Peláez Sagredo, José Ramón2023-06-202023-06-202004-12-210217-732310.1142/S0217732304016160https://hdl.handle.net/20.500.14352/51732©World Scientific Publ Co Pte Ltd. I thank A. Andrianov, D. Espriu, A. Gómez Nicola, F. Kleefeld, R. Jaffe, E. Oset, J. Soto and M. Uehara for their comments and support from the Spanish CICYT projects, BFM2000-1326, BFM2002-01003 and the E.U. EURIDICE network contract no. HPRN-CT-2002-00311.By means of unitarized Chiral Perturbation Theory it is possible to obtain a remarkable description of meson-meson scattering amplitudes up to 1.2 GeV, and generate poles associated to scalar and vector resonances. Since Chiral Perturbation Theory is the QCD low energy effective theory, it is then possible to study its large N_c limit where q q̅ states are easily identified. The vectors thus generated follow closely a q q̅ behavior, whereas the light scalar poles follow the large-N-c behavior expected for a dominant tetraquark or two-meson structure.engjournal articlehttp://dx.doi.org/10.1142/S0217732304016160http://www.worldscientific.comhttp://arxiv.org/abs/hep-ph/0411107open access51-73π-π-scatteringInverse amplitude methodMulti-quark hadronsKpi scatteringPhase-shiftOne-loopMesonSigmaResonancesDecaysFísica-Modelos matemáticosFísica matemática