Paper 2, Section II, G

Riemann Surfaces
Part II, 2010

Given a complete analytic function F\mathcal{F} on a domain UCU \subset \mathbb{C}, describe briefly how the space of germs construction yields a Riemann surface RR associated to F\mathcal{F} together with a covering map π:RU\pi: R \rightarrow U (proofs not required).

In the case when π\pi is regular, explain briefly how, given a point PUP \in U, any closed curve in UU with initial and final points PP yields a permutation of the set π1(P)\pi^{-1}(P).

Now consider the Riemann surface RR associated with the complete analytic function

(z21)1/2+(z24)1/2\left(z^{2}-1\right)^{1 / 2}+\left(z^{2}-4\right)^{1 / 2}

on U=C\{±1,±2}U=\mathbb{C} \backslash\{\pm 1, \pm 2\}, with regular covering map π:RU\pi: R \rightarrow U. Which subgroup of the full symmetric group of π1(P)\pi^{-1}(P) is obtained in this way from all such closed curves (with initial and final points P)P) ?