2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/192801We discuss the lightest scalar resonances, $f_0(600)$, $κ(800)$, $a_0(980)$ and $f_0(980)$ in the extended Nambu Jona-Lasinio model. We find that the model parameters can be tuned, but unnaturally, to accommodate for those scalars except the $f_0(980)$. We also discuss problems encountered in the K Matrix unitarization approximation by using $N_c$ counting technique.23 pages 3 eps figures, To appear in Nucl. Phys. AHigh Energy Physics - PhenomenologyNuclear Theorytext