English

$C_{10}$ has positive Tur\'an density in the hypercube

Combinatorics 2025-01-08 v3

Abstract

The nn-dimensional hypercube QnQ_n is a graph with vertex set {0,1}n\{0,1\}^n such that there is an edge between two vertices if and only if they differ in exactly one coordinate. For any graph HH, define ex(Qn,H)\text{ex}(Q_n,H) to be the maximum number of edges of a subgraph of QnQ_n without a copy of HH. In this short note, we prove that for any nNn \in \mathbb{N} ex(Qn,C10)>0.024e(Qn).\text{ex}(Q_n, C_{10}) > 0.024 \cdot e(Q_n). Our construction is strongly inspired by the recent breakthrough work of Ellis, Ivan, and Leader, who showed that "daisy" hypergraphs have positive Tur\'an density with an extremely clever and simple linear-algebraic argument.

Keywords

Cite

@article{arxiv.2402.19409,
  title  = {$C_{10}$ has positive Tur\'an density in the hypercube},
  author = {Alexandr Grebennikov and João Pedro Marciano},
  journal= {arXiv preprint arXiv:2402.19409},
  year   = {2025}
}

Comments

6 pages

R2 v1 2026-06-28T15:04:59.106Z