中文

Generalized Erdős--Rogers problems for $r$-uniform hypergraphs

组合数学 2026-07-01 v1

摘要

Let FF and GG be rr-uniform hypergraphs, and let fF,G(n)f_{F,G}(n) be the largest integer mm such that every nn-vertex GG-free rr-graph contains an induced FF-free subgraph on mm vertices. We prove that, if r3r\ge3, FF is nonempty, GG is 22-tightly connected, and there is no homomorphism from GG to FF, then fF,G(n)C(logn)βF,βF=maxP2Fe(P)v(P)1. f_{F,G}(n)\le C(\log n)^{\beta_F}, \qquad \beta_F= \max_{\substack{\emptyset\ne P\subseteq\partial_2F}} \frac{e(P)}{v(P)-1}. For r=3r=3, this confirms a conjecture of He and Nie for tightly connected 33-graphs, sharpening their earlier bound by replacing the exponent maxP2Fe(P)+1v(P)1 \max_{\substack{\emptyset\ne P\subseteq\partial_2F}} \frac{e(P)+1}{v(P)-1} with βF\beta_F. When F=KrrF=K_r^r, our result recovers the Ramsey lower bound r(G,Knr)2Ω(n2/r)r(G,K_n^r)\ge 2^{\Omega(n^{2/r})} whenever GG is 22-tightly connected and non-rr-partite.

引用

@article{arxiv.2607.00732,
  title  = {Generalized Erdős--Rogers problems for $r$-uniform hypergraphs},
  author = {Lulu Dai and Qizhong Lin},
  journal= {arXiv preprint arXiv:2607.00732},
  year   = {2026}
}

备注

10 pages