Phase-shift-equivalent potentials and pion-nucleus reactions

Since pion-nucleus elastic scattering data serve as a measure only of the asymptotic behavior of the outgoing pion wave function, it is possible to introduce transformations which alter the wave function only inside the nucleus, leaving the total and elastic differential cross sections unchanged. Examples are presented which illustrate certain ambiguities in attempts to extract optical potential information from elastic scattering data, and which show how such transformations may also be used as a tool to constrain the pion wave function with inelastic scattering and reaction data