2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56297Generalizing the 't Hooft and Veltman method of unitary regulators, we demonstrate for the first time the existence of local, Lorentz-invariant, physically motivated Lagrangians of quantum-electrodynamic phenomena such that: (i) Feynman diagrams are finite and equal the diagrams of QED but with regularized propagators. (ii) N-point Green functions are causal. (iii) S-matrix relates only electrons, positrons and photons, is unitary and Lorentz-invariant, and conserves charge and total four-momentum.RevTeX, 5 pages, nofigures; changed title and changed and added few sentences to stress that this is an example, and to shortly explain the framework of the original 't Hooft and Veltman regularization methodHigh Energy Physics - Theorytext