Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

New Hawking paper

  1. Jul 18, 2005 #1


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    noted in surrogate sticky

    I printed this paper out and tried unsuccessfully for an hour or so to understand his argument. maybe someone else can elucidate. I am stumped.
    The paper is short, 5 pages, with few formulas. It goes over the
    argument he gave at the Dublin conference last year, about BH
    information loss (not). I was hoping when his paper on this came out
    that I would understand his reasoning better, but it didnt happen.
    Last edited: Jul 18, 2005
  2. jcsd
  3. Jul 18, 2005 #2
    Very interesting. I don't understand it at all, but I found this curious, "My work with Hartle showed the radiation could be thought of as tunnelling out from inside the black hole." I suppose he's saying that instead of virtual particle pairs being extracted from the quantum fluctuations in empty space being the reason black holes radiate energy, as he had originally imagined, it's more accurate to describe the particles themselves as tunnelling through the event horizon? Also, does anyone know what he means by "Giant black holes are stable and won't evaporate away"? Is he just saying that practically speaking the amount of time it would take black holes to evaporate is so long that we should consider them stable, as he originally predicted, or is he saying something else entirely.. that gigantic black holes don't evaporate even if left for an infinite amount of time?
  4. Jul 18, 2005 #3


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    that raised the same question in my mind---I can't give you the necessary answer---and there may be a third possibility: that he is considering a universe with finite lifespan, that eventually collapses, so that a big enough black hole would not have time enough to evaporate.

    I find this paper baffling and frustrating and hope someone will show up who can clarify. Otherwise i think I will just forget about it (instead of continuing to be baffled)
  5. Jul 19, 2005 #4


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    much of this new Hawking paper is similar to his talk at the GR17 conference in July 2004, although there is some new content and it helps to see some references.
    John Baez reported from Dublin GR17 in his "this week's finds" column #207, so I will get the link to that.


    Baez reflected some on the talk and the reception it got from other physicists, as I recall. He also included the complete text of the talk, which NY Times reporter Dennis Overbye seems to have webulized.
    webulated? allowed to percolate out into the web-wide world.
    Last edited: Jul 19, 2005
  6. Jul 20, 2005 #5
    Marcus, the post:Lets read between the path-integral lines? straight away I see Hawking has confirmed my 'past' question of Blackhole 'Time-dependant' reasoning. Take the last sentence in the paper:I gave John an encyclopedia of baseball, but maybe I should just have given him the ashes.

    Is this really cricket? ..or is this fact that one can derive an integral of information entering a Blackhole, but cannot derieve the same integral of the information that 'rebounds' , scatters back out?

    What this really means is that if you throw an English Encyclopedia into a Blackhole, the only thing you can guarantee, is that an English Encyclopedia will never emerge, the particles that went into the construction of the pre-blackhole Encyclopedia, can never re-construct it , the particles that scatter from a certain blackhole horizon, are 'Time-Stamped', and are thus 'younger', 'older' but never the same 'age' as those that entered the Blackhole.

    Into the fire, Out of the ashes ?..you will never get the particles of the Encyclopedia back scattered, but you could theoretically Get the Particles of the Trees that went into 'before' the Paper was created, and thus only re-create an Encyclopedia that has 'no-written-words', a sort of Encyclopedia Template!..not an 'Historical' Documentation of Factual Writings!

    "The information loss corresponds to the classical relaxation of black holes according to the no hair theorem. One can not ask when the information gets out of a black hole because that would require the use of a semi-classical metric which has already lost the information"

    The Time-Dependant paths of Galactic Blackholes have no Branching off to 'other-universes' . "If you jump into a black hole, your mass energy will
    be returned to our universe but in a mangled form which contains the information about what you were like but in a state where it can not be easily recognized. It is like burning an encyclopedia. Information is not lost, if one keeps the smoke and the ashes. But it is difficult to read."

    This paper contravines one of the most rigourous time-evolution paramiters of Big-Bang theory, if one rewinds our Galaxy, with the theorized Blackhole at its Core, then our Galaxy has a Time-Stamp 'information' that is Unique to our Galaxy. It is evident that all Galaxies that have theorized Blackhole's at their core's, are thus themselves 'Unique'.

    The only way in GR to travel to another 'Time-PAST/FUTURE', is to remain inside you Galaxy, wait for another Galaxy to head your way as a merging process, then to 'jump-ship' when the intertwined Galaxies exchange information during the collision process.

    You cannot leave our Galaxy and travel to Andromeda, which observationally is within our 'information-time' locally, but yet according to Hawking, if one waits for the 'future' collision of Andromeda and Milkyway, then this collision harbours a good chance of 'Time-Travel'..infact the ONLY chance.

    Involved my over-reactive post in your library thread, so if one reads the current Hawking paper, then one can only draw the conclusions that the 'topology' at infinity boundary, will cause the boundary to have a 'far-off' Reflective Index correlated to the Blackhole Thermal 'local' spectrum.

    This is the crux of a lot of confusing Blackhole 'near' and 'far-off' effects for observation and interacting around Blackholes. What is clear is that there is an underlying process for Particles that are 'infalling' around a Blackhole, and are back-scattered, not locally but at a far off location, at the Cosmic Horizon.

    Trust me, what Hawking is trying to get to grips with, is that it has been known for some time that Penrose 'conformal techniques', produces 'information' not appearing locally at the Blackhole horizon, if one is an observer between the observevation-point, and the source-point.

    So in a nutshell, if you look at a known Blackhole source, say at the Galactic core, send in particles from 'your' location into the core, you should recieve a signal back, telling you that the particles have Anhilated, or evaporated thermally?..and record this event thus.

    Hawking uses the Path Integral formilism to preserve this information, to recieve confirmation?..initially some years ago it was thought that information 'Bounced' or re-bounded via compact trapped shell horizons, but Quantum Tunneling. His reference to baby universe's branching off is where this information was deemed to have travelled to.

    Now the really interesting thing that Hawkings paper is implying, and it may be that he has overlooked this, is that the Quantum Tunneling from within the Blackhole, only, I stress again 'ONLY' appears as a Reflective Index on the far off Horizon!..so in order to gain knowlwdge of Blackholes in your vicinity, any input you send in, would appear 'behind-you'. So you would be facing the wrong way, if you send particles into a blackhole, you could wait for an eternity, if you look in the same direction, the scattering signal would not manifest locally, one has to look in the opposite direction.

    Whilst this seems quite strange, actually from a Quantum 'tunnelling' Observation point of view it, is not really that strange, its an 'Hidden Variable' :rolleyes: , anyway, the evidence of this effect can be seen in a large number of Cosmological paradoxe's, non more than the Holographic Projection Effect detailed by G T Hooft.

    Hawking states this:There is a problem describing what happens because strictly speaking, the only observables in quantum gravity are
    the values of the field at infinity. One can not define the field at some point in the middle because there is quantum uncertainty in where the measurement is done.

    What he is neglecting, and I know I am correct here, is that the information an observer see's inside the Universe, is allways heading away from him (GR) locally, but at far off cosmological distances, it is Heading towards him, in the form of Inflation..Accelerated Expansion..and now The Luminocity Function has recently been found to have a Correlated Function, different at far away locations, when compared to Local Effects.

    Again:A semi-classical metric is in a mixed state already. The information loss corresponds to the classical relaxation of black holes according to the no hair theorem. One can not ask when the information gets out of a black hole because that would require the use of a semi-classical metric which has already lost the information. This tends to be a cop out against:The Entropy Input at the Universe's Horizon(wavefunction of Universe), and one can ask : Can information be lost locally, and gained at another location?,,if so what comes first the 'inside' Boundary or the 'Outside' boundary..its a question about Time?
  7. Jul 20, 2005 #6


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Hi spin_network and anybody else. there's more discussion over at the thread hans started about this same paper


    Basically Hawking loses me at the very start when he says he's going to do this in the context of his own personal unpopular theory of quantum gravity, "Euclidean path integral".
    Nobody much has wanted to pursue that approach to QG since sometime in the 1990s because it didnt pan out in the 1980s.

    It seens like Loll is finally making path integral QG work now by introducing a Lorentzian (instead of Euclidean) version.

    but hawking makes this rather eccentric pronouncement at the beginning that he will do his reasoning in the context of Euclidean P.I. because it
    "is the only sane way to do quantum gravity nonperturbatively"

    it sounds silly to me. I will wait to hear what others say though.
    I guess the best plan is to discuss this paper go to Hans de Vries
    "Hawking preprint" thread
    Last edited: Jul 20, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook