High-momentum phonon exchange and the effective shell-model interaction

The influence of the medium polarisation on the mesons which are exchanged in the shell-model effective interaction is investigated. The calculation of the medium polarisation in nuclear matter allows the treatment of high-momentum excitation tensor correlations and isobar degrees of freedom. Very large medium effects are obtained if the phonons are evaluated in the RPA approximation. A self-consistent treatment of collective features by the inclusion of the induced interaction reduces these effects considerably. Therefore the conclusion obtained in the investigation by Kirson (1971), which was performed for finite nuclei and restricted to excitations of low energy, is confirmed.