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.

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.

Brent

I think you will find many informations on this by searching on terms like black hole, Hawking, Preskill. I am not an expert in cosmology (nor physics), so I have only layman ideas on this. I do have "theological-arithmetical" reason that the core of physics is highly symmetrical, though, and I do expect that the time symmetry of nature is something very basic. I explain why in the paper:

Marchal B., 2005, Theoretical computer science and the natural sciences, Physics of Life Reviews, Vol. 2 Issue 4 December 2005, pp. 251-289.
http://www.sciencedirect.com/science/article/pii/S1571064505000242

Bruno



http://iridia.ulb.ac.be/~marchal/




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