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We give a complete $K$-theoretical description of when an extension of two simple graph $C^{*}$-algebras is again a graph $C^{*}$-algebra.

算子代数 · 数学 2020-07-07 Søren Eilers , James Gabe , Takeshi Katsura , Efren Ruiz , Mark Tomforde

\noindent Let $A$ be an arbitrary $C^*$ algebra. In \cite{BH} Blackadar and Handelman conjectured the set of lower semicontinuous dimension functions on $A$ to be pointwise dense in the set $DF(A)$ of all dimension functions on $A$ and…

算子代数 · 数学 2016-01-15 Kaushika De Silva

We construct uncountably many mutually nonisomorphic simple separable stably finite unital exact C$^\ast$-algebras which are not isomorphic to their opposite algebras. In particular, we prove that there are uncountably many possibilities…

算子代数 · 数学 2024-02-14 N. Christopher Phillips , Maria Grazia Viola

We prove a strong classification result for a certain class of $C^{*}$-algebras with primitive ideal space $\widetilde{\mathbb{N}}$, where $\widetilde{\mathbb{N}}$ is the one-point compactification of $\mathbb{N}$. This class contains the…

算子代数 · 数学 2013-11-13 James Gabe , Efren Ruiz

We prove constructive versions of various usual results related to the Gelfand duality. Namely, that the constructive Gelfand duality extend to a duality between commutative nonunital C*-algebras and locally compact completely regular…

范畴论 · 数学 2015-02-04 Simon Henry

The class of simple separable KK-contractible (KK-equivalent to $\{0\}$) C*-algebras which have finite nuclear dimension is shown to be classified by the Elliott invariant. In particular, the class of C*-algebras $A\otimes \mathcal W$ is…

算子代数 · 数学 2020-12-08 George A. Elliott , Guihua Gong , Huaxin Lin , Zhuang Niu

We give a detailed introduction to the theory of Cuntz semigroups for C*-algebras. Beginning with the most basic definitions and technical lemmas, we present several results of historical importance, such as Cuntz's theorem on the existence…

算子代数 · 数学 2022-12-14 Eusebio Gardella , Francesc Perera

For elements $a, b$ of a C*-algebra we denote $a=ab$ by $a\ll b$. We show that all $\omega_1$-unital C*-algebras have $\ll$-increasing approximate units, extending a classical result for $\sigma$-unital C*-algebras. We also construct (in…

算子代数 · 数学 2019-11-19 Tristan Bice , Piotr Koszmider

We show that the group C*-algebra of any elementary amenable group is quasidiagonal. This is an offspring of recent progress in the classification theory of nuclear C*-algebras.

算子代数 · 数学 2014-09-24 Narutaka Ozawa , Mikael Rordam , Yasuhiko Sato

We consider operators on $L^2$ spaces that expand the support of vectors in a manner controlled by some constraint function. The primary objects of study are $\mathrm C^*$-algebras that arise from suitable families of constraints, which we…

算子代数 · 数学 2022-11-08 Bruno de Mendonça Braga , Joseph Eisner , David Sherman

Let X be a path connected, compact metric space and let A be a unital separable simple nuclear Z-stable real rank zero C*-algebra. We classify all the unital *-embeddings (up to approximate unitary equivalence) of C(X) into A. Specifically,…

算子代数 · 数学 2007-09-11 P. W. Ng , Wilhelm Winter

Given a closed ideal $I$ in a C*-algebra $A$, we show that $A$ is pure if and only if $I$ and $A/I$ are pure. More generally, we study permanence of comparison and divisibility properties when passing to extensions. As an application we…

算子代数 · 数学 2025-06-13 Francesc Perera , Hannes Thiel , Eduard Vilalta

We show that finitely generated subhomogeneous C*-algebras have finite decomposition rank. As a consequence, any separable ASH C*-algebra can be written as an inductive limit of subhomogeneous C*-algebras each of which has finite…

算子代数 · 数学 2007-05-23 Ping Wong Ng , Wilhelm Winter

We show that nuclear C*-algebras have a refined version of the completely positive approximation property, in which the maps that approximately factorize through finite dimensional algebras are convex combinations of order zero maps. We use…

算子代数 · 数学 2012-04-27 Ilan Hirshberg , Eberhard Kirchberg , Stuart White

We introduce a notion of approximate ideal structure for a $C^*$-algebra, and use it as a tool to study $K$-theory groups. The notion is motivated by the classical Mayer-Vietoris sequence, by the theory of nuclear dimension as introduced by…

算子代数 · 数学 2020-05-12 Rufus Willett

We introduce and analyse the structure of C*-algebras arising from ideals in right tensor C*-precategories, which naturally generalize both relative Cuntz-Pimsner and Doplicher-Roberts algebras. We establish an explicit intrinsic…

算子代数 · 数学 2013-08-27 B. K. Kwaśniewski

Further to the functional representations of C$^*$-algebras proposed by R. Cirelli, A. Mania and L. Pizzocchero, we consider in this article the uniform K\"ahler bundle (in short, UKB) description of some C$^*$-algebraic subjects. In…

算子代数 · 数学 2015-09-10 Xiao Chen

We extend in this paper the characterisation of a separable nuclear \cst-algebra given by Kirchberg proving that given a unital separable continuous field of nuclear C*-algebras A over a compact metrizable space X, the C(X)-algebra A is…

算子代数 · 数学 2016-09-07 Etienne Blanchard

Given an ultragraph in the sense of Tomforde, we construct a topological quiver in the sense of Muhly and Tomforde in such a way that the universal C*-algebras associated to the two objects coincide. We apply results of Muhly and Tomforde…

算子代数 · 数学 2008-04-25 Takeshi Katsura , Paul S. Muhly , Aidan Sims , Mark Tomforde

Let A be a simple, unital, exact, and finite C*-algebra which absorbs the Jiang-Su algebra Z tensorially. We prove that the Cuntz semigroup of A admits a complete order embedding into an ordered semigroup obtained from the Elliott invariant…

算子代数 · 数学 2007-05-23 Francesc Perera , Andrew S. Toms