Equation of state for neutron stars with hyperons and quarks in relativistic Hartree-Fock approximation

TL;DR

This paper develops a detailed equation of state for neutron stars including hyperons and quarks using relativistic Hartree-Fock approximation, and finds it can explain heavy neutron star masses without a transition to pure quark matter.

Contribution

It introduces a comprehensive EoS model incorporating hyperons and quarks with relativistic Hartree-Fock, aligning with experimental data and neutron star observations.

Findings

Hadronic EoS is stiffened by strange vector mesons and Fock terms.

Maximum neutron star mass can match observed heavy neutron stars.

Transition to pure quark matter does not occur in stable neutron stars.

Abstract

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