2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55732Some new expressions are found, concerning the effective action as a regularized path-integral for Dirac's spinors in {\it 3+1} dimensions, in the presence of general uniform (i.e., constant and homogeneous) electric and magnetic fields. The rate of $e^+e^-$ pairs production is computed and briefly discussed.4 pages, LaTeX, no Figures, to appear in the Proceedings of the 6-th International Conference on Path-Integrals from peV to TeV, FirenzeHigh Energy Physics - Theorytext