Equation of state of spin-polarized nuclear matter in the relativistic Hartree-Fock method

TL;DR

This paper investigates the equation of state of spin-polarized nuclear matter using a relativistic Hartree-Fock approach with a point-coupling model, revealing correlations between spin and isospin polarization parameters.

Contribution

It introduces a simplified relativistic Hartree-Fock method with point-coupling to analyze spin-polarized nuclear matter and explores the relationships between spin and isospin polarization parameters.

Findings

Negative correlation between $L$ and $L_s$ in isoscalar polarization.

Spin slope parameter $L_s$ is nearly independent of $L$ in isovector polarization.

Relativistic point coupling model explains the observed polarization correlations.

Abstract

We calculate the equation of state (EOS) of spin-polarized nuclear matter in the relativistic Hartree-Fock method. To this end, we employ the relativistic point-coupling model, with which the Fock terms are considerably simplified, reducing them to the same form as the Hartree terms. In analogy to the slope parameter $L$ of the isospin-symmetry energy for spin-unpolarized matter, we evaluate the spin slope parameter $L_s$ of the corresponding spin-symmetry energy for spin-polarized matter. We find that the slope parameter $L$ and the spin slope parameter $L_s$ have a negative correlation in the case of isoscalar polarization, where neutrons and protons are spin-polarized in the same direction. On the other hand, the spin slope parameter is nearly independent of the slope parameter in the case of isovector polarization, where neutrons are spin-polarized along the opposite direction to protons. We show that these correlations are a natural consequence of the relativistic point coupling model which we employ.