Black Holes and Information Loss

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

  1. RJBeery Natural Philosopher Valued Senior Member

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    Agreed, but when we consider GR in the context of "observers" and "declarers of existence" and "existing objects" then coordinates do matter. Existence has a necessary temporal element implicit in its definition, and we cannot say that black holes exist in any physical way simply because they exist within the mathematics of general relativity.
     
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  3. Schmelzer Valued Senior Member

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    There is nothing one can do about this. "Exists" in common sense means "exists now", but there is no definition what is "now" in the GR spacetime. So, in a strong sense it makes no sense to say something "exists" if it does not exist for a sufficiently long time so that it can send and receive messages from us now. That means, "exists" is also only sloppy speaking.

    All one can say about the existence of BHs is that there may be some observer, who was nearby a million years ago, and send us a good bye message that in a few seconds he will be inside the BH. If classical GR is true, which is quite improbable in this region.
     
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  5. RJBeery Natural Philosopher Valued Senior Member

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    Did you read the paper in the OP? I deal with this. While we cannot say what "exists now" we certainly can say what does not. GR allows for ambiguous but not arbitrary definitions of "now".
     
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  7. Schmelzer Valued Senior Member

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    Sometimes we can, sometimes not. We cannot say if something exists now if there are two time-like coordinates so that in one coordinate it does not exist now, and in the other it does.

    GR BHs are of this type. You can have coordinates where they never exist, and others where they exist in short time of the external observer after the collapse has started. You would need a criterion which coordinates define true time, GR does not give anything of this type.
     
  8. RJBeery Natural Philosopher Valued Senior Member

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    This is not true. Whichever definition you give to "now", it cannot involve two events which are time-like separated. There are no "coordinates where [black holes] exist in short time of the external observer after the collapse has started." This is literally a complete contradiction to the GR definition claiming that event horizons do not exist in the past light cone of future null infinity.
     
  9. Schmelzer Valued Senior Member

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    Wrong. Take the Kruskal coordinates https://en.wikipedia.org/wiki/Kruskal–Szekeres_coordinates which have the same light cones as a standard Minkowski space. Put as usual done an infalling line to it which describes the radius of the surface of the collapsing star, I think you have seen that picture somewhere. This line comes from the right down but higher than the X=-T line, moves to the left until it intersects the X=T line (creating the horizon) at some $T_h$ and later hits (creates) the singularity at some $T_s$. Starting with the point where it is behind the horizon the Kruskal time $T>T_h$ will be a time where the BH exists, and a short time later, when the surface hits the singularity, $T>T_s$, is even a time where even the singularity already exists. But T is a normal time-like function, thus, the events on a T=const surface are space-like separated.
     
  10. karenmansker HSIRI Banned

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    IMHO, RJB is correct!
     
  11. Schmelzer Valued Senior Member

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    This is about mathematical facts, not about opinions.
     
  12. sweetpea Registered Senior Member

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    RJB, out of curiosity I followed your link and noticed you give your old or present university ''
    University of Nebraska''. Wondering about your qualifications for writing this paper, I found this page...
    https://www.researchgate.net/profile/Rhoderick_Beery

    I take it you store your 'papers' there. Are your present qualifications to do with the ''Theoretical Physics, Quantum Physics'' subheading on that page ? If yes, what are they? If not, why the mention of your university? To add learned flavour?
    Can you do the math which comes with the subjects '' Theoretical Physics, Quantum Physics''?
     
  13. RJBeery Natural Philosopher Valued Senior Member

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    Why wouldn't I list my Alma Mater? Researchgate allows for alums to follow each other's work and research. And what to do you mean "do the math"? Yes I can do the math of QM. GR and Christoffel symbols...not so much. Theoretical and Quantum Physics are my areas of interest. I feel like you're trying to make some sort of reverse argument-from-authority...confusing -- logic and reasoning are sufficient to stand on their own without regard for who is authoring them. I think you'll find I'm receptive to errors in logic in anything I've written.
    Schmelzer, I can't understand what you're saying. It is against the theory of general relativity for the creation event or the continued existence of an event horizon to reside in an external observer's past light cone. This isn't a controversial claim, this is basic GR.
     
  14. Schmelzer Valued Senior Member

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    So what? "Exists now" refers to a time coordinate. Not to some past light cone. The events inside the BH may be in the future light cone, and may be space-like separated, thus, neither in the future nor in the past light cone. For space-like separated events, you have coordinates where the BH already "exists now".
     
  15. RJBeery Natural Philosopher Valued Senior Member

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    I'm not talking about third parties making remote declarations. I'm talking about observers (i.e. "us") claiming that events within the black hole are occurring now. If events occur at time T from my perspective then at T+1 they existed in my past.

    This is why I tried to focus on whether or not information has been lost to an event horizon. "Has been lost" is necessarily an event occurring in the past.
     
  16. sweetpea Registered Senior Member

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    Thanks for answering.
    If you could give your qualifications then I would have some idea how proficient you are at the math of ''Theoretical and Quantum Physics'' .
    Knowing that will help me take more interest in your papers, i.e. let me know, and perhaps others, you can do the walk and not just talk the talk. As you are well aware, most models are built from math, understanding the math means you can avoid the pitfalls of layman models.
    You must also have noticed how many laypeople 'build' their own 'models' from just an understanding of these layman models.
     
  17. karenmansker HSIRI Banned

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    RJB . . . . gullibility warning!!
     
    Last edited: Mar 27, 2017
  18. RJBeery Natural Philosopher Valued Senior Member

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    I'm not interested in you being interested in my papers, and the idea of doing homework to earn your respect is a bit silly. When math is relevant to the model I provide it. Here's an example: https://goo.gl/uJWO4n

    Bras, kets and matrices have no bearing on any papers that I've written to this point. I tend to make aesthetic appeals because my topics are largely philosophical in nature. On the topic in this thread, however, it isn't a matter of philosophy -- if the astrophysicist community believes that black holes have existed in the past (and no longer do, vis-a-vis micro black holes) then they are contradicting the mathematics of general relativity.
     
  19. Schmelzer Valued Senior Member

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    Yes, but not in your past lightcone.
    Yes, but once contemporaneity is not well-defined but coordinate-dependent in GR, past and future are not well-defined in the same sense. With the exception of the past and future light cones, of course. (And even this only if you ignore solutions with causal loops.)
     
  20. RJBeery Natural Philosopher Valued Senior Member

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    4,136
    Fair. How about this: is there any information which is space-like separated from all external points in spacetime outside of our past light cones?
     
    Last edited: Mar 27, 2017
  21. karenmansker HSIRI Banned

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    638
    An exercise: Suppose (not real!) that you were able to exist within a BH. As an intelligent, scientific observer, what information would you expect to 'observe' when looking outward from the BH interior (i.e., you are observing incoming information from outside the BH). Would 'space and its contents ' appear to be contracting (toward your POV) or expanding (away from your POV)?
     
  22. Schmelzer Valued Senior Member

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    No. Our past lightcone covers all we can see now. Everything which happens later is in some future light cone of some point of our own past light cone.

    In particular, what we see if we look at a BH is the surface of the collapsing BH before horizon formation. So, everything behind the BH is in its future.

    And as I have already said, we can also use coordinates where the BH horizon never forms, because it remains in the future forever.

    So, above positions - the BH exists now and the BH will be created only in the future, or even never - are compatible with GR math, because "exists now" is simply not well-defined.
     
  23. RJBeery Natural Philosopher Valued Senior Member

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    Please reconcile the above statements with the LHC Safety Assessment report discussing evaporating micro black holes.
     

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