Unified Interacting Quark Matter and its Astrophysical Implications

Abstract

We investigate interacting quark matter (IQM), including the perturbative QCD correction and color superconductivity, for both up-down quark matter (udQM) and strange quark matter (SQM). We first derive an equation of state (EOS) unifying all cases by a simple reparametrization and rescaling, through which we manage to maximally reduce the number of degrees of freedom. We find, in contrast to the conventional EOS p = 1/3(ρ − 4B eff ) for non-interacting quark matter, that taking the extreme strongly interacting limit on the unified IQM EOS gives p = ρ−2B eff , where B eff is the effective bag constant. We employ the unified EOS to explore the properties of pure interacting quark stars (IQSs) composed of IQM. We describe how recent astrophysical observations, such as the pulsar-mass measurements, the NICER analysis, and the binary merger gravitational-wave events GW170817, GW190425, and GW190814, further constrain the parameter space. An upper bound for the maximum allowed mass of IQSs is found to be MTOV 3.23 M . Our analysis indicates a new possibility that the currently observed compact stars, including the recently reported GW190814's secondary component (M = 2.59 +0.08 −0.09 M ), can be quark stars composed of interacting up-down quark matter.

Stellar Structure and Stability of Charged Interacting Quark Stars and Their Scaling Behaviour

“…Previously we established a general parametrization of the quark matter EOS that included pQCD corrections and color superconductivity [14]. Somewhat remarkably, we found that the EOS could be rescaled into a dimensionless form depending only on a single parameter characterizing the relative size of strong interaction effects.…”

“…Taking into account such interactions generally yields predictions of larger masses and radii for quark stars, due to their stiff equation of state (EOS) compared to those of neutron stars and 'normal' quark stars in which such interactions are neglected [12] . Such interacting quark stars have been shown to have regions of parameter space that match current astrophysical constraints [13,14] and are able to produce gravitational-wave echoes [15].…”

“…The unified EOS of interacting quark matter relating the radial pressure P to the mass density ρ is [14]:…”

Non-Minimally Coupled Einstein-Yang-Mills Field Equations and Wu-Yang Monopoles in Bertotti-Robinson Spacetimes

“…A very special class of exact static, spherically symmetric solutions which are determined by the Wu-Yang magnetic pole potentials in a non-conformally flat Bertotti-Robinson spacetime are found. Such solutions may be related physically to regular black holes with colour [31,32,33]. However, they are in no way generic.…”