Antikaon condensation and the metastability of protoneutron stars

Abstract

We investigate the condensation of ${K}^{0}$ mesons along with ${K}^{\ensuremath{-}}$ condensation in neutrino-trapped matter with and without hyperons. Calculations are performed in the relativistic mean field models in which both the baryon-baryon and (anti)kaon-baryon interactions are mediated by meson exchange. In the neutrino-trapped matter relevant to protoneutron stars, the critical density of ${K}^{\ensuremath{-}}$ condensation is shifted considerably to higher density whereas that of ${K}^{0}$ condensation is shifted slightly to higher density with respect to that of the neutrino-free case. The onset of ${K}^{\ensuremath{-}}$ condensation always occurs earlier than that of ${K}^{0}$ condensation. A significant region of maximum mass protoneutron stars is found to contain ${K}^{0}$ condensate for larger values of the antikaon potential. With the appearance of ${K}^{0}$ condensation, there is a region of symmetric nuclear matter in the inner core of a protoneutron star. We note that the gross properties of the protoneutron stars are significantly affected by the antikaon condensation for larger values of the antikaon potential. It is found that the maximum mass of a protoneutron star containing ${K}^{\ensuremath{-}}$ and ${K}^{0}$ condensate is greater than that of the corresponding neutron star. We reexamine the implication of this scenario in the context of the metastability of protoneutron stars and their evolution to low mass black holes.