Hardon-Quark Hybrid Stars Constructed by the Nonlinear σ-ω-ρ Mean-Field Model and MIT-Bag Model

Abstract

Density-dependent relations among saturation properties of symmetric nuclear matter and hyperonic matter, properties of hadron-(strange) quark hybrid stars are discussed by applying the conserving nonlinear σ-ω-ρ hadronic mean-field theory. Nonlinear interactions that will be renormalized as effective coupling constants, effective masses and sources of equations of motion are constructed self-consistently by maintaining thermodynamic consistency to the mean-field approximation. The coupling constants expected from the hadronic mean-field model and SU(6) quark model for the vector coupling constants are compared; the coupling constants exhibit different density-dependent results for effective masses and binding energies of hyperons, properties of hadron and hadron-quark stars. The nonlinear σ-ω-ρ hadronic mean-field approximation with or without vacuum fluctuation corrections and strange quark matter defined by MIT-bag model are employed to examine properties of hadron-(strange) quark hybrid stars. We have found that hadron-(strange) quark hybrid stars become more stable in high density compared to pure hadronic and strange quark stars. 1 matter [23], M max (n, p, e) ∼ 2.50 M ⊙ (the solar mass: M ⊙ ∼ 1.989 × 10 30 kg), are found reasonable and admissible in the nonlinear σ-ω-ρ Hartree approximation [18,19].The maximum masses of neutron stars are expected to be below 2.5 M ⊙ [24], or 2.1 ± 0.2M ⊙ [25], which depends on the hadronic equation of state (EOS) for isospin asymmetric, hyperonic matter in the density range, 2ρ 0 ρ B 5ρ 0 . The hadronic liquid-gas phase transition at the surface of neutron stars and determination of the radius of smeared, gas-phase surface are not directly relevant to properties of hadronic matter and maximum masses of neutron stars. The nonlinear interactions exhibit significant density-dependent effects on incompressibility, K, and symmetry energy, a 4 , in high densities; these Fermi liquid properties monotonically increase about saturation density, but they are piecewise continuously softened at an hyperon onset density. These phenomena of piecewise continuous change of Fermi-liquid properties will be important for the analysis of Landau parameters, heavy-ion collision, high energy and high density experiments. At a hyperon onset density from (n, p, e) to (n, p, H, e), the EOS suddenly becomes softer. This is because the nucleon Fermi energy, E N (k F ) in the phase (n, p, e), will be redistributed to the hyperon Fermi energy, E H (k F ) in the phase (n, p, H, e); consequently, the Fermi energies become relatively small in the phase (n, p, H, e) compared with those of (n, p, e). The redistribution and slow increase of Fermi energies appear whenever hyperons are generated, resulting in a softer equation of state and discontinuous changes of K and a 4 . This is numerically checked as discrete changes of physical quantities, such as effective masses of hadrons, incompressibility, symmetry energy and energy density [18,19].Since the hyperon-onset will confine Fermi-energies of baryons as e...

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“…It is observed that ignoring critical aspects of the quantum particle physics in the framework of GR several authors [59,60,[99][100][101][102][103][104][105][106] have successfully introduced this simplified form of the MIT Bag EOS to study stellar systems made of SQM.…”

Study on Anisotropic Strange Stars in <em>f</em>(T,<em>T</em>) Gravity

“…It is observed that ignoring critical aspects of the quantum particle physics in the framework of GR several authors [56,57,[80][81][82][83][84][85][86][87] successfully have introduced this simplified form of the MIT Bag EOS to study stellar systems made of SQM.…”