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B Acoustical waves

  1. Jul 10, 2016 #1
    Acoustic waves started right after the end of inflation.
    But on the other hand I always read that the first perturbations reentered the horizon after ±50.000 years.
    These two fact I cannot cope. A reentering of perturbations at different times also don't go with the synchronicity of the waves.

    So, what is in my thinking the big flaw.
  2. jcsd
  3. Jul 10, 2016 #2


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    There was not a single accoustic wave in the early universe, but, a multitude. Baryonic acoustic oscillations have been likened to the ripples from a rock tossed into a pond. In this case the rock is more like a handful of gravel.
  4. Jul 11, 2016 #3
    What I mean: What is the connection between the acoustic waves right after inflation en the reentering of the primordial perturbations. I thought that these perturbations were the origin of the acoustic waves after they came under the influence of gravity.
  5. Jul 11, 2016 #4


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    Inflation generates perturbations across a wide range of scales, some with wavelengths that were subhorizon and some that were superhorizon after inflation ended. Those that were subhorizon manifested acoustic oscillations in the plasma, while those that were superhorizon could not oscillate until the Hubble scale grew to enclose them. Where did you read that the first perturbations enter only after 50,000 years? This is not something I've ever heard. And what do you mean by "synchronicity" of the waves? Perturbations on each scale are independently-evolving Fourier modes.
  6. Jul 11, 2016 #5
    Thank you very much, now it is clear for me. Perhaps I read the 50.000 years in the wrong context. With synchronicity I mean the integer relationship.
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