Stephen Hawking offers new resolution of black hole paradox

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  • #26
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Hawking has been dismissed most of his career upon the first presentations of a new idea. Historically it has usually been a great mistake to do this, b/c more often than not he has been deeply in advance of his detractors and the ideas usually have much more oomph to them than it might naively seem.

His situation is such that it is very difficult for him to actually flush out an idea, or to have quantitative arguments about nitty gritty details. Instead he is blessed with very acute mental pictures of what takes place, and it's difficult for him to explain how this works in great detail. This unfortunate aspect gives his presentations a bit of an oracle quality and hence much of the crazy press.

This is usually a matter of great frustration within the community, especially since his ideas here (and those back in the mid2ks) are not necessarily new to people. The asymptotic symmetry group aspect of GR has been a very fruitful avenue of research since the early 80s and was a precursor foundation to Brown-Henneaux's work and ultimately to AdS/CFT. Many people have been following Stromingers work on this subject for the last few years. Likewise the business about decoding the hologram is one of the very central textbook aspects of the information paradox, and is well studied.

So of course we would like to know the details..
 
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Ben Niehoff
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Indeed, everything he says has a tendency to require quite a bit of unpacking. It will be interesting to see the finished paper. I don't think that Malcolm or Andy intend to make any claims that are not supported by calculations.
 
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Infinite symmetries, that is infinite charges conserved. I wonder if they can be use to regularize perturbatively GR.
 
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It seems to me that Hawkings has pointed out something that should have been pretty obvious: if, from an outside observer’s viewpoint, infalling material appears to stop at the event horizon, then from the standpoint of everything outside the black hole, the material is stuck on the event horizon, so its ‘information’ is not lost, and the event horizon is not black at all, but a (colorful?) record of everything that has hit it. My question is: what happens as the event horizon expands?
 
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The expansion created more horizon surface to store the extra information I would guess...
 
  • #31
marcus
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... ‘information’ is not lost, and the event horizon is not black at all, but a (colorful?) record of everything that has hit it. My question is: what happens as the event horizon expands?
The expansion created more horizon surface to store the extra information I would guess...
According to the usual story, the event horizon shrinks as the BH evaporates. And eventually the horizon disappears in a final burst of H. radiation.
So it does seem that you need to refine your question: what happens as the event horizon contracts?
The information must somehow get off the event horizon and save itself by taking flight (either in the H. radiation, or encoded as variations in the gravitational field, or?)

That is, at least if it is meaningful for unitarity to be treated as an absolute requirement for all time.
 
  • #32
Chronos
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I think Hawking is ill and hoping to make a splash while he is still able to communicate.
 
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Ben Niehoff
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I think Hawking is ill and hoping to make a splash while he is still able to communicate.
What a terrible thing to say.
 
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marcus
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PM thanks for the link to those salient quotes from Strominger! They are worth excerpting:
==quote LA Times==
Contacted via telephone on Tuesday evening, Strominger said he felt confident that the information loss paradox was not irreconcilable. But he didn't think everything was settled just yet.

He had heard Hawking say there'd be a paper by the end of September. It had been the first he'd learned of it, he laughed, though he said the group did have a draft.

Whatever the team publishes, Strominger added, it's unlikely to be the final word.
==endquote==

The quote from Polchinski was also sobering:
==quote LA Times==
UC Santa Barbara physicist Joseph Polchinski, who has thought about the problem a great deal in the past, said that he, too would need to see Hawking's calculations to understand if the solution made sense.

"I don't think what Hawking and his collaborators are proposing is radical enough to solve the problem," he said. "But I haven't seen the publication, so I'm just speculating."
=endquote==

I thought the LA Times reporter did a good bit of journalism. It was smart to contact John Preskill at Caltech, and to talk with Strominger directly.
Here are a few more remarks from Strominger:
==quote LA Times==
"There's still much more work to be done to show that when something falls into a black hole that it leaves a record of exactly what it was. That is the part we still need to work out," he said. "Stephen is very optimistic that it's all going to work perfectly. But physics is a hard mistress. You have to get all the calculations to work perfectly and everything has to line up."

"Stephen is a smart guy," Strominger continued. "Maybe he's seeing all the way to the end. I'm certainly not."
==endquote==
http://www.latimes.com/science/scie...-hole-information-paradox-20150826-story.html
 
  • #36
Garth
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Would information be preserved through a 'Big Crunch' of a cyclical universe?

If so the entropy problem reappears.

Garth
 
  • #38
marcus
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The conference participants have all sat down together to do a Reddit AMA. Might be entertaining to read:

https://www.reddit.com/r/IAmA/comments/3iuf6c/we_are_the_international_group_of_theoretical/
Great! Thanks for posting the link!
Here's a brief sample of discussion
https://www.reddit.com/r/IAmA/comments/3iuf6c/we_are_the_international_group_of_theoretical/cujq1qu
Francesca was active in Physicsforums for several years, and still occasionally drops in. She gave a talk at the the Stockholm conference and also participated in the Reddit later.
https://www.reddit.com/r/IAmA/comments/3iuf6c/we_are_the_international_group_of_theoretical/cujq8hr
Here's a very brief thread where both Carlo Rovelli and Malcolm Perry replied to a question about "super translations"
https://www.reddit.com/r/IAmA/comments/3iuf6c/we_are_the_international_group_of_theoretical/cujporr

==sample quote from Carlo and Malcolm==
CarloRovelli 12 points 2 days ago

Here is a zero-level version of what a "super translation" means. Take a big sphere and imagine many clocks on it, say all beating at the same time. Now make one of the cocks miss a bit. So now that particular clock is a bit later than all the others. Well, this change is (an elementary version of) a "super translation". It is a "translation" because it is like "translating in time". But it is a "super" translation because it does not translate all the clocks (like normal time translation would), but only some of them. Now it turns out out, or at least so suggest Malcolm and Stephen, that the "super translations" might code the information about how things fall in a black hole.... but Malcolm can certainly explain this part better...

MalcolmJPerryPHYSICIST 14 points 2 days ago

The original idea of a super translation relates to how to detect gravitational radiation. Imagine a collection of satellites orbiting the earth. As you look into the sky, these satellites will formake a fixed pattern. Now suppose that a burst of gravitational radiation passes through the system. The pattern the satellites makes will change. The mathematical description for this change is called a super translation. What is new is the discovery that can extend the idea of a super translation to the horizon of a black hole. Then the super translation will give information about what has fallen into a black hole. In this way, one can determine what goes to make up the black hole and hence resolve (or perhaps help to resolve) the black hole information paradox


load more comments (4 replies)...
==endquote==
 
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  • #39
marcus
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Would information be preserved through a 'Big Crunch' of a cyclical universe?

If so the entropy problem reappears.

Garth
I'm not sure that bounce cosmologies have an entropy problem, Garth, because entropy is observer-dependent. The observer's coarse grain map of what matters--what makes a difference and what doesn't. We depend on the fact that according to our coarse-graining map the entropy was very low at the bounce, or start of expansion.

But in a bounce cosmology, at the bounce itself there are no observers, so entropy is simply not definable. The observers are partitioned into two groups, those before and those after.

I don't speculate about "cyclic". That is a further topic of conversation. Just a simple one-bounce model cosmology as in the paper by Ed Wilson-Ewing and Yi-Fu Cai
 
  • #40
Ben Niehoff
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Here is Malcolm's talk, and I suspect Nordita has put up everyone else's talk as well:

 
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marcus
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Ben, I suspect Nordita will post the other talks as you suggest. At http://www.nordita.org/video/index.php
they have batches of talks from other events like this conference, and they have added an icon for this conference on that page.
So far when you click on it you get a menu with only 1 talk, Malcolm Perry's:
http://www.nordita.org/video/index.php?ev=hrad2015

But it is clearly set up to have videos of the other talks from the event added to the menu. We can check the menu later in the week and see what they have added to it.
 
  • #42
Ben Niehoff
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By the way, I'm impressed at the production value of Nordita's talk videos (at least Malcolm's above). Three different camera angles! I don't think most conferences do this. I only remember seeing one camera in the room at any conference I've attended.
 
  • #43
marcus
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Hawking now has a 3 page paper on arxiv covering his talk and giving references
http://arxiv.org/abs/1509.01147
The Information Paradox for Black Holes
S. W. Hawking
(Submitted on 3 Sep 2015)
I propose that the information loss paradox can be resolved by considering the supertranslation of the horizon caused by the ingoing particles. Information can be recovered in principle, but it is lost for all practical purposes.
3 pages. Talk given on 28 August 2015 at Hawking Radiation, a conference held at KTH Royal Institute of Technology, Stockholm

It's quite brief, the abstract (which you see here) plus 1 and 1/2 page of text, plus half a page of references.
I think basically just a verbatim transcript of the talk, which we have recorded on video. But it's nice to see specific references.
 
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Inside a black hole there is gravity, matter and energy. The event horizon of a black hole is the limit between the black hole and the space. When the matter reaches the event horizon it turns into energy. E=mc2.
 
  • #45
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Hawking now has a 3 page paper on arxiv covering his talk and giving references
http://arxiv.org/abs/1509.01147
The Information Paradox for Black Holes
S. W. Hawking
(Submitted on 3 Sep 2015)
I propose that the information loss paradox can be resolved by considering the supertranslation of the horizon caused by the ingoing particles. Information can be recovered in principle, but it is lost for all practical purposes.
3 pages. Talk given on 28 August 2015 at Hawking Radiation, a conference held at KTH Royal Institute of Technology, Stockholm

It's quite brief, the abstract (which you see here) plus 1 and 1/2 page of text, plus half a page of references.
I think basically just a verbatim transcript of the talk, which we have recorded on video. But it's nice to see specific references.l
I read that paper, but I don't understand the premise. Hawking's approach is to analyze what happens when a particle falls in through the EH. But that does not address the information paradox with respect to mass trapped inside the BH as the star collapsed and which, therefore, never did pass through the EH.

My understanding of information conservation is that it is strict. Unless the paradox is resolved for every last particle, it remains a paradox.
Is that correct?
 

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