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Dark forces from extended supersymmetry

Dark forces from extended supersymmetry






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    Dark forces from extended supersymmetry Dark forces from extended supersymmetry Presentation Transcript

    • Dark forces from extended supersymmetry Mitchell Porter presented at University of Queensland 10 November 2011
      • In supersymmetry, fermions are paired with bosons.
      • For example, the spin-2 graviton is paired with the spin-3/2 gravitino, which is a candidate for the dark matter.
      • In extended supersymmetry, particles have multiple superpartners.
      • Since there is about three times as much dark energy as there is dark matter, one might look for an N=4 or N=8 supergravity in which ¼ of the gravitinos are dark matter and ¾ of the gravitinos are dark energy.
      • I have no such model. But there is an old proposal for particle physics in which the gravitinos are naturally divided into a set of two and a set of six. This is Gell-Mann’s 1983 proposal for N=8 supergravity.
      • N=8 supergravity contains 1 graviton, 8 gravitinos, 28 gauge bosons, 56 spin-1/2 fermions, and 35 complex scalars.
      • To realize Gell-Mann’s proposal, first we work in a space with negative cosmological constant (AdS4). N=8 supergravity has SU(8) x SO(8) symmetry there.
      • Then we break the symmetry to SU(3) x U(1).
      • 48 of the 56 spin-1/2 fermions end up in representations that can be assembled into the quarks and leptons.
      • The proposal has some problems. For example, the weak force is not directly accounted for. Also, the masses are wrong!
      • But we are in a space of the wrong curvature anyway. We need asymptotically de Sitter space, not anti-de-Sitter space, to match the real world.
      • We need some extra positive energy density, to uplift to de Sitter space. What about the gravitinos?
      • As it turns out, under SU(3) the N=8 gravitinos fall into two groups. Two are “singlets”, the other six are “triplets” or “antitriplets”.
      • Also, the eight unused spin-1/2 fermions have the same SU(3) transformation properties as the gravitinos. They are “goldstone fermions” that are absorbed by the gravitinos and give them mass.
      • You now know as much as I do. I still have no model, but the path ahead is clear…
      • Look for a solution to N=8 supergravity with the following characteristics:
      • It is a de Sitter uplift of the SU(3) x U(1) critical point.
      • Dark energy comes from a condensate of SU(3)-triplet gravitinos.
      • Dark matter comes from the remaining SU(3)-singlet gravitinos.
      • Now I will describe where these ideas actually came from.
      • In 2005, Bilson-Thompson proposed to identify the quarks and leptons with braids. He had no equation, just an idea.
      • In 2010, Marni Sheppeard noticed that there were some unused braids, the reflections of the neutrino braids. She called them “mirror neutrinos”.
      • Sheppeard and her collaborators are trying to devise a whole new framework for physics using the extended braid set. A condensate of mirror neutrinos will be responsible for gravity and for mass.
      • Cosmologically, they use the ideas of Louise Riofrio, who predicts 9/4 π for the dark energy fraction and 3/4 π for the dark matter fraction. Sheppeard wants to get the 1/4 π factor from recent “holographic” calculations of viscosity of plasmas in strongly coupled field theories.
      • So it’s all rather unorthodox.
      • Nonetheless, it was during a search for a model realizing the Riofrio-Sheppeard theory of the dark sector, that I unearthed Gell-Mann’s proposal.
      • Sheppeard’s mirror neutrinos correspond to the SU(3)-(anti)triplet goldstone fermions in Gell-Mann’s proposal, the ones that give mass to the “dark energy gravitinos”.
      • There are many other aspects to the possible mapping between Sheppeard et al and Gell-Mann 1983, but they are somewhat technical and uncertain.
      • So to sum up, we have, not just a new approach to the physics of the dark sector, but the possibility that N=8 supergravity has a radically different description in terms of quantum braids.
      • I used to say that dark cosmology offered no real guidance to particle physics, because there was too little data. I won’t say that again!