Rare event statistics in reaction-diffusion systems.

We present an efficient method to calculate probabilities of large deviations from the typical behavior (rare events) in reaction-diffusion systems. This method is based on a semiclassical treatment of an underlying "quantum" Hamiltonian, encoding the system's evolution. To this end, we formulate the corresponding canonical dynamical system and investigate its phase portrait. This method is presented for a number of pedagogical examples.