Electromagnetic properties of quasiparticles in a relativistic many-body theory

Using a relativistic meson-nucleon theory we describe both the ground state of nuclear matter and the electromagnetic current of a quasiparticle including vacuum fluctuation effects in the same framework. The energy density of nuclear matter is calculated in the two-loop approximation including also those higher-order effects which are known to be essential for stability, and the quasiparticle current is calculated in the one-loop approximation. Due to the consistency between the description of the strong and electromagnetic interactions, all requirements of gauge invariance can be satisfied. Relativistic corrections to the magnetic g-factors are studied in detail. (orig.)