External-emission dominance in pion-proton bremsstrahlung

The differential cross section for ..pi../sup + -/p ..-->.. ..pi../sup + -/p..gamma.. in the ..delta.. resonance region can be described in detail by an ''external-emission dominance'' calculation in which the matrix element is based on the first term in the soft-photon expansion of Low. The matrix element is gauge- and Lorentz-invariant and has no free parameters. (AIP)