Some Results in Computational Topology

  • Authors:
  • G. Tourlakis;J. Mylopoulos

  • Affiliations:
  • Department of Computer Sciences and mathematics, York University, Toronto, Oniario, Canada;Department of Computer Science, University of Toronto, Toronto 181, Ontario, Canada

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 1973

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Abstract

It is the object of this paper to study the topological properties of finite graphs that can be embedded in the n-dimensional integral lattice (denoted Nn). The basic notion of deletability of a node is first introduced. A node is deletable with respect to a graph if certain computable conditions are satisfied on its neighborhood. An equivalence relation on graphs called reducibility and denoted by “∼” is then defined in terms of deletability, and it is shown that (a) most important topological properties of the graph (homotogy, homology, and cohomology groups) are ∼-invariants; (b) for graphs embedded in N3, different knot types belong to different ∼-equivalence classes; (c) it is decidable whether two graphs are reducible to each other in N2 but this problem is undecidable in Nn for n ≥ 4. Finally, it is shown that two different methods of approximating an n-dimensional closed manifold with boundary by a graph of the type studied in this paper lead to graphs whose corresponding homology groups are isomorphic.