Re: Implications of Hawking's recent work for black hole jumping astronauts
- From: tessel@xxxxxx
- Date: Sat, 16 Sep 2006 20:03:58 +0000 (UTC)
On Thu, 14 Sep 2006, Gerry Quinn wrote:
Two years ago, in Dublin, Stephen Hawking announced that he had solved
the black hole information problem. In essence, he treated a black
hole as a particle scattering experiment, as viewed from a long
distance away. Particles go in, some sort of stuff goes on, particles
eventually come out, instruments detect them.
First, I stronly suggest that you PUT THIS ASIDE until you have studied
by other post and done the computational exercises. You can't
reasonably try to understand QFT near a black hole event horizon if you
haven't mastered the classical field theory (gtr) in terms of which
"black hole", "even horizon", "future null infinity", and so on, are
defined. (To mention just three concepts from classical gtr you will
need to understand the scattering picture.)
I will try to avoid speculation completely, and just describe my
understanding of the situation.
AFTER learning gtr:
I strongly urge you to read the book edited by Wald, Black Holes and
Relavistic Stars, for discussions of "evaporating black holes", "black
hole interior region", "information paradox", etc. This is somewhat out
of date but you will find it extremely useful for background.
Next, I urge you to obtain and read the relevant sections of Frolov &
Novikov, Black Hole Physics, for a fine introduction to the scattering
formalism for black holes.
So after the experiment is done and the measurements analysed, the
question of "what happens to an astronaut jumping into a large black
hole" will (if Hawking is right) have an experimentally verified answer.
Furthermore, if Hawking is right, this answer will be: he never reaches
the event horizon.
I think you have misunderstood. Since you are hopefully reading this
months in the future, after you have learned gtr, you probably can see
this yourself. But you do raise a question which you might repost:
In other words, physicists (if they do this experiment and Hawking is
found to be correct) will have demonstrated that general relativity
breaks down somewhere outside the event horizon of a black hole.
Gtr must break down -outside- the event horizon? I don't think Hawking
claimed any such thing! However, I'd rather see John Baez or Ned Bunn
or Steve Carlip or Ted Jacobson respond to this point, since at least
one of them was present for the talk in question, IIRC.
Is there a flaw in this analysis, or is it something generally agreed?
Well, last I checked, very little seemed to be "generally agreed" about
the black hole information paradox, but again, I'd prefer a response by
Baez, Bunn, Carlip, or Jacobson.
But I can tell you this: as Ned Bunn and I independently already
mentioned, it -is- generally agreed that gtr should give excellent
results near the event horizon (inside or outside!) of any astrophysical
black hole.
From what I hear, Hawking's latest remarks were a bit cryptic, but AFAIKhe has not claimed that this general agreement is mistaken. If you
think otherwise, can you provide a citation? Preferably to an arXiv
eprint rather than to an audio file or to some enthusiast's blog?
"T. Essel"
.
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