Phase Transition and Anisotropic Deformations of Neutron Star Matter

TL;DR

This paper models neutron stars using the Skyrme crystal framework, revealing a transition from isotropic to anisotropic deformation at a critical mass and accurately predicting maximum mass and radius.

Contribution

It introduces a novel approach using Skyrme crystal solutions to model neutron star deformations and mass limits, aligning with recent astronomical observations.

Findings

Neutron stars deform isotropically below 1.49 solar masses.

Above 1.49 solar masses, stars exhibit anisotropic strain.

Maximum neutron star mass predicted as 1.90 solar masses.

Abstract

The Skyrme model is a low energy, effective field theory for QCD which when coupled to a gravitational field provides an ideal semi-classical model to describe neutron stars. We use the Skyrme crystal solution composed of a lattice of $\alpha$-like particles as a building block to construct minimum energy neutron star configurations, allowing the crystal to be strained anisotropically. We find that below 1.49 solar masses the stars' crystal deforms isotropically and that above this critical mass, it undergoes anisotropic strain. We then find that the maximum mass allowed for a neutron star is 1.90 solar masses, in close agreement with a recent observation of the most massive neutron star yet found. The radii of the computed solutions also match the experimentally estimated values of approximately 10km.