共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
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
3.
4.
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
5.
The spatially one-dimensional relativistic Ornstein-Uhlenbeck process in an arbitrary inertial frame
C. Barbachoux F. Debbasch J.P. Rivet 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(1):37-47
The spatially one-dimensional relativistic Ornstein-Uhlenbeck process is studied in an arbitrary inertial reference frame.
In particular, we derive directly from the stochastic equations of motion in an arbitrary inertial frame the transport equation
for the distribution function of the diffusing particles in phase-space. We explain why this result is not trivial and has,
at the very least, methodological interest. We also show that this result offers a conceptually new proof of the well-known
fact that the relativistic one-particle distribution function in phase-space is a Lorentz scalar.
Received 28 March 2000 相似文献
6.
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
7.
8.
D. Chowdhury R.C. Desai 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(2):375-384
A Bus Route Model (BRM) can be defined on a one-dimensional lattice, where buses are represented by “particles” that are driven
forward from one site to the next with each site representing a bus stop. We replace the random sequential updating rules
in an earlier BRM by parallel updating rules. In order to elucidate the connection between the BRM with parallel updating
(BRMPU) and the Nagel-Schreckenberg (NaSch) model, we propose two alternative extensions of the NaSch model with space-/time-dependent
hopping rates. Approximating the BRMPU as a generalization of the NaSch model, we calculate analytically the steady-state
distribution of the time headways (TH) which are defined as the time intervals between the departures (or arrivals) of two
successive particles (i.e., buses) recorded by a detector placed at a fixed site (i.e., bus stop) on the model route. We compare these TH distributions with the corresponding results of our computer simulations
of the BRMPU, as well as with the data from the simulation of the two extended NaSch models. We also investigate interesting
kinetic properties exhibited by the BRMPU during its time evolution from random initial states towards its steady-states.
Received 16 December 1999 相似文献
9.
S. Wolfling Y. Kantor 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(4):569-577
Distribution of loops in a one-dimensional random walk (RW), or, equivalently, neutral segments in a sequence of positive
and negative charges is important for understanding the low energy states of randomly charged polymers. We investigate numerically
and analytically loops in several types of RWs, including RWs with continuous step-length distribution. We show that for long
walks the probability density of the longest loop becomes independent of the details of the walks and definition of the loops.
We investigate crossovers and convergence of probability densities to the limiting behavior, and obtain some of the analytical
properties of the universal probability density.
Received 8 January 1999 相似文献
10.
B. Schulz S. Trimper M. Schulz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):499-505
Random walks in one-dimensional environments with an additional dynamical feedback-coupling is analyzed numerically. The feedback
introduced via a generalized master equation is controlled by a memory kernel of strength the explicit form of which is motivated by arguments used in mode-coupling theories. Introducing several realizations of
the feedback mechanism within the simulations we obtain for a negative memory term, , superdiffusion in the long time limit while a positive memory leads to localization of the particle. The numerical simulations
are in agreement with recent predictions based on renormalization group techniques. A slight modification of the model including
an exponentially decaying memory term and some possible applications for glasses and supercooled liquids are suggested. The
relation to the true self-avoiding is discussed.
Received 16 September 1999 and Received in final form 27 December 1999 相似文献
11.
We have investigated the algebraic structure of the Fokker-Planck equation with a variable diffusion coefficient and a time-dependent
mean-reverting force. Such a model could be useful to study the general problem of a Brownian walker with a space-dependent
diffusion coefficient. We also show that this model is related to the Fokker-Planck equation with a constant diffusion coefficient
and a time-dependent anharmonic potential of the form V(x, t) = ?a(t)x
2 + b ln x, which has been widely applied to model different physical and biological phenomena, e.g. the study of neuron models and stochastic resonance in monostable nonlinear oscillators. Using the Lie algebraic approach
we have derived the exact diffusion propagators for the Fokker-Planck equations associated with different boundary conditions,
namely (i) the case of a single absorbing barrier, and (ii) the case of two absorbing barriers. These exact diffusion propagators
enable us to study the time evolution of the corresponding stochastic systems.
Received 23 October 2001 and Received in final form 24 December 2001 相似文献
12.
A. Namazi N. Eissfeldt P. Wagner A. Schadschneider 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):559-570
The Krauss-model is a stochastic model for traffic flow which is continuous in space. For periodic boundary conditions it
is well understood and known to display a non-unique flow-density relation (fundamental diagram) for certain densities. In
many applications, however, the behaviour under open boundary conditions plays a crucial role. In contrast to all models investigated
so far, the high flow states of the Krauss-model are not metastable, but also stable. Nevertheless we find that the current
in open systems obeys an extremal principle introduced for the case of simpler discrete models. The phase diagram of the open
system will be completely determined by the fundamental diagram of the periodic system through this principle. In order to
allow the investigation of the whole state space of the Krauss-model, appropriate strategies for the injection of cars into
the system are needed. Two methods solving this problem are discussed and the boundary-induced phase transitions for both
methods are studied. We also suggest a supplementary rule for the extremal principle to account for cases where not all the
possible bulk states are generated by the chosen boundary conditions.
Received 16 September 2002 / Received in final form 4 November 2002 Published online 31 December 2002 相似文献
13.
Using the Lie algebraic approach we have derived the exact diffusion propagator of the Fokker-Planck equation with a time-dependent
variable diffusion coefficient and a time-dependent mean-reverting force between two absorbing boundaries. The exact diffusion
propagator not only enables us to study the time evolution of the corresponding stochastic system, but the knowledge of the
propagator can also provide a benchmark for testing approximate numerical or analytical procedures. Furthermore, the Lie algebraic
method is very simple and could be easily extended to the more general Fokker-Planck equations with well-defined algebraic
structures.
Received 18 December 2002 / Received in final form 3 March 2003 Published online 24 April 2003 相似文献
14.
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
15.
16.
E. Canessa 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(1):123-127
We address the issue of stock market fluctuations within Langevin Dynamics (LD) and the thermodynamics definitions of multifractality
in order to study its second-order characterization given by the analogous specific heat Cq, where q is an analogous temperature relating the moments of the generating partition function for the financial data signals. Due
to non-linear and additive noise terms within the LD, we found that Cq can display a shoulder to the right of its main peak as also found in the S&P500 historical data which may resemble a classical
phase transition at a critical point.
Received 6 November 2000 and Received in final form 26 March 2001 相似文献
17.
A new and general approach is proposed to analyze the dynamics of a colloidal particle interacting with a nearby wall. This
analysis can be used to determine the acting forces even when the system is non-stationary. As an illustration, we use total
internal reflection microscopy to investigate the forces acting on a polystyrene sulfate latex particle as it is receding
from a charged glass surface.
Received 10 October 2002 Published online: 16 April 2003
RID="a"
ID="a"Present address: Department of Polymer Physics, BASF Aktiengesellschaft, 67056 Ludwigshafen, Germany
RID="b"
ID="b"Present address: Arryx. Inc., Chicago, IL 60601, USA 相似文献
18.
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
19.
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
20.
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