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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

In this paper we study an algebraic and topological structure inside the following sets of special functions: Bloch functions defined on the open unit disk that are unbounded and analytic functions of bounded type defined a Banach algebra E…

Functional Analysis · Mathematics 2020-11-16 M. Lilian Lourenço , Daniela M. Vieira

A Hilbert point in $H^p(\mathbb{T}^d)$, for $d\geq1$ and $1\leq p \leq \infty$, is a nontrivial function $\varphi$ in $H^p(\mathbb{T}^d)$ such that $\| \varphi \|_{H^p(\mathbb{T}^d)} \leq \|\varphi + f\|_{H^p(\mathbb{T}^d)}$ whenever $f$ is…

Functional Analysis · Mathematics 2023-07-07 Ole Fredrik Brevig , Joaquim Ortega-Cerdà , Kristian Seip

Let \[ \Gamma = \{(z+w, zw): |z|\leq 1, |w|\leq 1\} \subset \mathbb{C}^2. \] A $\Gamma$-inner function is defined to be a holomorphic map $h$ from the unit disc $\mathbb{D}$ to $\Gamma$ whose boundary values at almost all points of the unit…

Complex Variables · Mathematics 2016-11-01 Jim Agler , Zinaida A. Lykova , N. J. Young

For $\lambda\ge0$, a $C^2$ function $f$ defined on the unit disk ${{\mathbb D}}$ is said to be $\lambda$-analytic if $D_{\bar{z}}f=0$, where $D_{\bar{z}}$ is the (complex) Dunkl operator given by…

Complex Variables · Mathematics 2023-07-04 Zhongkai Li , Haihua Wei

For an analytic function $f(z)=\sum_{k=0}^\infty a_kz^k$ on a neighbourhood of a closed disc $D\subset {\bf C}$, we give assumptions, in terms of the Taylor coefficients $a_k$ of $f$, under which the number of intersection points of the…

Algebraic Geometry · Mathematics 2017-12-19 Georges Comte , Yosef Yomdin

Let $E$ be a subset of the unit disc $U$ of the complex plane $\CC$. Recall that $H^p(U)$ is the space of all holomorphic functions $g$ on $U$ for which $\|g\|_{H^p}$ $<$ $\infty$. Put \begin{equation} C_p(\epsilon, R) = \sup \{\sup_{|z|…

Complex Variables · Mathematics 2007-05-23 Dang Duc Trong , Truong Trung Tuyen

We construct a Schauder basis for the space $Hol(\mathbb D)$, the space of holomorphic functions on the closed unit disk, consisting entirely of finite Blaschke products. The expansion coefficients are given explicitly. Our result remains…

Complex Variables · Mathematics 2026-02-03 Emmanuel Fricain , Javad Mashreghi , Mostafa Nasri , Maëva Ostermann

We establish the first pointwise ergodic theorems along thin sets of prime numbers; a set with zero density with respect to the primes. For instance we will be able to achieve this with the Piatetski-Shapiro primes. Our methods will be…

Classical Analysis and ODEs · Mathematics 2014-01-28 Mariusz Mirek

Given an inner function $\theta$ on the unit disk, let $K^p_\theta:=H^p\cap\theta\bar z\bar{H^p}$ be the associated star-invariant subspace of the Hardy space $H^p$. Also, we put $K_{*\theta}:=K^2_\theta\cap{\rm BMO}$. Assuming that…

Complex Variables · Mathematics 2022-10-18 Konstantin M. Dyakonov

We give a condition under which a divisor X in a bounded convex domain of finite type D in C^n is the zero set of a function in a Hardy space H^p(D) for some p \textgreater{} 0. This generalizes Varopoulos' result [Zero sets of H^p…

Complex Variables · Mathematics 2016-02-12 William Alexandre

We consider Hilbert spaces of analytic functions in the disk with a normalized reproducing kernel and such that the backward shift $f(z) \mapsto \frac{f(z)-f(0)}{z}$ is a contraction on the space. We present a model for this operator and…

Functional Analysis · Mathematics 2019-01-15 Alexandru Aleman , Bartosz Malman

We discuss the notion of an inner function for spaces of analytic functions in multiply connected domains in $\mathbb{C}$, giving a historical overview and comparing several possible definitions. We explore connections between inner…

Complex Variables · Mathematics 2019-07-18 Catherine Bénéteau , Matthew Fleeman , Dmitry Khavinson , Alan A. Sola

A description of the Bloch functions that can be approximated in the Bloch norm by functions in the Hardy space $H^p$ of the unit ball of $\Cn$ for $0<p<\infty$ is given. When $0<p\leq1$, the result is new even in the case of the unit disk.

Complex Variables · Mathematics 2014-08-21 Petros Galanopoulos , Nacho Monreal Galán , Jordi Pau

We give a generalization of the notion of finite Blaschke products from the perspective of generalized inner functions in various reproducing kernel Hilbert spaces. Further, we study precisely how these functions relate to the so-called…

Functional Analysis · Mathematics 2022-06-07 Christopher Felder , Trieu Le

For analytic functions $g$ on the unit disc with non-negative Maclaurin coefficients, we describe the boundedness and compactness of the integral operator $T_g(f)(z)=\int_0^zf(\zeta)g'(\zeta)\,d\zeta$ from a space $X$ of analytic functions…

Complex Variables · Mathematics 2021-03-17 José Ángel Peláez , Jouni Rättyä , Fanglei Wu

This paper deals with representing in concrete fashion those Hilbert spaces that are vector subspaces of the Hardy spaces $H^p(\bb D^n) \ (1\le p\le \infty)$ that remain invariant under the action of coordinate wise multiplication by an…

Functional Analysis · Mathematics 2022-01-19 Sneh Lata , Sushant Pokhriyal , Dinesh Singh

The purpose of this expository note is to give a proof of a Schur-type theorem that characterizes the inner functions in terms of their Taylor coefficients. In view of Beurling's theorem, this provides a sequential characterization of the…

Complex Variables · Mathematics 2014-12-31 Dragan Vukotić

In this article, we introduce a general approach for deriving zero-free half-planes for the Riemann zeta function $\zeta$ by identifying topological vector spaces of analytic functions with specific properties. This approach is applied to…

Number Theory · Mathematics 2024-09-04 Aditya Ghosh , Kobi Kremnizer , S. Waleed Noor , Charles F. Santos

Following Gorkin, Mortini, and Nikolski, we say that an inner function $I$ in $H^\infty$ of the unit disc has the WEP property if its modulus at a point $z$ is bounded from below by a function of the distance from $z$ to the zero set of…

Complex Variables · Mathematics 2017-10-24 Alexander Borichev , Artur Nicolau , Pascal J. Thomas