DYNAMICAL PHASES IN A CELLULAR-AUTOMATON MODEL FOR EPIDEMIC PROPAGATION

A directed epidemic propagation process is modeled by a deterministic cellular automaton with three local states (infected, immunized and su sceptible). The model is characterized by the choice of the lifetimes of the infected and immunized states as external parameters and by the existence of a continuous control parameter determining the fraction of synchronized infection vectors, The various dynamical regimes obser ved in the fully synchronized stale are described. In a region of para meter space where a statistically stationary disordered regime is obse rved, evidence is given of a phase transition between a localized dama ge and a spreading damage regime.