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In this paper we initiate the study of composition operators on the noncommutative Hardy space $H^2_{\bf ball}$. Several classical results about composition operators (boundedness, norm estimates, spectral properties, compactness,…

Functional Analysis · Mathematics 2011-11-15 Gelu Popescu

We give examples of results on composition operators connected with lens maps. The first two concern the approximation numbers of those operators acting on the usual Hardy space $H^2$. The last ones are connected with Hardy-Orlicz and…

Functional Analysis · Mathematics 2012-01-04 Pascal Lefèvre , Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza

For alpha>0 we consider the system l_k^{(alpha-1)/2}(x) of the Laguerre functions which are eigenfunctions of the differential operator Lf =-\frac{d^2}{dx^2}f-\frac{alpha}{x}\frac{d}{dx}f+x^2 f. We define an atomic Hardy space H^1_{at}(X),…

Functional Analysis · Mathematics 2011-11-29 Marcin Preisner

Let $\Gamma$ be a graph. Under suitable geometric assumptions on $\Gamma$, we give several equivalent characterizations of Sobolev and Hardy-Sobolev spaces on $\Gamma$, in terms of maximal functionals, Haj{\l} asz type functionals or atomic…

Classical Analysis and ODEs · Mathematics 2012-10-12 Emmanuel Russ , Maamoun Turkawi

We realize norms of most composition operators acting on the Hardy space with linear fractional symbol as roots of hypergeometric functions. This realization leads to simple necessary and sufficient conditions on the symbol to exhibit…

Complex Variables · Mathematics 2007-05-23 Estelle L. Basor , Dylan Q. Retsek

In this paper we investigate the numerical ranges of composition operators whose symbols are elliptic automorphisms of finite orders, on the Hilbert Hardy space $H^2(D)$.

Functional Analysis · Mathematics 2023-02-22 Yong-Xin Gao , Ze-Hua Zhou

The Hardy operator is not bounded on the space of integrable functions on the positive half-line and its discrete counterpart on summable sequences. we introduce a modified Hardy operator obtained by subtracting a natural corrective term,…

Classical Analysis and ODEs · Mathematics 2026-03-24 Samson Owusu-Ensaw , Benoit F. Sehba , Ransford T. Tweneboanah

This paper consists in a first study of the Hardy space H1 in the rational Dunkl setting. Following Uchiyama's approach, we characterizee H1 atomically and by means of the heat maximal operator. We also obtain a Fourier multiplier theorem…

Classical Analysis and ODEs · Mathematics 2013-09-26 Jean-Philippe Anker , Néjib Ben Salem , Jacek Dziubanski , Nabila Hamda

We obtain a necessary and sufficient condition for a weighted composition operator to be co-isometric on a general weighted Hardy space of analytic functions in the unit disk whose reproducing kernel has the usual natural form. This turns…

Complex Variables · Mathematics 2021-07-14 María J. Martín , Alejandro Mas , Dragan Vukotić

Let $\mu$ be a non-negative Radon measure on ${\mathbb R}^d$ which only satisfies the polynomial growth condition. Let ${\mathcal Y}$ be a Banach space and $H^1(\mu)$ the Hardy space of Tolsa. In this paper, the authors prove that a linear…

Functional Analysis · Mathematics 2009-06-09 Dachun Yang , Dongyong Yang

In this paper we consider the Hardy-Lorentz spaces $H^{p,q}(R^n)$, with $0<p\le 1$, $0<q\le \infty$. We discuss the atomic decomposition of the elements in these spaces, their interpolation properties, and the behavior of singular integrals…

Classical Analysis and ODEs · Mathematics 2013-10-15 Wael Abu-Shammala , Alberto Torchinsky

We generalize, on one hand, some results known for composition operators on Hardy spaces to the case of Hardy-Orlicz spaces $H^\Psi$: construction of a "slow" Blaschke product giving a non-compact composition operator on $H^\Psi$;…

Functional Analysis · Mathematics 2010-01-20 Pascal Lefèvre , Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza

Several possible notions of Hardy-Sobolev spaces on a Riemannian manifold with a doubling measure are considered. Under the assumption of a Poincar\'e inequality, the space $\Mone$, defined by Haj{\l}asz, is identified with a Hardy-Sobolev…

Differential Geometry · Mathematics 2014-03-06 Nadine Badr , Galia Dafni

We characterize the space of multipliers from the Hardy space of Dirichlet series $\mathcal H_p$ into $\mathcal H_q$ for every $1 \leq p,q \leq \infty$. For a fixed Dirichlet series, we also investigate some structural properties of its…

Complex Variables · Mathematics 2022-05-18 Tomás Fernandez Vidal , Daniel Galicer , Pablo Sevilla-Peris

The primary aim of this paper is to characterize the uniformly locally univalent harmonic mappings in the unit disk. Then, we obtain sharp distortion, growth and covering theorems for one parameter family ${\mathcal B}_{H}(\lambda)$ of…

Complex Variables · Mathematics 2016-01-07 S. Ponnusamy , J. Qiao , X. Wang

Let $L$ be a linear operator on $L^2(\mathbb R^n)$ generating an analytic semigroup $\{e^{-tL}\}_{t\ge0}$ with kernels having pointwise upper bounds and $p(\cdot):\ \mathbb R^n\to(0,1]$ be a variable exponent function satisfying the…

Classical Analysis and ODEs · Mathematics 2015-12-21 Dachun Yang , Ciqiang Zhuo

Let $p(\cdot):\ \mathbb R^n\to(0,1]$ be a variable exponent function satisfying the globally log-H\"older continuous condition and $L$ a one to one operator of type $\omega$ in $L^2({\mathbb R}^n)$, with $\omega\in[0,\,\pi/2)$, which has a…

Classical Analysis and ODEs · Mathematics 2018-05-22 Ciqiang Zhuo , Dachun Yang

We present a natural family of Hilbert function spaces on the d-dimensional complex unit ball and classify which of them satisfy that subsets of the ball yield isometrically isomorphic subspaces if and only if there is an analytic…

Functional Analysis · Mathematics 2021-04-23 Danny Ofek , Gilad Sofer

In this paper we establish inclusions and noninclusions between various Hardy type spaces on noncompact Riemannian manifolds $M$ with Ricci curvature bounded from below, positive injectivity radius and spectral gap. Our first main result…

Functional Analysis · Mathematics 2024-06-10 Alessio Martini , Stefano Meda , Maria Vallarino , Giona Veronelli

The main aim of this article is to establish boundedness of singular integrals with non-smooth kernels on product spaces. Let $L_1$ and $L_2$ be non-negative self-adjoint operators on $L^2(\mathbb{R}^{n_1})$ and $L^2(\mathbb{R}^{n_2})$,…

Classical Analysis and ODEs · Mathematics 2015-09-28 Xuan Thinh Duong , Ji Li , Lixin Yan