Completeness conjecture for weighted extremal families in the Erdős–Kleitman problem

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Write n=sm+c=s(m+1)−ℓn=sm+c=s(m+1)-\ell, and for 0≤k≤m0\le k\le m define

Hk(m,s,ℓ)={F⊆[n] ⁣:k∣F∣+∣F∩[ak]∣≥m(k+1)},ak=ms−kc−1,\mathcal H^k(m,s,\ell)=\{F\subseteq[n]\colon k|F|+|F\cap[a_k]|\ge m(k+1)\},\qquad a_k=ms-kc-1,

and let P(m,s,ℓ)\mathcal P(m,s,\ell) be the shifted family {F⊆[n] ⁣:∣F∣+∣F∩[ℓ−1]∣≥m+1}\{F\subseteq[n]\colon |F|+|F\cap[\ell-1]|\ge m+1\}. Completeness conjecture. For every nn and ss with n=sm+c=s(m+1)−ℓn=sm+c=s(m+1)-\ell,

e(n,s)=max⁡{∣H0(m,s,ℓ)∣,∣H1(m,s,ℓ)∣,…,∣Hm(m,s,ℓ)∣,∣P(m,s,ℓ)∣}.e(n,s)=\max\left\{|\mathcal H^0(m,s,\ell)|,|\mathcal H^1(m,s,\ell)|,\ldots,|\mathcal H^m(m,s,\ell)|,|\mathcal P(m,s,\ell)|\right\}.

Moreover, every extremal family is isomorphic to one of the candidates attaining this maximum. The conjecture proposes that these known weighted constructions form a complete list of extremal families; the source does not give a resolution.

References

Primary source

Cheng Chi and Yan Wang, “Extremal Families for the Erdős–Kleitman Problem: The Missing Constructions”, arXiv:2607.25611 (2026).

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