Quantum metrics from length functions on étale groupoids

Fuente: arXiv
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Auteur principal: Austad, Are
Format: Preprint
Publié: 2026
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author Austad, Are
author_facet Austad, Are
contents We show how to construct a compact quantum metric space from a proper continuous length function on an étale groupoid with compact unit space, where the unit space additionally has the structure of a compact metric space. Using compactly supported Fourier multipliers on the reduced groupoid $C^*$-algebra we provide a sufficient condition for verifying when we obtain a compact quantum metric space in this manner. The condition is sometimes also necessary, and is new even in the case of length functions on discrete groups. Lastly, we show that any AF groupoid with compact unit space can be equipped with a length function from which we obtain a compact quantum metric space, thereby providing a groupoid approach to understanding the quantum metric geometry of unital AF algebras.
format Preprint
id arxiv_https___arxiv_org_abs_2602_20032
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Quantum metrics from length functions on étale groupoids
Austad, Are
Operator Algebras
Functional Analysis
58B34, 22A22, 46L87
We show how to construct a compact quantum metric space from a proper continuous length function on an étale groupoid with compact unit space, where the unit space additionally has the structure of a compact metric space. Using compactly supported Fourier multipliers on the reduced groupoid $C^*$-algebra we provide a sufficient condition for verifying when we obtain a compact quantum metric space in this manner. The condition is sometimes also necessary, and is new even in the case of length functions on discrete groups. Lastly, we show that any AF groupoid with compact unit space can be equipped with a length function from which we obtain a compact quantum metric space, thereby providing a groupoid approach to understanding the quantum metric geometry of unital AF algebras.
title Quantum metrics from length functions on étale groupoids
topic Operator Algebras
Functional Analysis
58B34, 22A22, 46L87
url https://arxiv.org/abs/2602.20032