Forthcoming Seminars › Seminar Series

Topology Seminar

Mon, 18/10/2010
15:45 		Jason Behrstock (CUNY) Topology Seminar Add to calendar L3
Curve complex projections and the mapping class group
Abstract: We will explain a certain natural way to project elements of the mapping class to simple closed curves on subsurfaces. Generalizing a coordinate system on hyperbolic space, we will use these projections to describe a way to characterize elements of the mapping class group in terms of these projections. This point of view is useful in several applications; time permitting we shall discuss how we have used this to prove the Rapid Decay property for the mapping class group. This talk will include joint work with Kleiner, Minksy, and Mosher.
Mon, 25/10/2010
03:45 		Udo Hertrich-Jeromin (Bath) Topology Seminar Add to calendar L3
Discrete differential geometry: constant mean curvature surfaces
The is the second part of the Analysis and Geometry Seminar today.
Mon, 01/11/2010
15:45 		Tom Leinster (Glasgow) Topology Seminar Add to calendar L3
Analogues of Euler characteristic
There is a close but underexploited analogy between the Euler characteristic of a topological space and the cardinality of a set. I will give a quite general definition of the "magnitude" of a mathematical structure, framed categorically. From this single definition can be derived many cardinality-like invariants (some old, some new): the Euler characteristic of a manifold or orbifold, the Euler characteristic of a category, the magnitude of a metric space, the Euler characteristic of a Koszul algebra, and others. A conjecture states that this purely categorical definition also produces the classical invariants of integral geometry: volume, surface area, perimeter, .... No specialist knowledge will be assumed.
Mon, 08/11/2010
15:45 		Alexandra Pettet (Oxford) Topology Seminar Add to calendar
The fundamental group of $ \text{ Hom}(\bb Z^k,G) $
Let $ G $ be a compact Lie group, and consider the variety $ \text {Hom} (\bb Z^k,G) $ of representations of the rank $ k $ abelian free group $ \bb Z^k $ into $ G $. We prove that the fundamental group of $ \text {Hom} (\bb Z^k,G) $ is naturally isomorphic to direct product of $ k $ copies of the fundamental group of $ G $. This is joint work with Jose Manuel Gomez and Juan Souto.
Mon, 15/11/2010
15:45 		Pierre Pansu (Orsay) Topology Seminar Add to calendar L3
$ L^p $ cohomology and pinching
We prove that no Riemannian manifold quasiisometric to complex hyperbolic plane can have a better curvature pinching. The proof uses cup-products in $ L^p $-cohomology.
Mon, 22/11/2010
15:45 		Nicholas Touikan (Oxford) Topology Seminar Add to calendar L3
To Be Announced

For any corrections/updates to these listings, please contact seminars [-at-] maths [dot] ox [dot] ac [dot] uk.

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