Fixed-point definability and polynomial time on graphs with excluded minors

  • Authors:
  • Martin Grohe

  • Affiliations:
  • Humboldt University Berlin, Germany

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 2012

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Abstract

We give a logical characterization of the polynomial-time properties of graphs embeddable in some surface. For every surface S, a property P of graphs embeddable in S is decidable in polynomial time if and only if it is definable in fixed-point logic with counting. It is a consequence of this result that for every surface S there is a k such that a simple combinatorial algorithm, namely “the k-dimensional Weisfeiler-Lehman algorithm”, decides isomorphism of graphs embeddable in S in polynomial time. We also present (without proof) generalizations of these results to arbitrary classes of graphs with excluded minors.