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Category Archives: seminar
Notes of Viktor Schroeder’s second informal Cambridge lecture 23052017
Moebius structures on boundaries, II 1. Ptolemaic Moebius structures Recall that a Moebius structure is Ptolemaic if crossratios satisfy the Ptolemaic inequality, This means that takes its values in the triangle with vertices at the extra points . Examples Boundaries … Continue reading
Notes of Nicolas Matte Bon’s Cambridge lecture 23052017
Uniformly recurrent subgroups and rigidity of nonfree minimal actions Joint work with A. Le Boudec and T. Tsankov. 1. The Chabauty space of a group Let be a locally compact group. The Chabauty space of is the set of subgroups … Continue reading
Notes of Erik Guentner’s Cambridge lecture 23052017
Affine actions, cohomology and hyperbolicity When can a group act properly on a Hilbert space or an space? I start from scratch. 1. Affine actions a discrete group, a Banach space. We are interested in actions of on where each … Continue reading
Notes of David Kyed’s Cambridge lecture 18052017
Betti numbers of universal quantum groups Joint with Pichon, Arndt, Vaes,… I spoke on the same subject in the same room in 2006. I think my understading has improved. 1. Infinite discrete groups Let act on vectorspace . There are … Continue reading
Notes of Nina Friedrich’s Cambridge lecture 17052017
Homological stability of moduli spaces of highdimensional manifolds 1. Manifolds Say a sequence manifolds and maps satisfies homological stability if induced maps on homomology groups become eventually isomorphisms. How does one prove such a property? We are interested in the … Continue reading
Notes of Viktor Schroeder’s first informal Cambridge lecture 16052017
Moebius structures on boundaries, I This is an informal series of 3 lectures. I start with boundaries of hyperbolic groups. I will continue with Furstenberg boundaries of higher rank symmetric spaces (joint work with my student Beyrer). 1. Moebius structures … Continue reading
Notes of Yves Cornulier’s Cambridge lecture 16052017
Commensurating actions of groups of birational transformations Joint work with Serge Cantat. 1. Birational geometry This is more than a century old. Let be irreducible varieties over . A rational map is a regular (given by the ratio of two … Continue reading