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1.
M. A. Fuentes H. S. Wio 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):249-253
With the aim of studying stochastic resonance (SR) in a
double-well potential when the noise source has a spectral density
of the form f-κ (with varying κ), we have extended
a procedure introduced by Kaulakys et al. (Phys. Rev. E 70,
020101 (2004)). In order to achieve an analytical understanding of
the results, we have obtained an effective Markovian approximation
that allows us to make a systematic study of the effect of such
noise on the SR phenomenon. A comparison of the numerical and
analytical results shows an excellent qualitative agreement
indicating that the effective Markovian approximation is able to
correctly describe the general trends. 相似文献
2.
M.A.R. de Cara O. Pla F. Guinea 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(1):187-191
The El Farol bar model, proposed to study the dynamics of competition of agents in a variety of contexts (W.B. Arthur, Amer. Econ. Assoc.
Pap. Proc. 84, 406 (1994)) is studied. We characterize in detail the three regions of the phase diagram (efficient, better than random
and inefficient) of the simplest version of the model (D. Challet, Y.-C. Zhang, Physica A 246, 407 (1997)). The efficient region is shown to have a rich structure, which is investigated in some detail. Changes in the
payoff function enhance further the tendency of the model towards a wasteful distribution of resources.
Received 13 November 1998 相似文献
3.
4.
S. Risau-Gusman G. Abramson 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):515-520
We analyze general two-species stochastic models, of the
kind generally used for the study of population dynamics. Although
usually defined a priori, the deterministic version of these
models can be obtained as the infinite volume limit of many
stochastic models (which are necessarily defined by more parameters
than the deterministic one). It is known that damped oscillations in
a deterministic model usually correspond to oscillatory-like
fluctuations in their deterministic counterparts. The quality of
these “oscillations" depends on details of each stochastic model.
We show, however, that the parameters of the deterministic system
are generally enough to obtain very good bounds for the quality of
“oscillations" in any of its stochastic counterparts. These
bounds are shown to depend on only one dimensionless parameter. 相似文献
5.
M. Khorrami A. Aghamohammadi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):223-227
A system of particles is studied in which the stochastic
processes are one-particle type-change (or one-particle diffusion)
and multi-particle annihilation. It is shown that, if the
annihilation rate tends to zero but the initial values of the
average number of the particles tend to infinity, so that the
annihilation rate times a certain power of the initial values of
the average number of the particles remain constant (the double
scaling) then if the initial state of the system is a
multi-Poisson distribution, the system always remains in a state
of multi-Poisson distribution, but with evolving parameters. The
large time behavior of the system is also investigated. The system
exhibits a dynamical phase transition. It is seen that for a
k-particle annihilation, if k is larger than a critical value
kc, which is determined by the type-change rates,
then annihilation does not enter the relaxation exponent of the
system; while for k < kc, it is the annihilation (in
fact k itself) which determines the relaxation exponent. 相似文献
6.
R. Mingesz Z. Gingl P. Makra 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):339-344
On the basis of our mixed-signal simulations we report significant stochastic resonance induced input-output signal improvement
in the double-well system for aperiodic input types. We used a pulse train with randomised pulse locations and a band-limited
noise with low cut-off frequency as input signals, and applied a cross-spectral measure to quantify their noise content. We
also supplemented our examinations with simulations in the Schmitt trigger to show that the signal improvement we obtained
is not a result of a potential filtering effect due to the limited response time of the double-well dynamics. 相似文献
7.
T. Aspelmeier J. Magnin W. Graupner U.C. Täuber 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):441-450
We investigate random walks on a lattice with imperfect traps. In one dimension, we perturbatively compute the survival probability
by reducing the problem to a particle diffusing on a closed ring containing just one single trap. Numerical simulations reveal
this solution, which is exact in the limit of perfect traps, to be remarkably robust with respect to a significant lowering
of the trapping probability. We demonstrate that for randomly distributed traps, the long-time asymptotics of our result recovers
the known stretched exponential decay. We also study an anisotropic three-dimensional version of our model. We discuss possible
applications of some of our findings to the decay of excitons in semiconducting organic polymer materials, and emphasize the
crucial influence of the spatial trap distribution on the kinetics.
Received 23 July 2001 / Received in final form 14 May 2002 Published online 13 August 2002 相似文献
8.
R. M. D'Souza P. L. Krapivsky C. Moore 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(4):535-543
The “power of choice” has been shown to radically alter the behavior of a number of
randomized algorithms. Here we explore the effects of choice on models of random tree growth.
In our models each new node has k randomly chosen contacts, where k > 1 is a constant.
It then attaches to whichever one of these contacts is most desirable in some sense, such as its
distance from the root or its degree. Even when the new node has just two choices,
i.e., when k = 2, the resulting tree can be very different from a random graph or tree. For instance,
if the new node attaches to the contact which is closest to the root of the tree, the
distribution of depths changes from Poisson to a traveling wave solution.
If the new node attaches to the contact with the smallest degree, the degree distribution
is closer to uniform than in a random graph, so that with high probability there are no nodes in the
tree with degree greater than O(log log N). Finally, if the new node attaches to the contact
with the largest degree, we find that the degree distribution is a power law with exponent -1
up to degrees roughly equal to k, with an exponential cutoff beyond that; thus, in this case,
we need k ≫ 1 to see a power law over a wide range of degrees. 相似文献
9.
Solomon Fekade Mulugeta Bekele 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):369-374
We analyze the relaxation behavior of a bistable system when the background temperature profile is inhomogeneous due to the
presence of a localized hot region (blowtorch) on one side of the potential barrier. Since the diffusion equation for inhomogeneous
medium is model-dependent, we consider two physical models to study the kinetics of such system. Using a conventional stochastic
method, we obtain the escape and equilibration rates of the system for the two physical models. For both models, we find that
the hot region enhances the escape rate from the well where it is placed while it retards the escape rate from the other well. However, the value of the escape rate from the well where the hot region is placed differs
for the two models while that of the escape rate from the other well is identical for both. This work, for the first time,
gives a detailed report of the similarities and differences of the escape rates and, hence, exposes the common and distinct
features of the two known physical models in determining the way the bistable system relaxes.
Received 25 September 2001 相似文献
10.
L. F. Matin A. Aghamohammadi M. Khorrami 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):243-246
The most general reaction-diffusion model on a Cayley
tree with nearest-neighbor interactions is introduced, which can
be solved exactly through the empty-interval method. The
stationary solutions of such models, as well as their dynamics,
are discussed. Concerning the dynamics, the spectrum of the
evolution Hamiltonian is found and shown to be discrete, hence
there is a finite relaxation time in the evolution of the system
towards its stationary state. 相似文献
11.
Exactly solvable models through the generalized empty interval method,for multi-species interactions
A. Aghamohammadi M. Alimohammadi M. Khorrami 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):371-378
Multi-species reaction-diffusion systems, with nearest-neighbor interaction on a one-dimensional lattice are considered. Necessary
and sufficient constraints on the interaction rates are obtained, that guarantee the closedness of the time evolution equation
for E
n(t)'s, the expectation value of the product of certain linear combination of the number operators on n consecutive sites at time t. The constraints are solved for the single-species left-right-symmetric systems. Also, examples of multi-species system for
which the evolution equations of E
n(t)'s are closed, are given.
Received 25 September 2002 / Received in final form 3 December 2002 Published online 14 February 2003
RID="a"
ID="a"e-mail: mamwad@iasbs.ac.ir 相似文献
13.
Stochastic multiresonance in a bistable sawtooth potential driven by correlated multiplicative and additive noise 总被引:1,自引:0,他引:1
J. Wang L. Cao D.J. Wu 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):123-128
We present an analytic investigation of the signal-to-noise ratio (SNR) by studying the bistable sawtooth system driven by correlated Gaussian white noises. The analytic expression of SNR is obtained. Based on it, we detect the phenomenon of stochastic multiresonance, which arises from the dependence of SNR upon the noises correlation coefficient. Furthermore, there exists not only resonance, but also suppression in the SNR∼D (the additive noise intensity) curve and the SNR∼Q (the multiplicative noise intensity) curve.
Received 26 February 2002 / Received in final form 12 July 2002 Published online 17 September 2002 相似文献
14.
F. Slanina 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):225-240
Far-from-equilibrium models of interacting particles in one dimension
are used as a basis for modelling the stock-market
fluctuations. Particle types and their positions are interpreted as
buy and sel orders placed on a price axis in the order book. We
revisit some modifications of well-known models, starting with the
Bak-Paczuski-Shubik model. We look at the four decades old Stigler
model and investigate its variants. One of them is the simplified
version of the Genoa artificial market. The list of studied models is
completed by the models of Maslov and Daniels et al. Generically, in
all cases we
compare the return distribution, absolute return autocorrelation and
the value of the Hurst exponent. It turns out that none of the models
reproduces satisfactorily all the empirical data, but the most promising
candidates for further development are the Genoa artificial market and
the Maslov model with moderate order evaporation. 相似文献
15.
G. Parisi F. Slanina 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):603-611
We present a variational approach for directed polymers in D transversal dimensions which is used to compute the correction to the mean field theory predictions with broken replica symmetry.
The trial function is taken to be a symmetrized version of the mean-field solution, which is known to be exact for . We compute the free energy corresponding to that function and show that the finite-D corrections behave like D
-4/3
. It means that the expansion in powers of 1/D should be used with great care here. We hope that the techniques developed in this note will be useful also in the study
of spin glasses.
Receveid 19 May 1998 相似文献
16.
A. Basu J.K. Bhattacharjee S. Ramaswamy 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):725-730
We show that a recently proposed [J. Fleischer, P.H. Diamond, Phys. Rev. E 58, R2709 (1998)] one-dimensional Burgers-like model for magnetohydrodynamics (MHD) is in effect identical to existing models
for drifting lines and sedimenting lattices. We use the model to demonstrate, contrary to claims in the literature, that the
energy spectrum of MHD turbulence should be independent of mean magnetic field and that cross-correlations between the noise
sources for the velocity and magnetic fields cannot change the structure of the equations under renormalisation. We comment
on the scaling and the multiscaling properties of the stochastically forced version of the model.
Received 29 October 1998 and Received in final form 8 December 1998 相似文献
17.
S. Aumaître A. Alastuey S. Fauve 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):263-266
Using simple scaling arguments and two-dimensional numerical simulations of a granular gas excited by vibrating one of the
container boundaries, we study a double limit of small 1-r and large L, where r is the restitution coefficient and L the size
of the container. We show that if the particle density n0 and (1-r2)(n0 Ld) where d is the particle diameter, are kept constant and small enough, the granular temperature, i.e. the mean value of
the kinetic energy per particle, 〈E 〉/N, tends to a constant whereas the mean dissipated power per particle, 〈D 〉/N, decreases
like
when N increases, provided that (1-r2)(n0 Ld)2 < 1. The relative fluctuations of E, D and the power injected by the moving boundary, I, have simple properties in that regime.
In addition, the granular temperature can be determined from the fluctuations of the power I(t) injected by the moving boundary. 相似文献
18.
19.
M. Dugic D. Rakovic 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):781-790
We investigate the quantum-mechanical tunneling between the “patterns" of the, so-called, associative neural networks. Being
the relatively stable minima of the “configuration-energy" space of the networks, the “patterns" represent the macroscopically
distinguishable states of the neural nets. Therefore, the tunneling represents a macroscopic quantum effect, but with some
special characteristics. Particularly, we investigate the tunneling between the minima of approximately equal depth, thus
requiring no energy exchange. If there are at least a few such minima, the tunneling represents a sort of the “random walk"
process, which implies the quantum fluctuations in the system, and therefore “malfunctioning" in the information processing
of the nets. Due to the finite number of the minima, the “random walk" reduces to a dynamics modeled by the, so-called, Pauli
master equation. With some plausible assumptions, the set(s) of the Pauli master equations can be analytically solved. This
way comes the main result of this paper: the quantum fluctuations due to the quantum-mechanical tunneling can be “minimized"
if the “pattern"-formation is such that there are mutually “distant" groups of the “patterns", thus providing the “zone" structure
of the “pattern" formation. This qualitative result can be considered as a basis of the efficient deterministic functioning
of the associative neural nets.
Received 15 July 1999 相似文献
20.
A. Svorenčík F. Slanina 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(4):453-462
Inspired by order-book models of financial fluctuations, we
investigate the Interacting gaps model, which is the schematic
one-dimensional system mimicking the order-book dynamics. We find by
simulations the power-law tail in return distribution, power-law decay
of volatility autocorrelation with exponent 0.5 and Hurst exponent
close to 1/2. Surprisingly, when we make a mean-field
approximation, i.e. replace the one-dimensional system by
effectively infinite-dimensional one, we obtain analytically the
return exponent 5/2, in perfect accord with one-dimensional simulations. 相似文献