Nuclear currents in a relativistic mean-field theory

Three-vector currents for nuclear matter with one valence particle outside a filled Fermi sphere are studied in the mean-field approximation to the Walecka model. Due to self-consistency, the added valence particle modifies the core by mixing the positive-energy Dirac core wave functions with their negative-energy counterparts with the same three-momentum. This mixing is implicit in the self-consistent mean-field calculation but can also be understood in terms of the linear response function at zero four-momentum transfer. The core contribution to the isoscalar three-vector current cancels the enhancement arising from the reduced mass M ^∗ of the valence particle; in contrast, the core has a small effect on the isovector current. Implications for isoscalar magnetic moments of odd- A nuclei are discussed, and results are illustrated for elastic magnetic scattering of electrons from ¹⁷O and ²⁰⁹Bi.