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We consider Bergman spaces and variations of them in one or several complex variables. For some domains we show that in these spaces the generic function is totally unbounded and hence non - extendable. We also show that the generic…

Complex Variables · Mathematics 2017-04-10 T. Hatziafratis , K. Kioulafa , V. Nestoridis

Under certain hypotheses on the Banach space $X$, we show that the set of $N$-homogeneous polynomials from $X$ to any dual space, whose Aron-Berner extensions are norm attaining, is dense in the space of all continuous $N$-homogeneous…

Functional Analysis · Mathematics 2013-04-23 Daniel Carando , Silvia Lassalle , Martín Mazzitelli

We prove $L^p$ quantitative differentiability estimates for functions defined on uniformly rectifiable subsets of the Euclidean space. More precisely, we show that a Dorronsoro-type theorem holds in this context: the $L^p$ norm of the…

Classical Analysis and ODEs · Mathematics 2025-11-14 Jonas Azzam , Mihalis Mourgoglou , Michele Villa

Let $C_b(K)$ be the set of all bounded continuous (real or complex) functions on a complete metric space $K$ and $A$ a closed subspace of $C_b(K)$. Using the variational method, it is shown that the set of all strong peak functions in $A$…

Functional Analysis · Mathematics 2007-05-23 Han Ju Lee

We discuss approximation of extremal functions by polynomials in the weighted Bergman spaces $A^p_\alpha$ where $-1 < \alpha < 0$ and $-1 < \alpha < p-2$. We obtain bounds on how close the approximation is to the true extremal function in…

Complex Variables · Mathematics 2017-05-19 Timothy Ferguson

The main aim of this paper is to prove a Bishop-Phelps-Bollob\'as type theorem on the unital uniform algebra A_{w^*u}(B_{X^*}) consisting of all w^*-uniformly continuous functions on the closed unit ball B_{X^*} which are holomorphic on the…

Functional Analysis · Mathematics 2017-07-24 Sheldon Dantas , Domingo García , Sun Kwang Kim , Un Young Kim , Han Ju Lee , Manuel Maestre

We take a unifying and new approach toward polynomial and trigonometric approximation in an arbitrary number of variables, resulting in a precise and general ready-to-use tool that anyone can easily apply in new situations of interest. The…

Classical Analysis and ODEs · Mathematics 2023-05-31 Marcel de Jeu

In most classical holomorphic function spaces on the unit disk in which the polynomials are dense, a function $f$ can be approximated in norm by its dilates $f_r(z):=f(rz)~(r<1)$, in other words, $\lim_{r\to1^-}\|f_r-f\|=0$. We construct a…

Complex Variables · Mathematics 2019-02-18 Javad Mashreghi , Thomas Ransford

In previous works, an approach to the study of cyclic functions in reproducing kernel Hilbert spaces has been presented, based on the study of so called \emph{optimal polynomial approximants}. In the present article, we extend such approach…

Classical Analysis and ODEs · Mathematics 2020-06-08 Daniel Seco , Roberto Téllez

We study the density of polynomials in $H^2(\Omega,e^{-\varphi})$, the space of square integrable holomorphic functions in a bounded domain $\Omega$ in $\mathbb{C}$, where $\varphi$ is a subharmonic function. In particular, we prove that…

Complex Variables · Mathematics 2019-03-01 Séverine Biard , John Erik Fornæss , Jujie Wu

In most classical holomorphic function spaces on the unit disk, a function $f$ can be approximated in the norm of the space by its dilates $f\_r(z):=f(rz)~(r \textless{} 1)$. We show that this is \emph{not} the case for the de…

Functional Analysis · Mathematics 2015-01-14 O. El-Fallah , E. Fricain , K. Kellay , J. Mashreghi , Ransford Tom

We enhance the approximation capabilities of algebraic polynomials by composing them with homeomorphisms. This composition yields families of functions that remain dense in the space of continuous functions, while enabling more accurate…

Numerical Analysis · Mathematics 2025-12-17 Álvaro Fernández Corral , Yahya Saleh

We study several connected problems of holomorphic function spaces on homogeneous Siegel domains. The main object of our study concerns weighted mixed norm Bergman spaces on homogeneous Siegel domains of type II. These problems include:…

Complex Variables · Mathematics 2022-12-20 Mattia Calzi , Marco M. Peloso

We prove matching direct and inverse theorems for uniform polynomial approximation with $A^*$ weights (a subclass of doubling weights suitable for approximation in the $L_\infty$ norm) having finitely many zeros and not too "rapidly…

Classical Analysis and ODEs · Mathematics 2015-10-27 Kirill A. Kopotun

We study comparison of Lp norms of polynomials on the sphere with respect to doubling measures. From our description it follows an uncertainty principle for square integrable functions on the sphere. We consider also weighted uniform…

Classical Analysis and ODEs · Mathematics 2024-10-18 Jordi Marzo , Joaquim Ortega-Cerdà

We provide lower bounds for the norms of embeddings between $\boldsymbol{\gamma}$-weighted Anchored and ANOVA spaces of $s$-variate functions with mixed partial derivatives of order one bounded in $L_p$ norm ($p\in[1,\infty]$). In…

Numerical Analysis · Mathematics 2015-11-19 Peter Kritzer , Friedrich Pillichshammer , G. W. Wasilkowski

We study differentiability properties in a particular case of the Palmer's linearization Theorem, which states the existence of an homeomorphism $H$ between the solutions of a linear ODE system having exponential dichotomy and a quasilinear…

Classical Analysis and ODEs · Mathematics 2015-12-07 Alvaro Castañeda , Gonzalo Robledo

We display four approximation theorems for manifold-valued mappings. The first one approximates holomorphic embeddings on pseudoconvex domains in $\Bbb C^n$ with holomorphic embeddings with dense images. The second theorem approximates…

Complex Variables · Mathematics 2023-06-21 Giovanni Domenico Di Salvo

We consider $\gamma$-weighted anchored and ANOVA spaces of functions with mixed first order partial derivatives bounded in a weighted $L_p$ norm with $1 \leq p \leq \infty$. The domain of the functions is $D^d$, where $D \subseteq…

Numerical Analysis · Mathematics 2021-02-09 Michael Gnewuch , Mario Hefter , Aicke Hinrichs , Klaus Ritter , Grzegorz W. Wasilkowski

Let $\mathcal{H}ol(B_d)$ denote the space of holomorphic functions on the unit ball $B_d$ of $\mathbb{C}^d$, $d\ge 1$. Given a log-convex strictly positive weight $w(r)$ on $[0,1)$, we construct a function $f\in\mathcal{H}ol(B_d)$ such that…

Complex Variables · Mathematics 2017-06-08 Evgueni Doubtsov