English

Erd\H{o}s-Gy\'{a}rf\'{a}s problem for partially ordered sets

Combinatorics 2026-05-14 v2

Abstract

Given integers p,q,tp,q,t with 1tp1 \le t \le p and 1qhp(t)1 \le q \le h_p(t), a strong (p,q,t)(p,q,t)-coloring of the Boolean lattice BnB_n is a coloring of its tt-chains such that every induced copy of BpB_p in BnB_n uses at least qq colors on its tt-chains. Let ft(n,p,q)f_t^{\sharp}(n,p,q) denote the minimum number of colors in such a coloring. We study this Boolean-lattice analogue of the Erd\H{o}s-Gy\'{a}rf\'{a}s function.We first show that every finite poset strongly embeds into a Boolean lattice. Combined with a structural Ramsey theorem for finite posets with linear extensions, this implies the existence of the strong Boolean Ramsey number Rk,t(BQ)\mathrm{R}^{\sharp}_{k,t}(\mathcal{B}\mid Q) for every integer k1k\ge1, every t1t\ge1, and every nonempty finite poset QQ. In particular, this gives an affirmative answer to a problem of Cox and Stolee and yields the existence of ft(n,p,2)f_t^{\sharp}(n,p,2). Next, using the symmetric Lov\'asz local lemma, we obtain a probabilistic upper bound on ft(n,p,q)f_t^{\sharp}(n,p,q). Finally, we prove lower bounds by combining Tur\'an-type extremal estimates for tt-chains, a double-counting argument, and a generalized Lubell-type framework for tt-chains.

Keywords

Cite

@article{arxiv.2604.10229,
  title  = {Erd\H{o}s-Gy\'{a}rf\'{a}s problem for partially ordered sets},
  author = {Gyula O. H. Katona and Yaping Mao},
  journal= {arXiv preprint arXiv:2604.10229},
  year   = {2026}
}

Comments

23 pages

R2 v1 2026-07-01T12:04:23.715Z