On the derivative of Dirichlet series (in Ukrainian) |
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| Author |
Lviv University, Department of Mechanics and Mathematics
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| Abstract |
For an absolutely convergent in $(-\|,A)$ Dirichlet series
$F(s) = \Sigma_{n=0}^{\|} a_n \text{e}^{s\lambda_n },\; s=\sigma+it$,
$0 < \lambda_n\uparrow +\|\; (n\to \|)$,
$A \in (-\|,+\|]$, let $M(\sigma ,F) = \sup\{ |F(\sigma +it)| : t \in \Bbb{R}\}$
and $S_1 (\sigma ,F) =\frac {M(\sigma ,F^\prime )}{M(\sigma ,F)}$, $\sigma < A$.
Let $\Omega(A)$, $-\| < A\le +\|$ be the class of positive unlimited on $(-\|,A)$
functions $ \Phi$ for which the derivative $\Phi^\prime$ is a positive, continuous
and increasing function on $(-\|,A)$ with limit $+\|$.
Let $\Psi (x)= x-\frac{\Phi (x)}{\Phi^\prime(x)}$.
We have the following assertion.
Let $q \in (0,+\|)$, $A\in (-\|,+\|]$, and let $\Phi \in \Omega(A)$ be a
function such that
$\ln \Phi^\prime (\sigma) \le \frac{1}{q}\bigl(\Phi(\sigma)+(A-\sigma)\Phi^\prime(\sigma)\bigr)$,
$\sigma_0\le\sigma < A. $
If for a Dirichlet series $F(s)$ we have
$ n(t)\le t^q \;\;(t\ge t_{\circ})$ and
$$\varlimsup_{\sigma \to A} \frac{\ln M(\sigma,F)}{\Phi (\sigma)}=1,$$
then
$$ \varlimsup_{\sigma \to A} \frac{S_1(\sigma,F)}{\Phi^\prime(\Psi^{-1}(\sigma+q\beta(\sigma)))} \le 1 \le
\varlimsup_{\sigma \to A} \frac{S_1(\sigma,F)}{\Phi^\prime(\sigma)},$$
where
$\beta (\sigma) = \frac {\ln \Phi^\prime (\Psi^{-1} (\sigma))}{ \Phi^\prime (\Psi^{-1} (\sigma))}.$
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| Keywords |
Dirichlet series, absolute convergence, maximum modulus, growth function
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| DOI |
doi:10.30970/ms.6.1.53-58
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Reference |
1. Шеремета М.Н. О производной целой функции // Укр. мат. журн. 1988. Т.40, №2. C.219–224.
2. Шеремета М.М. Цiлi ряди Дiрiхле. – K.: IСДО, 1993, 105c. 3. Kövari T. A note on entire functions // Acad. Sci. Hung. 1958. V.8, P.87–90. 4. Левин Б.Я. Распределение корней целых функций. – М.: Гостех-издат, 1956, 632c. 5. Мак-Лейн Г. Асимптотические значения голоморфных функций. – М.:Мир, 1966, 103c. Львiвський унiверситет, механіко-математичний факультет |
| Pages |
53-58
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| Volume |
6
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| Issue |
1
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| Year |
1996
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| Journal |
Matematychni Studii
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| Full text of paper | |
| Table of content of issue |