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Let $R$ be a commutative unital ring, $\mathfrak{ a}$ an ideal of $R$ and $M$ a fixed $R$-module. We introduce and study generalisations of $\mathfrak{a}$-reduced modules, $\mathfrak{R}_{\mathfrak{ a}}$ and $\mathfrak{a}$-coreduced modules,…

Commutative Algebra · Mathematics 2024-04-11 Tilahun Abebaw , Amanuel Mamo , David Ssevviiri , Zelalem Teshome

We say that a unital C*-algrebra A has the approximate positive factorization property (APFP) if every element of A is a norm limit of products of positive elements of A. (There is also a definition for the nonunital case.) T. Quinn has…

funct-an · Mathematics 2016-08-31 Gerard J. Murphy , N. Christopher Phillips

In this paper, we study the Noetherian dimension of sum of certain modules. It is proved that for any module M which is an irredundant sum of submodules, each of which has Noetherian dimension less than alpha, if M has finite spanning…

Rings and Algebras · Mathematics 2023-06-26 Sayed Malek Javdannezhad , Mohammad Maschizadeh , Nasrin Shirali

Suppose that A is a C*-algebra for which A is isomorphic to A tensor Z, where Z is the Jiang-Su algebra: a unital, simple, stably finite, separable, nuclear, infinite dimensional C*-algebra with the same Elliott invariant as the complex…

Operator Algebras · Mathematics 2010-11-24 Mikael Rordam

In this paper, we exhibit two unital, separable, nuclear ${\rm C}^*$-algebras of stable rank one and real rank zero with the same ordered scaled total K-theory, but they are not isomorphic with each other, which forms a counterexample to…

Operator Algebras · Mathematics 2024-08-29 Qingnan An , Zhichao Liu

Let $X$ and $\mathfrak{a}$ be an affine scheme and (respectively) a finite-dimensional associative algebra over an algebraically-closed field $\Bbbk$, both equipped with actions by a linearly-reductive linear algebraic group $G$. We…

Representation Theory · Mathematics 2025-09-03 Alexandru Chirvasitu

A $C^*$-algebra satisfies the Universal Coefficient Theorem (UCT) of Rosenberg and Schochet if it is equivalent in Kasparov's $KK$-theory to a commutative $C^*$-algebra. This paper is motivated by the problem of establishing the range of…

Operator Algebras · Mathematics 2023-07-14 Rufus Willett , Guoliang Yu

We study quasidiagonality and local reflexivity for $C^{*}$-algebras which are $C^*$-module over another $C^*$-algebra with compatible actions. We introduce and study a notion of amenability for vector valued traces.

Operator Algebras · Mathematics 2022-08-12 Massoud Amini

The radius of comparison is an invariant for unital C*-algebras which extends the theory of covering dimension to noncommutative spaces. We extend its definition to general C*-algebras, and give an algebraic (as opposed to…

Operator Algebras · Mathematics 2010-08-25 Bruce Blackadar , Leonel Robert , Aaron P. Tikuisis , Andrew S. Toms , Wilhelm Winter

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 extend the notion of Rokhlin dimension from topological dynamical systems to $C^*$-correspondences. We show that in the presence of finite Rokhlin dimension and a mild quasidiagonal-like condition (which, for example, is automatic for…

Operator Algebras · Mathematics 2016-08-12 N. P. Brown , A. Tikuisis , A. M. Zelenberg

Let A be a unital simple separable C*-algebra with strict comparison of positive elements. We prove that the Cuntz semigroup of A is recovered functorially from the Murray-von Neumann semigroup and the tracial state space T(A) whenever the…

Operator Algebras · Mathematics 2009-12-04 Marius Dadarlat , Andrew S. Toms

Simple, separable, unital, monotracial and nuclear C$^*$-algebras are shown to have finite nuclear dimension whenever they absorb the Jiang-Su algebra $\mathcal{Z}$ tensorially. This completes the proof of the Toms-Winter conjecture in the…

Operator Algebras · Mathematics 2015-11-30 Yasuhiko Sato , Stuart White , Wilhelm Winter

Let $A$ be a commutative noetherian ring, let $\mathfrak a$ be an ideal of $A$ and let $n$ be a non-negative integer. In this paper, we study $\mathcal{S}_{n}(\mathfrak{a})$, a certain class of $A$-modules and we find some sufficient…

Commutative Algebra · Mathematics 2023-02-09 Hajar Sabzeh , Reza Sazeedeh

Nuclear C*-algebras enjoy a number of approximation properties, most famously the completely positive approximation property. This was recently sharpened to arrange for the incoming maps to be sums of order-zero maps. We show that, in…

Operator Algebras · Mathematics 2017-08-25 Nathanial P. Brown , José R. Carrión , Stuart White

We solve a class of lifting problems involving approximate polynomial relations (soft polynomial relations). Various associated C*-algebras are therefore projective. The technical lemma we need is a new manifestation of Akemann and…

Operator Algebras · Mathematics 2014-01-14 Terry A. Loring , Tatiana Shulman

Let F be a right Hilbert C*-module over a C*-algebra B, and suppose that F is equipped with a left action, by compact operators, of a second C*-algebra A. Tensor product with F gives a functor from Hilbert C*-modules over A to Hilbert…

Operator Algebras · Mathematics 2020-06-19 Tyrone Crisp

We introduce the concept of finitely coloured equivalence for unital *-homomorphisms between C*-algebras, for which unitary equivalence is the 1-coloured case. We use this notion to classify *-homomorphisms from separable, unital, nuclear…

Operator Algebras · Mathematics 2019-04-24 Joan Bosa , Nathanial P. Brown , Yasuhiko Sato , Aaron Tikuisis , Stuart White , Wilhelm Winter

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

Let $R$ be a commutative noetherian ring, $\frak a$ be an ideal of $R$, $\mathcal{S}$ be an arbitrary Serre subcategory of $R$-modules satisfying the condition $C_{\frak a}$ and let $\mathcal{N}$ be the subcategory of finitely generated…

Commutative Algebra · Mathematics 2022-05-31 Negar Alipour , Reza Sazeedeh