LONG-RANGE CORRELATIONS IN THE DISORDERED PHASE OF A SIMPLE 3-STATE LATTICE-GAS

We investigate the dynamics of a three-state stochastic lattice gas, c onsisting of holes and two oppositely ''charged'' species of particles , under the influence of an ''electric'' field, at zero total charge. Interacting only through an excluded volume constraint, particles can hop to nearest-neighbor empty sites. With increasing density and drive , the system orders into a charge-segregated state. Using a combinatio n of Langevin equations and Monte Carlo simulations, we study the stea dy-state structure factors in the disordered phase where homogeneous c onfigurations are stable against small harmonic perturbations. They sh ow a discontinuity singularity at the origin which in real space leads to an intricate crossover between power laws of different kinds.