2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/179049Motivated by the 1/Nc expansion, we present a simple model of pion-pion scattering as a sum of a `current-algebra' contact term and resonant pole exchanges. The model preserves crossing symmetry as well as unitarity up to 1.2 GeV. Key features include chiral dynamics, vector meson dominance, a broad low energy scalar (sigma) meson and a `Ramsauer-Townsend' mechanism for the understanding of the 980 MeV region. We discuss in detail the `regularization' (corresponding to rescattering effects) necessary to make all these nice features work.35 pages (LaTeX), 13 PostScript figures are included as uuencoded-compressed-tarHigh Energy Physics - PhenomenologyNuclear Theorytext