Rare events and phase transitions in reaction diffusion systems

I shall discuss a way to evaluate tails of the probability distribution functions in stochastic reaction-diffusion models. The method is based on the semi-classical treatment of a proper ``quantum'' field theory, which may be associated with reaction-diffusion systems. The same set of ideas may be applied to a classification of non-equilibrium phase transitions, taking place in these models. \newline \newline V. Elgart and A. Kamenev, Classification of phase transitions in reaction--diffusion systems, Phys. Rev. E 74, 041101 (2006). \newline V. Elgart and A. Kamenev, Rare Events Statistics in Reaction--Diffusion Systems, Phys. Rev. E. 70, 041106 (2004).