Reggeon cuts in a multiparticle unitary model I Three-particle case

The authors investigate the reggeon cuts in a model derived from phi /sup 3/ theory, which exhibits three-particle unitarity in the non- asymptotic channel. They use momentum-space techniques to derive the asymptotic behaviour of the Feynman diagrams and discuss the anomalous structure of certain low-order contributions. Finally they show how the integral equation for the partial-wave amplitude can be used to derive the discontinuity formula across the reggeon cut which turns out to have the same structure and sign as that of the original Mandelstam contribution. (16 refs).