2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54482The effective Lagrangian of QED coupled to dyons is calculated. The resulting generalization of the Euler-Heisenberg Lagrangian contains non-linear $P$- and $T$-nonivariant (but $C$ invariant) terms corresponding to the virtual pair creation of dyons. As examples, the amplitudes for photon splitting and photon coalescence are calculated.7 pages, LaTexHigh Energy Physics - Theorytext