How is the hypersimplex related to the amplituhedron?

Abstract: In 1987, Gelfand-Goresky-MacPherson-Serganova made a beautiful connection between the geometry of the Grassmannian and convex polytopes, via the moment map; the moment map image of the Grassmannian Gr(k,n) is a polytope known as the hypersimplex Delta(k,n). In 2013, motivated by the desire to give a geometric basis for the computation of scattering amplitudes in N=4 SYM, Arkani-Hamed and Trnka introduced the amplituhedron A(n,k,m) as the image of the positive Grassmannian Gr+(k,n) under a linear map Z from R^n to R^{k+m} which is totally positive. While the case m=4 is most relevant to physics, the amplituhedron makes sense for any m. In my talk I will explain some strange parallels between the positroidal subdivisions of the hypersimplex Delta(k+1,n) and the m=2 amplituhedron A(n,k,2). One link is provided by the positive tropical Grassmannian. Attributions: based on joint works with Tomek Lukowski, Matteo Parisi, and David Speyer.

Disclaimer: I'm neither a geometer nor a physicist.

differential geometrymetric geometry

Audience: researchers in the discipline

Western Hemisphere colloquium on geometry and physics

Series comments: Description: Biweekly colloquium of geometers and physicists

This weekly online colloquium features geometers and physicists presenting current research on a wide range of topics in the interface of the two fields. The talks are aimed at a broad audience. They will take place via Zoom on alternate Mondays at 3pm Eastern, noon Pacific, 4pm BRT. Each session features a 60 minute talk, followed by 15 minutes for questions and discussion. You may join the meeting 15 minutes in advance. Questions and comments may be submitted to the moderator via the chat interface during the talk, or presented in person during the Q&A session. These colloquia will be recorded and will be available (linked from the website) asap after the event.