From Group Operations to Geometric Structures: Amalgamations, HNN-Extensions, and Twisting in Coset Geometries

Fuente: arXiv
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Autores principales: Piedade, Claudio Alexandre, Tranchida, Philippe
Formato: Preprint
Publicado: 2025
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author Piedade, Claudio Alexandre
Tranchida, Philippe
author_facet Piedade, Claudio Alexandre
Tranchida, Philippe
contents Coset incidence geometries, introduced by Jacques Tits, provide a versatile framework for studying the interplay between group theory and geometry. In this article, we build upon that idea by extending classical group-theoretic constructions (amalgamated products, HNN-extensions, semi-direct products, and twisting) to the setting of coset geometries. This gives a general way to glue together incidence geometries in various ways. This provides a general framework for combining or gluing incidence geometries in different ways while preserving essential properties such as flag-transitivity and residual connectedness. Using these techniques, we analyze families of Shephard groups, which generalize both Coxeter and Artin-Tits groups, and their associated simplicial complexes. Our results also point to the existence of a Bass-Serre theory for coset geometries and of a fundamental geometry of a graph of coset geometries.
format Preprint
id arxiv_https___arxiv_org_abs_2505_24662
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle From Group Operations to Geometric Structures: Amalgamations, HNN-Extensions, and Twisting in Coset Geometries
Piedade, Claudio Alexandre
Tranchida, Philippe
Group Theory
Combinatorics
Geometric Topology
20E06, 51E30, 20F55, 20F36
Coset incidence geometries, introduced by Jacques Tits, provide a versatile framework for studying the interplay between group theory and geometry. In this article, we build upon that idea by extending classical group-theoretic constructions (amalgamated products, HNN-extensions, semi-direct products, and twisting) to the setting of coset geometries. This gives a general way to glue together incidence geometries in various ways. This provides a general framework for combining or gluing incidence geometries in different ways while preserving essential properties such as flag-transitivity and residual connectedness. Using these techniques, we analyze families of Shephard groups, which generalize both Coxeter and Artin-Tits groups, and their associated simplicial complexes. Our results also point to the existence of a Bass-Serre theory for coset geometries and of a fundamental geometry of a graph of coset geometries.
title From Group Operations to Geometric Structures: Amalgamations, HNN-Extensions, and Twisting in Coset Geometries
topic Group Theory
Combinatorics
Geometric Topology
20E06, 51E30, 20F55, 20F36
url https://arxiv.org/abs/2505.24662