Oliver Club

Daniel Halpern-LeistnerCornell University
Beyond geometric invariant theory

Thursday, August 31, 2017 - 4:00pm
Malott 532

What is a moduli problem, and why do geometers care so much about them? I will answer these questions, and explain how algebraic geometers think about moduli problems. There is an old tension in the subject between the two main frameworks for analyzing moduli problems developed in the 80's: geometric invariant theory, a concrete approach to constructing quotients by group actions developed by Mumford, and the more abstract theory of algebraic stacks, originally proposed by Grothendieck. Both have advantages and disadvantages, but recently a new theory has developed which merges the two and has the advantages of both.

Refreshments will be served at 3:30 PM.