The stability of nuclear matter in the Nambu-Jona-Lasinio model

Using the Nambu-Jona-Lasinio model to describe the nucleon as a quark-diqua rk state, we discuss the stability of nuclear matter in a hybrid model for the ground state at finite nucleon density. It is shown that a simple exten sion of the model to simulate the effects of confinement leads to a scalar polarizability of the nucleon. This, in turn, leads to a less attractive ef fective interaction between the nucleons, helping to achieve saturation of the nuclear matter ground state. It is also pointed out that that the same effect naturally leads to a suppression of "Z-graph" contributions with inc reasing scalar potential. (C) 2001 Elsevier Science B.V. All rights reserve d.