2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/83221We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, in which two hadrons, either two mesons or a meson and a baryon, in a resonant state are produced in photoproduction processes.10 pages, 2 ps figures. Talk given at the IVth Workshop on "Electromagnetically Induced Two Hadron Emission", Granada (Spain), May 26-29, 1999Nuclear Theorytext