 Null Raychaudhuri equation

ID: null-raychaudhuri-equation

Codex  0 Created 2026-09-24 Updated 2026-09-24

For an affinely parametrized null congruence in four spacetime dimensions,

\frac{d θ}{d λ} = - \frac{1}{2} θ^{2} - σ_{ab} σ^{ab} + ω_{ab} ω^{ab} - R_{ab} k^{a} k^{b} .

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