Chiral Restoration of Nucleons in Neutron Star Matter: Studies Based on a Parity Doublet Model
Chiral Restoration of Nucleons in Neutron Star Matter: Studies Based on a Parity Doublet Model
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DOI：
10.3390/sym15030745
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发表时间：
2023-02
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影响因子：
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通讯作者：
Takuya Minamikawa;Bikai Gao;T. Kojo;M. Harada
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文献类型：
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作者：
Takuya Minamikawa;Bikai Gao;T. Kojo;M. Harada
本文综述了核子质量的手性变分和不变分量以及它们的存在对极端条件下，特别是中子星物质中的手征恢复的影响。我们考虑了一个手征对称性的线性实现模型，该模型具有核子宇称二重态结构，允许正负宇称核子的手征不变质量M0。核物质是通过U(1)A反常耦合到标量场σ、矢量场(ω，ρ)和具有奇异性的介子的宇称双核子模型构造的。在具有大M0的模型中，核子质量对介质不敏感，并且不需要核子与标量场σ和矢量场ω的强耦合就可以再现核饱和性质。我们将得到的核物态方程与核约束和中子星观测对峙，并描绘了手征不变质量和有效相互作用。为了进一步研究饱和密度以外的核物态方程，我们补充了夸克模型，从高密度侧设置边界条件。夸克模型受双太阳质量条件的约束，这种约束通过因果关系和热力学稳定性条件转移到原子核模型中。我们还通过构造一个生成泛函来插值核物质和夸克物质与外场，计算了统一物质中从核物质到夸克物质的各种凝聚体和物质组成。讨论了两种类型的手性恢复：一种是由于核子的正标量电荷，另一种是由狄拉克海的演化引发的。我们发现U(1)A反常使状态方程从低密度软化到高密度。
We review the chiral variant and invariant components of nucleon masses and the consequence of their existence on the chiral restoration in extreme conditions, particularly in neutron star matter. We consider a model of linear realization of chiral symmetry with the nucleon parity doublet structure that permits the chiral invariant mass, m0, for positive and negative parity nucleons. The nuclear matter is constructed with the parity doublet nucleon model coupled to scalar fields σ, vector fields (ω,ρ), and mesons with strangeness through the U(1)A anomaly. In models with a large m0, the nucleon mass is insensitive to the medium, and the nuclear saturation properties can be reproduced without demanding strong couplings of the nucleons to the scalar fields σ and vector fields ω. We confront the resulting nuclear equations of state with nuclear constraints and neutron star observations and delineate the chiral invariant mass and effective interactions. To further examine the nuclear equations of state beyond the saturation density, we supplement quark models to set the boundary conditions from the high-density side. The quark models are constrained by the two-solar-mass conditions, and such constraints are transferred to nuclear models through the causality and thermodynamic stability conditions. We also calculate various condensates and the matter composition from nuclear to quark matter in a unified matter by constructing a generating functional that interpolates the nuclear and quark matter with external fields. Two types of chiral restoration are discussed: one due to the positive scalar charges of nucleons and the other triggered by the evolution of the Dirac sea. We found that the U(1)A anomaly softens equations of state from low to high density.