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Being motivated by general interest as well as by certain concrete problems of Fourier Analysis, we construct analogs of the Lp spaces for measures. It turns out that most of standard properties of the usual Lp spaces for functions are…

Functional Analysis · Mathematics 2023-01-10 Laura De Carli , Eli Liflyand

In this paper, equivalence constants between various polynomial norms are calculated. As an application, we also obtain sharp values of the Hardy--Littlewood constants for $2$-homogeneous polynomials on $\ell_p^2$ spaces, $2<p\leq\infty$…

The paper concerns the uniform polynomial approximation of a function $f$, continuous on the unit Euclidean sphere of ${\mathbb R}^3$ and known only at a finite number of points that are somehow uniformly distributed on the sphere. First we…

Numerical Analysis · Mathematics 2018-08-10 Woula Themistoclakis , Marc Van Barel

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

We investigate the uniform approximation provided by least squares polynomials on the unit Euclidean sphere $\mathbb{S}^q$ in $\mathbb{R}^{q+1}$, with $q\ge 2$. Like any other polynomial projection, the study concerns the growth, as the…

Numerical Analysis · Mathematics 2018-08-13 Woula Themistoclakis , Marc Van Barel

This paper studies the uncertainty principle for spherical $h$-harmonic expansions on the unit sphere of $\mathbb{R}^d$ associated with a weight function invariant under a general finite reflection group, which is in full analogy with the…

Classical Analysis and ODEs · Mathematics 2015-11-18 Han Feng

In this paper we introduce a polynomial frame on the unit sphere $\sph$ of $\mathbb{R}^d$, for which every distribution has a wavelet-type decomposition. More importantly, we prove that many function spaces on the sphere $\sph$, such as…

Classical Analysis and ODEs · Mathematics 2007-05-23 Feng Dai

The problem of replacing an integral norm with respect to a given probability measure by the corresponding integral norm with respect to a discrete measure is discussed in the paper. The above problem is studied for elements of finite…

Numerical Analysis · Mathematics 2019-11-01 F. Dai , A. Prymak , V. N. Temlyakov , S. Tikhonov

We prove estimates for the $L^p$-norms of systems of functions and divergence free vector functions that are orthonormal in the Sobolev space $H^1$ on the 2D sphere. As a corollary, order sharp constants in the embedding $H^1\hookrightarrow…

Analysis of PDEs · Mathematics 2022-04-27 Alexei Ilyin , Sergey Zelik

We prove upper bounds on the $L^p$ norms of eigenfunctions of the discrete Laplacian on regular graphs. We then apply these ideas to study the $L^p$ norms of joint eigenfunctions of the Laplacian and an averaging operator over a finite…

Spectral Theory · Mathematics 2017-10-31 Shimon Brooks , Etienne Le Masson

We present a refinement of a known entropic inequality on the sphere, finding suitable conditions under which the uniform probability measure on the sphere behaves asymptomatically like the Gaussian measure on $\mathbb{R}^N$ with respect to…

Functional Analysis · Mathematics 2015-04-02 Amit Einav

We establish an inequality of different metrics for algebraic polynomials.

Classical Analysis and ODEs · Mathematics 2016-06-21 Roman Veprintsev

This is a survey on best polynomial approximation on the unit sphere and the unit ball. The central problem is to describe the approximation behavior of a function by polynomials via smoothness of the function. A major effort is to identify…

Classical Analysis and ODEs · Mathematics 2014-02-25 Yuan Xu

We study approximation properties of weighted $\mathrm{L}^2$-orthogonal projectors onto spaces of polynomials of bounded degree in the Euclidean unit ball, where the weight is of the reflection-invariant form $(1-\lVert x \rVert^2)^\alpha…

Classical Analysis and ODEs · Mathematics 2020-11-05 Gonzalo A. Benavides , Leonardo E. Figueroa

We study holomorphic functions attaining weighted norms and its connections with the classical theory of norm attaining holomorphic functions. We prove that there are polynomials on $\ell_p$ which attain their weighted but not their…

Functional Analysis · Mathematics 2022-06-23 Sheldon Dantas , Rubén Medina

We formulate and discuss a necessary and sufficient condition for polynomials to be dense in a space of continuous functions on the real line, with respect to Bernstein's weighted uniform norm. Equivalently, for a positive finite measure…

Complex Variables · Mathematics 2011-11-01 Alexei Poltoratski

We prove that the previously established inequality of different metrics for algebraic polynomials is sharp in the sense of order.

Classical Analysis and ODEs · Mathematics 2016-07-06 Roman Veprintsev

We present a new proof of the sphere covering inequality in the spirit of comparison geometry, and as a byproduct we find another sphere covering inequality which can be viewed as the dual of the original one. We also prove sphere covering…

Analysis of PDEs · Mathematics 2019-01-02 Changfeng Gui , Fengbo Hang , Amir Moradifam

In this paper we give different estimates between Lebesgue norms of quadratic time-frequency representations. We show that, in some cases, it is not possible to have such bounds in classical $L^p$ spaces, but the Lebesgue norm needs to be…

Functional Analysis · Mathematics 2024-02-28 Angela A. Albanese , Claudio Mele , Alessandro Oliaro

The purpose of this paper is to establish L^p error estimates, a Bernstein inequality, and inverse theorems for approximation by a space comprising spherical basis functions located at scattered sites on the unit n-sphere. In particular,…

Functional Analysis · Mathematics 2008-10-29 H. N. Mhaskar , F. J. Narcowich , J. Prestin , J. D. Ward
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