Paper 3, Section II, F

Algebraic Geometry
Part II, 2019

Let WA2W \subseteq \mathbb{A}^{2} be the curve defined by the equation y3=x4+1y^{3}=x^{4}+1 over the complex numbers C\mathbb{C}, and let XP2X \subseteq \mathbb{P}^{2} be its closure.

(a) Show XX is smooth.

(b) Determine the ramification points of the mapXP1\operatorname{map} X \rightarrow \mathbb{P}^{1} defined by

(x:y:z)(x:z).(x: y: z) \mapsto(x: z) .

Using this, determine the Euler characteristic and genus of XX, stating clearly any theorems that you are using.

(c) Let ω=dxy2KX\omega=\frac{d x}{y^{2}} \in \mathcal{K}_{X}. Compute νp(ω)\nu_{p}(\omega) for all pXp \in X, and determine a basis for L(KX)\mathcal{L}\left(\mathcal{K}_{X}\right)