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I Why the GUT epoch ended at ~10^-36 s ?

  1. Jul 26, 2017 #1
    I read that the GUT epoch is estimated to have ended at around 10-36 s, but I can't find any proof or derivation for this. Anyone knows ?
     
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  3. Jul 26, 2017 #2

    PeterDonis

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    Where? Please give a specific reference.
     
  4. Jul 26, 2017 #3
    Sure :
    The list goes on, but I didn't find a source with a proof or at least some qualitative justification for this.

    <Moderator's note: Link changed due to possible copyright violation>
     
    Last edited by a moderator: Jul 27, 2017
  5. Jul 26, 2017 #4

    George Jones

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    Try using (3.2.68) of Daniel Baumann's (Cambridge) excellent cosmology lecture notes
    http://www.damtp.cam.ac.uk/user/db275/Cosmology/Lectures.pdf
    to find ##t_\rm{GUT}## for ##T_\rm{GUT} \approx 10^{15} ~\rm{GeV}## and ##g_* \approx 10##.

    Within one or two orders of magnitude, it is ubiquitous in the literature, e.g., on page 190 of the second edition of the often-used text "Introduction to Cosmology" by Barbara Ryden.
     
  6. Jul 26, 2017 #5
    Seems to be it, thank you ! I get, using ##T_\rm{GUT} \approx 10^{15} ~\rm{GeV} = 10^{18} MeV## :

    ##t \approx \frac{9}{4\sqrt{10}T^2} \approx 7 \times 10^{-37} s##, which is close enough.

    One thing I'm not sure about though is why the choice of ##g_* \approx 10## degrees of freedom ?
     
  7. Jul 26, 2017 #6

    George Jones

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    I have a few books that give expressions equivalent to Baumann's (3.2.68), but, as far as I can see, I have only one book that explicitly uses this expression to estimate ##t_\rm{GUT}##, "Introduction to General Relativity" by Lewis Ryder.

    We are only looking at order of magnitude stuff. Even so, this is probably too small by an order of magnitude or so, since ##T_\rm{GUT} \approx 10^{15} ~\rm{GeV} ## or ##T_\rm{GUT} \approx 10^{16} ~\rm{GeV}## for the Minimal Supersymmetric Standard Model (MSSM), which has loads of particle species.
     
  8. Jul 27, 2017 #7
    Right, ##g_*## doesn't change much the estimation anyway. I was just curious of what those degrees mean, but doesn't really matter.

    Thanks, I got the book and found it indeed, on page 384. I'll keep those two references.
     
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