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Consider a coaction $\delta$ of a locally compact group $G$ on a \cstar algebra $A$, and a closed normal subgroup $N$ of $G$. We prove, following results of Echterhoff for abelian $G$, that Mansfield's imprimitivity between…

funct-an · Mathematics 2008-02-03 S. Kaliszewski , John Quigg , Iain Raeburn

I combine recent results in the structure theory of nuclear C*-algebras and in topological dynamics to classify certain types of crossed products in terms of their Elliott invariants. In particular, transformation group C*-algebras…

Operator Algebras · Mathematics 2015-04-08 Wilhelm Winter

The paper presents a construction of the crossed product of a C*-algebra by an endomorphism generated by partial isometry

Operator Algebras · Mathematics 2007-05-23 A. B. Antonevich , V. I. Bakhtin , A. V. Lebedev

We introduce an appropriate notion of inner amenability for locally compact quantum groups, study its basic properties, related notions, and examples arising from the bicrossed product construction. We relate these notions to homological…

Operator Algebras · Mathematics 2018-05-24 Jason Crann

Crossed product algebras are fundamental in the study of C*-algebras, traditionally under the assumption of continuity of group actions. Recent work by Grundling and Neeb introduced the crossed product host, an analog of the crossed product…

Operator Algebras · Mathematics 2025-05-13 Yusuke Nakae

We consider an extendible endomorphism $\alpha$ of a $C^*$-algebra $A$. We associate to it a canonical $C^*$-dynamical system $(B,\beta)$ that extends $(A,\alpha)$ and is `reversible' in the sense that the endomorphism $\beta$ admits a…

Operator Algebras · Mathematics 2015-04-29 B. K. Kwasniewski

We interpret several constructions with C*-algebras as colimits in the bicategory of correspondences. This includes crossed products for actions of groups and crossed modules, Cuntz-Pimsner algebras of proper product systems, direct sums…

Operator Algebras · Mathematics 2019-04-30 Suliman Albandik , Ralf Meyer

We give a survey of recent classification results for crossed product von Neumann algebras arising from measure preserving group actions on probability spaces. This includes II_1 factors with uncountable fundamental groups and the…

Operator Algebras · Mathematics 2010-08-24 Stefaan Vaes

Let $\alpha: G\curvearrowright X$ be a minimal free continuous action of an infinite countable amenable group on an infinite compact metrizable space. In this paper, under the hypothesis that the invariant ergodic probability Borel measure…

Dynamical Systems · Mathematics 2018-06-29 Xin Ma

We examine crossed product C*-algebras associated with non-minimal free actions of countably infinite discrete abelian groups on the circle, extending the work of Putnam, Schmidt, and Skau. We obtain a large class of unital separable…

Operator Algebras · Mathematics 2026-04-21 Jamie Bell

We consider the ideal structure of reduced crossed products over discrete groups. First, we completely characterize primality for reduced crossed products. Second, we characterize the ideal intersection property for reduced crossed products…

Operator Algebras · Mathematics 2025-04-22 Matthew Kennedy , Larissa Kroell , Camila F. Sehnem

As is well known, the equivalence between amenability of a locally compact group $G$ and injectivity of its von Neumann algebra $\mathcal{L}(G)$ does not hold in general beyond inner amenable groups. In this paper, we show that the…

Operator Algebras · Mathematics 2014-11-04 Jason Crann , Matthias Neufang

We give a means of estimating the equivariant compression of a group G in terms of properties of open subgroups G_i whose direct limit is G. Quantifying a result by S.R. Gal, we also study the behaviour of the equivariant compression under…

Group Theory · Mathematics 2016-02-09 Chris Cave , Dennis Dreesen

We study the exactness of the reduced crossed product of a semigroup dynamical system and the reduced $C^{*}$-algebra of a product system. We show that for a semigroup dynamical system $(A, P,\alpha)$, under reasonable hypotheses (e.g., $P$…

Operator Algebras · Mathematics 2026-04-07 Md Amir Hossain , S. Sundar

We compare the algebras of the quantum automorphism group of finite-dimensional C$^\ast$-algebra $B$, which includes the quantum permutation group $S_N^+$, where $N = \dim B$. We show that matrix amplification and crossed products by…

Operator Algebras · Mathematics 2023-02-22 Michael Brannan , Floris Elzinga , Samuel J. Harris , Makoto Yamashita

We study regular irreducible inclusions $B\subset A$ of simple unital $C^*$-algebras admitting a conditional expectation. We introduce a generalized notion of quasi-basis extending Watatani's framework and show that such inclusions admit a…

Operator Algebras · Mathematics 2026-05-13 Keshab Chandra Bakshi , Silambarasan C , Biplab Pal

We show that when a co-involutive Hopf C*-algebra $S$ coacts via $\delta$ on a C*-algebra $A$, there exists a full crossed product $A\times_\delta S$, with universal properties analogous to those of full crossed products by locally compact…

Operator Algebras · Mathematics 2016-09-07 May M. Nilsen

Recent work has highlighted the importance of crossed products in correctly elucidating the operator algebraic approach to quantum field theories. In the gravitational context, the crossed product simultaneously promotes von Neumann…

High Energy Physics - Theory · Physics 2024-06-28 Marc S. Klinger , Robert G. Leigh

Let $M$ be a finite von Neumann algebra with the Haagerup property, and let $G$ be a compact group that acts continuously on $M$ and that preserves some finite trace $\tau$. We prove that if $\Gamma$ is a countable subgroup of $G$ which has…

Operator Algebras · Mathematics 2007-05-23 Paul Jolissaint

We study w*-semicrossed products over actions of the free semigroup and the free abelian semigroup on (possibly non-selfadjoint) w*-closed algebras. We show that they are reflexive when the dynamics are implemented by uniformly bounded…

Operator Algebras · Mathematics 2020-01-24 Robert T. Bickerton , Evgenios T. A. Kakariadis