English

On asymptotic local Tur\'an problems

Combinatorics 2024-01-10 v3

Abstract

An rr-uniform hypergraph has (q,p)(q,p)-property if any set of qq vertices spans a complete sub-hypergraph on pp vertices. Let tr(n,q,p)t_r(n,q,p) be the minimum edge density of an nn-vertex rr-uniform hypergraph with {\em (q,p)(q,p)-property} and let tr(q,p)=limntr(n,q,p)t_r(q,p)=\lim_{n\to\infty}t_r(n,q,p). A disjoint union of kk complete hypergraphs has (q,q/k)(q,\lceil q/k\rceil)-property, which gives tr((q,q/k))1/kr1t_r((q,\lceil{q/k}\rceil))\le 1/k^{r-1}. The first author, Huang and R\"odl showed that these constructions are the best asymptotically, that is, limqtr((q,q/k))=1/kr1\lim_{q\to\infty}t_r((q,\lceil{q/k}\rceil))=1/k^{r-1}. They asked whether it is true for all real number γ1\gamma\ge1 that limqtr((q,q/γ))=1/γr1\lim_{q\to\infty}t_r((q,\lceil{q/\gamma}\rceil))=1/\lfloor{\gamma}\rfloor^{r-1}. In this paper, we give positive answers to this question for a small range of real numbers, and, on the other hand, provide new constructions that give negative answers for many other ranges.

Keywords

Cite

@article{arxiv.2303.00375,
  title  = {On asymptotic local Tur\'an problems},
  author = {Peter Frankl and Jiaxi Nie},
  journal= {arXiv preprint arXiv:2303.00375},
  year   = {2024}
}

Comments

12 pages

R2 v1 2026-06-28T08:53:36.952Z