License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.SoCG.2020.62
URN: urn:nbn:de:0030-drops-122201
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Patáková, Zuzana ; Tancer, Martin ; Wagner, Uli

Barycentric Cuts Through a Convex Body

LIPIcs-SoCG-2020-62.pdf (0.7 MB)


Let K be a convex body in ℝⁿ (i.e., a compact convex set with nonempty interior). Given a point p in the interior of K, a hyperplane h passing through p is called barycentric if p is the barycenter of K ∩ h. In 1961, Grünbaum raised the question whether, for every K, there exists an interior point p through which there are at least n+1 distinct barycentric hyperplanes. Two years later, this was seemingly resolved affirmatively by showing that this is the case if p=p₀ is the point of maximal depth in K. However, while working on a related question, we noticed that one of the auxiliary claims in the proof is incorrect. Here, we provide a counterexample; this re-opens Grünbaum’s question.
It follows from known results that for n ≥ 2, there are always at least three distinct barycentric cuts through the point p₀ ∈ K of maximal depth. Using tools related to Morse theory we are able to improve this bound: four distinct barycentric cuts through p₀ are guaranteed if n ≥ 3.

BibTeX - Entry

  author =	{Zuzana Pat{\'a}kov{\'a} and Martin Tancer and Uli Wagner},
  title =	{{Barycentric Cuts Through a Convex Body}},
  booktitle =	{36th International Symposium on Computational Geometry (SoCG 2020)},
  pages =	{62:1--62:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-143-6},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{164},
  editor =	{Sergio Cabello and Danny Z. Chen},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{},
  URN =		{urn:nbn:de:0030-drops-122201},
  doi =		{10.4230/LIPIcs.SoCG.2020.62},
  annote =	{Keywords: convex body, barycenter, Tukey depth, smooth manifold, critical points}

Keywords: convex body, barycenter, Tukey depth, smooth manifold, critical points
Collection: 36th International Symposium on Computational Geometry (SoCG 2020)
Issue Date: 2020
Date of publication: 08.06.2020

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