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Infinitely many accumulation points of codegree Tur\'an densities

Combinatorics 2026-02-04 v3

Abstract

The codegree Tur\'an density γ(F)\gamma(F) of a kk-graph FF is the smallest γ[0,1)\gamma\in[0,1) such that every kk-graph HH with δk1(H)(γ+o(1))V(H)\delta_{k-1}(H)\geq(\gamma+o(1))\vert V(H)\vert contains a copy of FF. We prove that for all k,rNk,r\in\mathbb{N} with k3k\geq3, r1r\frac{r-1}{r} is an accumulation point of Γ(k)={γ(F):F is a k-graph}\Gamma^{(k)}=\{\gamma(F):F\text{ is a }k\text{-graph}\}. This makes progress on a problem posed by Mubayi and Zhao.

Keywords

Cite

@article{arxiv.2502.13485,
  title  = {Infinitely many accumulation points of codegree Tur\'an densities},
  author = {Heng Li and Weichan Liu and Bjarne Schülke and Wanting Sun},
  journal= {arXiv preprint arXiv:2502.13485},
  year   = {2026}
}

Comments

8 pages

R2 v1 2026-06-28T21:49:42.563Z