arXiv subjects

Hiroshi Uechi

Publications and source records attributed to Hiroshi Uechi.

3 recordsLinked to original sources

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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arXiv2006

Properties of Nuclear and Neutron Matter and Thermodynamic Consistency in a Nonlinear Mean-field Approximation

Properties of nuclear and neutron matter are discussed in a nonlinear $σ$-$ω$-$ρ$ mean-field approximation with self-interactions and mixing-interactions of mesons and baryons. The nonlinear interactions are renormalized by employing the theory of conserving approximations, which results in a thermodynamically consistent approximation that maintains Hugenholtz-Van Hove theorem and Landau's requirement of quasiparticles. The approximation is equivalent to the Hartree approximation with {\it effective masses} and {\it effective coupling constants} of baryons and mesons. The effective masses and coupling constants are naturally required by self-consistency of the theory of conserving approximations. The approximation is applied to nuclear and neutron matter, which suggests that the lower bound of nuclear compressibility $K \sim 180$ MeV (with the symmetry energy $a_4 = 35.0$ MeV) be required to be consistent with properties of nuclear matter and the maximum masses of observed hadronic neutron stars ($M_{max} \ge 2.00$ $M_{\odot}$). The values of the compressibility, symmetry energy together with effective masses and coupling constants of baryons and mesons will be important constraints to examine models of nuclear and neutron matter. The accumulating data and accurate measurements of observables in high density and energy region will supply significant information in order to testify theoretical consistency of nuclear models.

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