Magnetic and density effects on the nucleon axial coupling

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 $g_A^{\ast }\approx 0.92$. Although $g_A$ decreases in general with the magnetic field intensity, $g_A^{\ast }$ does not change in a relevant way with the magnetic field.