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Might inflationary multiverses bumping cause anisotropy?

  1. Nov 28, 2011 #1
    Could two Inflationary universes bumping up against one another result in the anisotropy seen in the Cosmic background radiation and thus ultimately lead to galaxy formation? And could the signature for such an event be measured?
    It seems two "big bang" universes arising near one another might gently interact before the space between them expands fast enough to separate them. Could this, hopefully gentle, interaction be responsible for the eventual aggregation of matter into stars? If so, such a local interaction like two balloons bumping should leave some measurable "fingerprint" in both.

    Eagerly awaiting enlightenment,

  2. jcsd
  3. Nov 28, 2011 #2


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    From a totally speculative premise, you can make any conclusion that you like. No one can prove you wrong.
  4. Nov 28, 2011 #3
    Would not such an encounter leave a trace that would fit with a mathematical model consistent with cosmological models? And could such an interaction not be seen in the CMBR? New observations are so sensitive it seems any predicted ripples or perterbations might be seen.
  5. Nov 28, 2011 #4


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    A guy named Matthew Johnson from the Perimeter Institute for Theoretical Physics recently came to give a talk about this in my department. The short answer seems to be, "yes, people think that bubble collisions would leave observational signatures in the CMB." Some searching revealed that this was probably the paper he made reference to in his talk:


    and also this, its companion:


    For the sake of clarity, he's talking about eternal inflation, a scenario in which our observable universe is a sort of non-inflating "pocket universe" or "bubble" that has separated out of an eternally inflating background, and the theory predicts that many such bubbles or "pocket universes" would exist, each perhaps with different physical constants of nature.

    Skepticism is always good, but it turns out the OP was not totally out to lunch here. :wink:
    Last edited: Nov 28, 2011
  6. Nov 28, 2011 #5
    Two inflationary universes bumping against either other would result in anisotropy, but not the anisotropy we see. If you have only two universes, then you'd see massive directional differences which is something we *don't* see.

    Nope. Inflation happens a millions of years before galaxy formation. By the time galaxies form, then the universe has settled down. Now you could see a signature in the distribution of galaxies, but this would be some large directional component that we don't see.

    Also galaxy formation is a huge unknown, but by the time it happens, the universe is cool enough so that there is little room for "weird physics."

    Yes it could. We haven't seen it so, there are limits on what can happen.

    Two universe colliding wouldn't be gentle.

    No it couldn't. When stars form, we are in "non-weird" physics at which point, we can rule out weird things happening like colliding universes. (Also, colliding *galaxies* are important in star formation).

    Yes. And we don't see it (people have looked).

    Also you mention two balloons. If you have a large number of balloons things are different......
  7. Nov 29, 2011 #6


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    The interaction isn't quite so gentle, but yes, it would leave a distinct signature on the CMB if it happened late enough in inflation. Basically, such collisions produce ring-like patterns on the CMB. Some statistical tests of WMAP data show that maybe there is such a pattern, but the detection isn't strong enough to say for sure:

    Edit: Oh, and by the way, it is certainly the case that most of the fluctuations we see on the CMB are not due to any sort of collision.
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