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What impact on QG if the CMB map is revised?

  1. Aug 24, 2005 #1


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    A paper just came out this month that makes it more certain that the Cosmic Microwave map will have to be revised, with even less quadrupole and octopole power.

    On the large-angle anomalies of the microwave sky

    I opened a thread on this paper in the Astronomy section
    where it may be of general interest, since the Standard Model of cosmology will have to be made over if there is substantial revision of the CMB map. (that thread has reference to earlier papers about this by the same people, the issue has been around for a couple of years)

    what I want to know in this thread is if anyone has some idea as to the impact on quantum gravity. or even just explain some basics to us.

    According to some work by Bojowald, and by Singh (I think also perhaps Maartens, Tsujikawa) Loop Quantum Cosmology is near the point of being able to predict some LQG signature to be looked for in the CMB.
    This because the LQG big bang and the LQG inflation picture is slightly different from classical. Parampreet Singh gave a series of seminar talks on this at Penn State that is online and that I listened to the first two of.

    So if the CMB map is going to be radically revised, what happens to the LQG signature that people like Parampreet Singh were hoping to find in the CMB map? Do they have the rug pulled out from under? That depends on a lot of stuff I dont know. Does anybody else know something about this?
    If he is the only person who understands the situation, maybe we should write to Parampreet.
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  3. Aug 24, 2005 #2


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    Hi Marcus

    One of the authors is Starkman whom we discussed once previously because there was a New Scientist article about this.

    Summarising the conclusions: the authors pretty well rule out (a) systematic error and (b) statistical flukes. This leaves two possibilities:

    1) an unexpected foreground astrophysical source
    2) a cosmological explanation

    Either of these possibilities means a very serious reinterpretation of the WMAP data. Cool! This has to be the most astonishing observational conundrum around. :smile:
  4. Aug 24, 2005 #3


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    I think that the relations between the CMB and quantum gravity should not be considered too strong. As you say, there are LQG (and maybe string)-inspired models modifying the low-l CMB spectrum, but it is important to note that these 'explanations' for the observational discrepancies are not at all unique. I recall cosmologists having a rather large list of relatively mundane explanations that make the same predictions (at least to the observational precision acheivable in the forseeable future).

    As this paper points out, there are also a lot of systematic issues with measuring the lower multipole moments. It is an interesting thing to study, though. In my personal opinion, the assumptions used in the standard cosmological model are likely to have problems in this regime.
  5. Aug 24, 2005 #4


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  6. Aug 25, 2005 #5


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    Hi Kea! I vote for both possibilities. There is more than ample evidence for each. Modern cosmology is more exciting than texas holdem [except on Tuesdays].
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