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This article is cited in 4 scientific papers (total in 4 papers)
On upper estimates of the partial sums of a trigonometric series in terms of lower estimates
A. S. Belov
Abstract:
Let $\{a_k\}_{k=0}^\infty$ and $\{b_k\}_{k=0}^\infty$ be sequences of real numbers and let $ S_n(x)$ be defined by
$$
S_n(x)=\sum^n_{k=0}\bigl(a_k\cos(kx)+b_k\sin(kx)\bigr),\qquad
n=0,1,\dotsc\,.
$$
It is proved that the estimate
$$
\max_x S_n(x)\leqslant 4a_0 n^{1-\alpha},
$$
holds for each natural number $n$ such that $S_m(x)\geqslant0$ for all $x$ and
$m=1,\,\dots,\,n$. Here $\alpha\in(0,\,1)$ is the unique root of the equation
$$
\int^{3\pi /2}_0 t^{-\alpha}\cos t\,dt=0.
$$
It is proved that the order $n^{1-\alpha}$ in this estimate cannot be improved. Various generalizations of this result are also obtained.
Received: 13.02.1992
Citation:
A. S. Belov, “On upper estimates of the partial sums of a trigonometric series in terms of lower estimates”, Mat. Sb., 183:11 (1992), 55–74; Russian Acad. Sci. Sb. Math., 77:2 (1994), 313–330
Linking options:
https://www.mathnet.ru/eng/sm1089https://doi.org/10.1070/SM1994v077n02ABEH003443 https://www.mathnet.ru/eng/sm/v183/i11/p55
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Abstract page: | 475 | Russian version PDF: | 108 | English version PDF: | 30 | References: | 72 | First page: | 1 |
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