English

$d$-cluster-free sets with a given matching number

Combinatorics 2019-11-11 v3

Abstract

Let 3dk3\le d\le k and ν0\nu\ge 0 be fixed and F([n]k)\mathcal{F}\subset\binom{[n]}{k}. The matching number of F\mathcal{F}, denoted by ν(F)\nu(\mathcal{F}), is the maximum number of pairwise disjoint sets in F\mathcal{F}, and F\mathcal{F} is dd-cluster-free if it does not contain dd sets with the union of size at most 2k2k and empty intersection. In this paper, we give a lower bound and an upper bound for the maximum size of a dd-cluster-free family with a matching number at least ν+1\nu+1. In particular, our result of the case ν=1\nu=1 settles a conjecture of Mammoliti and Britz. We also introduce a Tur\'{a}n problem in hypergraphs that allows multiple edges, which may be of independent interest.

Keywords

Cite

@article{arxiv.1811.07064,
  title  = {$d$-cluster-free sets with a given matching number},
  author = {Xizhi Liu},
  journal= {arXiv preprint arXiv:1811.07064},
  year   = {2019}
}

Comments

revised according to reviewers' comments

R2 v1 2026-06-23T05:18:49.331Z