Three-particle equations for a model field theory

An analysis is carried out of an extension of the Lee model which describes the interaction of three fermions, V, N, and W, with a scalar boson through the virtual processes VN+ and WV+. It is shown that the amplitudes for the physical processes V+V+ and V+N+2 can be obtained from the solution of three-particle equations which differ from those of the Amado-Lovelace type as a result of the presence of the absorption channel V+WV+. The techniques used to derive the equations are not peculiar to the model, since they rely mainly on unitarity and analyticity in the subenergy and total energy variables, and hence they can be applied to realistic systems. [NUCLEAR REACTIONS Modified three-particle equations for V-sector of extended Lee model.]