Yangian symmetry of scattering amplitudes in N=4 super Yang-Mills theory

TL;DR

This paper demonstrates that tree-level scattering amplitudes in N=4 super Yang-Mills theory exhibit a Yangian symmetry, extending the known superconformal symmetry algebra and revealing an intrinsic integrable structure.

Contribution

The paper derives the dual superconformal generators' action, extends them to preserve amplitudes, and shows that combined with standard generators they form a Yangian algebra.

Findings

Yangian symmetry extends superconformal algebra

Dual generators leave amplitudes invariant

Yangian symmetry appears intrinsic at tree level

Abstract

Tree-level scattering amplitudes in N=4 super Yang-Mills theory have recently been shown to transform covariantly with respect to a 'dual' superconformal symmetry algebra, thus extending the conventional superconformal symmetry algebra psu(2,2|4) of the theory. In this paper we derive the action of the dual superconformal generators in on-shell superspace and extend the dual generators suitably to leave scattering amplitudes invariant. We then study the algebra of standard and dual symmetry generators and show that the inclusion of the dual superconformal generators lifts the psu(2,2|4) symmetry algebra to a Yangian. The non-local Yangian generators acting on amplitudes turn out to be cyclically invariant due to special properties of psu(2,2|4). The representation of the Yangian generators takes the same form as in the case of local operators, suggesting that the Yangian symmetry is an intrinsic property of planar N=4 super Yang-Mills, at least at tree level.