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Holomorphic extendibility and mapping degree

Published online by Cambridge University Press:  23 July 2007

Josip Globevnik
Affiliation:
Institute of Mathematics, Physics and Mechanics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia (josip.globevnik@fmf.uni-lj.si)

Abstract

Let $D$ be a bounded, finitely connected domain in $\mathbb{C}$ without isolated points in the boundary and let $f$ be a continuous function on $bD$. Let $\tilde{f}$ be a continuous extension of $f$ to $\bar{D}$. We prove that $f$ extends holomorphically through $D$ if and only if the degree of $\tilde{f}+h$ is non-negative for every holomorphic function $h$ on $D$ such that $\tilde{f}+h$ is bounded away from $0$ near $bD$.

Type
Research Article
Copyright
2007 Royal Society of Edinburgh

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