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The tensor functor called $\alpha$-induction arises from a Frobenius algebra object, or a Q-system, in a braided unitary fusion category. In the operator algebraic language, it gives extensions of endomorphism of $N$ to $M$ arising from a…

Quantum Algebra · Mathematics 2024-08-12 Yasuyuki Kawahigashi

A Q-algebroid is a Lie superalgebroid equipped with a compatible homological vector field and is the infinitesimal object corresponding to a Q-groupoid. We associate to every Q-algebroid a double complex. As a special case, we define the…

Differential Geometry · Mathematics 2020-03-30 Rajan Amit Mehta

In this paper, we initiate the study of higher rank Baumslag-Solitar semigroups and their related C*-algebras. We focus on two extreme, but interesting, classes - one is related to products of odometers and the other is related to…

Operator Algebras · Mathematics 2025-04-25 Robert Valente , Dilian Yang

We define E-theory for separable C*-algebras over second countable topological spaces and establish its basic properties. This includes an approximation theorem that relates the E-theory over a general space to the E-theories over finite…

K-Theory and Homology · Mathematics 2015-10-23 Marius Dadarlat , Ralf Meyer

Let $U_q(\hat{\cal G})$ denote the quantized affine Lie algebra and $U_q({\cal G}^{(1)})$ the quantized {\em nontwisted} affine Lie algebra. Let ${\cal O}_{\rm fin}$ be the category defined in section 3. We show that when the deformation…

High Energy Physics - Theory · Physics 2009-10-22 Yao-Zhong Zhang , Mark D. Gould

We introduce algebraic dynamical systems, which consist of an action of a right LCM semigroup by injective endomorphisms of a group. To each algebraic dynamical system we associate a C*-algebra and describe it as a semigroup C*-algebra. As…

Operator Algebras · Mathematics 2019-02-08 Nathan Brownlowe , Nadia S. Larsen , Nicolai Stammeier

We give a definition of partition C*-algebras: To any partition of a finite set, we assign algebraic relations for a matrix of generators of a universal C*-algebra. We then prove how certain relations may be deduced from others and we…

Operator Algebras · Mathematics 2017-10-18 Moritz Weber

The goal of this article is to emphasize the role of cubical sets in enriched categories theory and infinity-categories theory. We show in particular that categories enriched in cubical sets provide a convenient way to describe many…

Category Theory · Mathematics 2021-04-21 Brice Le Grignou

We study conditions that will ensure that a crossed product of a C*-algebra by a discrete exact group is purely infinite (simple or non-simple). We are particularly interested in the case of a discrete non-amenable exact group acting on a…

Operator Algebras · Mathematics 2010-11-22 Mikael Rordam , Adam Sierakowski

We construct an A_infinity-category D(C|B) from a given A_infinity-category C and its full subcategory B. The construction is similar to a particular case of Drinfeld's quotient of differential graded categories. We use D(C|B) to construct…

Category Theory · Mathematics 2008-02-15 Volodymyr Lyubashenko , Sergiy Ovsienko

We prove that faithful traces on separable and nuclear C*-algebras in the UCT class are quasidiagonal. This has a number of consequences. Firstly, by results of many hands, the classification of unital, separable, simple and nuclear…

Operator Algebras · Mathematics 2016-12-07 Aaron Tikuisis , Stuart White , Wilhelm Winter

Let B be a sigma-unital C*-algebra. We show that every strongly continuous E_0-semigroup on the algebra of adjointable operators on a full Hilbert B-module E gives rise to a full continuous product system of correspondences over B. We show…

Operator Algebras · Mathematics 2013-11-20 Michael Skeide

A new category of topological spaces with additional structures, called m-towers, is introduced. It is shown that there is a covariant functor which establishes a one-to-one correspondences between unital (resp. arbitrary) subhomogeneous…

Operator Algebras · Mathematics 2013-10-22 Piotr Niemiec

We introduce a notion of quantum function, and develop a compositional framework for finite quantum set theory based on a 2-category of quantum sets and quantum functions. We use this framework to formulate a 2-categorical theory of quantum…

Quantum Physics · Physics 2018-09-07 Benjamin Musto , David Reutter , Dominic Verdon

The reflexive completion of a category consists of the Set-valued functors on it that are canonically isomorphic to their double conjugate. After reviewing both this construction and Isbell conjugacy itself, we give new examples and revisit…

Category Theory · Mathematics 2021-06-11 Tom Avery , Tom Leinster

We show that torsion-free finitely generated nilpotent groups are characterised by their group C*-algebras and we additionally recover their nilpotency class as well as the subquotients of the upper central series. We then use a C*-bundle…

Operator Algebras · Mathematics 2018-08-31 Caleb Eckhardt , Sven Raum

In this article we analyze the structure of $2$-categories of symmetric projective bimodules over a finite dimensional algebra with respect to the action of a finite abelian group. We determine under which condition the resulting…

Representation Theory · Mathematics 2019-04-12 Volodymyr Mazorchuk , Vanessa Miemietz , Xiaoting Zhang

In this paper, we investigate *-homomorphisms between C*-algebras associated to \'etale groupoids. First, we prove that such a *-homomorphism can be described by closed invariant subsets, groupoid homomorphisms and cocycles under some…

Operator Algebras · Mathematics 2023-08-24 Fuyuta Komura

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

Let $G=K\ltimes A$ be the semi-direct product group of a compact group $K$ acting on an abelian locally compact group $A$. We describe the $C^*$-algebra $C^*(G)$ of $G$ in terms of an algebra of operator fields defined over the spectrum of…

Operator Algebras · Mathematics 2019-04-23 Hedi Regeiba , Jean Ludwig