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On the restricted matching of graphs in surfaces

Combinatorics 2010-02-04 v1

Abstract

A connected graph GG with at least 2m+2n+22m+2n+2 vertices is said to have property E(m,n)E(m,n) if, for any two disjoint matchings MM and NN of size mm and nn respectively, GG has a perfect matching FF such that MFM\subseteq F and NF=N\cap F=\varnothing. In particular, a graph with E(m,0)E(m,0) is mm-extendable. Let μ(Σ)\mu(\Sigma) be the smallest integer kk such that no graphs embedded on a surface Σ\Sigma are kk-extendable. Aldred and Plummer have proved that no graphs embedded on the surfaces Σ\Sigma such as the sphere, the projective plane, the torus, and the Klein bottle are E(μ(Σ)1,1)E(\mu(\Sigma)-1,1). In this paper, we show that this result always holds for any surface. Furthermore, we obtain that if a graph GG embedded on a surface has sufficiently many vertices, then GG has no property E(k1,1)E(k-1,1) for each integer k4k\geq 4, which implies that GG is not kk-extendable. In the case of k=4k=4, we get immediately a main result that Aldred et al. recently obtained.

Keywords

Cite

@article{arxiv.1002.0661,
  title  = {On the restricted matching of graphs in surfaces},
  author = {Qiuli Li and Heping Zhang},
  journal= {arXiv preprint arXiv:1002.0661},
  year   = {2010}
}

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9 pages