The Study Of Current Reversal,Anomalous Mobility And Diffusions Induced By Temperature And Friction

In recent years,the research on transport of Brownian particle plays an important role in the fields of physics,chemistry and complex system science,among which includes the study of noise-induced transport properties of Brownian particle.Considering the existence of the friction fluctuation and the bias,this paper investigates the transport properties of inertial Brownian particle driven by cross-correlated noises moving in a biased cosine potential via the second-order Runge-Kutta algorithm.It is found from figures of the mean velocity and the time-dependent diffusive coefficient of particle motion that,the existence of cross-correlated noises may break some symmetries of this nonlinear system.Anomalous diffusion(appearing in the process of reaching the steady state),current reversal,negative mobility,nonlinear transport,ratchet effect and other phenomena(appearing after reaching the steady state)can be controlled by temperature,friction or other parameters.The reason for these transport properties can be explained by the transient probability distributions of particle's velocity and displacement and stationary probability distributions of particle's velocity,and deepen the understanding of the system dynamics mechanism via the time-dependent diffusive coefficient.This paper is of potential help for the application of studying transport properties of Brownian particle,such as particle separation,Josephson junction system,etc.In Chapter 2,the related dynamical and nonequilibrium statistic physical theory are introduced.Then,in Chapter 3,the related stochastic simulation algorithms and numerical simulation methods via computer are also presented.Finally,in Chapter 4,the transport properties of the inertia Brownian particle in a biased periodic potential induced by friction and temperature fluctuation are investigated.The results mainly shows:(1)Both the friction fluctuation and the thermal fluctuation may be related to friction,thus they may be correlated with each other;(2)The effects of the correlated strength and the bias can lead to a transition between bimodal and unimodal of the stationary probability distribution of particle's velocity;(3)There exists various transport for certain conditions,such as current reversal,ratchet effect,nonlinear transport,and anomalous mobility,which may be tuned via temperature and friction;(4)The particle may undergo hyper-diffusion,super-diffusion,sub-diffusion,and finally normal diffusion for some certain parameters of the system.These anomalous diffusions may be tuned via temperature and friction;(5)The competition or promotion between the bias and the correlation between noises would constitute a simple mechanism for particle's transport,and we give possible explanations via the stationary probability distributions;(6)The transient probability distributions of particle's velocity and position shows rich dynamics.The results reveal that the motion of particle is sensitive to the initial conditions for a small bias.The particle may stay in its initial well,or jump to the left/right wells for different initial conditions.On the other hand,for a large bias,the bias dominates that the particle jumps to its left or right wells,and the particle is more possible to jump out of its initial well with the correlated strength increasing.Namely,the particle moves to the right wells for a positive bias,whereas the particle jumps to the left wells for a negative bias.