On 07 Jan 2012, at 22:00, meekerdb wrote:
On 1/7/2012 3:30 AM, Bruno Marchal wrote:
On 07 Jan 2012, at 01:33, Charles Goodwin wrote:
Black hole evaporation. I am thinking about some work by Hawking.
Could you point me towards it? I know Hawking conceded a bet on this
recently but I'm not sure why.
Search on "Hawking Preskill Thorne bet".
Or on "black hole information paradox 1997".
But $any* true erasing of information is forbid in any theory
where QM
applies universally. Unitary evolution cannot erase information,
although it can hide it and makes it very hard to recompose.
True....but I don't suppose anyone is sure that QM necessarily
applies
universally (altho I would bet that it did if I had to!)
In science we are never sure. But QM seems to be a very solid
hypothesis. It is the first "exact" theory which has lived longer
than 15 years, and indeed after about a century it remains
undefeated. By QM I mean the formulation of QM without the wave
collapse (Everett).
I think some cosmological observations confirm this. It makes QM
necessary to justify the existence and stability of Black Hole.
More information, please!!! :-)
Wheeler coined the term "black hole" to make the idea sounding
ridiculous.
Wheeler coined the term, but not to make it sound ridiculous, rather
to popularize the concept. I understand it had a rather different
reference in French than in English. Perhaps you're thinking of
"Big Bang" which was coined by Tommy Gold to mock the concept.
Gosh you might be right. Sorry.
Indeed Black Hole does not make much sense in classical general
relativity. It would force nature into dividing number by zero. But
quantum mechanics came to rescue them, and today it is generally
admitted that black holes indeed exist, in many forms.
A problem with QM arised: is information falling in a black hole
irreversibly destroyed ? If that is the case, then both classical
and quantum physics are incorrect, if not, it means black hole can
restitute in principle every bit of information which felt in it.
Apparently Hawking bet that the information might be destroyed,
and ... lost the bet.
More accurately, Hawking conceded the bet and now believes that
black holes do not destroy information, but there is no solid
evidence or theory to show that. It's just that Stephen changed his
opinion.
I share with Preskill the idea that the core fundamental (but not
primitive) physics is QM (without collapse). If the physical universe
is described by a unitary evolution then even a black hole can't
destroy one bit of information. So I do think there is a theory (QM),
even if I think this is an open problem in comp (but the material
hypostases already gives some hint for unitary and other symmetries).
And any evidence that QM applies in the cosmos is evidence that black
hole evolution have to be unitary, or partial trace of unitary
evolution. But I doubt QM makes it possible for information to leak
from one universe to a 'parallel one'. I dunno, I should think about
black hole entanglements, but globally QM evolution is information
preserving. OK?
Bruno
http://iridia.ulb.ac.be/~marchal/
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