Hadron–Quark Phase Transition in the SU (3) Local Nambu–Jona-Lasinio (NJL) Model with Vector Interaction

Grigor Alaverdyan

doi:10.3390/sym13010124

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 the scalar-isovector δ-meson effective field is adopted to describe the hadronic matter phase. It is shown that the larger the vector coupling constant GV, 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 that lead to a phase transition in nonstrange 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, 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.

Highlights

The study of the thermodynamic properties and constituent composition of strongly interacting matter at extremely high density/temperature is important for understanding many phenomena both in microscopic and macroscopic worlds
Another observational manifestation of a quark phase transition is an abrupt change in the stellar radius, when the accretion of matter onto the star increases the central pressure to a critical value, resulting in a quark core being formed in the center of the star [7]
We present the numerical results obtained according to the scheme described in the previous section for electrically neutral quark matter in beta equilibrium

Summary

Introduction

The study of the thermodynamic properties and constituent composition of strongly interacting matter at extremely high density/temperature is important for understanding many phenomena both in microscopic and macroscopic worlds. In the region of extremely high densities and low temperatures, compact stars are the main source that enriches our understanding about the structure of the matter [1,2,3,4]. The thermal evolution of compact stars is an example of such a process [5,6] Another observational manifestation of a quark phase transition is an abrupt change in the stellar radius, when the accretion of matter onto the star increases the central pressure to a critical value, resulting in a quark core being formed in the center of the star [7]

Objectives

Results

Conclusion