mₚi and Nc dependence of resonances from Unitarized Chiral Perturbation Theory

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We review our studies on the rho and sigma resonances properties derived from the Inverse Amplitude Method. In particular, we study the leading 1/Nc behavior of the resonances masses and widths and their evolution with changing mπ. The 1/Nc expansion gives a clear definition of qq states, which is neatly satisfied by the ρ but not by the sigma, showing that its dominant component is not qq. The mπ dependence of the resonance properties is relevant to connect with lattice studies. We show that our predictions compare well with some lattice results and we find that the rho-pi-pi coupling constant is mπ independent, in contrast with the sigma-pi-pi coupling, that shows a strong mπ dependence.