Strongly Interacting Quark Matter in Massive Quark Stars

This paper investigates the properties of strongly coupled matter at high densities in a quark star (QS). The QS is built from the density-dependent quark mass model (DDQM), modified to obtain higher maximum gravitational mass (Mₘₐₓ) of the QS using the data from observed pulsars: XMMU J173203.3-344518, PSR J0030+0451, PSR J0740+6620, and PSR J0952-0607 as constraints in Bayesian inference. We observed that the quark matter (QM) that composes QSs with Mₘₐₓ > 2M_ violates the conformality criteria determined through conformal field theory. This behavior is interpreted as a consequence of the increase in quark population with ρB and the concomitant formation of colored quark and gluon condensates, which are influenced by the pressure build-up in the stellar core as ρB increases. This is reflected in the enhanced DDQM model employed, which introduces an additional term relevant at high densities. On the other hand, for Mₘₐₓ < 2M_ we observed the desired behavior of the QM as predicted by quantum chromodynamics (QCD) at higher densities, where the interaction decreases with increasing ρB and eventually the quarks become deconfined due to the depletion of the DDQM through an additional attractive contribution in this case.