Supersaturation conjecture for odd-town families

Let [n][n] be an nn-element ground set, and let [?][?] be a collection of odd-sized subsets of it. Write peratornameop[?]([?])peratorname{op}[?]([?]) for the number of distinct pairs of sets in [?][?] having odd-sized intersection.

Odd-town supersaturation conjecture. Let n1n\geq 1 and fix 1sn1\leq s\leq n. If [?][?] is a collection of odd-sized subsets of an nn-element set with [?]n+s|[?]|\geq n+s, then

op(A)3s.\operatorname{op}(\mathcal{A})\geq 3s.

This extends the proved case s=1s=1, for which every odd-sized family of size at least n+1n+1 has at least three odd-intersection pairs; the conjecture predicts the extremality of the construction obtained by adjoining ss triples from vertex-disjoint copies of K4(3)K_4^{(3)}.

Sources & referencesView supporting material

Primary source

Jason O'Neill, “A short note on supersaturation for oddtown and eventown”, arXiv:2109.09925 (2022).

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