Collective Excitations
and Ground State Correlations

E. Heinz, H. Müther
Institut für Theoretische Physik, Universität Tübingen
72076 Tübingen, Germany

H.A. Mavromatis
Physics Dept., King Fahd University of Petroleum and Minerals
Dhahran 31261, Saudi Arabia

A generalized RPA formalism is presented which treats pp and ph correlations on an equal footing. The effect of these correlations on the single-particle Green function is discussed and it is demonstrated that a self-consistent treatment of the single-particle Green function is required to obtain stable solutions. A simple approximation scheme is presented which incorporates for this self-consistency requirement and conserves the number of particles. Results of numerical calculations are given for ¹⁶O using a G-matrix interaction derived from a realistic One-Boson-Exchange potential.