EXACT DIFFUSION CONSTANT FOR THE ONE-DIMENSIONAL PARTIALLY ASYMMETRICEXCLUSION MODEL

We calculate exactly the diffusion constant associated with the fluctu ations of the current for the partial asymmetric exclusion model on a ring with an arbitrary number of particles and holes. We also give the diffusion constant of a tagged particle on that ring. Our approach ex tends, using the deformed harmonic oscillator algebra, a result alread y known for the fully asymmetric case. In the limit of weak asymmetry, we extract from our exact expression the crossover between the Edward s-Wilkinson and the Kardar-Parisi-Zhang equations in (1 + 1) dimension s.