Global Residues and Two-Loop Hepta-Cuts

Understand

We examine maximal unitarity in the nonplanar case and derive remarkably compact analytic expressions for coefficients of master integrals with two-loop crossed box topology in massless four-point amplitudes in any gauge theory, thereby providing additional steps towards automated computation of the full amplitude.

• The coefficients are obtained by assembling residues extracted through integration on linear combinations of higher-dimensional tori encircling global poles of the loop integrand.
• We recover all salient features of two-loop maximal unitarity, such as the existence of unique projectors for each master integral.
• Several explicit calculations are provided.