Hybrid Stars using the Quark-Meson Coupling and Proper Time NJL Models

TL;DR

This paper models hybrid stars by combining hadronic and quark matter descriptions using the Hartree-Fock quark-meson coupling and NJL models, analyzing their equations of state and implications for neutron star observations.

Contribution

It introduces a crossover transition approach between two phenomenological models for hadronic and quark matter, incorporating quark degrees of freedom in hybrid star modeling.

Findings

Equations of state for hybrid stars are derived and analyzed.

Mass-radius relations for hybrid stars are consistent with observations.

Thermodynamic corrections from interpolation significantly affect the equation of state.

Abstract

Background: At high density deconfinement of hadronic matter may occur leading to quark matter. The immense densities reached in the inner core of massive neutron stars may be sufficient to facilitate the transition. Purpose: To investigate a crossover transition between two phenomenological models which epitomise QCD in two different regimes, while incorporating the influence of quark degrees of freedom in both. Method: We use the Hartree-Fock quark-meson coupling model and the proper time regularised three flavour NJL model to describe hadronic and quark matter, respectively. Hybrid equations of state are obtained by interpolating the energy density as a function of total baryonic density and calculating the pressure. Results: Equations of state for hadronic, quark and hybrid matter and the resulting mass versus radius curves for hybrid stars are shown, as well as other relevant physical quantities such as species fractions and the speed of sound in matter. Conclusions: The observations of massive neutron stars can certainly be explained within such a construction. However, the so-called thermodynamic correction arising from an interpolation method can have a considerable impact on the equation of state. The interpolation dependency of and physical meaning behind such corrections require further study.