THE NAMBU AND JONA-LASINIO MODEL - ITS IMPLICATIONS FOR HADRONS AND NUCLEI

We review recent developments and applications of the Nambu and Jona-Lasinio model with three quark flavours, based on the SU(3)L (x) SU (3)R (x) U (1)v symmetry of QCD. The model describes dynamical quark mass generation and spontaneous chiral symmetry breaking and includes effects of the axial U(1) anomaly. Mesons emerge as quark-antiquark modes; their spectra and properties are discussed. Properties of constituent quarks as quasi-particles, dressed by their strong interactions, are summarized. The quark-diquark structure of baryons is developed, and a brief summary is given on baryonic solitons as they result from the NJL model. Finally, selected implications for nuclear physics are described, such as the change of hadron structure in a dense and hot nuclear medium.