English

On growth functions of ordered hypergraphs

Combinatorics 2020-05-22 v1

Abstract

For k,l2k,l\ge2 we consider ideals of edge ll-colored complete kk-uniform hypergraphs (n,χ)(n,\chi) with vertex sets [n]={1,2,n}[n]=\{1, 2, \dots n\} for nNn\in\mathbb{N}. An ideal is a set of such colored hypergraphs that is closed to the relation of induced ordered subhypergraph. We obtain analogues of two results of Klazar [arXiv:0703047] who considered graphs, namely we prove two dichotomies for growth functions of such ideals of colored hypergraphs. The first dichotomy is for any k,l2k,l\ge2 and says that the growth function is either eventually constant or at least nk+2n-k+2. The second dichotomy is only for k=3,l=2k=3,l=2 and says that the growth function of an ideal of edge two-colored complete 33-uniform hypergraphs grows either at most polynomially, or for n23n\ge23 at least as GnG_n where GnG_n is the sequence defined by G1=G2=1G_1=G_2=1, G3=2G_3=2 and Gn=Gn1+Gn3G_n = G_{n-1} + G_{n-3} for n4n\ge4. The lower bounds in both dichotomies are tight.

Keywords

Cite

@article{arxiv.2005.10726,
  title  = {On growth functions of ordered hypergraphs},
  author = {Jaroslav Hančl and Martin Klazar},
  journal= {arXiv preprint arXiv:2005.10726},
  year   = {2020}
}

Comments

43 pages, 7 figures

R2 v1 2026-06-23T15:43:12.588Z