We propose and solve a Hamiltonian model for multidimensional epistastatic
interactions between beneficial mutations. The model is able to give rise
either to a phase transition between two equilibrium states, without any
coexistence, or exhibits a state where hybrid species can coexist, with gradual
passage from one wild type to another. The transition takes place as a function
of the "tolerance" of the environment, which we define as the amount of noise
in the system.Comment: 3 pages, 2 figures (in seperate files) spelling corrected and a
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