English

The Tur\'{a}n number of Berge matchings

Combinatorics 2026-01-27 v2

Abstract

Given a graph FF, an rr-uniform hypergraph H\mathcal{H} is a {\em Berge-FF} if there is a bijection ϕ:E(F)E(H)\phi:E(F)\to E(\mathcal{H}) such that eϕ(e)e\subseteq \phi(e) for each eE(F)e\in E(F). Given a family F\mathcal{F} of rr-uniform hypergraphs, an rr-uniform hypergraph is F\mathcal{F}-free if it does not contain any member of F\mathcal{F} as a subhypergraph. The Tur\'{a}n number of F\mathcal{F} is the maximum number of hyperedges in an F\mathcal{F}-free rr-graph on nn vertices. Let Ms+1M_{s+1} denote a matching of size s+1s+1, i.e., the graph consisting of s+1s+1 independent edges. Khormali and Palmer [\textit{European J. Combin.} 102 (2022) 103506] completely determined the Tur\'{a}n number of Berge matchings for sufficiently large nn. Subsequently, Kang, Ni, and Shan [\textit{Discrete Math.} 345 (2022) 112901] determined the exact value of the Tur\'{a}n number of Berge-Ms+1M_{s+1} for all nn when rs1r \le s-1 or r2s+2r \ge 2s+2. In this paper, we settle the final open case sr2s+1s \le r \le 2s+1, thereby completing the determination of the Tur\'{a}n number of Berge matchings.

Keywords

Cite

@article{arxiv.2510.05422,
  title  = {The Tur\'{a}n number of Berge matchings},
  author = {Yichen Wang and Zixuan Yang and Xiamiao Zhao and Yuhang Bai and Junpeng Zhou},
  journal= {arXiv preprint arXiv:2510.05422},
  year   = {2026}
}