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We study various aspects of Schur analysis in the slice hyperholomorphic setting. We present two sets of results: first, we give new results on the functional calculus for slice hyperholomorphic functions. In particular, we introduce and…

Functional Analysis · Mathematics 2012-11-14 Daniel Alpay , Fabrizio Colombo , Irene Sabadini

In this paper we prove a quaternionic positive real lemma as well as its generalized version, in case the associated kernel has negative squares for slice hyperholomorphic functions. We consider the case of functions with positive real part…

Complex Variables · Mathematics 2018-10-16 D. Alpay , F. Colombo , I. Lewkowicz , I. Sabadini

we start the study of Schur analysis in the quaternionic setting using the theory of slice hyperholomorphic functions. The novelty of our approach is that slice hyperholomorphic functions allows to write realizations in terms of a suitable…

Functional Analysis · Mathematics 2011-10-13 Daniel Alpay , Fabrizio Colombo , Irene Sabadini

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

We introduce generalized Schur functions and generalized positive functions in setting of slice hyperholomorphic functions and study their realizations in terms of associated reproducing kernel Pontryagin spaces

Complex Variables · Mathematics 2014-11-10 Daniel Alpay , Fabrizio Colombo , Izchak Lewkowicz , Irene Sabadini

In this work we treat realization results for operator-valued functions which are analytic in the complex sense or slice hyperholomorphic over the quaternions. In the complex setting, we prove a realization theorem for an operator-valued…

Functional Analysis · Mathematics 2018-04-17 Daniel Alpay , Fabrizio Colombo , Irene Sabadini

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

In this paper we characterize the closed invariant subspaces for the ($*$-)multiplier operator of the quaternionic space of slice $L^2$ functions. As a consequence, we obtain the inner-outer factorization theorem for the quaternionic Hardy…

Complex Variables · Mathematics 2018-06-13 Alessandro Monguzzi , Giulia Sarfatti

We give a generalization of the Beurling-Lax theorem both in the complex and quaternionic settings. We consider in the first case functions meromorphic in the right complex half-plane, and functions slice hypermeromorphic in the right…

Functional Analysis · Mathematics 2015-09-22 Daniel Alpay , Irene Sabadini

In this paper we study the additive splitting associated to the quaternionic Cauchy transform defined by the Cauchy formula of slice hyperholomorphic functions. Moreover, we introduce and study the analogue of the fundamental solution of…

Complex Variables · Mathematics 2019-01-30 Fabrizio Colombo , Samuele Mongodi

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

In this paper, we study the quaternionic counterpart of complex Fock spaces $\mathfrak{F}_{\alpha}^p ( 0<p<\infty$ and for some parameter $\alpha$) of entire slice hyperholomorphic functions in an Euclidean unit ball $\mathbb{B}^n$ in…

Functional Analysis · Mathematics 2016-12-06 Sanjay Kumar , Khalid Manzoor

In this paper we summarize some known facts on slice topology in the quaternionic case, and we deepen some of them by proving new results and discussing some examples. We then show, following [18], how this setting allows us to generalize…

Complex Variables · Mathematics 2024-06-27 X. Dou , M. Jin , G. Ren , I. Sabadini

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

Entire functions in one complex variable are extremely relevant in several areas ranging from the study of convolution equations to special functions. An analog of entire functions in the quaternionic setting can be defined in the slice…

Complex Variables · Mathematics 2016-11-08 Fabrizio Colombo , Irene Sabadini , Daniele C. Struppa

A slice regular analogue of the Malmquist-Takenaka system is investigated. It is proved that they form a complete orthonormal system in the quaternionic Hardy spaces of the unit ball. The properties of associated projection operator are…

Complex Variables · Mathematics 2016-11-21 Margit Pap

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 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

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

We construct a counterexample to a well-known extension theorem for slice regular functions, which motivates us to develop a theory of Riemann slice-domains by introducing a new topology on quaternions. By some paths describing axial…

Complex Variables · Mathematics 2019-02-13 Xinyuan Dou , Guangbin Ren
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