Spinodal instabilities of spin polarized asymmetric nuclear matter

TL;DR

This paper investigates how spin polarization affects the stability and phase separation of asymmetric nuclear matter at zero temperature, revealing that polarization reduces the instability region and influences isospin symmetry restoration.

Contribution

It provides a detailed analysis of spinodal instabilities in polarized asymmetric nuclear matter using the Brueckner--Hartree--Fock approach with an analytical energy density parametrization.

Findings

Spinodal instability region shrinks with increased polarization.

Antiparallel spins result in smaller instability regions than parallel spins.

Polarization diminishes the efficiency of isospin distillation.

Abstract

We analyze the spinodal instabilities of spin polarized asymmetric nuclear matter at zero temperature for several configurations of the neutron and proton spins. The calculations are performed with the Brueckner--Hartree--Fock (BHF) approach using the Argonne V18 nucleon-nucleon potential plus a three-nucleon force of Urbana type. An analytical parametrization of the energy density, which reproduces with good accuracy the BHF results, is employed to determine the spinodal instability region. We find that, independently of the of the orientation of the neutron and proton spins, the spinodal instability region shinks when the system is polarized, being its size smaller smaller when neutron and proton spins are antiparallel than when they are oriented in a parallel way. We find also that the spinodal instability is always dominated by total density fluctuation independently of the degree of polarization of the system, and that restoration of the isospin symmetry in the liquid phase, {\it i.e.,} the so-called isospin distillation or fragmentation effect, becomes less efficient with the polarization of the system.