Equation of state for neutron star matter with NJL model and Dirac-Brueckner-Hartree-Fock approximation

TL;DR

This paper models the neutron star interior by combining quark and hadron phases using NJL and Dirac-Brueckner-Hartree-Fock methods, analyzing how different crossover parameters affect star mass and radius.

Contribution

It introduces a combined equation of state for neutron stars using NJL and Dirac-Brueckner-Hartree-Fock models, exploring the impact of crossover parameters on stellar properties.

Findings

The equation of state predicts maximum neutron star masses consistent with observations.

Different crossover parameters significantly influence the star's radius.

The model provides insights into the hadron-quark transition within neutron stars.

Abstract

As the interior density of a neutron star can become very high, it has been expected and discussed that quark matter may exist inside it. To describe the transition from hadron to quark phases (and vice versa), there are mainly two methods; one is the first-order phase transition, and the other is the crossover phenomenon. In the present study, using the flavor-SU (3) NJL model with the vector coupling interaction, we have calculated the equation of state for the quark phase at high density. Furthermore, for the hadron phase at low density, we have used two kinds of the equations of state; one is a relatively soft one by the QHD model, and the other is a stiff one calculated with relativistic Brueckner-Hartree-Fock approximation. Using those equations of state for the two phases, we have investigated the influence of various choices of parameters concerning the crossover region on the mass and radius of a neutron star.