Paper 2, Section II, F

Riemann Surfaces
Part II, 2018

State the uniformisation theorem. List without proof the Riemann surfaces which are uniformised by C\mathbb{C}_{\infty} and those uniformised by C\mathbb{C}.

Let UU be a domain in C\mathbb{C} whose complement consists of more than one point. Deduce that UU is uniformised by the open unit disk.

Let RR be a compact Riemann surface of genus gg and P1,,PnP_{1}, \ldots, P_{n} be distinct points of RR. Show that R\{P1,,Pn}R \backslash\left\{P_{1}, \ldots, P_{n}\right\} is uniformised by the open unit disk if and only if 2g2+n>02 g-2+n>0, and by C\mathbb{C} if and only if 2g2+n=02 g-2+n=0 or 1-1.

Let Λ\Lambda be a lattice and X=C/ΛX=\mathbb{C} / \Lambda a complex torus. Show that an analytic map f:CXf: \mathbb{C} \rightarrow X is either surjective or constant.

Give with proof an example of a pair of Riemann surfaces which are homeomorphic but not conformally equivalent.