Langevin equation for driven diffusive systems

An open controversy exists about the nature of the second-order nonequilibrium phase transition exhibited by a lattice gas in which particles are driven along one of the lattice directions by an external agent. Field theoretical predictions and Monte Carlo estimates for the critical exponent values do not seem to agree with each other. In this paper we introduce a Langevin equation in which the effects of the microscopic dynamics are carefully taken into account. We show that the order parameter critical exponent when the drive is infinite (no backwards jumps) is not mean-field-like, in contrast with the prediction for finite values of the drive. This finding seems to reconcile field theoretical and numerical results.