Logarithmic Singularities and Maximally Supersymmetric Amplitudes

TL;DR

This paper explores the singularity structures of scattering amplitudes in N=4 super-Yang-Mills and N=8 supergravity, proposing conjectures that unify their analytic properties and providing explicit constructions and evidence at multiple loops.

Contribution

It introduces conjectures linking logarithmic singularities and dual conformal symmetry in planar and nonplanar amplitudes, with explicit basis constructions and evidence at three, four, and five loops.

Findings

Constructed a basis of integrands with only logarithmic singularities at three loops.

Provided evidence supporting the conjecture that nonplanar amplitudes share singularity properties with planar ones.

Analyzed the singularity structure of N=8 supergravity at three loops, revealing similar properties to N=4 super-Yang-Mills.

Abstract

The dual formulation of planar N = 4 super-Yang-Mills scattering amplitudes makes manifest that the integrand has only logarithmic singularities and no poles at infinity. Recently, Arkani-Hamed, Bourjaily, Cachazo and Trnka conjectured the same singularity properties hold to all loop orders in the nonplanar sector as well. Here we conjecture that to all loop orders these constraints give us the key analytic information contained in dual conformal symmetry. We also conjecture that to all loop orders, while N = 8 supergravity has poles at infinity, at least at four points it has only logarithmic singularities at finite locations. We provide nontrivial evidence for these conjectures. For the three-loop four-point N = 4 super-Yang-Mills amplitude, we explicitly construct a complete basis of diagram integrands that has only logarithmic singularities and no poles at infinity. We then express the complete amplitude in terms of the basis diagrams, with the coefficients determined by unitarity. We also give examples at three loops showing how to make the logarithmic singularity properties manifest via dlog forms. We give additional evidence at four and five loops supporting the nonplanar logarithmic singularity conjecture. Furthermore, we present a variety of examples illustrating that these constraints are more restrictive than dual conformal symmetry. Our investigations show that the singularity structures of planar and nonplanar amplitudes in N = 4 super-Yang-Mills are strikingly similar. While it is not clear how to extend either dual conformal symmetry or a dual formulation to the nonplanar sector, these results suggest that related concepts might exist and await discovery. Finally, we describe the singularity structure of N = 8 supergravity at three loops and beyond.