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Two themes drive this article: identifying the structure necessary to formulate quaternionic operator theory and revealing the relation between complex and quaternionic operator theory. The theory of quaternionic right linear operators is…

Spectral Theory · Mathematics 2018-03-29 Jonathan Gantner

The Bargmann-Fock space(or Fock space for short) is a fundamental example of reproducing kernel Hilbert spaces that has found fascinating applications across multiple fields of current interest, including quantum mechanics, time-frequency…

Complex Variables · Mathematics 2025-10-14 Kamal Diki

In this paper we develop a theory of slice regular functions on a real alternative algebra $A$. Our approach is based on a well--known Fueter's construction. Two recent function theories can be included in our general theory: the one of…

Complex Variables · Mathematics 2018-07-02 Riccardo Ghiloni , Alessandro Perotti

The aim of this paper is to provide and prove the most general Cauchy integral formula for slice regular functions and for C^1 functions on a real alternative *-algebra. Slice regular functions represent a generalization of the classical…

Complex Variables · Mathematics 2016-02-12 Riccardo Ghiloni , Alessandro Perotti , Vincenzo Recupero

In this paper, a new axiomatization for unbounded functional calculi is proposed and the associated theory is elaborated comprising, among others, uniqueness and compatibility results and extension theorems of algebraic and topological…

Functional Analysis · Mathematics 2020-09-11 Markus Haase

In this paper we begin the study of Schur analysis and 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…

Functional Analysis · Mathematics 2021-08-03 Daniel Alpay , Fabrizio Colombo , Kamal Diki , Irene Sabadini

Slice Fueter-regular functions, originally called slice Dirac-regular functions, are generalized holomorphic functions defined over the octonion algebra $\mathbb{O}$, recently introduced by M. Jin, G. Ren and I. Sabadini. A function…

Complex Variables · Mathematics 2019-11-15 Riccardo Ghiloni

We prove quadratic estimates for complex perturbations of Dirac-type operators, and thereby show that such operators have a bounded functional calculus. As an application we show that spectral projections of the Hodge--Dirac operator on…

Spectral Theory · Mathematics 2009-11-10 Andreas Axelsson , Stephen Keith , Alan McIntosh

In this paper, we first prove that the S-spectrum of a bounded right quaternionic linear operator on a two-sided quaternionic Banach space is a union of the spectrum of some bounded linear operators on a complex Banach space. Furthermore,…

Functional Analysis · Mathematics 2020-05-21 El Hassan Benabdi , Mohamed Barraa

A physically more adequate definition of a quaternionic holomorphic (H-holomorphic) function of one quaternionic variable compared to known ones and a quaternionic generalization of Cauchy-Riemann's equations are presented. At that a class…

Complex Variables · Mathematics 2024-02-14 Michael Parfenov

Polyharmonic functions f of infinite order and type {\tau} on annular regions are systematically studied. The first main result states that the Fourier-Laplace coefficients f_{k,l}(r) of a polyharmonic function f of infinite order and type…

Analysis of PDEs · Mathematics 2012-07-24 Ognyan Kounchev , Hermann Render

The two function theories of monogenic and of slice monogenic functions have been extensively studied in the literature and were developed independently; the relations between them, e.g. via Fueter mapping and Radon transform, have been…

Complex Variables · Mathematics 2024-12-19 Zhenghua Xu , Irene Sabadini

In this paper we develop a functional calculus for bounded operators defined on quaternionic Banach spaces. This calculus is based on the notion of slice-regularity, see \cite{gs}, and the key tools are a new resolvent operator and a new…

Spectral Theory · Mathematics 2010-03-30 F. Colombo , G. Gentili , I. Sabadini , D. C. Struppa

Recently, the concept of generalized partial-slice monogenic (or regular) functions has been introduced and studied over Clifford algebras and octonions, respectively. In this paper, we further develop the theory of generalized…

Complex Variables · Mathematics 2026-03-17 Qinghai Huo , Irene Sabadini , Zhenghua Xu

We present a Riesz-like hyperholomorphic functional calculus for a set of non-commuting operators based on the Clifford analysis. Applications to the quantum field theory are described. Keywords: Functional calculus, Weyl calculus, Riesz…

funct-an · Mathematics 2016-11-03 Vladimir V. Kisil , Enrique Ramírez de Arellano

The concept of slice regular function over the real algebra $\mathbb{H}$ of quaternions is a generalization of the notion of holomorphic function of a complex variable. Let $\Omega$ be an open subset of $\mathbb{H}$, which intersects…

Complex Variables · Mathematics 2020-11-20 Riccardo Ghiloni

The Fueter-Sce theorem provides a procedure to obtain axially monogenic functions, which are in the kernel of generalized Cauchy-Riemann operator in $ \mathbb{R}^{n+1}$. This result is obtained by using two operators. The first one is the…

Functional Analysis · Mathematics 2023-05-12 Antonino De Martino , Kamal Diki , Ali Guzmán Adán

Quaternionic analysis offers a function theory focused on the concept of $\psi-$hyperholomorphic functions defined as null solutions of the $\psi-$Fueter operator, where $\psi$ is an arbitrary orthogonal base (called structural set) of…

Complex Variables · Mathematics 2021-11-10 José Oscar González-Cervantes , Juan Bory-Reyes

We push the definition of multiple operator integrals (MOIs) into the realm of unbounded operators, using the pseudodifferential calculus from the works of Connes and Moscovici, Higson, and Guillemin. This in particular provides a natural…

Functional Analysis · Mathematics 2024-04-26 Eva-Maria Hekkelman , Edward McDonald , Teun D. H. van Nuland

In this paper we study properties of hyperholomorphic functions on commutative finite algebras. It is investigated the Cauchy-Riemann type conditions for hyperholomorphic functions. We prove that a hyperholomorphic function on a commutative…

Complex Variables · Mathematics 2007-05-23 Anatoliy A. Pogorui