English

On $\mathcal{F}$-multicolor Tur\'{a}n number of hypergraph graphs

Combinatorics 2026-03-25 v5

Abstract

The Ruzsa-Szemer\'{e}di (6,3)(6,3)-problem can be equivalently stated as determining the maximum number of edge-disjoint triangles on nn vertices such that no triangle is formed by edges from three distinct triangle-copies. Gowers and Janzer extended this problem by establishing an analogous result for complete graphs. A natural generalization of the two results, first introduced by Imolay, Karl, Nagy and V\'{a}li, asks for the maximum number of edge-disjoint copies of a graph FF on nn vertices such that no copy of GG is formed by edges originating from distinct FF-copies. This maximum number, denoted by exF(n,G)ex_F(n,G), is called the {\em FF-multicolor Tur\'{a}n number} of GG. This paper focuses on the setting of uniform hypergraphs. We first prove that for kk-uniform hypergraphs G\mathcal{G} and F\mathcal{F}, exF(n,G)=o(nk)ex_{\mathcal{F}}(n,\mathcal{G})=o(n^k) if and only if there exists a homomorphism from G\mathcal{G} to F\mathcal{F}. For degenerate case, we show that exF(n,G)=nko(1)ex_{\mathcal{F}}(n,\mathcal{G})=n^{k-o(1)} whenever G\mathcal{G} contains a kk-uniform tight triangle. These results extend previous results. We further establish corresponding supersaturation and blowup statements. In the non-degenerate setting, we derive matching lower and upper bounds for exF(n,G)ex_{\mathcal{F}}(n,\mathcal{G}). We give a necessary and sufficient condition for exF(n,G)ex_{\mathcal{F}}(n,\mathcal{G}) to fail to attain the upper bound, under the assumption that the extremal graphs for G\mathcal{G} are stable. As an application, we refine a result due to Imolay, Karl, Nagy and V\'{a}li. Furthermore, we completely characterize F\mathcal{F} for which exF(n,G)ex_{\mathcal{F}}(n,\mathcal{G}) does not attain the upper bound when G\mathcal{G} is one of the three special intersecting graphs: Fano plane, extended triangle and rr-book of rr-edges with r=3,4r=3,4.

Keywords

Cite

@article{arxiv.2502.11869,
  title  = {On $\mathcal{F}$-multicolor Tur\'{a}n number of hypergraph graphs},
  author = {Ping Li},
  journal= {arXiv preprint arXiv:2502.11869},
  year   = {2026}
}