COLLECTIVE EXCITATIONS AND GROUND-STATE CORRELATIONS

A generalized RPA formalism is presented which treats pp and ph correl ations on an equal footing. The effect of these correlations on the si ngle-particle Green function is discussed and it is demonstrated that a self-consistent treatment of the single-particle Green function is r equired to obtain stable solutions. A simple approximation scheme is p resented which incorporates for this self-consistency requirement and conserves the number of particles. Results of numerical calculations a re given for O-16 using a G-matrix interaction derived from a realisti c one-boson-exchange potential.