Spinodal instabilities of asymmetric nuclear matter within the Brueckner--Hartree--Fock approach

TL;DR

This paper investigates the spinodal instabilities of asymmetric nuclear matter at finite temperature using the Brueckner--Hartree--Fock approach with realistic interactions, comparing results with other nuclear models and analyzing isospin symmetry restoration.

Contribution

It provides a detailed microscopic analysis of spinodal instabilities in asymmetric nuclear matter using the BHF method, highlighting differences with other models and exploring isospin distillation effects.

Findings

BHF predicts a larger spinodal region than Skyrme and relativistic models.

Instability is dominated by total density fluctuations.

Isospin symmetry restoration efficiency varies with proton fraction, temperature, and density.

Abstract

We study the spinodal instabilities of asymmetric nuclear matter at finite temperature within the microscopic Brueckner--Hartree--Fock (BHF) approximation using the realistic Argonne V18 nucleon-nucleon potential plus a three-body force of Urbana type. Our results are compared with those obtained with the Skyrme force SLy230a and the relativistic mean field models NL3 and TW. We find that BHF predicts a larger spinodal region. This result is a direct consequence of the fact that our Brueckner calculation predicts a larger critical temperature and saturation density of symmetric nuclear matter than the Skyrme and relativistic mean field ones. We find that the instability is always dominated by total density fluctuations, in agreement with previous results of other authors. We study also the restoration of the isospin symmetry in the liquid phase, {\it i.e.,} the so-called isospin distillation or fragmentation effect, finding that its efficiency increases with increasing proton fraction and decreases as temperature and density increase. In general, we find that the Brueckner results are comparable to those obtained with the Skyrme and the relativistic mean field models, although the restoration of isospin symmetry is not so efficient in this case.