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The theory of quaternionic slice regular functions was introduced in 2006 and successfully developed for about a decade over symmetric slice domains, which appeared to be the natural setting for their study. Some recent articles paved the…

Complex Variables · Mathematics 2021-05-04 Graziano Gentili , Caterina Stoppato

A promising theory of quaternion-valued functions of one quaternionic variable, now called slice regular functions, has been introduced in 2006. The basic examples of slice regular functions are power series centered at 0 on their balls of…

Complex Variables · Mathematics 2012-09-11 Caterina Stoppato

The aim of this paper is to prove that a large class of quaternionic slice regular functions result to be (ramified) covering maps. By means of the topological implications of this fact and by providing further topological structures, we…

Complex Variables · Mathematics 2022-06-07 Amedeo Altavilla , Samuele Mongodi

After Gentili and Struppa introduced in 2006 the theory of quaternionic slice regular function, the theory has focused on functions on the so-called slice domains. The present work defines the class of speared domains, which is a rather…

Complex Variables · Mathematics 2024-06-10 Riccardo Ghiloni , Caterina Stoppato

The theory of slice regular functions of a quaternionic variable on the unit ball of the quaternions was introduced by Gentili and Struppa in 2006 and nowadays it is a well established function theory, especially in view of its applications…

Functional Analysis · Mathematics 2023-06-22 José Oscar González-Cervantes , Juan Bory-Reyes , Irene Sabadini

The aim of this paper is to introduce the $H^\infty$-functional calculus for harmonic functions over the quaternions. More precisely, we give meaning to Df(T) for unbounded sectorial operators T and polynomially growing functions of the…

Functional Analysis · Mathematics 2023-10-20 Antonino de Martino , Stefano Pinton , Peter Schlosser

The theory of slice regular functions of a quaternionic variable extends the notion of holomorphic function to the quaternionic setting. This theory, already rich of results, is sometimes surprisingly different from the theory of…

Complex Variables · Mathematics 2014-04-14 Graziano Gentili , Giulia Sarfatti

The main goal of this work is classifying the singularities of slice regular functions over a real alternative *-algebra A. This function theory has been introduced in 2011 as a higher-dimensional generalization of the classical theory of…

Complex Variables · Mathematics 2017-03-16 Riccardo Ghiloni , Alessandro Perotti , Caterina Stoppato

A new approach to normal operators in real Hilbert spaces is discussed, and a spectral representation is obtained, derived directly from the complex case. The results are then applied to quaternionic normal operators, regarded as a special…

Functional Analysis · Mathematics 2025-07-28 Florian-Horia Vasilescu

In this paper we introduce fractional powers of quaternionic operators. Their definition is based on the theory of slice-hyperholomorphic functions and on the $S$-resolvent operators of the quaternionic functional calculus. The integral…

Functional Analysis · Mathematics 2016-05-24 Fabrizio Colombo , Jonathan Gantner

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

In 2016, the spectral theory on the $S$-spectrum was used to establish the $H^\infty$-functional calculus for quaternionic or Clifford operators. This calculus applies for example to sectorial or bisectorial right linear operators $T$ and…

Spectral Theory · Mathematics 2025-05-06 Fabrizio Colombo , Francesco Mantovani , Peter Schlosser

The theory of slice regular functions of a quaternionic variable, introduced in 2006 by Gentili and Struppa, extends the notion of holomorphic function to the quaternionic setting. This fast growing theory is already rich of many results…

Complex Variables · Mathematics 2015-03-17 Chiara de Fabritiis , Graziano Gentili , Giulia Sarfatti

In this paper, we define the quaternionic Fock spaces $\mathfrak{F}_{\alpha}^p$ of entire slice hyperholomorphic functions in a quaternionic unit ball $\mathbb{B}$ in $\mathbb{H}.$ We also study growth estimate and various results of entire…

Functional Analysis · Mathematics 2016-11-17 Sanjay Kumar , S. D. Sharma , Khalid Manzoor

Slice regular functions are a generalization of holomorphic functions to the setting of quaternions (and more generally, Clifford algebras). In this paper, we first establish the Bohr inequality for slice starlike functions and slice…

Complex Variables · Mathematics 2025-11-18 Sabir Ahammed , Molla Basir Ahamed , Ming-Sheng Liu

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 main purpose of this work is the construction of an analytic functional calculus for Clifford operators, which are operators acting on certain modules over Clifford algebras. Unlike in some preceding works by other authors, we use a…

Functional Analysis · Mathematics 2020-08-18 Florian-Horia Vasilescu

This work looks at the theory of octonionic slice regular functions through the lens of differential topology. It proves a full-fledged version of the Open Mapping Theorem for octonionic slice regular functions. Moreover, it opens the path…

Complex Variables · Mathematics 2022-10-13 Riccardo Ghiloni , Alessandro Perotti , Caterina Stoppato

In this paper we introduce and study some basic properties of the Fock space (also known as Segal-Bargmann space) in the slice hyperholomorphic setting. We discuss both the case of slice regular functions over quaternions and also the case…

Complex Variables · Mathematics 2014-06-24 Daniel Alpay , Fabrizio Colombo , Irene Sabadini , Guy Salomon

In this paper, we utilize various integral representations derived from the Fueter-Sce extension theorem, to introduce novel functional calculi tailored for quaternionic operators of sectorial type. Specifically, due to the different…

Functional Analysis · Mathematics 2024-02-23 Fabrizio Colombo , Stefano Pinton , Peter Schlosser