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Soft Hair on Black Holes

  1. Jan 6, 2016 #1
    Soft Hair on Black Holes
    Stephen W. Hawking, Malcolm J. Perry, Andrew Strominger
    (Submitted on 5 Jan 2016)
    It has recently been shown that BMS supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian spacetimes. These laws require black holes to carry a large amount of soft (i.e. zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This paper gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.
    Comments: 22 pages 2 figures
    Subjects: High Energy Physics - Theory (hep-th)
    Cite as: arXiv:1601.00921 [hep-th]
    (or arXiv:1601.00921v1 [hep-th] for this version
     
  2. jcsd
  3. Jan 6, 2016 #2

    MTd2

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    It's the paper promised by Stephan Hawking last August. Perhaps Marcus would like to see it.
     
  4. Jan 6, 2016 #3
    It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.
    sounds like LQG BH entropy
     
  5. Jan 8, 2016 #4

    marcus

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    Dearly Missed

    Bee Hossenfelder was at the August conference and has a reaction to the HPS paper at her blog.
    http://backreaction.blogspot.com/2016/01/more-information-emerges-about-new.html
    At the end she says:
    "In summary, I am not at all convinced that the new idea proposed by Hawking, Perry, and Strominger solves the information loss problem. But it seems an interesting avenue that is worth further exploration. And I am sure we will see further exploration..."
     
    Last edited: Jan 8, 2016
  6. Jan 11, 2016 #5

    Ben Niehoff

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    To be fair, Perry isn't convinced of that, either. I don't know the others' opinions, but I think the paper is fairly conservatively-stated. Indeed, the conclusions end with

    A complete description of the holographic plate and resolution of the information paradox remains an open challenge, which we have new concrete tools to address.

    Malcolm will be giving some talks here in a few weeks to explain the paper to those of us who have not worked with the BMS group before. I'm looking forward to it.

    Edit: Andy is here and is apparently giving a talk on Monday, so we'll be hearing loads about this paper. :P
     
    Last edited: Jan 14, 2016
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