Time-dependent perturbation theory for nonequilibrium lattice models

We develop a perurbation theory for the asymptotic survival probability of an interacting particle system which can become trapped in an absorbing state. The method is applied to a simple model describing the poisoning of a catalytic surface. Analyais of the resulting series (in powers of the annihilation rate) leads to very precise estimates for the location of the critical point and the order-parameter exponent β. Results for similar models and other expansions are presented briefly.