English

Triple systems with bounded matching number: some constructions and exact Tur\'{a}n number

Combinatorics 2025-11-24 v1

Abstract

We study the Tur\'{a}n numbers of 33-graphs avoiding 33-graphs FF and Ms+13M_{s+1}^3, a matching of size s+1s+1. We disprove a conjecture of Gerbner, Tompkins, and Zhou [European Journal of Combinatorics, 2025, 127:104155] on \ex(n,{F,Ms+13})\ex(n,\{F,M^3_{s+1}\}) for 33-graph FF with χ(F)=2\chi(F)=2 by constructing infinitely many counterexamples. For this family, we determine the asymptotic Tur\'{a}n number via edge-colored Tur\'{a}n problem. In addition, for the 33-graph F3,2F_{3,2} with edge set {123,145,245,345}\{123,145,245,345\}, we determine the exact value of \ex(n,{F3,2,Ms+13})\ex(n,\{F_{3,2}, M_{s+1}^3\}) for every integers ss and all n12s2n \ge 12s^2.

Keywords

Cite

@article{arxiv.2511.17000,
  title  = {Triple systems with bounded matching number: some constructions and exact Tur\'{a}n number},
  author = {Nannan Chen and Miao Liu and Yuzhen Qi and Caihong Yang},
  journal= {arXiv preprint arXiv:2511.17000},
  year   = {2025}
}