$C(SO_q(4)/SO_q(2))$ as a Groupoid $C^*$-algebra

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Main Authors: Bhatt, Shreema Subhash, Deshpande, Vinay, Saurabh, Bipul
Format: Preprint
Published: 2026
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author Bhatt, Shreema Subhash
Deshpande, Vinay
Saurabh, Bipul
author_facet Bhatt, Shreema Subhash
Deshpande, Vinay
Saurabh, Bipul
contents In this paper, we prove that $C(SO_q(4)/SO_q(2))$ is isomorphic to the $C^*$-algebra of the tight groupoid $\mathcal{G}_{\mathrm{tight}}$ associated with the inverse semigroup generated by the standard generators of its classical limit $C(SO_0(4)/SO_0(2))$. We show that all four orbits of the unit space $\mathcal{G}_{\mathrm{tight}}^{(0)}$ under the natural action of $\mathcal{G}_{\mathrm{tight}}$ are locally closed, and that the associated isotropy groups are isomorphic to $\mathbb{Z}$. Consequently, every irreducible representation of $C^*(\mathcal{G}_{\mathrm{tight}})$ is induced from an irreducible representation of $C^*(\mathbb{Z})$, which are parametrized by $\mathbb{T}$. In this way, we obtain four families of irreducible representations parametrized by $\mathbb{T}$, and we explicitly construct their equivalence with the corresponding Soibelman irreducible representations of $C(SO_q(4)/SO_q(2))$.
format Preprint
id arxiv_https___arxiv_org_abs_2604_10047
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle $C(SO_q(4)/SO_q(2))$ as a Groupoid $C^*$-algebra
Bhatt, Shreema Subhash
Deshpande, Vinay
Saurabh, Bipul
Operator Algebras
22A22, 46L05, 46L67
In this paper, we prove that $C(SO_q(4)/SO_q(2))$ is isomorphic to the $C^*$-algebra of the tight groupoid $\mathcal{G}_{\mathrm{tight}}$ associated with the inverse semigroup generated by the standard generators of its classical limit $C(SO_0(4)/SO_0(2))$. We show that all four orbits of the unit space $\mathcal{G}_{\mathrm{tight}}^{(0)}$ under the natural action of $\mathcal{G}_{\mathrm{tight}}$ are locally closed, and that the associated isotropy groups are isomorphic to $\mathbb{Z}$. Consequently, every irreducible representation of $C^*(\mathcal{G}_{\mathrm{tight}})$ is induced from an irreducible representation of $C^*(\mathbb{Z})$, which are parametrized by $\mathbb{T}$. In this way, we obtain four families of irreducible representations parametrized by $\mathbb{T}$, and we explicitly construct their equivalence with the corresponding Soibelman irreducible representations of $C(SO_q(4)/SO_q(2))$.
title $C(SO_q(4)/SO_q(2))$ as a Groupoid $C^*$-algebra
topic Operator Algebras
22A22, 46L05, 46L67
url https://arxiv.org/abs/2604.10047