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The basic notions and results of equivariant KK-theory concerning crossed products can be extended to the case of locally compact quantum groups. We recall these constructions and prove some usefull properties of subgroups and amalgamated…

Operator Algebras · Mathematics 2020-06-04 Roland Vergnioux

Let $\Uq$ be a quantum group. Regarding a (noncommutative) space with $\Uq$-symmetry as a $\Uq$-module algebra $A$, we may think of equivariant vector bundles on $A$ as projective $A$-modules with compatible $\Uq$-action. We construct an…

Quantum Algebra · Mathematics 2009-12-21 G. I. Lehrer , R. B. Zhang

The equivariant coarse index is well-understood and widely used for actions by discrete groups. We extend the definition of this index to general locally compact groups. We use a suitable notion of admissible modules over $C^*$-algebras of…

K-Theory and Homology · Mathematics 2022-07-05 Hao Guo , Peter Hochs , Varghese Mathai

We study a Going-Down (or restriction) principle for ample groupoids and its applications. The Going-Down principle for locally compact groups was developed by Chabert, Echterhoff and Oyono-Oyono and allows to study certain functors, that…

Operator Algebras · Mathematics 2020-07-30 Christian Bönicke

We compute the group homology, the topological K-theory of the reduced C^*-algebra, the algebraic K-theory and the algebraic L-theory of the group ring of the semi-direct product of the three-dimensional discrete Heisenberg group by Z/4.…

K-Theory and Homology · Mathematics 2014-11-11 Wolfgang Lueck

We introduce the Property of Rapid Decay for discrete quantum groups by equivalent characterizations that generalize the classical ones. We then investigate examples, proving in particular the Property of Rapid Decay for unimodular free…

Operator Algebras · Mathematics 2020-06-04 Roland Vergnioux

We prove a `Whitney' presentation, and a `Coulomb branch' presentation, for the torus equivariant quantum K theory of the Grassmann manifold $\mathrm{Gr}(k;n)$, inspired from physics, and stated in an earlier paper. The first presentation…

Algebraic Geometry · Mathematics 2025-09-05 Wei Gu , Leonardo C. Mihalcea , Eric Sharpe , Hao Zou

We study the C*-algebras and von Neumann algebras associated with the universal discrete quantum groups. They give rise to full prime factors and simple exact C*-algebras. The main tool in our work is the study of an amenable boundary…

Operator Algebras · Mathematics 2007-09-25 Stefaan Vaes , Roland Vergnioux

We give a new proof of the Baum--Connes conjecture with coefficients for any second countable, locally compact topological group that acts properly and cocompactly on a finite-dimensional CAT(0)-cubical space with bounded geometry. The…

K-Theory and Homology · Mathematics 2019-08-29 Jacek Brodzki , Erik Guentner , Nigel Higson , Shintaro Nishikawa

These notes are based on a lecture course given by the first author in the Sedano Winter School on K-theory held in Sedano, Spain, on January 22-27th of 2007. They aim at introducing K-theory of C^*-algebras, equivariant K-homology and…

K-Theory and Homology · Mathematics 2020-08-05 Paul F. Baum , Rubén J. Sánchez-García

Let G be a locally compact group, let X be a universal proper G-space, and let Z be a G-equivariant compactification of X that is H-equivariantly contractible for each compact subgroup H of G. Let W be the resulting boundary. Assuming the…

K-Theory and Homology · Mathematics 2015-10-23 Heath Emerson , Ralf Meyer

We introduce a relative tensor product of $C^{*}$-modules and a spatial fiber product of $C^{*}$-algebras that are analogues of Connes' fusion of correspondences and the fiber product of von Neumann algebras introduced by Sauvageot,…

Operator Algebras · Mathematics 2013-07-02 Thomas Timmermann

We introduce an axiomatization of the notion of a semidirect product of locally compact quantum groups and study properties. Our approach is slightly different from the one introduced in the thesis of S.~Roy and, unlike the investigations…

Operator Algebras · Mathematics 2014-10-17 Paweł Kasprzak , Piotr M. Sołtan

We prove an identity relating the product of two opposite Schubert varieties in the (equivariant) quantum K-theory ring of a cominuscule flag variety to the minimal degree of a rational curve connecting the Schubert varieties. We deduce…

Algebraic Geometry · Mathematics 2018-01-31 Anders Skovsted Buch , Sjuvon Chung

For a matched pair of locally compact quantum groups, we construct the double crossed product as a locally compact quantum group. This construction generalizes Drinfeld's quantum double construction. We study C*-algebraic properties of…

Operator Algebras · Mathematics 2007-05-23 Saad Baaj , Stefaan Vaes

Strongly self-absorbing $\mathrm{C}^*$-algebras play a distinguished role in the classification of nuclear $\mathrm{C}^*$-algebras. Their dynamical analogues were introduced and extensively studied by Szab\'o. In this paper, we propose a…

Operator Algebras · Mathematics 2026-03-16 Masaki Izumi , Keiya Ohara

We put two C*-algebras together in a noncommutative tensor product using quantum group coactions on them and a bicharacter relating the two quantum groups that act. We describe this twisted tensor product in two equivalent ways. The first…

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

The operation of tensor product of Cohomological Field Theories (or algebras over genus zero moduli operad) introduced in an earlier paper by the authors is described in full detail, and the proof of a theorem on additive relations between…

q-alg · Mathematics 2009-10-28 M. Kontsevich , Yu. Manin , R. Kaufmann

We make a comprehensive and self-contained study of compact bicrossed products arising from matched pairs of discrete groups and compact groups. We exhibit an automatic regularity property of such a matched pair and and produce an easy…

Operator Algebras · Mathematics 2018-03-22 Pierre Fima , Kunal Mukherjee , Issan Patri

We consider the construction of twisted tensor products in the category of C*-algebras equipped with orthogonal filtrations and under certain assumptions on the form of the twist compute the corresponding quantum symmetry group, which turns…

Operator Algebras · Mathematics 2024-06-25 Jyotishman Bhowmick , Arnab Mandal , Sutanu Roy , Adam Skalski