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Dark energy proves.

  1. Dec 19, 2008 #1
    Hi, I have another doubt :biggrin:

    In addition to the Supernovae Ia, which more brought us to think the expansion was accelerating? And is there any difference between dark energy and quintessence? Because I've heard that dark energy is like vacuum energy (cosmological constant) and quintessence... I don't really know :tongue:

    Thanks for all, since I'm in Physics Forums i've learnt lots of healpful thigs!
     
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  3. Dec 19, 2008 #2

    marcus

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    There are 3 or 4 independent sets of data that support the dark energy interpretation. Here's a thread on a recent one
    https://www.physicsforums.com/showthread.php?t=280456

    It's a thread I set up in Cosmo forum in case anyone wanted to discuss the latest confirmation of dark energy----by counting clusters of galaxies of various masses, at near and medium distance (low and medium redshift).

    A good way to answer your question is to go here,
    http://blogs.discovermagazine.com/cosmicvariance/2008/12/16/dark-energy-no-longer-a-surprise/
    and look at the figure of overlapping intersecting ovals. These show confidence bounds on two important Cosmology parameters----dark energy fraction (around 0.74) and dark energy equationofstate (around -1)

    The four intersecting colored ovals are

    Supernovae---yellow oval
    WMAP cosmic microwave background data----blue oval
    BAO baryon acoustic oscillation data-----green oval
    cluster mass counts (the latest stuff)-----pink oval

    combined---red blob where they intersect

    You will see how each oval helps to narrow down the ranges on these two parameters. Those two numbers go into the cosmo models that give us estimates of other kinds of things that we can compare with observation.

    In case anyone is unfamiliar. There is a welldefined energy density of 0.85 nanojoules per cubic meter, called critical density. The number 0.74 means that dark energy is estimated to be 74 percent of critical. That gives us a figure for it in nanojoules per cubic meter, if we want.
    The equationofstate is just the ratio of the DE pressure to the DE energy density. As more data accumulates it seems increasingly likely that this ratio is -1.
     
    Last edited: Dec 19, 2008
  4. Dec 19, 2008 #3

    George Jones

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    Unlike vacuum energy, quintessence is a new field that could vary in space and time. See

    https://www.physicsforums.com/showthread.php?p=1327486.
     
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