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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

In this paper we study fractional powers of the Bessel differential operator defined on a semiaxis. Some important properties of such fractional powers of the Bessel differential operator are proved. They include connections with Legendre…

Classical Analysis and ODEs · Mathematics 2018-06-04 S. M. Sitnik , E. L. Shishkina

We study a new class of functions that arise naturally in quaternionic analysis, we call them "quasi regular functions". Like the well-known quaternionic regular functions, these functions provide representations of the quaternionic…

Representation Theory · Mathematics 2026-01-26 Igor Frenkel , Matvei Libine

In this paper, we introduce the new construction of fractional derivatives and integrals with respect to a function, based on a matrix approach. We believe that this is a powerful tool in both analytical and numerical calculations. We begin…

Numerical Analysis · Mathematics 2025-12-12 V. N. Kolokoltsov , E. L. Shishkina

We investigate the rational approximation of fractional powers of unbounded positive operators attainable with a specific integral representation of the operator function. We provide accurate error bounds by exploiting classical results in…

Numerical Analysis · Mathematics 2024-03-19 Lidia Aceto , Paolo Novati

The main goal of this work is classifying the singularities of slice regular functions over a real alternative *-algebra A. This function theory has been introduced in 2011 as a higher-dimensional generalization of the classical theory of…

Complex Variables · Mathematics 2017-03-16 Riccardo Ghiloni , Alessandro Perotti , Caterina Stoppato

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

Notions of a "holomorphic" function theory for functions of a split-quaternionic variable have been of recent interest. We describe two found in the literature and show that one notion encompasses a small class of functions, while the other…

Complex Variables · Mathematics 2015-06-25 John A. Emanuello , Craig A. Nolder

This paper addresses particular eigenvalue problems within the context of two quaternionic function theories. More precisely, we study two concrete classes of quaternionic eigenvalue problems, the first one for the slice derivative operator…

Complex Variables · Mathematics 2023-10-16 Rolf Sören Krausshar , Alessandro Perotti

In this paper we explore the theory of fractional powers of non-negative (and not necessarily self-adjoint) operators and its amazing relationship with the Chebyshev polynomials of the second kind to obtain results of existence, regularity…

Analysis of PDEs · Mathematics 2021-07-12 Flank D. M. Bezerra , Lucas A. Santos

The possibility of formulating quantum mechanics over quaternionic Hilbert spaces can be traced back to von Neumann's foundational works in the thirties. The absence of a suitable quaternionic version of spectrum prevented the full…

Functional Analysis · Mathematics 2017-10-20 Riccardo Ghiloni , Valter Moretti , Alessandro Perotti

This paper introduce a fractional-fractal $\psi$-Fueter operator in the quaternionic context inspired in the concepts of proportional fractional derivative and Hausdorff derivative of a function with respect to a fractal measure. Moreover,…

Complex Variables · Mathematics 2025-02-24 José Oscar González-Cervantes , Juan Adrián Ramírez-Belman , Juan Bory-Reyes

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

A new approach to normal operators in real Hilbert spaces is discussed, and a spectral representation is obtained, derived directly from the complex case. The results are then applied to quaternionic normal operators, regarded as a special…

Functional Analysis · Mathematics 2025-07-28 Florian-Horia Vasilescu

We define and examine certain matrix-valued multiplicative functionals with local Kato potential terms and use probabilistic techniques to prove that the semigroups of the corresponding partial differential operators with matrix-valued…

Mathematical Physics · Physics 2011-05-06 Batu Güneysu

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

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

In this paper, we first prove that the S-spectrum of a bounded right quaternionic linear operator on a two-sided quaternionic Banach space is a union of the spectrum of some bounded linear operators on a complex Banach space. Furthermore,…

Functional Analysis · Mathematics 2020-05-21 El Hassan Benabdi , Mohamed Barraa

Denoting by $\mathbb{M}$ the complexification of the quaternionic algebra $\mathbb{H}$, we characterize the family of those $\mathbb{M}$-valued functions, defined on subsets of $\H$, whose values are actually quaternions, using an intrinsic…

Functional Analysis · Mathematics 2019-05-31 Florian-Horia Vasilescu

The theory of the operator $$G(x) = |\underline{x}|^2 \frac{\partial }{\partial x_0} + \underline{x} \sum_{j=1}^n x_j \frac{\partial }{\partial x_j} $$ is deeply associated with the slice monogenic function theory and has grown in recent…

Complex Variables · Mathematics 2026-04-17 J. O. González-Cervantes , D. González-Campos , J. Bory-Reyes