Counting normals to closed curves in $\mathbb{R}^3$
Differential Geometry
2026-03-02 v2
Abstract
We prove the following results: (1) For every generic closed smooth curve in there is a point with at least emanating normals to the curve. (2) For every generic closed piecewise linear curve in there is a point with at least emanating normals to the curve. If the curve is knotted, there is a point with at least emanating normals. The proof is based on the Morse theory for the squared distance function and self intersections of the focal surface.
Cite
@article{arxiv.2602.06645,
title = {Counting normals to closed curves in $\mathbb{R}^3$},
author = {Gaiane Panina and Dirk Siersma},
journal= {arXiv preprint arXiv:2602.06645},
year = {2026}
}