Effect of isovector-scalar meson on neutron-star matter in strong magnetic fields

Abstract

Within the mean-field approximation to the Lagrangian field theory, we study the effects of isovector-scalar meson δ on nucleon effective masses and the equation of state (EOS) of neutron-star matter in strong magnetic fields. We find that the δ-field leads to a large splitting of proton and neutron effective masses in neutron-star matter. The strength of the δ-field decreases, however, with the increase of the magnetic field and is near zero at ultrastrong field. Although the proton effective mass is found to be highly influenced by magnetic fields, the effect of magnetic fields on the neutron effective mass is negligible. The EOS of neutron-star matter turns out to be stiffer at B < 1015 G but becomes softer at stronger magnetic field after including the δ-field. The effect due to the anomalous magnetic moments of both nucleons and lepton is also studied and is found to be appreciable only at ultrastrong magnetic field (B > 1019 G). In the range of 1015–1018 G, the properties of neutron-star matter remain similar to those without magnetic fields.