A study of behavior of the sequence of norm of primitives of functions in Orlicz spaces depending on their spectrum
type: Item
instance of: scholarly article
title: A study of behavior of the sequence of norm of primitives of functions in Orlicz spaces depending on their spectrum
zbMATH Open document ID: 1345.46021
author: Ha Huy Bang
author: Vu Nhat Huy
published in: Tokyo Journal of Mathematics
publication date: 2015-09-29T00:00:00Z
review text: \textit{H. H. Bang} [Trans. Am. Math. Soc. 347, No. 3, 1067--1080 (1995; Zbl 0828.42009)] proved that for \(1\leq p\leq\infty\) any function \(f\in L_p(\mathbb R^n)\), \(f\not\equiv0\), with \(\text{supp}\hat f\) bounded, satisfies \(\lim_{|\alpha|\to\infty}(\| D^\alpha f\|_p / \sup_{\xi\in\text{supp}\hat f}|\xi^\alpha|)^{1/|\alpha|}=1\). This allows to approximate the behaviour of the sequence \(\{\| D^\alpha f\|_p^{1/|\alpha|}\}\) (which is difficult to calculate directly) by the sequence \(\{\sup_{\xi\in\text{supp}\hat f}|\xi^\alpha|^{1/|\alpha|}\}\). The natural question is about the situation when derivatives are replaced by integrals. \textit{V. K. Tuan} answered the question in [J. Fourier Anal. Appl. 7, No. 3, 319--323 (2001; Zbl 0988.94011)] for \(p=2\) and \(n=1\), and the authors did it for \(1\leq p\leq\infty\), \(n=1\), in [J. Approx. Theory 162, No. 6, 1178--1186 (2010; Zbl 1204.46017)], and for \(1\leq p\leq\infty\), \(n\geq1\), in [Dokl. Math. 84, No. 2, 672--674 (2011; Zbl 1243.46015); translation from Dokl. Akad. Nauk 440, No. 4, 456--458 (2011)]. In the present paper, they deal with the \(n\)-dimensional case in Orlicz spaces. For instance, they prove that, for a function \(f\not\equiv0\) from an Orlicz space \(L_\Phi(\mathbb R^n)\) whose spectrum \(\text{supp}\hat f\) is contained in \(\{\xi\in\mathbb R^n: \min\{|\xi_1|,\dots,|\xi_n|\}>\Delta\}\) for some \(\Delta>0\), there exists exactly one sequence of primitives \((I^\alpha f)_{\alpha\in\mathbb Z^n_+}\subset L_\Phi(\mathbb R^n)\) such that the spectrum of \(I^\alpha f\) coincides with the spectrum of \(f\) for all \(\alpha\in\mathbb Z^n_+\), and \(\lim_{|\alpha|\to\infty}(\inf_{\xi\in\text{supp}\hat f}|\xi^\alpha|\| I^\alpha f\|_\Phi)^{1/|\alpha|}=1\).
Mathematics Subject Classification ID: 46E30
Mathematics Subject Classification ID: 42B10
zbMATH DE Number: 6486363
zbMATH Keywords: Orlicz space
zbMATH Keywords: Fourier transform
zbMATH Keywords: spectrum
zbMATH Keywords: primitive function
zbMATH Keywords: norm
reviewed by: Jiří Rákosník
MaRDI profile type: Publication
full work available at URL: https://doi.org/10.3836/tjm/1437506250
OpenAlex ID: W1488173512
DOI: 10.3836/TJM/1437506250
description: scientific article; zbMATH DE number 6486363