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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

This paper addresses the Corona problem for slice hyperholomorphic functions for a single quaternionic variable. While the Corona problem is well-understood in the context of one complex variable, it remains highly challenging in the case…

Complex Variables · Mathematics 2025-08-28 Fabrizio Colombo , Elodie Pozzi , Irene Sabadini , Brett D. Wick

We obtain general identities for the product of two Schur functions in the case where one of the functions is indexed by a rectangular partition, and give their t-analogs using vertex operators. We study subspaces forming a filtration for…

Combinatorics · Mathematics 2007-05-23 L. Lapointe , J. Morse

Slice regular functions have been extensively studied over the past decade, but much less is known about their boundary behavior. In this paper, we initiate the study of Julia theory for slice regular functions. More specifically, we…

Complex Variables · Mathematics 2016-03-22 Guangbin Ren , Xieping Wang

In 2016, the spectral theory on the $S$-spectrum was used to establish the $H^\infty$-functional calculus for quaternionic or Clifford operators. This calculus applies for example to sectorial or bisectorial right linear operators $T$ and…

Spectral Theory · Mathematics 2025-05-06 Fabrizio Colombo , Francesco Mantovani , Peter Schlosser

We study reproducing kernel Hilbert and Pontryagin spaces of slice hyperholomorphic functions which are analogs of the Hilbert spaces of analytic functions introduced by de Branges and Rovnyak. In the first part of the paper we focus on the…

Functional Analysis · Mathematics 2012-03-02 Daniel Alpay , Fabrizio Colombo , Irene 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

Using the notion of commutative operator vessels, this work investigates de Branges-Rovnyak spaces whose elements are sections of a line bundle of multiplicative half-order differentials on a compact real Riemann surface. As a special case,…

Complex Variables · Mathematics 2020-07-15 Daniel Alpay , Ariel Pinhas , Victor Vinnikov

In this paper, we lay the foundations of the theory of slice regular functions in several variables ranging in any real alternative $^*$-algebra, including quaternions, octonions and Clifford algebras. This theory is an extension of the…

Complex Variables · Mathematics 2023-10-16 Riccardo Ghiloni , Alessandro Perotti

The Schur function expansion of Sato-Segal-Wilson KP tau-functions is reviewed. The case of tau-functions related to algebraic curves of arbitrary genus is studied in detail. Explicit expressions for the Pl\"ucker coordinate coefficients…

Mathematical Physics · Physics 2013-04-08 V. Enolski , J. Harnad

In the literature on slice analysis in the hypercomplex setting, there are two main approaches to define slice regular functions in one variable: one consists in requiring that the restriction to any complex plane is holomorphic (with the…

Complex Variables · Mathematics 2024-06-28 Xinyuan Dou , Guangbin Ren , Irene Sabadini , Ting Yang

A factorial analogue of the supersymmetric Schur functions is introduced. It is shown that factorial versions of the Jacobi--Trudi and Sergeev--Pragacz formulae hold. The results are applied to construct a linear basis in the center of the…

q-alg · Mathematics 2008-02-03 Alexander Molev

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

The Bargmann-Fock space(or Fock space for short) is a fundamental example of reproducing kernel Hilbert spaces that has found fascinating applications across multiple fields of current interest, including quantum mechanics, time-frequency…

Complex Variables · Mathematics 2025-10-14 Kamal Diki

Following ideas by Beardon, Minda and Baribeau, Rivard, Wegert in the context of the complex Schwarz-Pick Lemma, we use iterated hyperbolic difference quotients to prove a quaternionic multipoint Schwarz-Pick Lemma, in the context of the…

Complex Variables · Mathematics 2026-04-01 Cinzia Bisi , Davide Cordella

This is an outline of Erlangen Program at Large. Study of objects and properties, which are invariant under a group action, is very fruitful far beyond the traditional geometry. In this paper we demonstrate this on the example of the group…

Complex Variables · Mathematics 2010-06-11 Vladimir V. Kisil

In this paper we begin the study of some important Banach spaces of slice hyperholomorphic functions, namely the Bloch, Besov and weighted Bergman spaces, and we also consider the Dirichlet space, which is a Hilbert space. The importance of…

Complex Variables · Mathematics 2014-03-28 C. M. P. Castillo Villalba , F. Colombo , J. Gantner , J. O. Gonzalez-Cervantes

Using the vertex operator representations for symplectic and orthogonal Schur functions, we define two families of symmetric functions and show thatthey are the skew symplectic and skew orthogonal Schur polynomials defined implicitly by…

Combinatorics · Mathematics 2024-05-22 Naihuan Jing , Zhijun Li , Danxia Wang

This work presents a family of fiber bundles where the total spaces are associated with holomorphic functions on several complex variables and the basis spaces extend the notion of quaternionic slice regular functions of several…

Complex Variables · Mathematics 2023-04-18 José Oscar González Cervantes

We continue the development of X-ray tomography in sub-Riemannian geometry. Using the Fourier Transform adapted to the group structure, we generalize the Fourier Slice Theorem to the class of H-type groups. The Fourier Slice Theorem…

Differential Geometry · Mathematics 2023-12-04 Steven Flynn