# Finite temperature effects on spin polarization of neutron matter in a strong magnetic field - Nuclear Theory

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Abstract: Spin polarization of neutron matter at finite temperatures and strongmagnetic fields up to $10^{18}$ G is studied in the model with the Skyrmeeffective interaction. It is shown that, together with the thermodynamicallystable branch of solutions for the spin polarization parameter corresponding tothe case when the majority of neutron spins are oriented opposite to thedirection of the magnetic field negative spin polarization, theself-consistent equations, beginning from some threshold density, have also twoother branches of solutions corresponding to positive spin polarization. Theinfluence of finite temperatures on spin polarization remains moderate in theSkyrme model up to temperatures relevant for protoneutron stars, and, inparticular, the scenario with the metastable state characterized by positivespin polarization, considered at zero temperature in Phys. Rev. C {\bf 80},065801 2009, is preserved at finite temperatures as well. It is shown thatabove certain density the entropy for various branches of spin polarization inneutron matter with the Skyrme interaction in a strong magnetic fielddemonstrates the unusual behavior being larger than that of the nonpolarizedstate. By providing the corresponding low-temperature analysis, it is clarifiedthat this unexpected behavior should be addressed to the dependence of theentropy of a spin polarized state on the effective masses of neutrons with spinup and spin down, and to a certain constraint on them which is violated in therespective density range.

Author: A.A. Isayev, J. Yang

Source: https://arxiv.org/