Time-dependent perturbation theory for diffusive non-equilibrium lattice models

The authors recently presented a perturbation theory for the asymptotic survival probability of an interacting particle system which can become trapped in an absorbing state. They extend the method to a simple diffusive model. Analysis of the resulting series shows that diffusion is an irrelevant perturbation, i.e. it does not change the critical behaviour. Quantitative predictions of the phase boundary are confirmed by results of Monte Carlo simulations.