Nucleon axial-vector coupling constant in magnetar environments

TL;DR

This study investigates how the nucleon axial-vector coupling constant $g_A$ changes in dense nuclear matter and magnetic fields, relevant for understanding magnetar environments, using QCD sum rules.

Contribution

It provides the first analysis of $g_A$ in magnetar-like conditions, combining density and magnetic field effects via QCD sum rules.

Findings

$g_A$ decreases with increasing density and magnetic field.

At nuclear density, $g_A^* \\approx 0.92$.

Magnetic fields cause a general decrease in $g_A$, but $g_A^*$ remains relatively stable.

Abstract

The nucleon axial-vector coupling constant $g_A$ is studied in the presence of an external magnetic field, and in dense nuclear environments, to emulate nuclear matter in magnetars. For this purpose we use QCD finite energy sum rules for two-current and three-current correlators, the former involving nucleon-nucleon correlators and the latter involving proton-axial-neutron currents. As a result, the axial-vector coupling constant decreases both with baryon density as well as with magnetic field. The axial-vector coupling evaluated with baryon density near the nuclear density $\rho_0$ leads to $g_A^*\approx 0.92$. In the presence of magnetic fields $g_A$ decreases in general, but $g_A^*$ does not show significant changes.