2-DIMENSIONAL SELF-ORGANIZED TRANSITIONS FOR PROPAGATION IN RANDOM-MEDIA

A simple so-called dynamic epidemic model, for the evolution of an adv ancing interface through a two-dimensional medium containing mobile im purities is investigated. A short range repulsion between the front an d the impurities leads to an aggregation process along the front, and to trapping of aggregates. The pattern of trapped impurities is found to be self-organized. The critical concentration of impurity for growt h blocking on a square lattice is 0.56. The kinetics of this self-orga nization is analyzed and discussed.