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Regarding quaternions as normal matrices, we first characterize the $2\times 2$ matrix-valued functions, defined on subsets of quaternions, whose values are quaternions. Then we investigate the regularity of quaternionic-valued functions,…

Functional Analysis · Mathematics 2019-02-12 Florian-Horia Vasilescu

In this paper, we prove that slice polyanalytic functions on quaternions can be considered as solutions of a power of some special global operator with nonconstant coefficients as it happens in the case of slice hyperholomorphic functions.…

Complex Variables · Mathematics 2021-01-06 Daniel Alpay , Kamal Diki , Irene Sabadini

According to [5] we define the $*$-exponential of a slice-regular function, which can be seen as a generalization of the complex exponential to quaternions. Explicit formulas for $\exp_*(f)$ are provided, also in terms of suitable sine and…

Complex Variables · Mathematics 2019-01-03 Amedeo Altavilla , Chiara de Fabritiis

Six years after William Rowan Hamilton's discovery of quaternions, in 1849 James Cockle introduced the algebra of split quaternions. (He called them ``coquaternions.'') In this paper we define regular functions on split quaternions and…

Complex Variables · Mathematics 2010-09-15 Matvei Libine

We show characterizations of the class of Cullen-regular functions in the sense of Gentili-Struppa for any domain $\Omega$ in terms of the Fueter operator. We then state a Integral Theorem and discuss how it can be used to define a more…

Complex Variables · Mathematics 2008-07-04 Daniel Alayon-Solarz

The Bargmann-Fock space of slice hyperholomorphic functions is recently introduced by Alpay, Colombo, Sabadini and Salomon. In this paper, we reconsider this space and present a direct proof of its independence of the slice. We also…

Complex Variables · Mathematics 2017-05-10 K. Diki , A. Ghanmi

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

We introduce two classes of right quaternionic Hilbert spaces in the context of slice polyregular functions, generalizing the so-called slice and full hyperholomorphic Bargmann spaces. Their basic properties are discussed, the explicit…

Complex Variables · Mathematics 2019-08-27 Abdelhadi Benahmadi , Amal El Hamyani , Allal Ghanmi

The pseudospherical functions on one-sheet, two-dimensional hyperboloid are discussed. The simplest method of construction of these functions is introduced using the Fock space structure of the representation space of the su(1,1) algebra.…

Mathematical Physics · Physics 2015-05-27 K. Kowalski , J. Rembielinski , A. Szczesniak

A previously established correspondence between definite-parity real functions and inner analytic functions is generalized to real functions without definite parity properties. The set of inner analytic functions that corresponds to the set…

Complex Variables · Mathematics 2015-05-12 Jorge L. deLyra

A new classification of real functions and other related real objects defined within a compact interval is proposed. The scope of the classification includes normal real functions and distributions in the sense of Schwartz, referred to…

Mathematical Physics · Physics 2015-07-07 Jorge L. deLyra

We will use analytic function theory and Fourier analysis to establish a characterization for some classical umbral calculus, which will focus on the generalization of the evaluation function. Although we cannot cover all the umbral…

Classical Analysis and ODEs · Mathematics 2021-03-17 Tang Qian

Given a quaternionic slice regular function $f$, we give a direct and effective way to compute the coefficients of its spherical expansion at any point. Such coefficients are obtained in terms of spherical and slice derivatives of the…

Complex Variables · Mathematics 2021-12-22 Amedeo Altavilla

This paper is inspired by a class of infinite order differential operators arising in the time evolution of superoscillations. Recently, infinite order differential operators have been considered and characterized on the spaces of entire…

Functional Analysis · Mathematics 2024-11-20 Stefano Pinton , Peter Schlosser

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

We introduce the notion of a pseudomultiplier of a Hilbert space $\mathcal H$ of functions on a set $\Omega$. Roughly, a pseudomultiplier of $\mathcal H$ is a function which multiplies a finite-codimensional subspace of $\mathcal H$ into…

Functional Analysis · Mathematics 2022-12-21 Jim Agler , Zinaida Lykova , N. J. Young

The celebrated Schwarz-Pick lemma for the complex unit disk is the basis for the study of hyperbolic geometry in one and in several complex variables. In the present paper, we turn our attention to the quaternionic unit ball B. We prove a…

Complex Variables · Mathematics 2013-02-12 Cinzia Bisi , Caterina Stoppato

Generalized analytic functions over generalized analytic manifolds are build from sums of convergent real power series with non-negative real exponents (and some well-ordering condition on the support). In a paper by Mart\'in-Villaverde,…

Algebraic Geometry · Mathematics 2022-06-23 B. Molina-Samper , J. Palma-Márquez , F. Sanz-Sánchez

The analogue of the Riesz-Dunford functional calculus has been introduced and studied recently as well as the theory of semigroups and groups of linear quaternionic operators. In this paper we suppose that $T$ is the infinitesimal generator…

Spectral Theory · Mathematics 2015-02-11 Daniel Alpay , Fabrizio Colombo , Jonathan Gantner , David P. Kimsey

We prove a Cauchy-type integral formula for slice-regular functions where the integration is performed on the boundary of an open subset of the quaternionic space, with no requirement of axial symmetry. In particular, we get a local…

Complex Variables · Mathematics 2023-10-16 Alessandro Perotti