EQUATION OF STATE FOR NEUTRON STARS WITH HYPERONS AND QUARKS IN THE RELATIVISTIC HARTREE–FOCK APPROXIMATION

Abstract

We construct the equation of state (EoS) for neutron stars explicitly\nincluding hyperons and quarks. Using the quark-meson coupling model with\nrelativistic Hartree-Fock approximation, the EoS for hadronic matter is derived\nby taking into account the strange ($\\sigma^{\\ast}$ and $\\phi$) mesons as well\nas the light non-strange ($\\sigma$, $\\omega$, $\\vec{\\pi}$ and $\\vec{\\rho}$)\nmesons. Relevant coupling constants are determined to reproduce the\nexperimental data of nuclear matter and hypernuclei in SU(3) flavor symmetry.\nFor quark matter, we employ the MIT bag model with one-gluon-exchange\ninteraction, and Gibbs criteria for chemical equilibrium in the phase\ntransition from hadrons to quarks. We find that the strange vector ($\\phi$)\nmeson and the Fock contribution make the hadronic EoS stiff, and that the\nmaximum mass of a neutron star can be consistent with the observed mass of\nheavy neutron stars even if the coexistence of hadrons and quarks takes place\nin the core. However, in the present calculation the transition to pure quark\nmatter does not occur in stable neutron stars. Furthermore, the lower bound of\nthe critical chemical potential of the quark-hadron transition at zero\ntemperature turns out to be around 1.5 GeV in order to be consistent with the\nrecent observed neutron star data.\n