On some questions about composition operators on weighted Hardy spaces

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Main Authors: Lefèvre, Pascal, Li, Daniel, Queffélec, Hervé, Rodríguez-Piazza, Luis
Format: Preprint
Published: 2023
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author Lefèvre, Pascal
Li, Daniel
Queffélec, Hervé
Rodríguez-Piazza, Luis
author_facet Lefèvre, Pascal
Li, Daniel
Queffélec, Hervé
Rodríguez-Piazza, Luis
contents We first consider some questions raised by N. Zorboska in her thesis. In particular she asked for which sequences $β$ every symbol $φ\colon \mathbb{D} \to \mathbb{D}$ with $φ\in H^2 (β)$ induces a bounded composition operator $C_ϕ$ on the weighted Hardy space $H^2 (β)$. We give partial answers and investigate when $H^2 (β)$ is an algebra. We answer negatively another question in showing that there are a sequence $β$ and $φ\in H^2 (β)$ such that $\| φ\|_\infty < 1$ and the composition operator $C_φ$ is not bounded on $H^2 (β)$. In a second part, we show that for $p \neq 2$, no automorphism of $\mathbb{D}$, except those that fix $0$, induces a bounded composition operator on the Beurling-Sobolev space $\ell^p_A$, and even on any weighted version of this space.
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id arxiv_https___arxiv_org_abs_2311_01062
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle On some questions about composition operators on weighted Hardy spaces
Lefèvre, Pascal
Li, Daniel
Queffélec, Hervé
Rodríguez-Piazza, Luis
Functional Analysis
We first consider some questions raised by N. Zorboska in her thesis. In particular she asked for which sequences $β$ every symbol $φ\colon \mathbb{D} \to \mathbb{D}$ with $φ\in H^2 (β)$ induces a bounded composition operator $C_ϕ$ on the weighted Hardy space $H^2 (β)$. We give partial answers and investigate when $H^2 (β)$ is an algebra. We answer negatively another question in showing that there are a sequence $β$ and $φ\in H^2 (β)$ such that $\| φ\|_\infty < 1$ and the composition operator $C_φ$ is not bounded on $H^2 (β)$. In a second part, we show that for $p \neq 2$, no automorphism of $\mathbb{D}$, except those that fix $0$, induces a bounded composition operator on the Beurling-Sobolev space $\ell^p_A$, and even on any weighted version of this space.
title On some questions about composition operators on weighted Hardy spaces
topic Functional Analysis
url https://arxiv.org/abs/2311.01062