Simplifying $D$-Dimensional Physical-State Sums in Gauge Theory and Gravity

Understand

We provide two independent systematic methods of performing $D$-dimensional physical-state sums in gauge theory and gravity in such a way so that spurious light-cone singularities are not introduced.

• A natural application is to generalized unitarity in the context of dimensional regularization or theories in higher spacetime dimensions.
• Other applications include squaring matrix elements to obtain cross sections, and decompositions in terms of gauge-invariant tensors.