We develop new hyperon equation of state (EoS) tables for core-collapse supernova simulations and neutron stars. These EoS tables are based on a densitydependent relativistic hadron field theory where baryon-baryon interaction is mediated by mesons, using the parameter set DD2 from Typel et al. (2010) for nucleons. Furthermore, light and heavy nuclei along with the interacting nucleons are treated in the nuclear statistical equilibrium model of Hempel and Schaffner-Bielich which includes excluded volume effects. Of all possible hyperons, we consider only the contribution of Λs. We have developed two variants of hyperonic EoS tables: in the npΛφ case the repulsive hyperon-hyperon interaction mediated by the strange φ meson is taken into account, and in the npΛ case it is not. The EoS tables for the two cases encompass wide range of density (10 −12 to ∼ 1 fm −3 ), temperature (0.1 to 158.48 MeV), and proton fraction (0.01 to 0.60). The effects of Λ hyperons on thermodynamic quantities such as free energy per baryon, pressure, or entropy per baryon are investigated and found to be significant at higher densities.The cold, β-equilibrated EoS (with the crust included self-consistently) results in a 2.1 M ⊙ maximum mass neutron star for the npΛφ whereas that for the npΛ case is 1.95 M ⊙ . The npΛφ EoS represents the first supernova EoS table involving hyperons that is directly compatible with the recently measured 2 M ⊙ neutron stars.

The formation of K − andK 0 condensation in β-equilibrated hyperonic matter is investigated within a relativistic mean field model. In this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by the exchange of mesons. It is found that antikaon condensation is not only sensitive to the equation of state but also to antikaon optical potential depth. For large values of antikaon optical potential depth, K − condensation sets in before the appearance of negatively charged hyperons. We treat K − condensation as a first order phase transition. The Gibbs criteria and global charge conservation laws are used to describe the mixed phase. Nucleons and Λ hyperons behave dynamically in the mixed phase. A second order phase transition tō K 0 condensation occurs in the pure K − condensed phase. Along with K − condensation,K 0 condensation makes the equation of state softer thus resulting in smaller maximum mass stars compared with the case without any condensate. This equation of state also leads to a stable sequence of compact stars called the third family branch, beyond the neutron star branch. The compact stars in the third family branch have different compositions and smaller radii than that of the neutron star branch. PACS: 26.60.+c, 21.65.+f, 97.60.Jd, 95.30.Cq

We investigate the condensation of $\bar K^0$ meson along with $K^-$ condensation in the 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 $K^-$ condensation is shifted considerably to higher density whereas that of $\bar K^0$ condensation is shifted slightly to higher density with respect to that of the neutrino free case. The onset of $K^-$ condensation always occurs earlier than that of $\bar K^0$ condensation. A significant region of maximum mass protoneutron stars is found to contain $\bar K^0$ condensate for larger values of the antikaon potential. With the appearance of $\bar K^0$ condensation, there is a region of symmetric nuclear matter in the inner core of a protoneutron star. It is found that the maximum mass of a protoneutron star containing $K^-$ and $\bar K^0$ condensate is greater than that of the corresponding neutron star. We revisit the implication of this scenario in the context of the metastability of protoneutron stars and their evolution to low mass black holes.Comment: 26 pages; Revtex; 8 figures include

We investigate first order phase transitions from β-equilibrated hadronic matter to color flavor locked quark matter in compact star interior. The hadronic phase including hyperons and Bose-Einstein condensate of K − mesons is described by the relativistic field theoretical model with density dependent meson-baryon couplings. The early appearance of hyperons and/or BoseEinstein condensate of K − mesons delays the onset of phase transition to higher density. In the presence of hyperons and/or K − condensate, the overall equations of state become softer resulting in smaller maximum masses than the cases without hyperons and K − condensate. We find that the maximum mass neutron stars may contain a mixed phase core of hyperons, K − condensate and color superconducting quark matter. Depending on the parameter space, we also observe that there is a stable branch of superdense stars called the third family branch beyond the neutron star branch. Compact stars in the third family branch may contain pure color superconducting core and have radii smaller than those of the neutron star branch. Our results are compared with the recent observations on RX J185635-3754 and the recently measured mass-radius relationship by X-ray Multi Mirror-Newton Observatory.

The measurement of 1.97 ± 0.04M solar for PSR J1614-2230 and 2.01 ± 0.04M solar for PSR J0348+0432 puts a strong constraint on the neutron star equation of state and its exotic composition at higher densities. In this paper, we investigate the possibility of exotic equation of state within the observational mass constraint of 2M solar in the framework of relativistic mean field model with density-dependent couplings. We particularly study the effect of antikaon condensates in the presence of hyperons on the mass-radius relationship of the neutron star.