and Received in final form 26 October 1999 相似文献