Consistency of multidimensional combinatorial substitutions

  • Authors:
  • Timo Jolivet;Jarkko Kari

  • Affiliations:
  • FUNDIM, Department of Mathematics, University of Turku, Finland and LIAFA, Université Paris 7, France;FUNDIM, Department of Mathematics, University of Turku, Finland

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2012

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Abstract

Multidimensional combinatorial substitutions are rules that replace symbols by finite patterns of symbols in Z^d. We focus on the case where the patterns are not necessarily rectangular, which requires a specific description of the way they are glued together in the image by a substitution. Two problems can arise when defining a substitution in such a way: it can fail to be consistent, and the patterns in an image by the substitution might overlap. We prove that it is undecidable whether a two-dimensional substitution is consistent or overlapping, and we provide practical algorithms to decide these properties in some particular cases.