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. The talk is in B3.02 Zeeman Buildingon Thursdays, times below. We will open and close the Zoom session on the hour. All of the talks will be streamed at this link.
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06 November 2025 at 13:30 in B3.02
Speaker: Islam Foniqi (University of East Anglia)
Title: TBA
Abstract: TBA
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13 November 2025 at 13:30 in B3.02
Speaker: Will Cohen (University of Cambridge)
Title: TBA
Abstract: TBA
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20 November 2025 at 13:30 in B3.02
Speaker: Sebastian Hensel (LMU Munich)
Title: TBA
Abstract: TBA
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27 November 2025 at 13:30 in B3.02
Speaker: Jing Tao (University of Oklahoma)
Title: TBA
Abstract: TBA
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04 December 2025 at 13:30 in B3.02
Speaker: TBA (TBA)
Title: TBA
Abstract: TBA
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11 December 2025 at 13:30 in B3.02
Speaker: Philipp Bader (University of Glasgow)
Title: TBA
Abstract: TBA
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30 October 2025 at 13:30 in B3.02
Speaker: TBA (TBA)
Title: TBA
Abstract: TBA
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23 October 2025 at 13:30 in B3.02
Speaker: Mahan Mj (Tata Institute of Fundamental Research)
Title: Hyperbolic and elliptic commensurations
Abstract: A group G is said to commensurate a subgroup H, if for all g in G, H^g \cap H is of finite index in H and H^g, where H^g denotes the conjugate of H by g. The commensuration action of G on H can be studied dynamically. This gives rise to two extreme behaviors: hyperbolic and elliptic. We will discuss what these mean and survey a range of theorems and conjectures in this context, starting with work of Mostow and Margulis, and coming to the present day.
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16 October 2025 at 13:30 in B3.02
Speaker: Davide Spriano (University of Warwick)
Title: Curtains, walls and stable cylinders.
Abstract: In this talk we will discuss a generalization of Sageev’s wallspace construction that allows to study the geometry of certain spaces by combinatorial properties of certain walls. Specifically, we’ll look at the interactions with hyperbolicity and focus on two applications. In CAT(0) spaces, these techniques allow to construct a “universal hyperbolic quotient”, called the curtain model, that is analogous to the curve graph of a surface. When focusing on a space that is already hyperbolic, the construction can be used to improve its fine properties, and in particular we address a conjecture of Rips and Sela and show that residually finite hyperbolic groups admit globally stable cylinders. This is joint work with Petyt and Zalloum.
Click on a title to view the abstract!