English

Each generic polytope in $\mathbb{R}^3$ has a point with ten normals to the boundary

Metric Geometry 2025-09-11 v4

Abstract

It is conjectured since long that each smooth convex body PRn\mathbf{P}\subset \mathbb{R}^n has a point in its interior which belongs to at least 2n2n normals from different points on the boundary of P\mathbf{P}. The conjecture is proven for n=2,3,4n=2,3,4. We treat the same problem for convex polytopes in R3\mathbb{R}^3 and prove that each generic polytope has a point in its interior with at least 1010 normals to the boundary. This bound is exact: there exists a tetrahedron with no more than 1010 normals emanating from a point in its interior. The proof is based on piecewise linear analog of Morse theory, analysis of bifurcations, and some combinatorial tricks.

Keywords

Cite

@article{arxiv.2411.12745,
  title  = {Each generic polytope in $\mathbb{R}^3$ has a point with ten normals to the boundary},
  author = {Ivan Nasonov and Gaiane Panina},
  journal= {arXiv preprint arXiv:2411.12745},
  year   = {2025}
}

Comments

arXiv admin note: text overlap with arXiv:2406.01773 v1 treats simple polytopes only