 Ingoing BTZ coordinates

ID: ingoing-btz-coordinates

Codex  0 Created 2026-09-28 Updated 2026-10-14

For

d s^{2} = - fd t^{2} + \frac{d r ^{2}}{f} + r^{2} (d ϕ - Ω d t)^{2},

the transformations

d v = d t + d r / f

and

d χ = d ϕ + Ω d r / f

give

d s^{2} = - f d v^{2} + 2 d v d r + r^{2} (d χ - Ω d v)^{2},

which is regular at every horizon where

f

vanishes while

Ω

remains finite.

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