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Mellissa Sherman-Bennett:The hypersimplex and the m=2 amplituhedron

Time: Wed 2022-02-02 15.15 - 16.15

Location: Zoom meeting ID: 654 5562 3260

Participating: Mellissa Sherman-Bennett (University of Michigan)

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Abstract: I'll discuss a curious correspondence between the m=2 amplituhedron, a 2k-dimensional subset of Gr(k, k+2), and the hypersimplex, an (n-1)-dimensional polytope in R^n. The amplituhedron and hypersimplex are both images of the totally nonnegative Grassmannian under some map (the amplituhedron map and the moment map, respectively), but are different dimensions and live in very different ambient spaces.
I'll talk about joint work with Matteo Parisi and Lauren Williams in which we give a bijection between decompositions of the amplituhedron and
decompositions of the hypersimplex (originally conjectured by Lukowski--Parisi--Williams). Along the way, we prove the sign-flip
description of the m=2 amplituhedron conjectured by Arkani-Hamed--Thomas--Trnka and give a new decomposition of the m=2
amplituhedron into Eulerian-number-many chambers, inspired by an analogous hypersimplex decomposition.

Zoom meeting ID: 654 5562 3260

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