2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/215078We report on two recent results based on the evaluation of five-loop massless propagators in QCD and QED: (i) corrections of order $α_s^4$ to the absorptive part of the polarization function in QCD with $n_f=3$;(ii) the five-loop contribution to the $β$ function of quenched QED.7 pages, contribution to the 8-th International Symposium on Radiative Corrections (RADCOR), October 1-5 2007, Florence, ItalyHigh Energy Physics - Phenomenologytext