Three-particle aspects in anNDapproach to nuclear reactions

Several approximations in a generalized $\frac{N}{D}$ approach to nuclear reactions are tested for the three-nucleon system. A detailed analysis of the analytic structure of the amplitudes for transitions between stable two-particle channels is presented. Three-particle unitarity is treated with a method which preserves the simple structure of the one variable $\frac{N}{D}$ equations. Calculations for the three-nucleon system are compared with the exact solutions of the Amado equations. The importance of exchange contributions to three-particle unitarity is stressed.