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We extend our previous results on generalized Dixmier-Douady theory to graded $C^*$-algebras, as means for explicit computations of the invariants arising for bundles of ungraded $C^*$-algebras. For a strongly self-absorbing $C^*$-algebra…

Operator Algebras · Mathematics 2026-01-08 Marius Dadarlat , Ulrich Pennig

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

It is shown that the class of Fredholm operators over an arbitrary unital $C^{*}$--algebra, which may not admit adjoint ones, can be extended in such a way that this class of compact operators, used in the definition of the class of…

K-Theory and Homology · Mathematics 2007-05-23 Anwar A. Irmatov , Alexandr S. Mishchenko

A surjective endomorphism or, more generally, a polymorphism in the sense of \cite{SV}, of a compact abelian group $H$ induces a transformation of $L^2(H)$. We study the C*-algebra generated by this operator together with the algebra of…

Operator Algebras · Mathematics 2015-06-04 Joachim Cuntz , Anatoly Vershik

The purpose of this paper is two-fold: firstly, we give a characterization on the level of non-unital operator systems for when the zero map is a boundary representation. As a consequence, we show that a non-unital operator system arising…

Operator Algebras · Mathematics 2024-08-13 Se-Jin Kim

We study hermitian operators and isometries on spaces of vector-valued Lipschitz maps with the sum norm: $\|\cdot\|_{\infty}+L(\cdot)$. There are two main theorems in this paper. Firstly, we prove that every hermitian operator on…

Functional Analysis · Mathematics 2024-11-20 Shiho Oi

Let $G$ be a countable group. We introduce several equivalence relations on the set ${\rm Sub}(G)$ of subgroups of $G$, defined by properties of the quasi-regular representations $\lambda_{G/H}$ associated to $H\in {\rm Sub}(G)$ and compare…

Group Theory · Mathematics 2019-03-04 Bachir Bekka , Mehrdad Kalantar

Necessary and sufficient conditions for the exponentiation of finite-dimensional real Lie algebras of linear operators on complete Hausdorff locally convex spaces are obtained, focused on the equicontinuous case - in particular, necessary…

Functional Analysis · Mathematics 2019-11-12 Rodrigo A. H. M. Cabral

We use homotopy operators for the $L_\infty$-algebra associated with an equivariant deformation problem in order to describe a smooth parametrization of the space of structures around a given one. Along the way we give new algebraic and…

Differential Geometry · Mathematics 2025-06-05 Sebastián Daza , João Nuno Mestre

Let $(G,\theta)$ be a Banach--Lie group with involutive automorphism $\theta$, $\g = \fh \oplus \fq$ be the $\theta$-eigenspaces in the Lie algebra $\g$ of $G$, and $H = (G^\theta)_0$ be the identity component of its group of fixed points.…

Representation Theory · Mathematics 2011-02-02 Stéphane Merigon , Karl-Hermann Neeb

We establish the dual equivalence of the category of (potentially nonunital) operator systems and the category of pointed compact nc (noncommutative) convex sets, extending a result of Davidson and the first author. We then apply this dual…

Operator Algebras · Mathematics 2021-03-24 Matthew Kennedy , Se-Jin Kim , Nicholas Manor

The restriction of an irreducible unitary representation $\pi$ of a real reductive group $G$ to a reductive subgroup $H$ decomposes into a direct integral of irreducible unitary representations $\tau$ of $H$ with multiplicities…

Representation Theory · Mathematics 2021-11-29 Jan Frahm

The weak operator topology closed operator algebra on $L^2(R)$ generated by the one-parameter semigroups for translation, dilation and multiplication by $exp(i\lambda x), \lambda \geq 0$, is shown to be a reflexive operator algebra, in the…

Operator Algebras · Mathematics 2015-03-06 Eleftherios Kastis , Stephen Power

We define a notion of smooth cohomology for $ C^* $-algebras which admit a faithful trace. We show that if $ \A\subseteq B(\h) $ is a $ C^* $-algebra with a faithful normal trace $ \tau $ on the ultra-weak closure $ \bar{\A} $ of $…

Operator Algebras · Mathematics 2018-10-22 Massoud Amini , Ahmad Shirinkalam

Let $\mathcal{G}$ be a locally compact \'{e}tale groupoid and $\mathscr{L}(L^2(\mathcal{G}))$ be the $C^*$-algebra of adjointable operators on the Hilbert $C^*$-module $L^2(\mathcal{G})$. In this paper, we discover a notion called…

Operator Algebras · Mathematics 2024-01-30 Baojie Jiang , Jiawen Zhang , Jianguo Zhang

Let s be the space of rapidly decreasing sequences. We give the spectral representation of normal elements in the Fr\'echet algebra L(s',s) of the so-called smooth operators. We also characterize closed commutative *-subalgebras of L(s',s)…

Functional Analysis · Mathematics 2013-04-29 Tomasz Ciaś

We construct some inverse-closed algebras of bounded integral operators with operator-valued kernels, acting in spaces of vector-valued functions on locally compact groups. To this end we make systematic use of covariance algebras…

Functional Analysis · Mathematics 2014-08-21 Ingrid Beltita , Daniel Beltita

In this paper we construct and study the representation theory of a Hopf C^*-algebra with approximate unit, which constitutes quantum analogue of a compact group C^*-algebra. The construction is done by first introducing a…

Quantum Algebra · Mathematics 2007-05-23 Do Ngoc Diep , Phung Ho Hai , Aderemi O. Kuku

We study various operator homological properties of the Fourier algebra $A(G)$ of a locally compact group $G$. Establishing the converse of two results of Ruan and Xu, we show that $A(G)$ is relatively operator 1-projective if and only if…

Operator Algebras · Mathematics 2018-05-24 Jason Crann , Zsolt Tanko

We study the cohomology $H^*_{\lambda \omega}(G/\Gamma, {\mathbb C})$ of the deRham complex $\Lambda^*(G/\Gamma)\otimes{\mathbb C}$ of a compact solvmanifold $G/\Gamma$ with a deformed differential $d_{\lambda \omega}=d + \lambda\omega$,…

Differential Geometry · Mathematics 2007-05-23 Dmitri V. Millionschikov