Additivity of Scattering Phase Shifts

The additivities of the partial wave phase shifts (APP) and of the phase in the impact parameter representation (AIP) are examined for models of scattering from two centers which simulate nucleon–deuteron and pion–deuteron scatterings. It is shown that the AIP, which essentially leads to the Glauber approximation, holds very well, whereas the APP fails except for a trivial case.