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中子星的核子半径效应

       近日,厦门大学天文学系李昂教授及其研究生朱镇宇最近在美国物理学会Physical Review C上发表了一篇题为“Effects of the nucleon radius on neutron stars in a quark mean field model”的文章,研究了中子星的核子半径效应,并基于更加合理自洽的方法否定了之前相关工作的结论。

       中子星(Neutron star)是一种宇宙中极为致密的天体,是大质量恒星演化到晚期的产物。在引力产生的极高压强下,普通物质的原子分子结构只能解体,转而完全由中子(Neutron)和少量质子(Proton)、电子组成的高度致密物质来抵抗自身的引力。因此,质子、中子这类微观的核子(Nucleon)性质或许会对中子星这个宏观星体产生明显的影响。事实上,之前已经有工作指出,核子半径的不确定性对中子星的半径产生了显著的影响。

       在该工作中,从夸克层次出发的物理模型——夸克平均场模型(Quark mean field model)被采用。通过固定核物质的饱和性质,该工作研究了不同核子半径(0.80, 0.87, 1.00 fm)对中子星半径(R)的影响。最终的结果显示,核子半径对中子星半径的影响非常小,而相比较下核物质的对称能(J)和对称能斜率(L)的影响反而更加重要。对称能是系统中由于质子和中子数不相同产生的附加能量。之前工作关于“核子半径显著影响中子星半径”的结论显然是由不同对称能和对称能斜率导致的。

英文摘要:We study the effects of free space nucleon radius on nuclear matter and neutron stars within the framework of the quark mean field model. The nucleon radius is treated self-consistently with this model, where quark confinement is adjusted to fit different values of nucleon radius. Corrections due to center-of-mass motion, quark-pion coupling, and one gluon exchange are included to obtain the nucleon mass in vacuum. The meson coupling constants that describe the behavior of the many-body nucleonic system are constructed by reproducing the empirical saturation properties of nuclear matter, including the recent determinations of symmetry energy parameters. Our results show that the nucleon radius in free space has negligible effects on the nuclear matter equation of state and neutron star mass-radius relations, which is different from the conclusion drawn in previous studies. We further explore that the sensitivity of star radius on the nucleon radius found in earlier publications is actually from the symmetry energy and its slope.

详见文献:Zhen-Yu Zhu and Ang Li, Phys. Rev. C 97, 035805 (2018)

李昂教授主页:http://astro.xmu.edu.cn/astro/liang

如对核天体物理研究方向感兴趣,请liang.AT.xmu.edu.cn咨询。

 



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