Recovering the conformal limit of color superconducting quark matter within a confining density functional approach

TL;DR

This paper extends a confining density functional model to include density-dependent couplings, recovering the conformal limit at high densities, and demonstrates its consistency with neutron star observations and the presence of quark matter at low masses.

Contribution

It introduces a generalized confining relativistic density-functional approach with density-dependent couplings, aligning the quark matter EoS with the conformal limit and astrophysical constraints.

Findings

The model achieves a conformal limit at high densities.

The EoS remains sufficiently stiff for neutron star interiors.

Quark matter onset is plausible below 1.0 solar masses.

Abstract

We generalize a recently proposed confining relativistic density-functional approach to the case of density dependent vector and diquark couplings. The particular behavior of these couplings is motivated by the non-perturbative gluon exchange in dense quark matter and provides the conformal limit at asymptotically high densities. We demonstrate that this feature of the quark matter EoS is consistent with a significant stiffness in the density range typical for the interiors of neutron stars. In order to model these astrophysical objects we construct a family of hybrid quark-hadron EoSs of cold stellar matter. We also confront our approach with the observational constraints on the mass-radius relation of neutron stars and their tidal deformabilities and argue in favor of a quark matter onset at masses below $1.0~{\rm M}_\odot$