Paper 4, Section II, F

Algebraic Geometry
Part II, 2020

Let P0,,PnP_{0}, \ldots, P_{n} be a basis for the homogeneous polynomials of degree nn in variables Z0Z_{0} and Z1Z_{1}. Then the image of the mapP1Pn\operatorname{map} \mathbb{P}^{1} \rightarrow \mathbb{P}^{n} given by

[Z0,Z1][P0(Z0,Z1),,Pn(Z0,Z1)]\left[Z_{0}, Z_{1}\right] \mapsto\left[P_{0}\left(Z_{0}, Z_{1}\right), \ldots, P_{n}\left(Z_{0}, Z_{1}\right)\right]

is called a rational normal curve.

Let p1,,pn+3p_{1}, \ldots, p_{n+3} be a collection of points in general linear position in Pn\mathbb{P}^{n}. Prove that there exists a unique rational normal curve in Pn\mathbb{P}^{n} passing through these points.

Choose a basis of homogeneous polynomials of degree 3 as above, and give generators for the homogeneous ideal of the corresponding rational normal curve.