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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

This work explores the geometrical/algebraic framework of Lie algebroids, with a specific focus on the decoupling and coupling phenomena within the bicocycle double cross product realization. The bicocycle double cross product theory serves…

Differential Geometry · Mathematics 2025-03-18 Begüm Ateşli , Oğul Esen , Serkan Sütlü

Quantum groupoids are a joint generalization of groupoids and quantum groups. We propose a definition of a compact quantum groupoid that is based on the theory of C*-algebras and Hilbert bimodules. The essential point is that whenever one…

Mathematical Physics · Physics 2007-05-23 N. P. Landsman

We extend the notion of Poincar\'e duality in KK-theory to the setting of quantum group actions. An important ingredient in our approach is the replacement of ordinary tensor products by braided tensor products. Along the way we discuss…

K-Theory and Homology · Mathematics 2009-11-16 Ryszard Nest , Christian Voigt

Given two associative algebras A, C and a linear space V together with some linear maps R_1, R_2, R_3, E satisfying some conditions, we define an associative algebra structure on A\otimes V\otimes C called a two-sided crossed product.…

Quantum Algebra · Mathematics 2024-10-22 Florin Panaite

For a quasitriangular C*-quantum group, we enrich the twisted tensor product constructed in the first part of this series to a monoidal structure on the category of its continuous coactions on C*-algebras. We define braided C*-quantum…

Operator Algebras · Mathematics 2024-06-25 Ralf Meyer , Sutanu Roy , Stanisław Lech Woronowicz

In this paper we analyse for a $G$-$C^{*}$-algebra $A$ to which extent one can calculate the $K$-theory of the reduced crossed product $K(A\rtimes_{r}G)$ from the $K$-theory spectrum $K(A)$ with the induced $G$-action. We also consider some…

Operator Algebras · Mathematics 2023-11-29 Ulrich Bunke

Given a finite dimensional C^*-Hopf algebra H and its dual H^ we construct the infinite crossed product A=... x H x H^ x H ... and study its superselection sectors in the framework of algebraic quantum field theory. A is the observable…

High Energy Physics - Theory · Physics 2009-10-28 Florian Nill , Kornel Szlachanyi

We show that for a locally compact group G there is a one-to-one correspondence between G-invariant weak*-closed subspaces E of the Fourier-Stieltjes algebra B(G) containing B_r(G) and quotients C*_E(G) of C*(G) which are intermediate…

Operator Algebras · Mathematics 2013-09-02 S. Kaliszewski , Magnus B. Landstad , John Quigg

We bound the nuclear dimension of crossed products associated to some partial actions of finite groups or $\mathbb{Z}$ on finite dimensional locally compact Hausdorff second countable spaces. Our results apply to globalizable partial…

Operator Algebras · Mathematics 2022-01-19 Shirly Geffen

The notion of quasicrossed product is introduced in the setting of G-graded quasialgebras, i.e., algebras endowed with a grading by a group G, satisfying a "quasiassociative" law. The equivalence between quasicrossed products and…

Rings and Algebras · Mathematics 2014-12-01 Helena Albuquerque , Elisabete Barreiro , José M. Sánchez-Delgado

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 introduce the concept of Rokhlin dimension for actions of residually compact groups on C*-algebras, which extends and unifies previous notions for actions of compact groups, residually finite groups and the reals. We then demonstrate…

Operator Algebras · Mathematics 2026-02-03 Xin Cao , Xiaochun Fang , Jianchao Wu

The well known "associativity property" of the crossed product by a semi-direct product of discrete groups is generalized into the context of discrete \emph{quantum} groups. This decomposition allows to define an appropriate triangulated…

Operator Algebras · Mathematics 2023-01-04 Rubén Martos

For $p \in [1, \infty),$ we define and study full and reduced crossed products of algebras of operators on $\sigma$-finite $L^p$ spaces by isometric actions of second countable locally compact groups. We give universal properties for both…

Functional Analysis · Mathematics 2013-09-26 N. Christopher Phillips

We show that every topological k-graph constructed from a locally compact Hausdorff space {\Omega} and a family of pairwise commuting local homeomorphisms on {\Omega} satisfying a uniform boundedness condition on the cardinalities of…

Operator Algebras · Mathematics 2011-06-02 Cynthia Farthing , Nura Patani , Paulette N. Willis

In this article, we generalize to the case of measured quantum groupoids on a finite basis some important results concerning actions of locally compact quantum groups on C*-algebras [S. Baaj, G. Skandalis and S. Vaes, 2003]. Let $\cal G$ be…

Operator Algebras · Mathematics 2019-10-01 Jonathan Crespo

Let P be a semigroup that admits an embedding into a group G. Assume that the embedding satisfies a certain Toeplitz condition and that the Baum-Connes conjecture holds for G. We prove a formula describing the K- theory of the reduced…

Operator Algebras · Mathematics 2012-05-25 Joachim Cuntz , Siegfried Echterhoff , Xin Li

Using duality and topological theory of well behaved Hopf algebras (as defined in [2]) we construct star-product models of non compact quantum groups from Drinfeld and Reshetikhin standard deformations of enveloping Hopf algebras of simple…

High Energy Physics - Theory · Physics 2009-10-28 Frédéric Bidegain , Georges Pinczon

In this paper we introduce generalizations of diagonal crossed products, two-sided crossed products and two-sided smash products, for a quasi-Hopf algebra H. The results we obtain may be applied to H^*-Hopf bimodules and generalized…

Quantum Algebra · Mathematics 2009-11-11 Daniel Bulacu , Florin Panaite , Freddy Van Oystaeyen