2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49243I : Chiral Perturbation Theory is introduced and its applications to semileptonic and nonleptonic kaon decays are discussed. II: The method of large $N_c$ is used to calculate $K\toππ$ nonleptonic matrix elements, in particular the matching procedure between long and short-distance evolution that takes all scheme dependence correctly into account is discussed. Numerical results reproduce the $ΔI=1/2$ rule without the introduction of any free parameters.Talk presented at Kaon99, Chicago, June 20-27, 1999, 11 pagesHigh Energy Physics - Phenomenologytext