2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/46786A review of the recent results obtained in the Nambu -- Jona-Lasinio model is given. In particular, the effect of screening of meson fields at finite temperature or density is analyzed and the formulation of a chirally invariant transport theory for quark matter is presented.128 pages (35 figures), Latex, uses psfigHigh Energy Physics - Phenomenologytext