Cold uniform matter and neutron stars in the quark–meson-coupling model

Abstract

A new density dependent effective baryon-baryon interaction has been recently derived from the quark-meson-coupling (QMC) model, offering impressive results in application to finite nuclei and dense baryon matter. This self-consistent, relativistic quark-level approach is used to construct the Equation of State (EoS) and to calculate key properties of high density matter and cold, slowly rotating neutron stars. The results include predictions for the maximum mass of neutron star models, together with the corresponding radius and central density, as well the properties of neutron stars with mass of order 1.4 M ⊙ . The cooling mechanism allowed by the QMC EoS is explored and the parameters relevant to slow rotation, namely the moment of inertia and the period of rotation investigated. The results of the calculation, which are found to be in good agreement with available observational data, are compared with the predictions of more traditional EoS, based on the A18+δv+UIX * and modified Reid soft core potentials, the Skyrme SkM * interaction and a relativistic mean field (RMF) models for a hybrid stars including quark matter. The QMC EoS provides cold neutron star models with maximum mass 1.9-2.1 M ⊙ , with central density less than 6 times nuclear saturation density (n 0 = 0.16 fm −3 ) and offers Preprint submitted to Elsevier Science 17 February 2017a consistent description of the stellar mass up to this density limit. In contrast with other models, QMC predicts no hyperon contribution at densities lower than 3n 0 , for matter in β-equilibrium. At higher densities, Ξ −,0 and Λ hyperons are present. The absence of lighter Σ ±,0 hyperons is understood as a consequence of antisymmetrisation, together with the implementation of the color hyperfine interaction in the response of the quark bag to the nuclear scalar field.

Tables of hyperonic matter equation of state for core-collapse supernovae

“…This behavior is different from the previous works that adopt attractive potentials [1,2,3,4,5], and pointed out in Refs. [2,3,4,38]. When we allow the appearance of pions, condensed pions (π − ) appear prior to hyperons.…”

Phase transition from quark-meson coupling hyperonic matter to deconfined quark matter

“…5, where we note that the species fraction is enhanced and the species fractions are suppressed with increasing density. From the investigations by Rikovska-Stone et al [16], we expect that the would disappear entirely if we were to include Fock terms.…”

“…For this purpose, we consider hadronic matter modeled by the quark-meson coupling (QMC) model [14,15], which was recently improved through the self-consistent inclusion of color hyperfine interactions [16]. While this improvement had no significant effect on the binding of nucleons, it led to impressive results for finite hypernuclei [17].…”

Medium modifications of baryon properties in nuclear matter and hypernuclei

“…[16], where Σ hypernuclei could be bound by an amount similar to Λ hypernuclei. Recently, the QMC model has been extended to include the quark-quark hyperfine interactions due to gluon and pion exchanges [52][53][54][55]. It was found that the hyperfine interaction due to the gluon exchange plays an important role in the in-medium baryon spectra, while the pion-cloud effect is relatively small [55].…”

“…It was found that the hyperfine interaction due to the gluon exchange plays an important role in the in-medium baryon spectra, while the pion-cloud effect is relatively small [55]. Furthermore, the hyperfine interaction can make the equation of state hard and thus enhance the mass of a neutron star [52,56]. The medium effect on the hyperfine interaction increases the splitting between the Λ and Σ masses as the density rises, and Σ hypernuclei are found to be unbound in Ref.…”