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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

We prove that every generator of a symmetric contraction semigroup on a $\sigma$-finite measure space admits, for $1<p<\infty$, a H\"ormander-type holomorphic functional calculus on $L^p$ in the sector of angle $\phi^*_p=\arcsin|1-2/p|$.…

Classical Analysis and ODEs · Mathematics 2017-04-05 Andrea Carbonaro , Oliver Dragičević

The theory of slice regular (also called hyperholomorphic) functions is a generalization of complex analysis originally given in the quaternionic framework, and then further extended to Clifford algebras, octonions, and to real alternative…

Complex Variables · Mathematics 2025-12-02 Xinyuan Dou , Ming Jin , Guangbin Ren , Irene Sabadini

Let T_t = e^{-tA} be a bounded analytic semigroup on Lp, with 1<p<\infty. It is known that if A and its adjoint A^* both satisfy square function estimates \bignorm{\bigl(\int_{0}^{\infty}| A^{1/2} T_t(x)|^2\, dt\,\bigr)^{1/2}_{Lp} \lesssim…

Functional Analysis · Mathematics 2011-11-17 Christian Le Merdy

Based on the full similarity in algebraic properties and differentiation rules between quaternionic (H-) holomorphic and complex (C-) holomorphic functions, we assume that there exists one holistic notion of a holomorphic function that has…

Complex Variables · Mathematics 2024-08-01 Michael Parfenov

Soit R\_{0,2m+1} l'alg\`{e}bre de Clifford de R^{2m+1} muni d'une forme quadratique de signature n\'{e}gative, D = \sum\_{i=0}^{2m+1} e\_i {\partial\over \partial x\_i}, \Delta le Laplacien ordinaire. Les fonctions holomorphes…

Complex Variables · Mathematics 2007-05-23 Guy Laville , Ivan Ramadanoff

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

For a bounded quaternionic operator $T$ on a right quaternionic Hilbert space $\mathcal{H}$ and $\varepsilon >0$, the pseudo $S$-spectrum of $T$ is defined as \begin{align*} \Lambda_{\varepsilon}^{S}(T) := \sigma_S (T) \bigcup \left \{ q…

Functional Analysis · Mathematics 2022-10-11 Kousik Dhara , Santhosh Kumar Pamula

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

This paper focuses on the development of harmonic and Clifford analysis techniques in the context of some conformally flat manifolds that arise from factoring out a simply-connected domain from $R^n$ by special arithmetic subgroups of the…

Differential Geometry · Mathematics 2007-05-23 R. S. Krausshar , John Ryan , Qiao Yuying

Octonionic analysis is becoming eminent due to the role of octonions in the theory of G2 manifold. In this article, a new slice theory is introduced as a generalization of the holomorphic theory of several complex variables to the…

Complex Variables · Mathematics 2018-12-12 Guangbin Ren , Ting Yang

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

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 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

We define a very general notion of regularity for functions taking values in an alternative real $*$-algebra. Over Clifford numbers, this notion subsumes the well-established notions of monogenic function and slice-monogenic function. Over…

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

Quaternionic Clifford analysis is a recent new branch of Clifford analysis, a higher dimensional function theory which refines harmonic analysis and generalizes to higher dimension the theory of holomorphic functions in the complex plane.…

Complex Variables · Mathematics 2016-04-07 Fred Brackx , Hennie De Schepper , David Eelbode , Roman Lavicka , Vladimir Soucek

In this paper, we are concerned with the S-polyregularity the regular dot product of slice regular functions. We prove that the product of a slice regular function and right quaternionic polynomial function is a S-polyregular function and…

Complex Variables · Mathematics 2019-01-30 Allal Ghanmi

In this article we apply a recently established transference principle in order to obtain the boundedness of certain functional calculi for semigroup generators. In particular, it is proved that if $-A$ generates a $C_0$-semigroup on a…

Functional Analysis · Mathematics 2013-11-20 Markus Haase , Jan Rozendaal

We present an approach to the spectrum and analytic functional calculus for quaternionic linear operators, following the corresponding results concerning the real linear operators. In fact, the construction of the analytic functional…

Functional Analysis · Mathematics 2020-05-06 Florian-Horia Vasilescu

In this article we investigate harmonicity, Laplacians, mean value theorems and related topics in the context of quaternionic analysis. We observe that a Mean Value Formula for slice regular functions holds true and it is a consequence of…

Complex Variables · Mathematics 2020-11-09 Cinzia Bisi , Joerg Winkelmann