Equation of state for neutron stars with hyperons using relativistic mean-field models

by Dr Tsuyoshi Miyatsu (Soongsil University, 숭실대학교)

Monday Apr 29, 2013, 5:00 PM → 6:00 PM Asia/Seoul

201-4호 (제1과학관)

The survey of a so-called two-solar-mass neutron star (PSR J1614-2230) puts a severe constraint on the equation of state for nuclear matter. Generally speaking, the inclusion of other degrees of freedom, such as hyperon admixture, softens an equation of state, and the maximum mass of neutron stars is thus reduced. In fact, the mass of J1614-2230 cannot be accounted for the equations of state which have been calculated so far. Thus, it is urgent to construct an equation of state which is consistent with both of the terrestrial nuclear experiments and the astrophysical observations. In this talk, I present a solution of this problem. Using several relativistic mean field models (such as GM1, GM3, NL3, TM1, FSUGold and IU-FSU) as well as the quark-meson coupling (QMC) and chiral quark-meson coupling (CQMC) models, we calculate the particle fractions, the equation of state, the maximum mass and radius of a neutron star within relativistic Hartree approximation. In determining the couplings of the isoscalar, vector mesons to the octet baryons, we examine the extension of SU(6) spin-flavor symmetry to SU(3) flavor symmetry. Furthermore, we consider the strange mesons, and study how they affect the equation of state. We find that the equation of state in SU(3) symmetry can sustain a neutron star with mass of (1.8~2.1) M_solar even if hyperons exist inside the core of a neutron star. In addition, the strange vector meson and the variation of baryon structure in matter also play important roles in supporting a massive neutron star.