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We give a survey of the known connections between regularity conditions and amenability conditions in the setting of uniform algebras. For a uniform algebra $A$ we consider the set, $A_{lc}$, of functions in $A$ which are locally constant…

Functional Analysis · Mathematics 2014-12-25 M. J. Heath , J. F. Feinstein

We develop the ring-theoretic notion of Invariant Basis Number in the context of unital $C^*$-algebras and their Hilbert $C^*$-modules. Characterization of $C^*$-algebras with Invariant Basis Number is given in $K$-theoretic terms, closure…

Operator Algebras · Mathematics 2015-09-15 Philip M. Gipson

We show that Segal spaces, and more generally category objects in an $\infty$-category $\mathcal{C}$, can be identified with associative algebras in the double $\infty$-category of spans in $\mathcal{C}$. We use this observation to prove…

Algebraic Topology · Mathematics 2020-06-19 Rune Haugseng

In the present article we review an approximation procedure for amenable traces on unital and separable C*-algebras acting on a Hilbert space in terms of F\o lner sequences of non-zero finite rank projections. We apply this method to…

Operator Algebras · Mathematics 2013-10-17 Pere Ara , Fernando Lledó

We construct a non-separable C*-algebra that is prime but not primitive.

Operator Algebras · Mathematics 2007-05-23 Nik Weaver

Both boundary maps in K-theory are expressed in terms of surjections from projective C*-algebras to semiprojective C*-algebras.

Operator Algebras · Mathematics 2014-01-17 Terry A. Loring

To an $r$-dimensional subshift of finite type satisfying certain special properties we associate a $C^*$-algebra $\cA$. This algebra is a higher rank version of a Cuntz-Krieger algebra. In particular, it is simple, purely infinite and…

Operator Algebras · Mathematics 2013-02-25 Guyan Robertson , Tim Steger

We prove a Corona type theorem with bounds for the Sarason algebra $H^\infty+C$ and determine its spectral characteristics. We also determine the Bass, the dense, and the topological stable ranks of $H^\infty+C$.

Complex Variables · Mathematics 2010-12-06 Raymond Mortini , Brett D. Wick

We associate reduced and full C*-algebras to arbitrary rings and study the inner structure of these ring C*-algebras. As a result, we obtain conditions for them to be purely infinite and simple. We also discuss several examples.…

Operator Algebras · Mathematics 2009-06-01 Xin Li

We show that separability and second-countability are first-order properties among topological spaces definable in o-minimal expansions of $(\mathbb{R},<)$. We do so by introducing first-order characterizations -- definable separability and…

Logic · Mathematics 2025-06-16 Pablo Andújar Guerrero

We give some sufficient conditions of separation of two sets of integer points by a hyperplane. Our conditions are related to the notion of convexity of sets of integer points and are weaker than existing notions.

Combinatorics · Mathematics 2014-02-11 Takuya Kashimura , Yasuhide Numata , Akimichi Takemura

The closed one-sided ideals of a C*-algebra are exactly the closed subspaces supported by the orthogonal complement of a closed projection. Let A be a (not necessarily selfadjoint) subalgebra of a unital C*-algebra B which contains the unit…

Operator Algebras · Mathematics 2007-05-23 Damon M. Hay

It is determined exactly which classifiable C*-algebras have approximately inner flip. The answer includes a number of C*-algebras with torsion in their K-theory, and a number of C*-algebras that are self-absorbing but not strongly…

Operator Algebras · Mathematics 2016-01-11 Aaron Tikuisis

We define the algebra of Colombeau generalized functions on a subset A of the space of d-dimensional generalized points. If the domain A is open, such generalized functions can be identified with pointwise maps from A into the ring of…

Functional Analysis · Mathematics 2008-11-11 Hans Vernaeve

We show that the following properties of the C*-algebras in a class $\mathcal{P}$ are inherited by simple unital ${\rm C^*}$-algebras in the class of asymptotically tracially in $\mathcal{P}$: $(1)$ $\beta$-comparison (in the sense of…

Operator Algebras · Mathematics 2021-01-26 Qingzhai Fan , Xiaochun Fang

In this paper, we will define the reduced cross-sectional $C^*$-algebras of $C^*$-algebraic bundles over locally compact groups and show that if a $C^*$-algebraic bundle has the approximation property (defined similarly as in the discrete…

Operator Algebras · Mathematics 2007-05-23 Ruy Exel , Chi-Keung Ng

We show that the following divisible properties of the ${\rm C^*}$-algebras in a class $\mathcal{P}$ are inherited by simple unital ${\rm C^*}$-algebras in the class of asymptotically tracially in $\mathcal{P}$: $(1)$ $m$-almost divisible,…

Operator Algebras · Mathematics 2024-04-08 Qingzhai Fan , Jiahui Wang

This paper introduces the notions of atoms and atomicity in $C$-algebras and obtains a characterisation of atoms in the $C$-algebra of transformations. Further, this work presents some necessary conditions and sufficient conditions for the…

Logic in Computer Science · Computer Science 2018-04-03 Gayatri Panicker , K. V. Krishna , Purandar Bhaduri

We introduce a new class of operator algebras -- tracially complete C*-algebras -- as a vehicle for transferring ideas and results between C*-algebras and their tracial von Neumann algebra completions. We obtain structure and classification…

We use C*-algebra theory to provide a new method of decomposing the eseential spectra of self-adjoint and non-self-adjoint Schrodinger operators in one or more space dimensions.

Spectral Theory · Mathematics 2008-10-01 E. B. Davies