Hawking radiation

Discussion in 'Physics & Math' started by hardalee, Sep 16, 2015.

  1. brucep Valued Senior Member

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    Since the Yilmaz theory of gravity has been introduced to this thread it's interesting to note just how far afield these predictions deviate from observation. Some text is in the abstract with further discussion at the end of the paper. The way it stands it's a steady state cosmological theory.
    http://arxiv.org/pdf/0705.0080.pdf
     
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  3. Q-reeus Banned Valued Senior Member

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    Evidently some prefer a quick skim of things, or maybe just conveniently ignore. Again, the article by S. Robertson I first linked to in #219: http://arxiv.org/abs/1507.07809
    Beginning p5, under 4 Discussion. Ibison's analysis is covered there and why it was wrong. Just for completeness, and to head off a further unwarranted assault re the false 'Yilmaz = steady state cosmology', here's another advocate of that faulty application of Yilmaz theory: http://www.olduniverse.com/1,1,6 Cosmology.pdf
    Wrong application does not invalidate the underlying theory. Einstein's original use of 'cosmological constant' in order to create his own 'steady state cosmology' should be a reminder of the distinction between models and basic theory.
     
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  5. paddoboy Valued Senior Member

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    Also in WIKI it says......
    The Yilmaz theory of gravitation is an attempt by Huseyin Yilmaz (1924-2013) (Turkish: Hüseyin Yılmaz) and his coworkers to formulate a classical field theory of gravitation which is similar to general relativity in weak-field conditions, but in whichevent horizons cannot appear.

    Yilmaz's work has been criticized on the grounds that

    • his proposed field equation is ill-defined,
    • event horizons can occur in weak field situations according to the general theory of relativity, in the case of a supermassive black hole.
    • the theory is consistent only with either a completely empty universe or a negative energy vacuum[1]
    It is well known that attempts to quantize general relativity along the same lines which lead from Maxwell's classical field theory of electromagnetism to quantum electrodynamics fail, and that it has proven very difficult to construct a theory ofquantum gravity which goes over to general relativity in an appropriate limit. However Yilmaz has claimed that his theory is 'compatible with quantum mechanics'. He suggests that it might be an alternative to superstring theory.

    In his theory, Yilmaz wishes to retain the left hand side of the Einstein field equation(namely the Einstein tensor, which is well-defined for any Lorentzian manifold, independent of general relativity) but to modify the right hand side, the stress–energy tensor, by adding a kind of gravitational contribution. According to Yilmaz's critics, this additional term is not well-defined, and cannot be made well defined.[citation needed]

    No astronomers have tested his ideas, although some have tested competitors of general relativity; see Category:Tests of general relativity.

    and another paper at......
    http://arxiv.org/ftp/arxiv/papers/0705/0705.0080.pdf
    In conclusion it says.....
    For a flat space FRW metric the Yilmaz theory demands that the total energy density (vacuum, matter, radiation, etc) is zero. In a matter conserving cosmology, if the vacuum energy density is assumed positive, the Yilmaz theory is compatible only with a universe where the total energy density is devoid of matter, radiation, and vacuum energy. Alternatively, if the vacuum energy density is allowed to take either sign, the Yilmaz theory predicts a cosmology that is always decelerating, with . Both of these are at variance with observation.

    The Yilmaz theory requires a non-uniform distribution of matter in order to generate the curved-space FRW metrics. That is, whilst all co-moving observers everywhere see the same evolution of the scale factor, they do not see the same local distribution of matter. Since both curvature and matter distribution are components of the local environment, this means that all co-moving observers do not see the same universe. It must be concluded that the Yilmaz theory does not accommodate the curved space instantiations of the Cosmological Principle.
     
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  7. Q-reeus Banned Valued Senior Member

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    Repetition of a freshly debunked argument may seem like a good idea to some, but others recognize the stupidity of such a tactic.
     
  8. The God Valued Senior Member

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    This guy Paddoboy, has heard about Yilmaz first time and he has to poke his nose, so he started with wiki....He has no point to offer.
     
  9. paddoboy Valued Senior Member

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    And yet you yourself are in the same boat.

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    Again your shameless hypocrisy knows no bounds.
    My excuse? I'm not that much into checking out every scientific paper by all and sundry, all doing their bit to debunk the great man and his GR, but considering the paper my friend Q-reeus has linked to was only July this year, I would say their has not been much time for peer review......Or do you see yourself as that appropriate peer review?

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  10. Schmelzer Valued Senior Member

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    The problem with this paper is that it does not matter at all, because, if the issue raised by Misner is correct, Yilmaz theory is simply dead, and a nice picture of global evolution cannot revive it.

    Physics does not work following the principle oh, this solution is nice, +1 for the theory, and if a theory has 5 nice solution but only 3 bad ones, it remains in the positive. If it has one bad solution, it is dead, falsified. And if, in particular, the classical limit is not Newtonian gravity, it is as dead as possible.
     
  11. Q-reeus Banned Valued Senior Member

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    So is the issue raised by Misner actually correct? Please point to any equation(s) and/or steps leading to such in rebuttal by Yilmaz et al, that iyo is obviously false. Also note that both parties accuse the other of supporting a theory that does not match Newtonian gravity in the weak field limit. And it's not an obvious discrepancy like Keplerian orbits of a test mass, but a more subtle one involving role of certain stress-energy-momentum tensor components.
    What constitutes a bad solution in this case - one that is genuinely intrinsic to the theory? And before you answer, recall how often you have brought up the unreasonableness of e.g. CTC's, wormholes, white holes as alloweable solutions to GR's EFE's. If you hitch your wagon to a star, better check it's not a wandering one.
     
  12. Schmelzer Valued Senior Member

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    5,003
    Feel free to believe otherwise. I have explained and justified my decision.
    So, we have one claim of mathematical invalidity of a claim (Newtonian limit of GR) which is part of standard textbooks, vs. a claim of mathematical invalidity of an alternative theory nobody has really cared about. The first claim is extraordinary, thus, needs extraordinary evidence. I have not seen it. The second claim is nothing extraordinary.
    It is sufficiently obvious. There is a difference in the equations. This may show up already in the Newtonian limit, or not. Once the Yilmaz side claims that GR has the wrong Newtonian limit, but not his theory, there is not even disagreement that it shows up. If it shows up, and if the GR Newtonian limit is correct, Yilmaz theory is dead.

    So, it obviously reduces to the claim that textbook-level mathematics - the Newtonian limit of GR - is invalid. This is an extraordinary, crank-suspect claim. Given that the conflict has been already evaluated by the peer-reviewers, and the claim was rejected, I do not plan to second-guess.
    One where the proposed alternative has a better solution.

    If, in particular, the domain where two theories disagree is one where the prediction can be tested, the fate of the theory is decided. The Newtonian limit of GR can be tested.

    If it is outside this domain, it is more problematic to show that one theory has to be rejected. One needs other arguments - like that one theory violates other well-known, well-established principles, the other not.

    And if there is not even an alternative theory which does not have this problem, then the theory with the unreasonable solution will be used as the best what is available today. That means, one recognizes that it is false, but a false theory which is a good approximation is better than nothing.

    Solutions with causal loops and nontrivial topology I reject based on another, ether, interpretation of the Einstein equations and my ether theory as alternatives which do not have the problem.
     
  13. paddoboy Valued Senior Member

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    http://arxiv.org/ftp/arxiv/papers/1510/1510.00621.pdf

    Observation of thermal Hawking radiation and its entanglement in an analogue black hole:

    Abstract:
    We observe a thermal distribution of Hawking radiation, stimulated by quantum vacuum fluctuations, emanating from an analogue black hole. This confirms Hawking's prediction regarding black hole thermodynamics. The thermal distribution is accompanied by correlations between the Hawking particles outside the black hole and the partner particles inside. We find that the high energy pairs of Hawking and partner particles are entangled, while the low energy pairs are not. This has implications for the problem of information loss in a black hole. The observation of Hawking radiation reported here verifies Hawking's semiclassical calculation, which is viewed as a milestone in the quest for quantum gravity.

    conclusion:
    In conclusion, thermal Hawking radiation stimulated by quantum vacuum fluctuations has been observed in a quantum simulator of a black hole. This confirms the prediction of Hawking regarding spontaneous pair production in the presence of a horizon. This has implications beyond the physics of black holes, as it confirms the semiclassical step toward the understanding of quantum gravity. The Hawking spectrum is observed, as are the correlations between the Hawking radiation exiting the black hole and the partner particles inside the black hole. These correlations are surprisingly narrow in position space, which implies that the high frequency tail of the distribution of Hawking pairs are entangled. On the other hand, the overall weakness of the correlations in position space implies that the low frequencies are not entangled. The entanglement confirms that there is an issue of information loss within the semiclassical approximation.
     
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  14. Q-reeus Banned Valued Senior Member

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    A lot of if's there in #289. I'm satisfied from another angle that Yilmaz gravity has a self-consistency lacking in GR. And it doesn't bother me others have their mind made up otherwise.
    [Including being swayed by *analogue* experiments]
     
  15. brucep Valued Senior Member

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    Consider next time linking the abstract rather than the PDF. This way you can link any citations. Forgot to thank you for finding and linking.
     
    Last edited: Oct 25, 2015
  16. paddoboy Valued Senior Member

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    Good advice bruce.....will do.
     
  17. paddoboy Valued Senior Member

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    I thought that something as potentially momentous as this "Yilmaz theory" would be creating somewhat of a stir within professional scientific circles, so I E-Mailed a couple of Professional people, whose name I'm not disclosing at this time. Trust me, I have no need to lie as others seem to find the need to do for personal agenda reasons.
    There replies were as follows........
    "Never heard of it. A quick look and it seems like it fails at the first hurdle in that it fails to reproduce Newtonian gravity.
    Just because some one has a brain fart, it does not make it a viable alternative to GR".



    and


    "I'm afraid I am not familiar with Yilmaz theory".

    So much for stirring up scientific circles!
     
  18. Q-reeus Banned Valued Senior Member

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    Shit stirring via anonymous email responses from individuals unfamiliar with a not-consensus-adopted theory, one of whom has obviously mistakenly relied on C.Misner's critique but evidently has no knowledge of the rebuttal to it, is predictable coming from the resident no-tricks pony professional shit-stirrer. One who tries to give the impression of understanding GR (or rival theories), yet was forced into a humiliating back-down and confession over a basic matter involving just SR. Hahahaha.

    I pity those whose intellectual and moral limitations channel them into thinking or at least shouting loudly that truth is decided on a vote of hands.
     
  19. paddoboy Valued Senior Member

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    Just pointing out some facts my dear friend, despite it upsetting your apple cart. Like I said, if this had any thing really going for it, it would be creating a stir within scientific circles. It's not doing that, except of course within your own mind. Now why would that be?
    Just an observation q-reeus, you seem intent on just playing games here as the one who calls himself the god does.Humiliating backdown, confessions etc etc.

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    Rather a childish approach.
    Not sure about the backdown you refer to but anyway if that gives you pleasure, you suck it up big boy!

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    Let me reiterate: The comments were from recognised professionals, and certainly not some tin arsed anti GR amateur.
     
  20. paddoboy Valued Senior Member

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    A third reply in short time.....
    Kip S.Thorne<kip@tapir.caltech.edu>;
    "It is a very long time since I looked at the Yilmaz theory, and I do not have time to refresh my memory. I suggest you contact Professor Clifford Will <cmw@physics.ufl.edu>. He is probably the world’s best expert on experimental tests of relativistic theories of gravity".
    sincerely,
    Kip Thorne
    """"""""""""""""""""""""""""""""""""""""""""""""""
    "

    Still not much stirring, But I'll certainly contact Professor Will for his update.

    Done!
     
    Last edited: Oct 27, 2015
  21. OnlyMe Valued Senior Member

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    Paddoboy, I do understand why anyone who might be recognized as a "professional" on the topic might not want to be associated with this discussion, however the abscence of names attached to the quotes, degrades their value, as quotes from authority. It seems there has already been some question of authority in the discussion, where names were involved.... They, the quotes.., become just words. You do understand that you are already in a debate where your position has been subject to question.., rightly or not.., yes?

    That said the first of your worthless unidentifiable quotes does sound about right. No theory of gravity that does not "reproduce Newtonian Gravity", as a weak field limit, can be taken as a serious description of reality, since Newtonian Gravity has been proven locally accurate.
     
  22. paddoboy Valued Senior Member

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    27,543
    As you say in the first sentence. Irrespective and despite your derision of replies from reputable people I can assure you, the decision not to name them was mine, purely out of the downfall from the Professor Bennett Link debacle and him leaving the forum.
    Certainly more reputable though than those pushing this Yilmaz hypothesis as a new saviour of gravity and the Universe, obviously.
    I'll stick with my decision at this time, and have just posted a third reply with the source named.
    DONE!
     
    Last edited: Oct 27, 2015
  23. paddoboy Valued Senior Member

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    27,543
    In the meantime while waiting for his reply [hopefully] here is a paper by Professor Wills.

    http://relativity.livingreviews.org/Articles/lrr-2006-3/download/lrr-2006-3Color.pdf

    :The Confrontation between General Relativity and Experiment:


    Published by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute)

    Abstract:
    The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed. Einstein’s equivalence principle (EEP) is well supported by experiments such as the E¨otv¨os experiment, tests of special relativity, and the gravitational redshift experiment. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse–Taylor binary pulsar, and other binary pulsar systems have yielded other tests, especially of strong-field effects. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible.

    conclusion:
    7 Conclusions We find that general relativity has held up under extensive experimental scrutiny. The question then arises, why bother to continue to test it? One reason is that gravity is a fundamental interaction of nature, and as such requires the most solid empirical underpinning we can provide. Another is that all attempts to quantize gravity and to unify it with the other forces suggest that the standard general relativity of Einstein is not likely to be the last word. Furthermore, the predictions of general relativity are fixed; the theory contains no adjustable constants so nothing can be changed. Thus every test of the theory is either a potentially deadly test or a possible probe for new physics. Although it is remarkable that this theory, born 90 years ago out of almost pure thought, has managed to survive every test, the possibility of finding a discrepancy will continue to drive experiments for years to come.
     

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