ON THE QUESTION OF FINE TUNING IN THE GAUGED NAMBU-JONA-LASINIO MODEL

This paper deals with the question of fine tuning the strength of the four Fermi interaction g in the gauged Nambu-Jona-Lasinio (NJL) model in order to produce a dynamical mass scale Σ0 which is much smaller than the cut-off Λ. We show that in the presence of gauge interaction the fine tuning of g is softened from Σ02 Λ2 to ( Σ02 Λ2)a where a= 1- α αc and αc is the critical value for the gauge coupling that is needed for it to break the chiral symmetry spontaneously by itself. This result is obtained by an analysis of the ladder Schwinger-Dyson equation in the linearized approximation. © 1990.