Angular momentum reduction for physical amplitudes in the three-body problem

We give here an approach to the angular momentum reduction that is tailed to be appropriate for the multichannel structure of the three-body problem. Wherever possible we work directly with the physical scattering amplitudes. We obtain concrete partial-wave expansions of elastic, rearrangement, and breakup amplitudes. For these amplitudes we obtain a coupled two-variable integral equation. The effects of parity, time reversal, and rotational invariance are fully discussed. Finally, we provide expressions for the multichannel partial-wave cross sections, asymptotic coordinate-space wave functions, off-shell unitarity, and the partial-wave version of the optical theorem as well as phase-shift parametrizations of the amplitudes.