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We present a simple and intuitive framework for duality of locally compacts groups, which is not based on the Haar measure. This is a map, functorial on a non-degenerate subcategory, on the category of coinvolutive Hopf \cst-algebras, and a…

Operator Algebras · Mathematics 2021-04-09 Yulia Kuznetsova

We introduce a noncommutative and noncocommutative Hopf algebra which takes for certain Hopf categories (and therefore braided monoidal bicategories) a similar role as the Grothendieck- Teichmueller group for quasitensor categories. We also…

Quantum Algebra · Mathematics 2009-11-07 Karl-Georg Schlesinger

We introduce the concept of homotopy equivalence for Hopf Galois extensions and make a systematic study of it. As an application we determine all H-Galois extensions up to homotopy equivalence in the case when H is a Drinfeld-Jimbo quantum…

Quantum Algebra · Mathematics 2010-03-25 Christian Kassel , Hans-Juergen Schneider

A theorem of Kazhdan and Lusztig establishes an equivalence between the category of G(CO)-integrable representations of the Kac-Moody algebra \hat{g}_{-\kappa} at a negative level -\kappa and the category \Rep_q(G) of (algebraic)…

Representation Theory · Mathematics 2021-04-13 Dennis Gaitsgory

Given a finite category T, we consider the functor category [T,A], where A can in particular be any quasi-abelian category. Examples of quasi-abelian categories are given by any abelian category but also by non-exact additive categories as…

Category Theory · Mathematics 2024-03-20 Nadja Egner

A connection between the Galois-theoretic approach to semi-abelian homology and the homological closure operators is established. In particular, a generalised Hopf formula for homology is obtained, allowing the choice of a new kind of…

Category Theory · Mathematics 2014-10-14 Mathieu Duckerts-Antoine , Tomas Everaert , Marino Gran

We give a pedagogical survey of those aspects of the abstract representation theory of quantum groups which are related to the Tannaka-Krein reconstruction problem. We show that every concrete semisimple tensor *-category with conjugates is…

Quantum Algebra · Mathematics 2007-05-23 M. Mueger , J. E. Roberts , L. Tuset

We construct new examples of ergodic coactions of compact quantum groups, in which the multiplicity of an irreducible corepresentation can be strictly larger than the dimension of the latter. These examples are obtained using a bijective…

Operator Algebras · Mathematics 2009-11-11 Julien Bichon , An De Rijdt , Stefaan Vaes

We use braided groups to introduce a theory of $*$-structures on general inhomogeneous quantum groups, which we formulate as {\em quasi-$*$} Hopf algebras. This allows the construction of the tensor product of unitary representations up to…

q-alg · Mathematics 2008-02-03 S. Majid

The notion of Fourier transform is among the more important tools in analysis, which has been generalized in abstract harmonic analysis to the level of abelian locally compact groups. The aim of this paper is to further generalize the…

Operator Algebras · Mathematics 2007-08-23 Byung-Jay Kahng

We supplement the study of Galois theory for algebraic quantum groups started in the paper 'Galois Theory for Multiplier Hopf Algebras with Integrals' by A. Van Daele and Y.H. Zhang. We examine the structure of the Galois objects: algebras…

Quantum Algebra · Mathematics 2019-01-29 K. De Commer

We develop a notion of covariant differential calculus for Hopf algebroids. As a byproduct, we prove analogues of the fundamental theorem of Hopf modules and a Takeuchi-Schneider equivalence in the realm of Hopf algebroids. The resulting…

Quantum Algebra · Mathematics 2026-05-12 Niels Kowalzig , Thomas Weber

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 introduce the language of multiplier Hopf algebra in the context of positive representations of split real quantum groups, and discuss its applications with a continuous version of Lusztig-Kashiwara's canonical basis, which may provide a…

Representation Theory · Mathematics 2014-05-30 Ivan Chi-Ho Ip

Let $G$ be a second-countable, locally compact Hausdorff groupoid equipped with a Haar system. This paper investigates the weak containment of continuous unitary representations of groupoids. We show that both induction and inner tensor…

Functional Analysis · Mathematics 2025-10-08 K. N. Sridharan , N. Shravan Kumar

For a finite-index $\mathrm{II}_1$ subfactor $N \subset M$, we prove the existence of a universal Hopf $\ast$-algebra (or, a discrete quantum group in the analytic language) acting on $M$ in a trace-preserving fashion and fixing $N$…

Quantum Algebra · Mathematics 2022-03-02 Suvrajit Bhattacharjee , Alexandru Chirvasitu , Debashish Goswami

We introduce a cohomology set for groups defined by algebraic difference equations and show that it classifies torsors under the group action. This allows us to compute all torsors for large classes of groups. We also develop some tools for…

Algebraic Geometry · Mathematics 2016-07-26 Annette Bachmayr , Michael Wibmer

{\em Galois comodules} over a coring can be characterised by properties of the relative injective comodules. They motivated the definition of {\em Galois functors} over some comonad (or monad) on any category and in the first section of the…

Category Theory · Mathematics 2009-10-01 Bachuki Mesablishvili , Robert Wisbauer

This is a survey of recent results on classification of compact quantum groups of Lie type, by which we mean quantum groups with the same fusion rules and dimensions of representations as for a compact connected Lie group $G$. The…

Quantum Algebra · Mathematics 2021-06-10 Sergey Neshveyev , Makoto Yamashita

Universal $T$-matrices, or Hopf algebra dual forms, for quantum groups are revisited, and their contraction theory is developed. As a first illustrative example, the (1+1) timelike $\kappa$-Poincar\'e $T$-matrix is explicitly worked out.…

Quantum Algebra · Mathematics 2026-04-23 Angel Ballesteros , Diego Fernandez-Silvestre , Ivan Gutierrez-Sagredo