Radial growth and variation of univalent functions and of Dirichlet finite holomorphic functions
Colloquium Mathematicum, Tome 69 (1996) no. 1, pp. 19-17
A well known result of Beurling asserts that if f is a function which is analytic in the unit disc $Δ ={z ∈ ℂ : |z|1} $ and if either f is univalent or f has a finite Dirichlet integral then the set of points $e^{iθ}$ for which the radial variation $V(f,e^{iθ})=∫_{0}^{1}|f'(re^{iθ})|dr$ is infinite is a set of logarithmic capacity zero. In this paper we prove that this result is sharp in a very strong sense. Also, we prove that if f is as above then the set of points $e^{iθ}$ such that $(1 - r)|f'(re^{iθ})| ≠ o(1)$ as r → 1 is a set of logarithmic capacity zero. In particular, our results give an answer to a question raised by T. H. MacGregor in 1983.
Keywords:
radial variation, Dirichlet integral, capacity, univalent functions
@article{10_4064_cm_69_1_19_17,
author = {Daniel Girela},
title = {Radial growth and variation of univalent functions and of {Dirichlet} finite holomorphic functions},
journal = {Colloquium Mathematicum},
pages = {19--17},
year = {1996},
volume = {69},
number = {1},
doi = {10.4064/cm-69-1-19-17},
language = {en},
url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-69-1-19-17/}
}
TY - JOUR AU - Daniel Girela TI - Radial growth and variation of univalent functions and of Dirichlet finite holomorphic functions JO - Colloquium Mathematicum PY - 1996 SP - 19 EP - 17 VL - 69 IS - 1 UR - http://geodesic.mathdoc.fr/articles/10.4064/cm-69-1-19-17/ DO - 10.4064/cm-69-1-19-17 LA - en ID - 10_4064_cm_69_1_19_17 ER -
%0 Journal Article %A Daniel Girela %T Radial growth and variation of univalent functions and of Dirichlet finite holomorphic functions %J Colloquium Mathematicum %D 1996 %P 19-17 %V 69 %N 1 %U http://geodesic.mathdoc.fr/articles/10.4064/cm-69-1-19-17/ %R 10.4064/cm-69-1-19-17 %G en %F 10_4064_cm_69_1_19_17
Daniel Girela. Radial growth and variation of univalent functions and of Dirichlet finite holomorphic functions. Colloquium Mathematicum, Tome 69 (1996) no. 1, pp. 19-17. doi: 10.4064/cm-69-1-19-17
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