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Holomorphic functions are fundamental in operator theory and their Cauchy formula is a crucial tool for defining functions of operators. The Fueter-Sce extension theorem (often called Fueter-Sce mapping theorem) provides a two-step…

Spectral Theory · Mathematics 2024-10-11 Fabrizio Colombo , Antonino De Martino , Stefano Pinton , Irene Sabadini , Peter Schlosser

Holomorphic functions play a crucial role in operator theory and the Cauchy formula is a very important tool to define functions of operators. The Fueter-Sce-Qian extension theorem is a two steps procedure to extend holomorphic functions to…

Spectral Theory · Mathematics 2023-03-02 Fabrizio Colombo , Antonino De Martino , Stefano Pinton , Irene Sabadini

Harmonic and polyanalytic functional calculi have been recently defined for bounded commuting operators. Their definitions are based on the Cauchy formula of slice hyperholomorphic functions and on the factorization of the Laplace operator…

Spectral Theory · Mathematics 2023-04-21 Fabrizio Colombo , Antonino De Martino , Stefano Pinton

The Fueter-Sce-Qian mapping theorem is a two steps procedure to extend holomorphic functions of one complex variable to quaternionic or Clifford algebra-valued functions in the kernel of a suitable generalized Cauchy-Riemann operator. Using…

Complex Variables · Mathematics 2021-12-10 Fabrizio Colombo , Antonino De Martino , Irene Sabadini

The Fueter-Sce mapping theorem stands as one of the most profound outcomes in complex and hypercomplex analysis, producing hypercomplex generalizations of holomorphic functions. In recent years, delving into the factorization of the second…

Complex Variables · Mathematics 2025-05-13 Fabrizio Colombo , Antonino De Martino , Irene Sabadini

The aim of this paper is to give an overview of the spectral theories associated with the notions of holomorphicity in dimension greater than one. A first natural extension is the theory of several complex variables whose Cauchy formula is…

Spectral Theory · Mathematics 2020-11-24 Fabrizio Colombo , Jonathan Gantner , Stefano Pinton

The spectral theory on the $S$-spectrum was born out of the need to give quaternionic quantum mechanics (formulated by Birkhoff and von Neumann) a precise mathematical foundation. Then it turned out that this theory has important…

Functional Analysis · Mathematics 2022-10-11 Fabrizio Colombo , Jonathan Gantner , David P. Kimsey , Irene Sabadini

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

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

The foundation of spectral theory on the $S$-spectrum can be traced back to the quaternionic framework of quantum mechanics. The concept of $S$-spectrum for quaternionic operators emerged as the natural spectrum in slice hyperholomorphic…

Spectral Theory · Mathematics 2026-02-05 Francesco Mantovani

In a recent paper, we introduced the concept of generalized partial-slice monogenic functions. The class of these functions includes both the theory of monogenic functions and of slice monogenic functions with values in a Clifford algebra.…

Complex Variables · Mathematics 2024-10-30 Zhenghua Xu , Irene Sabadini

Since 2006 the theory of slice hyperholomorphic functions and the related spectral theory on the S-spectrum have had a very fast development. This new spectral theory based on the S-spectrum has applications, for example, in the formulation…

Functional Analysis · Mathematics 2021-11-15 Daniel Alpay , Fabrizio Colombo , Kamal Diki , Irene Sabadini

The Fueter mapping theorem gives a constructive way to extend holomorphic functions of one complex variable to monogenic functions, i.e., null solutions of the generalized Cauchy-Riemann operator in $\mathbb{R}^4$, denoted by $\mathcal{D}$.…

Spectral Theory · Mathematics 2022-11-18 Antonino De Martino , Stefano Pinton

The Fueter-Sce theorem is one of the most important results in hypercomplex analysis, providing a two-step procedure for constructing axially monogenic functions starting from holomorphic functions of one variable. In the first step, the…

Functional Analysis · Mathematics 2026-01-09 Antonino De Martino , Stefano Pinton

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 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

Fueter's theorem states, in modern terms, that the Laplacian maps slice-regular quaternionic functions into Fueter-regular functions with axial symmetry. This phenomenon is also present in the Clifford setting, where both slice-monogenic…

Complex Variables · Mathematics 2025-11-10 Riccardo Ghiloni , Caterina Stoppato

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

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

We present some new relations between the Cauchy-Riemann operator on the real Clifford algebra $\mathbb R_n$ of signature $(0,n)$ and slice-regular functions on $\mathbb R_n$. The class of slice-regular functions, which comprises all…

Complex Variables · Mathematics 2022-04-26 Alessandro Perotti
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