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TENSOR-PRODUCT COACTION FUNCTORS

Part of: Selfadjoint operator algebras Methods of category theory in functional analysis

Published online by Cambridge University Press:  24 March 2020

S. KALISZEWSKI Open the ORCID record for S. KALISZEWSKI [Opens in a new window] ,
MAGNUS B. LANDSTAD  and
JOHN QUIGG
S. KALISZEWSKI
Affiliation:
School of Mathematical & Statistical Sciences, Arizona State University, Tempe, AZ 85287, USA e-mail: kaliszewski@asu.edu
MAGNUS B. LANDSTAD
Affiliation:
Department of Mathematical Sciences, Norwegian University of Science & Technology, NO-7491 Trondheim, Norway e-mail: magnus.landstad@ntnu.no
JOHN QUIGG
Affiliation:
School of Mathematical & Statistical Sciences, Arizona State University, Tempe, AZ 85287, USA e-mail: quigg@asu.edu
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Abstract

Recent work by Baum et al. [‘Expanders, exact crossed products, and the Baum–Connes conjecture’, Ann. K-Theory 1(2) (2016), 155–208], further developed by Buss et al. [‘Exotic crossed products and the Baum–Connes conjecture’, J. reine angew. Math. 740 (2018), 111–159], introduced a crossed-product functor that involves tensoring an action with a fixed action $(C,\unicode[STIX]{x1D6FE})$, then forming the image inside the crossed product of the maximal-tensor-product action. For discrete groups, we give an analogue for coaction functors. We prove that composing our tensor-product coaction functor with the full crossed product of an action reproduces their tensor-crossed-product functor. We prove that every such tensor-product coaction functor is exact, and if $(C,\unicode[STIX]{x1D6FE})$ is the action by translation on $\ell ^{\infty }(G)$, we prove that the associated tensor-product coaction functor is minimal, thereby recovering the analogous result by the above authors. Finally, we discuss the connection with the $E$-ization functor we defined earlier, where $E$ is a large ideal of $B(G)$.

Keywords

crossed productactioncoactiontensor productFell bundle

MSC classification

Primary: 46L55: Noncommutative dynamical systems
Secondary: 46M15: Categories, functors
Type
Research Article
Information
Journal of the Australian Mathematical Society , Volume 112 , Issue 1 , February 2022 , pp. 52 - 67
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Copyright
© 2020 Australian Mathematical Publishing Association Inc.

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Footnotes

Communicated by L. O. Clark

Dedicated to the memory of J. M. G. Fell, 1923–2016

References

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