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We analyze the decomposition rank (a notion of covering dimension for nuclear $C^*$-algebras introduced by E. Kirchberg and the author) of subhomogeneous $C^*$-algebras. In particular we show that a subhomogeneous $C^*$-algebra has…

Operator Algebras · Mathematics 2007-05-23 Wilhelm Winter

We prove a number of results having to do with equipping type-I $\mathrm{C}^*$-algebras with compact quantum group structures, the two main ones being that such a compact quantum group is necessarily co-amenable, and that if the…

Operator Algebras · Mathematics 2020-08-11 Alexandru Chirvasitu , Jacek Krajczok , Piotr M. Sołtan

We construct countable groups $G$ with the following new degree of W*-superrigidity: if $L(G)$ is virtually isomorphic, in the sense of admitting a bifinite bimodule, with any other group von Neumann algebra $L(\Lambda)$, then the groups…

Operator Algebras · Mathematics 2025-03-14 Milan Donvil , Stefaan Vaes

We construct a simple C*-algebra with nuclear dimension zero that is not isomorphic to its tensor product with the Jiang-Su algebra Z, and a hyperfinite II_1 factor not isomorphic to its tensor product with the separable hyperfinite II_1…

Operator Algebras · Mathematics 2016-01-11 Ilijas Farah , Dan Hathaway , Takeshi Katsura , Aaron Tikuisis

We define a dimension for a triangulated category. We prove a representabilityTheorem for a certain class of functors on finite dimensional triangulatedcategories. We study the dimension of the boundedderived category of an algebra or a…

Category Theory · Mathematics 2007-05-23 Raphael Rouquier

We classify finite-dimensional Nichols algebras over finite nilpotent groups of odd order in group-theoretical terms. The main step is to show that the conjugacy classes of such finite groups are either abelian or of type C; this property…

Quantum Algebra · Mathematics 2021-04-13 Nicolás Andruskiewitsch

We show that Nichols algebras of most simple Yetter-Drinfeld modules over the projective special linear group over a finite field, corresponding to non-semisimple orbits, have infinite dimension. We spell out a new criterium to show that a…

Quantum Algebra · Mathematics 2018-06-01 Nicolás Andruskiewitsch , Giovanna Carnovale , Gastón Andrés García

We partially characterize nuclearity for the recently introduced class of hypergraph C*-algebras using a tailor-made hypergraph minor relation. The latter is generated by certain operations on hypergraphs which resemble the moves on…

Operator Algebras · Mathematics 2026-03-17 Björn Schäfer , Moritz Weber

We give a partial answer to the question for the precise value of the nuclear dimension of UCT-Kirchberg algebras raised by W. Winter and J. Zacharias. It is shown that every Kirchberg algebra in the UCT-class with torsion free $K_1$-group…

Operator Algebras · Mathematics 2017-01-03 Dominic Enders

We study C*-algebras associated with subsemigroups of groups. For a large class of such semigroups including positive cones in quasi-lattice ordered groups and left Ore semigroups, we describe the corresponding semigroup C*-algebras as…

Operator Algebras · Mathematics 2012-05-14 Xin Li

In this paper we prove that the homological dimension of an elementary amenable group over an arbitrary commutative coefficient ring is either infinite or equal to the Hirsch length of the group. Established theory gives simple group…

Group Theory · Mathematics 2019-02-26 Peter Kropholler , Conchita Martínez-Pérez

Kazhdan's notion of property T has recently been imported to the C$^*$-world by Bekka. Our objective is to extend a well known fact to this realm; we show that a nuclear C$^*$-algebra with property T is finite dimensional (for all intents…

Operator Algebras · Mathematics 2007-05-23 Nathanial P. Brown

We show that the dimension of the Cuntz semigroup of a C*-algebra is determined by the dimensions of the Cuntz semigroups of its separable sub-C*-algebras. This allows us to remove separability assumptions from previous results on the…

Operator Algebras · Mathematics 2021-03-25 Hannes Thiel , Eduard Vilalta

While there is only one natural dimension concept for separable, metric spaces, the theory of dimension in noncommutative topology ramifies into different important concepts. To accommodate this, we introduce the abstract notion of a…

Operator Algebras · Mathematics 2015-01-06 Hannes Thiel

We show that stabilizations of sufficiently noncommutative separable unital C*-algebras with finite nuclear dimension have the corona factorization property.

Operator Algebras · Mathematics 2009-04-07 Ping Wong Ng , Wilhelm Winter

We introduce a notion of Rokhlin dimension for one parameter automorphism groups of C*-algebras. This generalizes Kishimoto's Rokhlin property for flows, and is analogous to the notion of Rokhlin dimension for actions of the integers and…

Operator Algebras · Mathematics 2018-01-12 Ilan Hirshberg , Gabor Szabo , Wilhelm Winter , Jianchao Wu

We prove that for any countable directed graph $E$ with Condition~(K), the associated graph $C^*$-algebra $C^*(E)$ has nuclear dimension at most $2$. Furthermore, we provide a sufficient condition producing an upper bound of $1$.

Operator Algebras · Mathematics 2023-10-24 Gregory Faurot , Christopher Schafhauser

We show that for a large class of C*-algebras $\mathcal{A}$, containing arbitrary direct limits of separable type I C*-algebras, the following statement holds: If $A\in \mathcal{A}$ and $B$ is a simple projectionless C*-algebra with trivial…

Operator Algebras · Mathematics 2012-12-03 Luis Santiago

We give two characterizations of tracially nuclear C*-algebras. The first is that the finite summand of the second dual is hyperfinite. The second is in terms of a variant of the weak* uniqueness property. The necessary condition holds for…

Operator Algebras · Mathematics 2018-10-15 Don Hadwin , Weihua Li , Wenjing Liu , Junhao Shen

We study the notions of nuclearity and exactness for module maps on $C^{*}$-algebras which are $C^*$-module over another $C^*$-algebra with compatible actions and examine finite approximation properties of such $C^*$-modules. We prove…

Operator Algebras · Mathematics 2022-06-15 Massoud Amini