English

Topological Drawings meet Classical Theorems from Convex Geometry

Combinatorics 2024-07-30 v4 Computational Geometry Discrete Mathematics

Abstract

In this article we discuss classical theorems from Convex Geometry in the context of topological drawings and beyond. In a simple topological drawing of the complete graph KnK_n, any two edges share at most one point: either a common vertex or a point where they cross. Triangles of simple topological drawings can be viewed as convex sets. This gives a link to convex geometry. As our main result, we present a generalization of Kirchberger's Theorem that is of purely combinatorial nature. It turned out that this classical theorem also applies to "generalized signotopes" - a combinatorial generalization of simple topological drawings, which we introduce and investigate in the course of this article. As indicated by the name they are a generalization of signotopes, a structure studied in the context of encodings for arrangements of pseudolines. We also present a family of simple topological drawings with arbitrarily large Helly number, and a new proof of a topological generalization of Carath\'{e}odory's Theorem in the plane and discuss further classical theorems from Convex Geometry in the context of simple topological drawings.

Keywords

Cite

@article{arxiv.2005.12568,
  title  = {Topological Drawings meet Classical Theorems from Convex Geometry},
  author = {Helena Bergold and Stefan Felsner and Manfred Scheucher and Felix Schröder and Raphael Steiner},
  journal= {arXiv preprint arXiv:2005.12568},
  year   = {2024}
}

Comments

A preliminary version appears in the Proceedings of the 28th International Symposium on Graph Drawing and Network Visualization (GD 2020). The reverse direction of Theorem 1 does not hold. The comment directly after the theorem is now corrected and a counterexample is presented

R2 v1 2026-06-23T15:48:47.119Z