Article thumbnail

Achieving maximum chromatic index in multigraphs

By J.M. McDonald

Abstract

AbstractLet G be a multigraph with maximum degree Δ and maximum edge multiplicity μ. Vizing’s Theorem says that the chromatic index of G is at most Δ+μ. If G is bipartite its chromatic index is well known to be exactly Δ. Otherwise G contains an odd cycle and, by a theorem of Goldberg, its chromatic index is at most Δ+1+Δ−2go−1, where go denotes odd-girth. Here we prove that a connected G achieves Goldberg’s upper bound if and only if G=μCgo and (go−1)∣2(μ−1). The question of whether or not G achieves Vizing’s upper bound is NP-hard for μ=1, but for μ≥2 we have reason to believe that this may be answerable in polynomial time. We prove that, with the exception of μK3, every connected G with μ≥2 which achieves Vizing’s upper bound must contain a specific dense subgraph on five vertices. Additionally, if Δ≤μ2, we prove that G must contain K5, so G must be nonplanar. These results regarding Vizing’s upper bound extend work by Kierstead, whose proof technique influences us greatly here

Publisher: Elsevier B.V.
Year: 2009
DOI identifier: 10.1016/j.disc.2008.04.023
OAI identifier:
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • https://s3-eu-west-1.amazonaws... (external link)
  • https://s3.amazonaws.com/prod-... (external link)
  • Suggested articles


    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.