Abstract

In this paper we begin the study of Schur analysis and of de Branges–Rovnyak spaces in the framework of Fueter hyperholomorphic functions. The difference with other approaches is that we consider the class of functions spanned by Appell-like polynomials. This approach is very efficient from various points of view, for example in operator theory, and allows us to make connections with the recently developed theory of slice polyanalytic functions. We tackle a number of problems: we describe a Hardy space, Schur multipliers and related results. We also discuss Blaschke functions, Herglotz multipliers and their associated kernels and Hilbert spaces. Finally, we consider the counterpart of the half-space case, and the corresponding Hardy space, Schur multipliers and Carathéodory multipliers.

Highlights

  • Two important function theories that allow to extend complex analysis and operator theory results to higher dimensions are the so-called monogenic and slice monogenic functions with values in a Clifford algebra

  • In this paper we begin the study of Schur analysis and of de Branges–Rovnyak spaces in the framework of Fueter hyperholomorphic functions

  • We tackle a number of problems: we describe a Hardy space, Schur multipliers and related results

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Summary

Introduction

Two important function theories that allow to extend complex analysis and operator theory results to higher dimensions are the so-called monogenic and slice monogenic functions with values in a Clifford algebra. In the case of quaternions these two theories are known as Fueter hyperholomorphic and slice regular or slice hyperholomorphic functions, respectively, see [32,38,39, 61,63]. We note that it is always possible to construct Fueter hyperholomorphic functions starting from slice regular ones using different techniques such as the Fueter mapping theorem [36,37], or using the Radon and dual Radon transforms, see [35]. The slice monogenicity does not imply, nor is implied by monogenicity

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Preliminaries
Quaternions and the Map χ
Various Notions of Hyperholomorphy and Homogeneous Polynomials
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Schur Algorithm
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Intrinsic Functions
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The Lurking Isometry
The Co-isometric Realization
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Blaschke Functions
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Rational Functions
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A Structure Theorem
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10. The Half-Space Case
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11. Schur Multipliers in the Half-Plane Setting
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12. Caratheodory Multipliers in the Half-Plane Setting
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13. A Table
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