Equations of State of different phases of dense quark matter

Abstract

Compact stars with significant high densities in their interiors can give rise to quark deconfined phases that can open a window for the study of strongly interacting dense nuclear matter. Recent observations on the mass of two pulsars, PSR J1614-2230 and PSR J0348+0432, have posed a great restriction on their composition, since their equations of state must be hard enough to support masses of about at least two solar masses. The onset of quarks tends to soften the equation of state, but due to their strong interactions, different phases can be realized with new parameters that affect the corresponding equations of state and ultimately the mass-radius relationships. In this paper I will review how the equation of state of dense quark matter is affected by the physical characteristics of the phases that can take place at different baryonic densities with and without the presence of a magnetic field, as well as their connection with the corresponding mass-radius relationship, which can be derived by using different models.

Properties of strange quark matter and strange quark stars

“…Therefore, several QCD enthused effective models are used widely to study the nonperturbative strongly interacting matter. Some of the examples are: MIT bag model [36,37], Dyson-Schwinger equation approach [38][39][40][41], quark meson coupling (QMC) model [42], quark mass density dependent (QMDD) model [43][44][45][46][47], Nambu-Jona-Lasinio (NJL) model [37,48], confined density dependent quark mass (CDDM) model [8,49,50], chiral SU(3) quark mean field (CQMF) model [51,52], Polyakov quark meson coupling (PQMC) model [53,54] and Polyakov extended NJL (PNJL) model [55][56][57]. Many authors have studied the properties of pure SQM in β-equilibrium [58-61], proto-strange quark stars (PSQS) [62][63][64][65][66][67], as well as hybrid star with SQM in the core [68,69] (also, see references therein).…”

“…In [36], the EoS of quark matter with color flavor locked (CFL) phase was studied using MIT bag and NJL model to understand the conditions which may lead to the mass of about 1.97M . Although in the MIT model, the stiff EoS can be observed if a larger value of gap parameter is used, in the NJL-CFL model, including gluonic effects, the stiffening of the EoS is very sensitive to the vector-vector coupling strength G V (large value of G V is required for stiff EoS).…”

“…In the present work, we will investigate the properties of stars during above described stages of evolution. The questions, for example, CFL phase in SQS [36], the impact of finite magnetic field [64], and the inclusion of the hadronic degrees of freedom to investigate hybrid stars within the present PCQMF model will be addressed in the future work.…”

Modelling a $2.5 \, M_{\odot}$ Compact Star with Quark Matter

“…A variety of approaches for a model description of strange matter and, in general, self-bound matter were attempted since Witten's work. The MIT bag model with a quasi-linear equation of state (EoS) has been widely used, but Nambu-Jona-Lasinio 32,33 , density-dependent quark masses 34 and a few other variants were also considered. More recently it has been established that paired quark states should be relevant in the dense deconfined phase.…”

“…Motivated by the introduction of strange matter, Ferrer 33 discussed a model based on the Nambu-Jona-Lasinio approach, in which vector interactions and gluon components were introduced. This work shows that, even without a gluonic component, NJL EoS can be used to reach high maximum masses in the corresponding sequences provided the ratio of the (repulsive) vector channel to the quark-antiquark G V /G S is high enough.…”