Self-diffusion in simple models: Systems with long-range jumps

Abstract

We review some exact results for the morion of a tagged particle in simple models. Then, we study the density dependence of the sill-diffusion coefficient D_(N)(ρ) in lattice systems with simple symmetric exclusion in which the particles can jump, with equal rates, to a set of N neighboring sites. We obtain positive upper and lower bounds on F_(N)(ρ) = N{(1 - ρ) - [D_(N)(ρ)/D_(N)(0)]}/[ρ(1 - ρ)] for ρ is an element of [0, 1]. Computer simulations for the square, triangular, and one-dimensional lattices suggest that FN becomes effectively independent of N for N greater than or equal to 20.