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Is Supersymmetry still viable in cosmology?

  1. Sep 5, 2014 #1

    wolram

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    Is Supersymmetry still viable in cosmology, given that so far no supersymmetric particles have been found.

    From Wiki.

    SUSY is often criticized in that its greatest strength and weakness is that it is not falsifiable, because its breaking mechanism and the minimum mass above which it is restored are unknown.[citation needed] This minimum mass can be pushed upwards to arbitrarily large values, without disproving the symmetry, and a non-falsifiable theory is generally considered unscientific. However, many theoretical physicists continue to focus on supersymmetry because of its usefulness as a tool in quantum field theory, its interesting mathematical properties, and the possibility that extremely high energy physics (as in around the time of the big bang) are described by supersymmetric theories.
     
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  3. Sep 6, 2014 #2

    wolram

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    http://www.math.columbia.edu/~woit/wordpress/?p=6392

    Tom Siegfried, last heard from telling us that Belief in multiverse requires exceptional vision, now has two new pieces at Science News (here and here) arguing that the failure of the LHC to see SUSY is not really a big problem for SUSY proponents. You see, it’s only a problem if you believe physics theories should be simple and if you believe in naturalness. According to Siegfried, what the LHC is telling us is that you just have to give up on one of these, with your choices now:

    Give up on simplicity. Just announce that SUSY is fine and solves the naturalness problem, but we’re not seeing it because it’s not the MSSM (which adds more than a hundred parameters), but something really, really complicated, so complicated that it manages to show up in such a way that the LHC experiments can’t see any evidence of it. Believe this, and you can still believe in SUSY, no need to face the tragedy of an idea you’ve done so much to promote getting killed by heartless experimentalists.
    Give up on naturalness and have the exceptional vision to believe in the multiverse. Then you can fine-tune your SUSY particles up to very high energies and make them unobservable. Again, you’re free to keep believing in SUSY, writing articles and books about it, etc., despite the negative experimental results. The advantage of this option is that you don’t need to make your SUSY complicated, it can just be the MSSM, so you keep simplicity. Of course, once you accept fine-tuning, you could get a whole lot more simplicity really easily: just throw out SUSY and stick to the SM…
     
  4. Sep 6, 2014 #3

    wolram

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    http://arxiv.org/abs/1308.4768


    The first three years of the LHC experiments at CERN have ended with "the nightmare scenario": all tests, confirm the Standard Model of Particles so well that theorists must search for new physics without any experimental guidance. The supersymmetric theories, a privileged candidate for new physics are nearly excluded. As a potential escape from the crisis, we propose thinking about a series of astonishing relations suggesting fundamental interconnections between the quantum world and the large scale Universe. It seems reasonable that, for instance, the equation relating a quark-antiquark pair with the fundamental physical constants and cosmological parameters must be a sign of new physics. One of the intriguing possibilities is interpreting our relations as a signature of the quantum vacuum containing the virtual gravitational dipoles
     
  5. Sep 6, 2014 #4

    wolram

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    https://www.sciencenews.org/blog/context/higgs-mass-isnt-natural-maybe-it-shouldnt-be


    There’s something wrong with the Higgs boson.

    It’s like a two-headed snake. Cats playing with dogs. Rabbits without baby bunnies. Voldemort’s nose.

    It ain’t natural.

    In this case, “natural” does not mean the opposite of artificial, like sweeteners or Christmas trees. “Naturalness” is actually a technical term in physics, although there is some confusion about exactly how to define it.

    In any event, the Large Hadron Collider’s discovery of the Higgs boson with the mass that it had (roughly 125 times the mass of a proton) has perplexed some physicists because they can’t articulate a “natural” explanation for it.

    To get a just a bit more technical, the issue involves what physicists call the “hierarchy” problem. It has to do with particle masses. (Remember, the Higgs particle is the offspring of a field that gives particles their masses.) Naively, it would be natural to expect particles to have masses at roughly the scale of the fundamental quantum unit of mass, known as the Planck mass. It’s calculated by properly combining Newton’s gravitational constant, Planck’s constant and the speed of light in a formula producing a number with the units of mass. And it turns out to be roughly 10 million billion trillion electron volts, or 20 millionths of a gram. By particle physics standards, that’s enormously heavy — physicists variously compare it to the mass of an eyebrow hair, or a flea’s egg, or millions of bacteria.
     
  6. Sep 6, 2014 #5

    Chalnoth

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    Yes. We've barely scratched the surface on experimentally probing the available parameter space.

    To me, this is sort of like asking, "Can we really be sure there are any bears in this forest?" after only walking through the edge of the forest for five minutes.

    Provided the planned re-opening of the LHC goes well next year, we should really be able to start delving well into that parameter space experimentally. Ideally we'll get some good information as to where to go next with high-energy physics whether or not supersymmetry happens to be correct.
     
  7. Sep 6, 2014 #6

    wolram

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  8. Sep 6, 2014 #7

    Chalnoth

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    The usual sensationalist claptrap. The real world isn't quite so dramatic. If we get the LHC reliably producing collisions in excess of 10TeV energy, and we don't see any hint of supersymmetry even after a couple of years of searching, then maybe supersymmetry will start to look a bit less likely. But the only way it will really be dead is if we start to see some deviations from the standard model that you would not expect to see at all within supersymmetry, but are explained by some other theory.
     
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