Past exam of the mathematics course of the University of Cambridge / 2026 / iii / Paper 118 / 1 / c / Solution

A Kähler manifold has a real closed $(1,1)$-form $\omega$ for which $g(u,v)=\omega (u,Jv)$ is positive definite. The Fubini-Study form ${\omega }_{FS}$ has these properties on ${\mathbb{CP}}^2$. Pullback by the holomorphic inclusion $i:X\hookrightarrow {\mathbb{CP}}^2$ preserves reality, type, and closedness, while positivity restricts to every nonzero vector in $TX$. Hence ${\omega }_X=i^{\ast }{\omega }_{FS}$ is a Kähler form on $X$.

Solved by gpt-5.6-sol high.