On Cauchy dual operator and duality for Banach spaces of analytic functions

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1. Verfasser: Pietrzycki, Paweł
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Veröffentlicht: 2020
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author Pietrzycki, Paweł
author_facet Pietrzycki, Paweł
contents In this paper, two related types of dualities are investigated. The first is the duality between left-invertible operators and the second is the duality between Banach spaces of vector-valued analytic functions. We will examine a pair ($\mathcal{B},Ψ)$ consisting of a reflexive Banach spaces $\mathcal{B}$ of vector-valued analytic functions on which a left-invertible multiplication operator acts and an operator-valued holomorphic function $Ψ$. We prove that there exist a dual pair ($\mathcal{B}^\prime,Ψ^\prime)$ such that the space $\mathcal{B}^\prime$ is unitarily equivalent to the space $\mathcal{B}^*$ and the following intertwining relations hold \begin{equation*} \mathscr{L} \mathcal{U} = \mathcal{U}\mathscr{M}_z^* \quad\text{and}\quad \mathscr{M}_z\mathcal{U} = \mathcal{U} \mathscr{L}^*, \end{equation*} where $\mathcal{U}$ is the unitary operator between $\mathcal{B}^\prime$ and $\mathcal{B}^*$. In addition we show that $Ψ$ and $Ψ^\prime$ are connected through the relation\begin{equation*} \langle(Ψ^\prime( \bar{z}) e_1) (λ),e_2\rangle= \langle e_1,(Ψ( \bar{ λ}) e_2)(z)\rangle \end{equation*} for every $e_1,e_2\in E$, $z\in \varOmega$, $λ\in \varOmega^\prime$. If a left-invertible operator $T$ satisfies certain conditions, then both $T$ and the Cauchy dual operator $T^\prime$ can be modelled as a multiplication operator on reproducing kernel Hilbert spaces of vector-valued analytic functions $\mathscr{H}$ and $\mathscr{H}^\prime$, respectively. We prove that Hilbert space of the dual pair of $(\mathscr{H},Ψ)$ coincide with $\mathscr{H}^\prime$, where $Ψ$ is a certain operator-valued holomorphic function. Moreover, we characterize when the duality between spaces $\mathscr{H}$ and $\mathscr{H}^\prime$ obtained by identifying them with $\mathcal{H}$ is the same as the duality obtained from the Cauchy pairing.
format Preprint
id arxiv_https___arxiv_org_abs_2007_01858
institution arXiv
publishDate 2020
record_format arxiv
spellingShingle On Cauchy dual operator and duality for Banach spaces of analytic functions
Pietrzycki, Paweł
Functional Analysis
Complex Variables
In this paper, two related types of dualities are investigated. The first is the duality between left-invertible operators and the second is the duality between Banach spaces of vector-valued analytic functions. We will examine a pair ($\mathcal{B},Ψ)$ consisting of a reflexive Banach spaces $\mathcal{B}$ of vector-valued analytic functions on which a left-invertible multiplication operator acts and an operator-valued holomorphic function $Ψ$. We prove that there exist a dual pair ($\mathcal{B}^\prime,Ψ^\prime)$ such that the space $\mathcal{B}^\prime$ is unitarily equivalent to the space $\mathcal{B}^*$ and the following intertwining relations hold \begin{equation*} \mathscr{L} \mathcal{U} = \mathcal{U}\mathscr{M}_z^* \quad\text{and}\quad \mathscr{M}_z\mathcal{U} = \mathcal{U} \mathscr{L}^*, \end{equation*} where $\mathcal{U}$ is the unitary operator between $\mathcal{B}^\prime$ and $\mathcal{B}^*$. In addition we show that $Ψ$ and $Ψ^\prime$ are connected through the relation\begin{equation*} \langle(Ψ^\prime( \bar{z}) e_1) (λ),e_2\rangle= \langle e_1,(Ψ( \bar{ λ}) e_2)(z)\rangle \end{equation*} for every $e_1,e_2\in E$, $z\in \varOmega$, $λ\in \varOmega^\prime$. If a left-invertible operator $T$ satisfies certain conditions, then both $T$ and the Cauchy dual operator $T^\prime$ can be modelled as a multiplication operator on reproducing kernel Hilbert spaces of vector-valued analytic functions $\mathscr{H}$ and $\mathscr{H}^\prime$, respectively. We prove that Hilbert space of the dual pair of $(\mathscr{H},Ψ)$ coincide with $\mathscr{H}^\prime$, where $Ψ$ is a certain operator-valued holomorphic function. Moreover, we characterize when the duality between spaces $\mathscr{H}$ and $\mathscr{H}^\prime$ obtained by identifying them with $\mathcal{H}$ is the same as the duality obtained from the Cauchy pairing.
title On Cauchy dual operator and duality for Banach spaces of analytic functions
topic Functional Analysis
Complex Variables
url https://arxiv.org/abs/2007.01858