The Imprimitivity Fell Bundle

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1. Verfasser: Duwenig, Anna
Format: Preprint
Veröffentlicht: 2023
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author Duwenig, Anna
author_facet Duwenig, Anna
contents Given a full right-Hilbert C*-module $\mathbf{X}$ over a C*-algebra $A$, the set $\mathbb{K}_{A}(\mathbf{X})$ of $A$-compact operators on $\mathbf{X}$ is the (up to isomorphism) unique C*-algebra that is strongly Morita equivalent to the coefficient algebra $A$ via $\mathbf{X}$. As bimodule, $\mathbb{K}_{A}(\mathbf{X})$ can also be thought of as the balanced tensor product $\mathbf{X}\otimes_{A} \mathbf{X}^{\mathrm{op}}$, and so the latter naturally becomes a C*-algebra. We generalize both of these facts to the world of Fell bundles over groupoids: Suppose $\mathscr{B}$ is a Fell bundle over a groupoid $\mathcal{H}$ and $\mathscr{M}$ an upper semi-continuous Banach bundle over a principal right $\mathcal{H}$-space $X$. If $\mathscr{M}$ carries a right-action of $\mathscr{B}$ and a sufficiently nice $\mathscr{B}$-valued inner product, then its imprimitivity Fell bundle $\mathbb{K}_{\mathscr{B}}(\mathscr{M})=\mathscr{M}\otimes_{\mathscr{B}} \mathscr{M}^{\mathrm{op}}$ is a Fell bundle over the imprimitivity groupoid of $X$, and it is the unique Fell bundle that is equivalent to $\mathscr{B}$ via $\mathscr{M}$. We show that $\mathbb{K}_{\mathscr{B}}(\mathscr{M})$ generalizes the 'higher order' compact operators of Abadie and Ferraro in the case of saturated bundles over groups, and that the theorem recovers results such as Kumjian's Stabilization trick.
format Preprint
id arxiv_https___arxiv_org_abs_2311_15021
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle The Imprimitivity Fell Bundle
Duwenig, Anna
Operator Algebras
46L55, 46L05, 22A22
Given a full right-Hilbert C*-module $\mathbf{X}$ over a C*-algebra $A$, the set $\mathbb{K}_{A}(\mathbf{X})$ of $A$-compact operators on $\mathbf{X}$ is the (up to isomorphism) unique C*-algebra that is strongly Morita equivalent to the coefficient algebra $A$ via $\mathbf{X}$. As bimodule, $\mathbb{K}_{A}(\mathbf{X})$ can also be thought of as the balanced tensor product $\mathbf{X}\otimes_{A} \mathbf{X}^{\mathrm{op}}$, and so the latter naturally becomes a C*-algebra. We generalize both of these facts to the world of Fell bundles over groupoids: Suppose $\mathscr{B}$ is a Fell bundle over a groupoid $\mathcal{H}$ and $\mathscr{M}$ an upper semi-continuous Banach bundle over a principal right $\mathcal{H}$-space $X$. If $\mathscr{M}$ carries a right-action of $\mathscr{B}$ and a sufficiently nice $\mathscr{B}$-valued inner product, then its imprimitivity Fell bundle $\mathbb{K}_{\mathscr{B}}(\mathscr{M})=\mathscr{M}\otimes_{\mathscr{B}} \mathscr{M}^{\mathrm{op}}$ is a Fell bundle over the imprimitivity groupoid of $X$, and it is the unique Fell bundle that is equivalent to $\mathscr{B}$ via $\mathscr{M}$. We show that $\mathbb{K}_{\mathscr{B}}(\mathscr{M})$ generalizes the 'higher order' compact operators of Abadie and Ferraro in the case of saturated bundles over groups, and that the theorem recovers results such as Kumjian's Stabilization trick.
title The Imprimitivity Fell Bundle
topic Operator Algebras
46L55, 46L05, 22A22
url https://arxiv.org/abs/2311.15021