Massive Gross–Neveu model in the leading order of the $1/N$ expansion. Allowance for the temperature and the chemical potential

The massive Gross–Neveu model is treated self-consistently in the leading order of the $1/N$ expansion. The properties of the model when the temperature and the chemical potential are included are studied. It is shown that there exists a critical value of the chemical potential at which the effective mass of the fermion abruptly changes its value.