QM + GR = black holes cannot exist

Discussion in 'Physics & Math' started by RJBeery, Sep 24, 2014.

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  1. OnlyMe Valued Senior Member

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    The issue here is not as simple as it seems from your comment.

    An early conclusion drawn from GR is that there would be a point where the "force" of gravitation would overcome all other forces and the mass would colapse into a "point singularity", a large mass with zero dimensions, defined at the time as a black hole (or included in the description). There aren't too many serious physicists that belive what we now call black holes, based on cosmological observations, are point singularities.

    A point singularity is not consistent with QM.., but for all intents and purposes GR also has significant real world issues associated with the concept of point singularities.

    I have not read the paper that got this thread going, but from the discussion it seems that it was a theoretical paper, once again exploring the theoretical implications of point singularities. The comclusion seems to be that they cannot exist. That is point singularities cannot exist.

    That got hyped by press and bystander commentary to mean that for QM, black holes cannot exist in any physical form.

    I don't believe that is true. I do agree that it is likely that point singularities do not exist.
     
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  3. paddoboy Valued Senior Member

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    In summation, and as mentioned way back near the

    Exactly...pure simple sensationalism.


    I believe there are not too many scientists that believe that any singularity leads to infinite spacetime curvature and density, and has nought to do with BH's existing.
    As I understand it the physical Singularity that GR predicts at the center of a BH, is simply the end parameters of where GR applies.
    In other words GR predicts its own limitations.
     
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  5. tashja Registered Senior Member

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    The paper clearly states that the backreaction from the Hawking radiation is such, that it prevents the event horizon from ever forming. The star bounces back before reaching the Schwarzchild radius, so a black hole is never created much less a singularity, hence the polemic.

     
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  7. paddoboy Valued Senior Member

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    As with all the hooha a while back regarding the same sensationalist headlines....

    ::::::::::::::::::::::::::::::::::::::::::
    In this new paper, the authors show that if the Hawking firewall idea is correct, then as a star starts collapsing at the end of its life, before it collapses into a black hole Hawking radiation starts kicking in, which pushes back against the collapsing star. So instead of collapsing into a solar-mass black hole, the star almost collapses into a black hole, Hawking radiation stops its collapse, and the stellar core then explodes. So the star dies in a supernova explosion, but no black hole is formed from its core.

    This is interesting theoretical work, and it raises questions about the formation of stellar-mass black holes. But it doesn’t prove that stellar-mass black holes don’t exist, nor does it say anything about intermediate mass or supermassive black holes, which would form by processes other than stellar collapse. And of course the work depends upon Hawking’s take on firewalls to be correct, which hasn’t been proven. To say that this work proves black holes don’t exist is disingenuous at best.

    So don’t buy into the hype. Black holes are real, this work is interesting, and the link-baiters should be ashamed of themselves.

    https://briankoberlein.com/2014/09/25/yes-virginia-black-holes/
     
  8. paddoboy Valued Senior Member

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    Regarding Laura and Harald's paper:

    DR. Vidotto: Hi Tashja, ours was a "friendly citation" as we both think that there is no singularity at the center of a collapsing region, but then opinions and results diverges...

    Paddoboy, Tashja: If Black holes don't form according to Mersini & Pfeiffer's recent paper, then... What are these unseen companions we see in apparent binary systems? Or the polar jets we see emanating from around apparent BH's? What do we put down these other observations to, that give results for objects with an apparent escape velocity at or exceeding "c." What do you think the dark, massive compact object (Sag A*) at the core of the Milky Way is?

    Dr. Vidotto: I totally agree with you. Yes, we observe things that behave exactly as black holes, soon we will also be able to directly observe the event horizon with the new Event Horizon Telescope... so yes, I think that a theory of non-singular black hole should be compatible with such observation.

    In the case of our work on Planck Stars, the singularity at the center of the black hole is removed by quantum effects, and a collapsing shell would bounce back approximately when it reaches a size comparable with the Schwarzschild radius (this calculation is the Fireworks' paper by Rovelli and Haggard). But the key point is that, even if such a bounce for a "bouncing observer" would last a millisecond, for a far-away observer it would take about a time comparable with the age of the universe. So everything goes for us as if there are standard black holes, and observation are not contradicted.


    RJBeery: Do you agree that QM, as a theory, forbids black holes?

    Dr. Vidotto: QM should forbids curvature singularity to form. Also, adding quantum effects convert event horizons into trapping surfaces, i.e. horizons that do not last forever. This is what Hawking also meant, when it was reported that BH do not exists: the asymptotic definition of a BH do not holds, BH are object with a limited life. THis was true because Hawking's evaporation cause their death, and it is even more true if internal quantum effects are turned on.

    What Mersini & Pfeiffer is a different story. They notice that, during a collapse, there is already Hawking evaporation, and this was known. They says that the backreaction of this radiation is so strong to prevent the Schwarzschild horizon to form. I think this should be better understood. It could very well be that this backreaction was previously underestimated, but it think it is more likely that there is a flaw in the calculation they are doing. For instance the way they plug the Hawking energy density into the Friedmann equation for the interior of a star that is a non-vacuum and non-static spacetime, looks pretty suspicious...



    RJBeery: And would you agree that QM is incomplete or even wrong if black holes do "exist"?

    Dr. Vidotto: No, not at all, see above.

    You're welcome! Cheers,
    Francesca


    Dr. Francesca Vidotto
    ---------------------------------------------------------------------------
    Institute for Mathematics, Astrophysics and Particle Physics
    Radboud University Nijmegen - The Netherlands"
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    from post 97:
     
  9. OnlyMe Valued Senior Member

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    Tashja, it sounds like your are trying to interpret a theoretical paper, as if it is intended to describe reality. Re-read even the section you quote, strike out all of the theoretical references it uses as a basis, for their conclusions.., and then see if there is any, even implied aplication to reality.
     
  10. tashja Registered Senior Member

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    OnlyMe, It sounds like you are trying to interpret my post into something it's not

    Please Register or Log in to view the hidden image!

     
  11. Russ_Watters Not a Trump supporter... Valued Senior Member

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    You can't just hand-wave the EH away by claiming it doesn't exist without fully developing the implications. Since you accept that there is a physical signficance to the Schwarzchild radius and accept at least some of what that significance is said to be by black hole theorists, you accept at least some of what defines an "event horizon" under black hole theory:

    1. You claim infalling observers never reach it. Fine. Most physicists disagree, but whatever -- you've at least been clear on that.
    2. But what about observers inside the Schwarzchild radius? Can they escape?

    I'll put it a little more directly: you are pecking-around the definition for "Event Horizon" without actually disagreeing with it.
    "An event horizon is, in general relativity, a boundary in spacetime beyond which events cannot affect an outside observer."
    http://en.wikipedia.org/wiki/Event_horizon

    See, the key to the definition of "Event Horizon" is that the inside observers can't get out, not that outside observers can't get in. So even if it is someday proven that infalling matter piles-up just outside the EH (while somehow also expanding with the EH as it grows?), it is still an event horizon.
     
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  12. RJBeery Natural Philosopher Valued Senior Member

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    a) Linking to papers in peer-reviewed journals containing mathematical analyses is a "form of argumentation" I feel has considerable merit.

    b) I'm neutral on the absolute value of scientific consensus. Why would anyone have "angst" against it?

    c) I'm here to explore the truth. If facts and evidence make me draw unpopular conclusions then I ask questions until I understand why that evidence is interpreted differently by others; I then change my interpretation of the facts if it's warranted. To this point I have not seen any persuasive argument to conclude that black holes exist, and I more than a few to suggest that they don't.
     
  13. RJBeery Natural Philosopher Valued Senior Member

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    Agreed. I agree with you here. The problem is that for this scenario to exist, that event horizon (and black hole) must be eternal, meaning that it must have always existed. I posted a thread on the necessity of the eternal age of black holes a few years ago. If we have an event horizon with a radius = r, which we can "see and measure" and all mutually agree exists, run time backwards in your mind until that radius was r/2. What did that sequence of events look like? Was matter being ejected from the event horizon? Can you appreciate the problem here?
     
  14. Russ_Watters Not a Trump supporter... Valued Senior Member

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    No, I don't see why that is necessarily true and the only problem I see is you arguing against your own scenario. Could you please explain in more detail what you see that you think requires black holes to be eternal?
     
  15. Russ_Watters Not a Trump supporter... Valued Senior Member

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    ...or perhaps a link to that old thread.
     
  16. RJBeery Natural Philosopher Valued Senior Member

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    Did you digest what I wrote? Start with an existing black hole and an event horizon radius R at time T. Say the black hole is being "fed" an infinite series of golf balls, one after the other, which are all stamped numerically such that the current golf ball external to the event horizon is 1.0 * 10^32.

    See linked img: http://i1373.photobucket.com/albums/ag380/rjbeery/golfball_black_holes_zps339d1899.png

    Now, starting at time T, run the clock backwards to T_past until R_past = R/2. What does the scene look like? Do golf balls with numbers less than 1.0 * 10^32 appear? If they do then there is a time T_crossover such that T_past < T_crossover < T where we would have witnessed the event horizon expand due to matter crossing it. This cannot happen. If the golf balls numbered 1 through (1.0 * 10^32 - 1) ever existed then we would theoretically be able to observe them, with perfect instrumentation, forever. But in this thought experiment the black hole is made of nothing but golf balls. This is a contradiction, therefore the event horizon cannot exist.
     
  17. brucep Valued Senior Member

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    • They're are holidays of ignorance in this bloggers discussion of a predicted firewall. He calls it a Hawking firewall as if the prediction of a super hot bath of Hawking radiation impeding the progress of the falling observer was Hawkings idea. He also doesn't understand why the infalling observer won't be subject to tidal forces until spaghettifacation at r=0. This is a much better discussion.
      http://www.nature.com/news/stephen-hawking-there-are-no-black-holes-1.14583

      I'm going to dervive the Hawking temperature from the Unruh temperature to show the prediction for the hot firewall. I'll link it to this post. I wondered about this when I was trying to learn GR.

     
  18. RJBeery Natural Philosopher Valued Senior Member

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    This is false. Tidal forces are dependent on mass of the black hole and distance from it. (Unless you're using an extremely odd definition of "spaghettification")
     
  19. RJBeery Natural Philosopher Valued Senior Member

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  20. brucep Valued Senior Member

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    The following is the derivation of the Hawking temperature from the Unruh temperature. The key is g_shell factored by gama for the local temperature and cancelled by the remote bookkeeper Schwarzschild coordinates. This predicts the Hawking temperature goes to very large locally and very small if on served from remote coordinates. For r=2M it predicts that g_shell is infinite. Based on an unphysical coordinate singularity called the Schwarzschild event horizon where gama blows up. Because of the coordinate singularity I just forgot about it. Hawking is saying the fixed coordinate singularity is an artifact of the classical solution and an apparent horizon is what describes the actual natural phenomena. That's where the quantum discussion begins.



    T_Unruh = h*g_conventional/4(pi)^2*k_Boltzmann*c [eq.1]
    g_conventional/c^2 = (M*c^2/r^2)(1-2M/r)^-1/2

    g_shell = g_conventional/c^2 = (M_meters*c^2/r^2)(1-2M/r)^-1/2 [eq.2]
    Substituting [eq.2] into [eq.1]

    T_Unruh = [h*M_meters*c] / [4(pi)^2*k_B*r^2 (1-2M/r)^1/2)]

    Let r > 2M the Schwarzschild event horizon. Account for the redshift measured from remote coordinates
    (1-2M/r)^1/2 / 1-2M/r)^1/2 =1

    T_Hawking=[h*c*M_meters/4(pi)^2*k_Boltz*(2M_meters)^2]
    T_Hawking = h*c/16(pi)^2*k_Boltz*M_meters
     
  21. brucep Valued Senior Member

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    I write observed and the IPADS changes it to on served. Just like it just changed IPAD to IPADS. Nonsense.
     
  22. brucep Valued Senior Member

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    He thinks the remote bookkeeper coordinates are preferred. Since he's been told that is bullshit he continues to look for stuff that he thinks confirms his bullshit analysis. The 'natural philosopher' in his view is a crank.
     
  23. paddoboy Valued Senior Member

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    Tidal forces are evident only when there is significant difference in the strength of gravity between two points. eg: You could cross the EH of the SMBH at the center of the Milky Way and not be affected by any tidal forces.
     
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