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Might Dark Energy have anything to do with Inflation?

  1. Dec 16, 2015 #1
    Inflationary Theory postulates that the inflaton field and its associated particle were responsible for a huge space expansion in the very early universe. Now we observe again positive expansion, albeit at a very moderate rate, which we attribute to "dark energy" / "cosmological constant".
    Could it be that both have anything in common? That dark energy is a sort of very weak remnant of the inflaton process?

    Even in theory, do the inflaton expansive effect on spacetime have anything in common with the expansive effect of the cosmological constant? Or are they fundamentally different in any sense, even if both cause space to expand?

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  3. Dec 16, 2015 #2

    George Jones

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  4. Dec 16, 2015 #3
    From my understanding, inflation happened because originally space was empty and empty space has an an insane amount of outward pressure and it rapidly created more space.
  5. Dec 16, 2015 #4


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    Inflation has a potential V(Phi) that *acts* like a dark energy term in Einsteins field equations when it is very close to being flat. That is the source by which it generates near DeSitter like expansion. In principle, dark energy takes contributions from all matter species and symmetry breaking terms within the theory, not just the Inflaton. However, by assumption, during inflation, V(Phi) of the inflaton completely dominates all of the other contributions for the vacuum energy so we just focus on that term.

    Now what happens when inflation ends and there is a 'relic' but ridiculously tiny cosmological constant term that is leftover. Well, what exactly the leftover is made off is unknown. Again in principle it takes contributions from whatever is left of V(Phi), as well as every thing else. In some sense the question is not particularly interesting, b/c you could imagine that V(phi) leaves over a nonzero but constant contribution that is cancelled by some other matter field's contribution, which in turn is cancelled by yet another one and so forth. It all becomes part of the mess of understanding what the cosmological constant is.

    So in practice people just set the inflaton potential to zero after reheating and then put off the question about what the CC really *is*. Alternatively, you could take the point of view a model builder, and ask the question about what happens if V(Phi) might not exactly go to zero, but might continue to evolve with the universe in some way. This acts then very much like the model George Jones linked too.
  6. Dec 16, 2015 #5


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    This is an idea that's been batted around, but for the most part nobody has yet come up with a really compelling way this could have happened. The ideas along these lines tend to be pretty ad-hoc, so that the linking of inflation with dark energy is something that is explicitly written into the equations instead of something that we might derive from them from first principles.

    Theoretically speaking, even if inflation and dark energy were each driven by a scalar field, chances are there are a lot of different scalar fields so that there really isn't good reason to expect that they'd be produced by the same scalar field.
  7. Dec 17, 2015 #6


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  8. Dec 27, 2015 #7
    Thanks to all !
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