Piercing intersecting convex sets

Assume two finite families A and B of convex sets in R 3 have the property that A ∩ B ≠ ∅ for every A ∈ A and B ∈ B . Is there a constant γ > 0 (independent of A and B ) such that there is a line intersecting γ | A | sets in A or γ | B | sets in B ? This is an intriguing Helly-type question from a paper by Martínez, Roldan and Rubin. We confirm this in the special case when all sets in A lie in parallel planes and all sets in B lie in parallel planes; in fact, one of the two families has a transversal by a single line.

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Publication Details

Journal
Linear Algebra and its Applications
Published
2025-02-05
DOI
https://doi.org/10.1016/j.laa.2025.02.007
Primary Topic
Computational Geometry and Mesh Generation
Type
article
Field-Weighted Citation Impact
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article

Piercing intersecting convex sets

Imre Bárány, Travis Dillon, Dániel Varga, Dömötör Pálvölgyi
Linear Algebra and its Applications
Computational Geometry and Mesh Generation
article

Piercing intersecting convex sets

Imre Bárány, Travis Dillon, Dániel Varga, Dömötör Pálvölgyi
article en

Abstract

Assume two finite families A and B of convex sets in R 3 have the property that A ∩ B ≠ ∅ for every A ∈ A and B ∈ B . Is there a constant γ > 0 (independent of A and B ) such that there is a line intersecting γ | A | sets in A or γ | B | sets in B ? This is an intriguing Helly-type question from a paper by Martínez, Roldan and Rubin. We confirm this in the special case when all sets in A lie in parallel planes and all sets in B lie in parallel planes; in fact, one of the two families has a transversal by a single line.

Linear Algebra and its ApplicationsVol. 710
Eötvös Loránd University (HU), HUN-REN Alfréd Rényi Institute of Mathematics (HU), University College London (GB), Massachusetts Institute of Technology (US)
Openalex Percentile: Top 97%
Computational Geometry and Mesh Generation
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