SEA AND VALENCE QUARKS IN THE NAMBU-JONA-LASINIO MODEL

Using proper-time regularization the Nambu-Jona-Lasinio model in the chiral invariant SU(2)-sector with scalar and pseudoscalar couplings is solved in the zero-boson-loop approximation for baryon number B = 1. The cut-off Λ is fixed to reproduce the pion decay constant. The B = 1 solution is obtained by means of a chemical potential in the generating functional and by separating the valence contribution from the quark one-loop contribution. For a given chiral profile the behavior of the solutions in dependence on the quark meson coupling is discussed and the role of the destabilizing fourth order terms of the heat kernel expansion is clarified. It is shown that for physically relevant coupling constants the present Nambu-Jona-Lasinio model is intimately related to the valence quark approximation of the linear chiral soliton model. The renormalized one-quark-loop approach to the linear chiral soliton model turns out to be different. It is demonstrated that in the SU(2)-sector with scalar and pseudoscalar couplings the Skyrme model is not an approximation to the Nambu-Jona-Lasinio model and vice versa. © 1990.