Geometry and Topology Seminar 

 Fall 2009

Time/Location: Fridays 1:20pm/901 Van Vleck Hall

Schedule of talks:

WebCalendar Announcements

cappell
 

TIME               SPEAKER                  TITLE HOST
September 4
Fri, 1:20pm
No Seminar
September 11
Fri, 1:20pm 
Deane Yang (NYU Polytech)
See also Colloquium
[Cancelled]
An information theoretic view of the sharp Sobolev inequality Slemrod
September 18
Fri, 1:20pm 
Laurentiu Maxim
(UW-Madison)
Characteristic classes of complex hypersurfaces
September 25
Fri, 1:20pm 
Sean Paul
(UW-Madison)
Hyperdiscriminants and the Tian-Yau-Donaldson conjecture 1
October 2 
Fri, 1:20pm 
No Seminar
October 9 
Fri, 1:20pm 
Sean Paul
(UW-Madison)
Hyperdiscriminants and the Tian-Yau-Donaldson conjecture 2
October 16 
Fri, 1:20pm 
No Seminar
October 23 
Fri, 1:20pm 
No Seminar
See Donaldson Conference
October 28
Wed, 1:20pm
Sylvain Cappell
(NYU)
Eigenvalues of Laplacians in continuous and discrete geometries Maxim
October 30 
Fri, 1:20pm 
See Colloquim by
Cappell on Wednesday
Seminar held on Wednesday this week. Check above.
November 6 
Fri, 1:20pm 
Aaron Naber
(MIT)
Collapse, Ricci Curvature and Topological \epsilon-regularity Theorems Viaclovsky
November 13
Fri, 1:20pm 
Deane Yang (NYU Polytech)
See also Colloquium
An information theoretic view of the sharp Sobolev inequality Slemrod
November 20
Fri, 1:20pm 
Stefan Wenger
(UIC)
Compactness for manifolds with bounded volume and diameter Maxim
November 27
Fri, 1:20pm 
Thanksgiving Holiday
December 4 
Fri, 1:20pm 
Brian Weber
(Stony Brook)
TBA
December 11 
Fri, 1:20pm 
Manuel Gonzalez Villa
(UIC)
TBA Maxim

Abstracts

Laurentiu : An old problem in geometry and topology is the computation of topological and analytical invariants of complex hypersurfaces, e.g., Betti numbers, Euler characteristic, signature, Hodge-Deligne numbers, etc. While the non-singular case is easier to deal with, the singular setting requires a subtle analysis of the intricate relation between the local and global topological and/or analytical structure of singularities. In this talk I will explain how to compute characteristic classes of complex hypersurfaces in terms of local invariants of singularities.

Paul : A long standing open problem in complex geometry is to find necessary and sufficient conditions for the existence of Kahler Einstein metrics with positive scalar curvature. Conjecturally the existence of such a metric is connected to the projective algebraic geometry of the manifold in question. On the other hand, necessary and sufficient conditions for existence can be formulated in terms of K-energy bounds (this is due to Tian) on the space of Kahler potentials. The question is how these bounds can be deduced from algebraic geometry. Very recently, I have been able to show that the K-energy is bounded below along all "degenerations" if and only if the hyperdiscriminant polytope dominates the Chow polytope. I will discuss these matters in the talk.

Cappell :

Naber : The work of Gromov and Fukaya tells us that a Riemannian manifold with bounded geometry has bounded topology. More specifically if a complete manifold has curvature bounded by one then there is a dimensional constant r(n) so that every ball of radius r has known topology. If one works a little more it can also be said that the ball is Gromov Hausdorff close to a torus quotient of a possibly lower dimenional euclidean ball. The main purpose of this talk is to show that in the case of lower or bounded Ricci that a form of sharp converse holds to this statement. That is a space with Ricci bounds that looks like a space of bounded geometry does in fact have bounded geometry.

Yang :

Wenger : Gromov's compactness theorem for metric spaces asserts that every uniformly compact sequence of metric spaces has a subsequence which converges in the Gromov-Hausdorff sense to a compact metric space. This theorem has been of great importance in Riemannian and metric geometry and also other fields. I will show in this talk that if one replaces the Hausdorff distance appearing in Gromov's theorem by the filling volume or flat distance then every sequence of oriented k-dimensional Riemannian manifolds with a uniform bound on diameter and volume has a subsequence which converges in this new distance to a countably k-rectifiable metric space. In general, such a sequence does not have a subsequence which converges with respect to the Gromov-Hausdorff distance. The new distance mentioned above was first introduced and studied by Christina Sormani and myself. In the talk, which will be self-contained, I will also explain the basic properties of this distance, its relationship with other distances, and illustrate it by examples.

Weber :

Villa :


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