arXiv subjects

Christian Weber

Publications and source records attributed to Christian Weber.

22 records · Page 2Linked to original sources

arXiv2012

Active Particles Forced by an Asymmetric Dichotomous Angle Drive

We analyze the dynamics of particles in two dimensions with constant speed and a stochastic switching angle dynamics defined by a correlated dichotomous Markov process (telegraph noise) plus Gaussian white noise. We study various cases of the asymptotic diffusional motion of the particle which is characterized by the effective diffusion coefficient. Expressions for this coefficient are derived and discussed in dependence on the correlation time and the intensity of the noise. The situation with a given mean curvature is of special interest since a non-monotonic behavior of the effective diffusion coefficient as function of the noise intensity and correlation time is found. A timescale matching condition for maximal diffusion is formulated.

cond-mat.stat-mech↗

arXiv2011

Active motion assisted by correlated stochastic torques

The stochastic dynamics of an active particle undergoing a constant speed and additionally driven by an overall fluctuating torque is investigated. The random torque forces are expressed by a stochastic differential equation for the angular dynamics of the particle determining the orientation of motion. In addition to a constant torque, the particle is supplemented by random torques which are modeled as an Ornstein-Uhlenbeck process with given correlation time $τ_c$. These nonvanishing correlations cause a persistence of the particles' trajectories and a change of the effective spatial diffusion coefficient. We discuss the mean square displacement as a function of the correlation time and the noise intensity and detect a nonmonotonic dependence of the effective diffusion coefficient with respect to both correlation time and noise strength. A maximal diffusion behavior is obtained if the correlated angular noise straightens the curved trajectories, interrupted by small pirouettes, whereby the correlated noise amplifies a straightening of the curved trajectories caused by the constant torque.

cond-mat.stat-mech↗

arXiv2011

Rectification of motion in nonlinear media with asymmetric random drive

We consider moving particles in media with nonlinear friction and drive them by an asymmetric dichotomic Markov process. Due to different energy dissipations, during the forward and backward stroke, we obtain a mean non-vanishing directed flow of the particles. Starting with the stationary velocity distribution, we calculate the stationary current of particles, the variance and the relative variance in dependence on the degree of nonlinearity of the friction, on the asymmetry and for different strengths of friction. In two dimensions the particle performs diffusional motion, if in addition the direction of the asymmetric drive changes stochastically.

cond-mat.stat-mech↗

arXiv2009

Low-degree Cohomology of Integral Specht Modules

We introduce a way of describing cohomology of the symmetric groups with coefficients in Specht modules over Z or F_p. We study i-th-degree cohomology for i in {0,1,2}. The focus lies on the isomorphism type of second-degree cohomology of integral Specht modules. Unfortunately, only in few cases can we determine this exactly. In many cases we obtain only some information about the prime divisors of the cohomology group's order. The most important tools we use are the Zassenhaus algorithm, the Branching Rules, Bockstein type homomorphisms, and the results from [Burichenko et al., 1996].

math.GR↗