English

Properties of a curve whose convex hull covers a given convex body

Metric Geometry 2022-10-04 v1

Abstract

In this note, we prove the following inequality for the norm of a convex body KK in Rn\mathbb{R}^n, n2n\geq 2: N(K)πn122Γ(n+12)length(γ)+πn21Γ(n2)diam(K)N(K) \leq \frac{\pi^{\frac{n-1}{2}}}{2 \Gamma \left(\frac{n+1}{2}\right)}\cdot \operatorname{length} (\gamma) + \frac{\pi^{\frac{n}{2}-1}}{\Gamma \left(\frac{n}{2}\right)} \cdot \operatorname{diam}(K), where diam(K)\operatorname{diam}(K) is the diameter of KK, γ\gamma is any curve in Rn\mathbb{R}^n whose convex hull covers KK, and Γ\Gamma is the gamma function. If in addition KK has constant width Θ\Theta, then we get the inequality length(γ)2(π1)Γ(n+12)πΓ(n2)Θ2(π1)n12πΘ\operatorname{length} (\gamma) \geq \frac{2(\pi-1)\Gamma \left(\frac{n+1}{2}\right)}{\sqrt{\pi}\,\Gamma \left(\frac{n}{2}\right)}\cdot \Theta \geq 2(\pi-1) \cdot \sqrt{\frac{n-1}{2\pi}}\cdot \Theta. In addition, we pose several unsolved problems.

Keywords

Cite

@article{arxiv.2109.12830,
  title  = {Properties of a curve whose convex hull covers a given convex body},
  author = {Yurii Nikonorov},
  journal= {arXiv preprint arXiv:2109.12830},
  year   = {2022}
}

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7 pages