Taylor Coefficients of Negative Powers of Schlicht Functions

被引:0
|
作者
Oliver Roth
Karl-Joachim Wirths
机构
[1] Universität Würzburg,Mathematisches Institut
[2] TU Braunschweig,Institut für Analysis
关键词
Taylor coefficients; univalent functions; Löwner’s method; optimization; 30C75; 49K15;
D O I
10.1007/BF03321005
中图分类号
学科分类号
摘要
Let \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\cal S$\end{document} denote the class of normalized schlicht functions in the unit disk. We consider for f ∊ \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}${\cal S}$\end{document} and λ < 0 the Taylor coefficients an (λ, f) of (f(z)/z)λ and prove that ∣an(λ, f)∣ ≤ ∣an(λ, k)∣ for every f ∈ S and every 1 ≤ n ≤ − λ + 1, where k(z) = z(l − z)−2 is the Koebe function. We also give a necessary condition such that the Koebe function maximizes the functional \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sum_{k=1}^n \sigma_k \mid a_k(\lambda,f) \mid^2$$\end{document} in the class \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}${\cal S}$\end{document} for given weights σk ∈ R. These results supplement and complement previous results due to de Branges, Hayman and Hummel and others. Our proofs are based on the Löwner differential equation combined with optimal control methods.
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页码:521 / 533
页数:12
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