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Estim. dark energy up by 3 percentage points. Any reaction?

  1. Mar 17, 2008 #1


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    When people cite the dark energy fraction informally (without errorbar) and other basic parameters they often have been saying something like

    Hubble 71
    dark energy 73%
    dark matter 23%
    baryonic 4%

    If I remember right, those are the default values used in the calculator at Ned Wright's website.

    Now in this 7 March paper by Michael Turner et al, right in the abstract up front I see

    dark energy 76%
    dark matter 20%
    baryonic 4%

    So are these new values that one should quote informally? Given the uncertainty it doesn't seem very different to say 76 instead of 73, but even though it is just a rough estimate I'd like to be aligned with the mainest of the stream---and keep the jarring dissonance to a minimum. So what numbers to you say?

    Michael Turner recent:
  2. jcsd
  3. Mar 17, 2008 #2
    Cosmology is a field I haven't studied in detail. I have only gone through it enough to know generally what cosmologist are talking about and why. For me my interest in cosmology is limited to what it can provide as a testing ground. Since I don't have any ideas (wild ass guesses) that require these parameters at the moment the ball park figure is fine with me. However, as a cosmologist, keeping abreast and using the best numbers from the best available data is important. Given the authors and the following quotes under "10.1 Take-home facts":

    I would go with these figures.
  4. Mar 17, 2008 #3


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    I don't really know where that figure has come from; I guess it depends on what data set you're using. I know the recent WMAP data had omega_lambda 0.74 on its own, and that shrunk to about 0.72 when including other data sets (namely the BAO and SN data). I've not read the Turner paper, though, so I can't really comment on that; perhaps someone else can?
  5. Mar 17, 2008 #4


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    The precise numbers still depend on which data sets are used. For instance see the series of tables http://lambda.gsfc.nasa.gov/product/map/current/parameters.cfm" that show the values obtained using WMAP5 + many different combinations of other data. The best fit values for dark energy vary between 0.7 and almost 0.8 depending on which data sets are used!

    There are a bunch of extensions to the basic LCDM such as non flat models, different dark energy models etc that are also covered.
    Last edited by a moderator: Apr 23, 2017
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