Exploring the first-order phase transition in neutron stars using the parity doublet model and NJL-type quark model

TL;DR

This study models the first-order phase transition from hadronic to quark matter in neutron stars using the parity doublet and NJL models, analyzing conditions and effects on star properties.

Contribution

It introduces a combined approach with specific parameter constraints to identify when a first-order phase transition occurs in neutron stars.

Findings

Phase transition occurs between 1.9$n_0$ and 2.95$n_0$ for $m_0$=500 MeV.

Higher $m_0$ shifts transition to densities between 2.9$n_0$ and 4.1$n_0$.

Parameter space constraints help understand the transition's impact on neutron star structure.

Abstract

We investigate the possibility and impacts of a first-order phase transition from hadronic matter to quark matter in neutron stars (NSs) using two specific models: the parity doublet model (PDM) for the hadronic phase and the Nambu-Jona-Lasinio (NJL) type model for the quark phase. By combining these models, we construct hybrid equations of state (EOSs) that capture the transition between the two phases. We explore the parameter space of both models to identify the conditions under which a first-order phase transition can occur and study its effects on NS properties. We identify the suitable parameter space and constrain the onset density of the first-order phase transition. For $m_0$ = 500 MeV -- the chiral invariant mass in PDM, the phase transition occurs between 1.9$n_0$ and 2.95$n_0$ and ends between 2.1$n_0$ and 3.6$n_0$. Increasing $m_0$ to 600 MeV shifts the phase transition to higher densities, occurring between 2.9$n_0$ and 4.1$n_0$ and ending between 3.4$n_0$ and 4.6$n_0$.