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Baryon Asymmetry explained by MWI

  1. Apr 1, 2015 #1
    I did some cursory searching, and I couldn't find this idea being discussed, so I thought it would be a good idea to bring it up here.

    Is there any reason why a valid explanation for baryon asymmetry isn't that we happen to live in a world branch where there was a significant asymmetry in the creation of matter and antimatter in the early universe? If i remember correctly, the asymmetry was on the order of a part per billion, which is pretty unlikely, but it's pretty certain that the universal wavefunction had some amplitude in those states, and one of those states corresponds to our history. There are many more worlds that came from branches nearer to the average, but some fraction of worlds must be as skewed as ours or more in either direction. All of these branches decohered from us billions of years ago.

    The 'unlikeliness' can even be addressed anthropically: while more symmetrical states may be vastly more probable, only in a place such as ours can matter have a significant existence, and thus only in asymmetric places can life develop.
     
    Last edited: Apr 1, 2015
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  3. Apr 1, 2015 #2

    Avodyne

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    It seems to me that this argument is similar to the "anthropic" argument for the smallness of the cosmological constant.

    My opinion is that these arguments should be used only as a last resort. Only if we do not have any better explanation of some phenomenon (nonzero baryon asymmetry, small CC) should "an extremely unlikely event occurred" be used as explanation.

    The smallness of the CC has resisted better explanations for a long time. But we've known since Sakharov what needs to happen to generate a baryon asymmetry, and these circumstances can arise fairly easily in various beyond-the-standard-model models, so there's no need (yet) to go to "anthropic" arguments.

    Which does not mean that an "anthropic" explanation is necessarily wrong, even in cases where a better explanation is in principle available.
     
  4. Apr 2, 2015 #3

    Strilanc

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    What you have there is a curiosity-satisfying explanation, but what you want is an anticipation-controlling explanation.

    Consider that your argument works just as well if you substitute "asymmetry" for "perfect symmetry", or even wilder things like "my car turned into a giraffe". The argument is in a sense not related to the conclusion, so it ends up working for any conclusion. It proves too much, so it must be wrong or at least useless. You're trying to work in Post-BQP, when actually reality is just plain BQP.
     
  5. Apr 2, 2015 #4
    If you want to explain the magnitude of the matter-antimatter asymmetry as a random fluctuation + anthropic selection, you should probably predict that the asymmetry will be *as small as possible* consistent with the existence of life. After all small asymmetries are vastly more probable if you think that the asymmetry is just a random fluctuation. Couldn't life exist just fine in a universe with half the observed asymmetry? If the asymmetry is just a random fluctuation, wouldn't it be vastly more probable for us to find ourselves in that universe?

    For example suppose God flips 1 billion coins and creates a life-bearing universe iff there are at least 51% heads. He repeats this many times, eventually creating many life-bearing universes. Given that you find yourself in a life-bearing universe, what fraction of heads do you predict God flipped in your case? Any answer appreciably greater than the minimum of 51% is vanishingly unlikely.
     
  6. Apr 2, 2015 #5
    At the root of the anthropic argument is that there is that my consciousness randomly "inhabits" an available conscious body among those available in all versions of reality. But I'm not sure probability can be applied here. Physically, I know all of you have your own conscious states, and I have mine, yet, I can't explain why I was born me, and not someone else, or nobody. It seems random, but it doesn't seem to be physically explainable at all.
     
  7. Apr 2, 2015 #6

    bhobba

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    First I think it's necessary to be clear what the anthropic principle is. From Wikipidia its 'the philosophical consideration that observations of the physical Universe must be compatible with the conscious and sapient life that observes it.'

    There are many multiverse conceptions (eg eternal inflation) and many worlds is just one of them. MW is not a version where the Anthropic principle as defined above is applicable, nor does the multiverse idea require multiple you in each universe.

    Thanks
    Bill
     
  8. Apr 2, 2015 #7
    The problem with these probability arguments is that the universe is NOT random. It started in a state of very low entropy, which could not come up by mere chance.
     
  9. Apr 2, 2015 #8

    bhobba

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    I don't know where you got the idea the universe is not random from. Science hasn't sorted that one out yet.

    There is no claim in this thread that the universe started out by mere chance or not - again that's something science hasn't sorted out yet.

    Thanks
    Bill
     
  10. Apr 2, 2015 #9
    A key assumption to anthropic principle is that there are many random versions of the universe. But if the universe is picked from a random version, why is the entropy so low?
     
  11. Apr 2, 2015 #10

    bhobba

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    That is not the assumption of the anthropic principle. I gave it's definition before. I have zero idea where you are getting this from.

    Added Later
    All the OP is suggesting is, if the MW interpretation is true, is the reason for the asymmetry we see in Bayon number maybe we simply live in a branch where that is the case. And on further thought I may have been a bit too hasty about the anthropic principle being applicable in MW. In MW the laws of physics, physical constants etc are the same in each world. But there are undoubtedly features of our world applicable to life where a change in those isn't required.

    Thanks
    Bill
     
    Last edited: Apr 2, 2015
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