Amplituhedron meets Jeffrey-Kirwan Residue

TL;DR

This paper links the amplituhedron, a geometric object encoding scattering amplitudes, to the Jeffrey-Kirwan residue, revealing new geometric and combinatorial structures across various dimensions.

Contribution

It establishes a novel connection between amplituhedra and Jeffrey-Kirwan residues, enabling volume computation and structural insights for amplituhedra in any dimension.

Findings

Jeffrey-Kirwan residue can extract amplituhedron volume functions

Revealed combinatorial and geometric structures of amplituhedra

Applied to cyclic polytopes and their conjugates in all dimensions

Abstract

The tree amplituhedra $\mathcal{A}_{n,k}^{(m)}$ are mathematical objects generalising the notion of polytopes into the Grassmannian. Proposed for $m=4$ as a geometric construction encoding tree-level scattering amplitudes in planar $\mathcal{N}=4$ super Yang-Mills theory, they are mathematically interesting for any $m$. In this paper we strengthen the relation between scattering amplitudes and geometry by linking the amplituhedron to the Jeffrey-Kirwan residue, a powerful concept in symplectic and algebraic geometry. We focus on a particular class of amplituhedra in any dimension, namely cyclic polytopes, and their even-dimensional conjugates. We show how the Jeffrey-Kirwan residue prescription allows to extract the correct amplituhedron volume functions in all these cases. Notably, this also naturally exposes the rich combinatorial and geometric structures of amplituhedra, such as their regular triangulations.