Tag diffusion in driven systems, growing interfaces and anomalous fluctuations

Abstract

Tagged diffusion in a one-dimensional hard-core lattice gas with biased nearest-neighbor hopping is mapped to a model of a growing interface. Based on the Kardar-Parisi-Zhang theory of interface dynamics, it is suggested that fluctuations, in the separation of the initial position of a tagged particle from the position at time t of a particle with tag shifted by vt at time t, grow at t^½ for most v, and as t^1/3 for a critical v_c. This is verified by numerical simulation, and the dependence of v_c on bias and density is found. The t^¼ growth of fluctuations in the unbiased case is unstable with respect to both bias and v-v_c.