Paper 3, Section II, G

Riemann Surfaces | Part II, 2011

State the Classical Monodromy Theorem for analytic continuations in subdomains of the plane.

Let n,rn, r be positive integers with r>1r>1 and set h(z)=zn−1h(z)=z^{n}-1. By removing nn semi-infinite rays from C\mathbb{C}, find a subdomain U⊂CU \subset \mathbb{C} on which an analytic function h1/rh^{1 / r} may be defined, justifying this assertion. Describe briefly a gluing procedure which will produce the Riemann surface RR for the complete analytic function h1/rh^{1 / r}.

Let ZZ denote the set of nnth roots of unity and assume that the natural analytic covering map π:R→C\Z\pi: R \rightarrow \mathbb{C} \backslash Z extends to an analytic map of Riemann surfaces π~:R~→C∞\tilde{\pi}: \tilde{R} \rightarrow \mathbb{C}_{\infty}, where R~\tilde{R} is a compactification of RR and C∞\mathbb{C}_{\infty} denotes the extended complex plane. Show that π~\tilde{\pi} has precisely nn branch points if and only if rr divides nn.

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