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Zapiski Nauchnykh Seminarov POMI, 2021, Volume 503, Pages 57–71
(Mi znsl7099)
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This article is cited in 1 scientific paper (total in 1 paper)
Logarithmically absolutely monotone trigonometric functions
O. L. Vinogradov St. Petersburg State University, Mathematics and Mechanics Faculty
Abstract:
We study absolute monotonicity and logarithmic absolute monotonicity for functions $$ f(z)=\dfrac{\cos{\alpha_1z}\cdot\ldots\cdot\cos{\alpha_Mz} \cdot\sin{\beta_1z}\cdot\ldots\cdot\sin{\beta_Nz}} {\cos{\alpha'_1z}\cdot\ldots\cdot\cos{\alpha'_{M'}z} \cdot\sin{\beta'_1z}\cdot\ldots\cdot\sin{\beta'_{N'}z}}z^{N'-N}. $$ Here $N,M,N',M'\in\Bbb Z_+$, $\alpha_j,\alpha_j',\beta_j,\beta_j'\geqslant 0$; if $\beta=0$, then the factor $\sin{\beta z}$ is replaced by $z$; if $N,M,N'$, or $M'$ equals zero, then the corresponding factors are absent. A criterion of logarithmic absolute monotonicity for $f$ is obtained.
We give some applications of absolute monotonicity to sharp inequalities for derivatives and differences of trigonometric polynomials and entire functions of exponential type.
Key words and phrases:
absolutely monotone functions, Bernstein inequality.
Received: 14.06.2021
Citation:
O. L. Vinogradov, “Logarithmically absolutely monotone trigonometric functions”, Investigations on linear operators and function theory. Part 49, Zap. Nauchn. Sem. POMI, 503, POMI, St. Petersburg, 2021, 57–71
Linking options:
https://www.mathnet.ru/eng/znsl7099 https://www.mathnet.ru/eng/znsl/v503/p57
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