English

A remark on the $t$-intersecting Erd\H{o}s-Ko-Rado theorem

Combinatorics 2025-07-16 v1

Abstract

The tt-intersecting Erd\H{o}s-Ko-Rado theorem is the following statement: if F([n]k)\mathcal{F} \subset \binom{[n]}{k} is a tt-intersecting family of sets and n(t+1)(kt+1)n\ge (t+1)(k-t+1), then F(ntkt)|\mathcal{F}| \le \binom{n-t}{k-t}. The first proof of this statement for all tt was a linear algebraic argument of Wilson. Earlier, Schrijver had proven the tt-intersecting Erd\H{o}s-Ko-Rado theorem for sufficiently large nn by a seemingly different linear algebraic argument motivated by Delsarte theory. In this note, we show that the approaches of Schrijver and Wilson are in fact equivalent.

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Cite

@article{arxiv.2507.11285,
  title  = {A remark on the $t$-intersecting Erd\H{o}s-Ko-Rado theorem},
  author = {William Linz},
  journal= {arXiv preprint arXiv:2507.11285},
  year   = {2025}
}