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A Variation of Hubble constant in cosmological time

  1. May 14, 2017 #1
    Is the Hubble constant decreasing over cosmological timescales?
     
  2. jcsd
  3. May 14, 2017 #2

    Bandersnatch

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  4. May 14, 2017 #3
    Why did the Hubble constant tend to infinity in the early universe?
     
  5. May 14, 2017 #4

    Bandersnatch

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    Mostly for the same reason that f(x)=1/x goes to infinity as x goes to 0. Remember that H is the proportionality factor between recessional velocities and distances: H=V/D. As the distances between receding objects decrease to 0, H goes to infinity.
    An additional effect comes from V being larger in the past, but that's secondary.
     
  6. May 14, 2017 #5
    The relation

    $$H = 1.67 \sqrt{g_{*}} \frac{T^{2}}{M_{P}}$$

    is valid during the radiation-dominated epoch. Is it valid during the inflationary epoch?
     
  7. May 15, 2017 #6

    Orodruin

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    No.
     
  8. May 15, 2017 #7
    What would be the correct relation for the Hubble parameter in the inflationary epoch?
     
  9. May 15, 2017 #8

    Orodruin

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    That would depend on the equation of state for whatever is driving inflation. If what drives inflation behaves as a cosmological constant, then the Hubble parameter would be constant during inflation.
     
  10. May 15, 2017 #9
    Would you share a review article which discusses this in more detail?
     
  11. May 15, 2017 #10

    Bandersnatch

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