No Big Bang? Quantum equation predicts universe has no beginning

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Aug 3, 2020.

  1. paddoboy Valued Senior Member

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    27,543
    https://phys.org/news/2015-02-big-quantum-equation-universe.html

    No Big Bang? Quantum equation predicts universe has no beginning:

    The universe may have existed forever, according to a new model that applies quantum correction terms to complement Einstein's theory of general relativity. The model may also account for dark matter and dark energy, resolving multiple problems at once.

    The widely accepted age of the universe, as estimated by general relativity, is 13.8 billion years. In the beginning, everything in existence is thought to have occupied a single infinitely dense point, or singularity. Only after this point began to expand in a "Big Bang" did the universe officially begin.

    Although the Big Bang singularity arises directly and unavoidably from the mathematics of general relativity, some scientists see it as problematic because the math can explain only what happened immediately after—not at or before—the singularity.

    "The Big Bang singularity is the most serious problem of general relativity because the laws of physics appear to break down there," Ahmed Farag Ali at Benha University and the Zewail City of Science and Technology, both in Egypt, told Phys.org.

    Ali and coauthor Saurya Das at the University of Lethbridge in Alberta, Canada, have shown in a paper published in Physics Letters B that the Big Bang singularity can be resolved by their new model in which the universe has no beginning and no end.

    Old ideas revisited

    The physicists emphasize that their quantum correction terms are not applied ad hoc in an attempt to specifically eliminate the Big Bang singularity. Their work is based on ideas by the theoretical physicist David Bohm, who is also known for his contributions to the philosophy of physics. Starting in the 1950s, Bohm explored replacing classical geodesics (the shortest path between two points on a curved surface) with quantum trajectories.

    In their paper, Ali and Das applied these Bohmian trajectories to an equation developed in the 1950s by physicist Amal Kumar Raychaudhuri at Presidency University in Kolkata, India. Raychaudhuri was also Das's teacher when he was an undergraduate student of that institution in the '90s.

    Using the quantum-corrected Raychaudhuri equation, Ali and Das derived quantum-corrected Friedmann equations, which describe the expansion and evolution of universe (including the Big Bang) within the context of general relativity. Although it's not a true theory of quantum gravity, the model does contain elements from both quantum theory and general relativity. Ali and Das also expect their results to hold even if and when a full theory of quantum gravity is formulated.
    more at link.....................


    the paper:

    https://www.sciencedirect.com/science/article/pii/S0370269314009381

    Cosmology from quantum potential:

    Abstract
    It was shown recently that replacing classical geodesics with quantal (Bohmian) trajectories gives rise to a quantum corrected Raychaudhuri equation (QRE). In this article we derive the second order Friedmann equations from the QRE, and show that this also contains a couple of quantum correction terms, the first of which can be interpreted as cosmological constant (and gives a correct estimate of its observed value), while the second as a radiation term in the early universe, which gets rid of the big-bang singularity and predicts an infinite age of our universe.



     
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  3. paddoboy Valued Senior Member

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    Interesting, but of course not yet verified.
     
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  5. DaveC426913 Valued Senior Member

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    Wish they hadn't said "..thought to have occupied a single infinitely dense point, or singularity..."
     
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  7. Q-reeus Banned Valued Senior Member

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    Leaving aside whether a self-consistent theory of gravity could even allow singularities, the finding of an infinitely old one-and-only universe, according to this latest of very many quantum-corrections-to-GR schemes, runs smack into a severe problem. Like any such eternal-in-the-past theory, it requires accepting as mysterious brute fact the exquisitely fine-tuned for life set of physical constants of our universe to be a-priori uniquely given. Why? Nothing at the cosmological evolution level requires it.
    Which issue is largely why multiverse theories are so popular - our universe is merely a lucky fluke out of the countless others having randomly varying ensembles of constants that overwhelmingly could not allow for life to arise.

    The article, like many others advocating an infinitely old universe, doesn't address the issue.
     
  8. paddoboy Valued Senior Member

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    I see nothing to hard to accept that our universe is fine tuned for life...if it wasn't, we wouldn't be here to contemplate it. It's simply the way things are.
    While it doesn't address the issue, it doesn't reject it either.
    By the way, while I find the article interesting and imo worthy of further research, I'm actually not that taken with it.
     
  9. Q-reeus Banned Valued Senior Member

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    You entirely miss the point of my #4. The posited infinitely old, monotonically evolving universe model allows just one shot at cooking up a single set of physical constants. What blind physical principle selected just from among the narrow spread of fine-tuned ones permitting life? Among near endless possibilities. To that add the no less severe problem of incredibly fine tuned initial conditions including extremely low initial entropy.

    I therefore only take seriously theories that posit an endless recycling with constants varying each time (cyclic universe) maybe including Roger Penrose's CCC. Inflationary multiverse theories have the known Achilles heel of inevitably requiring an initial seed universe so not past eternal.
    There are problems with all currently proffered models but the type presented in OP is as argued here and in #4 doomed when multiple fine-tuning issues are taken into account.
     
    Last edited: Aug 4, 2020
  10. paddoboy Valued Senior Member

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    No, I'm well aware of what you meant. Again it doesn't really have me in awe. That's simply the way it is.
    I'm still preferably with Krauss, and the nothingness being defined as the quantum foam.......whether one or a million quantum fluctuations resulting in the evolution of space and time [as we know them] is nether here nor there.
    But still of course speaking speculatively, as per the OP article, which again I find interesting, while much less conclusive.
     
  11. Q-reeus Banned Valued Senior Member

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    Sigh. Anyway a rethink and realize I had neglected a poorly motivated alternative. A single universe with slowly varying constants throughout. And one of your own fairly recent cut'n'paste jobs gives some support for that being so:
    http://www.sciforums.com/threads/the-consistency-of-the-laws-of-nature-questioned.163127/
    I was the only other contributor there and viewed the evidence favorably. Not sure how it has held up since. And there is the all important matter of how much variation would/could actually exist within the largest scale. With no underlying fundamental theory such a model is really purely empirical in nature....let's just suppose that....
     
  12. paddoboy Valued Senior Member

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    OK, Ooops forgot all about E-Mailing that astronomer!!
     

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