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Wmap and razors

  1. Apr 20, 2006 #1

    wolram

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    http://arxiv.org/abs/astro-ph/0604410

    Authors: Joao Magueijo, Rafael D. Sorkin

    Using a variety of quantitative implementations of Occam's razor we examine the low quadrupole, the ``axis of evil'' effect and other detections recently made appealing to the excellent WMAP data. We find that some razors {\it fully} demolish the much lauded claims for departures from scale-invariance. They all reduce to pathetic levels the evidence for a low quadrupole (or any other low $\ell$ cut-off), both in the first and third year WMAP releases. The ``axis of evil'' effect is the only anomaly examined here that survives the humiliations of Occam's razor, and even then in the category of ``strong'' rather than ``decisive'' evidence. Statistical considerations aside, differences between the various renditions of the datasets remain worrying.
     
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  3. Apr 20, 2006 #2

    Garth

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    In "Occam’s razor meets WMAP" the authors are trying their best to find a convincing refutation of the statistical evidence for non-Gaussality, low-l power deficiency, and the 'Axis-of-evil' in the WMAP power spectrum.

    However a prior question of the Mainstream model that might be relevant to this approach is: "What does Occam's razor do to Inflation, DM or DE?"

    From that paper:
    (emphasis mine)

    The question is exactly how 'strong' does the level of evidence have to be before people go to all "the trouble of rewriting cosmology textbooks"?

    Perhaps a lesser degree of confidence in the Mainstream model and a greater open-mindedness to other alternatives might not come amiss?

    Garth
     
    Last edited: Apr 20, 2006
  4. Apr 20, 2006 #3

    hellfire

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    Could anyone explain what this exactly means? (I have not read the paper)
     
  5. Apr 20, 2006 #4

    Garth

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    The paper uses different 'brands' of Occam's razor, using information theory.
    (Which provides the formal answer to my question above.)

    There are different criterion that can be used as razors , the Akaike Information Criterion, AIC, the Bayesian Information Criterion, BIC, and a third described in the text they call the HIC. The desire is for all three to remove the anomalies, and sometimes they do and sometimes they don't. Furthermore, they actually disagree with each other as to which is which and this removes the certainty in their result.

    My observations are these:

    1. As I have said elsewhere, in statistical significance assessment the desire not to fall into the trap of making a false positive, (e.g. requiring an improvement in I(D, T ) of at least 5 for a decisive result,) i.e. saying the anomalies are there when really they are not, inevitably increases the chance of making a false negative, saying the anomalies are not there when really they are.

    2. The paper deals with the low-l power deficiency separately from, and before, the Axis of evil, it concludes that the deficiency disappears after 'shaving' whereas the Axis does not and stubbornly remains. However these anomalies are connected, for if the AoE exists and is caused by local contamination, then the low-l power deficiency becomes even more pronounced and I would guess would actually survive the stringent 'shaving' of this analysis.

    Garth
     
    Last edited: Apr 21, 2006
  6. Apr 20, 2006 #5

    marcus

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    One of the authors is Joao Magueijo.
    (of course Bekenstein, the other, is famous for BH temperature and Bekenstein-Hawking BH entropy)

    About Magueijo, I really like his recent research. I can't evaluate this Occam WMAP paper but am enthusiastic about this one

    http://arxiv.org/abs/hep-th/0509010
    MOND habitats within the solar system
    Jacob Bekenstein, Joao Magueijo
    "MOdified Newtonian Dynamics (MOND) is an interesting alternative to dark matter in extragalactic systems. We here examine the possibility that mild or even strong MOND behavior may become evident well inside the solar system, in particular near saddle points of the total gravitational potential. Whereas in Newtonian theory tidal stresses are finite at saddle points, they are expected to diverge in MOND, and to remain distinctly large inside a sizeable oblate ellipsoid around the saddle point. We work out the MOND effects using the nonrelativistic limit of the TeVeS theory, both in the perturbative nearly Newtonian regime and in the deep MOND regime. While strong MOND behavior would be a spectacular ``backyard'' vindication of the theory, pinpointing the MOND-bubbles in the setting of the realistic solar system may be difficult. Space missions, such as the LISA Pathfinder, equipped with sensitive accelerometers, may be able to explore the larger perturbative region."

    Has anyone read "MOND habitats"?

    I tend to give this Occam paper benefit of doubt out of respect for the authors. But I fail to get any crisp message from it.
     
  7. Apr 20, 2006 #6

    hellfire

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    Thank you Garth.
     
  8. Apr 21, 2006 #7

    wolram

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    By Marcus

    we do seem to find the odd disturbed pebble, broken twig, but not so much
    as a sniff of the prey, it seems to me we desperatly need more dedicated hunters, hounds, maybe only then will we find out which of us is the yeti.
     
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