Black Holes and Information Loss

Discussion in 'Physics & Math' started by RJBeery, Mar 21, 2017.

  1. The God Valued Senior Member

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    Could you not draw a conclusion from your argument that HR is bad ?

    Say, I deduce from your argument that HR is bad and thus BH cannot evaporate, then what?

    By the way pl read page #217 of Wald, it has answer for your #4.
     
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  3. RJBeery Natural Philosopher Valued Senior Member

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    The evaporation mechanism could be something other than Hawking radiation, or event horizons could form in a way other than predicted by general relativity, but the fact that Hawking radiation presumes the existence of a general relativistic event horizon in finite time...yes I believe HR is "bad".

    I'm staring at page 217 of Wald's General Relativity book and I do not see how it pertains. Perhaps you're referring to "Black Holes and Relativistic Stars"?
     
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  5. The God Valued Senior Member

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    My bad, its page #212, Section 9.1 what is a singularity ?
     
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  7. The God Valued Senior Member

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    It is a problematic issue to define the place of singularity and thus an associated event cannot be mapped. I think pt#4 (BH not in past light cone) signifies the problem associated with this. It cannot be used to create a contradiction, the way you are suggesting.
     
  8. RJBeery Natural Philosopher Valued Senior Member

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    Conflating the singularity with the entire black hole is a mistake. #4 refers to any and all parts of the black hole, including the event horizon. Except for the physical singularity, these parts all have a finite interval from the external world which is necessarily space-like, time-like, or light-like. Additionally, none of these parts can exist in the past light cone of an external observer.

    I want pryzk to verify his position because frankly it's difficult for me to believe that he really believes it.
     
  9. The God Valued Senior Member

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    There seems to be some improper application of light cone concept here. Kind of misunderstanding. Inside EH the light cone is unidirectional and time coordinate becomes spatial. You are pushing pt#4, which is a non-issue. Anyway to pryzk..
     
  10. przyk squishy Valued Senior Member

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    Yes, and this is what the Kruskal diagram is showing.
     
  11. RJBeery Natural Philosopher Valued Senior Member

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    There are many problems with relying on that diagram.

    First of all, it's a mish-mash of diagrams, as explained in the paper.

    This is required because the conventional black hole and Hawking radiation are, at best, incomplete and, likely, completely incompatible.

    Secondly, Penrose diagrams are causal. The orange lines are clearly crossing over the 45 degree angle from the vertical that denotes causal possibilities.

    Lastly, you are basing your beliefs on a graph from a paper whose entire premise is to show that there is a problem with the current acceptance of evaporating black holes containing event horizons.

    I have a strong suspicion that if someone were pushing their crank theory which demonstrably required a non-compact topology it would be rejected on that basis alone.
     
  12. przyk squishy Valued Senior Member

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    Not for the point I was originally making. You claimed there was an obvious contradiction with evaporating black holes. But this was based on nothing except assumptions you made in favour of yourself. Like assuming something the LHC safety group said means the evaporating black hole is in the causal past, instead of actually looking up what people think an evaporating black hole is. The diagram, whatever its merits or flaws, does definitively show that what people imagine for an evaporating black hole is not so simplistic as what you were assuming.

    If you really need to be reminded, the thing I really objected to was you saying there was an obvious contradiction with the whole idea of evaporating black holes. As if the idea were so obviously stupid that it should never have been considered in the first place, and how can I not see it? You even said at one point that you thought physicists have been duped.

    But when I press you on this, you are never able to justify yourself, and you invariably change the subject to some milder claim that was never really under dispute or some dispute over definitions that absolutely nobody cares about.

    Most recently, you were trying to claim that the evaporating black hole isn't a black hole by Wald's definition and/or it is incompatible with classical GR in some way. Neither of those, even if they were true, would justify saying anyone has been duped.

    Likewise, the Nuclear Physics B paper says that the evaporating black hole picture is based on an assumption that Hawking radiation can be neglected during the formation of the black hole. It then proceeds to challenge whether it is actually safe to make that approximation. Now, if you need to do a difficult calculation to find out if evaporating black holes form or not, especially a calculation you yourself don't know how to do, then I think you're hardly justified to dismiss the matter as "obvious".
     
  13. RJBeery Natural Philosopher Valued Senior Member

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    Well, obvious is subjective, but a logical contradiction is not. I maintain there is an obvious contradiction with evaporating black holes. The only reason it isn't obvious for some, I suspect, is because scientific dogma has people (such as yourself, apparently) assuming that someone else has the actual answer. Evidence for this is that you claim I would achieve a full understanding if I just took a university course on the subject...despite the fact that you are an intellectual peer and clearly don't have such an understanding after taking those classes.

    I know my definitive tone is offensive, but just because I'm loud doesn't mean I'm wrong.
     
  14. przyk squishy Valued Senior Member

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    You haven't been able to show any logical contradiction with evaporating black holes.


    I don't assume someone else has the answer. My opinion is that whether evaporating black holes form or not is a research question that is best left to people who actually know what they're doing with the theory to sort out. I am not emotionally invested in black holes existing or not existing either way.

    Accusing me of dogmatism is self-defeating, especially when I consistently bend over backwards to admit the limits of my own knowledge while you act like everyone should adopt your opinions about black holes based on nothing but faith.


    You are wrong to be loud. If you claim there is a logical contradiction with evaporating black holes and can't prove it then you are wrong to make that claim, no matter whether they're found to exist or not. It is blatantly transparent that you are doing this. You said there was a contradiction before you even knew what the basic spacetime picture for an evaporating black hole is, for crying out loud.

    Just don't behave like this if you don't want to be called out on it.
     
  15. RJBeery Natural Philosopher Valued Senior Member

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    Good lord, przyk, the only reason you say I haven't established a logical contradiction is because you disagree with #4:

    1) HR requires an event horizon
    2) HR causes BH evaporation
    3) An evaporating BH has a finite life
    4) A BH with a finite life cannot contain an event horizon because it would be capable of existing in our past light cones (which contradicts general relativity)

    Wald's definition wasn't intended to mean that part of the event horizon lives in some mysterious Dimension X -- it means that the event horizon resides in our infinite causal future. The past light cone of future null infinity would include all of the causal present of all frames. Without a compact, infinitely differentiable topology spacetime is meaningless.
     
  16. przyk squishy Valued Senior Member

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    I say you haven't established a logical contradiction because you haven't justified your point #4.

    To avoid possibly being accused of moving the goal posts in the future I should also add this: it would not be enough to merely show a contradiction, any contradiction, with GR. This is because evaporating black holes come from a research area that is explicitly pushing beyond just what pure classical GR alone predicts. You would need to exhibit some contradiction that clearly proves the whole idea of evaporating black holes is fundamentally unworkable.


    No. Wald's definition is exactly what it is: a definition, according to which you can classify some regions of a given spacetime manifold as "black hole" or "event horizon" and others as neither. The definition alone says nothing, logically, about what kinds of manifolds are allowed in GR. You are obviously inserting your own assumptions about that here.

    Wald's definition of black holes isn't even logically a part of GR, so I don't see why you are so dependent on it. The theory of GR would be the same whether you use that definition or not.
     
    Last edited: Apr 10, 2017
  17. RJBeery Natural Philosopher Valued Senior Member

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    Wow, I missed a link posted by Fednis in another thread because, until then, it was filled with nothing interesting to me (so I unsubscribed).
    From the link:
     

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