SPONTANEOUS BREAKING OF TRANSLATIONAL INVARIANCE IN ONE-DIMENSIONAL STATIONARY STATES ON A RING

We consider a model in which positive and negative particles diffuse i n an asymmetric, CP-invariant way on a ring. The positive particles ho p clockwise, the negative counter-clockwise and oppositely-charged adj acent particles may swap positions. Monte Carlo simulations and analyt ic calculations suggest that the model has three phases; a 'pure' phas e in which one has three pinned blocks of only positive, negative part icles and vacancies, and in which translational invariance is spontane ously broken, a 'mixed' phase with a non-vanishing current in which th e three blocks are positive, negative and neutral, and a disordered ph ase without blocks.