z-logo
open-access-imgOpen Access
Pseudostarlike and pseudoconvex Dirichlet series of the order $\alpha$ and the type $\beta$
Author(s) -
М. М. Sheremeta
Publication year - 2020
Publication title -
matematičnì studìï/matematičnì studìï
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.482
H-Index - 8
eISSN - 2411-0620
pISSN - 1027-4634
DOI - 10.30970/ms.54.1.23-31
Subject(s) - order (exchange) , type (biology) , lambda , dirichlet series , combinatorics , mathematics , beta (programming language) , dirichlet distribution , physics , mathematical analysis , quantum mechanics , ecology , finance , computer science , programming language , economics , boundary value problem , biology
The concepts of the pseudostarlikeness of order $\alpha\in [0,\,1)$ and type $\beta\in (0,\,1]$ and the pseudoconvexity of order $\alpha$ and type $\beta$ are introduced for Dirichlet series with null abscissa of absolute convergence. In terms of coefficients, the pseudostarlikeness and the pseudoconvexity criteria of order $\alpha$ and type $\beta$ are proved.Let $h\ge 1$, $\Lambda=(\lambda_k)$ be an increasing to $+\infty$ sequence of positive numbers ($\lambda_1>h$. We call a conformal function of the form $F(s)=e^{sh}+\sum\nolimits_{k=1}^{\infty}f_k\exp\{s\lambda_k\}, \ s=\sigma+it,$in $\Pi_0=\{s\colon \, \text{Re}\,s<0\}$ pseudostarlike of order $\alpha\in [0,\,1)$ and type$\beta \in (0,\,1]$ if\begin{equation*}\left|\frac{F'(s)}{F(s)}-h\right|<\beta\left|\frac{F'(s)}{F(s)}-(2\alpha-h)\right|,\quad s\in \Pi_0.\end{equation*}The main results of the article are contained in Theorems 1 and 2. Theorem 1 states: \textit{If $\alpha \in [0, \, 1)$ and $\beta \in (0, \, 1]$ such that\begin{equation*}\sum\limits_{k=1}^{\infty}\{(1+\beta)\lambda_k -2\beta\alpha -h(1-\beta)\}|f_k|\le 2\beta (h-\alpha)\label{t7}\end{equation*}then the function $F$ is pseudostarlike of order $\alpha$ and type $\beta$.}The corresponding results for Hadamard compositions of such series are also established.

The content you want is available to Zendy users.

Already have an account? Click here to sign in.
Having issues? You can contact us here