Hybrid stars and QCD phase transition with a NJL-like model

TL;DR

This paper develops a mean field NJL model to study the QCD phase transition and hybrid star structure, revealing how the equation of state stiffness affects maximum star mass and implications for chiral transition nature.

Contribution

It introduces a phenomenological parameter in a self-consistent NJL model to analyze hybrid star properties and QCD phase transition characteristics.

Findings

Maximum hybrid star mass of 2.40 solar masses achieved.

EOS stiffness increases with parameter α.

Over 2.06 solar-mass neutron stars suggest crossover chiral transition.

Abstract

In this paper, we introduce a self-consistent mean field approximation to study the QCD phase transition and the structure of hybrid stars within the framework of NJL model. In our practice, a phenomenological parameter $\alpha$ is introduced, which reflects the weights of "direct" channel and "exchange" channel under a finite chemical potential. The mass-radius relation is obtained by solving the Tolman-Oppenheimer-Volkoff equation using a crossover equation of state (EOS). We calculate the density distribution in a two solar-mass hybrid star to show the effects of different parameters. We also calculate the tidal Love number $k_2$ and the deformability $(\Lambda)$. It is found that the stiffness of the EOS increases with $\alpha $, which allows us to obtain a hybrid star with a maximum mass of 2.40 solar-mass through our model. The observation of over 2.06 solar-mass neutron stars may indicates that the chiral transition may be a crossover on the whole $T-\mu$ plane.