Magnetic field dependence of Delta isobars properties in a Skyrme model

Abstract

The properties of Δ isobars in a uniform magnetic field are investigated. General relations between the magnetic moments of nucleons and Δ isobars in a weak magnetic field are given. In a strong magnetic field, the masses and sizes of Δ isobars depend on the magnetic field strength in different ways: the effective masses of Δ++, Δ+, and Δ0 (the sizes of Δ++ and Δ+) first decrease (increase) and then increase (decrease), whereas the effective mass of Δ- (the sizes of Δ0 and Δ-) always increases (decrease). Our estimates show that, in the core part of the magnetar, the equation of state for Δ isobars depends on the magnetic field, which affects the upper limit on the mass of the magnetar.