STEADY-STATE REACTION-DIFFUSION FRONT SCALING FOR MA+NB -] [INERT]

We study the front formed by the reaction mA+nB --> [inert] between opposing currents of A and B, as a function of current density J(--> 0), diffusion constant D, and reaction constant k. We show that the critical dimension is d(c) = 2/(m + n - 1), above which mean-field theory is valid. Below d(c), J --> 0 is equivalent to k --> infinity. Consistency arguments give exact predictions for the scaling exponents when d < d(c). Our results apply also to the case of a front that moves or grows with time, or where the diffusion constants differ.