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Let $\phi$ be a quasiconformal mapping, and let $T_\phi$ be the composition operator which maps $f$ to $f\circ\phi$. Since $\phi$ may not be bi-Lipschitz, the composition operator need not map Sobolev spaces to themselves. The study begins…

Classical Analysis and ODEs · Mathematics 2017-02-24 Marcos Oliva , Martí Prats

Let $X=(X,\mathcal{B},\mu)$ be a $\sigma$-finite measure space and \mbox{$f:X\to X$} be a measurable transformation such that the composition operator $T_f:\varphi\mapsto \varphi\circ f$ is a bounded linear operator acting on…

Dynamical Systems · Mathematics 2017-06-16 Udayan B. Darji , Benito Pires

In this article, we study Sobolev homeomorphisms and composition operators on homogeneous Lie groups. We prove that a measurable homeomorphism $\varphi: \Omega \to\widetilde{\Omega}$ belongs to the Sobolev space $L^{1}_{q}(\Omega;…

Analysis of PDEs · Mathematics 2025-09-11 Alexander Ukhlov

In this paper we study multiplication operators on Bergman spaces of high dimensional bounded domains and those von Neumann algebras induced by them via the geometry of domains and function theory of their symbols. In particular, using…

Operator Algebras · Mathematics 2024-05-31 Hansong Huang , Dechao Zheng

We give examples of composition operators $C\_\Phi$ on $H^2 (\D^2)$ showing that the condition $\|\Phi \|\_\infty = 1$ is not sufficient for their approximation numbers $a\_n (C\_\Phi)$ to satisfy $\lim\_{n \to \infty} [a\_n (C\_\Phi)…

Functional Analysis · Mathematics 2018-03-05 Daniel Li , Hervé Queffélec , Luis Rodríguez-Piazza

Let $B_d$ denote the unit ball of $\mathbb{C}^d$, $d\ge 1$. Given a holomorphic function $\varphi: B_d \to B_1$, we study the corresponding family $\sigma_\alpha[\varphi]$, $\alpha\in\partial B_1$, of Clark measures on the unit sphere…

Complex Variables · Mathematics 2019-04-10 Aleksei B. Aleksandrov , Evgueni Doubtsov

Let $\Omega\subset \mathbb{C}^n$ for $n\geq 2$ be a bounded pseudoconvex domain with a $C^2$-smooth boundary. We study the compactness of composition operators on the Bergman spaces of smoothly bounded convex domains. We give a partial…

Complex Variables · Mathematics 2019-05-01 Timothy G. Clos

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

For the Reshetnyak-class homeomorphisms $\varphi:\Omega\to Y$, where~$\Omega$ is a~domain in some Carnot group and~$Y$ is a~metric space, we obtain an~equivalent description as the mappings which induce the bounded composition operator $$…

Analysis of PDEs · Mathematics 2025-07-15 Pavlov S. V. , Vodopyanov S. K

We construct an analytic self-map $\Phi$ of the bidisk ${\mathbb D}^2$ whose image touches the distinguished boundary, but whose approximation numbers of the associated composition operator on $H^2 ({\mathbb D}^2)$ are small in the sense…

Functional Analysis · Mathematics 2019-01-23 Daniel Li , Hervé Queffélec , Luis Rodríguez-Piazza

Let $\varphi$ be a univalent non-elliptic self-map of the unit disc $\mathbb D$ and let $(\psi_{t})$ be a continuous one-parameter semigroup of holomorphic functions in $\mathbb D$ such that $\psi_{1}\neq\mathrm{id}_{\mathbb D}$ commutes…

Complex Variables · Mathematics 2025-12-11 Manuel D. Contreras , Santiago Díaz-Madrigal , Pavel Gumenyuk

On the space of bounded analytic functions and the Bloch space on the unit disk, we study the compact intertwining relations for composition operators, whose intertwining operators are Volterra type operators. Further, we consider the…

Functional Analysis · Mathematics 2018-09-17 Ce-Zhong Tong , Cheng Yuan , Ze-Hua Zhou

In this work, the density in $H(b)$ spaces of finitely connected planar domains and the boundedness of composition operators on these function spaces are studied. Density of the algebra $\mathcal{A}(D)$ is considered for both in the cases…

Functional Analysis · Mathematics 2022-08-09 Sibel Sahin

The paper considers bounded linear radial operators on the polyanalytic Fock spaces $\mathcal{F}_n$ and on the true-polyanalytic Fock spaces $\mathcal{F}_{(n)}$. The orthonormal basis of normalized complex Hermite polynomials plays a…

Operator Algebras · Mathematics 2020-09-25 Egor A. Maximenko , Ana María Tellería-Romero

In this article, we will give a characterization of Banach bimodules over $C^*$-algebras of compact operators that arises from operator spaces as well as a characterization of (F)-Banach bundles amongst all (H)-Banach bundles over a…

Operator Algebras · Mathematics 2007-05-23 Chi-Keung Ng

In this article, we completely characterize the complex symmetry, cyclicity and hypercyclicity of composition operators $C_\phi f=f\circ\phi$ induced by affine self-maps $\phi$ of the right half-plane $\mathbb{C}_+$ on the Hardy-Hilbert…

Functional Analysis · Mathematics 2019-10-14 S. Waleed Noor , Osmar R. Severiano

We completely characterize the spectrum of a weighted composition operator $W_{\psi, \varphi}$ on $H^{2}(\mathbb{D})$ when $\varphi$ has Denjoy-Wolff point $a$ with $0<|\varphi '(a)|< 1$, the iterates, $\varphi_{n}$, converge uniformly to…

Functional Analysis · Mathematics 2017-05-17 Carl Cowen , Eungil Ko , Derek Thompson , Feng Tian

We obtain exhaustive results and treat in a unified way the question of boundedness, compactness, and weak compactness of composition operators from the Bloch space into any space from a large family of conformally invariant spaces that…

Functional Analysis · Mathematics 2016-11-07 Manuel D. Contreras , Santiago Diaz-Madrigal , Dragan Vukotic

Let $K$ be a compact metric space and let $\varphi: K \to K$ be continuous. We study C*-algebra $\mathcal{MC}_\varphi$ generated by all multiplication operators by continuous functions on $K$ and a composition operator $C_\varphi$ induced…

Operator Algebras · Mathematics 2019-11-26 Hiroyasu Hamada

We prove a simple criterion for essential normality of composition operators on the Hardy space induced by maps in a reasonably large class of analytic self-maps of the unit disk. By combining this criterion with boundary…

Functional Analysis · Mathematics 2015-04-03 Mor Katz