Helly-type intersection conjecture for projection-direction sets

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Let F\mathcal{F} be an intersecting family of convex sets in R3\mathbb{R}^3. For each triple T={F1,F2,F3}∈(F3)T=\{F_1,F_2,F_3\}\in {\mathcal{F}\choose 3}, let DT⊂S2D_T\subset S^2 consist of the directions a\mathbf{a} for which the orthogonal projections of F1,F2,F3F_1,F_2,F_3 onto the plane x⋅a=0x\cdot\mathbf{a}=0 have a common point. Intersection conjecture for the sets DTD_T. For any three triples T1,T2,T3T_1,T_2,T_3, one has

DT1∩DT2∩DT3≠∅.D_{T_1}\cap D_{T_2}\cap D_{T_3}\neq\emptyset.

Together with the surrounding proposed lemmas, this would help prove that a line pierces c∣F∣c|\mathcal{F}| members of F\mathcal{F} for some constant cc. The supplied text does not state whether the assertion is resolved.

References

Primary source

Daniel McGinnis and Shira Zerbib, “Line transversals in families of connected sets the plane”, arXiv:2103.05565 (2021).

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