Paper 3, Section II, H

Algebraic Geometry
Part II, 2014

Let fk[x]f \in k[x] be a polynomial with distinct roots, degf=d>2\operatorname{deg} f=d>2, char k=0k=0, and let CP2C \subseteq \mathbf{P}^{2} be the projective closure of the affine curve

yd1=f(x)y^{d-1}=f(x)

Show that CC is smooth, with a single point at \infty.

Pick an appropriate ωΩk(C)/k1\omega \in \Omega_{k(C) / k}^{1} and compute the valuation vq(ω)v_{q}(\omega) for all qCq \in C.

Hence determine degKC\operatorname{deg} \mathcal{K}_{C}.