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Let $(\mathcal{G},\nu)$ be a $t$-discrete ergodic groupoid. Consider a finite Von Neumann algebra $\mathcal{M}$ with separable predual. We prove that every uniformly bounded measurable representation $\rho:\mathcal{G} \rightarrow…

Operator Algebras · Mathematics 2025-12-29 Alessio Savini

We introduce a general notion of quantum universal enveloping algebroids (QUE algebroids), or quantum groupoids, as a unification of quantum groups and star-products. Some basic properties are studied including the twist construction and…

Quantum Algebra · Mathematics 2016-09-07 Ping Xu

This is the second part of the paper. Results of the first part about crossed modules are applied here to study of quantum groups in braided categories. Correct cross product in the class of quantum braided groups is built. Criterion when…

High Energy Physics - Theory · Physics 2008-02-03 Yuri Bespalov

We develop a generalization of quantitative $K$-theory, which we call controlled $K$-theory. It is powerful enough to study the $K$-theory of crossed product of $C^*$-algebras by action of \'etale groupoids and discrete quantum groups. In…

K-Theory and Homology · Mathematics 2017-10-18 Clément Dell'Aiera

We introduce the notion of Zimmer amenability for actions of discrete quantum groups on von Neumann algebras. We prove generalizations of several fundamental results of the theory in the noncommutative case. In particular, we give a…

Operator Algebras · Mathematics 2018-03-20 Mohammad S. M. Moakhar

This is Part II in our multi-part series of papers developing the theory of a subclass of locally compact quantum groupoids ("quantum groupoids of separable type"), based on the purely algebraic notion of weak multiplier Hopf algebras. The…

Operator Algebras · Mathematics 2019-08-21 Byung-Jay Kahng , Alfons Van Daele

We establish an induction isomorphism in the context of measurable bounded cohomology of discrete measured groupoid, which generalizes the Eckmann-Shapiro isomorphism in bounded cohomology of lattices due to Burger and Monod. In our wider…

Dynamical Systems · Mathematics 2025-10-24 Tobias Hartnick , Filippo Sarti

We prove a weak form of the mean ergodic theorem for actions of amenable locally compact quantum groups in the von Neumann algebra setting.

Operator Algebras · Mathematics 2008-12-05 Rocco Duvenhage

We show that an isometric action of a compact quantum group on the underlying geodesic metric space of a compact connected Riemannian manifold $(M,g)$ with strictly negative curvature is automatically classical, in the sense that it factors…

Quantum Algebra · Mathematics 2016-01-27 Alexandru Chirvasitu

In this paper we study various convolution-type algebras associated with a locally compact quantum group from cohomological and geometrical points of view. The quantum group duality endows the space of trace class operators over a locally…

Functional Analysis · Mathematics 2011-10-25 Mehrdad Kalantar , Matthias Neufang

A half a century ago, George Bergman introduced stunning machinery which would realise any commutative conical monoid as the non-stable $K$-theory of a ring. The ring constructed is ``minimal" or ``universal". Given the success of graded…

Rings and Algebras · Mathematics 2024-03-05 Roozbeh Hazrat , Huanhuan Li , Raimund Preusser

In recent work, Launois and Lenagan have shown how to construct a cocycle twisting of the quantum Grassmannian and an isomorphism of the twisted and untwisted algebras that sends a given quantum minor to the minor whose index set is…

Quantum Algebra · Mathematics 2013-10-22 Justin M. Allman , Jan E. Grabowski

The quantum completion of the space of connections in a manifold can be seen as the set of all morphisms from the groupoid of the edges of the manifold to the (compact) gauge group. This algebraic construction generalizes the analogous…

High Energy Physics - Theory · Physics 2017-08-23 J. M. Velhinho

We prove a "unique crossed product decomposition" result for group measure space II_1 factors arising from arbitrary free ergodic probability measure preserving (p.m.p.) actions of groups \Gamma in a fairly large family G, which contains…

Operator Algebras · Mathematics 2015-05-13 Sorin Popa , Stefaan Vaes

In this paper using split extensions of group-groupoids we obtain the notion of crossed modules over group-grouoids which are also called 2-groups and we prove a categorical equivalence of these types of crossed modules and double…

Category Theory · Mathematics 2021-02-16 Sedat Temel , Tunçar Şahan , Osman Mucuk

In this work, we address ergodicity of smooth actions of finitely generated semi-groups on an m-dimensional closed manifold M. We provide sufficient conditions for such an action to be ergodic with respect to the Lebesgue measure. Our…

Dynamical Systems · Mathematics 2015-05-14 Azam Ehsani , Fatome-Helen Ghane , Marzie Zaj

In a series of papers we proposed a model unifying general relativity and quantum mechanics. The idea was to deduce both general relativity and quantum mechanics from a noncommutative algebra ${\cal A}_{\Gamma}$ defined on a transformation…

General Relativity and Quantum Cosmology · Physics 2015-01-09 M. Heller , T. Miller , L. Pysiak , W. Sasin

Using the theory of measurable categories developped by Yetter in work in preparation, we provide a notion of representations of 2-groups more well-suited to physically and geometrically interesting examples than that proposed in…

Quantum Algebra · Mathematics 2007-05-23 L. Crane , D. N. Yetter

We establish new characterizations for (pseudo)isometric extensions of topological dynamical systems. For such extensions, we also extend results about relatively invariant measures and Fourier analysis that were previously only known in…

Dynamical Systems · Mathematics 2020-09-29 Nikolai Edeko , Henrik Kreidler

In the framework of locally compact quantum groups, we provide an induction procedure for unitary corepresentations as well as coactions on C*-algebras. We prove imprimitivity theorems that unify the existing theorems for actions and…

Operator Algebras · Mathematics 2007-05-23 Stefaan Vaes