Deconfinement of neutron star matter within the Nambu-Jona-Lasinio model

TL;DR

This paper investigates the deconfinement transition from hadronic to quark matter in neutron stars using a two-phase model with the NJL effective theory, identifying critical masses and transition conditions relevant for neutron star composition.

Contribution

It introduces a two-phase model incorporating color and flavor conservation during deconfinement, providing new insights into the transition conditions and critical masses in neutron stars.

Findings

Critical mass for quark core formation: 1.5-1.8 solar masses.

Deconfinement transition occurs at specific free-energy densities.

Transition influences neutron star structure and evolution.

Abstract

We study the deconfinement transition of hadronic matter into quark matter under neutron star conditions assuming color and flavor conservation during the transition. We use a two-phase description. For the hadronic phase we use different parameterizations of a non-linear Walecka model which includes the whole baryon octet. For the quark matter phase we use an SU(3)_f Nambu-Jona-Lasinio effective model including color superconductivity. Deconfinement is considered to be a first order phase transition that conserves color and flavor. It gives a short-lived transitory colorless-quark-phase that is not in beta-equilibrium, and decays to a stable configuration in tau ~ tau_{weak} ~ 10^{-8} s. However, in spite of being very short lived, the transition to this intermediate phase determines the onset of the transition inside neutron stars. We find the transition free-energy density for temperatures typical of neutron star interiors. We also find the critical mass above which compact stars should contain a quark core and below which they are safe with respect to a sudden transition to quark matter. Rather independently on the stiffness of the hadronic equation of state (EOS) we find that the critical mass of hadronic stars (without trapped neutrinos) is in the range of ~ 1.5 - 1.8 solar masses. This is in coincidence with previous results obtained within the MIT Bag model.