Renormalization of Nonequilibrium Systems with Critical Stationary States

We introduce the general formulation of a renormalization method suitable to study the critical properties of nonequilibrium systems with steady states: the dynamically driven renormalization group. We renormalize the time evolution operator by computing the rescaled time transition rate between coarse grained states. The obtained renormalization equations are coupled to a stationarity condition which provides the approximate nonequilibrium statistical weights of steady-state configurations to be used in the calculations. In this way we are able to write recursion relations for the parameter evolution under scale change, from which we can extract numerical values for the critical exponents. This general framework allows the systematic analysis of several models showing self-organized criticality in terms of usual concepts of phase transitions and critical phenomena.