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A physically more adequate definition of a quaternionic holomorphic (H-holomorphic) function of one quaternionic variable compared to known ones and a quaternionic generalization of Cauchy-Riemann's equations are presented. At that a class…

Complex Variables · Mathematics 2024-02-14 Michael Parfenov

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

Quaternionic tori are defined as quotients of the skew field $\mathbb{H}$ of quaternions by rank-4 lattices. Using slice regular functions, these tori are endowed with natural structures of quaternionic manifolds (in fact quaternionic…

Complex Variables · Mathematics 2018-07-04 Cinzia Bisi , Graziano Gentili

We give some characterizations of Lipschitz type spaces of slice regular functions in the unit ball of the skew field of quaternions with prescribed modulus of continuity.

Functional Analysis · Mathematics 2022-09-27 José Oscar González-Cervantes , Daniel González-Campos , Juan Bory-Reyes

The notion of a quaternionic gerbe is presented as a new way of bundling algebraic structures over a four manifold. The structure groupoid of this fibration is described in some detail. The Euclidean conformal group R*SO(4) appears…

Differential Geometry · Mathematics 2007-05-23 Finlay Thompson

In this paper we provide a general construction of a quaternionic Banach space of slice regular functions from a given Banach space of holomorphic functions, which we call its quaternionic lift. To the best of our knowledge, this…

Functional Analysis · Mathematics 2025-12-09 Nikolaos Chalmoukis , Giulia Sarfatti

We investigate slice-quaternionic Hopf surfaces. In particular, we construct new structures of slice-quaternionic manifold on $\mathbb{S}^1\times\mathbb{S}^7$, we study their group of automorphisms and their deformations.

Complex Variables · Mathematics 2019-06-26 Daniele Angella , Cinzia Bisi

In this paper we study Hankel operators in the quaternionic setting. In particular we prove that they can be exploited to measure the $L^{\infty}$ distance of a slice $L^{\infty}$ function from the space of bounded slice regular functions.

Complex Variables · Mathematics 2016-11-16 Giulia Sarfatti

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 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

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

We initiate the study of the generalized quaternionic manifolds by classifying the generalized quaternionic vector spaces, and by giving two classes of nonclassical examples of such manifolds. Thus, we show that any complex symplectic…

Differential Geometry · Mathematics 2011-11-02 Radu Pantilie

In the present paper we introduce the class of slice-polynomial functions: slice regular functions {defined over the quaternions, outside the real axis,} whose restriction to any complex half-plane is a polynomial. These functions naturally…

Complex Variables · Mathematics 2019-01-03 Amedeo Altavilla , Giulia Sarfatti

By analogy with the real and complex affine groups, whose unitary irreducible representations are used to define the one and two-dimensional continuous wavelet transforms, we study here the quaternionic affine group and construct its…

Mathematical Physics · Physics 2014-09-19 S. Twareque Ali , K. Thirulogasanthar

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

Starting with a concise review of quaternionic geometry and quaternionic K{\"a}hler manifolds, we define a transversely quaternionic K{\"a}hler foliation. Then we formulate and prove the foliated versions of the now classical results of…

Differential Geometry · Mathematics 2025-12-16 Rouzbeh Mohseni , Robert A. Wolak

In this paper we propose an Almansi-type decomposition for slice regular functions of several quaternionic variables. Our method yields $2^n$ distinct and unique decompositions for any slice function with domain in $\mathbb{H}^n$. Depending…

Complex Variables · Mathematics 2024-11-12 Giulio Binosi

The purpose of this paper is twofold. One is to enrich from a geometrical point of view the theory of octonionic slice regular functions. We first prove a boundary Schwarz lemma for slice regular self-mappings of the open unit ball of the…

Complex Variables · Mathematics 2016-04-15 Xieping Wang

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 article we give an approach to define continuous functional calculus for bounded quaternionic normal operators defined on a right quaternionic Hilbert space.

Spectral Theory · Mathematics 2017-11-06 G. Ramesh , P. Santhosh Kumar