Hawking radiation

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

  1. Q-reeus Valued Senior Member

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    2,606
    Conveniently ignoring what should be an obvious issue with GR is one thing, but you actually do not even recognize it? The answer given to question here should ring a bell:
    http://physics.stackexchange.com/qu...vature-in-the-schwarzschild-metric-due-to-a-c
    If no bell rings, if you can't make an obvious connection and see logical issues with supposed properties of a TT GW. Or more generally inconsistency within GR of the notion of gravitational field 'self-gravitation', don't worry. Yours will be an overwhelming majority perspective. Even if your own rival theory is far from enjoying such.
     
    Last edited: Oct 29, 2015
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  3. The God Valued Senior Member

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    Thank you Tashja....

    When I raised the issue regarding CMBR absorption at faster than HR and also improbability of Isolated BH (BH in otherwise empty space..of Misner), Paddoboy jumped on me with absuses after abuses......Thankfully now he got his response and reference. Will he show courage to admit his silly takes? I am afraid not.

    Prof Misner has made it very clear that evaporation of a stellar BH is nothing but a fantasy. Thanks once again.
     
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  5. The God Valued Senior Member

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    I do not know so far how many participants here are aware of what the Yilmaz additional terms is for, except probably you and Schemelzer. I had a vague idea that Yilamz with his additional term was talking about Gravitational Influence of other sources, to resolve the superimpostion related issues by including the same in right hand side tensors. This way I was wondering why it is not Yilamz contribution to GR rather than Yilmaz Theory, But no I was wrong, I read the Yilmaz paper, and his addition of term is more towards the ''funky 'source' gravity further gravitates" aspect. This is bound to give an additional component in the week field domain. I will read Yilmaz counter to this, but looks improbable.
     
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  7. Q-reeus Valued Senior Member

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    Yilmaz theory is imo and for reasons already covered and explained in referenced articles, superior to GR particularly in terms of self-consistency.
    And btw your last line in #362 misses the mark. I'm sure Misner would respond that 'BH' growth in current epoch owing to CMBR is 'temporary'. And will if current best-estimate extrapolations bear out indefinitely, give way to eventual 'evaporation' once CMBR T < HR T. As to whether horizons thus HR exists at all is a separate issue.
     
  8. The God Valued Senior Member

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    But will this condition ever arise CMBR T < HR T? I do not think so.

    Yeah, you can argue that in some epoc after almost eternity CMBR may go away or its T goes down below HR T. You see the theory behind origin of this CMBR, is a separate issue. My take was that can you find a BH in an 'empty space', infact that would be the perfect place to test GR as well.
     
  9. The God Valued Senior Member

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    3,546
    Q-reeus,

    The source of below comparison (not mine) is not authenticated, but it hardly matters. The pointed questions / parameters are exhaustive and open. The list is extremely biased (favorable) towards Yilmaz....See if any one can indulge in pointwise rebuttal to this table. By posting this I am not implying that I am supporting Yilmaz over GR, but I am sure if pointwise discussion (healthy and intelligent) is conducted then lot of learning can be there..



    GR /Yilmaz

    1. Type of theory (Gauge)

    No/gauge theory

    2. Local conservation of enery-momentum?

    GR - No/ YT - Yes

    3. Definite stress-energy tensor exists?

    GR - No/ YT - Yes

    4. Exact closed gravity wave solutions
    for arbitrary field strengths?

    GR - No/ YT - Yes

    5. True Lagrangian exists?

    GR - No / YT - Yes

    6. Interaction can be deduced from gauge
    principle?

    GR - No/ YT - Yes

    7. Strong principle of equivalence?

    GR - Not deducible / YT - Holds

    8. Theory is quantizable?

    GR - NO / YT - Yes
     
    Last edited: Oct 29, 2015
  10. Q-reeus Valued Senior Member

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    2,606
    Why not just post a link, which I presume would be: http://albert51.tripod.com/yilz.html
    Yes it's 'not authenticated' in the sense of being that writer's personal exposition, and is a bit dated in that Reference [9] should have at least a [10] furnishing link to rebuttal of Fackerell.
    If no feedback comes via tashja from Alley or Robertson, both far abler than myself in defending Yilmaz theory, I see no point in further debate/discussion. Because what has really gone on is mostly the usual defamatory rhetoric from one notorious individual in particular. Quality not quantity counts, but only for those with enough nous and integrity.
     
  11. The God Valued Senior Member

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    3,546
    Thats why I avoided the link, because this man would have killed the discussion at the threshold itself....
     
  12. Schmelzer Valued Senior Member

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    3,703
    It does not. If there is no matter, then the Einstein equations are \(R_{mn}=0\). This is elementary GR, well-known, and means, the Ricci tensor, which you can name Ricci curvature if you like, is zero in the vacuum. This does not mean that the curvature is zero, because the curvature is defined by the full curvature tensor \(R^k_{lmn}\). And, of course, for gravitational waves in the vacuum there will be also \(R_{mn}=0\), but \(R^k_{lmn}\neq 0\). What is the problem here?

    And why do you think there is anything inconsistent if one talks about self-gravitation? This is, anyway, only sloppy talk, what it means is simply that the Einstein equations are complex nonlinear equation, so that one cannot simply add two solutions of GR to obtain another one.
    As if I would reject a position simply because it is a majority position. I reject a majority position if I see good arguments to reject it. If I see no such reasons, I defend a majority position even if it is a majority position. As I have, for example, defended the majority position about the violation of Bell's inequality against cranks like Benjamin Schulz and Joy Christian.

    To reject a position simply because it is a majority position I leave to pubescents.
     
  13. Q-reeus Valued Senior Member

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    2,606
    You continue to miss the real point. Non-linearity per se does not imply 'self-gravitating'. Zero Ricci curvature implies absence of *all* sources of gravitation in such region, not just matter density. Hence, explicitly, form of exterior Schwarzschild metric forbids existence of field self-gravitation. Many try and impose it via 'tricks' so as to justify BH 'self-sustaining fossil field' etc. but such cannot be true to the basic statement of EFE's. Shuffling lhs 'effect' terms to rhs and pretending such legitimately becomes 'source' is often done but that doesn't make it legitimate practice. Yilmaz gravity does not need or use such subterfuges.
    Similarly a hypothetical TT GW is in GR a nonsense for the same basic reason - zero Ricci curvature directly implies zero stress-energy-momentum density in such 'wave'. In other words, as Eddington maintained, all you can have is 'ripples in the coordinates'. A shadowy artifact of maths of a self-inconsistent theory.

    Only recently appreciated that Yilmaz theory predicts exactly the same TT GW's as GR in weak field regime. In that respect I no longer claim absence of GW's is specifically evidence against GR. While in Yilmaz theory non-zero GW energy-momentum has a self-consistency entirely lacking in GR, TT character could not be exact owing to the 'self-gravitating' requirement. For other reasons not to be divulged here, even such Yilmaz almost purely TT GW's are not possible.
     
  14. Schmelzer Valued Senior Member

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    3,703
    Correct, I completely miss any point here. No physicist really cares about some popular descriptions for laymen use the phrase "self-gravitating". I would expect that many GR textbooks do not use this phrase at all, and if they use it, I would guess they use it simply to refer to non-linearity of the field equations.
    I don't even see any reason to try. Which terms of an equation are written on the left side and which on the right side is completely irrelevant, it does not matter at all. You can write the Einstein equations as \( G_{mn}=T_{mn}\) as well as \( G_{mn}-T_{mn}=0\), you can subdivide \( G_{mn}\) into, say, a second order term \( \square g_{mn}\), which is, for small modifications, almost linear, and all other terms which are non-linear even on the small scale, and all this is completely legitimate, because it does not change the equations even a single bit. And all this plays, at best, a pedagogical role, and is otherwise completely irrelevant, and, in particular, cannot cause any foundational problem.
    No. To reduce a solution to "ripples in the coordinates" requires \(R^k_{lmn}=0\). That the Ricci tensor \(R_{mn}=0\) is necessary for this, but not sufficient. In particular, you cannot transform the Schwarzschild solution into the gravitational vacuum (the Minkowski metric) by a simple transformation of coordinates.
    Which would be anyway nonsensical, because the GWs which would have to exist, if all what we think we know about stars, galaxies, and what can happen to them would be correct, are below the threshold we are able to measure. Thus, observation of GWs would be the unexpected things, pointing to new, unexpected physics of sources of unexpectedly strong gravitational radiation. (At least this was correct a few years ago when I have checked, if you have different, more actual information, tell me about this).
    Sorry, but claims that GR is not self-consistent are extremely dubious, a clear indication of crank science. So, if one simply ignores those who make such claims one usually does not make an error. (An exception is Logunov's RTG. He has made the error of making wrong claims about inconsistency of GR, which has extremely harmed his scientific reputation, which has also harmed the reputation of the theory of gravity he has proposed as an alternative, but which is nonetheless a viable alternative to GR.)

    GR has a lot of weak points, from singularities, the non-existence of a local energy-momentum tensor for gravity and dark matter to incompatibility with quantum theory, but this does not mean inconsistency. GR is an internally consistent theory. At least I have not found any inconsistency.

    If there is some consistent formulation of Yilmaz theory I don't know. At least I have not seen one which I would have recognized as defining a consistent theory.
     
  15. OnlyMe Valued Senior Member

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    Once again great work Tashja!

    Two birds with one stone this time, touching on both the initial Hawking radiation debate and the Yilmas theory. I know very little of the Yilmas theory and only speculate about the reality of Hawking radiation, so his comments on both are appreciated.
     
  16. Q-reeus Valued Senior Member

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    2,606
    You thought I was implying such? No - quite aware that Weyl curvature is non-zero there. And, despite all your other comments, including that cheap 'crank' shot which is a bit ironic given your own earlier reactions to such hurled your way, still not getting the significance of zero Ricci curvature in exterior Schwarzschild region. But I'm burning midnight oil and must go.
     
  17. Schmelzer Valued Senior Member

    Messages:
    3,703
    Yes, this is what "as Eddington maintained, all you can have is 'ripples in the coordinates'" suggested. "Ripples in the coordinates" are something you can get rid by choosing coordinates which do not have such ripples. It was only a weak suggestion, so, its fine that you did not want to imply this.

    And, indeed, I'm still not getting the point where you think zero Ricci curvature in the exterior Schwarzschild region is significant. All ideas I have why this might be significant are cranky, sorry, there is not a single meaningful, reasonable among them.

    Sorry for such a misinterpretation, but it is your suggestion that zero Ricci curvature is somehow important, without giving detailed explanations why, combined with my inability to find a non-cranky reason why this should be somehow important, which leads to such "cheap 'crank' shots". What else can I do, once I do not know non-cranky reasons?
     
  18. paddoboy Valued Senior Member

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    21,647
    No he hasn't.
    Professor Misner said in his opening paragraph.......
    I think there is a consensus that a black hole in otherwise empty space would emit radiation as predicted by Hawking and confirmed by a variety of other approaches to the question. This conclusion is based on an acceptance of classical general relativity for the geometry of spacetime, and a belief that quantum field theory in a curved spacetime background is an acceptable approximation to the as yet uncompleted search for a unified theory of gravity with quantum mechanics.
    As usual, you are twisting facts to suit your agenda. And a dishonest misinterpretation to boot. Surely you did not believe that such dishonesty would go unnoticed? Even another old adversary of mine picks up this gross inaccuracy of yours at best, or just plain gross dishonesty at worst.
    I believe you had no idea at all about Yilmaz theory as neither did I.
    You saw an opportunity as others did to use it to support your agenda, that's all.
    The evidence of course is just as Misner inferred and what I said many times....a storm in a teacup....not even a ripple.
    GR reigns supreme at this time.
     
    Last edited: Oct 29, 2015
  19. paddoboy Valued Senior Member

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    21,647

    Please Register or Log in to view the hidden image!

    What has really gone on actually, is just the application of common sense and logic, without any addition of conspiracy to muddy the waters.
    I have defended GR logically and reasonably on the grounds that Yilmaz theory has been around for 20 years and more, and yet still lingers as near unknown even among the professional experts such as Professor Lewis and Professor Hamilton, and an obvious lack of interest by Professor Thorne.
    If then using the terms that it is a storm in a teacup, or barely a ripple, constitutes "defamatory remarks" then I suggest that my other claim re your own agenda must be pretty close to reality.
     
  20. paddoboy Valued Senior Member

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    21,647
    deleted booboo
     
  21. OnlyMe Valued Senior Member

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    The following quote has been edited for clarity.

    If I understand The God's intent in that one statement, aside from any hostile implications contained in his post as a whole.., and that paddoboy's response was a response to that statement....

    First, it is my opinion that The God was being theatrical almost to an extreme and his statement could be taken as adding some emphasis to the professor's response other than intended by the professor, but while a theatrical exaggeration, his statement is not wholly inconsistent with the professors comments. Though unless his intent is to incite conflict, he should be more careful with his words... In the following quote of the professor's comments, note the portion I have emphasized in bold.

    What I understand the professor to have been saying, is that in an ideal vacuum solution (empty space), which does not exist in reality, a black hole would emit Hawking radiation..., and none of the compact objects we currently believe are black holes, are believed to emit Hawking radiation.

    Is that the same as saying Hawking radiation is fantasy? Absolutely not. It puts Hawking radiation in a similar category as say a schwarzchild black hole, we don't know them to exist in our reality, but they play a significant role in our attempts to understand that reality.

    Even further when he (the professor) adds in the same quote, "and confirmed by a variety of other approaches to the question.", where I assume (risky I know) that he is referring to some of the analogues earlier discussed, he is raising the issue well above what I would expect of a fantasy.

    Hypothetical as it relates to black holes, at present yes! A fantasy, absolutely not!
     
  22. paddoboy Valued Senior Member

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    21,647
    Would you like to reference back to where you claimed exactly that, and where I hurled abuse after abuse upon you?
    No silly mistakes on my part, HR is a quantum effect that is generally accepted by mainstream cosmology...I have said that many times. And I'm rather pleased that an expert like Professor Misner also confirms that.
     
  23. paddoboy Valued Senior Member

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    Bingo. And I am also pleased you noticed the usual hostile intent.
    The Professor's intent is obvious. HR is logically a minimal scenario. Most BH's by there very nature, will be swallowing far more than what is evaporated due to HR, at this time of course. Just as obvious is the fact that in the far far distant future HR will eventually gain ascendancy and the BH should indeed evaporate.
    In a similar vane, all of spacetime is expanding, but over smaller denser scales, the effects of gravity overcome that expansion and systems such as our local group and further afield, are void of any obvious spacetime expansion and are gravitationally bound.


    What the Professor said.....
    " At a minimum these black hole candidates are all sufficiently massive that the 3 deg cosmic microwave radiation would be getting absorbed by these black holes at a rate much higher than the suggested Hawking radiation energy loss. Thus all known compact objects, which have masses near or above one solar mass, are currently gaining mass, making their B-H temperature decrease still farther. "


    OnlyMe:
    For many reasons including your last castigation of me for the many rounds of insulting remarks and below the belt posts that are taking place on this forum, particularly with the god and myself, I'm at least going to try and disentangle myself from such participation.
    Part of my decision and reasons are that in time the mods and administrators will start taking action when enough complaints are forthcoming.
    And as per the rules, it will not just be the instigator of the undesirable posts that will be banned, it will be all that are taking part in such behaviour, which would include me.
    This would put the god at a distinct advantage.
    He is in my opinion obviously the former poster known as rajesh Trivedi. This would give him that extra handle to come back into the fray, while I remained banned.

    I certainly hope though, that the pressure and observations you focused on me re my part in these exchanges, continues with regards to the god if he continues on with the nonsense.
    I of course will continue to refute any crazy or unsupported claims that he or anyone else makes to the best of my ability.
     

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