Magnetic and density effects on the nucleon axial coupling

TL;DR

This paper investigates how external magnetic fields and baryonic density, similar to conditions in magnetars, affect the nucleon axial coupling constant $g_A$ using QCD sum rules, revealing a decrease in $g_A$ under these conditions.

Contribution

It introduces a QCD sum rule approach to analyze the combined effects of magnetic fields and density on $g_A$, a novel application in magnetar-like environments.

Findings

$g_A$ decreases with increasing magnetic field and density

At nuclear density, $g_A$ is approximately 0.92

Magnetic field has little effect on $g_A$ at nuclear density

Abstract

Using appropriate QCD finite energy sum rules, we discuss the influence of an external magnetic field and baryonic density on the axial-vector coupling constant $g_{A}$. This scenario corresponds to a magnetar environment. We found that $g_{A}$ decreases both as function of the magnetic field strength and the baryonic density. It turns out that at the nuclear density $\rho _{0}$ the axial-vector coupling takes the value $g_{A}^{*} \approx 0.92$. Although $g_{A}$ decreases in general with the magnetic field intensity, $g_{A}^{*}$ does not change in a relevant way with the magnetic field.