Scaling and universality in Brownian motion on a stochastic harmonic oscillator chain.

Abstract

Diffusion of a Brownian particle along a stochastic harmonic oscillator chain is investigated. In contrast to the usually discussed Brownian motion driven by Gaussian white noise, the particle at high temperatures performs long Lévy flights. At high temperatures T the diffusion coefficient scales as D∼T^{2+α}, where the parameter α determine the average damping force ∝1/(T^{α}P) on the particle at large momentum P and at high temperature. The exponent α depends on the particle-chain interaction and chain properties. It is shown that the mean time t[over ¯]_{f} necessary to perform a flight of l lattice constant scales with l as t[over ¯]_{f}∝l^{2/3} at high temperatures and flight lengths. Last, the flight length probability distribution is found to decay as 1/l^{β} with the exponent β=4/3 being universal, i.e., independent of the model parameters.