Gluing topological graph C*-algebras

Fuente: arXiv
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Hauptverfasser: Gothe, Atul, Quigg, John, Tobolski, Mariusz
Format: Preprint
Veröffentlicht: 2025
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author Gothe, Atul
Quigg, John
Tobolski, Mariusz
author_facet Gothe, Atul
Quigg, John
Tobolski, Mariusz
contents We introduce regular closed subgraphs of Katsura's topological graphs and use them to generalize the notion of an adjunction space from topology. Our construction attaches a topological graph onto another via a regular factor map. We prove that under suitable assumptions the C*-algebra of the adjunction graph is a pullback of the C*-algebras of the topological graphs being glued. Our results generalize certain pushout-to-pullback theorems proved in the context of discrete directed graphs. Our theorem applied to homeomorphism C*-algebras recovers a special case of the well-known result stating that pullbacks of $\mathbb{Z}$-C*-algebras induce pullbacks of the respective crossed product C*-algebras. Furthermore, we show that the C*-algebras of odd-dimensional quantum balls of Hong and Szymański (which are known not to be graph C*-algebras) are topological graph C*-algebras and we recover the pullback structure of C*-algebras of odd-dimensional quantum spheres by gluing the topological graphs associated to the C*-algebras of the corresponding odd-dimensional quantum balls.
format Preprint
id arxiv_https___arxiv_org_abs_2506_11592
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Gluing topological graph C*-algebras
Gothe, Atul
Quigg, John
Tobolski, Mariusz
Operator Algebras
46L05, 46L55, 46L85
We introduce regular closed subgraphs of Katsura's topological graphs and use them to generalize the notion of an adjunction space from topology. Our construction attaches a topological graph onto another via a regular factor map. We prove that under suitable assumptions the C*-algebra of the adjunction graph is a pullback of the C*-algebras of the topological graphs being glued. Our results generalize certain pushout-to-pullback theorems proved in the context of discrete directed graphs. Our theorem applied to homeomorphism C*-algebras recovers a special case of the well-known result stating that pullbacks of $\mathbb{Z}$-C*-algebras induce pullbacks of the respective crossed product C*-algebras. Furthermore, we show that the C*-algebras of odd-dimensional quantum balls of Hong and Szymański (which are known not to be graph C*-algebras) are topological graph C*-algebras and we recover the pullback structure of C*-algebras of odd-dimensional quantum spheres by gluing the topological graphs associated to the C*-algebras of the corresponding odd-dimensional quantum balls.
title Gluing topological graph C*-algebras
topic Operator Algebras
46L05, 46L55, 46L85
url https://arxiv.org/abs/2506.11592