Low density nuclear matter with quantum molecular dynamics : The role of the symmetry energy

TL;DR

This study uses quantum molecular dynamics to analyze how isospin-dependent nuclear forces influence the pasta phases in neutron star crusts, revealing limited sensitivity to isospin effects and rapid phase transitions.

Contribution

It introduces a GPU-accelerated QMD simulation to examine the impact of isospin dependence on nuclear pasta phases in neutron star crusts, highlighting the role of higher-order asymmetry terms.

Findings

Pasta phase diagram shows limited sensitivity to isospin effects.

Higher-order asymmetry terms influence energy parameter extraction.

Rapid transition from pasta to homogeneous phase observed.

Abstract

We study the effect of isospin-dependent nuclear forces on the pasta phase in the inner crust of neutron stars. To this end we model the crust within the framework of quantum molecular dynamics (QMD). For maximizing the numerical performance, a newly developed code has been implemented on GPU processors. As a first application of the crust studies we investigate the dependence of the particular pasta phases on the isospin dependence of the interaction, including non-linear terms in this sector of the interactions. Our results indicate that in contrast to earlier studies the phase diagram of the pasta phase is not very sensitive to isospin effects. We show that the extraction of the isospin parameters like asymmetry energy and slope from numerical data is affected by higher-order terms in the asymmetry dependence of the energies per particle. Furthermore, a rapid transition from the pasta to a homogeneous phase is observed even for proton-to-neutron ratios typical for a supernova environment.