Isospin symmetry breaking in relativistic mean-field theories of nuclear matter

Taking into account σ-, ω- and ρ-mesons, an expression for the interaction function of quasiparticles in non-isoscalar nuclear matter is derived. This medium resembles a state of broken symmetry, which gives rise to a Goldstone boson. It obtains nonzero mass, if the electromagnetic interaction is included. Treating the electromagnetic field self-consistently, dressing factors for the single-particle current in non-isoscalar nuclear matter are determined. As an application, the effective angular momentum g-factor for a single nucleon added at the Fermi surface is calculated. (orig.)