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Asymptotically optimal neighbour sum distinguishing total colourings of graphs

Combinatorics 2015-08-06 v1

Abstract

Consider a simple graph G=(V,E)G=(V,E) of maximum degree Δ\Delta and its proper total colouring cc with the elements of the set {1,2,,k}\{1,2,\ldots,k\}. The colouring cc is said to be \emph{neighbour sum distinguishing} if for every pair of adjacent vertices uu, vv, we have c(u)+euc(e)c(v)+evc(e)c(u)+\sum_{e\ni u}c(e)\neq c(v)+\sum_{e\ni v}c(e). The least integer kk for which it exists is denoted by χ"(G)\chi"_{\sum}(G), hence χ"(G)Δ+1\chi"_{\sum}(G) \geq \Delta+1. On the other hand, it has been daringly conjectured that just one more label than presumed in the famous Total Colouring Conjecture suffices to construct such total colouring cc, i.e., that χ"(G)Δ+3\chi"_{\sum}(G) \leq \Delta+3 for all graphs. We support this inequality by proving its asymptotic version, χ"(G)(1+o(1))Δ\chi"_{\sum}(G) \leq (1+o(1))\Delta. The major part of the construction confirming this relays on a random assignment of colours, where the choice for every edge is biased by so called attractors, randomly assigned to the vertices, and the probabilistic result of Molloy and Reed on the Total Colouring Conjecture itself.

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Cite

@article{arxiv.1508.01062,
  title  = {Asymptotically optimal neighbour sum distinguishing total colourings of graphs},
  author = {Jakub Przybyło},
  journal= {arXiv preprint arXiv:1508.01062},
  year   = {2015}
}

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19 pages