Cluster algebras and tilings for the m=4 amplituhedron

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Main Authors: Even-Zohar, Chaim, Lakrec, Tsviqa, Parisi, Matteo, Tessler, Ran, Sherman-Bennett, Melissa, Williams, Lauren
Format: Preprint
Published: 2023
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author Even-Zohar, Chaim
Lakrec, Tsviqa
Parisi, Matteo
Tessler, Ran
Sherman-Bennett, Melissa
Williams, Lauren
author_facet Even-Zohar, Chaim
Lakrec, Tsviqa
Parisi, Matteo
Tessler, Ran
Sherman-Bennett, Melissa
Williams, Lauren
contents The amplituhedron $A_{n,k,m}(Z)$ is the image of the positive Grassmannian $Gr_{k,n}^{\geq 0}$ under the map ${Z}: Gr_{k,n}^{\geq 0} \to Gr_{k,k+m}$ induced by a positive linear map $Z:\mathbb{R}^n \to \mathbb{R}^{k+m}$. Motivated by a question of Hodges, Arkani-Hamed and Trnka introduced the amplituhedron as a geometric object whose tilings conjecturally encode the BCFW recursion for computing scattering amplitudes. More specifically, the expectation was that one can compute scattering amplitudes in ${N}=4$ SYM by tiling the $m=4$ amplituhedron $A_{n,k,4}(Z)$ - that is, decomposing the amplituhedron into `tiles' (closures of images of $4k$-dimensional cells of $Gr_{k,n}^{\geq 0}$ on which ${Z}$ is injective) - and summing the `volumes' of the tiles. In this article we prove two major conjectures about the $m=4$ amplituhedron: $i)$ the BCFW tiling conjecture, which says that any way of iterating the BCFW recurrence gives rise to a tiling of the amplituhedron $A_{n,k,4}(Z)$; $ii)$ the cluster adjacency conjecture for BCFW tiles, which says that facets of tiles are cut out by collections of compatible cluster variables for $Gr_{4,n}$. Moreover, we show that each BCFW tile is the subset of $Gr_{k, k+4}$ where certain cluster variables have particular signs. Along the way, we construct many explicit seeds for $Gr_{4,n}$ comprised of high-degree cluster variables, which may be of independent interest in the study of cluster algebras.
format Preprint
id arxiv_https___arxiv_org_abs_2310_17727
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Cluster algebras and tilings for the m=4 amplituhedron
Even-Zohar, Chaim
Lakrec, Tsviqa
Parisi, Matteo
Tessler, Ran
Sherman-Bennett, Melissa
Williams, Lauren
Combinatorics
High Energy Physics - Theory
Mathematical Physics
Algebraic Geometry
05E14, 13F60
The amplituhedron $A_{n,k,m}(Z)$ is the image of the positive Grassmannian $Gr_{k,n}^{\geq 0}$ under the map ${Z}: Gr_{k,n}^{\geq 0} \to Gr_{k,k+m}$ induced by a positive linear map $Z:\mathbb{R}^n \to \mathbb{R}^{k+m}$. Motivated by a question of Hodges, Arkani-Hamed and Trnka introduced the amplituhedron as a geometric object whose tilings conjecturally encode the BCFW recursion for computing scattering amplitudes. More specifically, the expectation was that one can compute scattering amplitudes in ${N}=4$ SYM by tiling the $m=4$ amplituhedron $A_{n,k,4}(Z)$ - that is, decomposing the amplituhedron into `tiles' (closures of images of $4k$-dimensional cells of $Gr_{k,n}^{\geq 0}$ on which ${Z}$ is injective) - and summing the `volumes' of the tiles. In this article we prove two major conjectures about the $m=4$ amplituhedron: $i)$ the BCFW tiling conjecture, which says that any way of iterating the BCFW recurrence gives rise to a tiling of the amplituhedron $A_{n,k,4}(Z)$; $ii)$ the cluster adjacency conjecture for BCFW tiles, which says that facets of tiles are cut out by collections of compatible cluster variables for $Gr_{4,n}$. Moreover, we show that each BCFW tile is the subset of $Gr_{k, k+4}$ where certain cluster variables have particular signs. Along the way, we construct many explicit seeds for $Gr_{4,n}$ comprised of high-degree cluster variables, which may be of independent interest in the study of cluster algebras.
title Cluster algebras and tilings for the m=4 amplituhedron
topic Combinatorics
High Energy Physics - Theory
Mathematical Physics
Algebraic Geometry
05E14, 13F60
url https://arxiv.org/abs/2310.17727