Paper 2, Section II, F

Riemann Surfaces
Part II, 2017

Let ff be a non-constant elliptic function with respect to a lattice ΛC\Lambda \subset \mathbb{C}. Let PP be a fundamental parallelogram whose boundary contains no zeros or poles of ff. Show that the number of zeros of ff in PP is the same as the number of poles of ff in PP, both counted with multiplicities.

Suppose additionally that ff is even. Show that there exists a rational function Q(z)Q(z) such that f=Q()f=Q(\wp), where \wp is the Weierstrass \wp-function.

Suppose ff is a non-constant elliptic function with respect to a lattice ΛC\Lambda \subset \mathbb{C}, and FF is a meromorphic antiderivative of ff, so that F=fF^{\prime}=f. Is it necessarily true that FF is an elliptic function? Justify your answer.

[You may use standard properties of the Weierstrass \wp-function throughout.]