Cross-intersection conjecture for levels of hereditary families

Let H\mathcal{H} be a hereditary family, let H(r)\mathcal{H}^{(r)} be its rr-th level, and write μ(H)\mu(\mathcal{H}) for the minimum size of a base. Two subfamilies are cross-intersecting if every member of one intersects every member of the other.

Cross-intersection conjecture for hereditary families. If μ(H)2r\mu(\mathcal{H})\geq 2r and A,BH(r)\mathcal{A},\mathcal{B}\subseteq\mathcal{H}^{(r)} are cross-intersecting, then

A+BH(r).|\mathcal{A}|+|\mathcal{B}|\leq |\mathcal{H}^{(r)}|.

The source explicitly calls this a generalization of Kamat's conjecture and does not report a resolution.

Sources & referencesView supporting material

Primary source

Peter Borg, “Cross-intersecting subfamilies of levels of hereditary families”, arXiv:1805.05241 (2018).

Additional references

2 papers in this index state this conjecture (2010–2018). The statement above is taken from the most recent of them; the others are arXiv:1010.0947.

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