COMPETING 2-SPECIES DIRECTED PERCOLATION

We study an extension of conventional directed percolation (DP) with two species (A and B) using mean-field and Monte Carlo methods. The densities of the two species in the steady-state exhibit phase transitions which are due both to simple percolation and to competition between the species. In 1 + 1 dimensions, as well as a simple DP transition, there is a line of first-order transitions between pure-A and pure-B phases. The phase diagram in 2 + 1 dimensions agrees qualitatively with that obtained from mean-field calculations, with second-order transitions between pure and mixed phases. Preliminary studies suggest that the critical exponents are in the same universality class as (one-species) DP.