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Another dark horse in the MOND race

  1. May 14, 2006 #1

    marcus

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    Another "dark" horse in the MOND race

    I'm glad there are several competing alternatives to dark matter.
    Bekenstein's TeVeS doesnt have the field to itself.
    this appeared today:

    http://arxiv.org/abs/astro-ph/0605322
    Dark energy, MOND and sub-millimeter tests of gravity
    I. Navarro, K. Van Acoleyen
    6 pages, to appear in proceedings of the 51st Rencontres de Moriond

    "We consider modifications of General Relativity obtained by adding the logarithm of some curvature invariants to the Einstein-Hilbert action. These non-linear actions can explain the late-time acceleration of the universe giving an expansion history that differs from that of a pure cosmological constant. We show that they also modify the Newtonian potential below a fixed acceleration scale given by the late-time Hubble constant times the speed of light. This is exactly what is required in MOND, a phenomenological modification of the Newtonian potential that is capable of explaining galactic rotation curves without the need to introduce dark matter. We show that this kind of modification also predicts short distance deviations of Newton's law at the sub-mm scale and an anomalous shift in the precession of the Moon's orbit around the Earth, both effects of a size that is less than an order of magnitude below current bounds."

    Ignacio Navarro is at Cambridge----basically the same bunch as Daniele Oriti: the DAMPT

    Navarro and van Acoleyen have a bid to

    1. replace Lambda or dark energy
    2. replace dark matter and get a better fit to the rotation curves
    3. achieve rapid testability---falsification attainable with only a factor of 10 improvement in the accuracy of measurements that are already made

    sounds good. the kind of thing it is nice when theorists come up with.

    maybe it will be shot down. and maybe not. if it is not then I would guess that someone at
    Perimeter will try ways to wangle those effects using a more fundamental model of spacetime
     
    Last edited: May 14, 2006
  2. jcsd
  3. May 15, 2006 #2

    Chronos

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    It's all bells and whistles to me when I hear

    "galactic rotation curves without the need to introduce dark matter"

    I think that is fundamentally wrong. Just another short sighted explanation that conveniently ignores the preponderance of observational evidence.
     
  4. May 15, 2006 #3
    Preponderance of evidence?

    Exactly what, in your view, is this preponderance of observational evidence?

    And how is it related/not related to galactic rotation curves?

    TIA

    Jim Graber
     
  5. May 16, 2006 #4

    Chronos

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    Virial theorem, lensing and stuff like that.
     
  6. May 16, 2006 #5

    marcus

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    a second post by Navarro and friend in as many days

    http://arxiv.org/abs/gr-qc/0605091
    Long distance modifications of gravity in four dimensions
    I. Navarro, K. Van Acoleyen
    4 pages, contribution to the proceedings of the Rencontres de Moriond: Contents and Structures of the Universe, March 18-25, 2006, La Thuile


    "We discuss some general characteristics of modifications of the 4D Einstein-Hilbert action that become important for low space-time curvatures. In particular we focus on the chameleon-like behaviour of the massive gravitational degrees of freedom. Generically there is at least one extra scalar that is light on cosmic scales, but for certain models it becomes heavy close to any mass source."
     
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