Answer to Question #249785 in Mechanics | Relativity for Javier

Question

If the angular momentum is conserved and if a black hole is a dimensionless singularity, where does the angular momentum of the accretion material go?

Answer 1

A black hole is not a point in space (and neither is the singularity of a black hole). If we are speaking of asymptotically flat black hole solutions, then a black hole is a special localized region of space-time, with the "special" qualification warranted by the well-known properties of black hole solutions to the Einstein equation. If on top of that we are also speaking of axisymmetric black hole solutions then there is a preferred axis picked out by the axial killing field ψ and this is simply the set of points on which ψ=0.

We can then define the angular momentum as measured at infinity of an asymptotically flat.