O'Neill and Versträete's uniform extremal-family conjecture

Let ([n]k)\binom{[n]}k be the family of kk-element subsets of [n][n]. For r2r\geq2, let BDr(n,k){\rm BD}_r(n,k) and Fr(n,k,r1)\mathcal F_r(n,k,r-1) be the two specified non-trivial rr-wise intersecting kk-uniform families. A family is extremal if it has maximum size among non-trivial rr-wise intersecting subfamilies of ([n]k)\binom{[n]}k.

O'Neill and Versträete's conjecture. Let k>r2k>r\geq2 and nkr(r1)n\geq kr(r-1). Then the unique extremal non-trivial rr-wise intersecting families in ([n]k)\binom{[n]}k are BDr(n,k){\rm BD}_r(n,k) and Fr(n,k,r1)\mathcal F_r(n,k,r-1), up to isomorphism.

This is the proposed uniform analogue of the extremal result for product-measure families. The supplied text gives no resolution of the conjecture.

Sources & referencesView supporting material

Primary source

Norihide Tokushige, “The maximum measure of non-trivial 3-wise intersecting families”, arXiv:2203.17158 (2023).

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