DIFFUSION IN A ONE-DIMENSIONAL BOSONIC LATTICE-GAS

A one-dimensional lattice-gas model with order preservation is conside red where the occupation probabilities of sites correspond to Bose sta tistics as a consequence of the prescribed dynamics. The master equati on for the particle-cluster dynamics at the sites is formulated. The c orresponding continuum nonlinear diffusion equation is derived for the space- and time-dependent concentration fluctuations. The equation ca n be regarded, in the presence of a drift force, as the Burgers equati on when terms irrelevant in the sense of renormalization-group ideas a re neglected. Collective centre-of-mass and tagged-particle diffusion are investigated by numerical simulations and the results agree with t he analytical derivations. Subdiffusive behaviour of the mean-square d isplacement of tagged particles and normal collective and centre-of-ma ss diffusion are observed when no bias is present. The dispersion of t he centre-of-mass displacement exhibits superdiffusive behaviour in th e case of mean drift of the particles. Discrepancies of about 20% betw een the numerically determined superdiffusion coefficients and the pre dictions of the mode-coupling theory are found and discussed.