Topology Seminar (past)
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Mon, 21/01/2008 14:45 |
Saul Schleimer (Warwick) |
Topology Seminar  |
L3 |
| The arc complex is a combinatorial moduli space, very similar to the curve complex. Using the techniques of Masur and Minsky, as well as new ideas, I'll sketch the theorem of the title. (Joint work with Howard Masur.) If time permits, I'll discuss an application to the cusp shapes of fibred hyperbolic three-manifolds. (Joint work with David Futer.) We are planning to have dinner at Chiang Mai afterwards. If anyone would like to join us, please can you let me know today, as I plan to make a booking this evening. (Chiang Mai can be very busy even on a Monday.) | |||
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Mon, 14/01/2008 14:45 |
Jessica Purcell (Oxford) |
Topology Seminar |
L3 |
| The complement of a knot or link is a 3-manifold which admits a geometric structure. However, given a diagram of a knot or link, it seems to be a difficult problem to determine geometric information about the link complement. The volume is one piece of geometric information. For large classes of knots and links with complement admitting a hyperbolic structure, we show the volume of the link complement is bounded by the number of twist regions of a diagram. We prove this result for a large collection of knots and links using a theorem that estimates the change in volume under Dehn filling. This is joint work with Effie Kalfagianni and David Futer | |||
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Mon, 19/11/2007 14:45 |
Liz Hanbury (Oxford) |
Topology Seminar |
L3 |
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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, 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, 29/10/2007 14:45 |
Tilman Bauer (Muenster) |
Topology Seminar |
L3 |
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Mon, 22/10/2007 15:45 |
Daryl Cooper (USCB and Oxford) |
Topology Seminar |
L3 |
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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, 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, 11/06/2007 15:45 |
Andrew Ranicki (Edinburgh) |
Topology Seminar |
L3 |
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Mon, 04/06/2007 15:45 |
Johannes Ebert (Oxford) |
Topology Seminar |
L3 |
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Mon, 28/05/2007 15:45 |
Topology Seminar |
L3 | |
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Mon, 21/05/2007 15:45 |
Kevin Costello (Northwestern) |
Topology Seminar |
L3 |
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Mon, 14/05/2007 15:45 |
Max Karoubi (Paris) |
Topology Seminar |
L3 |
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Mon, 07/05/2007 15:45 |
Jesper Grodal (Copenhagen) |
Topology Seminar |
L3 |
| In this talk I will show how one can sometimes "uncomplete" the p-completed classifying space of a finite group, to obtain the original (non-completed) classifying space, and hence the original finite group. This "uncompletion" process is closely related to well-known local-to-global questions in group theory, such as the classification of finite simple groups. The approach goes via the theory of p-local finite groups. This talk is a report on joint work with Bob Oliver. | |||
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Mon, 30/04/2007 15:45 |
Alex Coward (Oxford) |
Topology Seminar |
L3 |
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Mon, 23/04/2007 15:45 |
Topology Seminar |
L3 | |
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Mon, 05/03/2007 15:45 |
Paul Mitchener (Gottingen) |
Topology Seminar |
L3 |
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Mon, 05/03/2007 14:15 |
Paul Baum (Penn State) |
Topology Seminar |
L3 |
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Mon, 26/02/2007 15:45 |
John Jones (Warwick) |
Topology Seminar |
L3 |
