The stability of color-flavor-locked quark matter and massive CFL quark stars

TL;DR

This paper investigates the stability of color-flavor-locked quark matter in compact stars, demonstrating conditions under which CFL quark matter could be the true ground state and explaining certain astrophysical observations.

Contribution

It provides a systematic analysis of the parameters influencing CFL quark matter stability, supporting the existence of self-bound quark stars consistent with recent astrophysical data.

Findings

Identifies a parameter space where CFL phase is the true ground state.

Supports the existence of self-bound quark stars compatible with NICER and LIGO/Virgo data.

Offers explanations for the mass-gap object in GW190814 and ultra-low-mass compact objects.

Abstract

Owing to the emergence of attractive interactions between quarks, color superconductivity is expected to occur, with the color-flavor-locked (CFL) phase favored at high densities. This work investigates the absolute stability of beta-equilibrated CFL quark matter in bulk within the modified Nambu-Jona-Lasinio model, under color and electric charge neutrality conditions relevant to compact stars. Motivated by the possible existence of an ultra-low-mass central compact object in the supernova remnant HESS J1731-347 and the "mass-gap" secondary component in the GW190814 event, we systematically explore how vector repulsion, attractive diquark pairing, and nonperturbative vacuum effects influence the stiffness of CFL quark matter and its stability. Our findings suggest the existence of a physically viable region of parameter space in which the CFL phase is the true ground state of strongly interacting matter, thereby theoretically supporting the scenario of self-bound quark stars. This configuration is not only consistent with current astrophysical constraints from NICER and LIGO/Virgo observations, but also provides a possible explanation for both the $~2.6\ M_{\odot}$ secondary component in GW190814 and the ultra-low-mass compact object with $M = 0.77^{+0.20}_{-0.17}\ M_{\odot}$in HESS J1731-347.