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We consider existence and uniqueness of symmetric approximation of frames by normalized tight frames and of symmetric orthogonalization of bases by orthonormal bases in Hilbert spaces H . More precisely, we determine whether a given frame…

Functional Analysis · Mathematics 2025-05-08 M. Frank , V. I. Paulsen , T. R. Tiballi

A notion of super operator system is defined which generalizes the usual notion of operator systems to include certain unital involutive operator spaces which cannot be represented completely isometric as a concrete operator system on some…

Operator Algebras · Mathematics 2013-08-05 Ulrich Haag

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 study unital operator spaces endowed with a partially defined product. We give a matrix-norm characterization of such products that allows for a representation theorem where the partial product is realized as composition of operators on…

Operator Algebras · Mathematics 2025-11-07 Adam Dor-On , Travis B. Russell

As a partial generalisation of the Uhlhorn theorem to Hilbert $C^*$-modules, we show in this article that the module structure and the orthogonality structure of a Hilbert $C^*$-module determine its Hilbert $C^*$-module structure. In fact,…

Operator Algebras · Mathematics 2010-07-27 Chi-Wai Leung , Chi-Keung Ng , Ngai-Ching Wong

In this papers we investigate the g-frame and Bessel g-sequence related to a linear bounded operator $K$ in Hilbert $C^{\ast}$-module and we establish some results.

Operator Algebras · Mathematics 2019-01-15 H. Labrigui , A. Touri , S. Kabbaj

Given a pair of positive real numbers $\alpha, \beta$ and a sesqui-analytic function $K$ on a bounded domain $\Omega \subset \mathbb C^m$, in this paper, we investigate the properties of the sesqui-analytic function $\mathbb K^{(\alpha,…

Functional Analysis · Mathematics 2019-06-11 Soumitra Ghara , Gadadhar Misra

In this peaper we stady certain Bessel sequences $\left\{f_k\right\}_{k=1}^{\infty}$ in Hilbert C*- modules $\mathcal{H}$ for which operator $S$ defined by \ref{eq2} is of the form $\mathcal{T}+\xi I$, for some real number $\xi$ and a…

Functional Analysis · Mathematics 2024-01-01 Abdelilah Karara , Khadija Mabrouk

Frame Theory has a great revolution for recent years. This theory has been extended from Hilbert spaces to Hilbert $C^{\ast}$-modules. In this paper, we introduce the concept of Controlled K-operator frame for the space…

Functional Analysis · Mathematics 2020-08-14 Abdeslam Touri , Samir Kabbaj

We study the decomposition of tensor products between a Steinberg module and a costandard module, both as a module for the algebraic group $G$ and when restricted to either a Frobenius kernel $G_r$ or a finite Chevalley group…

Representation Theory · Mathematics 2018-02-09 Tobias Kildetoft

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 $\Delta$ be a closed, cocompact subgroup of $G \times \widehat{G}$, where $G$ is a second countable, locally compact abelian group. Using localization of Hilbert $C^*$-modules, we show that the Heisenberg module…

Operator Algebras · Mathematics 2022-07-12 Are Austad , Ulrik Enstad

In this paper, we will generelize $b$-frames; a new concept of frames for Hilbert spaces, by $K$-$b$-frames. The idea is to take a sequence from a Banach space and see how it can be a frame for a Hilbert space. Instead of the scalar product…

Functional Analysis · Mathematics 2023-03-29 Chaimae Mezzat , Samir Kabbaj , Abdelkarim Bourouihia

In the first part of the paper we describe the dual \ell^2(A)^{\prime} of the standard Hilbert C*-module \ell^2(A) over an arbitrary (not necessarily unital) C*-algebra A. When A is a von Neumann algebra, this enables us to construct…

Operator Algebras · Mathematics 2019-12-19 Damir Bakic

In this paper, firstly we investigate conditions under which the action of an operator on a $K$-frame, remain again a $K$-frame for Hilbert module E. We also give a generalization of Douglas Theorem and we shall use it to prove the sum of…

Operator Algebras · Mathematics 2018-02-07 Gh. Abbaspour Tabadkan , A. A. Arefijamaal , M. Mahmoudieh

In this article, we study g-frames in Hilbert $C^*$-modules and investigate conditions under which the sum of two g-frames (or a g-frame and a g-Bessel sequence) remains a g-frame. We also address the stability of g-frames under certain…

Functional Analysis · Mathematics 2025-02-19 Abdellatif Lfounoune , Hafida Massit , Abdelilah Karara , Mohamed Rossafi

The concept of a bi-g-fusion frame for a Hilbert space, which is a generalizations of a controlled g-fusion frame, is introduced and an example is given. Finally, bi-g-fusion frame in tensor product of Hilbert spaces is considered.

Functional Analysis · Mathematics 2024-11-05 Prasenjit Ghosh , T. K. Samanta

A definition of frames for Krein spaces is proposed, which extends the notion of $J$-orthonormal basis of Krein spaces. A $J$-frame for a Krein space $(\HH, \K{\,}{\,})$ is in particular a frame for $\HH$ in the Hilbert space sense. But it…

Functional Analysis · Mathematics 2011-12-08 J. I. Giribet , A. Maestripieri , F. Martínez Pería , P. Massey

We study symmetric and antisymmetric tensor products of Hilbert-space operators, focusing on norms and spectra for some well-known classes favored by function-theoretic operator theorists. We pose many open questions that should interest…

Functional Analysis · Mathematics 2025-02-19 Stephan Ramon Garcia , Ryan O'Loughlin , Jiahui Yu

Let $K$ be a compact group, and let $\rho$ be a representation of $K$ on a Hilbert space $\mathcal{H}_\rho$. We classify invariant subspaces of $\mathcal{H}_\rho$ in terms of range functions, and investigate frames of the form $\{\rho(\xi)…

Classical Analysis and ODEs · Mathematics 2015-09-24 Joseph W. Iverson