FERMI SEA EFFECTS ON PION AND KAON PROPERTIES IN THE NAMBU-JONA-LASINIO MODEL

We study modifications of hadronic properties in dense nuclear and neu tron matter, in the context of a generalized three-flavor Nambu-Jona-L asinio model, focussing mainly on Fermi sea effects. In symmetric nucl ear matter, we observe the splitting between K+/- and the occurrence o f a low-lying K- branch at baryonic densities around 0.4 times normal nuclear matter density rho(0). This branch is not significantly affect ed by the inclusion of strange matter in the medium while the flavor a symmetry is preserved. A similar pi(+) branch is found in neutron matt er at neutron densities around 0.3 rho(0), These low-lying modes are p anicle-hole excitations of the Fermi sea and decrease smoothly with de nsity. In any case, the vacuum doss not exhibit signs of instability a ssociated with boson condensation. (C) 1997 Elsevier Science B.V.