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Amenability and Covariant Injectivity of Locally Compact Quantum Groups II

Published online by Cambridge University Press:  20 November 2018

Jason Crann*
Affiliation:
School of Mathematics and Statistics, Carleton University, Ottawa, ON, Canada KlS 5B6 e-mail: jason.crann@carleton.ca
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Abstract

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Building on our previous work, we study the non-relative homology of quantum group convolution algebras. Our main result establishes the equivalence of amenability of a locally compact quantum group $\mathbb{G}$ and 1-injectivity of ${{L}^{\infty }}\left( \widehat{\mathbb{G}} \right)$ as an operator ${{L}^{1}}\left( \widehat{\mathbb{G}} \right)$-module. In particular, a locally compact group $G$ is amenable if and only if its group von Neumann algebra $\text{VN}\left( G \right)$ is 1-injective as an operator module over the Fourier algebra $A\left( G \right)$. As an application, we provide a decomposability result for completely bounded ${{L}^{1}}\left( \widehat{\mathbb{G}} \right)$-module maps on ${{L}^{\infty }}\left( \widehat{\mathbb{G}} \right)$, and give a simplified proof that amenable discrete quantum groups have co-amenable compact duals, which avoids the use of modular theory and the Powers-Størmer inequality, suggesting that our homological techniques may yield a new approach to the open problem of duality between amenability and co-amenability.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2017

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