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About Dark Matter

  1. Oct 1, 2015 #1

    wolram

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    http://w.astro.berkeley.edu/~mwhite/darkmatter/essay.html, A good overview of dark matter.
    Quote.

    The density of matter in the solar neighborhood is measured by sampling a uniform population of luminous stars that extends well above the disk of the galaxy. The average velocities of the stars and the vertical distances they traverse above the disk provide a measure of the gravitational restoring force that keeps these stars in the disk. From the strength of this force, one can deduce the total density of matter that exerts this gravitational pull. Comparing this density with actual counts of stars, one finds that the number of observed stars falls short, by perhaps as much as a factor of 2, of the number needed to account for this density. This is the first hint of any dark matter, and it is present in the vicinity of the sun. It should be noted that the amount of such a shortfall in the disk matter is controversial.
     
    Last edited: Oct 1, 2015
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  3. Oct 1, 2015 #2

    wolram

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    From http://arxiv.org/pdf/0811.3347v1.pdf
    With the standard active neutrinos being too light, such a dark matter candidate cannot be found within the Standard Model. Thus, one can consider the existence of dark matter as evidence for new physics

    In this review we focus on dark matter candidates that appear once the Standard Model is extended with the Peccei–Quinn (PQ) symmetry and/or supersymmetry (SUSY): the axion, the lightest neutralino, the gravitino, and the axino. These hypothetical particles are particularly well motivated:

    Is new physics required for Dark Matter?

    http://web.mit.edu/redingtn/www/netadv/Xdarkmatte.html Dark Matter library.
     
    Last edited: Oct 1, 2015
  4. Oct 1, 2015 #3
    Its been proposed dark matter may arise from quantum gravity.
     
  5. Oct 1, 2015 #4

    wolram

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  6. Oct 1, 2015 #5

    Chronos

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    It is a safe bet DM requires physics beyond the standard model. For discussion see http://arxiv.org/abs/0704.2276, Physics Beyond the Standard Model and Dark Matter.
     
  7. Oct 2, 2015 #6

    wolram

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    Cronos from your post

    I will discuss strong evidence for non-baryonic dark matter and dark matter later in my lectures. Density fluctuation is covered in many other lectures in this school by Lev Kofman, Sabino Matarrese, Yannick Mellier, Simon Prunet, and Romain Teyssier. Neutrino mass is discussed by Sergio Pastor, and baryon asymmetry by Jim Cline. The bottom line is simple: we already know that there must be physics beyond the standard model. However, we don’t necessarily know the energy (or distance) scale for this new physics, nor what form it takes. One conservative approach is to try to accommodate all of these established empirical facts into the standard model with minimum particle content: The New Minimal Standard Model [2]. I will discuss some aspects of the model later. But theoretical arguments suggest the true model be much bigger, richer, and more interesting.

    Why is it evident that new physics is needed? What particle is most favored and why?
     
  8. Oct 2, 2015 #7

    wolram

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    Last edited: Oct 2, 2015
  9. Oct 2, 2015 #8

    Chronos

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