Quark matter symmetry energy and quark stars

TL;DR

This paper introduces an extended quark matter model incorporating isospin dependence, which better explains the properties of massive quark stars and aligns with recent pulsar observations.

Contribution

The study develops the CIDDM model to include isospin effects, significantly impacting quark matter symmetry energy and quark star characteristics, aligning theoretical predictions with observed massive pulsars.

Findings

Including isospin dependence affects quark matter symmetry energy.

Quark stars with masses around 2 solar masses are compatible with the CIDDM model.

Two-flavor u-d quark matter symmetry energy should be at least twice that of a free quark gas.

Abstract

We extend the confined-density-dependent-mass (CDDM) model to include isospin dependence of the equivalent quark mass. Within the confined-isospin-density-dependent-mass (CIDDM) model, we study the quark matter symmetry energy, the stability of strange quark matter, and the properties of quark stars. We find that including isospin dependence of the equivalent quark mass can significantly influence the quark matter symmetry energy as well as the properties of strange quark matter and quark stars. While the recently discovered large mass pulsars PSR J1614-2230 and PSR J0348+0432 with masses around $2M_{\odot}$ cannot be quark stars within the CDDM model, they can be well described by quark stars in the CIDDM model. In particular, our results indicate that the two-flavor $u$-$d$ quark matter symmetry energy should be at least about twice that of a free quark gas or normal quark matter within conventional Nambu-Jona-Lasinio model in order to describe the PSR J1614-2230 and PSR J0348+0432 as quark stars.