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New Bekenstein paper on BH and Information

  1. Nov 13, 2003 #1


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    "Black Holes and Information Theory"

    popularly written, at least for part of it,
    with rather nice pictures and some historical
    summary of the field as well as some new thoughts

    by Bekenstein himself who came up with BH temperature
    and entropy around 1972 and 1973 and started Hawking
    thinking (Hawking was trying to disprove a bekenstein
    notion, I believe, and instead of disproving he
    discovered the radiation mechnanism)

    anyway bekenstein is an old head about BH and its
    worth checking out his new paper
  2. jcsd
  3. Nov 13, 2003 #2


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    i absolutly refuse to read any more about BHs until
    hawking radiation is observed or disproved :smile:
  4. Nov 13, 2003 #3
    I think Bekenstein, even when discussing the Generalized Second Law (GSL), fails to mention recent developments which are, I think, interesting. For instance, there is an interesting discussion about the GSL in the paper:
    by Marolf and Sorkin.
  5. Nov 13, 2003 #4


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    "On the status of highly entropic objects"
    The date on the arXiv file is November 2003
    Bekenstein may not have been aware of the Marolf/Sorkin article
    Personally I could not tell how much of M/S was tongue-in-cheek
    apart from the obviously tongue-in-cheek bit at the end about
    the man giving a seminar-talk and waving his hands and thereby
    producing an Unruh acceleration temperature---by the acceleration of his hands---and thereby something like Hawking radiation, namely Unruh radiations, containing highly entropic objects. either funny parody or far out speculation, IMO.

    Non-unitary please tell what you got out of the article that was interesting. I havent had time to try to adequately understand it.
  6. Nov 13, 2003 #5


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    I haven't read it either Marcus, but it's a famous paper. It is supposed to have a proposed counter to the information parasox.
  7. Nov 15, 2003 #6

    Let me try to give a little summary of what I see with the GSL. In few words it postulates that the entropy of a black hole plus the entropy of everything else never decreases.

    Ok, so now there are basically 2 different viewpoints regarding its validity. The school of Bekenstein says that some entropy bound on the matter should be satisfied for the GSL to be valid. The school of Wald and Unruh say that the GSL is valid anyhow and does not any any entropy bound.

    They have had a debate over the years defending their viewpoints. The basic gadanken experiment that has been used is the so-called Geroch process. What it assumes is that one has a box with some stuff that gets lowered almost to the surface of the black hole and then the stuff is released into the black hole. The problem I see with the Bekenstein vs. Wald debate is that they each pay attention to different parts of the process, so they never really discuss the same issue. One of them pays a lot o attention to the lowering of the box and not so much to the "release" of the stuff. The other pays extra attention to the release process.

    What is new about the Marolf-Sorkin paper is that they argue that a new element in the debate should be considered, namely the fact that the stuff that is going to fall into the black hole might cause so much quantum disturbance in the vecinity that a lot of Hawking radiation is produced, such that the entropy produced outside the horizon is more that the entropy of the stuff that fell. They argue that this might be happening even when the stuff violates the Bekenstein bounds, so the GSL is saved and one does not need to impose any bound.

    I hope this helps.
  8. Nov 15, 2003 #7


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    that helps some. Now what are HEO (highly entropic objects)
    and how do they fit into the story as you just told it?

    the whole business here is interesting and could do with
    more discussion.


  9. Nov 17, 2003 #8

    By HEO what they mean is any kind of stuff (mater, particles, whatever) that contains a lot of entropy. So much that it might violate some of the entropy bounds.

    Marolf and Sorkin even make a stronger case. They say that there is not even an issue about the valdity of the GSL, since Sorkin has proved in very general situations (basically whenever QFT is valid) in:
    R.D. Sorkin "The statistical mechanics of Black Hole thermodynamics"

    Then their papers are only (according to them) a matter of figuring out how is it that the arguments of Bekenstein fail when arguing that the GSL is violated unless the entropy bounds are satisfied.
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