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We study C*-irreducibility of inclusions of reduced twisted group C*-algebras and of reduced group C*-algebras. We characterize C*-irreducibility in the case of an inclusion arising from a normal subgroup, and exhibit many new examples of…

Operator Algebras · Mathematics 2023-01-31 Erik Bédos , Tron Omland

The notion of bounded element of C*-inductive locally convex spaces (or C*-inductive partial *-algebras) is introduced and discussed in two ways: the first one takes into account the inductive structure provided by certain families of…

Operator Algebras · Mathematics 2013-07-29 Giorgia Bellomonte , Salvatore Di Bella , Camillo Trapani

We say that a contractive Hilbert space operator is universal if there is a natural surjection from its generated C*-algebra to the C*-algebra generated by any other contraction. A universal contraction may be irreducible or a direct sum of…

Operator Algebras · Mathematics 2019-05-06 Kristin Courtney , David Sherman

The note is concerned with inductive systems of Toeplitz algebras and their $*$-homomorphisms over arbitrary partially ordered sets. The Toeplitz algebra is the reduced semigroup $C^*$-algebra for the additive semigroup of non-negative…

Operator Algebras · Mathematics 2019-05-17 E. V. Lipacheva

We consider Fell bundles over discrete groups, and the C*-algebra which is universal for representations of the bundle. We define deformations of Fell bundles, which are new Fell bundles with the same underlying Banach bundle but with the…

Operator Algebras · Mathematics 2016-06-01 Iain Raeburn

We introduce the notion of a (noncommutative) C*-Segal algebra as a Banach algebra which is a dense ideal in a C*-algebra. Several basic properties are investigated and, with the aid of the theory of multiplier modules, the structure of…

Operator Algebras · Mathematics 2012-09-25 Jukka Kauppi , Martin Mathieu

In this paper we associate to every reduced C*-algebraic quantum group A a universal C*-algebraic quantum group. We fine tune a proof of Kirchberg to show that every *-representation of a modified L1-space is generated by a unitary…

Operator Algebras · Mathematics 2007-05-23 Johan Kustermans

A collection of partial isometries whose range and initial projections satisfy a specified set of conditions often gives rise to a partial representation of a group. The C*-algebra generated by the partial isometries is thus a quotient of…

funct-an · Mathematics 2016-08-31 Ruy Exel , Marcelo Laca , John Quigg

Given an n-tuple of multiplication operators on the Bergman space of a bounded pseudoconvex domain in C^n, we study the algebra of their commutants. In particular, we give a geometric description of the maximal C*-subalgebra of this…

Functional Analysis · Mathematics 2016-07-05 Akaki Tikaradze

We characterize when a C*-cover admits a C*-dynamical extension of dynamics on an operator algebra in terms of the boundary ideal structure for the operator algebra in its maximal representation and show that the C*-covers that admit such…

Operator Algebras · Mathematics 2024-03-25 Mitch Hamidi

We characterise absolutely dilatable completely positive maps on the space of all bounded operators on a Hilbert space that are also bimodular over a given von Neumann algebra as rotations by a suitable unitary on a larger Hilbert space…

Operator Algebras · Mathematics 2025-04-25 Alexandros Chatzinikolaou , Ivan G. Todorov , Lyudmila Turowska

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 consider various lifting problems for C*-algebras. As an application of our results we show that any commuting family of order zero maps from matrices to a von Neumann central sequence algebra can be lifted to a commuting family of order…

Operator Algebras · Mathematics 2019-10-30 Don Hadwin , Tatiana Shulman

This paper investigates the algebraic structure of indecomposable $\mathbb{N}$-graded vertex algebras $V = \bigoplus_{n=0}^{\infty} V_n$, emphasizing the intricate interactions between the commutative associative algebra $V_0$, the Leibniz…

Quantum Algebra · Mathematics 2024-12-12 Alex Keene , Christian Soltermann , Gaywalee Yamskulna

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…

The GNS construction for positive invariant sesquilinear forms on quasi *-algebras is generalized to a class of positive C*-valued sesquilinear maps on quasi *-algebras. The result is a *-representation taking values in a space of operators…

Operator Algebras · Mathematics 2024-08-08 Giorgia Bellomonte , Stefan Ivkovic , Camillo Trapani

In this paper we study the structure of the $C^*$-algebra, generated by the representation of the paths semigroup on a partially ordered set (poset) and get the net of isomorphic $C^*$-algebras over this poset. We construct the extensions…

Operator Algebras · Mathematics 2016-11-02 Suren Grigoryan , Tamara Grigoryan , Ekaterina Lipacheva , Airat Sitdikov

We consider three notions of divisibility in the Cuntz semigroup of a C*-algebra, and show how they reflect properties of the C*-algebra. We develop methods to construct (simple and non-simple) C*-algebras with specific divisibility…

Operator Algebras · Mathematics 2014-02-26 Leonel Robert , Mikael Rordam

Any $C^*$-algebra can be regarded as a generalization of locally compact, Hausdorff topological space $\mathcal X$. From the commutative commutative Gelfand-Na\u{\i}mark theorem it follows that the spectrum of any commutative $C^*$-algebra…

Operator Algebras · Mathematics 2026-03-17 Petr Ivankov

We study the Wold decomposition for representations of a self-similar semigroup $P$ action on a directed graph $E$. We then apply this decomposition to the case where $P=\mathbb{N}$ to study the C*-envelope of the associated universal…

Operator Algebras · Mathematics 2024-05-14 Boyu Li , Dilian Yang
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