Kaonic modes in hyperonic matter and p-wave kaon condensation

Abstract

Kaon excitations (kaonic modes) are investigated in hyperonic matter, where hyperons ($Λ$, $Σ^-$, $Ξ^-$) are mixed in the ground state of neutron-star matter. $P$-wave kaon-baryon interactions as well as the s-wave interactions are taken into account within chiral effective Lagrangian, and the nonrelativistic effective baryon-baryon interactions are incorporated. When the hyperon $Λ$ is more abundant than the proton at high baryon density, a proton-particle-$Λ$-hole mode, which has the $K^+$ quantum number, appears in addition to other particle-hole modes with the $K^-$ quantum number. It is shown that the system becomes unstable with respect to a spontaneous creation of a pair of the particle-hole modes with $K^+$ and $K^-$ quantum numbers, stemming from the p-wave kaon-baryon interaction. The onset density of this p-wave kaon condensation may be lower than that of the s-wave $K^-$ condensation.