Bohr Phenomenon for Certain Close-to-Convex Analytic Functions

被引:0
作者
Vasudevarao Allu
Himadri Halder
机构
[1] Indian Institute of Technology Bhubaneswar,School of Basic Science
来源
Computational Methods and Function Theory | 2022年 / 22卷
关键词
Starlike; Convex; Close-to-convex; Quasi-convex functions; Conjugate points; Symmetric points; Subordination; Majorant series; Bohr radius; Primary 30C45; 30C50; 30C80;
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学科分类号
摘要
We say that a class G\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathcal {G}}$$\end{document} of analytic functions f of the form f(z)=∑n=0∞anzn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$f(z)=\sum _{n=0}^{\infty } a_{n}z^{n}$$\end{document} in the unit disk D:={z∈C:|z|<1}\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathbb {D}}:=\{z\in {\mathbb {C}}: |z|<1\}$$\end{document} satisfies a Bohr phenomenon if for the largest radius Rf<1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_{f}<1$$\end{document}, the following inequality ∑n=1∞|anzn|≤d(f(0),∂f(D))\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\begin{aligned} \sum \limits _{n=1}^{\infty } |a_{n}z^{n}| \le d(f(0),\partial f({\mathbb {D}}) ) \end{aligned}$$\end{document}holds for |z|=r≤Rf\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$|z|=r\le R_{f}$$\end{document} and for all functions f∈G\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$f \in {\mathcal {G}}$$\end{document}. The largest radius Rf\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_{f}$$\end{document} is called Bohr radius for the class G\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathcal {G}}$$\end{document}. In this article, we obtain the Bohr radius for certain subclasses of close-to-convex analytic functions. We establish the Bohr phenomenon for certain analytic classes Sc∗(ϕ),Cc(ϕ),Cs∗(ϕ),Ks(ϕ)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathcal {S}}_{c}^{*}(\phi ),\,{\mathcal {C}}_{c}(\phi ),\, {\mathcal {C}}_{s}^{*}(\phi ),\, {\mathcal {K}}_{s}(\phi )$$\end{document} and obtain the radius Rf\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_{f}$$\end{document} such that the Bohr phenomenon for these classes holds for |z|=r≤Rf\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$|z|=r\le R_{f}$$\end{document}. As a consequence of these results, we obtain several interesting corollaries about the Bohr phenomenon for the aforesaid classes.
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页码:491 / 517
页数:26
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