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Just an idea

  1. Jul 20, 2003 #1
    just an idea....

    i thought about something today the information of the universe has been also in the singularity of the big bang from this we can deduct that we know what was in the singularity.
    what do you think?
     
  2. jcsd
  3. Jul 20, 2003 #2
    Well, i think that you could say that everything that was in the singularity just before the Big Bang must also be somewhere in the Universe today.
     
  4. Jul 20, 2003 #3

    marcus

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    Re: just an idea....

    does the "singularity" describe a real state of the universe or is it merely a glitch in the Friedmann equations (General Relativity) model?
    since your nickname is "LQG" then I think you might know
    that quantizing spacetime geometry overrides the glitch.

    "Absence of Singularity in Loop Quantum Cosmology"

    Bojowald 2001
    http://www.arxiv.org/gr-qc/0102069

    The unquantized GR model breaks down at the time that has been arbitrarily designated as time zero---because it predicts infinite curvature. I believe there are other divergences and physically meaningless predictions, like infinite density, making the model unworkable at "time zero".

    But quantizing GR using LQG makes the curvature (now a quantum operator) remain bounded and bridges over the breakdown in the unquantized model. In the quantized model the timeline runs smoothly back without infinities of curvature or density appearing.

    So it seems that "big bang" is not a good word for the beginning of the current expansion phase of the universe. Also it does not seem appropriate to call it a "singularity" since mathematically it was not a singularity (except in the unquantized model). To call conditions at time zero a big bang or a singularity seems to involve a prejudgment or bias in favor of the 1916 unquantized version of General Relativity.

    But whatever people choose to call it this does not change the qualitative picture of a moment of extremely high temperature and extremely high concentration of energy (which may have resulted from a prior contraction phase and which initated the current expansion). So what you say about logical deduction ought to be at least partly right:

    It should be possible to deduce some things about conditions back then by observing conditions now----or by modeling conditions then to arrive at predictions about the present which could be checked against observation. So I basically agree with you.
     
  5. Jul 20, 2003 #4
    Maybe I missed a meeting, but I don't believe there's an accepted quantum interpretation of gravity in existence. So your post makes little sense, unless your promoting a fringe theory (and there's nothing wrong with that - Cosmology is in effect the science of mysteries - just pointing the difference between mainstream and otherwise) :).

    As to all the information of the universe being held within the original "singularity" - yes, certainly. However, an interesting consequence of Black Hole behaviour is the apparent destruction - else leakage - of information from the universe. This is something that Information Theory abhors and makes people nervous. Something to be addressed at some point (assuming we're not evoking White Holes here). :)
     
  6. Jul 20, 2003 #5
    Re: Re: just an idea....

    i hope ill have time to read the article you gave.
     
  7. Jul 20, 2003 #6
    a question: does the singularity of the big bang resembles the ones of black holes? if so does it posses the same information as the other singularities (i know that it might imply that from a black hole there might be created a big bang, a new universe)?
     
  8. Jul 20, 2003 #7

    marcus

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    Quantizing general relativity is a long-standing project in mainstream physics going back to work by Dirac in the 1940s and John Archibald Wheeler in the 1960s (his book Geometrodynamics was published in 1962). If memory serves he was at the Princeton Institute for Advanced Study---not exactly a "fringe" institution.

    The most significant advance since the Wheeler-DeWitt equations is IMHO the new variables for GR developed by Abhay Ashtekar (1986). Around 1993, in order to get Ashtekar to join the Physics Department, Penn State set up the Center for Gravitational Physics and Geometry (CGPG) and offered him the directorship.
    This does not look especially "fringe" to me.

    Have a look at Ashtekar's article of Feb 2002
    http://www.arxiv.org/math-ph/0202008
    "Quantum Geometry in Action..."

    It gives an overview and is not especially technical. There are a bunch of more recent papers about the removal of the time zero singularity by quantizing General Relativity---by Ashtekar and others. This is definitely mainstream and the issue of not encouraging bias or prejudice is a sensitive one BECAUSE the work is quite recent and not yet widely understood or established.

    What you say about a quantum spacetime model not being "generally accepted" is certainly right----there is a shift in progress and that needs to be taken account of----but your suggestion that the work of Ashtekar and others is "fringe" is in my view rather wide of the mark.

    Bojowald is another of the group at Penn State CGPG---I gave a link to a 2001 article by him in the previous post. Bojowald and Ashtekar co-authored a more recent paper about the removal of the time zero singularity by quantizing the GR model.

    http://www.arxiv.org/gr-qc/0304074

    It also has a useful non-technical overview of current work in quantum cosmology/general relativity and is dated June 2003,
    if you happen to be interested.
     
  9. Jul 20, 2003 #8
    Finge probably sounded like an unfortunate use of the term. However, there's nothing necessarily demeaning about being on the "fringe" of mainstream scientific theories. Or perhaps I've trying to save grace by avoiding addressing the populer use of the term. :)

    As for the article in question - I'll leave that for peer review. :)

    There are certainly a lot of interesting theories out there that seek to reconcile the various aspects of GR and QT. Until any single generally accepted theoretical framework arises from that, then there really is no basis for claiming that gravity has been successfully quantised.
     
  10. Jul 20, 2003 #9

    marcus

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    Not unfortunate, just inaccurate when applied to the current effort to quantize general relativity.

    I don't imagine that, as you apply it, the word is at all pejorative. I dont presume to understand your use of words, however inappropriate. Quantizing general relativity is a long-standing mainstream focus of research going back to Dirac and Wheeler---major people have thought it important and contributed to its progress over the years: Ashtekar most recently.

    If you are interested in peer-reviewed publications the main journal relevant to quantizing general relativity is "Classical and Quantum Gravity". However the article in question (by Bojowald)
    was published in "Physical Review Letters" vol 86, pp 5227-5230 (2001). Since then a number of papers about the removal of the classical singularity at time zero have appeared by a half dozen or so other researchers as well as those I've mentioned, some as co-authors. The past couple of years have seen a lot of work on this in several parts of the world. I interpret this as a significant peer response. :wink:

    I am not sure who you are telling this to or why you are saying it. There would not be so much work on it going on if general relativity had already been satisfactorily and finally quantized. The fact is that there are very interesting open questions and topics for research in the field!

    No one has declared the research finished as yet, and since things are in flux, I would urge we not use biased language suggesting that there is a singularity at time zero except as an artifact of the classical model.

    The classical EQUATIONS (already more than 80 years old) fail at time zero and do not go back farther. But I see no reason to suppose that nature itself fails at time zero and does not go back before that. Particularly since the models under development do evolve smoothly back to before the classical time zero.
    It would seem that the burden is on you to supply evidence if you presume that the timeline ends in a kind of precipice at time zero.
     
    Last edited: Jul 20, 2003
  11. Jul 20, 2003 #10

    marcus

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    Thanks for even thinking of it. Time for reading is always at a premium, so I've been trying to decide what article about this is the quickest to read and accessible to the most people. Instead of the one by Bojowald that I first mentioned I'd recommend a well-written general audience article by Abhay Ashtekar:

    http://www.arxiv.org/math-ph/0202008
    "Quantum Geometry in Action, Big Bang and Black Holes"

    In some of the other articles one can get bogged down in formulas, but this one states the main developments in a real direct way and gives a some helpful mental pictures.
     
  12. Jul 20, 2003 #11

    marcus

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    The next post, by ranyart, makes me think what I posted here was too wordy, so I will scrap all but the essential part.

    A. Ringwald of DESY is one of the people predicting a cosmic NEUTRINO background of 1.9 kelvin. Neutrinos from the sun and supernovas and other high energy sources have been detected, but these low energy ones have not been detected yet.
    The suspected neutrinos are relics from the first second of expansion and they have lost most of their original energy (around 1 MeV) due to the expansion of space. Ringwald estimates the energies are now around 10-4 eV.
    He calculates that there are some 56 of these ancient neutrinos in each cubic centimeter of space.

    I dont know who originally broached this "cosmic neutrino background" subject---only that Ringwald has a clear readable
    article about it (the first link I gave didn't work, this one may work better)

    "How to Detect the Cosmic Neutrino Background"



    http://arxiv.org/abs/hep-ph/0301157


    If these neutrinos could be detected it would strongly corroborate to the expansion picture of the universe. Another long-shot prediction (analogous to the CMB) confirmed. As
    something I read recently about this said, it would open another window for observing the big bang.
     
    Last edited: Jul 21, 2003
  13. Jul 21, 2003 #12
    There seems to be a conflict with the info you are providing, the link for Ringwald is by some other person?

    There are also other links you could provide, showing at least the Ekpryotic/Cycle model, as this predicts a 'bounce' that is percieved to be pre-inflation for some models ie Guth/Linde. Although there has been good recent papers by both Linde and Guth, there appears to be a concensus of opinion that the Fluctuations of Temperature ie,from Hot to Cold and Cold To hot are quite important to present day detections.

    http://arxiv.org/PS_cache/hep-th/pdf/0307/0307170.pdf

    What this relates to is there are models in which the Universe can evolve from a Cold Big-Crunch, just as likely as the evolution form a Hot Big-Bang, infact the consensus is there would be very two colliding Universes, one that is collapsing or de-flating, connected to another Universe that is Expanding.

    Assigning the correct temperature with expansion models and with Contracting models is where different models start/end from.

    The CMB is presumed to be the intersection (Brane) of collapse and Expansion, thus our current Universe may be at the 'pre-crunch' phase, having evolved from a Hot Big-Bang phase.

    This is of course reliant on the matter density and Vacuum density, if matter is contracting(density increase)then non-matter density(Vacuum)would be increasing(Negative Matter density de-creasing)

    Below is another recent paper fro you to read, presuming you do actually read the links you post?

    http://arxiv.org/abs/hep-th/0306109
     
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