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Radical new cosmic model (Barrau Linsefors one-up Penrose)

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  1. Jun 18, 2014 #1

    marcus

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    ==from conclusions section on page 4 of Barrau Linsefors June paper==
    V. REBIRTH OF THE UNIVERSE AND TESTS OF THE MODEL
    In the far future, huge patches of our universe, with radii larger than the Hubble scale, will be completely empty. They will be pure dS spaces. If the model suggested in this work is correct, these empty spaces will give birth to new universe through the process of spontaneous symmetry breaking described above. When this leads to a contraction, which will inevitably occur, a new universe filled with radiation – and then matter – will appear.

    It should be emphasized that time always exists in this model in the sense of a light cone structure. The quantum breaking of the classical symmetry just selects a preferred slicing that corresponds to either a contracting or an expanding solution. We are not suggesting that time is emergent, or that it changes direction.

    Is it possible to test this scenario? First, it should be pointed out that no new “theory” is suggested here. We just link together all the consequences of already accepted or assumed models. The two main ingredients of our proposal are the bounce and the cosmological constant. Both can be tested and, in principle, if both are validated the suggest scenario comes somehow automatically.

    As far as the bounce in concerned, different observational footprints can be expected, even beyond LQC (see, e.g., [28] and references therein). As far as the interpretation of the acceleration of the Universe by a cosmological constant (or not) is concerned, many experiments are of course devoted to this issue, in particular the LSST telescope and the Euclid satellite.

    One step further, this specific scenario of filling the Universe with dS radiation (beyond the bounce and cosmological constant ingredients) can be falsified. Let us consider an example. If our suggestion is correct, one does not expect complex structures in the contracting branch, there is no way to form stars and subsequent black holes. However coalescence of black holes in the contracting phase have been shown to be detectable [29]. If such circles were to be detected, this would disprove our proposal.
    ...
    This simple model builds on the specific properties of dS spaces and bouncing cosmologies to suggest an original new scenario which does not require any assumption about the initial matter content of the Universe. Everything happens because of the cosmological constant and quantum effects. Particle physics enters the game for the details of the dynamics around the bounce, but the main picture just relies on ”vacuum” properties. There are no divergences, no origin of time, and no problem of initial values for the content of the Universe.
    ==endquote==

    http://arxiv.org/abs/1406.3706
    Our Universe from the cosmological constant
    Aurelien Barrau, Linda Linsefors
    (Submitted on 14 Jun 2014)
    In this article, we consider a bouncing Universe, as described for example by Loop Quantum Cosmology. If the current acceleration is due to a true cosmological constant, this constant is naturally conserved through the bounce and the Universe should also be in a (contracting) de Sitter phase in the remote past. We investigate here the possibility that the de Sitter temperature in the contracting branch fills the Universe with radiation and causes the bounce and the subsequent inflation and reheating. We also consider the possibility that this gives rise to a cyclic model of the Universe and suggest some possible tests.
    5 pages

    ==my comment, merely to clarify one of their points==
    MATTER and/or radiation by its very existence breaks the symmetry of deSitter geometry by selecting a preferred slicing. We already see this sort of thing with the CMB ancient light which selects a preferred foliation in the standard Friedman cosmic model. The "symmetry breaking" here is a GR symmetry breaking rather than the particle physics kind. One is breaking the diffeo invariance/general covariance.
     
    Last edited: Jun 18, 2014
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  3. Jun 19, 2014 #2

    Simon Bridge

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    My immediate thought is "how do they avoid 'Universes all the way back'?"
    Or did I misunderstand?
     
  4. Jun 19, 2014 #3

    marcus

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    I think you understood correctly, Simon! I don't think they answer the existential question, any more than Penrose does, or Steinhardt with his cyclic or ekpyrotic. I could be mistaken but it seems to me that nobody attempts to answer the question "why does existence exist?"

    I like the "Universes all the way back" way of putting it, like "Elephants all the way down" :biggrin:
     
    Last edited: Jun 19, 2014
  5. Jun 19, 2014 #4

    Simon Bridge

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    Or turtles all the way down... yeah.

    It is a nice extension to Susskind's observations about how we seem to be in a special epoch in the evolution of the Universe though - where there is stuff to see. Also sidles nicely along with the fecund universes and avoids improbability of life arguments since there is a mechanism for multiple die rolls.

    The "beginning of time" stuff does have the advantage of not needing an infinite stack of elephants

    I think the standout feature is the claim to falsifiability.
     
  6. Jun 19, 2014 #5
    ... Thanks for sharing Marcus. Glad to have read something coming from bounce scenario. Bounce has a reputation of the 'G of the gap' in science literature (Penrose aeons-quantum goemetry- oscilalating scenario-non-singular bounce) and always has a nag to 'field'. I just wonder if our universe can really recycle in a sense.
     
  7. Jun 19, 2014 #6

    MTd2

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    Not like that. That is the multiverse idea, where the constants of everything in nature change in each path of a forever inflationary universe.

    Here, we have that at some point in time, everything gets so distant from each other and all things decay, that only radiation remains. Now, remember that one of the reasons for proposing inflation was too smooth out the universe. So, this new patch behaves as an smoothing out of a new inflation of a new cycle of the universe.

    The first case is like a crazy fractal tree. The second case is like erasing the old universe by heat death, where the new universe don't see the death of the old universe, but only as inflation that follows a big bang.
     
  8. Oct 4, 2014 #7

    marcus

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    Last edited: Oct 4, 2014
  9. Oct 4, 2014 #8

    MTd2

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    You said it. Break of diffeo!
     
  10. Oct 4, 2014 #9

    marcus

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    Just as a reminder to anyone reading, the symmetry breaking described here is not a problem. Solutions to the Einstein equation can have a preferred perspective/time slicing in which the contents of the universe are seen to be stationary. The theory itself has full symmetry, which individual solutions are not required to have. E.g. the standard cosmic model, the Friedman universe cosmologists use, has the criterion of CMB rest---being at rest relative to the ancient light.

    To make that clear, in case anyone missed the main point, I'll quote from the original post. Note the phrase in the abstract "fills the Universe with radiation".
    ===quote from the top===
    http://arxiv.org/abs/1406.3706
    Our Universe from the cosmological constant
    Aurelien Barrau, Linda Linsefors
    (Submitted on 14 Jun 2014)
    In this article, we consider a bouncing Universe, as described for example by Loop Quantum Cosmology. If the current acceleration is due to a true cosmological constant, this constant is naturally conserved through the bounce and the Universe should also be in a (contracting) de Sitter phase in the remote past. We investigate here the possibility that the de Sitter temperature in the contracting branch fills the Universe with radiation and causes the bounce and the subsequent inflation and reheating. We also consider the possibility that this gives rise to a cyclic model of the Universe and suggest some possible tests.
    5 pages

    ...MATTER and/or radiation by its very existence breaks the symmetry of deSitter geometry by selecting a preferred slicing. We already see this sort of thing with the CMB ancient light which selects a preferred foliation in the standard Friedman cosmic model. The "symmetry breaking" here is a GR symmetry breaking rather than the particle physics kind. One is breaking the diffeo invariance/general covariance.
    ==endquote==
     
    Last edited: Oct 4, 2014
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