COLD EQUATION OF STATE IN A STRONG MAGNETIC-FIELD - EFFECTS OF INVERSE BETA-DECAY

We study the influence of a high magnetic field (B > 10(12) G) on the degenerate matter equation of state appropriate to a neutron star. We focus on the regime dominated by relativistic electrons up to the neutron drip density. We determine the equilibrium matter composition and equation of state, allowing for inverse beta-decay. We adopt two different equilibrium models: an ideal neutron-proton-electron (npe) gas and the more realistic model of Baym, Pethick, and Sutherland, consisting of a Coulomb lattice of heavy nuclei embedded in an electron gas. For a sufficiently high field strength, the magnetic field has an appreciable effect, changing the adiabatic index of the matter and the nuclear transition densities. We also consider the influence of a strong field on some simple nonequilibrium processes, including beta-decay and inverse beta-decay (electron capture). The effects produced by the magnetic field are mainly due to the changes in the transverse electron quantum orbits and the allowed electron phase space induced by the field.