共查询到20条相似文献,搜索用时 15 毫秒
1.
L. R. Nie D. C. Mei 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):475-481
The properties of the underdamped Josephson junction subjected to
colored noises were investigated with large and small phase
difference (φ). For the case of the large φ, we found
numerically that: (i) the probability distribution function of
φ exhibits monostability → bistability → monostability
transitions as the autocorrelation rate (λ) of a colored
noise increases; (ii) in the bistability region the multiplicative
noise drives the phase difference to turn over periodically; (iii)
the slope K of the linear response of the junction potential
difference (〈V 〉) can be somewhat reduced by means of tuning an
optimal λ; (iv) the amplitude of φ in response to
external sinusoidal signals changes with λ. For the case of
small φ, after deriving the analytical expressions of the
potential difference amplitude (〈V 〉max) and the K in the
presence of a dichotomous noise, we found nonmonotonic behavior of
〈V 〉max and the slope K as a function of λ. 相似文献
2.
Tamm MV Nechaev SK Erukhimovich IY 《The European physical journal. E, Soft matter》2005,17(2):209-219
We investigate the statistical properties of a randomly branched 3-functional N-link polymer chain without excluded volume, whose one point is fixed at the distance d from the impenetrable surface in a 3-dimensional space. Exactly solving the Dyson-type equation for the partition function Z(N, d )= N-θeγN in 3D, we find the “surface” critical exponent θ =
, as well as the density profiles of 3-functional units and of dead ends. Our approach enables to compute also the pairwise correlation function of a randomly branched polymer in a 3D semi-space. 相似文献
3.
S. Haddad M. Héritier R. Bennaceur 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(3):429-437
By setting up the relevant recursion relations and by doing exact and approximate calculations, we show that there is no critical
dimension in a self-avoiding random walk on a simplex fractal.
Received: 6 April 1998 / Revised: 4 August 1998 / Accepted: 26 August 1998 相似文献
4.
5.
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
6.
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
7.
E. Scalas U. Garibaldi S. Donadio 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):271-272
This erratum corrects a mistake in reference [E. Scalas, U. Garibaldi, S. Donadio, Eur. Phys. J. B 53, 267 (2006)].
In that paper,
we needed an aperiodic version of the BDY game, but, in formula (1),
we incorrectly presented
a periodic transition matrix of period 2 in the special case of g = 2 agents.
Here, we present the right aperiodic version. 相似文献
8.
A. Bershadskii 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):691-693
It is shown that multifractal properties of some random and disordered systems can be simulated using thermodynamics of a
generalized ideal monoatomic gas in a fractal phase space.
Received 25 November 1998 and Received in final form 16 December 1998 相似文献
9.
D. Martila R. Mankin R. Tammelo A. Sauga E. Reiter 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(3):375-383
The influence of noise-flatness on overdamped motion of
Brownian particles in a 1D periodic system with a simple sawtooth
potential subjected to both unbiased thermal noise and
three-level telegraph noise is considered. The exact formula for
the stationary probability flux (current) is presented. The
phenomenon of multiple current reversals and some topological
properties of the hypersurface of zero current in the parameter
space of noises are investigated and illustrated by phase
diagrams. The conditions for the existence of four current
reversals versus the switching rate of nonequilibrium noise are
given. An alternative interpretation of the results in terms of
cross-correlation between two dichotomous noises is presented. 相似文献
10.
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
11.
X. Gu S. Zhu D. Wu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):461-466
The steady state properties of a noise-driven bistable system are
investigated when there are two different kinds of time delays
existed in the deterministic and fluctuating forces respectively.
Using the approximation of the probability density approach, the
delayed Fokker-Planck equation is obtained. The stationary
probability distribution (SPD) and the variance of the system are
derived. It is found that the time delay τ in the deterministic
force can reduce the fluctuations while the time delay β in
the fluctuating force can enhance the fluctuations. Numerical
simulations are presented and are in good agreement with the
approximate theoretical results. 相似文献
12.
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
13.
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
14.
S. E. Mangioni H. S. Wio 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(1):67-73
We analyze the effect of a colored non Gaussian noise on a model of
a random walker moving along a ratchet potential. Such a model was
motivated by the transport properties of motor proteins, like
kinesin and myosin. Previous studies have been realized assuming
white noises. However, for real situations, in general we could
expect that those noises be correlated and non Gaussian. Among other
aspects, in addition to a maximum in the current as the noise
intensity is varied, we have also found another optimal value of the
current when departing from Gaussian behavior. We show the relevant
effects that arise when departing from Gaussian behavior,
particularly related to current's enhancement, and discuss its
relevance for both biological and technological situations. 相似文献
15.
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
16.
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
17.
J.-U. Sommer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):537-542
We study the adsorption cross-over of ideal polymer chains in an environment of disordered traps. Starting from the assumption
of an optimal cluster size of traps (optimal fluctuation method) we derive a general scaling form of the free energy function
for arbitrary spatial dimensions. For small concentrations of traps we find a cross-over from localized (adsorbed) behavior
to delocalized behavior depending on the chain's length and on the depth of the traps; this is connected with the non-monotonic
behavior of the chain's extension. In terms of the free energy of the chain this cross-over resembles a first order transition
scenario, the chain gets localized at many traps at once.
Received 18 November 1998 相似文献
18.
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
19.
M. Gosak M. Marhl M. Perc 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(2):171-177
We study the transition from stochasticity to determinism
in calcium oscillations via diffusive coupling of individual cells that are
modeled by stochastic simulations of the governing reaction-diffusion
equations. As expected, the stochastic solutions gradually converge to their
deterministic limit as the number of coupled cells increases. Remarkably
however, although the strict deterministic limit dictates a fully periodic
behavior, the stochastic solution remains chaotic even for large numbers of
coupled cells if the system is set close to an inherently chaotic regime. On
the other hand, the lack of proximity to a chaotic regime leads to an
expected convergence to the fully periodic behavior, thus suggesting that
near-chaotic states are presently a crucial predisposition for the
observation of noise-induced chaos. Our results suggest that chaos may exist
in real biological systems due to intrinsic fluctuations and uncertainties
characterizing their functioning on small scales. 相似文献
20.
D. Stauffer M. Sahimi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(2):147-152
Models that provide insight into how extreme positions regarding any social phenomenon may spread in a society or at the global
scale are of great current interest. A realistic model must account for the fact that globalization, internet, and other means
of mass communications have given rise to scale-free networks of interactions between people. We propose a novel model which
takes into account the nature of the interactions network, and provides some key insights into this phenomenon. These include,
(1) the existence of a
fundamental difference between a hierarchical network whereby people are influenced by those that are higher in the hierarchy
but not by those below them, and a symmetrical network where person-on-person influence works mutually, and (2) that a few
“fanatics” can influence a large fraction of the population either temporarily (in the hierarchical networks) or permanently
(in symmetrical networks). Even if the “fanatics” disappear, the population may still remain susceptible to the positions
originally advocated by them. The
model is, however, general and applicable to any phenomenon for which there is a degree of enthusiasm or susceptibility to
in the population. 相似文献