Tracially amenable actions and purely infinite crossed products
We introduce the notion of tracial amenability for actions of discrete groups on unital, tracial C$^*$-algebras, as a weakening of amenability where all the relevant approximations are done in the uniform trace norm. We characterize tracial amenability with various equivalent conditions, including t...
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Zusammenfassung: | We introduce the notion of tracial amenability for actions of discrete groups
on unital, tracial C$^*$-algebras, as a weakening of amenability where all the
relevant approximations are done in the uniform trace norm. We characterize
tracial amenability with various equivalent conditions, including topological
amenability of the induced action on the trace space. Our main result concerns
the structure of crossed products: for groups containing the free group $F_2$,
we show that outer, tracially amenable actions on simple, unital,
$\mathcal{Z}$-stable C$^*$-algebras always have purely infinite crossed
products. Finally, we give concrete examples of tracially amenable actions of
free groups on simple, unital AF-algebras. |
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DOI: | 10.48550/arxiv.2211.16872 |