Fermi sea effects on pion and kaon properties in the Nambu-Jona-Lasinio model

We study modifications of hadronic properties in dense nuclear and neutron matter, in the context of a generalized three-flavor Nambu-Jona-Lasinio model, focussing mainly on Fermi sea effects. In symmetric nuclear matter, we observe the splitting between K^± and the occurrence of a low-lying K⁻ branch at baryonic densities around 0.4 times normal nuclear matter density ϱ₀. This branch is not significantly affected by the inclusion of strange matter in the medium while the flavor asymmetry is preserved. A similar π⁺ branch is found in neutron matter at neutron densities around 0.3ϱ₀. These low-lying modes are particle-hole excitations of the Fermi sea and decrease smoothly with density. In any case, the vacuum does not exhibit signs of instability associated with boson condensation.