On the derivative of Dirichlet series (in Ukrainian)

Author
S.I. Fedynyak
Lviv University, Department of Mechanics and Mathematics
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 $\beta (\sigma) = \frac {\ln \Phi^\prime (\Psi^{-1} (\sigma))}{ \Phi^\prime (\Psi^{-1} (\sigma))}.$
Keywords
Dirichlet series, absolute convergence, maximum modulus, growth function
DOI
doi:10.30970/ms.6.1.53-58
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
Volume
6
Issue
1
Year
1996
Journal
Matematychni Studii
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