Schun T. Uechi | Searcharxiv

arXiv2010

Chiral-particle Approach to Hadrons in an Extended Chiral ($σ,π,ω$) Mean-Field Model

The chiral nonlinear ($σ,π,ω$) mean-field model is an extension of the conserving nonlinear (nonchiral) $σ$-$ω$ hadronic mean-field model which is thermodynamically consistent, relativistic and Lorentz-covariant mean-field theory of hadrons. In the extended chiral ($σ,π,ω$) mean-field model, all the masses of hadrons are produced by chiral symmetry breaking mechanism, which is different from other conventional chiral partner models. By comparing both nonchiral and chiral mean-field approximations, the effects of chiral symmetry breaking to the mass of $σ$-meson, coefficients of nonlinear interactions, coupling ratios of hyperons to nucleons and Fermi-liquid properties are investigated in nuclear matter, hyperonic matter, and neutron stars.

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arXiv2010

Hardon-quark hybrid stars constructed by the nonlinear $σ$-$ω$-$ρ$ mean-field model and MIT-bag model

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.

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