Off-shell momentum as a variational parameter in calculations of matrix Padé approximants in potential scattering

Abstract

In calculations using matrix Pad\'e approximants, an off-shell momentum (or several off-shell momenta) is introduced. In previous work, this momentum was chosen arbitrarily and not varied. However, it is a variational parameter and may be varied to find points where the phase shift has an extreme value. At such points, the matrix Pad\'e approximants are extraordinarily accurate, even for potentials with strong repulsive cores.