E8 theory…


Garett Lisi recently posted An Exceptionally Simple Theory of Everything on ArXiv. Don’t expect the article to really be “exceptionally simple”, the title is really a pun on the fact that E8 is the largest exceptional simple Lie group. There’s nothing really simple about all this, except that it’s a beautiful form of symmetry.

This work was quickly picked up all over the place, for example at Backreaction, where a good discussion followed. It even made it to Slashdot, where whatever discussion was typical Slashdot (“it’s funny, laugh!”🙂. Not useful, but entertaining.

Unfortunately, it also made it to less reputable science outlets. My favorite blogger made predictable comments about it being stupidly wrong, rejoicing in an arXiv demotion from hep-th (“professional”) to gen-ph (“laymen’s fantasies”):

Update I: the preprint was re-classified from the professional hep-th archive to gen-ph, general physics, an archive mostly dedicated to laymen’s fantasies. Thanks God. Comment for general readers: this preprint is of course not peer-reviewed and probably won’t get published anywhere.

That demotion may very well be Motl’s own fantasy, as the preprint still appears as hep-th for me. In any case, you can compare Lubos’ “professional” piece of work to, say, John Baez’s reaction to the exact same event. True, Baez also shows some skepticisim, which I will share for the moment, but he remains healthily neutral, whereas Motl “exploded in laughter” at the first equation in the paper. More importantly, Baez, unlike Motl, starts looking at similar work, like earlier attempts at unifying forces using SU(5). That’s the right way to go. Even if the paper is totally bogus (which I don’t think it is, more likely to be subtly bogus), you still have to prove it, which Lubos Motl spectacularly failed to do as usual.

So… Why be skeptical? Simply because that’s not the first time folks look at E8, and even if Garrett Lisi’s approach is innovative, it may still very well be entirely wrong, until experiments show the predicted additional particles. But at least, Garrett is ready to take that risk, and that’s worth a lot in my book. And, if nothing else, he provided us with a very beautiful video:

So at this time, what I find a source of concern is not Garrett’s article itself, it’s all the publicity around it. Early publicity for something as “grandiose” as a “theory of everything” can prove fatal to the researcher if he turns out to be wrong, or to not make as much progress as expected. That’s in no small part what happened to Laurent Nottale. And just like for Nottale, that would be a shame if Garrett Lisi ended up doing nothing more than surfing in Hawaii…

And I also believe that Garrett Lisi’s work is absolutely not in conflict with my own ideas, nor any step in that direction. In other words, the paper I submitted still shows, in my opinion, just how far Garrett’s work is from a “theory of everything”.

4 thoughts on “E8 theory…

  1. I’m a bit confused by your comment on Laurent Nottale here; sure scale relativity isn’t the most active area of research despite the ten-and-something years of research, but still … apart from being inactive, is there something to indicate his work is flawed somehow?

  2. I don’t think Nottale’s work is flawed. It’s rather that he set expectations very high initially, in no small part due to media exposure (the cover of a French magazine that said “the new Einstein” or something silly like that). That did not help him in the long run, unfortunately.He personally remained very productive, but the “bad reputation” (and possibly some other reasons which I have insufficient data to comment on) never allowed a strong community of scientists to build around these ideas. There are a few here and there, but compared to LQG or strings, it’s really small.It does not help that he still has the support of a community of “crackpots”, as physicists like to call them, i.e. folks who have no understanding of what Nottale’s work is about but like the “fringe” character.

  3. About :”That’s in no small part what happened to Laurent Nottale.”See”Derivation of the postulates of quantum mechanics from the first principles of scale relativity”http://arxiv.org/abs/0711.2418That’s what I call “blow your mind” progress.

  4. Laurent,Thanks for the article pointer. But about what happened to Laurent Nottale, I am referring to the sociological aspect, the relative lack of traction with other scientists. I was not implying he had stopped working on his theory.As an illustration, compare the number of citations for Nottale and Rovelli. This is not a metric of the quality of the work, but a metric of how well known and understood it is.Now, to be fair, I don’t think the specific article you referred to is significant progress compared to Nottale’s earlier work. I do buy the idea of scale relativity in general, but I’m not convinced by many of the arguments in the article.For example, in order to find a complex wave function, Nottale introduces a differential equation (between equations (27) and (28) in the article) which I find rather ad-hoc. He also postulates geodesics of a fractal space time, which similarly seems arbitrary to me. It doesn’t seem “simpler” as a starting postulate than quantum mechanics to me, and it’s a bit less precise, since as Nottale observes, “the scaled fluctuation a is no longer defined”.I honestly prefer my way of finding a complex wave function in the TIM, even if at this point I am honestly not convinced “my” probability of presence wave function is really the same as the traditional QM wave function. It shares many properties, but I have not proven it’s the same thing (and it may very well not be).

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