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Quasi-flats in hierarchically hyperbolic spaces

Presented by: 
Alessandro Sisto ETH Zürich
Thursday 9th February 2017 -
10:00 to 12:00
INI Seminar Room 2
The notion of hierarchically hyperbolic space provides a common framework to study mapping class groups, Teichmueller spaces with either the Teichmueller or the Weil-Petersson metric, CAT(0) cube complexes admitting a proper cocompact action, fundamental groups of non-geometric 3-manifolds, and other examples.   I will discuss the result that any top-dimensional quasi-flat in a hierarchically hyperbolic space lies within finite Hausdorff distance from a finite union of "standard orthants", a result new for both mapping class groups and cube complexes. Also, I will discuss how this can be used to reduce proving quasi-isometric rigidity results to much more manageable, (mostly) combinatorial problems that require no knowledge about the geometry of HHSs.   Joint work with Jason Behrstock and Mark Hagen.

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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons