FADDEEV APPROACH TO THE NUCLEON IN THE NJL MODEL

The nucleon and the delta are described as solutions of the relativist ic Faddeev equation in the NJL model. We discuss the dependence of the baryon masses on the particular form of the four-Fermi interaction La grangians. Using the quark-diquark wave function, we calculate some bo und state matrix elements such as the axial coupling constants, magnet ic moments of the nucleon, the pion-nucleon sigma term and the proton- neutron mass difference. We also try to compare two pictures of descri bing the baryons in the NJL model, i.e. the mean-field approximation a nd the relativistic Faddeev approach. As a first step, we discuss how to improve the mean-field approximation by introducing an effective in teraction. We also discuss the perturbative estimate of the deformatio n of the 'vacuum' in the Faddeev approach.