English

Forbidding intersection patterns between layers of the cube

Combinatorics 2015-03-23 v2

Abstract

A family AP[n]{\mathcal A} \subset {\mathcal P} [n] is said to be an antichain if A⊄BA \not \subset B for all distinct A,BAA,B \in {\mathcal A}. A classic result of Sperner shows that such families satisfy A(nn/2)|{\mathcal A}| \leq \binom {n}{\lfloor n/2\rfloor}, which is easily seen to be best possible. One can view the antichain condition as a restriction on the intersection sizes between sets in different layers of P[n]{\mathcal P} [n]. More generally one can ask, given a collection of intersection restrictions between the layers, how large can families respecting these restrictions be? Answering a question of Kalai, we show that for most collections of such restrictions, layered families are asymptotically largest. This extends results of Leader and the author.

Keywords

Cite

@article{arxiv.1311.5713,
  title  = {Forbidding intersection patterns between layers of the cube},
  author = {Eoin Long},
  journal= {arXiv preprint arXiv:1311.5713},
  year   = {2015}
}

Comments

16 pages

R2 v1 2026-06-22T02:12:50.845Z