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## Main Question or Discussion Point

My ongoing study of https://www.physicsforums.com/showthread.php?t=483871" that this has something to do with the fact that the shear viscosity to entropy ratio of a strongly coupled N=4 super-Yang-Mills plasma is 1/4π.

Sheppeard has her own program of deriving field theory from categorical quantum gravity, but I'm not going to talk about that here. Instead, I want to speculate on how one might try to get Riofrio's numbers (perhaps just as a first-order approximation) from a known field theory.

"3/4π" is the central number here. That's the dark matter fraction, the dark energy fraction is exactly three times that, and that already accounts for 96% of the universe. So it could be that we have four copies of the same physics, each of them accounting for 3/4π of the total energy density; but one of them is in "dark matter" mode, and the other three are in "dark energy" mode.

In my attempts to find a field-theoretic analogue of Sheppeard's particle physics, I was driven to consider N=2 gauge theories. In such a theory, there will need to be a lot of heavy particles - for each visible particle species, there will also be a superpartner, a mirror partner, and a mirror superpartner, and all of these (on a conventional understanding) will need to be heavy. Cosmologically, one would therefore expect the dark matter to consist of the lightest stable super- or mirror particles. In other words, the dark matter sector consists of stable heavy particles from a N=2 gauge theory.

But in order to interpret Riofrio's numbers, I just speculated that the dark energy sector consists of three almost-copies of the dark matter sector. Thus, in a very simple way, I am led to wonder whether Riofrio's numbers can somehow come from d=4 N=8 supergravity.

Before superstrings, there was a lot of interest in N=8 supergravity as a theory of nature. The spectrum doesn't look much like the real world, so one has to treat it as a preon theory. I believe that one reason it fell out of favor was the apparent impossibility of getting chiral fermions, the consideration which also sank Kaluza-Klein models based on d=11 N=1 supergravity. Also, it was believed to be divergent, and therefore not fundamental.

In recent years, new methods of calculation have suggested that N=8 supergravity is perturbatively finite after all, and it has even been proposed that it is http://arxiv.org/abs/0808.1446" [Broken]]

• identifies SU(3) with the diagonal subgroup [SU(3)

• shifts all U(1)

Of course, for this to work there would have to be new and very strange dynamics, where the weak interactions would have to be dynamically generated with composite W and Z bosons, while the gluons and the photon would be elementary. Furthermore, the family symmetry SU(3)

This sounds a lot like what we have been looking for in the search for a theory that produces https://www.physicsforums.com/showthread.php?t=485247", where I have been considering the possibility of a perturbed version of the self-duality of N=2 N

So what is the cosmology of N=8 supergravity? I read somewhere that it develops a large negative cosmological constant without finetuning. But couldn't we apply Weinberg's anthropic argument for a small positive cosmological constant? As for the dark matter, perhaps some version of http://arxiv.org/abs/hep-ph/0202161" [Broken], solitonic diquark condensates containing a trapped exotic phase of QCD, can do the job. It seems somehow concordant with Nicolai's own appeal to exotic dynamics.

This may just be the first step on a long road; "the simplest quantum field theory" seems to be very hard to study. But the reward could be very great.

Sheppeard has her own program of deriving field theory from categorical quantum gravity, but I'm not going to talk about that here. Instead, I want to speculate on how one might try to get Riofrio's numbers (perhaps just as a first-order approximation) from a known field theory.

"3/4π" is the central number here. That's the dark matter fraction, the dark energy fraction is exactly three times that, and that already accounts for 96% of the universe. So it could be that we have four copies of the same physics, each of them accounting for 3/4π of the total energy density; but one of them is in "dark matter" mode, and the other three are in "dark energy" mode.

In my attempts to find a field-theoretic analogue of Sheppeard's particle physics, I was driven to consider N=2 gauge theories. In such a theory, there will need to be a lot of heavy particles - for each visible particle species, there will also be a superpartner, a mirror partner, and a mirror superpartner, and all of these (on a conventional understanding) will need to be heavy. Cosmologically, one would therefore expect the dark matter to consist of the lightest stable super- or mirror particles. In other words, the dark matter sector consists of stable heavy particles from a N=2 gauge theory.

But in order to interpret Riofrio's numbers, I just speculated that the dark energy sector consists of three almost-copies of the dark matter sector. Thus, in a very simple way, I am led to wonder whether Riofrio's numbers can somehow come from d=4 N=8 supergravity.

Before superstrings, there was a lot of interest in N=8 supergravity as a theory of nature. The spectrum doesn't look much like the real world, so one has to treat it as a preon theory. I believe that one reason it fell out of favor was the apparent impossibility of getting chiral fermions, the consideration which also sank Kaluza-Klein models based on d=11 N=1 supergravity. Also, it was believed to be divergent, and therefore not fundamental.

In recent years, new methods of calculation have suggested that N=8 supergravity is perturbatively finite after all, and it has even been proposed that it is http://arxiv.org/abs/0808.1446" [Broken]]

• identifies SU(3) with the diagonal subgroup [SU(3)

_{color}× SU(3)_{family}]_{diag}• shifts all U(1)

_{em}charges by a spurion charge 1/6.Of course, for this to work there would have to be new and very strange dynamics, where the weak interactions would have to be dynamically generated with composite W and Z bosons, while the gluons and the photon would be elementary. Furthermore, the family symmetry SU(3)

_{family}does*not*commute with weak isospin SU(2)_{w}in the above scheme. Looking at the diagonal subgroup may likewise appear a strange thing to do, but according to http://arxiv.org/abs/hep-ph/0003183" [Broken] such ‘flavor color locking’ may actually occur, and not only in strongly coupled QCD! So it is not completely excluded that an ‘obviously wrong’ theory (or some extension of it) could turn out to be right after all – just like QCD would have been considered ‘obviously wrong’ had it been proposed in 1950 as a theory of strong interactions, and without knowledge of its underlying dynamics![/QUOTE]This sounds a lot like what we have been looking for in the search for a theory that produces https://www.physicsforums.com/showthread.php?t=485247", where I have been considering the possibility of a perturbed version of the self-duality of N=2 N

_{f}=6 SU(3)_{c}gauge theory. And this "stationary point with residual SU(3) × U(1) symmetry" even has N=2 supersymmetry!So what is the cosmology of N=8 supergravity? I read somewhere that it develops a large negative cosmological constant without finetuning. But couldn't we apply Weinberg's anthropic argument for a small positive cosmological constant? As for the dark matter, perhaps some version of http://arxiv.org/abs/hep-ph/0202161" [Broken], solitonic diquark condensates containing a trapped exotic phase of QCD, can do the job. It seems somehow concordant with Nicolai's own appeal to exotic dynamics.

This may just be the first step on a long road; "the simplest quantum field theory" seems to be very hard to study. But the reward could be very great.

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