Given a metric space , the Vietoris-Rips complex VR is a classical simplicial complex obtained from , and a group acting properly by isometries yields another metric space of the orbits of under . There is a canonical way in which can act on VR, so instead using the Vietoris-Rips metric thickening VR allows a meaningful comparison between VR and VR 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 -diameter action, which guarantees that under certain scale parameters VR VR. 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.