English

Triangles in r-wise t-intersecting families

Combinatorics 2022-08-01 v1

Abstract

Let tt, rr, kk and nn be positive integers and F\mathcal{F} a family of kk-subsets of an nn-set VV. The family \CF \CF is r r -wise t t -intersecting if for any F1,,Fr\CF F_1, \ldots, F_r \in \CF , we have \absi=1rFi\gst \abs{\cap_{i = 1}^{r}F_i}\gs t . An r r -wise t t -intersecting family of r+1 r + 1 sets {T1,,Tr+1} \{T_1, \ldots, T_{r + 1}\} is called an (r+1,t) (r + 1,t) -triangle if T1Tr+1\lst1 |T_1 \cap \cdots \cap T_{r + 1}| \ls t - 1 . In this paper, we prove that if n\gsn0(r,t,k) n \gs n_0(r, t, k) , then the r r -wise t t -intersecting family \CF([n]k) \CF \subseteq \binom{[n]}{k} containing the most (r+1,t) (r + 1,t) -triangles is isomorphic to \curlybracesF([n]k):\absF[r+t]\gsr+t1 \curlybraces{F \in \binom{[n]}{k}: \abs{F \cap [r + t]} \gs r + t - 1} . This can also be regarded as a generalized Tur\'{a}n type result.

Keywords

Cite

@article{arxiv.2207.14548,
  title  = {Triangles in r-wise t-intersecting families},
  author = {Jiaqi Liao and Mengyu Cao and Mei Lu},
  journal= {arXiv preprint arXiv:2207.14548},
  year   = {2022}
}

Comments

14 pages

R2 v1 2026-06-25T01:19:36.780Z