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We show that, in every weighted Dirichlet space on the unit disk with superharmonic weight, the Taylor series of a function in the space is $(C,\alpha)$-summable to the function in the norm of the space, provided that $\alpha>1/2$. We…

Complex Variables · Mathematics 2020-09-28 Javad Mashreghi , Pierre-Olivier Parisé , Thomas Ransford

We construct functions in the disc algebra with pointwise universal Fourier series on sets which are G-delta and dense and at the same time with Fourier series whose set of divergence is of Hausdorff dimension zero. We also see that some…

Classical Analysis and ODEs · Mathematics 2015-12-11 Christos Papachristodoulos , Michael Papadimitrakis

A compact subset $K$ of the complex plane $\C$ is a set of polynomial (respectively rational) approximation if $P(K)=A(K)$ (respectively $R(K)=A(K)$), where $P(K)$ (respectively $R(K)$) is the family of functions on $K$ which are uniform…

Complex Variables · Mathematics 2024-12-31 P. M. Gauthier , Jujie Wu

We prove that if f is a holomorphic function on the open unit disc in C whose cluster set C(f) has finite linear measure and is such that the complement of C(f) has finitely many components, then the derivative of f belongs to the Hardy…

Complex Variables · Mathematics 2016-10-25 Josip Globevnik , David Kalaj

We show generic existence of power series a with complex coefficients a_n, such that the sequence of partial sums of a new power series where its coefficients b_n are functions of a_0, a_1, ..., a_n approximate every polynomial uniformly on…

Complex Variables · Mathematics 2019-06-05 Konstantinos Maronikolakis , Vassili Nestoridis

We prove a formula for the Taylor series coefficients of a zero of the sum of a complex-exponent polynomial and a base function which is a general holomorphic function with a simple zero. Such a Taylor series is more general than a Puiseux…

Complex Variables · Mathematics 2021-03-16 Mario DeFranco

We generalize the universal power series of Seleznev to several variables and we allow the coefficients to depend on parameters. Then, the approximable functions may depend on the same parameters. The universal approximation holds on…

Complex Variables · Mathematics 2020-08-11 Konstantinos Maronikolakis , Giorgos Stamatiou

The main objective of the present article is to make interconnection between the Generalized Hyergeometric series and some subclasses of normalized analytic functions with positive(Tailor's) coefficients in the open unit disc $\mathbb{D}…

Complex Variables · Mathematics 2023-08-09 K. Chandrasekran , D. J. Prabhakaran

Let $T$ be a $C_0$--contraction on a separable Hilbert space. We assume that $I_H-T^*T$ is compact. For a function $f$ holomorphic in the unit disk $\DD$ and continuous on $\bar\DD$, we show that $f(T)$ is compact if and only if $f$…

Functional Analysis · Mathematics 2008-09-19 Karim Kellay , Mohamed Zarrabi

Under very general conditions it is shown that if $A$ is a uniform algebra generated by real-analytic functions, then either $A$ consists of all continuous functions or else there exists a disc on which every function in $A$ is holomorphic.…

Complex Variables · Mathematics 2017-10-10 Alexander J. Izzo

Let $D_j\subset\Bbb C^{k_j}$ be a pseudoconvex domain and let $A_j\subset D_j$ be a locally pluripolar set, $j=1,...,N$. Put$$X:=\bigcup_{j=1}^N A_1\times...\times A_{j-1}\times D_j\times A_{j+1}\times...\times A_N\subset\Bbb…

Complex Variables · Mathematics 2007-05-23 Marek Jarnicki , Peter Pflug

We prove simultaneous Universal Approximation of a certain type of Pade Approximants and of Taylor series with the same indexes. This is a generic phenomenon in the space of holomorphic functions in any simply connected domain, as well as…

Complex Variables · Mathematics 2015-03-11 K. Makridis

For separable metrizable spaces $X,Y$ and a metrizable topological group $Z$ by $S(X\times Y,Z)$ we denote the space of all separately continuous functions $f:X\times Y\to Z$ endowed with the topology of layer-wise uniform convergence,…

General Topology · Mathematics 2016-02-23 Taras Banakh

This paper studies the equivalence between generalized holomorphic functions (GHF) and complex analytic functions in the framework of Robinson-Colombeau generalized numbers. In every non-Archimedean ring, the use of ordinary series is…

Functional Analysis · Mathematics 2026-04-21 Sekar Nugraheni , Paolo Giordano

Let (k(n)) n=1,2,... be a strictly increasing sequence of positive integers . We consider a specific sequence of differential operators Tk(n),{\lambda} , n=1,2,... on the space of entire functions , that depend on the sequence (k(n))…

Functional Analysis · Mathematics 2015-06-18 Nikos Tsirivas

For a subfield K of C, we denote by C^K the category of algebras of functions defined on the globally subanalytic sets that are generated by all K-powers and logarithms of positively-valued globally subanalytic functions. For any function f…

Algebraic Geometry · Mathematics 2025-07-09 Georges Comte , Dan J. Miller , Tamara Servi

Let $H(D)$ denote the space of holomorphic functions on the unit disk $D$. We characterize those radial weights $w$ on $D$, for which there exist functions $f, g \in H(D)$ such that the sum $|f| + |g|$ is equivalent to $w$. Also, we obtain…

Complex Variables · Mathematics 2021-08-20 Evgeny Abakumov , Evgueni Doubtsov

In this article we prove a general result which in particular suggests that, on a simply connected domain in C, all the derivatives and anti-derivatives of the generic holomorphic function are unbounded. A similar result holds for the…

Complex Variables · Mathematics 2016-11-17 Maria Siskaki

In this paper, pointwise convergence, uniform convergence and compact convergence of sequences of holomorphic functions on an open subset of the complex plane are compared from a linear point of view. In fact, it is proved the existence of…

Complex Variables · Mathematics 2025-03-14 L. Bernal-González , M. C. Calderón-Moreno , J. López-Salazar , J. A. Prado-Bassas

For a compact subset $K$ of the complex plane $\mathbb C,$ let $C(K)$ denote the algebra of continuous functions on $K$. For an open subset $U \subset K,$ let $A(K,U) \subset C(K)$ be the algebra of functions that are analytic in $U.$ We…

Functional Analysis · Mathematics 2023-08-24 Liming Yang