English

Erd\H{o}s-Szekeres type Theorems for ordered uniform matchings

Combinatorics 2024-10-01 v2

Abstract

For r,n2r,n\ge2, an ordered rr-uniform matching of size nn is an rr-uniform hypergraph on a linearly ordered vertex set VV, with V=rn|V|=rn, consisting of nn pairwise disjoint edges. There are 12(2rr)\tfrac12\binom{2r}r different ways two edges may intertwine, called here patterns. Among them we identify 3r13^{r-1} collectable patterns PP, which have the potential of appearing in arbitrarily large quantities called PP-cliques. We prove an Erd\H{o}s-Szekeres type result guaranteeing in every ordered rr-uniform matching the presence of a PP-clique of a prescribed size, for some collectable pattern PP. In particular, in the diagonal case, one of the PP-cliques must be of size Ω(n31r)\Omega\left( n^{3^{1-r}}\right). In addition, for each collectable pattern PP we show that the largest size of a PP-clique in a random ordered rr-uniform matching of size nn is, with high probability, Θ(n1/r)\Theta\left(n^{1/r}\right).

Keywords

Cite

@article{arxiv.2301.02936,
  title  = {Erd\H{o}s-Szekeres type Theorems for ordered uniform matchings},
  author = {Andrzej Dudek and Jarosław Grytczuk and Andrzej Ruciński},
  journal= {arXiv preprint arXiv:2301.02936},
  year   = {2024}
}
R2 v1 2026-06-28T08:06:20.773Z