Strong cross-star conjecture for hereditary families

Let 1tr1\leq t\leq r, let S[r]\emptyset\neq S\subseteq [r], and let H\mathcal{H} be a hereditary family with covering number μ(H)(t+1)(rt+1)\mu(\mathcal{H})\geq (t+1)(r-t+1). Write H(S)\mathcal{H}^{(S)} for the subfamily consisting of members whose sizes lie in SS, and use the strong cross-tt-star property as in the paper. Hereditary-family cross-star conjecture. The pair

(H(S),H(S))(\mathcal{H}^{(S)},\mathcal{H}^{(S)})

has the strong cross-tt-star property. The paper additionally conjectures that the pair has the extrastrong cross-tt-star property when μ(H)>(t+1)(rt+1)\mu(\mathcal{H})>(t+1)(r-t+1).

Sources & referencesView supporting material

Primary source

Peter Borg, “The maximum product of sizes of cross-intersecting families”, arXiv:1605.08752 (2016).

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