Nonperturbative quark matter equations of state with vector interactions

Abstract

Nonperturbative equations of state (EoSs) for two and three quark flavors are constructed with the functional renormalization group (FRG) within a quark-meson model truncation augmented by vector mesons for low temperature and high density. Based on previous FRG studies without repulsive vector meson interactions the influence of isoscalar vector ω- and ϕ-mesons on the dynamical fluctuations of quarks and (pseudo)scalar mesons is investigated. The grand potential as well as vector meson condensates are evaluated as a function of quark chemical potential and the quark matter EoS in β-equilibrium is applied to neutron star (NS) physics. The tidal deformability and mass-radius relations for hybrid stars from combined hadronic and quark matter EoSs are compared for different vector couplings. We observe a significant impact of the vector mesons on the quark matter EoS such that the resulting EoS is sufficiently stiff to support two-solar-mass neutron stars.

Universal relations for rapidly rotating cold and hot hybrid star

“…Furthermore, models which describe on the same footing the quark and hadronic phases for astrophysics applications are lacking, therefore a first-order phase transition is often constructed between models of hadronic and quark matter with different underlying theories. A first-order phase transition will affect not only the static properties of compact stars, such as tidal deformabilities measured in gravitational wave events (Paschalidis et al 2018;Montaña et al 2019;Sieniawska et al 2019;Essick et al 2020;Otto et al 2020;Li et al 2020;Jie Li et al 2021;Ferreira et al 2021;Ayriyan et al 2021b), but also their dynamics (Fischer et al 2018;Zha et al 2020;Most et al 2019;Bauswein et al 2019;Prakash et al 2021). Specifically, Fischer et al (2018) and Zha et al (2020) proposed that neutrino and gravitational-wave signals from supernova explosions may contain observable signatures of a phase transition.…”

EoS for hot neutron stars

“…PSR J1810+1744 (M = 2.13 ± 0.04M ⊙ with 68% confidence level [24]), but in contrast to the above mentioned mass determinations these depend on the companion heating model -have triggered a large number of studies on the appearance of non-nucleonic degrees of freedom at high densities. In particular, hyperons [25,26,27,28,29,30,31,32,33,34], the lowest spin-3/2 baryonic multiplet [35,36,37,38,34,39,40], meson condensates [41,42] and a potential phase transition to quark-matter [43,44,45,46,47,48,49,50] have been considered. All these works indicate that in contrast to the first expectations, maximum NS masses of ≈ 2M ⊙ do not exclude these non-nucleonic degrees of freedom to appear in the most massive neutron stars.…”

Tidal Deformability of Quark Stars with Repulsive Interactions

“…Since then it was shown in several works that a self-bound star, composed entirely of quark matter, could explain a massive neutron star. In order to obtain a stiff enough quark matter equation of state, several groups introduced repulsive interactions among the quarks, mediated by the exchange of vector particles [10,[14][15][16][17][18][19], which can be "effective massive gluons" or "effective vector mesons". Interestingly, most of these developments make use of a mean field approximation for the vector field and arrive at a similar result, which is a quadratic term in the baryon density present both in the pressure and energy density.…”