Every finite group is represented by a finite incidence geometry

Fuente: arXiv
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Auteurs principaux: Ramos, Antonio Díaz, Molinier, Rémi, Viruel, Antonio
Format: Preprint
Publié: 2025
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author Ramos, Antonio Díaz
Molinier, Rémi
Viruel, Antonio
author_facet Ramos, Antonio Díaz
Molinier, Rémi
Viruel, Antonio
contents We investigate the relationship between finite groups and incidence geometries through their automorphism structures. Building upon classical results on the realizability of groups as automorphism groups of graphs, we develop a general framework to represent pairs of finite groups $(G, H)$, where $H \trianglelefteq G$, as pairs of correlation--automorphism groups of suitable incidence geometries. Specifically, we prove that for every such pair $(G, H)$, there exists a finite incidence geometry $Γ$ satisfying that the pair $(\operatorname{Aut}(Γ), \operatorname{Aut}_I(Γ))$ of correlation--automorphism groups of $Γ$ is isomorphic to $(G, H)$. Our construction proceeds in two main steps: first, we realize $(G, H)$ as the correlation and automorphism groups of an incidence system; then, we refine this system into a genuine incidence geometry preserving the same pair of automorphisms groups. We also provide explicit examples, including a family of geometries realizing $(S_n, A_n)$ for all $n \ge 2$.
format Preprint
id arxiv_https___arxiv_org_abs_2511_02410
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Every finite group is represented by a finite incidence geometry
Ramos, Antonio Díaz
Molinier, Rémi
Viruel, Antonio
Group Theory
Combinatorics
We investigate the relationship between finite groups and incidence geometries through their automorphism structures. Building upon classical results on the realizability of groups as automorphism groups of graphs, we develop a general framework to represent pairs of finite groups $(G, H)$, where $H \trianglelefteq G$, as pairs of correlation--automorphism groups of suitable incidence geometries. Specifically, we prove that for every such pair $(G, H)$, there exists a finite incidence geometry $Γ$ satisfying that the pair $(\operatorname{Aut}(Γ), \operatorname{Aut}_I(Γ))$ of correlation--automorphism groups of $Γ$ is isomorphic to $(G, H)$. Our construction proceeds in two main steps: first, we realize $(G, H)$ as the correlation and automorphism groups of an incidence system; then, we refine this system into a genuine incidence geometry preserving the same pair of automorphisms groups. We also provide explicit examples, including a family of geometries realizing $(S_n, A_n)$ for all $n \ge 2$.
title Every finite group is represented by a finite incidence geometry
topic Group Theory
Combinatorics
url https://arxiv.org/abs/2511.02410