A new treatment of correlations in reaction theory

The problem of correlations in reaction theory is treated making use of relationships between the S-matrix and appropriate correlation functions. The correlation functions are calculated from the resolvent matrix with the help of Feshbach's projection operator technique, generalized in such a way that correlations can be incorporated. A perturbation procedure in terms of a continued fraction expansion can be defined which avoids the well known divergence problems of the Born series. As a byproduct a conceptually and numerically simple treatment of single particle resonances is obtained and worked out in an example. (orig.)