2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54181We review the closed time path formalism of Schwinger using a path integral approach. We apply this formalism to the study of pair production from strong external fields as well as the time evolution of a nonequilibrium chiral phase transition.19 pages, 4 figuresHigh Energy Physics - Theorytext