The ABCT variety V(3,n) is a positive geometry

The ABCT variety V(3,n) is the image closure of the rational Veronese map from the Grassmannian G(2,n) to the Grassmannian Gr(3,n). It was studied by Arkani-Hamed--Bourjaily--Cachazo--Trnka in the context of tree-level scattering amplitudes arising in planar N=4 supersymmetric Yang-Mills theory and Witten's twistor string theory. From this perspective, V(3,n) was conjectured to be a positive geometry by Lam. In this talk, I will discuss some combinatorial and geometric aspects of V(3,n), showing that it is a positive geometry. This is joint work with Dawei Shen.