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We consider positive semidefinite kernels which have values given by bounded linear operators on certain bundles of Hilbert spaces and which are invariant under actions of $*$-semigroupoids. For these kernels, we prove that there exist…

Functional Analysis · Mathematics 2026-02-20 Aurelian Gheondea

We consider positive semidefinite kernels valued in the $*$-algebra of adjointable operators on a VE-space (Vector Euclidean space) and that are invariant under actions of $*$-semigroups. A rather general dilation theorem is stated and…

Functional Analysis · Mathematics 2017-02-06 Serdar Ay , Aurelian Gheondea

We consider the space of adjointable operators on barreled VH (Vector Hilbert) spaces and show that such operators are automatically bounded.This generalizes the well known corresponding result for locally Hilbert $C^*$-modules.We pick a…

Functional Analysis · Mathematics 2021-08-02 Serdar Ay

We single out the concept of concrete Hilbert module over a locally $C^*$-algebra by means of locally bounded operators on certain strictly inductive limits of Hilbert spaces. Using this concept, we construct an operator model for all…

Operator Algebras · Mathematics 2025-11-04 Aurelian Gheondea

We consider weakly positive semidefinite kernels valued in ordered $*$-spaces with or without certain topological properties, and investigate their linearisations (Kolmogorov decompositions) as well as their reproducing kernel spaces. The…

Functional Analysis · Mathematics 2025-11-04 Serdar Ay , Aurelian Gheondea

The aim of this paper is to present a unified framework in the setting of Hilbert $C^*$-modules for the scalar- and vector-valued reproducing kernel Hilbert spaces and $C^*$-valued reproducing kernel spaces. We investigate conditionally…

Operator Algebras · Mathematics 2021-05-17 M. S. Moslehian

Let $G$ be a locally compact abelian group with a Haar measure, and $Y$ be a measure space. Suppose that $H$ is a reproducing kernel Hilbert space of functions on $G\times Y$, such that $H$ is naturally embedded into $L^2(G\times Y)$ and is…

Functional Analysis · Mathematics 2025-04-28 Crispin Herrera-Yañez , Egor A. Maximenko , Gerardo Ramos-Vazquez

We suppose that $G$ is a locally compact abelian group, $Y$ is a measure space, and $H$ is a reproducing kernel Hilbert space on $G\times Y$ such that $H$ is naturally embedded into $L^2(G\times Y)$ and it is invariant under the…

Operator Algebras · Mathematics 2025-04-29 Shubham R. Bais , Egor A. Maximenko , D. Venku Naidu

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

We generalize the concept of coherent states, traditionally defined as special families of vectors on Hilbert spaces, to Hilbert modules. We show that Hilbert modules over $C^*$-algebras are the natural settings for a generalization of…

Mathematical Physics · Physics 2015-05-19 S. Twareque Ali , T. Bhattacharyya , S. Shyam Roy

We introduce and study a class $\mathcal{M}$ of generalized positive definite kernels of the form $K\colon X\times X\to L(\mathfrak{A},L(H))$, where $\mathfrak{A}$ is a unital $C^{*}$-algebra and $H$ a Hilbert space. These kernels encode…

Operator Algebras · Mathematics 2025-05-28 Palle E. T. Jorgensen , James Tian

We study reproducing kernel Hilbert spaces on the unit ball with the complete Nevanlinna-Pick property through the representation theory of their algebras of multipliers. We give a complete description of the representations in terms of the…

Operator Algebras · Mathematics 2020-09-23 Raphaël Clouâtre , Michael Hartz

In this paper we study hermitian kernels invariant under the action of a semigroup with involution. We characterize those hermitian kernels which realize the given action by bounded operators on a Krein space. Applications to the GNS…

Functional Analysis · Mathematics 2009-10-31 Tiberiu Constantinescu , Aurelian Gheondea

The study presents a vector-valued extension of the classical Mercer theorem within the framework of reproducing kernel Hilbert spaces defined over Kaplansky-Hilbert modules associated with the algebra of essentially bounded measurable…

Functional Analysis · Mathematics 2025-11-24 A. Arziev , K. Kudaybergenov. P. Orinbaev

An operator *-algebra is a non-selfadjoint operator algebra with completely isometric involution. We show that any operator *-algebra admits a faithful representation on a Hilbert space in such a way that the involution coincides with the…

Operator Algebras · Mathematics 2019-11-28 David Blecher , Jens Kaad , Bram Mesland

We show that every Finsler module over a $C^*$-algebra has a quasi-representation into the Banach space $\mathbb{B}(\mathscr{H},\mathscr{K})$ of all bounded linear operators between some Hilbert spaces $\mathscr{H}$ and $\mathscr{K}$. We…

Operator Algebras · Mathematics 2012-01-13 M. Amyari , M. Chakoshi , M. S. Moslehian

We study the theory of a Hilbert space H as a module for a unital C*-algebra A from the point of view of continuous logic. We give an explicit axiomatization for this theory and describe the structure of all the representations which are…

Logic · Mathematics 2012-12-03 Camilo Argoty

Motivated by Cuntz-Krieger-Toeplitz systems associated to undirected graphs and representations of groupoids, we obtain a generalisation of the Sz-Nagy's Dilation Theorem for operator valued partially positive semidefinite maps on…

Operator Algebras · Mathematics 2025-11-04 Aurelian Gheondea , Bogdan Udrea

In this paper, we introduce the notion of invariant submodule in the theory of Hilbert C*-modules and study some basic properties of bounded adjointable operators and their generalized inverses which have nontrivial invariant submodules. We…

Operator Algebras · Mathematics 2025-06-03 Kamran Sharifi

Let E be an operator algebra on a Hilbert space with finite-dimensional generated C*-algebra. A classification is given of the locally finite algebras and the operator algebras obtained as limits of direct sums of matrix algebras over E…

Operator Algebras · Mathematics 2007-05-23 S. C. Power
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