DIFFUSION IN THE PRESENCE OF TOPOLOGICAL DISORDER

A general framework is presented for the discussion of Brownian motion in crystals with randomly distributed topological defects. In a two-d imensional lattice with disclinations one finds a nonuniversal subdiff usional behavior if screening in the disclination ensemble is taken in to account. Without screening, a Sinai-type diffusion is expected. In a three-dimensional random array of parallel screw dislocations, a Bro wnian particle shows anisotropic normal diffusion. However, the proces s no longer is Gaussian and displays long-time tails in the fourth-ord er cumulants.