researchseminars.org

Jake Levinson (University of Washington)
2020-06-11 22:30 - 23:30 UTC | https://researchseminars.org/talk/SFUQNTAG/6/
Title: Boij-Söderberg Theory for Grassmannians (https://researchseminars.org/talk/SFUQNTAG/6/)
by Jake Levinson (University of Washington) as part of SFU NT-AG seminar

Abstract
The Betti table of a graded module over a polynomial ring encodes much of its structure and that of the corresponding sheaf on projective space. In general, it is hard to tell which integer matrices can arise as Betti tables. An easier problem is to describe such tables up to positive scalar multiple: this is the "cone of Betti tables". The Boij-Söderberg conjectures, proven by Eisenbud-Schreyer, gave a beautiful description of this cone and, as a bonus, a "dual" description of the cone of cohomology tables of sheaves.

I will describe some extensions of this theory, joint with Nicolas Ford and Steven Sam, to the setting of GL-equivariant modules over coordinate rings of matrices. Here, the dual theory (in geometry) concerns sheaf cohomology on Grassmannians. One theorem of interest is an equivariant analog of the Boij-Söderberg pairing between Betti tables and cohomology tables. This is a bilinear pairing of cones, with output in the cone coming from the "base case" of square matrices, which we also fully characterize.
