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Colouring a graph frugally
Authors:Hugh Hind  Michael Molloy  Bruce Reed
Affiliation:(1) Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Canada;(2) Equipe Combinatoire, CNRS, Université Pierre et Marie Curie, Paris, France;(3) Department of Computer Science, University of Toronto, Toronto, Canada
Abstract:We prove that any graph with maximum degree Delta sufficiently large, has a proper vertex colouring using Delta+1 colours such that each colour class appears at most log8 Delta times in the neighbourhood of any vertex. We also show that for betage1, the minimum number of colours required to colour any such graph so that each vertex appears at most beta times in the neighbourhood of any vertex is theta(Delta+Delta1+1/beta/beta), showing in particular that when beta=logDelta/loglogDelta, such a colouring cannot always be achieved with O(Delta) colours. We also provide a polynomial time algorithm to find such a colouring. This has applications to the total chromatic number of a graph.The second two authors were supported by NATO Collaborative Research Grant #CRG950235.
Keywords:05C15
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