Seminar 'The Cone of Numerically Effective Divisors for Spherical Varieties and Gale Duality'

On October 8, 2025, Vladimir Zhgoon will speak on 'The Cone of Numerically Effective Divisors for Spherical Varieties and Gale Duality'.

Abstract:
In the talk I will give a brief introduction to the theory of G-equivariant embeddings of spherical varieties, which can be described in terms of combinatorial data the so-called colored fans, which generalize the fans for toric varieties. Then I will explain how to describe the cone of numerically effective divisors. In the classical literature this cone is described in terms of the convex piecewise-linear functions on the colored fan. Recently it has become clear that in many problems of toric geometry the so-called Gale duality arises in a natural way. I will tell how Gale duality arises in the description of the cone of numerically-effective divisors for spherical varieties (which is the closure of the cone of ample divisors) and the description of the Picard group.

Time and place: 18:00, 11 Pokrovsky Bulvar, Room D202