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

A black-hole metric is stationary when it admits a Killing field $K$ generating time translations and timelike near spatial infinity. It is static when $K$ is also hypersurface orthogonal,In coordinates adapted to a static field, the metric coefficients are time independent and the time-space cross terms vanish.

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