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I How many e folds?

  1. May 5, 2017 #1
    Is there any way to constrain with data how many e folds went on during inflation ( or during our era of inflation in the case of eternal inflation)?
     
  2. jcsd
  3. May 5, 2017 #2

    bapowell

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    There's no way to collect data on inflation that occurred prior to the last 60 e-folds or so, since such length scales are outside today's cosmological horizon.
     
  4. May 5, 2017 #3

    kimbyd

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    Sort of. It depends upon the inflation model.

    Basically, for a given inflation model, different numbers of e-folds of inflation result in different spectral tilt (that is, the power spectrum's shape is slightly altered by the number of e-folds).

    However, this can't be done in general. This depends upon a very specific model of inflation. Other models, with other dynamics, will show very different numbers in terms of the number of e-folds. I'm not currently aware of any methodology to measure the number of e-folds directly.
     
  5. May 10, 2017 #4

    Chronos

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    Most theorists would agree no less than 50 e-folds are necessary, many prefer 60.
     
  6. May 10, 2017 #5

    bapowell

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    It's not so much a matter of it being "necessary"...when you begin considering fewer than 50 efolds or so, you begin to have real problems satisfying the flatness and entropy constraints.
     
  7. May 11, 2017 #6

    Chronos

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    I mean necessary in the sense of modeling a universe consistent with the observational constraints you hint at.
     
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