CHIRALLY SYMMETRICAL O(1/N-C) CORRECTIONS TO THE NAMBU-JONA-LASINIO MODEL

(W)e develop an extended chirally symmetric self-consistent approximation scheme to the Nambu-Jona-Lasinio model, that corresponds to O(1/N-C) corrections to the usual Hartree + random phase approximations. This scheme amounts to adding ''meson cloud'' contributions self-consistently to the quark self-energy and the meson polarization functions in a manner suggested by the weakly interacting nature of the quark and collective meson degrees of freedom of the NJL model in the large N-C limit. We demonstrate explicitly that this scheme fulfills all the chiral symmetry theorems, namely the Goldstone theorem, the Goldberger-Treiman relation, and the conservation of the quark axial current. We explore the corrections to the quark self-energy and scalar condensate, as well as to the pion polarization function and the weak decay constant f(pi). The numerical evaluation of these corrections is presented and discussed. (C) 1995 Academic Press, Inc.