Nature of light scalar mesons from their large-Nc behavior

We show how to obtain information about the states of an effective field theory in terms of the underlying fundamental theory. In particular, we analyze the spectroscopic nature of meson resonances from the meson-meson scattering amplitudes of the QCD low energy effective theory, combined with the expansion in the large number of colors. The vectors follow a qq behavior, whereas the sigma, kappa, and f0(980) scalars disappear for large Nc, in support of a q q qq-like nature. The a0 shows a similar pattern, but the uncertainties are large enough to accommodate both interpretations.