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The covering radius problem for sets of perfect matchings

Combinatorics 2021-09-30 v2

Abstract

Consider the family of all perfect matchings of the complete graph K2nK_{2n} with 2n2n vertices. Given any collection M\mathcal M of perfect matchings of size ss, there exists a maximum number f(n,x)f(n,x) such that if sf(n,x)s\leq f(n,x), then there exists a perfect matching that agrees with each perfect matching in M\mathcal M in at most x1x-1 edges. We use probabilistic arguments to give several lower bounds for f(n,x)f(n,x). We also apply the Lov\'asz local lemma to find a function g(n,x)g(n,x) such that if each edge appears at most g(n,x)g(n, x) times then there exists a perfect matching that agrees with each perfect matching in M\mathcal M in at most x1x-1 edges. This is an analogue of an extremal result vis-\'a-vis the covering radius of sets of permutations, which was studied by Cameron and Wanless (cf. \cite{cameron}), and Keevash and Ku (cf. \cite{ku}). We also conclude with a conjecture of a more general problem in hypergraph matchings.

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Cite

@article{arxiv.1009.0810,
  title  = {The covering radius problem for sets of perfect matchings},
  author = {Cheng Yeaw Ku and Alan J. Aw},
  journal= {arXiv preprint arXiv:1009.0810},
  year   = {2021}
}

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10 pages