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A Definition of [itex]\sigma_8[/itex]

  1. Aug 25, 2017 #1
    Hi everyone,
    apologies if this question has been asked already. My search didn't give any results.

    Can anyone tell me the definition of [itex]\sigma_8[/itex] in terms of the power spectrum? A reference where I could find it is perfect too!

    Thanks a lot
     
  2. jcsd
  3. Aug 25, 2017 #2

    George Jones

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  4. Aug 25, 2017 #3
    Thanks a lot! Does that simply mean [itex]\sigma_8=\mathcal{P}(k=1/8 \,h/Mpc)[/itex]? Where [itex]\mathcal{P}[/itex] is the power spectrum.
     
  5. Aug 25, 2017 #4

    George Jones

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    I have attached one page from the second edition of "Fundamentals of Cosmology" by James Rich. Take ##r=8## in equation (7.32).
     

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  6. Aug 25, 2017 #5

    kimbyd

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    And just to clarify, this is the matter power spectrum. There are other power spectrums that are used in cosmology.
     
  7. Aug 26, 2017 #6
    All clear now! Thank you so much everyone!
     
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