Frankl–Wang's 3/73/7 conjecture on maximum-degree ratios

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Let [n]={1,2,…,n}[n]=\{1,2,\dots,n\}, and let ([n]k)\binom{[n]}{k} denote the family of all kk-subsets of [n][n]. A family F⊆([n]k)\mathcal{F}\subseteq\binom{[n]}{k} is intersecting if F∩F′≠∅F\cap F'\neq\emptyset for all F,F′∈FF,F'\in\mathcal{F}. Define

Δ(F)=max⁡x∈[n]∣{F∈F:x∈F}∣,ϱ(F)=Δ(F)∣F∣.\Delta(\mathcal{F})=\max_{x\in[n]}|\{F\in\mathcal{F}:x\in F\}|,\qquad \varrho(\mathcal{F})=\frac{\Delta(\mathcal{F})}{|\mathcal{F}|}.

Frankl–Wang's 3/73/7 conjecture. If F⊆([n]k)\mathcal{F}\subseteq\binom{[n]}{k} is intersecting, n>100kn>100k, and ∣F∣>(n−3k−3)|\mathcal{F}|>\binom{n-3}{k-3}, then

ϱ(F)≥37.\varrho(\mathcal{F})\ge \frac{3}{7}.

The ratio ϱ(F)\varrho(\mathcal{F}) measures concentration on the most popular element, so the conjecture gives a quantitative lower bound on this concentration for sufficiently large intersecting families. The source presents it as a conjecture of Frankl and Wang; no resolution is supplied.

References

Primary source

Zejun Huang, Zhiyi Liu, Lu Lu and Tingzeng Wu, “Thresholds for the Frankl-Wang 3/7 conjecture on maximum-degree ratios”, arXiv:2607.02589 (2026).

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