BINDING-ENERGIES IN WEAKLY COUPLED (2+1)-DIMENSIONAL QUANTUM-FIELD THEORIES

We calculate the binding energy of the two-particle threshold bound state in the (2 + 1)-dimensional Gross-Neveu model. This model was recently shown to be renormalizable within the 1/N expansion. The binding energy is found to be DELTA-E = 4me-8nf where m is the mass of the elementary fermion and N(f) is the number of flavors. The general question of consistency of the perturbation theory within the framework of the Bethe-Salpeter equation is discussed.