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arXiv · 1106.0936

Gunning-Narasimhan's theorem with a growth condition

Franc Forstneric·Takeo Ohsawa
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Abstract

Given a compact Riemann surface X and a point x_0 in X, we construct a holomorphic function without critical points on the punctured Riemann surface R = X - x_0 which is of finite order at the point x_0. This complements the result of Gunning and Narasimhan from 1967 who constructed a noncritical holomorphic function on every open Riemann surface, but without imposing any growth condition. On the other hand, if the genus of X is at least one, then we show that every algebraic function on R admits a critical point. Our proof also shows that every cohomology class in H^1(X;C) is represented as a de Rham class by a nowhere vanishing holomorphic one-form of finite order on the punctured surface X-x_0.

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Franc Forstneric, Takeo Ohsawa. 2011-06-05. Gunning-Narasimhan's theorem with a growth condition. https://doi.org/10.1007/s12220-011-9274-0

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