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Spring Semester 2017

Date / Time Speaker Title Location
1 March 2017
15:45-16:45 		Fanny Kassel
CNRS - IHES
Event Details

Geometry Seminar

Title Proper affine actions of right-angled Coxeter groups
Speaker, Affiliation Fanny Kassel, CNRS - IHES
Date, Time 1 March 2017, 15:45-16:45
Location HG G 43
Abstract The Auslander Conjecture states that all discrete groups acting properly and cocompactly on R^n by affine transformations should be virtually solvable. In 1983, Margulis constructed the first examples of proper (but not cocompact) affine actions of nonabelian free groups. It seems that until now all known examples of irreducible proper affine actions were by virtually solvable or virtually free groups. I will explain that any right-angled Coxeter group on k generators admits a proper affine action on R^{k(k-1)/2}. This is joint work with J. Danciger and F. Guéritaud.
Proper affine actions of right-angled Coxeter groups read_more
HG G 43
15 March 2017
15:45-16:45 		Mentor Stafa
IUPUI Indianapolis
Event Details

Geometry Seminar

Title Polyhedral products and toric topology
Speaker, Affiliation Mentor Stafa, IUPUI Indianapolis
Date, Time 15 March 2017, 15:45-16:45
Location HG G 43
Abstract Polyhedral products are the central objects in the emerging field of toric topology, which stands at the crossroads of equivariant topology, algebraic and symplectic geometry, combinatorics and commutative algebra. In this talk I will give an introduction to these combinatorial constructions in topology, and give a few applications, including calculations of monodromy representations.
Polyhedral products and toric topologyread_more
HG G 43
29 March 2017
15:45-16:45 		Alexandre Martin
Universität Wien
Event Details

Geometry Seminar

Title On the acylindrical hyperbolicity of certain Artin groups
Speaker, Affiliation Alexandre Martin, Universität Wien
Date, Time 29 March 2017, 15:45-16:45
Location HG G 43
Abstract Acylindrical hyperbolicity is a far-reaching generalisation of the notion of relative hyperbolicity that encompasses many classes of groups of interest in geometry and geometric group theory. In this talk, I will present a powerful but easy to apply criterion to show the acylindrical hyperbolicity of certain groups acting on CAT(0) cube complexes. As an application, I will explain how such a criterion can be used to show the acylindrical hyperbolicity of certain Artin groups. (Joint work with Indira Chatterji)
On the acylindrical hyperbolicity of certain Artin groupsread_more
HG G 43
26 April 2017
15:45-16:45 		Romain Tessera
CNRS-Université Paris-Sud
Event Details

Geometry Seminar

Title A Banachic generalization of Shalom's property H_FD
Speaker, Affiliation Romain Tessera, CNRS-Université Paris-Sud
Date, Time 26 April 2017, 15:45-16:45
Location HG G 43
Abstract A group has property H_FD if the first reduced cohomology of unitary representations is supported on finite sub-representations. Shalom has proved that this property is stable under quasi-isometry among amenable groups. We generalize this notion to the class of WAP representations, and we prove that this stronger property holds for a class of locally compact solvable groups including algebraic groups over local fields and their lattices. As a by-product we prove a conjecture of Shalom, namely that solvable finitely generated subgroups of GL(Q) have H_FD. This is joint work with Yves Cornulier
A Banachic generalization of Shalom's property H_FDread_more
HG G 43
3 May 2017
15:45-16:45 		Sang-hyun Kim
Seoul National University
Event Details

Geometry Seminar

Title Obstruction for a virtual C^2 action on the circle
Speaker, Affiliation Sang-hyun Kim, Seoul National University
Date, Time 3 May 2017, 15:45-16:45
Location HG G 43
Abstract When does a group virtually admit a faithful C^2 action on the circle? We provide an obstruction using a RAAG. Examples include all (non-virtually-free) mapping class groups, Out(Fn) and Torelli groups. This answers a question by Farb. (Joint work with Hyungryul Baik and Thomas Koberda)
Obstruction for a virtual C^2 action on the circleread_more
HG G 43
21 June 2017
15:45-16:45 		Robert Kropholler
Tufts University
Event Details

Geometry Seminar

Title An arbitrary cubical dimension gap
Speaker, Affiliation Robert Kropholler, Tufts University
Date, Time 21 June 2017, 15:45-16:45
Location HG G 43
Abstract I will discuss recent work with Chris O’Donnell who proved a cubical decomposition theorem for hyperbolic groups. In joint work, we extended this theorem and use it to give explicit examples of groups with cohomological dimension 2n and cubical dimension 3n.
An arbitrary cubical dimension gapread_more
HG G 43

Organizers: Marc Burger, Manfred Einsiedler, Alessandra Iozzi, Urs Lang, Viktor Schröder, Alessandro Sisto

Archive: SS 24 AS 23 SS 23 AS 22 SS 22 AS 21 AS 20 SS 20 AS 19 SS 19 AS 18 SS 18 AS 17 SS 17 AS 16 SS 16 AS 15 SS 15 AS 14 SS 14 AS 13 SS 13 AS 12 SS 12 AS 11 SS 11 AS 10 SS 10 AS 09 SS 09

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