Black holes may not exist after all

[JesseM]

I meant a closed, finite, universe; one where future null conformal infinity is undefined.

Even in a closed universe, is it meaningful to distinguish between worldlines that terminate in a black hole singularity and worldlines that terminate in the Big Crunch singularity? If so, then even if the standard definition of "event horizon" in terms of escaping to infinity wouldn't apply, perhaps one could still define a different sort of horizon marking the boundary between points in spacetime where all lightlike worldlines through that point end in the black hole singularity, and points where at least some lightlike worldlines terminate in the Big Crunch singularity. But maybe a distinct black hole singularity doesn't exist in this case, I don't know.

 

[PAllen]

Even in a closed universe, is it meaningful to distinguish between worldlines that terminate in a black hole singularity and worldlines that terminate in the Big Crunch singularity? If so, then even if the standard definition of "event horizon" in terms of escaping to infinity wouldn't apply, perhaps one could still define a different sort of horizon marking the boundary between points in spacetime where all lightlike worldlines through that point end in the black hole singularity, and points where at least some lightlike worldlines terminate in the Big Crunch singularity. But maybe a distinct black hole singularity doesn't exist in this case, I don't know.

But then some events inside the apparent horizon (near the big crunch) would be considered outside the true horizon. An 'outgoing' null ray from them might be caught be the big crunch without reaching what was the BH singularity.

I think, for a universe without the appropriate infinity it makes more sense to define an 'effective BH' in terms of the local trapping surface plus classically predicted singularity.

 

[Vanadium 50]

This is drifting into the realm of personal theories.