Conjecture on consecutive-layer extremal families avoiding a fixed poset

Let PP be a fixed finite poset, let e(P)e(P) be the largest integer kk such that the union of the kk middle layers of the Boolean lattice is PP-free, and let Lac(n,P)\operatorname{La}^c(n,P) be the maximum size of a PP-free family contained in e(P)+1e(P)+1 consecutive layers. If the limit exists, define

πc(P)=limnLac(n,P)(nn/2).\pi^c(P)=\lim_{n\to\infty}\frac{\operatorname{La}^c(n,P)}{\binom{n}{\lfloor n/2\rfloor}}.

Consecutive-layer conjecture. For any fixed poset PP,

πc(P)=e(P).\pi^c(P)=e(P).

This is presented as a weaker version of the general extremal-poset conjecture. The source highlights the diamond poset as an important unresolved case of the stronger conjecture.

Sources & referencesView supporting material

Primary source

Travis Johnston and Linyuan Lu, “Turan Problems on Non-uniform Hypergraphs”, arXiv:1301.1870 (2013).

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