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arXiv 1111.6942astro-ph.SR
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中子星核中的超子和双太阳质量脉冲星

Hyperons in neutron-star cores and two-solar-mass pulsar

I. Bednarek, P. Haensel, J. L. Zdunik, M. Bejger, R. Mańka

摘要:

最近对PSR J1614 - 2230质量的测量排除了大多数现有的致密物质状态方程(EOS)模型,这些模型具有由于超电离或向夸克物质或玻色子凝聚体的相变而导致的高密度软化。我们寻找一个解决方案的一个明显的矛盾之间的后果源于最新的超核数据,表明超子的外观在3个核密度和存在的两个太阳质量的中子星。考虑一个包含重子八重态和介子场耦合的非线性相对论平均场模型。有效拉格朗日量包括介子场中的四次项。模型的参数值是通过拟合饱和点处核物质的半经验参数、核物质中超子的势阱以及双λ超核中的Lambda-Lambda吸引力强度得到的。我们提出了一个非线性RMF模型,它与最新的半经验核和超核数据相一致,并允许中子星的超子核心和M大于2太阳质量。该模型涉及到隐奇异标量和矢量介子,耦合到超子,四次项涉及矢量介子场。我们的状态方程涉及超子比相应的核子状态方程(人工抑制超子)以上五个核密度。所需的硬化是由包含隐奇异矢量介子的四次项产生的。

英文摘要:

Recent measurement of mass of PSR J1614-2230 rules out most of existing models of equation of state (EOS) of dense matter with high-density softening due to hyperonization or a phase transition to quark matter or a boson condensate. We look for a solution of an apparent contradiction between the consequences stemming from up-to-date hypernuclear data, indicating appearance of hyperons at 3 nuclear densities and existence of a two-solar-mass neutron star. We consider a non-linear relativistic mean field (RMF) model involving baryon octet coupled to meson fields. An effective lagrangian includes quartic terms in the meson fields. The values of the parameters of the model are obtained by fitting semi-empirical parameters of nuclear matter at the saturation point, as well as potential wells for hyperons in nuclear matter and the strength of the Lambda-Lambda attraction in double-Lambda hypernuclei. We propose a non-linear RMF model which is consistent with up-to-date semiempirical nuclear and hypernuclear data and allows for neutron stars with hyperon cores and M larger than 2 solar masses. The model involves hidden-strangenes scalar and vector mesons, coupled to hyperons only, and quartic terms involving vector meson fields. Our EOS involving hyperons is stiffer than the corresponding nucleonic EOS (with hyperons artificially suppressed) above five nuclear densities. Required stiffening is generated by the quartic terms involving hidden-strangeness vector meson.

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