Dispersion Relations and Direct Nuclear Reactions

This review is concerned with the application of dispersion relation methods to direct nuclear reactions. We begin with a discussion of the assumptions required to relate analyticity properties to the conventional descriptions of direct-reaction amplitudes. This leads naturally to a description of phenomenological methods such as extrapolation to poles and similar topics. The use of the unitarity condition provides a framework for the discussion of the distorted wave Born approximation from the $S$-matrix point of view Finally we call attention to some dynamical calculations of relevance to our discussion.