Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is the Evidence for Dark Energy Secure?

  1. Nov 9, 2007 #1

    cristo

    User Avatar
    Staff Emeritus
    Science Advisor

    This paper came out on the arxiv a few weeks ago. I've not had a chance to read it fully yet, but it looks like an interesting paper. http://arxiv.org/abs/0710.5307


    Here's an article in the news section of Nature on the same topic: Bursting Dark Energy's Bubble.
     
    Last edited: Nov 9, 2007
  2. jcsd
  3. Nov 9, 2007 #2

    Wallace

    User Avatar
    Science Advisor

    Based on the abstract ( I haven't read the full paper ) this all sounds reasonable ( and by no means original, people have been pointing all of this out since dark energy first was suggested). SN1A could be spoofing us by evolving in some as yet unknown way, and the rest of the probes may indeed by spoofed in the ways he suggests. However, there are two issues here I think. The first is one of simplicity, either we have one model that concisely describes all of what we observe with needed tweaks here and there to satisfy each observation, or we need a contrived model like the one suggested by Sarkar.

    Please nobody starting abusing poor little Ockam and his razor, we could argue till next millennium whether LCDM is 'simpler' because it has only a few parameters, or whether the kind of thing Sarkar suggests is 'simpler' because it doesn't need exotic dark energy. Lets not pretend that our subjective judgments are objective just because we mis-represent a much abused principle!

    I'd prefer to talk about something more concrete, for instance predictions. The LCDM model predicted the location of the acoustic peak in the galaxy-galaxy auto-correlation function, based on previous observations of very different things (the CMB and SN1A predominantly). We've seen marginal evidence for this peak in existing galaxy surveys and will hopefully have that confirmed soon by new surveys. Sarkar's suggestion however requires that the mechanism for the peak is totally unrelated to anything else in cosmology, and just happens to occur on the scale predicted by LCDM.

    If we want to talk about physical plausibility, it seems quite reasonable to have a 'not quite scale free' inflationary fluctuation spectrum yet we have no idea of how this physically would occur. All physically motivated theories describing the origin of the fluctuations predict that there would be no preferred scales.

    At this stage, in the end, we are not going to settle this kind of theoretical argument. With next generation BAO, SN and CMB probes however, we may either confirm LCDM (or more generally wCDM) to ridiculous precision or indeed find that the model starts to break down.
     
  4. Nov 9, 2007 #3

    Garth

    User Avatar
    Science Advisor
    Gold Member

    As already discussed here.

    As I asked in the Critique of Mainstream Cosmology thread, "Mundane checks" anyone?"

    Garth
     
    Last edited: Nov 9, 2007
  5. Nov 9, 2007 #4

    cristo

    User Avatar
    Staff Emeritus
    Science Advisor

    Ahh, sorry, I don't delve into that thread too much!
     
  6. Nov 16, 2007 #5
    black holes

    all black holes have the same mass
     
  7. Nov 16, 2007 #6

    Garth

    User Avatar
    Science Advisor
    Gold Member

    What on Earth made you say that?

    Black Holes that formed from the collapse of stellar cores and through mergers have masses from
    ~ 3 MSolar up to 108 MSolar, mini BH's may have formed in the BB as over dense areas collapsed into themselves, which may have had small masses of a few Kg upwards.

    Garth
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?