强磁场中中子物质自旋极化的有限温度效应
Finite temperature effects on spin polarization of neutron matter in a strong magnetic field
摘要：
在考虑Skyrme有效相互作用的模型中，研究了中子物质在有限温度和高达$10^{18}$ G的强磁场下的自旋极化。结果表明，连同对应于大多数中子自旋与磁场方向相反（负自旋极化）的情况下的自旋极化参数的解的稳定分支，自洽方程，从某个阈值密度开始，也有两个对应于正自旋极化的解的其他分支。有限温度对自旋极化的影响在Skyrme模型中保持适度，直到与质子中子星相关的温度，并且特别地，在Phys.Rev.C { \bf 80}，065801（2009）中在零温度下考虑的具有以正自旋极化为特征的亚稳态的情况也在有限温度下被保留。结果表明，在一定密度以上，强磁场中存在Skyrme相互作用的中子物质中自旋极化各分支的熵表现出比非极化态大的反常行为。通过提供相应的低温分析，它是澄清，这种意想不到的行为应解决的自旋极化态的熵的有效质量的中子与自旋向上和自旋向下的依赖关系，并对他们的一定的约束，这是违反在各自的密度范围。
英文摘要：
Spin polarization of neutron matter at finite temperatures and strong magnetic fields up to $10^{18}$ G is studied in the model with the Skyrme effective interaction. It is shown that, together with the thermodynamically stable branch of solutions for the spin polarization parameter corresponding to the case when the majority of neutron spins are oriented opposite to the direction of the magnetic field (negative spin polarization), the self-consistent equations, beginning from some threshold density, have also two other branches of solutions corresponding to positive spin polarization. The influence of finite temperatures on spin polarization remains moderate in the Skyrme model up to temperatures relevant for protoneutron stars, and, in particular, the scenario with the metastable state characterized by positive spin polarization, considered at zero temperature in Phys. Rev. C {\bf 80}, 065801 (2009), is preserved at finite temperatures as well. It is shown that above certain density the entropy for various branches of spin polarization in neutron matter with the Skyrme interaction in a strong magnetic field demonstrates the unusual behavior being larger than that of the nonpolarized state. By providing the corresponding low-temperature analysis, it is clarified that this unexpected behavior should be addressed to the dependence of the entropy of a spin polarized state on the effective masses of neutrons with spin up and spin down, and to a certain constraint on them which is violated in the respective density range.
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