ON MATRIX PRODUCT GROUND-STATES FOR REACTION-DIFFUSION MODELS

We discuss a new mechanism leading to a matrix product form for the st ationary state of one-dimensional stochastic models. The corresponding algebra is quadratic and involves four different matrices. For the ex ample of a coagulation-decoagulation model explicit four-dimensional r epresentations are given and exact expressions for various physical qu antities are recovered. We also find the general structure of n-point correlation functions at the phase transition.