共查询到20条相似文献,搜索用时 46 毫秒
1.
We study the escape for the mean first passage time (MFPT) over a potential barrier for a system with non- fluctuating potential barrier and only driven by a three-state noise. It is shown that in some circumstances, the three-state noise can induce the resonant activation for the MFPT over the potential barrier; but in other circumstances, it can not. There are three resonant activations for the MFPT over the potential barrier, which are respectively as the functions of the transition rates of the three-state noise. 相似文献
2.
M. L. Deng W. Q. Zhu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):391-397
The energy diffusion controlled reaction rate of a reacting particle with linear weak damping and broad-band noise excitation
is studied by using the stochastic averaging method. First, the stochastic averaging method for strongly nonlinear oscillators
under broad-band noise excitation using generalized harmonic functions is briefly introduced. Then, the reaction rate of the
classical Kramers' reacting model with linear weak damping and broad-band noise excitation is investigated by using the stochastic
averaging method. The averaged It? stochastic differential equation describing the energy diffusion and the Pontryagin equation
governing the mean first-passage time (MFPT) are established. The energy diffusion controlled reaction rate is obtained as
the inverse of the MFPT by
solving the Pontryagin equation. The results of two special cases of
broad-band noises, i.e. the harmonic noise and the exponentially corrected noise, are discussed in details. It is demonstrated
that the general expression of reaction rate derived by the authors can be reduced to the classical ones via linear approximation
and high potential barrier approximation. The good agreement with the results of the Monte Carlo simulation verifies that
the reaction rate can be well predicted using the stochastic averaging method. 相似文献
3.
Entropic noise induced stability and double entropic stochastic resonance induced by correlated noises 下载免费PDF全文
For the activated dynamics of a Brownian particle moving in a confined system with the presence of entropic barriers, this paper investigates a periodic driving and correlations between two noises. Within the two-state approximation, the explicit expressions of the mean first passage time (MFPT) and the spectral power amplification (SPA) are obtained, respectively. Based on the numerical computations, it is found that: (i) The MFPT as a function of the noise intensity exhibits a maximum with the positive correlations between two noises (λ>0), this maximum for MFPT shows the characteristic of the entropic noise induced stability (ENIS) effect. The intensity λ of correlations between two noises can enhance the ENIS effect. (ii) The SPA as a function of the noise intensity exhibits a double-peak by tuning the noise correlation intensity λ, i.e., the existence of a double-peak behaviour is the identifying characteristic of the double entropic stochastic resonance phenomenon. 相似文献
4.
5.
Rui-Hua Shao 《Physica A》2009,388(6):977-983
We study theoretically a bistable system with time-delayed feedback driven by a weak periodic force. The effective potential function and the steady-state probability density are derived. The delay time and the strength of its feedback can change the shapes of the potential wells. In the adiabatic approximation, the signal-to-noise ratio (SNR) of the system with a weak periodic force is obtained. The time-delayed feedback modulates the magnitude of SNR by changing the shape of the potential and the effective strength of the signal. The maximum of SNR decreases with increasing the feedback intensity ?. When ? is negative (or positive), the time delay can suppress (or promote) the stochastic resonance phenomenon. 相似文献
6.
Stochastic resonance, reverse-resonance, and resonant activation induced by a multi-state noise 总被引:1,自引:0,他引:1
Jing-hui Li 《Physica A》2010,389(1):7-3266
In this paper, we investigate the periodic response for a linear system driven by a multiplicative multi-state noise (which is composed of the multiplication of two dichotomous noises) to an input temporal oscillatory signal, and the escape of Brownian particles over the fluctuating potential barrier for a system with a piece-wise linear potential and driven by an additive multi-state noise (which is also composed of the multiplication of two dichotomous noises). For the first system, we get the stochastic resonance phenomenon for the amplitude of the periodic response vs. the two dichotomous noise strengths, and the phenomenon of reverse-resonance for the amplitude of the periodic response vs. k, which represents the asymmetry degree of the dichotomous noises. For the second system, we obtain the resonant activation phenomenon, for which the mean first passage time of the Brownian particles over the fluctuating potential barrier shows a minimum as the function of the transition rates of the multi-state noise. 相似文献
7.
Dan Wu 《Physics letters. A》2008,372(32):5299-5304
The dynamics of a periodically driven FitzHugh-Nagumo system with time-delayed feedback and Gaussian white noise is investigated. The stochastic resonance which is characterized by the Fourier coefficient Q is numerically calculated. It is found that the stochastic resonance of the system is a non-monotonic function of the noise strength and the signal period. The variation of the time-delayed feedback can induce periodic stochastic resonance in the system. 相似文献
8.
The phenomenon of stochastic resonance in a bistable system with time-delayed feedback driven by non-Gaussian noise is investigated. Combining the small time delay approximation, the path-integral approach and the unified colored noise approximation, a general approximate Fokker–Planck equation of a stochastic system is obtained. The effects of the parameter q indicating the departure from the Gaussian noise, the delay time τ , and the correlation time τ0 of the non-Gaussian noise on the quasi-steady-state probability distribution function (SPD) and the signal-to-noise ratio (SNR) are discussed. It is found that the number of peaks in SPD and the reentrant transition between one peak and two peaks and then to one peak again in the curve of SNR depends on the parameter q, the delay time τ , and the noise correlation time τ0. 相似文献
9.
10.
Jorge A. Revelli 《Physica A》2008,387(13):3103-3110
We have investigated the effects of noise on an extended chaotic system. The chosen model is the Lorenz’96, a type of “toy” model used for climate studies. Through the analysis of the system’s time evolution and its time and space correlations, we have obtained numerical evidence for two distinct stochastic resonance-like behaviors. Such behaviors are seen when both the usual and a generalized signal-to-noise ratio functions are depicted as a function of the external noise intensity, or of the system size. The underlying mechanisms seem to be associated with a noise-induced chaos reduction. The possible relevance of these and other findings for an optimal climate prediction are discussed. 相似文献
11.
Zheng-Lin Jia 《Physica A》2008,387(25):6247-6251
The effects of time delay on the transient properties of a time-delayed metastable system subjected to cross-correlated noises are studied by means of a stochastic simulation method. It is found that: (i) Both additive noise and multiplicative noise can produce the noise enhanced stability (NES) effect; (ii) The time delay induces critical behavior on the NES, i.e., there is a critical value of the delay time τc1≈2.2, above which the time delay increases the stability of the system enhanced by the additive noise, and below which the NES effect induced by the additive noise disappears; (iii) There exists another critical value of the delay time τc2≈3.0, above which the time delay increases the stability of the system enhanced by the multiplicative noise and below which the time delay decreases it. 相似文献
12.
13.
PeiMing Shi HaiFeng Xia DongYing Han RongRong Fu 《Chinese Journal of Physics (Taipei)》2017,55(1):133-141
The dynamical complexity and stochastic resonance (SR) of a time-delayed asymmetric bistable system are studied. Firstly, The effective potential function and steady-state probability density function are deduced based on Born-Oppenheimer approximation theory, and we find that the asymmetric item and time-delayed feedback item can both affect the curve of these two functions, especially the asymmetric item can induce phase displacement. Secondly, the mean first-passage time (MFPT) which plays an important role in research on particles escape rate is derived and we obtain an approximate asymmetric item r which can maintain a steady MFPT. Finally, the influences of different parameters on SR are researched by signal-to-noise ratio (SNR). The analytic expression of SNR is derived and three dimensional graphs and contour maps of SNR with different parameters are obtained. The results indicate that time delay τ and time delay strength e can enhance the SNR and the asymmetric item r has a non-monotone effect on SNR. Notably, adjusting time delay strength e is more sensitive than that of the time delay τ in controlling SR. 相似文献
14.
Based on the exponential monostable potential, we study an exponential monostable system with time-delayed feedback driven by weak periodic signals and additive Gaussian white noises. The small delay approximation is used to deduce the steady-state probability distribution and the effective potential function is derived. The system parameters l and b, time delay τ, feedback strength β can change the shapes of the potential function. The mean first-passage time (MFPT) is calculated, which plays an extremely important role in the research of particles escape. And the signal-to-noise ratio (SNR) of the system can be obtained by using the adiabatic approximation theory. The phenomenon of stochastic resonance is investigated under different system parameters and time-delayed feedback. The amplitude of SNR can be changed by adjusting the system parameters. When the feedback strength β is positive (or negative), the time delay τ can promote (or suppress) the stochastic resonance phenomenon. The SNR versus the noise intensity D presents the stochastic resonance phenomenon. In addition, the SNR increases non-monotonically with the increasing feedback strength β and the parameter b. Also, the analysis and numerical simulation results of SNR are in good agreement with the formula simulation. 相似文献
15.
Marko Gosak 《Physica D: Nonlinear Phenomena》2009,238(5):506-515
We study the impact of subthreshold periodic pacemaker activity and internal noise on the spatial dynamics of excitable media. For this purpose, we examine two systems that both consist of diffusively coupled units. In the first case, the local dynamics of the units is driven by a simple one-dimensional model of excitability with a piece-wise linear potential. In the second case, a more realistic biological system is studied, and the local dynamics is driven by a model for calcium oscillations. Internal noise is introduced via the τ-leap stochastic integration procedure and its intensity is determined by the finite size of each constitutive system unit. We show that there exists an intermediate level of internal stochasticity for which the localized pacemaker activity maps best into coherent periodic waves, whose spatial frequency is uniquely determined by the local subthreshold forcing. Via an analytical treatment of the simple minimal model for the excitable spatially extended system, we explicitly link the pacemaker activity with the spatial dynamics and determine necessary conditions that warrant the observation of the phenomenon in excitable media. Our results could prove useful for the understanding of interplay between local and global agonists affecting the functioning of tissue and organs. 相似文献
16.
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
17.
J. Dunkel W. Ebeling U. Erdmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):511-524
We investigate the stochastic dynamics of an one-dimensional ring with N self-driven Brownian particles. In this model neighboring particles interact via conservative Morse potentials. The influence of the surrounding heat bath is modeled by Langevin-forces (white noise) and
a constant viscous friction coefficient γ. The Brownian particles are provided with internal energy depots which may lead to active motions of the particles. The depots
are realized by an additional nonlinearly velocity-dependent friction coefficient γ
1(v) in the equations of motions. In the first part of the paper we study the partition functions of time averages and thermodynamical
quantities (e.g. pressure) characterizing the stationary physical system. Numerically calculated non-equilibrium phase diagrams are represented.
The last part is dedicated to transport phenomena by including a homogeneous external force field that breaks the symmetry
of the model. Here we find enhanced mobility of the particles at low temperatures.
Received 21 July 2001 相似文献
18.
We study the flip-processes in a two-level system, which is triggered by the coupling to a classical bath. When the bath is represented by a stochastic field, the time evolution of the density matrix leads to a stochastic equation with a multiplicative noise. Accordingly the Fokker–Planck-equation (FPE) depends on the matrix elements of the underlying density operator. The solution of the FPE can be parametrized in terms of an inherent conserved quantity α, which is interpreted as a measure for the persistence of quantum information. We show that the FPE exhibits a single unique steady state solution different from Boltzmann's law. The exactly computable discrete spectrum of the relaxation times is characterized by two quantum numbers and the ratio of Planck's constant and the coupling strength to the bath. The total entropy is analyzed as function of the quantum number α . In case of α=1 the system is in a pure state whereas for α≠1 a mixed state is realized. In case of two, two-level systems, immersed in the common bath, the two noninteracting two-level systems become mutually entangled. The annealed entropy is in that case non-extensive. 相似文献
19.
The associated relaxation time Tc and the normalized correlation function C(s) for a tumor cell growth system subjected to color noises are investigated. Using the Novikov theorem and Fox approach, the steady probability distribution is obtained. Based on them, the expressions of Tc and C(s) are derived by means of projection operator method, in which the effects of the memory kernels of the correlation function are taken into account. Performing the numerical computations, it is found: (1) With the cross-correlation intensity |λ|, the additive noise intensity α and the multiplicative noise self-correlation time τ1 increasing, the tumor cell numbers can be restrained; And the cross-correlation time τ3, the multiplicative noise intensity D can induce the tumor cell numbers increasing; However, the additive noise self-correlation time τ2 cannot affect the tumor cell numbers; The relaxation time Tc is a stochastic resonant phenomenon, and the distribution curves exhibit a single-maximum structure with D increasing. (2) The cross-correlation strength λ weakens the related activity between two states of the tumor cell numbers at different time, and enhances the stability of the tumor cell growth system in the steady state; On the contrast, τ1 and τ3 enhance the related activity between two states at different time; However, τ2 has no effect on the related activity between two states at different time. 相似文献
20.
In this paper the energy diffusion controlled reaction rate in dissipative Hamiltonian
systems is investigated by using the stochastic averaging method for quasi
Hamiltonian systems. The boundary value problem of mean first-passage time
(MFPT) of averaged system is formulated and the energy diffusion controlled
reaction rate is obtained as the inverse of MFPT. The energy diffusion
controlled reaction rate in the classical Kramers bistable potential and in
a two-dimensional bistable potential with a heat bath are obtained by using
the proposed approach respectively. The obtained results are then compared
with those from Monte Carlo simulation of original systems and from the
classical Kramers theory. It is shown that the reaction rate obtained by
using the proposed approach agrees well with that from Monte Carlo
simulation and is more accurate than the classical Kramers rate. 相似文献