DAMAGE SPREADING AND CRITICAL BEHAVIOUR OF CELLULAR AUTOMATA MODELS OF NONEQUILIBRIUM PHASE TRANSITION

摘要

Simple cellular automata models of nonequilibrium phase transitions are studied. These markovian models are characterized by the fact that they have two possible states at each site and one adsorbing phase. One shows that below the transition point, the Hamming distance is exactly related to the one and two-point nonequilibrium correlation function. The divergence of the Hamming distance at criticality gives a precise determination of the transition point. Furthermore, the study of the order parameter near criticality shows that the critical exponent #beta# is not always compatible with the exponent of directed percolation, in contradistinction to a conjecture of Grassberger.