Evolution of the A-particle island-B-particle island system at propagation of the sharp annihilation front A+B-->0

We consider diffusion-controlled evolution of the A-particle island-B-particle island system in a semi-infinite medium at propagation of the sharp annihilation front A+B-->0. We show that depending on the initial particle number ratio, the system demonstrates three asymptotic regimes: self-accelerating collapse of one of the islands, synchronous power-law relaxation of both islands, and exponential death of one of the islands at a constant velocity of front propagation. We find asymptotic scaling laws of evolution in these regimes and reveal the limits of their applicability for the cases of mean field and fluctuation fronts.