Arbeitsgruppe Geometrie, Topologie und Gruppentheorie

Mathematisches Institut, Universität Münster

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Tee-Seminar der AG Kramer

Zeit und Ort:

Semester: SS 2013
Zeit: Di 10:30 - 11:30
Ort: SR 1C

Inhalt:

Mitglieder der Arbeitsgruppe tragen über ihre laufenden Forschungsarbeiten vor, oder über Themen, die uns interessieren. Vor dem Seminar (ab 10:00) gibt es in Zimmer 301b Tee.

Vorträge:

23.04.13 Matt Zaremski : Playing ping-pong on a euclidean building

Abstract: It is a longstanding open problem to determine whether the Burau representation of the 4-strand braid group B4 is faithful. In the 1970's, this problem was reduced to proving that a certain pair of 3-by-3 matrices f and k with entries in Z[t,t-1] generate a copy of the free group F2. In joint work with Stefan Witzel, we analyze the action of these matrices on the relevant euclidean building, and deduce that f3 and k3 generate a copy of F2. Unsurprisingly, the work amounts to finding nice subsets for which the Ping-Pong Lemma applies.



7.05.13 Petra Schwer : CAT(0) Braid Groups



14.05.13 Rupert McCallum : Locally compact groups with a unique locally compact sigma-compact topology

Abstract: There are some locally compact sigma-compact groups with the property that there is just one locally compact sigma-compact Hausdorff topology on the carrier set of the group compatible with the group operations. We show how to prove this for a connected centreless Lie group whose Lie algebra is absolutely simple and generalise this to the case where the underlying field is a non-archimedean local field. We also discuss the case of the full automorphism group of a locally finite biregular tree and speculate about whether the result might also be true for certain closed subgroups of the full automorphism group.

28.05.13 Olga Varghese : Actions on CAT(0) cube complexes





Zuletzt geändert: 24.05.13, 13:32:29