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Let $F$ be a holomorphic map from an open disc $D \subset \mathbb{C}^n$ to $\mathbb{C}^n$ and suppose $F$ extends continuously to $\overline{D}$. Do the maps $\partial F_i / \partial z_k$ extend continuously to $\overline{D}$?

Thanks

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    Uitstekend, @Wim.2012-04-04

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The partial derivatives do not necessarily extend continuously to the closed disc. WimC gave $F(z)=\sqrt{1-z}$ as a counterexample in one dimension. In any dimension, $F(z)=(\sqrt{1-z_1},\dots,\sqrt{1-z_n})$ has the same property: each partial fails to have a continuous extension, and is not even bounded.

A situation in which one might hope for boundary smoothness is when $F$ is a biholomorphic map onto a smooth domain. In one dimension there is a very satisfactory result called the Kellogg-Warschawski theorem. The situation in several variables is much more involved: see this brief overview.