A unified approach to distance-two colouring of planar graphs

  • Authors:
  • Omid Amini;Louis Esperet;Jan van den Heuvel

  • Affiliations:
  • Max-Planck-Institut für Informatik, Saarbrücken, Germany;LaBRI (Université de Bordeaux, CNRS), Talence, France;London School of Economics, London

  • Venue:
  • SODA '09 Proceedings of the twentieth Annual ACM-SIAM Symposium on Discrete Algorithms
  • Year:
  • 2009

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Abstract

We introduce the notion of (A, B)-colouring of a graph: For given vertex sets A, B, this is a colouring of the vertices in B so that both adjacent vertices and vertices with a common neighbour in A receive different colours. This concept generalises the notion of colouring the square of graphs and of cyclic colouring of plane graphs. We prove a general result which implies asymptotic versions of Wegner's and Borodin's Conjecture on these two colourings. Using a recent approach of Havet et al., we reduce the problem to edge-colouring of multigraphs and then use Kahn's result that the list chromatic index is close from the fractional chromatic index. Our results are based on a strong structural lemma for planar graphs which also implies that the size of a clique in the square of a planar graph of maximum degree Δ is at most 3/2 Δ plus a constant.