Functional integral formulation of the Thirring model with two fermion species

A two-dimensional Abelian model with quartic interaction among two species of Fermi fields is analyzed through a functional integral formulation. We consider the bosonization of the generating functional of the model in order to establish the fermion-boson mapping in the Hilbert space of states. The grand partition function of the statistical mechanical system associated with the effective bosonized theory is obtained and the corresponding exact equation of state exhibits a critical line characterizing a Kosterlitz-Thouless phase transition.