Monthly Archives: June 2012

Notes of Christophe Pittet’s lecture

Spheres in horospheres 1. The result Conjecture. -filling is exponential for non uniform irreducible lattices in rank lattices. Thurston did it for . Wortman solved the conjecture in most cases for simple ambient groups, when the -rank is maximal. Theorem … Continue reading

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Notes of Nicholas Touikan’s lecture

Hierarchical accessibility of relatively hyperbolic groups joint with Lars Louder Let be hyperbolic relative to some family P of parabolic subgroups. Assume is torsion free (non 2-torsion would suffice). Let be an elementary family of subgroups. could be trivial, , … Continue reading

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Notes of Bogdan Nica’s lecture

Proper isometric actions of hyperbolic groups on spaces As far as affine isometric actions on spaces, hyperbolic groups may have Kazhdan’s property, Haagerup property, or neither. As far as affine isometric actions on spaces, Yu’s theorem asserts that Theorem 1 … Continue reading

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Notes of Alain Valette’s Lille lecture

Graphs of groups and the Haagerup property joint with Yves Cornulier 1. The Haagerup property 1.1. Basics Definition 1 has Haagerup property if it has a proper affine sometric action on some Hilbert space. Gromov calls them a-T-menable. Example 1 … Continue reading

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Notes of Robert Young’s lecture

Filling functions and non-positive curvature Continuation of Leuzinger’s talk. I will bring support to his conjecture and explain why it is so hard. And then describe some preliminary results. 1. and is the semi-direct product of by acting by diagonal … Continue reading

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Notes of Yves Cornulier’s lecture

Dehn functions of Lie groups joint with Romain Tessera Sample application to finitely generated groups: The Dehn function of a polycyclic group is either exponential or at most polynomial. 1. Basic facts Dehn function makes sense for compactly presented locally … Continue reading

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Notes of Kevin Wortman’s lecture

Cohomology of arithmetic groups over function fields I show that , a prime field, virtually has infinite . 1. The problem More generally, we deal with finite extensions of (functions on ), like (functions on an elliptic curve). And rings … Continue reading

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