Solution

ID: past-exam-of-the-geometry-of-surfaces-course-of-the-university-of-oxford/2023/2/c/solution

In a cyclic group of prime order , a stabilizer subgroup has order either one or . The latter case consists exactly of points fixed by all of . Thus the fixed points each have ramification index of a holomorphic map , and every other point has index one. Applying the Riemann-Hurwitz formula with degree of a holomorphic map gives
Equivalently,
The count concerns fixed points upstairs. Each is its own group orbit, so their images are also distinct branch values of a holomorphic map.

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