Garrett Lisi has a new paper, “An Exceptionally Simple Theory of Everything.” Many people seem to think that I should have an opinion about it, but I don’t. It’s received a good deal of publicity, in part because of Lisi’s personal story — if you can write an story with lines like “A. Garrett Lisi, a physicist who divides his time between surfing in Maui and teaching snowboarding in Lake Tahoe, has come up with what may be the Grand Unified Theory,” you do it.
The paper seems to involve a novel mix-up between internal symmetries and spacetime symmetries, including adding particles of different spin. This runs against the spirit, if not precisely the letter, of the Coleman-Mandula theorem. Okay, maybe there is a miraculous new way of using loopholes in that theorem to do fun things. But I would be much more likely to invest time trying to understand a paper that was devoted to how we can use such loopholes to mix up bosons and fermions in an unexpected way, and explained clearly why this was possible even though you might initially be skeptical, than in a paper that purports to be a theory of everything and mixes up bosons and fermions so casually.
So I’m sufficiently pessimistic about the prospects for this idea that I’m going to spend my time reading other papers. I could certainly be guessing wrong. But you can’t read every paper, and my own judgment is all I have to go on. Someone who understands this stuff much better than I do will dig into it and report back, and it will all shake out in the end. Science! It works, bitches.
For a discussion that manages to include some physics content, see Bee’s post and the comments at Backreaction.
Dear B,
Sure, I agree with you. One of the great thing to me (at least in principle) with physics is that in principle it is based on the idea of cooperation (that is cooperation to share our ideas, with the common goal of describing and understanding reality and Nature; the arXiv is a great example of that), in contrast with our capitalist society which is based on the idea of competition. Of course, for such a “cooperative system” to work, we should do our best to work together and collaborate, that is be respectful of each other, honest, not overstate our work, not be condescendent, be humble, etc. These are all essential to me for a collaborative system to work at its best.
What I meant is that int the actual realm of academia, as you say there is all kinds of personalities, and very often the more humble and honest people are not the loudest ones (I don’t think “arrogant” people dominate the fields, simply often they are louder). So as people who want to continue working in a collaborative environment we should also be able to go beyond just “counterattacking”, and learn to deal with personalities different from our “ideals”. And this involves, in particular, just ignoring what we think is condescendent, or arrogant, instead of replying in the same way like a lot of people seem to do on blogs unfortunately. Since our goal is still a collaborative goal of trying to understand the world, and while someone may think a person is arrogant, he may still have good ideas that are worth looking at (this has happened so often in the history of science…). Do you agree?
Best 🙂
vincent
Dear all,
Unless I am having a particularly opaque day, Distler’s remarks on Pati-Salam are incorrect. Let me explain the issue that is troubling me. What is usually called the Pati-Salam model was defined in two papers, one of which is accessible through the KEK archive and is Jogesh C. Pati, Abdus Salam, LEPTON NUMBER AS THE FOURTH COLOR.Phys.Rev.D10:275-289,1974. (I should note this paper has 2700+ citations, so this is not an obscure work.) Another clear paper is H.S. Mani, Jogesh C. Pati, Abdus Salam, ‘NATURALNESS’ OF ATOMIC PARITY CONSERVATION WITHIN LEFT-RIGHT SYMMETRIC UNIFIED THEORIES. Phys.Rev.D17:2510,1978. In these papers it is clearly explained that their theory is parity invariant and parity is broken only spontaneously. They are explicit that for every left handed current in their model there is a parity related right handed current with equal coupling constants. Hence before spontaneous symmetry breaking the fermion rep for Pati-Salam must be parity invariant. More specifically, in the first paper above, just after eq 3, they state that the fermions are in the representation (4-bar,2,1)+(4-bar,1,2) of SU(4) x SU(2)_L x SU(2)_R, which is parity invariant. (Note that parity exchanges the left and right handed
SU(2)’s.)
In Distler’s post he asserts to the contrary that in the Pati-Salam model the fermions are in the representation he calls R_ps= (4,2,1)+(4-bar,1,2) of SU(4) x SU(2)_L x SU(2)_R, which is not parity invariant. (Parity changes this to (4,1,2)+(4-bar,2,1) which is not equivalent to R_ps.) This disagrees with what is stated in the above paper, by the omission of a single bar. This small change has a major impact on the discussion because it turns a parity symmetric theory into a parity non-symmetric theory which is not the Pati-Salam model.
It seems to me this invalidates Distler’s discussion of Pati Salam and by extension suggests that his second post on Lisi is incorrect. While Lisi’s scheme is not quite the same as the above, because the electroweak gauge symmetry is unified first with local lorentz, then with G2, the moral is the same because Lisi breaks E8 to a version of electro-weak unification which is parity symmetric. This is ok for the same reason Pati-Salam is ok, because parity can be broken spontaneously.
Thanks,
Lee
Ps to HIGGS.
One does not need a special extension of parity to switch SU(2)_L with
SU(2)_R, because they couple to left and right handed currents in the usual sense, so parity switches them. And, in case there is any confusion, the above discussion is not affected by any terminological confusion as to the meaning of chiral.
I am afraid that you are, indeed, confused.
Start by writing everything in terms of left-handed 2-component Weyl fermions (whose Hermitian conjugates are right-handed Weyl fermions).
The quantum number of a generation of fermions are as I stated in my post (and as can be confirmed by a myriad of contemporary sources). To check, it suffices to look at what happens when you break the Pati-Salam group down to the Standard Model gauge group to see that what I wrote down give the correct Standard Model content, and that what you wrote down does not.
In fact, the representation you wrote down is anomalous, so could not possibly be correct.
H-I-G-G-S stated the distinction between Parity and Chirality correctly. The names of the two SU(2) groups in Pati-Salam are just names.
Lee,
The discrepancy is quite simple to explain.
In the Pati-Salam paper what they say is
that psi_L is in the (2,1 bar 4) and psi_R in the (1,2 bar 4). It is common
in the study of grand unification to write all fermions as left-handed fermions.
psi_R^*, after multiplication by a suitable matrix, is left-handed. Let us
call it psi’_L. We then have
psi_L: (2,1, bar 4)
psi’_L: (1,2, 4)
Note that complex conjugation does not change the SU(2) rep because the
2 is pseudo-real. The representation in which all fermions are left-handed is
the one that Jacques was correctly using and it agrees with Pati-Salam.
The relevance of the reality of the representation when written this way
is that a real representation allows a gauge invariant mass term whereas
a complex one does not. I’ll let you be the judge of your own opacity.
SY,
H
Jacques,
You are claiming 1) that the original Pati-Salam paper I refer to is incorrect about what their own theory is and 2) even though their big point is that the fundamental dynamics could parity invariant that they should have based the model on a parity non-invariant representation (4,2,1)+(4-bar,1,2) instead of the parity invariant one they specify?
Ah, I see Jacques beat me to it by a few minutes. In fact I did not see his post
before writing mine. Perhaps the extra pedagogical details I provided will be useful to those following along at home.
Lee,
Read my post (#104). Take a deep breath. Think. Jacques agrees with
PS. He is simply using a basis in which all fermions are left-handed. PS are
not. But they have exactly the same degrees of freedom and are
describing the same theory. If you are unfamiliar with the fact that psi_R^*
is left-handed you might want to take a look at the chapter on fermions
in any modern book on quantum field theory.
H
Dear HIGGS
I see, if it is then just a terminological mixup that is of course fine for this issue. I don’t mind making mistakes in public-the time spent studying the Pati-Salam papers was my own and in any case worthwhile-but this shows to me the difficulty of arguing technical issues in the blog environment. Perhaps the experts could find a better way, probably off line, to go through the issues with Lisi point by point and reach a conclusion over the main issues. If so I’d be happy to be involved, so long as everyone involved was patient and professional and no one pretended that the representation theory of non-compact forms of E8 is child’s play.
Thanks,
Lee
Dear Lee,
I’m glad that we cleared this up, and I appreciate that you admitted error,
in line with your earlier posting on the spirit of science requiring such acknowledgement. I don’t quite agree however that it was a “terminological mixup.” This makes it sounds like there was no real content to the debate, whereas in fact there was. The issue at hand was whether or not Lisi’s embedding contains the Pati-Salam model or not. Jacques showed that it does not. All I did was to provide some helpful clarification. In an earlier post you went on about how “Distler was largely wrong” and so forth, while as far as I can tell, everything he has said has either been correct, or when it was in error, the error was admitted and then clarified. Thus it would be much more appropriate for you to address your admission of error to him than to me. Perhaps if you did so his responses to you would in the future be more temperate.
It is true that blogs are far from the best place to argue technical issues. This discussion was one of the happy exceptions where a point was argued and resolved with all parties in agreement. As for Lisi’s proposal, I believe a conclusion has been reached by the experts.
H
Of course, I cannot follow the technicalities of this exchange, but I couldn’t help noticing
#109 H-I-G-G-S comments were riddled with contradictions of a non-technical nature. These comments do not form an internally consistent collection of beliefs.
Dear HIGGS,
Thanks for your kind words, but wiith respect, this resolved only the point I queried. I have more technical questions about missing steps in Jacques’s arguments which would need to be filled in before I understand it. Rather than raising them in this forum, since you seem to understand the argument, if you email me I’d be glad to discuss them and have you straighten me out, then we can report back our aggreement on the whole issue. Let me make a similar offer to anyone who understands the argument in question and thinks it is correct.
Thanks,
Lee
Dear physics neophyte,
In the words of one of your earlier postings, wtf?
Dear Lee,
I’m afraid I’m going to decline your invitation for further discussion via email.
I don’t think Lisi’s proposal is worth pursuing, and don’t wish to spend time explaining group theoretical details when I could be doing other more interesting things. I’m sure you have colleagues who could assist you in these matters.
H
Dear Vincent #101:
I too think that there is too much emphasis on competition in comparison to collaboration. One needs both, but in a field where sharing information is essential for progress, too much competition is fatal. I mean, it’s not like we’re trying to bake the pizza that sells best in the neighborhood. The ‘American Competitiveness Initiative‘ shows who’s still living in the last century.
Since our goal is still a collaborative goal of trying to understand the world, and while someone may think a person is arrogant, he may still have good ideas that are worth looking at (this has happened so often in the history of science…). Do you agree?
I mostly agree with you. I just think we’re tolerating too much arrogance.
I don’t know how many people I’ve meet who carry this certain type of condescending superiority that makes it very clear it is below their status to explain anything, and you are labeled ‘stupid by default’. It is a small surprise that little people consider this to be encouraging. Competition pairs well with arrogance.
Whether we like it or not, these people set an atmosphere in our field – exactly for the reason that they are, as you say, louder. And this atmosphere does a selection among those who want to be part of the community. I’ve had quite a number of friends (both male and female) who at some point decided all their love for physics isn’t worth the constant fight, annoyance, and lacking respect.
Should add though I don’t think this is special to the blogosphere, it just reflects there.
Best,
B.
B,
Some people thrive when they are challenged/insulted intellectually and use it as motivation to understand things better. Others just ignore it, and are more motivated by natural curiosity. Whos to say which paradigm works better, realizing many famous names in the history of physics have had success with that attitude (see eg Isaac Newton)
I guess its akin to trash talking in proffessional sports, where people do it for those reasons. Anyway, if it makes them output better physics and work harder, fine I have no problem with it. Ultimately thats what matters most.
H-I-G-G-S:”This makes it sounds like there was no real content to the debate, whereas in fact there was… This discussion was one of the happy exceptions where a point was argued and resolved with all parties in agreement.”
No. The debate was pointless. Come on, guys! Do you intend to start doing physics?
Regards, Dany.
Haelfix said
“Some people thrive when they are challenged/insulted intellectually and use it as motivation to understand things better. Others just ignore it, and are more motivated by natural curiosity. Whos to say which paradigm works better, realizing many famous names in the history of physics have had success with that attitude (see eg Isaac Newton)
I guess its akin to trash talking in proffessional sports, where people do it for those reasons. Anyway, if it makes them output better physics and work harder, fine I have no problem with it. Ultimately thats what matters most.”
Haelfix, I have a colleague who strongly agrees with you. As a consequence, his son jumped out of a very tall building. My colleague has shown no remorse, and has not changed his views or his ways.
There is nothing positive about such bullying, and there is no excuse for condoning it.
Pingback: Competitive Cycle « Theorema Egregium
*lol* bullying victim, this is so sad I even feel bad for laughing about your sarcasm. as a fact I know a very similar story (the son survived though with both legs broken, I guess he wasn’t sufficiently intellectually challenged ).
Haelfix, you kind of miss my point. I know there are people who “thrive when they are challenged/insulted intellectually and use it as motivation to understand things better.”. But then those are the ones you keep, and you bully out the others. I see no reason why good physicists are exclusively found with the type of personality you describe. This means the community misses a lot of good people who are, depending on personality, either disgusted or discouraged, and leave the field or chose a more welcoming community. Best,
B.
Haelfix and B discussed the “trash talking” “bullying” atmosphere in the physics community, and B said that such an “… atmosphere does a selection among those who want to be part of the community. I’ve …[B has]… had quite a number of friends (both male and female) who at some point decided all their love for physics isn’t worth the constant fight, annoyance, and lacking respect. …”.
I have also seen brilliant people who are not in physics but who might have been had the community been “nicer”.
As for why I do what I do, I am, to quote Haelfix “motivated by natural curiosity”, but I am not able to do as Haelfix suggests and “just ignore it”, and consequently I run up psychiatric bills for depression (primarily therapy rather than drugs) and I probably don’t get as much physics done as I would in a cooperative environment,
and I have probably paid a price in my personal life for trying to indulge in my “natural curiosity”.
Yes, pursuing “natural curiosity” in the face of “trash talking” and “bullying” is a choice I have made, but it has been forced on me by the atmosphere of the physics community, and in a cooperative world it would not have been necessary to make such a choice.
Tony Smith
PS – An example of “nice cooperative” behaviour would be if H-I-G-G-S would state (clearly and in detail enough that Lee Smolin could explicitly agree or point to error and disagree),
about Lisi’s proposal, exactly what is meant by H-I-G-G-S’s statement:
“… a conclusion has been reached by the experts …”.
For example:
is Garrett’s E8 Pati-Salam idea OK,
or
is there a technical flaw that can be fixed by making changes (maybe by using something other than Pati-Salam)
(after all, the superstring community has been fixing up its models by making changes ever since back in 1985 when Schwarz’s original SU(5) proposal was refuted)
or
is the entire E8 program irretrievably lost for some reason ?
PPS – As to people saying that Garrett Lisi’s title was inappropriate,
what about the title Schwarz and Hamidi used for their 1984 APS DPF presentation of superstring theory:
“A Unique Unified Theory That Could Be Finite and Realistic” ?
In that paper, they said
“… The three-loop calculation could result in culd result in a dramatic failure or success and is therefore of utmost importance …”.
Within a year, the three-loop calculations were done and the result was in fact “dramatic failure”,
however
they did not abandon superstring theory, but began to modify it (for example, in those early days, by introducing flipped SU(5), etc).
Shouldn’t Garrett Lisi’s E8 model be given the same freedom to make modifications, and not entirely be trashed just because the exact Pati-Salam part might not work ?
Haelfix, as someone who was repeatedly burnt with “intellectual challenges” (what a charming euphemism) I can say for sure that it didn’t make me a better or more determined/motivated physicist. It’s effect was simply to make me avoid famous or well-known physicists like the plague whenever they visit a department i’m in; more generally to avoid discussing physics with anyone who isn’t specifically interested in what i’m working on, and to decide that, as far as physics goes, the only people whose opinion i give a damn about are the editors and referees of Physical Review Letters (and other journals as well, to a lesser extent). Not much positive in that.
However, in the present case I think J.D. and others have been remarkably restrained and polite considering the circumstances. (As an illustation of the “circumstances” see the quote from the Economist in #47 above.) The only thing I didn’t understand was J.D.’s slamming of Bee (in the comments of his post) which just seemed mean and pointless, especially considering that Bee had done a much better job of analyzing the physics of Lisi’s proposal (modulo the group theoretical stuff) than Lubos, but Lubos didn’t get slammed…
Somehow I suspect “Haelfix”, “H-I-G-G-S” and others like them might show a lot less enthusiasm for “trash-talking” and “bullying” other physicists if they weren’t doing this from behind the cover of anonymity. One can argue about whether the emotional environment at the scrimmage line of a football game is a good way to do science, but I think it’s pretty clear clear what a professional football player would do to someone who tried to “trash-talk” and “bully” them while hiding their identity.
Dear Tony et. al.
My apologies if I came off as bullying. It was not my intent. I was
put off by Lee’s attack on Distler’s credibility (read his first post) and so my replies were on the forceful side since it seemed to me clear that Distler was in fact correct.
I have only spoken to a few “experts” on the Lisi proposal, so let me simply say that I don’t think the proposal has much merit. The reasons include
1) It does not contain the standard model fermions in a chiral rep. In fact it contains fermions in real reps, so they will presumably have large masses
and one will not get the chiral structure of the SM.
2) It mixes bosons and fermions with some talk about BRST but no definite proposal about what the mathematical structure is that lies behind this. For exampe, are the physical states defined by BRST cohomology classes?
3) He has nothing new to say about dynamics so I expect the theory to be
non-renormalizable, to the degree the theory is even defined.
4) He starts with all couplings equal but does no RGE analysis to see whether they take reasonable values at low-energies. This seems unlikely since the
low-energy couplings do not unify without superpartners or some other
new structure at low energies.
5) The E8 symmetry is not a symmetry at all since there is no limit proposed
in which it is restored.
And so on and so on. In brief, I don’t see anything new and promising in his proposal. I of course have no objection to him or others trying to develop it to the point where it does contain something new and interesting. But he and others should be expected to defend their work in the face of criticism. That’s how science works.
Dear Peter,
Once again, I am not anonymous. I have a pseudonym. Earlier you pointed
me to a posting by Bee on this precise topic where she was quite positive about the use of a pseudonym as compared to anonymous postings. I’m trying to be
nice here, I’m not “trash-talking” and I’m trying to be helpful by making correct statements about physics. Please do the same.
H
Hi Tony:
Thanks for your comment. I am sorry to hear about your unhappiness with the work environment. Sadly, I have heard remarks like this very often 🙁 Usually only by younger people, grad studs, postdocs. Those who can’t stand it, leave, meaning we are at the senior level left with a majority of those who find it okay and see nothing wrong with it. I mean, here is a typical example (particle physics community) that I’ve seen repeated in various shades: young researchers about to finish his/her PhD gives first seminar, is obviously terribly nervous (well, he’s seen what others had to go through). Is interrupted already on the first slide, to be told everything he’s done is useless and uninteresting, and his adviser doesn’t know nothing. Upon which an argument develops between the person asking and the advisor, an argument that has been repeated a million times, only little people can follow the details, and nobody actually wants to hear it. Ten minutes later, the student manages to proceed to slide two, where he’s being told to move ahead because everybody knows that stuff. So he flips through the introduction to some results, only to hear a couple of incredibly stupid remarks caused by the fact that he didn’t have a chance to explain what he was doing. He tries to answer politely, but the only result is senior people shooting questions at him until he’s out of answers, and completely destroyed. In the best case, he has a good advisor who will protect him. That’s not a single sorry story, that’s the way I have seen it happening over and over and over again, in seminars, group meetings, and on conferences (parallel session of course), etc. It’s like all these people just want to show off with several decades more experience.
Reg Lisi’s title, I too found it inappropriate, but you are of course right that there are more examples like this. These usually don’t make it into the media though, so in most cases it doesn’t really matter what you title a paper on the arxiv. As I’ve argued in the comments above and here, I think we still need to learn how to live with such media attention and how to be appropriately careful and precise. What I think is likely to happen though is that now people are pointing out the problems and the flaws of his proposal, that can be done rather fast. It takes more time though to figure out whether it can be worked out, or which features of the model can be useful etc. As so often, constructive criticism requires more effort than the destructive sort. I hope that despite all the hype, Garrett has found some people who’d be interested in investigating the direction he is looking into.
Best,
B.
Tony Smith says:
“PS – An example of “nice cooperative” behaviour would be if H-I-G-G-S would state (clearly and in detail enough that Lee Smolin could explicitly agree or point to error and disagree),
about Lisi’s proposal, exactly what is meant by H-I-G-G-S’s statement:
“… a conclusion has been reached by the experts …”. ”
As far as I understand, this is precisely done in Distler’s second post, where he shows that Lisi’s embedding of a generation of fermions does not seem to be correct mathematically (whitout using any physics argument, this is a purely technical group theory argument). I think Distler’s post is also pretty clear and well written and should be understandable for people willing to go through it in detail. Then, if they have further questions there is a comment section there that can be used. That seems like all that is needed at the moment, right?
With respect to fixing the mathematical mistake by making modifications to the theory, well people interested in that may indeed look for that, and it would of course be very nice if they find anything interesting. On his side, Distler has proposed his own conjecture (in an Appendix to his first post) where he proposes that all embeddings in E8 will be non-chiral, in which case unification of all fields in E8 as proposed by Lisi would not seem to be very useful, or at least much more important modifications to his work would have to be done to make it interesting. Proving (or disproving) this statement is something that people interested in Lisi’s idea may want to work on.
As for the title of Lisi’s paper, there has been obviously plenty of overstatements and hype in previous titles in the history of science, which in no way justifies keeping doing the same thing, if we are honest about wanting the field to change for the best. It is simply a clear overstatement to call a paper a Theory of Everything from a start, which is bound to attract unwanted and unnecessary media attention before the theory has been looked at by peers in the science community.
Best 🙂