Nambu - Jona-Lasinio-like models and the low-energy effective action of QCD

We present a derivation of the low energy effective action of an extended Nambu Jona-Lasinio (ENJL) model to $O(p^4)$ in the chiral counting. Two alternative scenarios are considered on how the ENJL model could originate as a low energy approximation to QCD. The low energy effective Lagrangian we derive includes the usual pseudoscalar Goldstone modes, as well as the lower scalar, vector and axial-vector degrees of freedom. By taking appropriate limits, we recover most of the effective low-energy models discussed in the literature; in particular the gauged Yang-Mills vector Lagrangian, the Georgi-Manohar constituent quark-meson model, and the QCD effective action approach model. Another property of the ensuing effective Lagrangian is that it incorporates most of the short-distance relations which follow from QCD. (We derive these relations in the presence of all possible gluonic interactions to leading order in the $1/N_c$-expansion.) Finally the numerical predictions are compared to the experimental values of the low energy parameters