2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/203405We review our recent analysis of pion-pion scattering data in terms of Roy equations and Forward Dispersion Relations, and present some preliminary results in terms of a new set of once-subtracted coupled equations for partial waves. The first analysis consists of independent fits to the different pion-pion channels that satisfies rather well the dispersive representation. In the second analysis we constrain the fit with the dispersion relations. The latter provides a very precise and model independent description of data using just analyticity, causality and crossing.6 pages, two figures. To appear in the proceedings of the Workshop on Scalar Mesons and Related Topics, Lisbon, Portugal, 11-16 Feb 2008High Energy Physics - Phenomenologytext