A new approach to giant resonances in nuclei

The absorptive part of the response function for-transitions between the ground state and excited states of even-even nuclei is calculated using correlation function techniques. The absorptive part of the response function is expressed in terms of symmetrized correlation functions; these, in turn, are obtained as matrix elements of a properly defined resolvent operator using a generalization of Feshbach's projection operator technique. It is shown how the coupling of RPA states to the one-particle continuum and to more complicated excitations can be treated.