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Applied Topology

Johnathan Bush

Subevent of Applied Topology - Sat. PM

Forbes 1022

Eastern Time (US & Canada)

Starts at: 2025-03-08 02:45PM

Ends at: 2025-03-08 03:05PM

The connectivity of Vietoris-Rips complexes of spheres

Johnathan Bush ⟨bush3je@jmu.edu⟩

Abstract:

Although Vietoris–Rips complexes are frequently used in topological data analysis to approximate the “shape” of a dataset, their theoretical properties are not fully understood. In the case of the circle, these complexes exhibit a surprising progression of homotopy types (from S1 to S3 to S5, etc.) as the scale increases. However, much less is known about the Vietoris–Rips complexes of higher-dimensional spheres. I will present work that explores Vietoris–Rips complexes of the n-sphere Sn and shows how the appearance of nontrivial homotopy groups of VR(Sn;t) can be controlled by covering properties of Sn and real projective space RPn. Specifically, if the first nontrivial homotopy group of VR(Sn;πt) occurs in dimension k, then Sn can be covered by 2k+2 balls of radius t, but there is no covering of RPn by k balls of radius t/2. This is joint work with Henry Adams and Žiga Virk.

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