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In this paper, we consider fixed-circle problem in C*-algebra valued metric spaces and prove some fixed-circle theorems for self-mappings by defining the notion of fixed-circle on such spaces with geometric interpretation. Furthermore, we…

Functional Analysis · Mathematics 2021-04-08 Nilay Değirmen

We consider derivations from the image of the canonical contraction $\theta_A$ from the Haagerup tensor product of a C*-algebra A with itself to the space of completely bounded maps on A. We show that such derivations are necessarily inner…

Operator Algebras · Mathematics 2009-07-14 Ilja Gogić

In the present paper we study the structure of C^*-algebras generated by the components of the polar decompositions of operators in Hilbert space satisfying certain commutation relations.

Operator Algebras · Mathematics 2007-05-23 A. Lebedev , A. Odzijewicz

We study the elementary C*-algebra whose elements are the sum of a diagonal plus a compact operator. We describe the structure of the unitary group, the sets of ideals, automorhisms and projections.

Operator Algebras · Mathematics 2019-03-15 Esteban Andruchow , Eduardo Chiumiento , Alejandro Varela

C*-categories are essentially norm-closed *-categories of bounded linear operators between Hilbert spaces. The purpose of this work is to identify suitable axioms defining Krein C*-categories, i.e. those categories that play the role of…

Operator Algebras · Mathematics 2011-12-30 Paolo Bertozzini , Kasemsun Rutamorn

We obtain partial affirmative answers to the question whether isomorphism of the unitary groups of two C*-algebras, either as topological groups or as discrete groups, implies isomorphism of the C*-algebras as real C*-algebras.

Operator Algebras · Mathematics 2023-06-29 Lionel Fogang Takoutsing , Leonel Robert

Representations of $C^*$-algebras are realized on section spaces of holomorphic homogeneous vector bundles. The corresponding section spaces are investigated by means of a new notion of reproducing kernel, suitable for dealing with…

Operator Algebras · Mathematics 2008-02-22 Daniel Beltita , Jose E. Gale

After introducing a natural notion of continuous fields of locally convex spaces, we establish a new theory of strongly continuous families of possibly unbounded self-adjoint operators over varying Hilbert spaces. This setting allows to…

Functional Analysis · Mathematics 2025-09-10 Ali BenAmor , Batu Güneysu , Thomas Kalmes , Peter Stollmann

Due to the corresponding fact concerning Hilbert spaces, it is natural to ask if the linearity and the orthogonality structure of a Hilbert $C^*$-module determine its $C^*$-algebra-valued inner product. We verify this in the case when the…

Operator Algebras · Mathematics 2010-05-26 Chi-Wai Leung , Chi-Keung Ng , Ngai-Ching Wong

The C*-algebra of bounded operators on the separable infinite-dimensional Hilbert space cannot be mapped to a W*-algebra in such a way that each unital commutative C*-subalgebra C(X) factors normally through $\ell^\infty(X)$. Consequently,…

Operator Algebras · Mathematics 2016-08-05 Chris Heunen , Manuel L. Reyes

We prolonge the list of C*-algebras for which all extensions by any stable separable C*-algebra are semi-invertible. In particular, we handle certain amalgamations, both of C*-algebras and of groups. Concerning groups we consider both…

Operator Algebras · Mathematics 2010-05-13 Vladimir Manuilov , Klaus Thomsen

In the present note we show that the involution in locally C*-algebras is uniquely determined.

Operator Algebras · Mathematics 2012-01-04 Alexander A. Katz

In this paper, we collect some technical results about weights on C*-algebras which are useful in de theory of locally compact quantum groups in the C*-algebra framework. We discuss the extension of a lower semi-continuous weight to a…

Operator Algebras · Mathematics 2007-05-23 Johan Kustermans , Stefaan Vaes

This paper explores the concept of $K$-$g$-frames in locally $C^*$-algebras, which are shown to be more general than $g$-frames. The authors first introduce the notion of a $g$-orthonormal basis and utilize it to define the $g$-operator, a…

Operator Algebras · Mathematics 2024-05-30 Roumaissae Eljazzar , Mohammed Mouniane , Mohamed Rossafi

We explore the recently introduced local-triviality dimensions by studying gauge actions on graph $C^*$-algebras, as well as the restrictions of the gauge action to finite cyclic subgroups. For $C^*$-algebras of finite acyclic graphs and…

Operator Algebras · Mathematics 2021-06-09 Alexandru Chirvasitu , Benjamin Passer , Mariusz Tobolski

The notion of extension of a given $C^*$-category $C$ by a $C^*$-algebra $A$ is introduced. In the commutative case $A = C(\Omega)$, the objects of the extension category are interpreted as fiber bundles over $\Omega$ of objects belonging…

Operator Algebras · Mathematics 2011-11-18 Ezio Vasselli

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

Continuous actions of topological groups on compact Hausdorff spaces $X$ are investigated which induce almost periodic functions in the corresponding commutative C*-algebra. The unique invariant mean on the group resulting from averaging…

Operator Algebras · Mathematics 2009-03-11 M. Frank , V. Manuilov , E. Troitsky

In this article, we identify a suitable approach to define the character space of a commutative unital locally $C^{\ast}$-algebra via the notion of the inductive limit of topological spaces. Also, we discuss topological properties of the…

Operator Algebras · Mathematics 2024-09-04 Santhosh Kumar Pamula , Rifat Siddique

We introduce and analyse the structure of C*-algebras arising from ideals in right tensor C*-precategories, which naturally generalize both relative Cuntz-Pimsner and Doplicher-Roberts algebras. We establish an explicit intrinsic…

Operator Algebras · Mathematics 2013-08-27 B. K. Kwaśniewski