  We examine the leading-Nc behavior of the masses and transition matrix
elements of some low-lying, few-particle configurations in QCD. A truncation of
the Fock space produces an effective, symmetric Hamiltonian that we
diagonalize. The lowest eigenvalue is identified as the sigma meson if the
Hamiltonian is chosen to represent the scalar sector. As an application, the
coefficients of the Nc powers are then fit to two-loop Unitarized SU(2) Chiral
Perturbation Theory results for the sigma mass and width as a function of the
number of colors, and we show that those results can be accommodated using the
QCD Nc dependence previously derived for matrix elements, without the need for
unnatural parameters or fine tunings. Finally, we show a very preliminary good
quality fit, estimating the proportion of tetraquark/molecule-like (dominant),
q-anti-q-like (subdominant) and exotic-like (marginal) configurations in the
sigma.
