SHOCKS IN THE ASYMMETRY EXCLUSION MODEL WITH AN IMPURITY

We consider the one-dimensional asymmetric exclusion process with an i mpurity. This model describes particles hopping in one direction with stochastic dynamics and a hard core exclusion condition. The impurity hops with a rate different from that of the normal particles and can b e overtaken by these particles. We solve this model exactly and give i ts phase diagram. In one of the phases the system presents a shock, i. e. a sharp discontinuity between a region of high density of particles and a region of low density. Density profiles and relevant exponents are explicitly calculated. These exact results for systems of finite s ize are consistent with anomalous diffusion laws observed in infinite systems.