DISCRETE TO CONTINUOUS-TIME CROSSOVER DUE TO ANISOTROPY IN DIFFUSION-LIMITED 2-PARTICLE ANNIHILATION REACTIONS

The diffusion-limited reaction A + A --> inert with anisotropic hopping on the d = 1 lattice is solved exactly for a simultaneous updating, discrete time-step dynamics. Diffusion-dominated processes slow down as the anisotropy increases. For large times or large anisotropy, one can invoke the appropriate continuum limits. In these limits the effects of the anisotropy on the variation of particle density can be absorbed in time rescaling. However, in other regimes, when the discreteness of the time steps is nonnegligible, the anisotropy effects are nontrivial, although they are always quite small numerically.