DISPERSION EFFECTS IN LATTICE GASES WITH INTERNAL AND TRANSLATIONAL MODE-COUPLING

We construct a 7-bit lattice-gas automaton modelling a 2D fluid with internal degrees of freedom weakly coupled to the translational degrees of freedom. The coupling is obtained by using probabilistic collision rules and produces an additional mode for density fluctuations whose effects are evidenced by the line shape of the dynamic structure factor; the spectrum of density fluctuations shows the usual normal modes together with an additional mode and a dispersion effect for the acoustic waves. Good agreement is found between these predictions and measurements performed in a direct simulation of the lattice gas dynamics.