2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54698Electric-magnetic duality allows to calculate the central charges of N=2 supersymmetric theories with massless hypermultiplets as derivatives of simple modular forms. The procedure reproduces the Seiberg-Witten results for N_f=0,2,3 in a uniform way, but indicates open problems for N_f=1.4 pages, plain TeXHigh Energy Physics - Theorytext