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In this paper we will show how the boundedness condition for the weighted composition operators on a class of spaces of analytic functions on the open right complex half-plane called Zen spaces (which include the Hardy spaces and weighted…

Functional Analysis · Mathematics 2017-02-09 Andrzej S. Kucik

We present the following reflexivity-like result concerning the automorphism group of the $C^*$-algebra B(H), H being a separable Hilbert space. Let $\phi:B(H)\to B(H)$ be a multiplicative map (no linearity or continuity is assumed) which…

Operator Algebras · Mathematics 2007-05-23 Lajos Molnar

On a complex ellipsoid in $\mathbb{C}^n$, we show that there is no nonzero Hankel operator with an anti-holomorphic symbol that is Hilbert-Schmidt.

Complex Variables · Mathematics 2013-05-31 Mehmet Çelik , Yunus E. Zeytuncu

We present complete characterizations of Toeplitz operators that are complex symmetric. This follows as a by-product of characterizations of conjugations on Hilbert spaces. Notably, we prove that every conjugation admits a canonical…

Functional Analysis · Mathematics 2022-07-27 Sudip Ranjan Bhuia , Deepak Pradhan , Jaydeb Sarkar

Let $\lambda_i (i=1,...,k)$ be any nonzero complex scalars and $\varphi_i (i=1,..,k)$ be any analytic self-maps of the unit disk $\mathbb{D}$. We show that the operator $\sum_{i=1}^k\lambda_iC_{\varphi_i}$ is compact on the Bloch space…

Complex Variables · Mathematics 2018-02-13 Yecheng Shi , Songxiao Li

We characterize Hilbert-Schmidt Hankel operators on the Bergman spaces of smooth bounded strongly pseudoconvex domains in $\mathbb{C}^n$ for $n \geq 2$. We consider harmonic symbols of class $C^3$ up to the closure of the domain and show…

Complex Variables · Mathematics 2026-03-27 Timothy G. Clos

We give estimates for the approximation numbers of composition operators on $H^2$, in terms of some modulus of continuity. For symbols whose image is contained in a polygon, we get that these approximation numbers are dominated by $\e^{- c…

Functional Analysis · Mathematics 2012-06-07 Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza

We give examples of results on composition operators connected with lens maps. The first two concern the approximation numbers of those operators acting on the usual Hardy space $H^2$. The last ones are connected with Hardy-Orlicz and…

Functional Analysis · Mathematics 2012-01-04 Pascal Lefèvre , Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza

We obtain necessary and sufficient conditions for the composition and weighted composition operator and product of composition operators to be isometry and unitary on $H_{E}(\xi).$ With the help of counter example we also prove that the…

Functional Analysis · Mathematics 2021-10-25 Anuradha Gupta , Geeta Yadav

Conditions for a composition operator on the Hardy space of the disk to have closed range or be similar to an isometry are well known. We provide such conditions for composition operators on the Hardy space of the upper half-plane. We also…

Functional Analysis · Mathematics 2012-05-08 Hari Bercovici , Dan Timotin

We study when multiplication by a weight can turn a non-compact composition operator on H 2 into a compact operator, and when it can be in Schatten classes. The q-summing case in H p is considered. We also study when this multiplication can…

Functional Analysis · Mathematics 2019-04-16 Pascal Lefèvre , Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza

Using recent characterizations of the compactness of composition operators on Hardy-Orlicz and Bergman-Orlicz spaces on the ball, we first show that a composition operator which is compact on every Hardy-Orlicz (or Bergman-Orlicz) space has…

Functional Analysis · Mathematics 2011-01-20 Stéphane Charpentier

Let $ \mathcal{H}(\mathbb{D}) $ be the class of all holomorphic functions in the unit disk $ \mathbb{D} $. We aim to explore the complex symmetry exhibited by generalized weighted composition-differentiation operators, denoted as $L_{n,…

Complex Variables · Mathematics 2023-08-28 Molla Basir Ahamed , Taimur Rahman

In this work we propose composition products in the class of complex harmonic functions so that the composition of two such functions is again a complex harmonic function. From here we begin the study of the iterations of the functions of…

Complex Variables · Mathematics 2022-02-08 Luis E. Benítez , Raúl Felipe

We study the cyclic and supercyclic dynamical properties of weighted composition operators on the Fock space $\mathcal{F}_2$. A complete characterization of cyclicity which depends on the derivative of the symbol for the composition…

Complex Variables · Mathematics 2019-01-08 Tesfa Mengestie

In this paper we define $\lambda$-hyponormal operators on an infinite dimensional Hilbert space $\mathcal{H}$ and find a class of $\lambda$-hyponormal operators that can not be hypercyclic. Also, we study closedness of range and…

Functional Analysis · Mathematics 2025-08-07 Y. Estaremi , M. S. Al Ghafri , and S. Shamsigamchi

A characterization of those points in the unit disc which belong to the spectrum of a composition operator $C_{\varphi}$, defined by a rotation $\varphi(z)=rz$ with $|r|=1$, on the space $H_0(\mathbb{D})$ of all analytic functions on the…

Functional Analysis · Mathematics 2020-01-15 José Bonet

We describe the C*-algebra generated by an irreducible Toeplitz operator $T_{\psi}$, with continuous symbol $\psi $ on the unit circle $\mathbb{T}$, and finitely many composition operators on the Hardy space $H^2$ induced by certain…

Operator Algebras · Mathematics 2014-08-06 Masoud Salehi Sarvestani , Massoud Amini

We show that a composition operator on weighted Bergman spaces $\mathcal{A}_{\mu}^p$ is invertible if and only if it is Fredholm if and only if it is an isometry.

Functional Analysis · Mathematics 2014-04-15 Maxime Bailleul

For approximation numbers $a_n (C_\phi)$ of composition operators $C_\phi$ on weighted analytic Hilbert spaces, including the Hardy, Bergman and Dirichlet cases, with symbol $\phi$ of uniform norm $< 1$, we prove that $\lim_{n \to \infty}…

Functional Analysis · Mathematics 2014-07-09 Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza