Constraints on the relativistic mean field of Δ-isobar in nuclear matter

The effects of the presence of Δ-isobars in nuclear matter are studied in the framework of relativistic mean-field theory. The existence of stable nuclei at saturation density imposes constraints on the Δ-isobar self-energy and thereby on the mean-field coupling constants of the scalar and vector mesons with Δ-isobars. The range of possible values for the scalar and vector coupling constants of Δ-isobars with respect to the nucleon coupling is investigated and compared to recent predictions of QCD sum-rule calculations