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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

Consider a scaled Nevanlinna-Pick interpolation problem and let $\Pi$ be the Blaschke product whose zeros are the nodes of the problem. It is proved that if $\Pi$ belongs to a certain class of inner functions, then the extremal solutions of…

Complex Variables · Mathematics 2014-05-21 Nacho Monreal Galán , Artur Nicolau

A subclass of complex-valued close-to-convex harmonic functions that are univalent and sense-preserving in the open unit disc is investigated. The coefficient estimates, growth results, area theorem, boundary behavior, convolution and…

Complex Variables · Mathematics 2012-07-17 Sumit Nagpal , V. Ravichandran

By extending the idea of a difference operator with a fixed step to varying-steps difference operators, we have established a difference Nevanlinna theory for meromorphic functions with the steps tending to zero (vanishing period) and a…

Complex Variables · Mathematics 2017-03-14 Yik-Man Chiang , Xudan Luo

We revisit the problem of characterizing cyclic elements for the shift operator in a broad class of radial growth spaces of holomorphic functions on the unit disk, focusing on functions of finite Nevanlinna characteristic. We provide…

Complex Variables · Mathematics 2025-04-01 Linus Bergqvist , Adem Limani , Bartosz Malman

We show that a nonvanishing analytic function on a domain in the unit disc can be approximated by (a scalar multiple of) a Blaschke product whose zeros lie on a prescribed circle enclosing the domain. We also give a new proof of the…

Complex Variables · Mathematics 2010-02-02 David W. Farmer , Pamela Gorkin

In this paper we give precise characterizations of the relation between the Nevanlinna counting function and pull-back measure of an analytic self-map of the unit disk near the boundary. We show that it is quite worth considering these two…

Functional Analysis · Mathematics 2022-04-29 Yong-Xin Gao , Yuxia Liang , Ze-Hua Zhou

Biunivalent holomorphic functions form an interesting class in geometric function theory and are connected with special functions and solutions of complex differential equations. The paper reveals a deep connection between biunivalence and…

Complex Variables · Mathematics 2024-10-18 Samuel L. Krushkal

A tropical version of Nevanlinna theory is described in which the role of meromorphic functions is played by continuous piecewise linear functions of a real variable whose one-sided derivatives are integers at every point. These functions…

Exactly Solvable and Integrable Systems · Physics 2007-07-31 R. G. Halburd , N. J. Southall

This paper is associated with Nevanlinna class, Dirichlet series and Szeg\"o's problem in infinitely many variables. As we will see, there is a natural connection between these topics. The paper first introduces the Nevanlinna class and the…

Complex Variables · Mathematics 2022-06-02 Kunyu Guo , Jiaqi Ni , Qi Zhou

In this paper, we prove a lemma on logarithmic derivative for holomorphic curves from annuli into K\"{a}hler compact manifold and. As its application, a second main theorem for holomophic curves from annuli into semi abelian varieties…

Complex Variables · Mathematics 2022-06-01 Si Duc Quang

We prove a version of the Bernstein-Walsh theorem on uniform polynomial approximation of holomorphic functions on compact sets in several complex variables. Here we consider subclasses of the full polynomial space associated to a convex…

Complex Variables · Mathematics 2017-01-23 Len Bos , Norm Levenberg

We prove that the Nevalinna-Pick algorithm provides different homeomorphisms between certain topological spaces of measures, analytic functions and sequences of complex numbers. This algorithm also yields a continued fraction expansion of…

Classical Analysis and ODEs · Mathematics 2007-11-06 Olav Njastad , Luis Velazquez

We generalize our earlier results from \cite{K} on the Bessmertny\u{\i} class of operator-valued functions holomorphic in the open right poly-halfplane which admit representation as a Schur complement of a block of a linear homogeneous…

Functional Analysis · Mathematics 2007-05-23 Dmitry S. Kalyuzhny\uı-Verbovetzki\uı

In this expository article, we present a number of classic theorems that serve to identify the closure in the sup-norm of various sets of Blaschke products, inner functions and their quotients, as well as the closure of the convex hulls of…

Complex Variables · Mathematics 2017-01-20 Javad Mashreghi , Thomas Ransford

In this paper, we mainly propose improvements of the logarithmic difference lemma for meromorphic functions in several complex variables, and then investigate meromorphic solutions of partial difference equations from the viewpoint of…

Complex Variables · Mathematics 2019-09-10 Tingbin Cao , Ling Xu

Bounded holomorphic interpolation problems associated to finitely many data have, in general, distinct solutions. Uniqueness arises only in some convex extreme configurations. Rational inner functions in a polydisk are the best understood…

Functional Analysis · Mathematics 2025-09-23 Mainak Bhowmik , Mihai Putinar

We establish new analytic and numerical results on a general class of rational operator Nevanlinna functions that arise e.g. in modelling photonic crystals. The capability of these dielectric nano-structured materials to control the flow of…

Mathematical Physics · Physics 2015-07-24 Christian Engström , Heinz Langer , Christiane Tretter

We extend the study of the Pick class, the set of complex analytic functions taking the upper half plane into itself, to the noncommutative setting. R. Nevanlinna showed that elements of the Pick class have certain integral representations…

Functional Analysis · Mathematics 2013-10-18 J. E. Pascoe , Ryan Tully-Doyle

The class of Hausdorff spaces that are continuous images of compact orderable spaces is studied by analyzing the relationship between the elements of this class and compact orderable spaces in a back-and-forth fashion. Structure results for…

General Topology · Mathematics 2016-11-15 Ahmad Farhat