Structure of supersymmetric sums in multiloop unitarity cuts

In this paper we describe algebraic and diagrammatic methods related to the maximally helicity-violating generating function method for evaluating and exposing the structure of supersymmetric sums over the states crossing generalized unitarity cuts of multiloop amplitudes in four dimensions. We focus mainly on cuts of maximally supersymmetric Yang-Mills amplitudes. We provide various concrete examples, some of which are directly relevant for the calculation of four-loop amplitudes. Additionally, we discuss some cases with less-than-maximal supersymmetry. The results of these constructions carry over to generalized cuts of multiloop supergravity amplitudes through use of the Kawai-Lewellen-Tye relations between gravity and gauge-theory tree amplitudes.