Ramification of the derivative of the Weierstrass elliptic function

ID: ramification-of-the-derivative-of-the-weierstrass-elliptic-function

On its period torus, the derivative has one triple pole, so degree three. The Riemann-Hurwitz formula gives total ramification six, counting each ramification point with weight . The number of distinct ramification points is five when and three when . Indeed by the Weierstrass elliptic differential equation. If , each of its two possible -values has two distinct unramified preimages for , because coincidence with a cubic branch root would force a repeated root. These four simple zeros of give local degree two for , and its triple pole contributes local degree three. If , nonsingularity forces ; the two simple zeros of are double zeros of and each gives local degree three for . Along with its pole these are three distinct points, each of weight two. A hexagonal period lattice realizes this second case by its sixth-root rotational symmetry.

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