2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55456The importance of a rigorous definition of the singular degree of a distribution is demonstrated on the case of two-dimensional QED (Schwinger model). Correct mathematical treatment of second order vacuum polarization in the perturbative approach is crucial in order to obtain the Schwinger mass of the photon by resummation.5 pages, LaTeX, no figures. To appear in Lett. Math. PhysHigh Energy Physics - Theorytext