T-Matrix Perturbation Theory and Its Application to the Faddeev Equations

A $T$-matrix perturbation theory is developed and applied to the Faddeev equations. This theory allows one to calculate the shift in the three-body binding energy produced by any part of the two-body $T$ matrix which is neglected in a three-body calculation. Since the perturbation series is given in terms of an operator closely related to the two-body $T$ matrix, the theory can be applied even when extremely singular potentials are used to describe the two-body interaction.