Comment on the Exterior-Interior Separation in the Three-Body Problem

The exterior-interior separation of the three-body wave function is derived directly from the Faddeev equations by using the Kowalski representation for the two-body $t$ matrices. The formalism clarifies the relationship between the quantum-mechanical observables in three-body breakup experiments and the two- and three-body wave functions in the interior regions. A complete parametrization of three-body breakup amplitudes suggested by this approach provides the generalization of the Watson-Migdal formula to include interference between resonances in different two-body channels.