English

On Erd\H{o}s-Ko-Rado for random hypergraphs I

Combinatorics 2014-12-17 v1

Abstract

A family of sets is intersecting if no two of its members are disjoint, and has the Erd\H{o}s-Ko-Rado property (or is EKR) if each of its largest intersecting subfamilies has nonempty intersection. Denote by Hk(n,p)\mathcal{H}_k(n,p) the random family in which each kk-subset of {1n}\{1\dots n\} is present with probability pp, independent of other choices. A question first studied by Balogh, Bohman and Mubayi asks: \mbox{for what $p=p(n,k)$ is $\mathcal{H}_k(n,p)$ likely to be EKR?} Here, for fixed c<1/4c<1/4, and k<cnlognk< \sqrt{cn\log n} we give a precise answer to this question, characterizing those sequences p=p(n,k)p=p(n,k) for which Pr(Hk(n,p) is EKR)1 as n. \Pr(\mathcal{H}_k(n,p) \textrm{ is EKR}) \rightarrow 1 \textrm{ as } n\rightarrow \infty.

Keywords

Cite

@article{arxiv.1412.5085,
  title  = {On Erd\H{o}s-Ko-Rado for random hypergraphs I},
  author = {Arran Hamm and Jeff Kahn},
  journal= {arXiv preprint arXiv:1412.5085},
  year   = {2014}
}

Comments

46 pages

R2 v1 2026-06-22T07:33:43.749Z