Surface topology and incidence theorems over division rings

Fuente: arXiv
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Main Author: Izosimov, Anton
Format: Preprint
Published: 2026
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author Izosimov, Anton
author_facet Izosimov, Anton
contents Incidence theorems concern configurations of points, lines, and, more generally, higher-dimensional subspaces in projective space. Broadly speaking, such theorems fall into two classes: those that hold over an arbitrary division ring, such as Desargues' theorem, and those that hold only over fields, such as Pappus' theorem. In this paper, we explain the topological origin of this distinction. To this end, we extend to the noncommutative setting the surface-graph approach to incidence theorems developed by Richter-Gebert, Fomin, and Pylyavskyy. We then show that theorems associated with graphs embedded on the sphere, such as Desargues' theorem, hold over any division ring, whereas theorems corresponding to graphs embedded on surfaces of positive genus, such as Pappus' theorem, typically hold if and only if the ground ring is a field. We also extend these results to the setting of arbitrary rings, not necessarily admitting division.
format Preprint
id arxiv_https___arxiv_org_abs_2603_00288
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Surface topology and incidence theorems over division rings
Izosimov, Anton
Combinatorics
Geometric Topology
Metric Geometry
Rings and Algebras
Incidence theorems concern configurations of points, lines, and, more generally, higher-dimensional subspaces in projective space. Broadly speaking, such theorems fall into two classes: those that hold over an arbitrary division ring, such as Desargues' theorem, and those that hold only over fields, such as Pappus' theorem. In this paper, we explain the topological origin of this distinction. To this end, we extend to the noncommutative setting the surface-graph approach to incidence theorems developed by Richter-Gebert, Fomin, and Pylyavskyy. We then show that theorems associated with graphs embedded on the sphere, such as Desargues' theorem, hold over any division ring, whereas theorems corresponding to graphs embedded on surfaces of positive genus, such as Pappus' theorem, typically hold if and only if the ground ring is a field. We also extend these results to the setting of arbitrary rings, not necessarily admitting division.
title Surface topology and incidence theorems over division rings
topic Combinatorics
Geometric Topology
Metric Geometry
Rings and Algebras
url https://arxiv.org/abs/2603.00288