English

An almost complete $t$-intersection theorem for permutations

Combinatorics 2024-05-14 v1 Discrete Mathematics

Abstract

For any ϵ>0\epsilon>0 and n>(1+ϵ)tn>(1+\epsilon)t, n>n0(ϵ)n>n_0(\epsilon) we determine the size of the largest tt-intersecting family of permutations, as well as give a sharp stability result. This resolves a conjecture of Ellis, Friedgut and Pilpel (2011) and shows the validity of conjectures of Frankl and Deza (1977) and Cameron (1988) for n>(1+ϵ)tn>(1+\epsilon )t. We note that, for this range of parameters, the extremal examples are not necessarily trivial, and that our statement is analogous to the celebrated Ahlswede-Khachatrian theorem. The proof is based on the refinement of the method of spread approximations, recently introduced by Kupavskii and Zakharov (2022).

Keywords

Cite

@article{arxiv.2405.07843,
  title  = {An almost complete $t$-intersection theorem for permutations},
  author = {Andrey Kupavskii},
  journal= {arXiv preprint arXiv:2405.07843},
  year   = {2024}
}
R2 v1 2026-06-28T16:25:32.602Z