E8

[Solitary]

All fields of the standard model and gravity are unified as an E8 principal bundle connection. A non-compact real form of the E8 Lie algebra has G2 and F4 subalgebras which break down to strong su(3), electroweak su(2) x u(1), gravitational so(3,1), the frame-Higgs, and three generations of fermions related by triality. The interactions and dynamics of these 1-form and Grassmann valued parts of an E8 superconnection are described by the curvature and action over a four dimensional base manifold.

What do you think of this Joseph Palazzo?  

[josephpalazzo]

Well, I have studied String Theory for a number of years, and my opinion is that it is too speculative for the following reasons:

1) It uses QFT in curved space-time, which I have also studied quite extensively, and everything in QFTCST has not been proven yet. Yes, it makes testable predictions like Hawking radiation and the Unruh effect, but those haven't been observed. So we don't really know if QFTCST is valid. But ST assumes it is right.

2) There are five String theories linked by dualities. But I doubt if duality is a fundamental principle of nature. Unlike Lorentz invariance and Gauge invariance which have proven to be necessary to develop QFT with outstanding results, there are no such success with duality. So I'm sceptical on that.

3) Even if you accept duality, and the five ST are united under M-theory, as Witten proposed, you end up with a theory that predicts too many particles, in fact, an infinite number of them. So you can twist any of the parameters in the theory to make it say whatever you want. {BTW, E8 is one of those 5 ST's, the others are type I, type II, type IIa and the SO(32)}

4) It assumes that Supersymmetry is valid. We don't know that, in fact at the LHC, they haven't found any evidence and SuSy has been ruled out up to 1000GeV. By next year, when the LHC will go full blast at 1400GeV, we will see if SuSy is valid or not.

5) No one has developped a mathematical scheme to go from 10 dimensions, which ST is stuck with, to our own 4-d world. A number of schemes were tried such as moduli stabilization, which a few years back was very promising, but all have failed to do that task.

6) The landscape problem gives 10^500 possible multiverses, which can only be resolved with the Anthropic Principle. That to me is a sure sign that ST is on the wrong track.


As I said, ST is too speculative, has too many unresolved issues.

Edit: correcting the exponent format

[josephpalazzo]

I don't think this is reasoning outside the box. More and more in the physics community are thinking along the line that gravity can't be quantized. As Freeman Dyson once indicated, if one would construct a detector for gravitational waves, the detector would have to be so massive, it would form a black hole. So even nature seems to conspire against that. And according to GR, gravity is not an interaction due to the exchange of particles as in the case of electromagnetic force or the weak and strong nuclear force, but due to the curvature of spacetime. So no interaction, no particles exchange, no QFT can be constructed to quantize gravity.

I feel sorry for Garrett Lisi, the author of the OP. For a while his paper created some sensation, which eventually petered out. That has been the fate of all the 5 String Theories and M-theory. For a short time, they created a lot of buzz only to eventually fizzle out. Some of these people have spent their whole life/career for nought, a waste of precious talent. I hope the next generation will make wiser choices as it now appears we have explored this too much, and little has been accomplished.