Topology Seminar
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Mon, 08/10/2007 15:45 |
Martin Bridson (Oxford) |
Topology Seminar  |
L3 |
| Roughly speaking, a quasiregular map is a possibly-branched covering map with bounded distortion. The theory of such maps was developed in the 1970s to carry over to higher dimensions the more geometric aspects of the theory of complex analytic functions of the plane. In this talk I shall outline the proof of rigidity theorems describing the quasiregular self-maps of hyperbolic manifolds. These results rely on an extension of Sela's work concerning the stability of self-maps of hyperbolic groups, and on older topological ideas concerning discrete-open and light-open maps, particularly their effect on fundamental groups. I shall explain how these two sets of ideas also lead to topological rigidity theorems. This talk is based on a paper with a similar title by Bridson, Hinkkanen and Martin (to appear in Compositio shortly). http://www2.maths.ox.ac.uk/~bridson/papers/QRhyp/ | |||
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Mon, 15/10/2007 15:45 |
Ezra Getzler (Nortwestern and Imperial) |
Topology Seminar |
L3 |
| I will present a general formalism for understanding coloured operads of different flavours, such as cyclic operads, modular operads and topological field theories. The talk is based on arXiv:math/0701767. | |||
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Mon, 22/10/2007 15:45 |
Daryl Cooper (USCB and Oxford) |
Topology Seminar |
L3 |
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Mon, 29/10/2007 14:45 |
Tilman Bauer (Muenster) |
Topology Seminar |
L3 |
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Mon, 05/11/2007 14:45 |
Bob Penner (USC and Aarhus) |
Topology Seminar |
L3 |
| Recent joint work with Greg McShane has answered the following question: Which curves can be short in a given cell of the decomposition of Teichmueller space? The answer involves a new combinatorial structure called "screens on fatgraphs" as we shall describe. The techniques of proof involve Fock's path-ordered product expansion of holonomies, Ptolemy transformations, and the triangle inequalities. This is a main step in giving a combinatorial description of the Deligne-Mumford compactification of moduli space which we shall also discuss as time permits. | |||
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Mon, 12/11/2007 14:45 |
Cornelia Drutu (Oxford) |
Topology Seminar |
L3 |
Both Kazhdan and Haagerup properties turn out to be related to actions
of
groups on median spaces and on spaces with measured walls.
These relationships allows to study the connection between Kazhdan
property (T) and the fixed point property
for affine actions on  spaces, on one hand.
On the other hand, they allow to discuss conjugacy classes of subgroups
with property (T) in Mapping Class Groups. The latter result
is due to the existence of a natural structure of measured walls
on the asymptotic cone of a Mapping Class Group.
The talk is on joint work with I. Chatterji and F. Haglund
(first part), and J. Behrstock and M. Sapir (second part). |
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Mon, 19/11/2007 14:45 |
Liz Hanbury (Oxford) |
Topology Seminar |
L3 |
