2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54440The phase structure of a $(2+1)$ - dimensional model of relativistic fermions with a four fermi interaction is analyzed in the strong coupling regime using the large $N$ perturbation theory. It is shown that, this model exhibits a low temperature superconducting phase due to the vortex-anti vortex binding via Kosterlitz-Thouless mechanism. Above a critical temperature, vortices unbind and superconductivity is destroyed; at a still higher temperature the vacuum expectation value of a neutral order parameter vanishes. The ground state respects parity and time reversal symmetries.10 pages, RevtexHigh Energy Physics - TheoryCondensed Mattertext