2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/214793We study the renormalization of normal mixing matrices, which includes hermitian and unitary matrices as particular cases. We give a minimal, multiplicative parametrization of counterterms, and compute the renormalized Lagrangian to one-loop order in several models with N species of fermions, both in on-shell and MS schemes. In on-shell scheme the mass-degenerate case is considered separately.23+1 LaTeX pages, no figures, uses amslatex, amsfontsHigh Energy Physics - Phenomenologytext