A note on permutation regularity

  • Authors:
  • Carlos Hoppen;Yoshiharu Kohayakawa;Rudini M. Sampaio

  • Affiliations:
  • Instituto de Matemática, UFRGS-Avenida Bento Gonçalves, 9500, 91501-970 Porto Alegre, RS, Brazil;Instituto de Matemática e Estatística, USP-Rua do Matão 1010, 05508-090 São Paulo, SP, Brazil;Departamento de Computação, Centro de Ciências, UFC-Campus do Pici, Bloco 910, 60451-760 Fortaleza, CE, Brazil

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2012

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Abstract

The existence of a small partition of a combinatorial structure into random-like subparts, a so-called regular partition, has proven to be very useful in the study of extremal problems, and has deep algorithmic consequences. The main result in this direction is the Szemeredi Regularity Lemma in graph theory. In this note, we are concerned with regularity in permutations: we show that every permutation of a sufficiently large set has a regular partition into a small number of intervals. This refines the partition given by Cooper (2006) [10], which required an additional non-interval exceptional class. We also introduce a distance between permutations that plays an important role in the study of convergence of a permutation sequence.