title: Anomalous diffusion in infinite horizon billiards.
abstract: We consider the long time dependence for the moments of displacement <|r|(q)> of infinite horizon billiards, given a bounded initial distribution of particles. For a variety of billiard models we find <|r|(q)> approximately t(gamma(q)) (up to factors of ln t). The time exponent, gamma(q), is piecewise linear and equal to q/2 for q<2 and q-1 for q>2. We discuss the lack of dependence of this result on the initial distribution of particles and resolve apparent discrepancies between this time dependence and a prior result. The lack of dependence on initial distribution follows from a remarkable scaling result that we obtain for the time evolution of the distribution function of the angle of a particle's velocity vector.
authors.affiliation: Department of Physics and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20904, USA. dna2@physics.umd.edu
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Armstead
authors.forename: Brian R
authors.initials: BR
authors.lastname: Hunt
authors.forename: Edward
authors.initials: E
authors.lastname: Ott