Dispersive chiral approach to Meson-meson dynamics: Spectroscopy results   for light scalars and precision studies
  Dispersive approaches provide model independent description of meson-meson scattering. We first review here the use of dispersion relations to obtain a model independent unitarization of Chiral Perturbation Theory amplitudes, that establish the existence of light scalar mesons and whose leading 1/N_c behavior suggest they ahve a non q-qbar dominant component. We also review the forward dispersion relation checks on conflicting experimental data and the resulting very precise pion-pion scattering scattering amplitudes. 
J. R. Pelaez (U. Complutense de Madrid)