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I introduce yet another way to associate a C*-algebra to a graph and construct a simple nuclear C*-algebra that has irreducible representations both on a separable and a nonseparable Hilbert space.

Operator Algebras · Mathematics 2009-10-24 Ilijas Farah

We study the question when for a given *-algebra $\mathcal{A}$ a sequence of cones $C_n\in M_n(\mathcal{A})$ can be realized as cones of positive operators in a faithful *-representation of $\mathcal{A}$ on a Hilbert space. A…

Operator Algebras · Mathematics 2010-03-19 Ekaterina Juschenko , Stanislav Popovych

The question of existence of outer automorphisms of a simple algebraic group $G$ arises naturally both when working with the Galois cohomology of $G$ and as an example of the algebro-geometric problem of determining which connected…

Group Theory · Mathematics 2016-09-14 Skip Garibaldi , Holger P. Petersson

In this note, we describe how the study of backgrounds for general quantum systems can be formulated in terms of the representation theory of abstract $C^*$ algebras. We illustrate our general framework through two example systems:…

High Energy Physics - Theory · Physics 2026-01-15 Marc Klinger

In this paper we study the completely bounded anti-isomorphisms on operator algebras, that work similarly to the involutions with the exception for the property of being completely isometric. We elaborate the Blecher's characterization…

Operator Algebras · Mathematics 2011-04-15 Nikolay P. Ivankov

We combine the notion of norming algebra introduced by Pop, Sinclair and Smith with a result of Pisier to show that if A_1 and A_2 are operator algebras, then any bounded epimorphism of A_1 onto A_2 is completely bounded provided that A_2…

Operator Algebras · Mathematics 2016-05-13 David R. Pitts

The Euclidean operator radius of two bounded linear operators in the Hilbert $C^*$-module over $\A$ is given some precise bounds. Their relationship to recent findings in the literature that offer precise upper and lower bounds on the…

Functional Analysis · Mathematics 2023-07-06 M. H. M. Rashid

We consider second order differential operators $P$ with polynomial coefficients that preserve the vector space $V_k$ of polynomials of degrees not greater then $k$. We assume that the metric associated with the symbol of $P$ is flat and…

Exactly Solvable and Integrable Systems · Physics 2015-09-30 Vladimir Sokolov

We exhibit examples of simple separable nuclear C*-algebras, along with actions of the circle group and outer actions of the integers, which are not equivariantly isomorphic to their opposite algebras. In fact, the fixed point subalgebras…

Operator Algebras · Mathematics 2016-02-16 Marius Dadarlat , Ilan Hirshberg , N. Christopher Phillips

We discuss algebraic properties for the symbols of geometric first order differential operators on almost Hermitian manifolds and K\"ahler manifolds. Through study on the universal enveloping algebra and higher Casimir elements, we know…

Differential Geometry · Mathematics 2007-05-23 Yasushi Homma

Motivated by importance of operator spaces contained in the set of all scalar multiples of isometries ($MI$-spaces) in a separable Hilbert space for $C^*$-algebras and E-semigroups we exhibit more properties of such spaces. For example, if…

Operator Algebras · Mathematics 2008-05-23 Waclaw Szymanski

The study of operator algebras on Hilbert spaces, and C*-algebras in particular, is one of the most active areas within Functional Analysis. A natural generalization of these is to replace Hilbert spaces (which are $L^2$-spaces) with…

Functional Analysis · Mathematics 2019-10-09 Eusebio Gardella

Let H be a separable infinite dimensional complex Hilbert space. We prove that every continuous 2-local automorphism of the poset (that is, partially ordered set) of all idempotents on H is an automorphism. Similar results concerning the…

Operator Algebras · Mathematics 2007-05-23 Lajos Molnar

Every partial algebra is the colimit of its total subalgebras. We prove this result for partial Boolean algebras (including orthomodular lattices) and the new notion of partial C*-algebras (including noncommutative C*-algebras), and…

Category Theory · Mathematics 2012-12-05 Benno van den Berg , Chris Heunen

For a smooth manifold with boundary we construct a semigroupoid and a continuous field of C*-algebras which extend Connes' construction of the tangent groupoid. We show the asymptotic multiplicativity of \hbar-scaled truncated…

Functional Analysis · Mathematics 2007-05-23 Johannes Aastrup , Ryszard Nest , Elmar Schrohe

Let $E$ and $F$ be Hilbert $C^*$-modules over a $C^*$-algebra $\CAlg{A}$. New classes of (possibly unbounded) operators $t:E\to F$ are introduced and investigated. Instead of the density of the domain $\Def(t)$ we only assume that $t$ is…

Operator Algebras · Mathematics 2015-07-09 René Gebhardt , Konrad Schmüdgen

Hilbert C*-modules are the analogues of Hilbert spaces where a C*-algebra plays the role of the scalar field. With the advent of Kasparov's celebrated KK-theory they became a standard tool in the theory of operator algebras. While the…

Operator Algebras · Mathematics 2016-12-23 Jens Kaad , Matthias Lesch

For special universal $C^*$-algebras associated to $k$-semigraphs we present the universal representations of these algebras, prove a Cuntz--Krieger uniqueness theorem, and compute the $K$-theory. These $C^*$-algebras seem to be the most…

Operator Algebras · Mathematics 2013-06-24 Bernhard Burgstaller

In this paper I show that pointwise bounded asymptotic morphisms between separable metrisable locally convex *-algebras induce continuous maps between the quasi-unitary groups of the algebras, provided that the algebras support a certain…

Operator Algebras · Mathematics 2007-05-23 Edwin J. Beggs

We prove that the reduced C*-algebras of centerless mapping class groups and outer automorphism groups of free groups are simple, as are the irreducible pure subgroups of mapping class groups and the analogous subgroups of outer…

Operator Algebras · Mathematics 2007-05-23 Martin R. Bridson , Pierre de la Harpe
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