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大质量中子星内部强子-夸克混杂相的研究

Study of Hadron-quark Mixed Phases in Massive Neutron Stars

  • 摘要: 大质量中子星的核心密度可达5~10倍饱和密度,很有可能发生强子-夸克退禁闭相变。在本工作中,研究了强子-夸克混杂相的结构性质及其对中子星性质的影响,并进一步讨论了中子星内部是否存在纯夸克相核心。在此工作中,采用Wigner-Seitz元胞近似描述强子-夸克混杂相,采用自洽考虑了有限尺度效应的能量最小化(EM)方法判断系统的稳定态。通过允许强子相和夸克相具有不同的电子密度,但总电子化学势保持相等,在Wigner-Seitz元胞内实现局部β平衡。本文采用BigApple和NL3两组参数描述强子物质,而夸克物质由加入了矢量相互作用的MIT袋模型描述。研究发现,强子相的对称能斜率越大,相变发生越早,且夸克之间的矢量相互作用可以显著硬化高密度下的状态方程(EOS),有助于增大中子星的最大质量。其他参数,如口袋常数B,也会影响中子星内部的退禁闭相变。结果表明,强子-夸克混杂相可能出现在大质量中子星核心中,并满足当前天文观测约束。

     

    Abstract: The cores of massive neutron stars can reach densities 5~10 times that of nuclear saturation density, where hadron deconfinement phase transition is highly plausible. In this work, we investigate the structural properties of the hadron-quark mixed phases and their impact on the characteristics of neutron stars. Furthermore, we delve into the possibility of the existence of a pure quark phase core within neutron stars. We investigate the properties of the hadron-quarkpastaphases and their influences on the equation of state (EOS) for neutron stars. In this work, we extend the energy minimization (EM) method to describe the hadron-quarkpastaphase, where the surface and Coulomb contributions are included in the minimization procedure. By allowing different electron densities in the hadronic and quark matter phases, the total electron chemical potential with the electric potential remains constant, and local β equilibrium is achieved inside the Wigner-Seitz cell. We employ the relativistic mean-field model to describe the hadronic matter, while the quark matter is described by the MIT bag model with vector interactions. It is found that the vector interactions among quarks can significantly stiffen the EOS at high densities and help enhance the maximum mass of neutron stars. Other parameters like the bag constant can also affect the deconfinement phase transition in neutron stars. Our results show that hadron-quarkpastaphases may appear in the core of massive neutron stars that can be compatible with current observational constraints.

     

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