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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 a continuation of the research of our previous work and considers quaternionic generalized Carath\'eodory functions and the related family of generalized positive functions. It is addressed to a wide audience which includes…

Complex Variables · Mathematics 2020-04-23 Daniel Alpay , Fabrizio Colombo , Izchak Lewkowicz , Irene Sabadini

In this paper, we initiate the study of the geometric function theory for slice starlike functions over quaternions and its subclasses. This allows us to answer negatively some questions about the Bieberbach conjecture, the growth,…

Complex Variables · Mathematics 2025-03-18 Zhenghua Xu , Guangbin Ren

In the series of papers [FL,FL2] we approach quaternionic analysis from the point of view of representation theory of the conformal group SL(4,C) and its real forms. This approach has proven very fruitful and pushed further the parallel…

Representation Theory · Mathematics 2011-10-11 Igor Frenkel , Matvei Libine

The notion of monogenic (or regular) functions, which is a correspondence of holomorphic functions, has been studied extensively in hypercomplex analysis, including quaternionic, octonionic, and Clifford analysis. Recently, the concept of…

Complex Variables · Mathematics 2026-05-19 Zhenghua Xu , Chao Ding , Haiyan Wang

Slice analysis is a generalization of the theory of holomorphic functions of one complex variable to quaternions. Among the new phenomena which appear in this context, there is the fact that the convergence domain of…

Complex Variables · Mathematics 2021-01-26 Xinyuan Dou , Guangbin Ren , Irene Sabadini

We study a characterization of slice Carleson measures and of Carleson measures for the both the Hardy spaces $H^p(\mathbb B)$ and the Bergman spaces $\mathcal A^p(\mathbb B)$ of the quaternionic unit ball $\mathbb B$. In the case of…

Complex Variables · Mathematics 2017-01-25 Irene Sabadini , Alberto Saracco

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

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

We study the $L^p$ norm of the orthogonal projection from the space of quaternion valued $L^2$ functions to the closed subspace of slice $L^2$ functions.

Complex Variables · Mathematics 2015-06-23 Nicola Arcozzi , Giulia Sarfatti

In this paper we describe the rise of global operators in the scaled quaternionic case, an important extension from the quaternionic case to the family of scaled hypercomplex numbers $\mathbb{H}_t,\, t\in\mathbb{R}^*$, of which the…

Functional Analysis · Mathematics 2024-04-05 Daniel Alpay , Ilwoo Cho , Mihaela Vajiac

The theory of slice regular functions of a quaternion variable is applied to the study of orthogonal complex structures on domains \Omega\ of R^4. When \Omega\ is a symmetric slice domain, the twistor transform of such a function is a…

Differential Geometry · Mathematics 2015-07-27 Graziano Gentili , Simon Salamon , Caterina Stoppato

The goal of the present paper is to introduce and study noncommutative Hardy spaces associated with the regular $\Lambda$-polyball, to develop a functional calculus on noncommutative Hardy spaces for the completely non-coisometric (c.n.c.)…

Functional Analysis · Mathematics 2020-01-31 Gelu Popescu

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

We introduce a variable exponent version of the Hardy space of analytic functions on the unit disk, we show some properties of the space, and give an example of a variable exponent $p(\cdot)$ that satisfies the $\log$-H\"older condition…

Complex Variables · Mathematics 2018-11-01 Gerardo A. Chacón , Gerardo R. Chacón

The goal of this article is to present a survey of the recent theory of plurisubharmonic functions of quaternionic variables, and its applications to theory of valuations on convex sets and HKT-geometry (HyperK\"ahler with Torsion). The…

Metric Geometry · Mathematics 2016-07-08 Semyon Alesker

The present paper is a continuation of our work [11], where we introduced a fractional operator calculus related to a fractional ${\psi}-$Fueter operator in the one-dimensional Riemann-Liouville derivative sense in each direction of the…

Complex Variables · Mathematics 2022-09-27 José Oscar González-Cervantes , Juan Bory-Reyes

We investigate differentiability of functions defined on regions of the real quaternion field and obtain a noncommutative version of the Cauchy-Riemann conditions. Then we study the noncommutative analog of the Cauchy integral as well as…

Complex Variables · Mathematics 2007-05-23 S. V. Ludkovsky , F. van Oystaeyen

It is well known that the real and imaginary parts of any holomorphic function are harmonic functions of two variables. In this paper we generalize this property to finite-dimensional commutative algebras. We prove that if some basis of a…

Analysis of PDEs · Mathematics 2008-11-18 Anatoliy A. Pogorui

We obtain a new square function characterization of the weak Hardy space $H^{p,\infty}$ for all $p\in(0,\iy)$. This space consists of all tempered distributions whose smooth maximal function lies in weak $L^p$. Our proof is based on…

Classical Analysis and ODEs · Mathematics 2013-12-10 Danqing He