Kaon condensation in hyperonic matter and properties of neutron stars

The equation of state (EOS) of kaon condensation in hyperonic matter, where hyperons (Λ,Σ) are mixed in the ground state of neutron-star matter, is investigated. P-wave kaon-baryon interactions are included as well as s-wave ones by the use of effective chiral Lagrangian. It is shown that kaon condensates appear with finite momentum, stemming from the attractive p-wave kaon-baryon interactions. However, in the fully-developed phase, the s-wave kaon-baryon interactions control the EOS, and kaon condensation becomes of an s-wave type at higher density. Due to a considerable softening of the EOS caused by both hyperon-mixing and kaon condensates, the energy of the system has a local minimum, which leads to a metastable configuration of self-bound kaon-condensed star in addition to a usual kaon-condensed star obtained by Maxwell's construction.