1.II.23H

Riemann Surfaces
Part II, 2008

Define the terms Riemann surface, holomorphic map between Riemann surfaces and biholomorphic map.

Show, without using the notion of degree, that a non-constant holomorphic map between compact connected Riemann surfaces must be surjective.

Let ϕ\phi be a biholomorphic map of the punctured unit disc Δ={0<z<1}C\Delta^{*}=\{0<|z|<1\} \subset \mathbb{C} onto itself. Show that ϕ\phi extends to a biholomorphic map of the open unit disc Δ\Delta to itself such that ϕ(0)=0\phi(0)=0.

Suppose that f:RSf: R \rightarrow S is a continuous holomorphic map between Riemann surfaces and ff is holomorphic on R\{p}R \backslash\{p\}, where pp is a point in RR. Show that ff is then holomorphic on all of RR.

[The Open Mapping Theorem may be used without proof if clearly stated.]