2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/187037We present a derivation of the bosonic contribution to the thermodynamical potential of four fermion models by means of a $1/N_c$-expansion of the functional integral defining the partition function. This expansion turns out to be particularly useful to correct the mean field approximation expecially at low temperatures, where the relevant degrees of freedom are low-mass bosonic excitations (pseudogoldstones).9 pages, latex, no figuresHigh Energy Physics - PhenomenologyHigh Energy Physics - TheoryNuclear Theorytext