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The Number of Holes in the Union of Translates of a Convex Set in Three Dimensions

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Abstract

We show that the union of n translates of a convex body in \(\mathbb {R}^3\) can have \(\varTheta (n^3)\) holes in the worst case, where a hole in a set X is a connected component of \(\mathbb {R}^3 \setminus X\). This refutes a 20-year-old conjecture. As a consequence, we also obtain improved lower bounds on the complexity of motion planning problems and of Voronoi diagrams with convex distance functions.

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Notes

  1. We say a path \(\pi \) is convex in a direction u if the orthogonal projection of \(\pi \) onto \(u^\bot \) is injective and the set \(\pi + \mathbb {R}^+ u\) is convex.

  2. In other words, the i-dimensional simplices of \(\Delta \) form a basis of the vector space \({{\mathrm{\mathcal {C}}}}_i(\Delta )\), which consists of formal sums of i-simplices, each simplex being assigned a real coefficient.

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Acknowledgments

B. Aronov supported by NSF Grants CCF-11-17336 and CCF-12-18791. O. Cheong and M. G. Dobbins supported by NRF Grant 2011-0030044 (SRC-GAIA) from the Government of Korea.

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Correspondence to Michael Gene Dobbins.

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Editor in Charge: János Pach

An extended abstract of this work was presented at the 32nd International Symposium on Computational Geometry [4].

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Aronov, B., Cheong, O., Dobbins, M.G. et al. The Number of Holes in the Union of Translates of a Convex Set in Three Dimensions. Discrete Comput Geom 57, 104–124 (2017). https://doi.org/10.1007/s00454-016-9820-4

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  • DOI: https://doi.org/10.1007/s00454-016-9820-4

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