Early deconfinement of asymptotically conformal color-superconducting quark matter in neutron stars

TL;DR

This paper develops a relativistic density functional model for color superconducting quark matter in neutron stars, incorporating confinement and medium-dependent couplings, and suggests early deconfinement at low neutron star masses.

Contribution

It introduces a novel approach combining confinement mimicry with medium-dependent couplings to model quark matter in neutron stars, aligning with observational constraints.

Findings

Deconfinement likely occurs in neutron stars below 1.0 solar masses.

Model reproduces QCD vacuum phenomenology and high-density conformal behavior.

Provides constraints on the onset of quark matter in neutron stars.

Abstract

We present a relativistic density functional approach to color superconducting quark matter that mimics quark confinement by a fast growth of the quasiparticle selfenergy in the confining region. The approach is shown to be equivalent to a chiral model of quark matter with medium dependent couplings. While the (pseudo)scalar sector of the model is fitted to the vacuum phenomenology of quantum chromodynamics, the strength of interaction in the vector and diquark channels is varied in order to provide the best agreement with the observational constraints on the mass-radius relation and tidal deformability of neutron stars modelled with our approach. In order to recover the conformal behavior of quark matter at asymptotically high densities we introduce a medium dependence of the vector and diquark couplings motivated by the nonperturbative gluon exchange. Our analysis signals that the onset of deconfinement to color superconducting quark matter is likely to occur in neutron stars with masses below 1.0 $M_\odot$.