Hello everyone,

This week in topology we have Jonathan Spreer returning to give a talk. The talk is available via the usual link:

https://meet.google.com/frv-bgow-byi

Here are the other relevant details:

Title: Linking topology and combinatorics: Width-type parameters of 3-manifolds Speaker: Jonathan Spreer, University of Sydney Date: Feb 24, 2021 Time: 3:30 PM Room: Virtual

Abstract: Many fundamental topological problems about 3-manifolds are algorithmically solvable in theory but continue to withstand practical computations. In recent years some of these problems have been shown to allow efficient solutions, if the input 3-manifold comes with a sufficiently ”thin” presentation.

More specifically, a 3-manifold given as a triangulation is considered thin, if the treewidth of its dual graph is small. I will show how this combinatorial parameter, defined on a triangulation, can be linked back to purely topological properties of the underlying manifold. From this connection it can then be followed that, for some 3-manifolds, we cannot hope for a thin triangulation.

Also, for any Australians stopping by (including the speaker), the talk is Thursday, 8:30AM AEDT

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Neil R. Hoffman Assistant Professor Department of Mathematics 523 Math Science Building Oklahoma State University Stillwater, OK 74078-1058 405-744-7791 http://math.okstate.edu/people/nhoffman