Variational Principles for Multichannel Feshbach Equations for Scattering and Rearrangement Collisions

Abstract
Variational functionals are constructed for solving Feshbach equations for multichannel scattering and rearrangement collisions. The open-channel and closed-channel components of the state function are varied separately. This separation disentangles the violent fluctuation in the open-channel component from the closed-channel component and speeds up the convergence in the resonance energy region. Numerical illustrations are given for the elastic (e, H) scattering.