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Applied Topology

Liam Barham

Subevent of Applied Topology - Sat. AM

Forbes 1022

Eastern Time (US & Canada)

Starts at: 2025-03-08 11:10AM

Ends at: 2025-03-08 11:30AM

Group Actions on Metric Spaces

Liam Barham ⟨blb0081@auburn.edu⟩

Abstract:

Given a metric space X, the Vietoris-Rips complex VR(X) is a classical simplicial complex obtained from X, and a group G acting properly by isometries yields another metric space X/G of the orbits of X under G. There is a canonical way in which G can act on VR(X), so instead using the Vietoris-Rips metric thickening VRm(X) allows a meaningful comparison between VRm(X)/G and VRm(X/G) as metric spaces.

This talk will survey a variety of properties which a group action on a metric space can have with some examples, and culminate with a discussion of the strong r-diameter action, which guarantees that under certain scale parameters VRm(X)/G VRm(X/G). I also discuss a strictly weaker condition and present some open questions concerning the connection between the two. Finally, I will briefly mention some analogous results for the Cech metric thickening.

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