Abstract
We present multichannel nuclear reaction formalisms based on the Schwinger and Kohn variational principles. Our formalisms seem somewhat simpler in form than those heretofore proposed. The necessity of using the entire set of asymptotic boundary conditions to constrain the trial wave function is stressed. We show how this may be done by employing the coupled integral equations formalism discussed by Baer and Kouri, Kouri and Levin, and by Tobocman. Several explicit expressions for the transition amplitude are presented which appear to provide a promising basis for doing many-body system scattering reaction calculations.