The December issue of Scientific American is out, and it has an article by Garrett Lisi and Jim Weatherall about geometry and unification entitled A Geometric Theory of Everything. Much of the article is about the geometry of Lie groups, fiber-bundles and connections that underpins the Standard Model as well as general relativity, and it promotes the idea of searching for a unified theory that would involve embedding the SU(3)xSU(2)xU(1) of the Standard Model and the Spin(3,1) Lorentz group in a larger Lie group.
The similarities between (pseudo)-Riemannian geometry in the “vierbein” formalism where there is a local Spin(3,1) symmetry, and the Standard Model with its local symmetries makes the idea of trying to somehow unify these into a single mathematical structure quite appealing. There’s a long history of such attempts and an extensive literature, sometimes under the name of “graviGUT”s. For a recent example, see here for some recent lectures by Roberto Percacci. The Scientific American article discusses two related unification schemes of this sort, one by Nesti and Percacci that uses SO(3,11), another by Garrett that uses E8. Garrett’s first article about this is here, the latest version here.
While I’m very sympathetic to the idea of trying to put these known local symmetry groups together, in a set-up close to our known formalism for quantizing theories with gauge symmetry, it still seems to me that major obstructions to this have always been and are still there, and I’m skeptical that the ideas about unification mentioned in the Scientific American article are close to success. I find it more likely that some major new ideas about the relationship between internal and space-time symmetry are still needed. But we’ll see, maybe the LHC will find new particles, new dimensions, or explain electroweak symmetry breaking, leading to a clear path forward.
For a really skeptical and hostile take on why these “graviGUT” ideas can’t work, see blog postings here and here by Jacques Distler, and an article here he wrote with Skip Garibaldi. For a recent workshop featuring Lisi, as well as many of the most active mathematicians working on representations of exceptional groups, see here. Some of the talks feature my favorite new mathematical construction, Dirac Cohomology.
One somewhat unusual aspect of Garrett’s work on all this, and of the Scientific American article, is that his discussion of Lie groups puts their maximal torus front and center, as well as the fascinating diagrams you get labeling the weights of various representations under the action of these maximal tori. He has a wonderful fun toy to play with that displays these things, which he calls the Elementary Particle Explorer. I hear that t-shirts will soon be available…
Update: T-shirts are available here.
Oh dear lord. Again?!?
oh, that guy. thanks for pointing this out.
by the way, Lisi seems to have gone into comercials lately…
http://cheapuniverses.com/universesplitter/
I’m deleting a sequence of comments triggered by an anonymous attack on one of the authors of the SciAm piece, Jim Weatherall. If you want to attack someone from behind anonymity here, it better be me, or it better be extremely fair, otherwise it’s a good candidate for deletion.
The exchange did contain links to something Weatherall wrote for Slate based on early Higgs rumors
http://www.slate.com/id/2167563/
and a blogposting he wrote about it featuring an exchange with Nima Arkani-Hamed.
http://stevens.edu/csw/?p=42
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I applaud this work if for no other reason than the work involved in juggling all the multiplets, although I think it is pretty clear that toying with gauge groups is not going to produce a breakthrough. The particle explorer is a fantastic toy!
-drl
Hmm.. Motl has a post just now about Weatherall, attacking him. He happens to have the very same two links (to Slate and the blog posting) you’ve retained here.
Coincidence?
This wouldn’t be the first of such “coincidences”.
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How is a mathematically rigorous disproof of a concrete proposal “really skeptical and hostile”? Facts simply are.
Or, are you suggesting that Distler-Garibaldi’s disproof is incomplete, (perhaps not unlike the very productive examples of some well-known past “no-go theorems”)? If so, please do share: we all might learn a great deal more.
Tristan,
My understanding is that Garrett is well aware that his proposal has problems. In the Scientific American article he writes:
“All new ideas must endure a trial by fire, and this one is no exception. Many physicists are skeptical—and rightly so. The theory remains incomplete.”
I have no problem with skepticism, I’m skeptical about many of Garrett’s ideas too. If Jacques wants to make a clean technical argument showing the nature of the problems with Garrett’s proposal, that’s great, and could be potentially worthwhile. But I don’t see any reason for the hostile, sneering tone of Jacques’s blog posting explaining these points. This is not the way to professionally make a credible technical argument.
He and Lubos have done an excellent job of convincing many people that there’s something seriously wrong with string theory and string theorists. Instead of writing in here to complain about my accurate characterization of Jacques’s writings as “hostile”, you might want to think seriously about whether his behavior is worth defending, given how much it has cost your field.
Peter: Thanks for posting on the SciAm piece.
Chris: It was an (unpaid) endorsement of a fun app, not a commercial.
D R Lunsford: Glad you like the Elementary Particle Explorer — I think it’s a fun and worthwhile educational tool.
Tristan: What is it, precisely, that you think Distler and Garibaldi proved? Their claim is that they proved “the theory doesn’t work.” But does that follow from what they technically proved, or is it in fact a lie, dependent on a hidden assumption?
Peter: Agreed. Except I see several reasons for Distler and Motl’s sneering tone, all of which speak to their character rather than that of those they malign.
I wonder if anyone remembers Feza Gursey, who was always finding suggestive patterns in the objects of algebra. I was entranced at first, and then just sort of decided that even if that was the right way, I preferred to not go crazy thinking about it, and so good luck. It seemed to me that nothing could possibly be that complex 🙂
So my point is, this goes back a long way and not much has come of it, because it doesn’t have a new dynamical principle.
-drl
I’m reminded of the old quote “Academic politics are so vicious precisely because the stakes are so small.”[1] It seems that so little has happened of real import in HEP over the last 30 years that practitioners are left squabbling for the scraps. It’s very sad. I think it was Peter who said something along the lines that when he started his career, the Standard Model had just had the finishing touches applied to it after nearly a century of bold, dramatic progress in the field of physics. Who knew that a whole generation of physics PhDs were going to see very little happen on their watch?
[1] http://ask.metafilter.com/80812/Academic-politics-are-vicious-because-the-stakes-are-so-low
Garrett wrote:
What do you think? I’ll guess you’re hinting it’s the latter. if so, could you be really specific about what hidden assumption they’re using, and why it’s wrong?
As a complete outsider, when I skimmed through some of the Distler-Lisi exchanges when Lisi’s first preprint came out, I was amazed to see Lisi keep his cool again and again while Distler consistently displayed a belittling, arrogant tone. It seemed to me that all concerned were getting something out of the exchanges, and since both were some of the very few people in the world who could possibly understand the arguments involved, why in the world would one of them seem to consistently view the other as an “enemy”? Now to prick Distler’s enormous pride a bit, if he were such a damn expert why would he need to rely on a coauthor to “do the math” for him in the new preprint? Methinks there is more behind his anger than greets the eye, some “hidden variables” of jealousy, bitterness and frustration that keep rearing their ugly heads and interfere with what should be simply a fascinating, INSPIRING intellectual debate. Lisi’s best move is to keep reading zen books for the philosophy and leave the snide remarks to others. Beauty is not only in the eye but in the heart of the observer. Nastiness in academia has driven many gentle but brilliant souls away from the ivy halls, Lisi will have to be strong inside to continue to weather all this with wistful good humor.
Addendum: just skimmed Lubos’ twin posts on the matter, and along with some (apparently well done) general exposition, he makes some concrete criticisms which (apparently) should be seriously addressed. I say apparently because of my own ignorance, and will now shut up and watch the discussion by those who know something unfold. I will just say to Lisi that if you write an article about your own work in a popular magazine, then you are setting yourself up for a really big fall IF your work turns out to be wrong. But that fall would be no problem at all, if all that really matters to you is what is so- in all its aspects. In skiing and surfing we fall all the time, right? The wave shows us the reality, we laugh and shake our heads, look at the amazing sky and keep on going…
Bugsy,
Jacques has always been quite consistent in starting out his various blog postings on the topic by explaining that it is “mind-numbingly trivial”, elementary, and intellectually far beneath him, even if he is requiring the efforts of a specialist. This is pretty funny stuff if you know something about the technicalities of the subject. If you don’t know the technicalities, the humor still becomes pretty obvious when you see David Vogan writing to Jacques to explain to him why he has it wrong. For amusement, read Jacques’s first blog posting on the topic:
http://golem.ph.utexas.edu/~distler/blog/archives/001505.html
The comic high point there though is not Jacques, but an anonymous string theorist who writes in:
“Nice post. It would make a good final exam question for a first course on baby Lie theory, too. (A 4th year undergrad course, these days, I should point out; something worth pondering.)”
There are some other hilarious parts of this story that unfortunately I’m not at liberty to discuss here. Over the years mathematicians have learned some beautiful and important ideas from string theory, they’ve also had some very amusing interactions with string theorists.
DR: Yes, Gursey was one of the first to consider E8 for unification. I think what held people up was not knowing how to include gravity (that needed a new dynamical principle).
Casey: There have been several interesting developments in HEP, but yes, nothing as dramatic as in the previous 30 years.
John: Yes, they are relying on two hidden assumptions:
(1) Having mirror fermions makes a theory unviable.
(2) There is no way of getting rid of mirror fermions.
The first assumption is wrong because we just don’t know why particles have the masses they do, and there could be mirrors with large masses. Since what Distler and Garibaldi prove is that, under a direct decomposition of E8, there are mirror fermions, they then use (1) to claim this E8 theory is unviable. But that is a lie, based on (1), which they initially obscured. I am using this strong language because I talked to Distler in person and his strategy of obscuring (1) was made clear to me. (You might recall a lengthy and repetitive exchange on Urs’ ncat post, during which Distler refused to acknowledge what was going on.) And Garibaldi was following Distler’s word on the physics.
Issue (2) is more subtle, and harder to argue, since I haven’t written up the precise mechanism yet. But I think what’s really going on is that these mirror fermions may be related to usual fermions using an E8 gauge transformation, so that they never appear as mirrors but rather as another generation.
Bugsy: Sage advice. But I suspect I am too gritty to completely take the high road. However, the concrete criticism has been seriously addressed. Here’s a summary of criticism, and how it has played out:
(1) Impossible mixing of bosons and fermions.
The superconnection was quickly agreed to be viable.
(2) Violation of the Coleman-Mandula theorem.
The novel loophole in the theorem is addressed in the Scientific American article, and was described in more detail here. If nothing else, this new understanding opens the field for gauge-gravity unification.
(3) The dynamics is not described (with an action) invariant under the full E8 symmetry.
A couple of LQG researchers and I recently found such an action.
(4) Even one generation of fermions does not fit in E8.
This misconception, introduced and propagated by Distler and Garibaldi, is directly countered here. It was one of the more enjoyable experiences of my life to see this issue discussed in Banff with Garibaldi in attendance. I think it still pains Distler to use the standard terminology “fermions and mirror fermions,” instead choosing to say “no chiral fermions,” which is synonymous but misleading.
(5) The theory is not quantized.
The theory is compatible with the usual methods of quantum field theory. Although extensive renormalization calculations have not been carried out, I think they can and will be. The lack of a background spacetime does make this difficult though — a known problem with quantizing gravitational theories. In any case, the QFT of nonabelian Yang-Mills theories, and the geometry of BRST, is an extremely rich area that should be further explored.
(6) The theory does not accommodate three generations of fermions.
This issue was identified (by me) as the most serious problem from the beginning, with a potential solution coming from triality. As of a year ago I was discouraged, but with some insights gained at Banff I now think triality will indeed work. It’s tricky though (for the noncompact case), and I’m working on that now.
Peter: Since Distler has been very effective at persuading physicists that there is nothing to this E8 stuff, it has been less funny from my perspective. But it has certainly been interesting. And my interactions with mathematicians have been fantastically enjoyable and informative.
Garrett, it is an established fact that your theory has a non-chiral spectrum. This is what Distler and Garibaldi rigorously proved. It has been known for 40+ years that in order to describe the real world the fermion spectrum must be chiral. Hence, unless you impose some extra symmetry that would forbid the vector-like mass terms, ALL fermions will get large GUT scale masses through quantum corrections and will automatically decouple at the scale far above the electroweak scale. Thus, the electroweak scale spectrum of your theory looks nothing like the real world. This is not a lie but a basic QFT argument that cannot be refuted just by waving your hands and saying that “The first assumption is wrong because we just don’t know why particles have the masses they do, and there could be mirrors with large masses.”
Oh for christ’s sake, Garrett. Do we really have to go through this again? You can call your ‘superconnection’ whatever you want (although you still have not acknowledged that the very BRST superconnection you cite and don’t seem to understand is related to a Grassman symmetry), but that doesn’t mean it makes sense. For example, are the currents that relate the fermions and bosons in your model Grassman or commuting? If they’re Grassman, do they fit into an ordinary Lie algebra or a superalgebra?
For the Coleman-Mandula theorem, you need to address what happens in the low-energy theorem. In particular, what breaks the symmetry mixing spacetime and internal indices and at what scale?
For your paper with Lee, I’d be a lot more interested if it had fermions in it.
The idea of net numbers of generations has been standard in high energy physics for at least thirty years and probably longer. You’re welcome to present a reason why your mirror fermions don’t pair up with a high mass and disappear from the low energy spectrum, but until you do no one’s going to care about the fact that you don’t like the standard terminology; they’re just going to ignore you.
For quantization, if it’s so easy, why don’t you sit down and compute something? Like the low-energy spectrum, say. If you’re going to go around and talk about what particles your theory predicts at the LHC, I’d think you’d at least have the responsibility to compute a scattering amplitude or two.
Or, for that matter, what are the free parameters in your theory? What sets the Yukawa couplings? What sets the Higgs self coupling? Neutrino masses? The CKM matrix? The value of the cosmological constant? Even if you’re not able to give numbers, can you at least explain the mechanism by which these parameters arise? Are they all undetermined? Are there relations between them?
And, seriously Peter. The math here is the computation of a few branching relations for the adjoint of various real forms of E8. Big fucking deal. There’s probably a computer program out there that will do that for you these days. Must all these discussions end up focussing on how mean Jacques and all the other people on the internet are? We could just cut and paste from the old discussion on Cosmic Variance and save us all some time.
Aaron,
Sure, the kinds of mathematical questions raised by Jacques are answerable with known mathematical techniques. But, no, they’re not trivial, and only an idiot would think they’d make a good final exam question for an undergraduate course on Lie theory.
I’ve had extensive experience trying to have technical discussions with Jacques, just about all of which are publicly available on various blogs, so anyone who cares can read them and see for themselves what they think. Based on that experience, I can easily see why Garrett, who’s a very polite, mild-mannered guy, describes what he encountered with a strong word like “lying”. The problem with Jacques is not that he’s mean (I hear that, like Lubos, he’s a perfectly nice guy in person, the problem is just when he gets a keyboard in his hands). The problem is that he’s unprofessional and dishonest. There are well-understood rules for how professionals conduct intellectual arguments (e.g. avoid ad hominem attacks, try to accurately describe your opponents arguments, etc.). Jacques and Lubos don’t play by those rules. In Lubos’s case it’s immediately obvious, with Jacques it takes a while to figure out.
“There are well-understood rules for how professionals conduct intellectual arguments (e.g. avoid ad hominem attacks, try to accurately describe your opponents arguments, etc.). Jacques and Lubos don’t play by those rules. In Lubos’s case it’s immediately obvious, with Jacques it takes a while to figure out.”
Well, it’s not an ad hominem attack to state that Garrett has never published a peer-reviewed paper on his “theory.”
Nor is it an ad hominem attack to note that Distler *has* published a paper refuting Lisi’s theory.
What *is* an ad hominem attack is to label the physicist publishing peer-reviewed papers as somehow being unprofessional, while cheering the one who does not publish peer-reviewed papers and receives all the “fantastic” hype as behaving professionally. What you are doing, Peter, is “attacking the man”–Distler–while ignoring his superior physics and math, which was published in a peer-reviewed journal.
Bugsy writes, “Now to prick Distler’s enormous pride a bit, if he were such a damn expert why would he need to rely on a coauthor to “do the math” for him in the new preprint? Methinks there is more behind his anger than greets the eye, some “hidden variables” of jealousy, bitterness and frustration that keep rearing their ugly heads and interfere with what should be simply a fascinating, INSPIRING intellectual debate. Lisi’s best move is to keep reading zen books for the philosophy and leave the snide remarks to others.”
“enormous pride” is a snide, ad hominem attack.
“if he were such a damn expert” is a snide, ad hominem attack.
“methinks there is more behind his anger than greets the eye, some “hidden variables” of jealousy, bitterness and frustration that keep rearing their ugly heads ” is a snide, ad hominem attack.
hey peter et al.–instead of the snide, ad-hominem attacks, why not try to refute distler’s paper on a scientific, mathematical level, and then publish it like distler did?
seems distler is taking the high, professional road, while you guys are taking the snide low road…
Mark,
I have no dog in the argument between Garrett and Jacques over chirality problems in what Garrett is trying to do. As I said, I’m in the camp of skeptics that Garrett has a workable unified theory. I agree that you can’t automatically conclude from the fact that Jacques or Lubos argues in a dishonest and unprofessional way that they’re wrong.
Again, I’m just telling you what my personal experience with Jacques is, going back now quite a few years, on several different topics. The relevant exchanges are in the public domain, if anyone cares.
Peter,
I’m glad that your skepticism is not as one-sided (“I’m skeptical about many of Garrett’s ideas too”) as it seemed to me; sorry about that: my bad. In turn, however, writing “you might want to think seriously” implies that you know that I don’t. But, never mind.
Finally, thanks for a nice book; I’ve learned a lot about human nature.
Peace, out.
Just for my own peace of mind, I’ll try to summarize my own understanding of various problems that confront Lisi’s theory, or indeed any attempt to pack all known particles into the adoint representation of E8.
I’ll try to do this in a fairly lowbrow sort of way, so more people can understand what I’m saying. This increases the risk of oversimplifications, but doubtless I’ll be corrected here if I make any mistakes, and even if I don’t.
So here goes:
Most importantly, particles have very distinct personalities, whereas all 248 dimensions of E8 look alike. E8 is very symmetrical, that’s why people like it. But this beautiful symmetry needs to be severely broken for anything like real-world physics to fall out.
First, particles come in two kinds: bosons and fermions. If we chop E8 into a bosonic part and a fermionic part we no longer have the whole symmetry of E8. Garrett writes:
but I’m not sure anyone there agreed it was ‘viable’: Urs merely suggested this idea as a way forward, but as Aaron notes,
I see no way to get E8 symmetries that mix fermions and bosons in a model where the symmetry of E8 has been broken by deliberately chopping it into bosonic and fermionic parts.
Second, even among fermions, different particles have drastically different personalities: for example their masses, and the rates at which they turn into each other, which are described by the numbers in the Cabibbo-Kobayashi-Maskawa matrix and the Maki-Nakagawa-Sakata matrix. Similarly, in the realm of the bosons there’s the Higgs mass and other numbers. Garrett’s work has nothing to say about these. Without these numbers we can’t do real-world physics. But the big problem is this: I don’t see any way to get these numbers into the game without further breaking down the symmetry of E8. Why? Because again, E8 symmetry wants all particles to be alike, but these numbers describe how they’re not.
Third, there’s no way to pack all known fermions into E8 without positing two copies of E8 and giving every fermion a mysterious unseen partner called a “mirror fermion”. To keep these rascals from being seen we could claim they’re more massive than the guys we see – but no method for this has been described yet, to my knowledge.
(This should be vaguely reminiscent of the problem with supersymmetry, where every known particle gets a “superpartner”, and then we have to wave our hands frantically and try to find a way for those superpartners to be a lot heavier, to explain why we haven’t seen them. But at least in the case of supersymmetry, a method for doing this has been described. It’s a completely ad hoc, ugly method that involves breaking supersymmetry by hand, and throwing over a hundred extra unknown parameters into the Standard Model! But it’s still a method.)
Given all this, it should not be surprising that Garrett has not yet done calculations with his theory that reproduce the physics of the world we see around us. I am very glad to be doing something easy like trying to prevent global warming.
I have an idea! Lisis should:
a) publish some papers in journals
b) answer john baez et al.’s skepticism
c) present some testable predictions
d) have them tested
e) be labeled the next-einstein and move on to selling i-phone universe-splitter apps and t-shirts
But right now he is beginning with e), and naturally, this rubs some hard-working physicists doing a) the wrong way. 🙂
Add to this the powerful behind-the-scenes financial and media forces at play here, and that this has been going on for over three years with no new developments nor solutions to the problems from Lisi which teh greater community recognizes, and some physicists are a bit frustrated that they have to take time off of their research to get the simple truth of the E8 hype heard above the well-funded media train.
Tristan,
My apologies for any mistaken assumptions, I should know better. Glad you liked the book.
Mark,
The idea that what motivates Jacques is willingness to bravely stand up to a well-funded, powerful lobby promoting over-hyped ideas about unification to the public is very funny.
Yes Peter–it is perhaps funny. But true! And props go to Distler here for actually publishing sound peer-reviewed papers, which is what physics has ever been about, long before this era of anonymous wikipedia editors/blogs/postmodern/ironic/behind-the-scene machination physics and t-shirt sales.
And yes–I do realize how in certain ways Lisi was used by some to satirize the String Theorists, but two not even wrongs do not make a right GUT.
Best,
Mark 🙂
At this point in time, what distinguishes Lisi’s claims from those of the Bogdonavs?
At any rate, Lisi has had almost four years to publish a single peer-reviewed paper since all the hype started with… so what exactly is he waiting for?
In the history of science, has an unpublished, unaccepted, and now refuted theory ever received so much attention and hype?
Is this a product of our times, whence politics has trumped physics?
Something like this would have been impossible, even ten years ago.
“It’s a completely ad hoc, ugly method that involves breaking supersymmetry by hand”
The SUSY breaks in the hidden sector sponteneously and is mediated to the visible via a certain mechanism; so this is not what I would call an ugly/unnatural ad hoc method.
From reading through the above, it seems that Peter is motivated largely by his past interactions with Distler, and that he finds Lisi to be a “nice guy.” Does Peter think that bringing personalities into a discussion of physics is “professional?” It seems the professional viewpoint would be to note that while Distler has published a paper refuting Lisi’s theory in a peer-reviewed journal, Lisi has yet failed to publish a paper supporting his theory. And so, I guess the best Lisi’s supporters can do is to use ad hominem attacks. But is this professional. If so, what has the physics profession become, where spurious, unpublished science is hyped, and those who question it are attacked on a personal level?
Brian,
The Bogdanovs (not “Bogdanavs”) are the poster-boys for the problems with peer-review. They published five peer-reviewed articles, two of them in very well-known and highly-respected journals. One of them was given his Ph.D. on the basis of having published such peer-reviewed articles. The articles are complete gibberish, and very different than Garrett’s. Garrett is making clear statements and proposals, some of which may be wrong and/or incomplete. What he’s saying is so clear that Jacques can write a mathematical physics paper purporting to give a rigorous refutation of some of it.
The fact of the matter is that one can’t judge this kind of research on whether it is peer-reviewed or not, you have to read the things, understand them and make up their own mind. In my posting I gave links people can follow to do this, and that’s what they should do if they are seriously interested in this particular question. I’ve also noted in the comments that my experience with Jacques is that he doesn’t follow the usual rules for intellectual debate, which you can check by reading my public exchanges with him. You may or may not find that relevant if you try and follow his arguments with Garrett.
Giotis,
You’re conjecturing an unobserved entirely different “hidden sector” of physics that spontaneously breaks the symmetry, interacting with ours through interactions cooked up to completely escape any currently observable effects.
Tastes may vary, but ugly/unnatural/ad hoc all seem to me reasonable adjectives to apply to this scenario.
Thanks Peter,
You write, “Garrett is making clear statements and proposals, some of which may be wrong and/or incomplete.”
Which of Garrett’s “clear statements” are “right” and “complete?”
I have read his work and while he stated that the LHC can test his theory, in reality his theory makes no predictions. Perhaps I missed that part? If so, please do share!
And if peer-review is so completely broken, what should replace it? Media campaigns, anonymous wikipedia editors, and the suppression of all peer-reviewed articles mathematically refuting Garrett’s theory?
Brian,
As I’ve noted repeatedly, I’m somewhat of a skeptic on the subject of Garrett’s theory. I’m not going to spend more of my time defending his work for him. All I’ll say is that I’ve read his papers, I’ve read the Bogdanov papers and the two things are completely different.
Obviously I’m not arguing for the suppression of anyone’s articles, peer-reviewed or not. Given the broken nature of the peer-reviewed system, I don’t think you can conduct an argument about the value of an idea by saying that X is peer-reviewed and Y isn’t. Or by seeing that Z has made it into Wikipedia, or is the subject of an article in a popular magazine.
You need people who know what they are talking about to discuss the issue as honestly and clearly as they can. In many cases things will come down to whether there’s any hope that future work will fix known problems with some idea (and I think that’s what’s going on here, as well as in string theory). Reasonable people will differ, with those who believe problems can be overcome going on to try and do so.
Peter,
Yes it’s a matter of taste if you like but my main point is that you don’t put the soft SUSY breaking terms in the langranian completely arbitrary and by hand as Baez said. There is a proposed theoretical mechanism/justification for the presence of these terms and in any case the SUSY breaks spontaneously which is not unnatural at least.
Thanks very much for your time, Peter,
I do not wish to take up more of it, but I feel that if Garrett Lisi has made clear statements and proposals, it would take but a moment for you to express them. For instance, Einstein and Newton made clear proposals: E=mc^2 and F=ma.
You write, “Garrett is making clear statements and proposals, some of which may be wrong and/or incomplete.”
Which of Garrett’s “clear statements” are right and complete?
Thank you for your time.
Brian,
Sorry, Garrett’s ideas are a lot more complicated than F=ma, and I believe the same will be true of whatever ideas finally get us beyond the Standard Model.
You appear to be a complete fanatic on the Garrett issue, posting seven highly repetitive and uninformed comments here in the past few hours. That’s enough, I’m deleting the rest. If you want to carry on this kind of campaign, you’ll have to do it somewhere else.
Mr. Woit,
I’m no physicist, so of course I don’t have the slightest idea of the merits of the arguments in this discussion.
But on reading through this exchange I did notice something which was not mentioned:
Some of the postings, though on the surface pretending to be about physics, seem to me to have a closer connection with another branch of science – psychology.
What the real problem here seems to be is addressed quite beautifully in a single sentence – the last one in a
recent article about Mr. Lisi in the Telegraph:
“… [Lisi] tells me: “I’ve been spending every other day surfing or kitesurfing here in Maui.” No wonder his peers are jealous.”
At least some of them.
Before I address the many points that have been raised, I’d like to say something on the personal and meta level about where I’m coming from. Many people seem to be behaving as if this E8 Theory is being forced on them, or as if I am some kind of salesman or trickster. What I am is a physicist who struck out on his own to pursue a question (specifically, what spinor fields are geometrically) that was of little interest to the broader community. I worked on this question largely in isolation for ten years, self supported, never pushing my ideas on anyone, and happened to find something incredibly cool. If I seem pushy now it is because I’m excited about this E8 Theory and I want to share it. At the same time, I openly acknowledge its current deficiencies and where there is work left to do. Regarding the media… sometimes excitement tempered by scientific skepticism is too subtle for editors and tv hosts, and hype gets extremized, which is unfortunate. I do have a tendency to say “yes” to interviews, invitations, and speaking engagements — so I am complicit to that degree, but in my defense it is because I’m excited about what I’ve found, and where it may lead. Also, as prospective theories of everything go, this one does look pretty awesome on a tshirt. (No, I’m not going to make money off of them, nor have I made money selling anything — the shirts are for love.) That said, I will now throw myself back into this comment thread and address the points raised. I generally enjoy and benefit from the high level of discussion on this blog.
-Garrett
Mark: You’re wrong on several counts. Distler and Garibaldi proved that their version of E8 Theory has a non-chiral spectrum. It is my thinking that mirror fermions (and 64 other E8 root vectors) can be gauge transformed to another chiral generation. However, since this is yet to be formally established, I’m willing to play along with the possible existence of mirror fermions. And the bottom line is that the existence of mirror fermions has not been ruled out. So although they are bad, they do not make a theory wrong, merely unattractive — and I expect this to change so that the problem is irrelevant.
Giotis wrote:
I don’t really follow particle physics much these days, so I could easily be behind the times. Spontaneous symmetry breaking is, of course, much nicer than adding soft SUSY breaking terms by hand! I’d like to learn more about the state of the art.
Is the idea of spontaneously broken supersymmetry widely used in particle physics phenomenology, or is it just a proposal that’s been studied in some toy models?
If the former:
Does someone know how to get a supersymmetric extension of the Standard Model where supersymmetry is broken spontaneously? If so, how do the superpartners get their masses? Is there some theoretical reason why all observed particles have superpartners much more massive than they are, rather than comparable masses – or is this fact somehow fed in by hand?
Etcetera, etcetera – lots of questions.
Garrett–in your Scientific American article, you claim that the LHC will test your theory.
How will it do this?
What are the specific particles and masses predicted by your theory?
Thanks!
Sure. There are tons and tons of such models. The usual idea is that you have some hidden sector with a bunch of stuff that spontaneously breaks supersymmetry. The breaking is then communicated over to the MSSM by some sort of mediating particle. This is often a gauge field (gauge mediated susy breaking) or a graviton (gravity mediated supersymmetry breaking). It’s a little old, but I think Martin’s review hep-ph/9709356v5 has a pretty decent overview. As is often the case with these things, as soon as you solve one problem, another one will often pop up.
Aaron:
The superconnection I am using — the formal sum of a 1-form and a Grassmann field — is a well established mathematical construction. There are references cited in my papers, as well as from the link I provided. Such a superconnection is conventionally used in the BRST approach to YM gauge quantization. I am simply using the same well established mathematical formalism, with a different physical interpretation. I am sorry if it’s unfamiliar to you — it’s unfamiliar to most physicists, but it’s an interesting geometric structure worth understanding.
An excellent question, which is answered in detail in this paper with Lee and Simone. To summarize: the E8 connection obtains a nonzero VEV, separating the gravitational and gauge sectors of the connection, thus satisfying C-M at low energies.
It does. See Section 3.
For the rest of your questions, they’re being addressed elsewhere in this thread — or they’re pure snark. If I’m failing to address a question you have, try posing it more politely. In general, if you think E8 Theory is hopeless, then yes, do what you like and ignore it. Might I recommend you choose one of the other ToE’s that have made fruitful progress over the last 30 years — oh wait, there are none. Maybe you can find one yourself that you like better.
Mark:
No, but it’s wrong. The paper with Lee and Simone lays out 90% of the theory, and was published in J. Phys. A: Math. Theor. 43 (2010). Lee and I tend to just put papers on the arxiv, but Simone thought it would be good to put it in a journal. There was no problem getting it published.
I did. The resulting paper is here, which I believe makes things crystal clear, as well as forming a more complete introduction to E8 Theory.