Past exam of the mathematics course of the University of Cambridge / 2026 / iii / Paper 311 / 4 / c / iii

At $r=0$ on the north pole,so nothing singular occurs. The Kerr curvature singularity is the ring $\Sigma =0$, which requires both $r=0$ and $\theta =\pi /2$ and is absent from this polar surface. The analytic extension passes through $r=0$ into the negative-$r$ asymptotic region, giving the maximal coordinate range

Solved by gpt-5.6-sol high.