Geometry and Topology
Please contact Saul Schleimer, Davide Spriano, or Robert Kropholler if you would like to speak or to suggest a speaker.
We will also attempt to maintain an up-to-date listing at researchseminars.org.
The seminar will be hybrid, and will be run weekly in term. The talks are physically in B3.02 Zeeman Building on Thursdays, with times as listed below. We will open the Teams session approximately five minutes before the talk starts.
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08 October 2026 at 13:30 in B3.02
Speaker: Ana Isakovic (University of Cambridge)
Title: Top-dimensional \(l^2\)-homology of hyperbolic groups
Abstract: Computing \(l^2\)-homology can be a demanding task especially if one attempts to follow the definition directly. In this talk, I will speak about using automatic structures to construct top-dimensional \(l^2\)-cycles and how they can further be used to compute \(l^2\)-homology of certain hyperbolic groups.
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15 October 2026 at 13:30 in B3.02
Speaker: Thomas Hill (University of Warwick)
Title: Mapping class groups of infinite graphs
Abstract: The group of topological symmetries of a surface, known as the mapping class group, provides a powerful lens for studying the geometry and topology of surfaces. The outer automorphism groups of a free group, Out(\(F_n\)), can be thought of as a graph-theoretic analog of the mapping class group. Although results do not translate directly between the surface and graph settings, their structural parallels inspire questions and techniques between these areas. Over the past decade, there has been a growing interest in studying big mapping class groups, namely those of infinite-type surfaces. In this talk, I will discuss recent progress on the analog of Out(\(F_n\)) for infinite graphs, including a rigidity theorem, results about the algebraic properties of their asymptotically rigid subgroups, and recent work on actions of these groups on hyperbolic spaces, particularly obstructions to general-type actions.
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22 October 2026 at 13:30 in B3.02
Speaker: Laura Wakelin (King's College London (KCL))
Title: TBA
Abstract: TBA
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29 October 2026 at 13:30 in B3.02
Speaker: Dawid Kielak (University of Oxford)
Title: Fibring of Poincare-duality groups
Abstract: I will introduce Pincare-duality groups, and talk about what we know about their virtual fibring properties.
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05 November 2026 at 13:30 in B3.02
Speaker: Danielle West (Tel Aviv University)
Title: TBA
Abstract: TBA
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12 November 2026 at 13:30 in B3.02
Speaker: Koji Fujiwara (Kyoto University)
Title: TBA
Abstract: TBA
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19 November 2026 at 13:30 in B3.02
Speaker: Giovanni Sartori (Heriot-Watt University)
Title: TBA
Abstract: TBA
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26 November 2026 at 13:30 in B3.02
Speaker: Antoine Poulin (University of Warwick)
Title: TBA
Abstract: TBA
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03 December 2026 at 13:30 in B3.02
Speaker: Alexander Nolte (Institut des Hautes Études Scientifiques)
Title: TBA
Abstract: TBA
Click on a title to view the abstract!