Hadron-quark phase transition in the SU(3) local Nambu-Jona-Lasinio (NJL) model with vector interaction

TL;DR

This paper investigates the hadron-quark phase transition in neutron stars using the SU(3) NJL model with vector interactions, revealing how vector coupling influences the transition density, EOS stiffness, and core stability.

Contribution

It introduces a combined NJL and RMF framework to analyze phase transitions in neutron star matter, highlighting the impact of vector coupling on transition properties.

Findings

Higher vector coupling lowers strange quark threshold density.

Small vector coupling leads to ambiguous mass-chemical potential relations.

Infinitesimal quark cores are stable within the model.

Abstract

We study the hadron-quark hybrid equation of state (EOS) of compact-star matter. The Nambu-Jona-Lasinio (NJL) local SU(3) model with vector-type interaction is used to describe the quark matter phase, while the relativistic mean field (RMF) theory with scalar-isovector $\delta$-meson effective field adopted to describe the hadronic matter phase. It is shown that the larger the vector coupling constant , the lower the threshold density for the appearance of strange quarks. For a sufficiently small value of the vector coupling constant, the functions of the mass dependence on the baryonic chemical potential have regions of ambiguity which leads to a phase transition in non-strange quark matter with an abrupt change in the baryon number density. We show that within the framework of the NJL model, the hypothesis on the absolute stability of strange quark matter is not realized. In order to describe the phase transition from hadronic matter to quark matter, the Maxwell's construction is applied. It is shown that the greater the vector coupling, the greater the stiffness of the EOS for quark matter and the phase transition pressure. Our results indicate that the infinitesimal core of the quark phase, formed in the center of the neutron star, is stable.