2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/52852The prediction of a massless boson after the spontaneous chiral symmetry breaking in the classic paper of Nambu and Jona-Lasinio (NJL) is shown to be wrong. Their mistake is due to a carelessly employed perturbative vacuum when evaluating the boson mass by summing up one loop Feynman diagrams. With the proper symmetry broken vacuum, one obtains a finite boson mass depending on the coupling constant $G$.3 pagesHigh Energy Physics - Theorytext