Algebraic Geometry Seminar Fall 2011

The seminar meets on Fridays at 2:25 pm in Van Vleck B215.

The schedule for the previous semester is here.

Fall 2011

date	speaker	title	host(s)
Sep. 23	Yifeng Liu (Columbia)	Enhanced Grothendieck's operations and base change theorem for sheaves on Artin stacks	Tonghai Yang
Sep. 30	Andrei Caldararu (UW-Madison)	The Hodge theorem as a derived self-intersection	(local)
Oct. 7	Zhiwei Yun (MIT)	Cohomology of Hilbert schemes of singular curves	Shamgar Gurevich
Oct. 14	Javier Fernández de Bobadilla (Instituto de Ciencias Matematicas, Madrid)	Nash problem for surfaces
Nov. 25	Shamgar Gurevich (Madison)	Canonical Hilbert Space: Why? How? and its Categorification

Spring 2012

date	speaker	title	host(s)
May 4	Mark Andrea de Cataldo (Stony Brook)	TBA	Maxim

Abstracts

Yifeng Liu

TBA

Andrei Caldararu

The Hodge theorem as a derived self-intersection

The Hodge theorem is one of the most important results in complex geometry. It asserts that for a complex projective variety X the topological invariants H^*(X, C) can be refined to new ones that reflect the complex structure. The traditional statement and proof of the Hodge theorem are analytic. Given the multiple applications of the Hodge theorem in algebraic geometry, for many years it has been a major challenge to eliminate this analytic aspect and to obtain a purely algebraic proof of the Hodge theorem. An algebraic formulation of the Hodge theorem has been known since Grothendieck's work in the early 1970's. However, the first purely algebraic (and very surprising) proof was obtained only in 1991 by Deligne and Illusie, using methods involving reduction to characteristic p. In my talk I shall try to explain their ideas, and how recent developments in the field of derived algebraic geometry make their proof more geometric.

Zhiwei Yun

Cohomology of Hilbert schemes of singular curves

Abstract: For a smooth curve, the Hilbert schemes are just symmetric powers of the curve, and their cohomology is easily computed by the H^1 of the curve. This is known as Macdonald's formula. In joint work with Davesh Maulik, we generalize this formula to curves with planar singularities (which was conjectured by L.Migliorini). In the singular case, the compactified Jacobian will play an important role in the formula, and we make use of Ngo's technique in his celebrated proof of the fundamental lemma.