 Kerr axial analytic extension

The two-dimensional symmetry-axis restriction of the Kerr metric has simple horizons at $r_{\pm }$ for $0<|a|<M$, but is regular at $r=0$ because the ring is off-axis. Its static region below the inner horizon continues to an asymptotically flat end at negative infinity. The horizon blocks repeat in the maximal analytic extension. This ideal continuation is distinct from a claim of physical stability at the Cauchy horizon.