Geometry seminar

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Spring Semester 2017

Note: The highlighted event marks the next occurring event.

Date / Time Speaker Title Location
1 March 2017
Fanny Kassel
Proper affine actions of right-angled Coxeter groups   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.
15 March 2017
Mentor Stafa
IUPUI Indianapolis
Polyhedral products and toric topology  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.
29 March 2017
Alexandre Martin
Universität Wien
On the acylindrical hyperbolicity of certain Artin groups  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)
26 April 2017
Romain Tessera
CNRS-Université Paris-Sud
A Banachic generalization of Shalom's property H_FD  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
3 May 2017
Sang-hyun Kim
Seoul National University
Obstruction for a virtual C^2 action on the circle  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)
21 June 2017
Robert Kropholler
Tufts University
An arbitrary cubical dimension gap  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.

Archive: 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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