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Black Holes and Strings

  1. Oct 20, 2005 #1
    Does string theory touted as TOE offer a possible explanation of what happens beyond the event horizon?

    If not what may?
  2. jcsd
  3. Oct 20, 2005 #2


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    Standard GR is probably good enough to describe what happens beyond the event horizon of a black hole if one is not too close to the central singularity. The solution for non-rotating black holes is believe to be a particular sort of singularity, called a BKL singularity.

    Unfortunately, the predictions of GR cannot be tested in this realm except by a person willing to jump into a black hole. At that point, the person or probe that jumps into the black hole will have the answers, but they won't have any way of communicating them to the rest of us. (Unless we decide to follow the probe and jump into the black hole ourselves).

    Quantum gravity is probably needed when one is very close to the singularity. (this is where string theory or some other TOE / theory of quantum gravity would be needed).

    Non-rotating black holes are probably reasonably well understood by GR, but there are still some unanswered questions about the internal structure of rotating black holes. These questions are separate from the quantum gravity questions that arise when one is close to the central singularity. They arise in regions where GR is still expected to be valid, however the computations of exactly what happens inside a rotating black hole involve complex cacluations that are still a subject of some debate.

    For more reading, I would recommend

    Thorne, K. S. Black Holes and Time Warps: Einstein's Outrageous Legacy. New York: W. W. Norton, 1994.
  4. Nov 1, 2005 #3
    beyond the horizon

    I would like to add the ref


    'Quantum geometry and the Schwarzschild singularity'
    Abhay Ashtekar, Martin Bojowald

    which is a very useful discussion about the singularity inside the horizon and the evolution of the spactime. It seems to me that even though the inside of the black hole is hidden by the horizon, the evaporation should eventually reveal what is going on inside - if we understand its process fully. It seems plausible to me that string theory should at least describe part of this - even if it is not the TOE.
  5. Nov 2, 2005 #4


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    I agree that this is a key paper. It seems to "make it official" that the classical BH singularity can be replaced with a quantum gravity model of what goes on at the pit of a black hole. And the process of constructing the new picture is far from over.

    It seems like a huge gap in people's understanding----there is something down there which can be analysed, it is not just a glitch where the classical theory blows up and about which nothing can be said. If string theory or any other theory develops into a successful non-perturbative quantum theory of gravity then I agree with hossi that whether or not it is a TOE it should be able to describe conditions down there where the classical singularity used to be. Exciting challenge for today's QG physicists.
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