Paper 3, Section II, F

Riemann Surfaces
Part II, 2020

Let Λ=λ,μC\Lambda=\langle\lambda, \mu\rangle \subseteq \mathbb{C} be a lattice. Give the definition of the associated Weierstrass \wp-function as an infinite sum, and prove that it converges. [You may use without proof the fact that

wΛ\{0}1wt\sum_{w \in \Lambda \backslash\{0\}} \frac{1}{|w|^{t}}

converges if and only if t>2t>2.]

Consider the half-lattice points

z1=λ/2,z2=μ/2,z3=(λ+μ)/2,z_{1}=\lambda / 2, \quad z_{2}=\mu / 2, \quad z_{3}=(\lambda+\mu) / 2,

and let ei=(zi)e_{i}=\wp\left(z_{i}\right). Using basic properties of \wp, explain why the values e1,e2,e3e_{1}, e_{2}, e_{3} are distinct

Give an example of a lattice Λ\Lambda and a conformal equivalence θ:C/ΛC/Λ\theta: \mathbb{C} / \Lambda \rightarrow \mathbb{C} / \Lambda such that θ\theta acts transitively on the images of the half-lattice points z1,z2,z3z_{1}, z_{2}, z_{3}.