The pachner graph and the simplification of 3-sphere triangulations

  • Authors:
  • Benjamin A. Burton

  • Affiliations:
  • The University of Queensland, Brisbane, QLD 4072, Australia

  • Venue:
  • Proceedings of the twenty-seventh annual symposium on Computational geometry
  • Year:
  • 2011

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Abstract

It is important to have fast and effective methods for simplifying 3-manifold triangulations without losing any topological information. In theory this is difficult: we might need to make a triangulation super-exponentially more complex before we can make it smaller than its original size. Here we present experimental work suggesting that for 3-sphere triangulations the reality is far different: we never need to add more than two tetrahedra, and we never need more than a handful of local modifications. If true in general, these extremely surprising results would have significant implications for decision algorithms and the study of triangulations in 3-manifold topology. The algorithms behind these experiments are interesting in their own right. Key techniques include the isomorph-free generation of all 3-manifold triangulations of a given size, polynomial-time computable signatures that identify triangulations uniquely up to isomorphism, and parallel algorithms for studying finite level sets in the infinite Pachner graph.