  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 possible then
to study its large Nc limit where qqbar states are easily identified. The
vectors thus generated follow closely a qqbar behavior, whereas the light
scalar poles follow the large Nc behavior expected for a dominant tetraquark or
two-meson structure.
