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The main results presented in this paper provide a complete and explicit description of all solutions to the left tangential operator Nevanlinna- Pick interpolation problem assuming the associated Pick operator is strictly positive. The…

Functional Analysis · Mathematics 2018-04-24 A. E. Frazho , S. Ter Horst , M. A. Kaashoek

Given a domain $\Omega$ in $\mathbb{C}^m$, and a finite set of points $z_1,z_2,\ldots, z_n\in \Omega$ and $w_1,w_2,\ldots, w_n\in \mathbb{D}$ (the open unit disc in the complex plane), the \textit{Pick interpolation problem} asks when there…

Functional Analysis · Mathematics 2023-09-13 Tirthankar Bhattacharyya , Anindya Biswas , Vikramjeet Singh Chandel

This paper studies the determining sets for analytic functions from the symmetrized bidisk into the open unit disk in $\mathbb C$. It relates the idea to the uniqueness of the solutions of a Nevanlinna-Pick interpolation problem. It also…

Complex Variables · Mathematics 2022-08-15 B. Krishna Das , P. Kumar , H. Sau

Given a collection $K$ of positive integers, let $H^{\infty}_K(\mathbb{D})$ denote the set of all bounded analytic functions defined on the unit disk $\mathbb{D}$ in $\mathbb{C}$ whose $k^{\text{th}}$ derivative vanishes at zero, for all $k…

Complex Variables · Mathematics 2020-03-02 Debendra P. Banjade , Jeremiah Dunivin

We analyse a special case of the robust stabilization problem under structured uncertainty. We obtain a new criterion for the solvability of the spectral Nevanlinna-Pick problem, which is a special case of the $\mu$-synthesis problem of…

Complex Variables · Mathematics 2013-03-22 Jim Agler , Z. A. Lykova , N. J. Young

We show that the Hardy space on the unit disk is the only non-trivial irreducible reproducing kernel Hilbert space which satisfies the complete Nevanlinna-Pick property and hyponormality of all multiplication operators.

Functional Analysis · Mathematics 2015-10-08 Michael Hartz

We investigate the Schwarz lemma and the Schur algorithm for elements in the unit ball of the multiplier algebra of a reproducing kernel Hilbert space on the open unit ball whose kernel satisfies the complete Nevanlinna-Pick property. This…

Functional Analysis · Mathematics 2023-12-05 Daniel Alpay , Tirthankar Bhattacharyya , Abhay Jindal , Poornendu Kumar

This note finds a new characterization of complete Nevanlinna-Pick kernels on the Euclidean unit ball. The classical theory of Sz.-Nagy and Foias about the characteristic function is extended in this note to a commuting tuple $\bfT$ of…

Functional Analysis · Mathematics 2023-05-01 Tirthankar Bhattacharyya , Abhay Jindal

I describe a verifiable criterion for the solvability of the 2 by 2 spectral Nevanlinna-Pick problem with two interpolation points, and likewise for three other special cases of the mu-synthesis problem. The problem is to construct an…

Complex Variables · Mathematics 2012-01-10 N. J. Young

Let $(\mathcal{H}_k, \mathcal{H}_{\ell})$ be a pair of Hilbert function spaces with kernels $k, \ell$. In a 2005 paper, Shimorin showed that a certain factorization condition on $(k, \ell)$ yields a commutant lifting theorem for multipliers…

Functional Analysis · Mathematics 2025-08-27 Scott McCullough , Georgios Tsikalas

The Sz.-Nagy Foias characteristic function for a contraction has had a rejuvenation in recent times due to a number of authors. Such a classical object relates to an object of very contemporary interest, viz., the complete Nevanlinna-Pick…

Functional Analysis · Mathematics 2024-02-09 Tirthankar Bhattacharyya , Abhay Jindal

This article treats Nevanlinna-Pick interpolation in the setting of a special class of algebraic curves called distinguished varieties. An interpolation theorem, along with additional operator theoretic results, is given using a family of…

Functional Analysis · Mathematics 2013-02-06 Michael T. Jury , Greg Knese , Scott McCullough

We study reproducing kernel Hilbert spaces on the unit ball with the complete Nevanlinna-Pick property through the representation theory of their algebras of multipliers. We give a complete description of the representations in terms of the…

Operator Algebras · Mathematics 2020-09-23 Raphaël Clouâtre , Michael Hartz

We consider de Branges-Rovnyak spaces of a considerably large class of reproducing kernel Hilbert spaces and find a characterization for them to be complete Nevanlinna-Pick spaces. This extends as well as recovers earlier characterizations…

Functional Analysis · Mathematics 2025-08-08 Hamidul Ahmed , B. Krishna Das , Samir Panja

An indefinite generalization of Nudel'man's problem is used in a systematic approach to interpolation theorems for generalized Schur and Nevanlinna functions with interior and boundary data. Besides results on existence criteria for…

Functional Analysis · Mathematics 2007-05-23 D. Alpay , T. Constantinescu , A. Dijksma , J. Rovnyak

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

We prove existence and uniqueness of a solution of the Dirichlet problem for separately $(\alpha, \beta)$ - harmonic functions on the unit polydisc $\mathbb D^n$ with boundary data in $C(\mathbb T^n)$ using $(\alpha, \beta)$ - Poisson…

Complex Variables · Mathematics 2023-05-19 Jelena Gajic , Milos Arsenovic , Miodrag Mateljevic

We introduce Nevanlinna classes of holomorphic functions associated to a closed set on the boundary of the unit disc in the complex plane and we get Blaschke type theorems relative to these classes by use of several complex variables…

Complex Variables · Mathematics 2017-06-14 Eric Amar

We return to Takagi's variational principle, generalized after forty years to two complex variables by Pfister. Both isolating some extremal rational functions associated to a bounded holomorphic function in the unit disk, respectively the…

Complex Variables · Mathematics 2025-09-22 Mainak Bhowmik , Mihai Putinar

We give a solution to Pick's interpolation problem on the unit polydisc in $\mathbb{C}^n$, $n\geq 2$, by characterizing all interpolation data that admit a $\mathbb{D}$-valued interpolant, in terms of a family of positive-definite kernels…

Complex Variables · Mathematics 2019-12-20 Gautam Bharali , Vikramjeet Singh Chandel