BICRITICAL POINT AND CROSSOVER IN A 2-TEMPERATURE, DIFFUSIVE KINETIC ISING-MODEL

The phase diagram of a two-temperature kinetic Ising model which evolv es by Kawasaki dynamics is studied using Monte Carlo simulations in di mension d = 2 and solving a mean-spherical approximation in general d. We show that the equal-temperature (equilibrium) Ising critical point is a bicritical point where two nonequilibrium critical lines meet a first-order line separating two distinct ordered phases. The shape of the nonequilibrium critical lines is described by a crossover exponent , phi, which we find to be equal to the susceptibility exponent, gamma , of the Ising model.