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This article is cited in 17 scientific papers (total in 17 papers)
On convergence of Fourier series in complete orthonormal systems in the $L^1$-metric and almost everywhere
M. G. Grigoryan Yerevan State University
Abstract:
It is proved that if $\{\varphi_n(x)\}$ is a complete orthonormal system of bounded functions and $\varepsilon>0$, then there exists a measurable set $E\subset[0,1]$ with $|E|>1-\varepsilon$ such that
1) for any function $f(x)\in L[0,1]$ there exists a function $g(x)\in L^1[0,1]$ with $g(x)=f(x)$ on $E$ and such that the Fourier series of $g(x)$ in the system $\{\varphi_n(x)\}$ converges in the $L^1$-metric; and
2) there exists a subsequence of natural numbers $m_k\nearrow\infty$ such that for any function $f(x)\in L^1[0,1]$ there exists a function $g(x)\in L^1[0,1]$ such that $g(x)=f(x)$ for $x\in E$, $\displaystyle\lim_{k\to\infty}\sum\limits_{n=1}^{m_k}\alpha_n(g)\varphi_n(x)=g(x)$ almost everywhere on $[0,1]$, and $\{\alpha_n(g)\}\in l_p$ for all $p>2$, where $\displaystyle\alpha_n(g)=\int_0^1g(x)\varphi_n(x)\,dx$, $n=1,2\dots$ .
Received: 23.12.1988 and 27.03.1990
Citation:
M. G. Grigoryan, “On convergence of Fourier series in complete orthonormal systems in the $L^1$-metric and almost everywhere”, Mat. Sb., 181:8 (1990), 1011–1030; Math. USSR-Sb., 70:2 (1991), 445–466
Linking options:
https://www.mathnet.ru/eng/sm1206https://doi.org/10.1070/SM1991v070n02ABEH002124 https://www.mathnet.ru/eng/sm/v181/i8/p1011
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Abstract page: | 414 | Russian version PDF: | 138 | English version PDF: | 19 | References: | 60 | First page: | 1 |
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