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In this work a possibility of a decomposition of a bounded operator which acts in a Hilbert space $H$ as a product of a J-unitary and a J-self-adjoint operators is studied, $J$ is a conjugation (an antilinear involution). Decompositions of…

Functional Analysis · Mathematics 2009-10-15 Sergey M. Zagorodnyuk

Let $H^\infty$ denote the algebra of all bounded analytic functions on the unit disk. It is well-known that every (algebra) automorphism of $H^\infty$ is a composition operator induced by disc automorphism. Maurya et al., (J. Math. Anal.…

Complex Variables · Mathematics 2025-06-23 Kanha Behera , Rahul Maurya , P. Muthukumar

We give different types of new characterizations for the boundedness and essential norms of generalized weighted composition operators between Zygmund type spaces. Consequently, we obtain new characterizations for the compactness of such…

Functional Analysis · Mathematics 2019-04-01 Mostafa Hassanlou , Amir H. Sanatpour

In this paper we investigate some basic results on the slice regular Besov spaces of hyperholomorphic functions on the unit ball $\mathbb{B}.$ We also characterize the boundedness, compactness and find the essential norm estimates of…

Functional Analysis · Mathematics 2016-09-09 Sanjay Kumar , Khalid Manzoor

Commutators of a large class of bilinear operators and multiplication by functions in a certain subspace of the space of functions of bounded mean oscillations are shown to be jointly compact. Under a similar commutation, fractional…

Classical Analysis and ODEs · Mathematics 2013-10-16 Árpád Bényi , Wendolín Damián , Kabe Moen , Rodolfo H. Torres

We prove the following localization for compactness of Hankel operators on Bergman spaces. Assume that D is a bounded pseudoconvex domain in C^n, p is a boundary point of D and B(p,r) is a ball centered at p with radius r so that U=D\cap…

Complex Variables · Mathematics 2021-03-08 Sonmez Sahutoglu

We study the essential spectrum and Fredholm properties of integral and pseudodiferential operators associated to (maybe non-commutative) locally compact groups G. The techniques involve crossed product C*-algebras. We extend previous…

Spectral Theory · Mathematics 2015-10-20 Marius Mantoiu

We characterize the weighted composition-differentiation operators $D_{\mfn,\psi,\varphi}$ acting on $\mathcal{H}_\gamma(\mathbb{D}^d)$ over the polydisk $\mathbb{D}^d$ which are complex symmetric with respect to the conjugation…

Functional Analysis · Mathematics 2025-05-27 Vasudevarao Allu , Satyajit Sahoo

In this paper the necessary and sufficient conditions for the product of composition operators to be isometry are obtained on weighted Bergman space. With the help of a counter example we also proved that unlike on…

Functional Analysis · Mathematics 2021-07-07 Anuradha Gupta , Geeta Yadav

Continuing the study initiated in our earlier article [7], this paper aims to characterize various continuity properties of nonlinear composition operators acting on some sequence spaces, giving special attention to the space of sequences…

Functional Analysis · Mathematics 2025-05-13 Daria Bugajewska , Piotr Kasprzak

We study mean ergodic composition operators on infinite dimensional spaces of holomorphic functions of different types when defined on the unit ball of a Banach or a Hilbert space: that of all holomorphic functions, that of holomorphic…

Functional Analysis · Mathematics 2021-03-04 David Jornet , Daniel Santacreu , Pablo Sevilla-Peris

To a generalized tight continuous frame in a Hilbert space $\H$ indexed by a locally compact space $\Si$ endowed with a Radon measure, one associates a coorbit theory converting spaces of functions on $\Si$ in spaces of vectors comparable…

Functional Analysis · Mathematics 2014-06-30 M. Mantoiu , D. Parra

We describe the norm-closures of the set $\mathfrak{C}_{\mathfrak{E}}$ of commutators of idempotent operators and the set $\mathfrak{E} - \mathfrak{E}$ of differences of idempotent operators acting on a finite-dimensional complex Hilbert…

Functional Analysis · Mathematics 2022-05-19 Laurent W. Marcoux , Heydar Radjavi , Yuanhang Zhang

We consider various classes of bounded operators on the Fock space $F^2$ of Gaussian square integrable entire functions over the complex plane. These include Toeplitz (type) operators, weighted composition operators, singular integral…

Functional Analysis · Mathematics 2024-06-03 Wolfram Bauer , Robert Fulsche , Miguel Angel Rodriguez Rodriguez

We show that a composition operator induced by an analytic self-map of the unit disc in the complex plane is weakly compact on the space BMOA precisely when the operator is compact on BMOA. As a crucial step we simplify the compactness…

Functional Analysis · Mathematics 2010-01-22 Jussi Laitila , Pekka J. Nieminen , Eero Saksman , Hans-Olav Tylli

We study weighted composition operators acting between Fock spaces. The following results are obtained: (1) Criteria for the boundedness and compactness; (2) Characterizations of compact differences and essential norm; (3) Complete…

Complex Variables · Mathematics 2017-04-13 Pham Trong Tien , Le Hai Khoi

We prove an abstract theorem on keeping the compactness property of a linear operator after interpolation in Banach spaces. No analytical presentation of operators, spaces and interpolation functor is required. We use only some little-known…

Functional Analysis · Mathematics 2021-09-14 Evgeniy Pustylnik

We consider compact locally symmetric spaces $\Gamma\backslash G/H$ where $G/H$ is a non-compact semisimple symmetric space and $\Gamma$ is a discrete subgroup of $G$. We discuss some features of the joint spectrum of the (commutative)…

Representation Theory · Mathematics 2021-04-13 Salah Mehdi , Martin Olbrich

This paper presents a systematic operator theory approach for abstract structure of Banach measure algebras over coset spaces of compact subgroups. Let $H$ be a compact subgroup of a locally compact group $G$ and $G/H$ be the left coset…

Functional Analysis · Mathematics 2019-05-02 Arash Ghaani Farashahi

In this paper we investigate the numerical ranges of composition operators whose symbols are elliptic automorphisms of finite orders, on the Hilbert Hardy space $H^2(D)$.

Functional Analysis · Mathematics 2023-02-22 Yong-Xin Gao , Ze-Hua Zhou