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We introduce the nuclear dimension of a C*-algebra; this is a noncommutative version of topological covering dimension based on a modification of the earlier concept of decomposition rank. Our notion behaves well with respect to inductive…

Operator Algebras · Mathematics 2009-03-31 Wilhelm Winter , Joachim Zacharias

The relative commutant $A'\cap A^{\mathcal{U}}$ of a strongly self-absorbing algebra $A$ is indistinguishable from its ultrapower $A^{\mathcal{U}}$. This applies both to the case when $A$ is the hyperfinite II$_1$ factor and to the case…

Logic · Mathematics 2016-04-19 Ilijas Farah , Bradd Hart , Mikael Rørdam , Aaron Tikuisis

We exhibit a unital simple nuclear non-type-I C*-algebra into which the Jiang-Su algebra does not embed unitally. This answers a question of M. R{\o}rdam.

Operator Algebras · Mathematics 2007-12-13 Marius Dadarlat , Ilan Hirshberg , Andrew S. Toms , Wilhelm Winter

We prove that Z-stable, simple, separable, nuclear, non-unital C*-algebras have nuclear dimension at most 1. This completes the equivalence between finite nuclear dimension and Z-stability for simple, separable, nuclear, non-elementary…

Operator Algebras · Mathematics 2020-11-18 Jorge Castillejos , Samuel Evington

The Kasparov absorption (or stabilization) theorem states that any countably generated Hilbert C*-module is isomorphic to a direct summand in the standard module of square summable sequences in the base C*-algebra. In this paper, this…

Operator Algebras · Mathematics 2014-07-08 Jens Kaad

Suppose $A$ is a separable unital $C(X)$-algebra each fibre of which is isomorphic to the same strongly self-absorbing and $K_{1}$-injective $C^{*}$-algebra $D$. We show that $A$ and $C(X) \otimes D$ are isomorphic as $C(X)$-algebras…

Operator Algebras · Mathematics 2007-05-23 Marius Dadarlat , Wilhelm Winter

We characterize absorption in finite idempotent algebras by means of J\'onsson absorption and cube term blockers. As an application we show that it is decidable whether a given subset is an absorbing subuniverse of an algebra given by the…

Rings and Algebras · Mathematics 2015-12-23 Libor Barto , Alexandr Kazda

We show that C*-algebras generated by irreducible representations of finitely generated nilpotent groups satisfy the universal coefficient theorem of Rosenberg and Schochet. This result combines with previous work to show that these…

Operator Algebras · Mathematics 2023-07-19 Caleb Eckhardt , Elizabeth Gillaspy

We provide some background on the category of classifiable $\mathrm{C}^*$-algebras, whose objects are infinite-dimensional, simple, separable, unital $\mathrm{C}^*$-algebras that have finite nuclear dimension and satisfy the universal…

Operator Algebras · Mathematics 2025-12-09 Bhishan Jacelon

The study of open quantum systems relies on the notion of unital completely positive semigroups on $C^*$-algebras representing physical systems. The natural generalisation would be to consider the unital completely positive semigroups on…

Operator Algebras · Mathematics 2022-11-15 V. I. Yashin

It is known that, under certain conditions, *-representability and extensibility to the unitized *-algebra of a positive linear functional, defined on a *-algebra without unit, are equivalent. In this paper, a new condition for an analogous…

Functional Analysis · Mathematics 2013-12-06 Giorgia Bellomonte

We introduce two nonnegative real-valued invariants for unital and stably finite C*-algebras whose minimal instances coincide with the notion of classifiability via the Elliott invariant. The first of these is defined for AH algebras, and…

Operator Algebras · Mathematics 2007-05-23 Andrew S. Toms

An algebra $\mathcal{A}$ of $n\times n$ complex matrices is said to be \textit{idempotent compressible} if $E\mathcal{A}E$ is an algebra for all idempotents $E\in\mathbb{M}_n(\mathbb{C})$. Analogously, $\mathcal{A}$ is said to be…

Rings and Algebras · Mathematics 2021-06-22 Zachary Cramer , Laurent W. Marcoux , Heydar Radjavi

Let A be a unital separable simple C*-algebra with a unique tracial state. We prove that if A is nuclear and quasidiagonal, then A tensored with the universal UHF-algebra has decomposition rank at most one. Then it is proved that A is…

Operator Algebras · Mathematics 2015-01-14 Hiroki Matui , Yasuhiko Sato

We study permanence properties of the classes of stable and so-called D-stable C*-algebras, respectively. More precisely, we show that a C_0(X)-algebra A is stable if all its fibres are, provided that the underlying compact metrizable space…

Operator Algebras · Mathematics 2007-05-23 Ilan Hirshberg , Mikael Rordam , Wilhelm Winter

Let $A$ be a non-unital Banach algebra, S. J. Bhatt and H. V. Dedania showed that $A$ has the unique uniform norm property (UUNP) if and only if its unitization has UUNP. Here we prove this result for any non-unital algebra.

Functional Analysis · Mathematics 2016-03-02 M. El Azhari

This is a survey of recent progress in the structure and classification theory of nuclear C*-algebras. In particular, I outline how the Universal Coefficient Theorem ensures a positive answer to the quasidiagonality question in the presence…

Operator Algebras · Mathematics 2016-04-29 Wilhelm Winter

We exhibit a countably infinite family of simple, separable, nuclear, and mutually non-isomorphic C*-algebras which agree on K-theory and traces. The algebras do not absorb the Jiang-Su algebra Z tensorially, answering a question of N. C.…

Operator Algebras · Mathematics 2007-08-22 Andrew S. Toms

We give an example of an exact, stably finite, simple. separable C*-algebra D which is not isomorphic to its opposite algebra. Moreover, D has the following additional properties. It is stably finite, approximately divisible, has real rank…

Operator Algebras · Mathematics 2014-01-22 N. Christopher Phillips , Maria Grazia Viola

We study an example of a projective threefold with a non-isolated singularity and its derived category. The singular locus can be locally described as a line of surface nodes compounded with a threefold node at the origin. We construct a…

Algebraic Geometry · Mathematics 2026-01-01 Aporva Varshney
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