Doubly Commuting Semigroups of Isometries

Fuente: arXiv
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Autori principali: Namitha, C. H., Sundar, S., Veerabathiran, Shankar
Natura: Preprint
Pubblicazione: 2025
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author Namitha, C. H.
Sundar, S.
Veerabathiran, Shankar
author_facet Namitha, C. H.
Sundar, S.
Veerabathiran, Shankar
contents In this paper, we discuss the structure of doubly commuting semigroups of isometries. We record a new proof of Cooper's theorem in the Hilbert module setting. We discuss the Fell topology on the set of equivalence classes of irreducible, doubly commuting isometric representations of $\mathbb{R}_{+}^{d}$. We show that if $d$ is finite, the topology is $T_0$. We indicate the pathologies that occur when $d=\infty$. In particular, we show that Wold decomposition fails for isometric representations of $\mathbb{R}_{+}^{\infty}$ and prove that the Fell topology on the set of equivalence classes of irreducible, doubly commuting isometric representations of $\mathbb{R}_{+}^{\infty}$ is not $T_0$
format Preprint
id arxiv_https___arxiv_org_abs_2509_00409
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Doubly Commuting Semigroups of Isometries
Namitha, C. H.
Sundar, S.
Veerabathiran, Shankar
Operator Algebras
Functional Analysis
In this paper, we discuss the structure of doubly commuting semigroups of isometries. We record a new proof of Cooper's theorem in the Hilbert module setting. We discuss the Fell topology on the set of equivalence classes of irreducible, doubly commuting isometric representations of $\mathbb{R}_{+}^{d}$. We show that if $d$ is finite, the topology is $T_0$. We indicate the pathologies that occur when $d=\infty$. In particular, we show that Wold decomposition fails for isometric representations of $\mathbb{R}_{+}^{\infty}$ and prove that the Fell topology on the set of equivalence classes of irreducible, doubly commuting isometric representations of $\mathbb{R}_{+}^{\infty}$ is not $T_0$
title Doubly Commuting Semigroups of Isometries
topic Operator Algebras
Functional Analysis
url https://arxiv.org/abs/2509.00409