Fractional line-transversal conjecture for pairwise intersecting convex sets in three dimensions

Let K\mathcal{K} be a finite family of nn convex sets in R3\mathbb{R}^3, and suppose that every two members K1,K2KK_1,K_2\in\mathcal{K} satisfy K1K2K_1\cap K_2\neq\emptyset. Fractional line-transversal conjecture. There is an absolute constant c>0c>0 such that a line crosses cncn members of K\mathcal{K}. This is the one-colored variant highlighted by Bárány and Kalai; the source presents it as a subsequent open problem related to the 2-colored conjecture.

Sources & referencesView supporting material

Primary source

Natan Rubin, “On Lines Crossing Pairwise Intersecting Convex Sets in Three Dimensions”, arXiv:2601.17913 (2026).

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