Testing contractibility in planar rips complexes

  • Authors:
  • Erin W. Chambers;Jeff Erickson;Pratik Worah

  • Affiliations:
  • UIUC, Urbana, IL, USA;UIUC, Urbana, IL, USA;UIUC, Urbana, IL, USA

  • Venue:
  • Proceedings of the twenty-fourth annual symposium on Computational geometry
  • Year:
  • 2008

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Abstract

The (Vietoris-)Rips complex of a discrete point-set P is an abstract simplicial complex in which a subset of P defines a simplex if and only if the diameter of that subset is at most 1. We describe an efficient algorithm to determine whether a given cycle in a planar Rips complex is contractible. Our algorithm requires O(m log n) time to preprocess a set of n points in the plane in which m pairs have distance at most 1; after preprocessing, deciding whether a cycle of k Rips edges is contractible requires O(k) time. We also describe an algorithm to compute the shortest non-contractible cycle in a planar Rips complex in O(n2log n + mn) time.