A simulation study of an asymmetric exclusion model with open boundaries and random rates

Using numerical simulations, we study the asymmetric exclusion model with open boundaries, particlewise disorder and parallel dynamics. At each time step, particles are injected at the left boundary with probability alpha Delta t, removed on the right with probability beta Delta t, and jump in the bulk with probability p(mu)Delta t, where p(mu) is a random rate associated with each injected particle mu. The parameter Delta t interpolates between fully parallel (Delta t = 1) and random sequential (Delta t --> 0) dynamics. The phase diagram in the (alpha, beta)-plane displays high-density, low-density and maximum-current phases, with the first-order transition line between high- and low-density phases shifted away from the line alpha = beta. Within the low-density phase a platoon phase transition occurs, many features of which can be explained using exact results for asymmetric exclusion with particlewise disorder on the ring. In a certain region of parameter space the disorder induces a cusp in the current-density relation at maximum Bow. Our simulations indicate that this does not affect the topology of the phase diagram, nor the familiar 1/root x-decay of the density profile in the maximum-current phase.