Quark Matter at High Density based on Extended Confined-isospin-density-dependent-mass Model

TL;DR

This paper explores how including relativistic Coulomb terms in an extended confined-isospin-density-dependent-mass model affects the equation of state of strange quark matter, with implications for neutron star mass and stability.

Contribution

It systematically analyzes the impact of scalar and vector Coulomb terms in the extended CIDDM model on the properties of strange quark matter and neutron star constraints.

Findings

Scalar Coulomb term stiffens the EOS at high densities.

Vector Coulomb term results in a softer EOS.

Model with scalar Coulomb better matches 2 M_sun pulsar mass constraints.

Abstract

We investigate the effect of the inclusion of relativistic Coulomb terms in a confined-isospin-density-dependent-mass (CIDDM) model of strange quark matter (SQM). We found that if we include Coulomb term in scalar density form, SQM equation of state (EOS) at high densities is stiffer but if we include Coulomb term in vector density form is softer than that of standard CIDDM model. We also investigate systematically the role of each term of the extended CIDDM model. Compared with what was reported in Ref.~\cite {ref:isospin}, we found the stiffness of SQM EOS is controlled by the interplay among the the oscillator harmonic, isospin asymmetry and Coulomb contributions depending on the parameter's range of these terms. We have found that the absolute stable condition of SQM and the mass of 2 $M_\odot$ pulsars can constrain the parameter of oscillator harmonic $\kappa_1$ $\approx 0.53$ in the case Coulomb term excluded. If the Coulomb term is included, for the models with their parameters are consistent with SQM absolute stability condition, the $2.0~M_{\odot}$ constraint more prefer the maximum mass prediction of model with scalar Coulomb term than that of model with vector Coulomb term. On contrary, the high densities EOS predicted by model with vector Coulomb is more compatible with recent pQCD result \cite{ref:pressure} than that predicted by model with scalar Coulomb. Furthermore, we also observed the quark composition in a very high density region depends quite sensitively on the kind of Coulomb term used.