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In this paper, we will introduce the concept of a continuous K-biframe for Hilbert spaces and we present various examples of continuous K-biframes. Furthermore, we investigate their characteristics from the perspective of operator theory by…

Functional Analysis · Mathematics 2024-02-27 Abdelilah Karara , Mohamed Rossafi

The finite Hilbert transform $T$ is a classical (singular) kernel operator which is continuous in every rearrangement invariant space $X$ over $(-1,1)$ having non-trivial Boyd indices. For $X=L^p$, $1<p<\infty$, this operator has been…

Functional Analysis · Mathematics 2023-04-03 G. P. Curbera , S. Okada , W. J. Ricker

Let $B(H)$ be the algebra of all bounded operators on a Hilbert space $H$. Let $T=V|T|$ be the polar decomposition of an operator $T\in B(H)$. The mean transform of $T$ is defined by $M(T)=\frac{T+|T|V}{2}$. In this paper, we discuss…

Functional Analysis · Mathematics 2022-07-28 Fadil Chabbabi , Maëva Ostermann

We develop a number of inequalities to obtain bounds for the numerical radius of a bounded linear operator defined on a complex Hilbert space using the properties of $t$-Aluthge transform. We show that the bounds obtained are sharper than…

Functional Analysis · Mathematics 2024-08-13 Santanu bag , Pintu Bhunia , Kallol Paul

In this paper we study the Hilbert transformations over $L^2(\mathbb{R})$ and $L^2(\mathbb{T})$ from the viewpoint of symmetry. For a linear operator over $L^2(\mathbb{R})$ commutative with the ax+b group we show that the operator is of the…

Complex Variables · Mathematics 2017-11-15 Pei Dang , Hua Liu , Tao Qian

In this Work, We introduce the concept of $\ast$-operator frame, which is a generalization of $\ast$-frames in Hilbert pro-$C^{\ast}$-modules, and we establish some results, we also study the tensor product of $\ast$-operator frame for…

Functional Analysis · Mathematics 2021-11-19 Roumaissae Eljazzar , Mohamed Rossafi

A classical result of Duffin and Schaeffer gives conditions under which a discrete collection of characters on $\mathbb{R}$, restricted to $E = (-1/2, 1/2)$, forms a Hilbert-space frame for $L^2(E)$. For the case of characters with period…

Representation Theory · Mathematics 2014-09-30 Benjamin Robinson , William Moran , Douglas Cochran , Stephen D. Howard

Continuous frames and tensor products are important topics in theoretical physics. This paper combines those concepts. We derive fundamental properties of continuous frames for tensor product of Hilbert spaces. This includes, for example,…

Functional Analysis · Mathematics 2022-03-23 Peter Balazs , Nenad Teofanov

In this paper, we present intriguing findings that characterize both the closed (unbounded) and bounded EP operators on Hilbert spaces. Additionally, we demonstrate the result $\gamma(T) \leq r(T)$, where $T$ is a bounded EP operator, and…

Functional Analysis · Mathematics 2024-12-10 Arup Majumdar , P. Sam Johnson

Atomic system in fuzzy Hilbert space is introduced and the existence of the fuzzy atomic systems for a strongly fuzzy bounded linear operator is studied. The notion of a K-frame in fuzzy Hilbert space is presented and some of their…

General Mathematics · Mathematics 2025-06-17 Prasenjit Ghosh , Jayanta Ghosh , T. K. Samanta

Gavruta introduced $K$-frames for Hilbert spaces to study atomic systems with respect to a bounded linear operator. There are many differences between K-frames and standard frames, so we study weaving properties of K-frames. Two frames…

Functional Analysis · Mathematics 2018-06-08 Deepshikha , Lalit K. Vashisht

In this paper, the concept of grand variable Herz-Morrey-Hardy spaces are introduced. We also establish the atomic characterization of these spaces. As an application the authors investigate the continuity of a few singular integral…

Functional Analysis · Mathematics 2025-08-26 Babar Sultan , Amjad Hussain , Mehvish Sultan

In this paper we show that every conjugation $C$ on the Hardy-Hilbert space $H^{2}$ is of type $C=T^{*}C_{1}T$, where $T$ is an unitary operator and $C_{1}f\left(z\right)=\overline{f\left(\overline{z}\right)}$, with $f\in H^{2}$. In the…

Functional Analysis · Mathematics 2022-02-01 Marcos S. Ferreira

Importance of theorem dedicated to isomorphisms consist in statement that they allow to identify different mathematical objects which have something common from the point of view of certain model. This paper considers morphisms of \Ts…

Differential Geometry · Mathematics 2008-03-19 Aleks Kleyn

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

Frames in a separable quaternionic Hilbert space were introduced and studied in [17] to have more applications. In this paper, we extend the study of frames in quaternionic Hilbert spaces and introduce different types of duals of a frame in…

Functional Analysis · Mathematics 2018-03-16 S. K. Sharma , Ghanshyam Singh , Soniya Sahu

Fusion frames are a very active area of research today because of their myriad of applications in pure mathematics, applied mathematics, engineering, medicine, signal and image processing and much more. They provide a great flexibility for…

We introduce the concept of essential numerical range $W_{\!e}(T)$ for unbounded Hilbert space operators $T$ and study its fundamental properties including possible equivalent characterizations and perturbation results. Many of the…

Spectral Theory · Mathematics 2019-07-24 Sabine Bögli , Marco Marletta , Christiane Tretter

In this article, we study properties of multilinear Fourier integral operators on weighted modulation spaces. In particular, using the theory of Gabor frames, we study boundedness of multilinear Fourier integral operators on products of…

Functional Analysis · Mathematics 2023-02-22 Aparajita Dasgupta , Lalit Mohan , Shyam Swarup Mondal

If $g$ is an analytic function in the unit disc $\D $ we consider the generalized Hilbert operator $\hg$ defined by {equation*}\label{H-g} \mathcal{H}_g(f)(z)=\int_0^1f(t)g'(tz)\,dt. {equation*} We study these operators acting on classical…

Complex Variables · Mathematics 2018-04-12 Petros Galanopoulos , Daniel Girela , José Ángel Peláez , Aristomenis Siskakis