Medium corrections to the tensor interaction in nuclei: Energy difference of T = 1 and T = 0 J^π = 0^- states in ¹⁶O

It has been shown in the past that in a shell model calculation, restricted to 1hω 1p-1h configurations, the energy splitting between the lowest J^π = 0^-, T = 0 and J^π = 0^-, T = 1 states in ¹⁶O is mainly due to the tensor component of the nucleon-nucleon interction. In this work, we extend the calculation to include 3hω 2p-2h and 3p-3h configurations. We use realistic G matrices derived from various one-boson-exchange potentials, taking into account the effects of the Dirac-Brueckner-Hartree-Fock approach, i.e., a modification of the Dirac spinors for the nucleons in the medium. It is found that the splitting is rather sensitive to the long-range components of the isovector tensor force. The splitting is reduced considerably by including 2p-2h configurations.