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Herglotz's representation of holomorphic functions with positive real part and Carath\'eodory's theorem on approximation by inner functions are two well-known classical results in the theory of holomorphic functions on the unit disc. We…

Functional Analysis · Mathematics 2024-03-05 Tirthankar Bhattacharyya , Mainak Bhowmik , Poornendu Kumar

In this paper a quaternionic sharp version of the Carath\'{e}odory theorem is established for slice regular functions with positive real part, which strengthes a weaken version recently established by D. Alpay et. al. using the Herglotz…

Complex Variables · Mathematics 2014-10-17 G. B. Ren , X. P. Wang

We show that the Herglotz functions that arise as Weyl-Titchmarsh $m$ functions of one-dimensional Schr\"odinger operators are dense in the space of all Herglotz functions with respect to uniform convergence on compact subsets of the upper…

Spectral Theory · Mathematics 2016-02-23 Injo Hur

A Herglotz function is a holomorphic map from the open complex unit disk into the closed complex right halfplane. A classical Herglotz function has an integral representation against a positive measure on the unit circle. We prove a free…

Operator Algebras · Mathematics 2020-05-26 J. E. Pascoe , Benjamin Passer , Ryan Tully-Doyle

The Herglotz representation theorem for holomorphic functions with non-negative real part is a fundamental result in the theory of holomorphic functions. In this paper, we reinterpret the Herglotz representation in the context of modern…

Functional Analysis · Mathematics 2024-11-25 Mainak Bhowmik , Poornendu Kumar

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 article, we characterize the radial operators on weighted Bergman spaces of Reinhardt domains in $\mathbb{C}^n$, the Dirichlet and the Hardy spaces of the open unit disk $\mathbb{D}$, in terms of integral representations. We also…

Functional Analysis · Mathematics 2024-10-01 Bishal Bhunia

We prove representation theorems for Carath\'eodory functions in the setting of Banach spaces.

Functional Analysis · Mathematics 2007-05-23 Daniel Alpay , Olga Timoshenko , Dan Volok

Inner functions are the backbone of holomorphic function theory. This paper studies the inner functions on quotient domains of the open unit polydisc, $\bD^d$, arising from the group action of finite pseudo-reflection groups. Such quotient…

Functional Analysis · Mathematics 2025-04-04 Mainak Bhowmik , Poornendu Kumar

We give a generalization of the nonexistence of level structures as Nadel, Noguchi, Hwang-To, for quasi-projective manifolds uniformized by strongly Carath\'eodory hyperbolic complex manifolds. Examples include moduli space of compact…

Algebraic Geometry · Mathematics 2025-01-17 Kwok-Kin Wong , Sai-Kee Yeung

This is an introduction to the geometry of compact Riemann surfaces, largely following the books Farkas-Kra, Fay, Mumford Tata lectures. 1) Defining Riemann surfaces with atlases of charts, and as locus of solutions of algebraic equations.…

Mathematical Physics · Physics 2018-05-17 Bertrand Eynard

For $S$ a contractive analytic operator-valued function on the unit disk ${\mathbb D}$, de Branges and Rovnyak associate a Hilbert space of analytic functions ${\mathcal H}(S)$. A companion survey provides equivalent definitions and basic…

Classical Analysis and ODEs · Mathematics 2014-05-14 Joseph A. Ball , Vladimir Bolotnikov

We prove a compact embedding theorem in a class of spaces of piecewise H1 functions subordinated to a class of shape regular, but not necessarily quasi-uniform triangulations of a polygonal domain. This result generalizes the…

Numerical Analysis · Mathematics 2013-03-01 Sheng Zhang

This survey mainly deals with the tilted Carath{\'e}odory class by angle $\lambda$ (denoted by $\mathcal{P}_{\lambda}$) an element of which maps the unit disc into the tilted right half-plane $\{w: \Re e^{i\lambda} w>0\}$. Firstly we will…

Complex Variables · Mathematics 2010-06-30 Li-Mei Wang

The Riemann-Roch theorem is of utmost importance in the algebraic geometric theory of compact Riemann surfaces. It tells us how many linearly independent meromorphic functions there are having certain restrictions on their poles. The aim of…

Complex Variables · Mathematics 2007-06-20 A. Lesfari

Let $\mathcal{P}$ denote the Carath\'{e}odory class accommodating all the analytic functions $p$ having positive real part and satisfying $p(0)=1$. In this paper, the second coefficient of the normalized analytic function $f$ defined on the…

Complex Variables · Mathematics 2023-05-26 Meghna Sharma , Naveen Kumar Jain , Sushil Kumar

Using Zeilberger generating function formula for the values of a discrete analytic function in a quadrant we make connections with the theory of structured reproducing kernel spaces, structured matrices and a generalized moment problem. An…

Complex Variables · Mathematics 2022-03-28 Daniel Alpay , Fabrizio Colombo , Kamal Diki , Irene Sabadini , Dan Volok

Inspired by the theories of Kaplansky-Hilbert modules and probability theory in vector lattices, we generalise functional analysis by replacing the scalars $\mathbb{R}$ or $\mathbb{C}$ by a real or complex Dedekind complete unital…

In this paper we extend vessel theory, or equivalently, the theory of overdetermined $2D$ systems to the Pontryagin space setting. We focus on realization theorems of the various characteristic functions associated to such vessels. In…

Functional Analysis · Mathematics 2018-06-29 Daniel Alpay , Ariel Pinhas , Victor Vinnikov

We describe several classes of holomorphic functions of positive real part on the unit ball; each is characterized by an operator-valued Herglotz formula. Motivated by results of J.E. McCarthy and M. Putinar, we define a family of weighted…

Functional Analysis · Mathematics 2008-01-04 Michael T. Jury
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