Garrett Lisi has a new paper on the arXiv with the rather over-the-top title of. Sabine Hossenfelder has a typically excellent about the paper and Garrett has been discussing his work with populate in the comment divide there. Lubos Motl has a typically how shall I say. Lubosian on the topic.
I’m the first person thanked in the acknowledgment section of the paper but at Sabine’s blog Garrett explains that this is just because he is using reverse alphabetical order. I’ve corresponded with him in the past about his research in this area without being able to provide any real help other than a certain amount of encouragement. Two of the ideas he is pursuing are general ones I’m also very fond of. One is well-known and many populate undergo also tried this it’s the idea of bringing together the internal calculate symmetry and the symmetry of local frame rotations. The problems with this are also well-known and some have been brought up by the commenters at Sabine’s blog. I don’t evaluate Garrett has found the answer to this or that he claims to. I’m still hopeful that this line of thinking ordain lead somewhere but think some dramatically different new idea about this is still needed. The other idea he likes is that of trying to understand the fermionic degrees of freedom of the BRST method for handling gauge invariance as providing the fermions of the Standard copy. I suspect there is something to this but to get anywhere with it a much deeper understanding of BRST will be required. I’ve been spending a lot of time trying to understand some of the mathematics related to BRST in recent years and am in the lay of writing some of this up. It seems to me that there is a lot that is not understood yet about this topic change surface in much simpler lower-dimensional contexts so we’re a desire way from being able to really see whether something can be done with this idea in a realistic four-dimensional setting.
While there may be some sort of ultimate truth to this the problem is that just as for GUTs and for superstring models all you’re doing when you do this is changing the unification problem into the problem of what breaks the large symmetry. This change in the problem adds some new structure to it but just doesn’t seem to help very much with the bottom lie being that you get few if any testable predictions out of it (one exception is with the simplest GUTs where you do get a prediction proton change integrity which turns out to be do by falsifying the models).
Anyway. I’m glad to see someone pursuing these ideas even if they haven’t go up with solutions to the underlying problems. Garrett is a serious and competent researcher who has pursued a non-traditional go path and was recently awarded a give to by the FQXI organization. You can construe more about him in an on their web-site.
Unfortunately some of the reaction to Garrett’s bind has been depressing. A commenter who sounds well-informed but hides behind anonymity goes on about “this nonsense” (although Garrett’s polite reaction to him/her did lead to a more sensible discussion). Early on in my experience with blogs I believed that no serious professional in particle physics would contend someone and try and carry on a scientific argument anonymously so any such comments had to be coming from misguided students or someone not in the profession. Unfortunately I’ve all too often seen bear witness that I was wrong about this. Lubos Motl on his blog denounced the fact that Garrett’s cover appeared in the hep-th section of the arXiv then later wrote in to Sabine’s blog to blow that it had been removed from hep-th. As always with the arXiv how moderation occurs there is non-transparent so I don’t experience how or why this happened. My own undergo with the arXiv over trackbacks to hep-th has been a highly disturbing one. The current hep-th policy seems to be to allow any sort of nonsense to be posted there if it fits into the current string-theory-based ideology (see for example ) while suppressing any criticism of this. A paranoid person might be tempted to wonder whether hep-th is being moderated by someone so ideological and petty that criticism of string theory or including string theory critics in an acknowledgment divide would be create for having ones bind removed from hep-th…
Update: I comprehend from Garrett that the story of this paper at the arXiv is that it was submitted to gr-qc not hep-th. Before it was posted it was re-classified as hep-th and appeared there. Later on (after the appearance of Lubos’s communicate entry denouncing the arXiv for allowing the cover on hep-th I believe) it was re-classified again this measure as general physics (with cross-listing to hep-th).
modify: Latest news about this is that the paper has now been reclassified again to the perfectly appropriate hep-th cross-listed as gr-qc although no one seems to experience why this happened. Another continuing mystery is the trackback situation: there are four trackbacks to the cover to postings by Lubos. Bee and to Physics Forums as well as to an old TWF from John Baez that doesn’t change surface cerebrate to the cover. My postings comfort seem to be non-trackback worthy on hep-th not that I can argue with this particular case since the discussion elsewhere has been more substantive (except for Lubos’s which is valuable for the way it accurately represents the hysterical reaction to speculation that is not string theory speculation all too common in certain quarters).
Update: Garrett is making the news Whether this is a good thing is yet another question for debate on the next thread. I guess. A lot of the attraction for the media seems to be his personal story. Maybe it’s a good thing for physics for people to see that one can be a theoretical physicist while surfing in Hawaii…
Hello Peter,This is a well thought out post as usual. I did believe our short emails — and the very existence of you and this communicate — encouraging enough to consider you in the acknowledgments. Your concerns are all valid and are some of the same concerns I discuss in the paper. Though I do evaluate the way I’ve combined the gravitational frame-Higgs and used the MacDowell-Mansouri description of gravity is new. You are correct that I don’t have a good cerebrate or mechanism for what breaks the E8 symmetry and this is needed. What I’ve done is break the symmetry by transfer including the few terms necessary to recover the action of the standard model and gravity. I am biased towards E8 because of its beauty and similarly towards the general idea of unification. The success of electroweak symmetry breaking in the standard model is compelling bear witness that symmetry breaking of this choose plays a very important role in nature and I’m surprised you dislike the idea of applying this on a larger scale. Surely you acknowledge that successful predictions from electroweak symmetry breaking indicate it did more than just add new coordinate to the problem? In any inspect. I am very much looking forward to reading your bring home the bacon on BRST as it’s a very complicated and fascinating subject and it plays an important role in this E8 theory that I’d desire to understand exceed.
By “adding new structure” to the problem I meant to imply something not negative but potentially positive. The new structure may be usable to bound things and thus allow non-trivial predictions. If you are using a scalar field to do the breaking then the question becomes how constrained this set-up is. In the electroweak theory the Higgs sector on the one transfer fits in well with the symmetries of the theory and has a limited be of free parameters but it still has quite a few and is the main source of the problems of the Standard copy. Because of this situation. I’ve always been most interested in ideas about unification that tell you more about the Higgs not so much in ideas that don’t do that but add other Higgs sectors.
That’s my prejudice but sure starting from other reasonable prejudices like the desire for a hit simple group to act on everything may bring about one somewhere. Maybe you’ll undergo better luck than the GUT program which hasn’t been successful so far.
In terms of just the pure math here– the one thing I’m at least superficially in a place to mention on– what Garrett’s doing with breaking down E_8 into the various gauge groups we’d need to exposit reality seems to make sense. Where I get lost is in trying to understand how you use this model to express us something about the physical world (maybe Garrett’s believe of E_8 would be obviously useful or obviously unsuitable for this to someone with a good understanding of what the gauge assort “does” in a gauge theory but that person is not me). Can you help me understand what the physical significance of some of this stuff is or might be assuming some understanding of what the groups themselves are doing?
I convey so you’ve shown it looks like that E_8 can be decomposed into SU(3)xSU(2)xU(1)xSO(3,1)xHiggsxFermion. The mere fact that this is possible does be suggestive of something. What do we gain however from describing all of these fields as the one big E_8 group– you know rather than just leaving all those component groups displace with their own yang-mills theories and such (or perhaps just awkwardly x-ing them together like we do to fasten up SU(3) to everything else in the Standard copy)? How does the unification of all these groups dress things?
I’m meanwhile somewhat confused as to the physical significance we are meant to act from the various features of E_8’s structure. I’m particularly baffled by what to make of the big grow draw which is shown in the video Bee links and in various ways in the cover. What does it convey for two roots in this draw to have an edge between them? If I’m not mistaken (er am I?) then from a mathematical perspective an edge between two roots in the E_8 root system polytope corresponds to the lie bracket between those two roots. But what does this mean physically when we use E_8 as Garrett has here?
Also what is the meaning of the “rotations” of the root system shown in the paper and the youtube video? Do these rotations be to anything physically meaningful or are the rotations just showing the root system diagram in different ways to make the different groups the system breaks drink into visually clear?
Meanwhile if elementary particle fields correspond to roots in Garrett’s gigantor calculate group then what do products of those roots physically be to? The paper says “The interactions between all standard copy and gravitational fields be to the Lie brackets between elements of the E8 Lie algebra and thus to the addition of E8 roots.” Hm okay so additions of E8 roots produce interactions between? What are those “interactions”? Or is this specified by the yang-mills action or something?
Also a little confused: so counting up all the fields we evaluate to see in nature we find they fit with 222 of the roots in your E_8 grow system leaving 18 “extra” roots whose properties as fields are described on page 22 of the paper. The paper seems to be saying that these 18 new fields each act kinda desire the Higgs and each one is identified with a specific one of three generations and a specific color or anti-color. If this reading is correct what do these generation/alter identifications have in mind to? Does this have to do with the color or anti-color of quark that the field is able to interact with or is the idea that the field carries color charge or…?
One more general possibly dumb question is there any potential form of correspondence which one could draw between how E_8 is used here and arrange theories which use E_8 (or products of E_8) as a symmetry assort? Or is the usage of a “symmetry group” simply too different in these different contexts?
1. Yes the Coleman-Mandula theorem assumes a background spacetime with Poincare symmetry but this theory doesn’t undergo this background spacetime — with a cosmological constant the vacuum spacetime is deSitter. So this theory avoids one of the necessary assumptions of the theorem and is able to unify gravity with the other gauge fields. On small scales though. Poincare symmetry is a good approximation and on those scales gravity and the other gauge feels are separate in accordance with the theorem. (I’m not the first person to dodge C-M this way.)
(1) The first person I experience of to point out this loophole in Coleman-Mandula was Thomas like (a visitor here) in his 1987 dissertation. There is also a discussion of this loophole in this recent cover by F. Nesti and R. Percacci: . Or you can go to the obtain and look at Coleman and Mandula’s in which their first condition for the theorem is “G contains a subgroup locally isomorphic to the Poincare group.” The G = E8 I am using does not include a subgroup locally isomorphic to the Poincare group it contains the subgroup SO(4,1) — the symmetry group of de Sitter spacetime.
(2) I’m banking on the LQG community to change this one. So calculate the odds of this E8 Theory being right times the odds of LQG finding the alter answers for quantizing the theory… and I’m first to adjudge it’s a desire shot. But I think it’s got a chance which is why I work on it.
Hi create verbally,Peter teaches classes in representation theory so he can say most of these questions better than I can but I can at least help out with what’s in this paper. You undergo a correct understanding of what’s going on so I’ll just answer your specific questions.
“What do we gain however from describing all of these fields as the one big E_8 group– you know rather than just leaving all those component groups displace with their own yang-mills theories and such (or perhaps just awkwardly x-ing them together desire we do to hook up SU(3) to everything else in the Standard Model)? How does the unification of all these groups dress things?”
Because all these fields are parts of E8 we can assemble an E8 principal bundle connection (technically a superconnection) which consists of 1-forms and Grassmann fields valued in this E8 Lie algebra and use the curvature of this big connection to get the dynamics. The curvature in the action determines how E8 interacts with itself. And since everything is move of E8 this corresponds with how all the fields of the standard model and gravity interact with each other. This action is built by hand to match the standard model which is an inadequacy of the theory but it’s very concise. And I evaluate it’s cover amazing that this works at all.
Physically as this theory develops it should make definite predictions for the coupling constants predict a handful of new particles and some non-standard interactions and (if things go astoundingly well) undergo something to say about the particle masses. These predictions may end up being do by killing the theory but so far things are looking good.
The root diagrams correspond to the structure of the Lie algebra. If two E8 roots add to give a third (in eight dimensional Euclidean root space) then the Lie bracket of the corresponding two Lie algebra basis elements give the third. In the paper. I describe which roots correspond to which elementary particles. Also since the projection used to plan the eight dimensional grow system is linear you can determine particle interactions by adding these roots together as two dimensional vectors extending from the origin — it’s fun try it. This is standard representation theory and it’s very pretty. In my opinion. Peter doesn’t push his own affect hard enough — I desire I had learned about this stuff earlier than I did it’s wonderful.
Yes the addition of the roots corresponds to the Lie brackets between fields which is in the curvature which is in the challenge and this gives the interactions between particles appearing as Feynman vertices in QFT calculations.
“these 18 new fields each act kinda like the Higgs and each one is identified with a specific one of three generations and a specific color or anti-color. If this reading is correct what do these generation/color identifications have in mind to? Does this have to do with the color or anti-color of quark that the field is able to interact with or is the idea that the field carries color rush or…?”
Yes exactly so. These new scalar fields have color quantum numbers and so act with the quarks and gluons. In my dreams at night these new Higgs fields furnish the CKM matrix but I don’t know how that works when the sun comes up. They’re also a potential dark be candidate but I don’t say that in my paper because I evaluate that’s a cliche.
“is there any potential form of correspondence which one could draw between how E_8 is used here and string theories which use E_8 (or products of E_8) as a symmetry group? Or is the usage of a “symmetry group” simply too different in these different contexts?”
They are completely different theories which happen to use related Lie groups. I could list many specific differences:non-compact E8 vs compact E8 x E8gravity in E8 vs gravity via otherfour dimensional spacetime vs 11 dimensional spacetime with Kaluza-Klein orbifold compactificationsprincipal bundle connection vs strings branes and who knows whatetc.
The Coleman-Mandula theorem applies to “All Possible Symmetries of the S-Matrix” the title of their cover. The S-matrix formalism is based on particle democracy there are no fundamental particles. In “The Geometry of Elementary Particles” my 1987 dissertation which Garrett mentioned there are truely elementary particles and the S-matrix formalism is not valid hence the Coleman-Mandula theorem is not applicable. I use U(3,2) as the symmetry of a complex spacetime by passing the no-go theorems (which cerebrate to the Poincare group).
“… The proof of the Coleman-Mandula theorem … makes it clear that the list of possible bosonic symmetry generators is essentially the same in d greater than 2 spacetime dimensions as in four spacetime dimensions:… there are only the momentum d-vector Pu a Lorentz generator Juv = -Jvu ( with u and v here running over the values 1. 2. … d-1. 0 ) and various Lorentz scalar ‘charges’ …the fermionic symmetry generators furnish a representation of the homogeneous Lorentz group … or strictly speaking of its covering group Spin(d-1,1). …The anticommutators of the fermionic symmetry generators with each other are bosonic symmetry generators and therefore must be a linear combination of the Pu. Juv and various conserved scalars. …the general fermionic symmetry generator must alter according to the fundamental spinor representations of the Lorentz group … and not in higher spinor representations such as those obtained by adding vector indices to a spinor. …”.
In short since E8 is the sum of the adjoint representation and a half-spinor representation of Spin(16),if Garrett builds his model with respect to Lorentz spinor etc representations based on Spin(16) consistently with Weinberg’s bring home the bacon,thenGarrett’s model could well conform to Coleman-Mandula.
A paranoid person might be tempted to wonder whether hep-th is being moderated by someone so ideological and petty that criticism of string theory or including string theory critics in an acknowledgment divide would be cause for having ones article removed from hep-th…
“Yes exactly so. These new scalar fields undergo color quantum numbers and so act with the quarks and gluons. In my dreams at night these new Higgs fields give the CKM matrix but I don’t know how that works when the sun comes up. They’re also a potential dark be candidate but I don’t say that in my paper because I think that’s a cliche.”
If your dark matter candidate has alter quantum numbers it should interact strongly with ordinary matter. In MSSM the dark matter candidate is typically a neutralino. In some models it’s a sneutrino. So in either case it only couples gravitationally - that is why it is referred to as a dark matter candidate. So if some construction predicted say a gluino LSP (which is strongly interacting) that would be a disaster.
One should be able to set up certain fixed situations in which a graviton can be derived as an approximation. But the graviton should not exist in the theory as a fundamental descriptor. If it does exist then the theory would not be fundamental–according to what Renate Loll says.
Given my rather boring lifestyle I evaluate about becoming a ghost writer and hire someone to market my papers with a better story! Anybody could please point me towards a 30something color male single good-looking US citizen who has an interest in extreme sports of whatever kind grew up under difficult circumstances (but doesn’t experience from an embarrassing evince) good socializing skills likes to communicate in front of people does come up on TV preferably works in a patent office or likewise speaks Spanish and French fluently and well has maybe taken some physics classes in high educate?
One should be able to set up certain fixed situations in which a graviton can be derived as an approximation. But the graviton should not exist in the theory as a fundamental descriptor. If it does exist then the theory would not be fundamental–according to what Renate Loll says.
Hm while I can see attractive aspects to that approach that kind of sounds like a dramatic step to take. Do there already exist any other theories of quantum gravity besides Loll’s which avoid the graviton or act the “graviton as approximation” come you exposit?*
Meanwhile I sight Loll’s argument in the paper you cerebrate against the graviton somewhat unconclusive. “Well we’ve been trying to get useful answers out of this create for decades and haven’t succeeded so it’s a good bet we’re doing something wrong” sounds like good strategy to me but he doesn’t be to actually be putting forth an argument about reality there only an argument about “how to proceed”. I don’t see any reason that just because we can’t exposit the graviton perturbatively that would mean it doesn’t exist– since as far as I understand perturbation theory is supposed to just be an approximation anyway. (And this is of cover assuming that perturbatively modeling the graviton is impossible and not just too hard for anyone to manage right now). Am I missing something about Loll’s argument?
* Does LQG for example have a graviton? Looking I am finding references to a “graviton propagator” in LQG but it is not immediately obvious whether that’s the same thing.
P. Woit: “One idea Garrett is fond of that has generally left me cold is the idea of unification via a large simple Lie algebra like E8. While there may be some sort of ultimate truth to this the problem is that just as for GUTs and for superstring models all you’re doing when you do this is changing the unification problem into the problem of what breaks the large symmetry. This change in the problem adds some new structure to it but just doesn’t seem to back up very much with the furnish line being that you get few if any testable predictions out of it (one exception is with the simplest GUTs where you do get a prediction proton decay which turns out to be wrong falsifying the models).”
I adjudge that I didn’t read the paper. However in my view all that PR tararam have very positive outcome: it again attract the attention to the Cayley numerical system which seems to be the natural candidate for QG and unification of all fundamental interactions. Since the connection with the GR and relativistic QM is the necessary constraint one should define the real octonion valued self adjoint operators. My own experience with them is that it is exceptionally not simple problem (indeed change surface the solution will be far from being theory of everything).
This physics-related pressure was at least as important for me to leave those circles as the purely political issues about the academic freedom because I became pretty much certain that all these things would be getting worse as time goes.
When I was first suggested by relatively powerful people that I should have been treating complete idiots such as Peter Woit as my peers if not more it was just way too much for me. We may be create from raw material that the society may misevaluate many things nothing is perfect but these things are just many orders of magnitude out of proportion.
What about next. I would be thinking. Would cranks with their ‘theories of everything’ who experience less than 1% what I do and whose IQ is 45 below exploit - literally an inferior species - would be placed upon us or change surface dictate what we can think about physics? Well this epoch just here. It has become politically incorrect to say that what surfers like Garrett Lisi are doing are lighten years away from what theoretical physics is. The closer one is to the top of the real physics the most impossible it is for him or her to say any opinions. With a realistic idea about psychology and social science where do you evaluate that the society will be going if the relative influences are arranged in this way?”
1. The press stories aren’t awful with reporters mostly trying to include some skeptical comments about how speculative this is while at the same time as much as possible making an enthusiastic story about the latest “theory of everything”. Unfortunately for reasons I inform in the latest posting here. I think these kinds of stories don’t really do much in terms of explaining what is really going on to people often giving a misleading impression.
2. Comments on Slashdot and the blogs are all too much dominated by the huge number of people who evaluate it is a good idea to write in about things they don’t understand happily spreading misinformation or irrelevancy and burying serious comments under a mountain of junk. The noise to signal ratio on Slashdot is so high that very few populate who actually know something about this subject are willing to waste their measure reading the comments or trying to alter to the discussion. Too many comments on this blog and on others come from people who don’t actually know much about the topic at hand but conclude compelled to share whatever is on their object anyway.
3. Some blogs and commenters try and fit this into the ongoing string theory/LQG warfare which it isn’t especially relevant to. As usual Lubos can be counted on to obscure whatever sensible criticism he might undergo with crazed rants about how populate who aren’t string theorists are lower life forms.
Blogs do sometimes bring home the bacon to provide a displace for some sensible discussion even amidst a heavy helping of nonsense. In this inspect the beat I’ve seen is Sabine’s communicate which has provided a forum for Garrett to discuss some of the issues raised by his paper in detail with her and others.
I agree with Garrett that this is a very exciting measure. Congratulations to him on getting some very interesting and compeling work out. It’s encouraging me to take a end from dynamical coulped-channel approach to meson production reactions to have another look at some issues of GR that I’ve thought about in the past.
Curiously the question of renormalization doesn’t appear to be getting too much play here. It seems that while the E8 unification proposed could understand some issues of organization the fundamental issues of spacetime properties and particle properties comfort remain distinct. Garrett’s bet that LQG will solve this issue is probably not all that much of a sucker’s bet. It seems desire accent independence will be a key concept in the resolution — to me anyway.
But that’s only “half” the problem. There seem to be two issues regarding renormalization. The non-renormalizability of GR has already been mentioned. But also circle integrations will apparently still lead to divergences in the E8 unification — the theory enjoys no supersymmetry cancellations for example. Then we’re stuck with infinite renormalizations — fine we’re used to it. And physics can comfort be done. But the precision required to fix the couplings will make. I fear accurate detailed predictions impossible. Spectroscopy alter still be possible however.
Regarding the pun: It might be perfectly obvious to everybody who works in theoretical physics but I doubt many populate of the broader public or even the journalists got it. Was it explained anywhere than here? I am constantly making terrible puns desire this which is always source of a broad confusion. But besides this it’s somewhat unfair to blame things on the title there are other examples (testing quantum gravity! testing arrange theory!) that go the same way. It’s probably a consequence of of populate’s sensitivity to news change state lower and lower because there’s such an over flow of unbalanced hypes that needs to be filtered (not only in science). It’s a very bad turn though. I convey. I do appreciate attention for theoretical physics but things desire this make the news nothing comes out of it for the next some years no revolution no incredible insight no dress in world view etc and populate will start to wonder ‘what ever happened to’ do these theoretical physicists just make vacuous announcements that never come drink to anything? All the while support dwindles for the less spectacular basics.
Let me give you an example. My preserve is working for a scientific publisher in Germany. They publish a book series that contains literally every stupid fact about material sciences you be and there’s still data that’s added since populate are working in the handle. It’s an extremely boring read it gets sold maybe to some thousand libraries worldwide for an horrendous determine since it takes a lot of time and effort editing. Nevertheless it’s an essential for anybody working in the field. Now it looks desire the publisher will stop the series because it just doesn’t pay off. I’ve suggested they apply for governmental but not sure if they will do (its a rather large publisher having plenty of exceed fields to cerebrate on). What I am trying to say is that not all we do is hip and cool and we’re not all surfer dudes making E8 animations. Events desire this raise in me the concern that support might go increasingly into media-suitable research.
So far it is not clear to me that this theory is even consistent at low energies. I have not spent the any time decoding the notation to see if the above consistency constraints are satisfied. But I shouldn’t have to… these issues are absolutely crucial and should be addressed prominently and explicitly in the paper.
TE:The action is written drink in an efficient expression on page 25. I did use some fancy math tools including Clifford algebra and the Hodge feature instead of using indices. However over the following two pages I expanded the terms of this challenge in dilate including writing out the resulting Dirac action in curved spacetime in indexed components. I did this because I share your wish for a complete and understandable exposition in conventional notation.
You should be able to look at the expanded local coordinate form of these expressions and confirm they match those of the Standard Model with all the correct signs factors of 1/2 no higher derivative couplings and the change by reversal spin statistics. It is true that the original action was chosen by transfer such that this comes out but given the efficient expression used. I consider it non-trivial that this works.
Sabine. I’m sorry that you open that insulting but I was just making a joke and trying to complement you at the same time. The basic point is that if Smolin did want to use someone for PR you would be a good choice. In any case let’s face it this whole media thing with Lisi’s cover is completely unwarranted. There’s really no content there just some big statements and nice pictures. It’s really amazing that this work was funded by the Foundational Questions Institute unless you consider that Smolin is on the scientific advisory panel. Even Smolin I’m sure knows that this work is do by but I believe he has an ulterior motive in supporting it.
Definitely not. I’m a researcher. Eric. The attention my communicate currently gets is about the maximum I am comfortable with. I am not writing it because I want to advertise PI. Lee’s book or my papers but because I like writing it. Since I am currently not teaching I find it a nice way to alter my part to spreading knowledge and to share the fascination my job brings - still and still in new ways.
In any inspect let’s face it this whole media thing with Lisi’s paper is completely unwarranted. There’s really no content there just some big statements and nice pictures.
The cover has circumscribe and I’ve explained in my post in great detail which. What it does not provide in my opinion is a Theory of Everything so I accept that the media hype is unwarranted.
It’s really amazing that this work was funded by the Foundational Questions Institute unless you consider that Smolin is on the scientific advisory panel. Even Smolin I’m sure knows that this bring home the bacon is wrong but I believe he has an ulterior motive in supporting it.
When you see a new theory in formation it’s legit to anticipate that the gaps will be filled new things found to reconcile it with observation and the theory ordain complete itself (if it looks to you like it will) and it’s likewise kosher to anticipate that the gaps and imperfections won’t be worked out and the theory won’t end.
Then if it is completed and firm predictions are derived it’s anybody’s guess whether experiments affirm or refute. Whether its alter or wrong is a later issue. With the E8 theory we are seeing the outlines of something emerge and it seems to have both some problems and some nice features.
What’s not acceptable is to hammer the theory relentlessly as if to punish it for the fact that it attracted command public interest. Whatever the public does or does not do when you crit some new theory development it should be constructive—when you point out problems you should acknowledge how they might be resolved at least in the first weeks and months when the whole thing the only thing that matters is whether or not the theory gets other researchers interested in working on it.
populate in the public don’t have to be protected from believing something might bring home the bacon. Plenty of them are cause to be perceived and skeptical enough to experience that proposed ideas often don’t work and they desire to hear about new ideas anyway. It’s common sense that new ideas can interbreed and morph and help start other ideas—that some ordain cease forever and others you ordain hear about a few years down the road when they re-surface. I think the public knows that or a substantial sector does.
In Garrett’s case what I construe that he said sounded calm and forthright enough. He was constantly pointing to parts of the theory that he was dissatisfied with and looked to improve. And he was repeatedly pointing out that it could turn out wrong—and might not accept with experiment. I heard experience but I did not comprehend hype.
The public reaction I saw was interest but not whole-hog credulity. I don’t think it was contrary to the longterm interests of science. Just normal reaction to some good news. It’s good news that this new idea is out there trying to take cause whether it’s eventually shown alter or wrong. And I really doubt anyone can confidently say at this inform.
Does your theory shed any lighten on why the electro-weak group is U(2) and the electro-strong assort is U(3) and the overall group is S(U(3)xU(2))? I’ve always wondered why the U(3) and U(2) determinants were related in that way i e. epsilon_abc*epsilon_AB is an invariant (lower inspect indices are electrostrong 1-3 indices upper case are electroweak 1-2 indices). This has to do with the global structure of the gauge group of the standard copy. If you assume that the global group is S(U(3)xU(2)) and that anomalies balance in each family then you get a unique solution for the hypercharges in a family (given the SU(3) and SU(2) reps of the quarks and leptons):
are both helpful regarding the properties and interactions of these recurring factions. Popular writers be to have cast Garrett Lisi in the role of a man of the people who is challenging the great and proving again that the people are their equals in every way (including theoretical physics). I evaluate Machiavelli discusses examples in which one of the great suspects that a man of the people is being supported covertly by another of the great. He appears to teach that the antagonism between people and great is reproduced among factions of the great.
In case you end to read the works I named. I’ll just make have in mind that Carnes Lord and Joe Sachs are good translators of Aristotle and that the best available translation of Machiavelli’s
Let’s go away with the classical theory. Garrett has an E8-valued connection on 3+1 dimensions. He has an challenge (his equation 3.7) which explicitly breaks part of the E8 symmetry including the part which notionally mixes fermions and bosons. I say “notionally” because those terms don’t mean anything until we quantize.
Now analyse this situation to the Standard Model coupled to gravity. A classical theory exists here too; then you get to the quantum theory by substituting operators for fields in the usual way.
This seems to be the crux of the debate with Aaron. You don’t need a super-Lie algebra to quantize the Standard Model because the fermions and bosons don’t undergo to mix. Is it the same for Garrett’s theory? If the action didn’t already contain those symmetry-breaking terms wouldn’t Aaron be right? But given that it does does that convey that Garrett’s alter? Section 3.2.3 must be the key here because that’s where the “fermionic” action is extracted.
The hype is dying down. I’ve tried to make it very alter to every reporter I’ve talked with that no be how beautiful and promising a theory looks its validity is determined by predictions and how those fare under experiment. And that with any new theory including this one which is still developing an attitude of healthy skepticism is appropriate.
The thing worrying me is… this E8 Theory was playing out very well in academia before the media hype. I gave four talks on it in quick succession and each one went better than the last with a very good reception from physicists. And the paper generated a great deal of arouse. Then what I thought would be a nice explanation for a lay audience in New Scientist spawned a media frenzy. I just hope the air didn’t obliterate serious consideration of the paper.
Last night I read all the posts on Bee’s blog and I think you handled all the attacks and criticisms that came your way in a manner that showed a great deal of categorise and dignity always answering every challenge or challenge in a good natured way.
In everything I have construe that you have said. I undergo detected no trace of your trying to overhype your work as string theorists have been very guilty of doing with string theory. All I detect is the natural excitement and enthusiasm of a theoretical physicist for his work in trying to understand the laws of nature.
In every instance you are extremely honest and straightforward and always point out that the theory is in its early stages and could prove to be do by and that it will make predictions that ordain be testable. I find this quite refreshing and admirable. My hat is off to you for the way you have conducted yourself.
It might be useful for you to write a more expanded version of your paper that is more in the notation familiar to particle physicists where you carefully and redundantly explain your steps and methods as if you were teaching a week or two long categorise on your theory. A review divide on the key points of Lie algebras and assort theory relevant to your work might also be useful to connect the gap since the theory of exceptional groups may be an impediment to many. It is always good to show simple examples and then talk about the command inspect. I know it is hard to try to do something like that when you are in the lay of doing important work but it could help your create tremendously.
A analyse divide on the key points of Lie algebras and assort theory relevant to your bring home the bacon might also be useful to bridge the gap since the theory of exceptional groups may be an impediment to many
This is not the problem. Everyone knows about E_8. Clifford algebras and BRST symmetries — they’re standard material. What makes the paper difficult to construe (for me at least) is the lack of standard notation (all the tildes underlines and dots for example) and a be of missing steps in various derivations. I would like to see a detailed step-by-step derivation of the standard copy using standard notation. I’d desire to see the exact subgroup of E8 we’re using and the decomposition of the adjoint rep of E8 under that subgroup with each rep labelled with respect to every factor in the subgroup.
The standard model has a well-known set of fields with a well-known set of quantum numbers and interactions. The paper presents a rather piecemeal approach of getting to the standard copy cram and it didn’t make much sense to me. I’d like to see the Lagrangian (3.7) expanded out in its full exuberate so to speak.
Basically right now it feels to me like reading the paper is a chore and I have better things to do. It’s not even clear to me at the moment what the resulting symmetries of the Lagrangian are and the more things I undergo to evaluate out when I construe the cover the less urge I undergo to do so. Sounds selfish I know but such things are adjust about papers in command — you should try to make things as easy as possible for your colleagues.
I think there is a significant difference between the overhyping of Garrett’s work and the overhyping of string theory. One has to do with a very speculative idea that just one person is working on the other a very speculative research program that has dominated particle theory for a couple decades involving thousands of people. I don’t think we’re anywhere near yet the situation where some of the smartest have students in the subject are leaving the field because they conclude that only if they work on Garett’s theory could they find an advisor and go away a career for themselves at the beat graduate programs.
There’s a constant be adrift of overhyped articles in the press about specific speculative ideas in physics being promoted by one person or a small group. New Scientist has such an bind almost every week. Commenting on all such articles would take a lot of time and get them more attention than they deserve so mostly I evaluate it’s best to just do by them
The media Lisi-mania is a much more unusual phenomenon. It has gotten a much wider distribution than usual so it’s a good idea for physicists to put out some more realistic points of view. I think the blogs on the whole have done a good job of this. Anyone who reads the coverage here at Sabine’s blog and at Sean Caroll’s should get a pretty accurate view of what is going on. They could also read Lubos’s blog but he is likely to just convince them that Garrett has definitely accomplished something revolutionary that has driven string theorists insane.
I think we’re comfort quite a ways away from the Pons-Fleischman level of media frenzy. And that was an experimental affirm which led to many groups doing experiments to try and replicate the results (as well as physicists selling platinum short convinced that the way platinum had been bid up because it was the catalyst Pons-Fleischman used would soon collapse as the results weren’t replicated). Claims from serious experimental physicists saying they have an inexhaustible source of free energy are rather more rare than claims from theorists that they have made progress towards a ToE.
The description of what has and hasn’t been done in this paper should be made a lot clearer. E g.. I and quite a few others it seems got the impression that this was supposed to be a unified handle theory with E8 calculate symmetry containing gravity and the SM. The e8 calculate connection and its curvature are discussed at length in a way that gives the impression that they are to be used to create the action for the fields presumably an e8 gauge-invariant one — otherwise why go on about it? If this had really been the inspect then there would be an immediate issue with the Coleman-Mandula theorem. The remark in the paper about C-M not being relevant because the spacetime is deSitter is nonsense since Poincare symmetry can be assumed for all practical purposes when applying the theory to particle scatterings in labs.
The real reason why C-M turns out not to be relevant here (as noted by Aaron B over on Bee’s blog) is that the action proposed for the fields is not e8 calculate invariant: Despite the impression the other parts of the paper furnish the actual construction of the action is not based on the e8 connection and its curvature. Instead it is pulled together from various parts of the e8 curvature in a way that breaks the e8 gauge symmetry; the action is not invariant under transformations that mix the gravitational and internal calculate parts of the e8 connection. This seems really ad hoc to me — there is no governing principle like gauge invariance for determining the challenge it is just cooked up to create the gravity and the SM. (This seems to be Bee’s objection as come up if I understood her comments rightly.) In lighten of this I don’t see any compelling reason for expecting that the new “color scalar fields” that arise have anything to do with nature. So at this point it seems that the paper is just one more not particularly well-motived proposal for what beyond the SM physics might look like. (String phenomenologists already have loads of these apparently.) Well it is not change surface that yet — first one would have to quantized the theory determine the particle content renormalizability etc. But a unified theory it certainly isn’t — where is the unification?
As for the media hype. “surfer dude stuns physics” makes for a cool story but it wouldn’t have happened without the backing of some big-name physicist. Smolin was most obliging in this role but I’m sure it was for the purest of motives (let’s not be getting cynical here ;)). I share very much Bee’s concern about episodes like this leading to an atmosphere where populate conclude pressured to be working on media-appealing hypeable topics rather than solid conservative ones.
One does not undergo to examine the beat E_8 structure to see the“non-unification” unification aspects of the construction. believe his“unification” of the quarks and gluons of QCD using G_2. It is true that the 14-dimensional adjoint rep of G_2 decomposes as the 8 + 3 + \bar 3 of SU(3) under G_2 -> SU(3). And it is true that the gluons are in the 8 and the quarks and anti-quarks in the 3 + \bar 3. So what? What action does Dr. Lisi propose? I am very sure that if you walk through the obscure notation one will discover that either
This posting in no way purports to contain a technical examination of the paper and its problems. I undergo put a “modest be” of effort into understanding what is going on enough to see several problems with what Garrett is trying to do. The sort of general unification/non-unification problem you bring up is specifically addressed in the posting. I don’t think there’s anything at all in what I wrote that hypes the cover quite the contrary. The links I provided to places where it is hyped were given in the context of noting that I don’t think this kind of thing is a good idea at all.
I’ll provide you with another cerebrate to the discussion and my comments at Sabine’s blog about how unprofessional it is to contend populate from behind the cover of anonymity evading any responsibility for one’s actions:
Sorry to walk in late to this go…but as an outsider. I haven’t yet learned to talk shop with the physics media circus at full tilt. You guys should get that thing fixed…
In helping us to understand the motivation for your beliefs can you be at all specific about how you see the origins of E8 as a symmetry group? Is it effectively a black box to you or do you see a preferred set of objects (constructed without benefit of E8) on which E8 acts as natural symmetries? For example do you have any insight into the Freudenthal/Tits magic square construction that is not already present?
As you are likely aware many of us hold the prejudice that if nature uses exceptional algebra as you assert a complete physical theory based on E8 should eventualy illuminate its ‘purpose’ through some kind of principle of emergent exceptional symmetry. As best as I can tell at this re-create your paper treats E8 as an unmotivated combinatorial anomaly from mathematics to be used by physics.
Lastly there is a tremendous ammount of rich folk wisdom held by very respectable mathematicians about E8 most of which is unfortunately unpublished (as it is generally treated as a private hobby). If you would like to talk off line. I could recommend some folks to you who do not seem to be on your acknolwedgement enumerate. This is pretty specialized theory change surface for Lie assort specialists.
I also were quite surprised after understanding that Garrett’s action was not E8 invariant. I evaluate the cover is not so clear about this point. The question is then which kind of unification is this? Of the three unification steps (sight multiplets furnish an invariant challenge and find a breaking mechanism) Garrett only carried out the first one.
Given that the result of this first step is really nice and non trivial since you should acknowledge that some Higgs is contained in the E8 connection as well as _three_ families. This is for the excitement. The rest just calls for much (exciting!) bring home the bacon in the future.
About Coleman-Mandula. I can clarify: the inform is not desitter or noninvariance - because eventually one will look for an invariant theory. The point is that above the unification scale there is probably no metric because the metric itself is inside the e8 connection. If at high energy there is no metric there is no time no standard scatterings and thus no Coleman-Mandula.
But that’s not true change surface if we accept the identifications made in the cover. The three families are not identical — they be in different representations and do not agree with the standard copy.
Thanks for the link. I suggest you read it. I am not anonymous. I undergo a pseudonym. As Bee points out there is a difference. I’ve posted under H-I-G-G-S before and ordain do so again unless you block my comments. My actions have consequences at least in the blogosphere.
Anyway let’s get back to the physics. Garrett agrees that as far as the quarks and gluons are concerned G_2 is totally irrelevant. Since he does the same thing with E8 that is combines all the fields into one connection but then writes drink an challenge piecemeal to agree with the SM. I am tempted to say that the whole E8 is irrelevant. But I think this is not totally fair. After all the SM fields fit into E8 with some dwell left over so the copy “predicts” these extra particles. Of course I could just as easily invent a theory of everything based on a noncompact form of SU(248) or SO(196884) or an infinite be of other groups which would “unify” everything in the same way. And since the challenge is whatever he wants it to be and there is no dynamics to break the E8 symmetry there is no prediction for the masses or couplings of these particles. If they are not found he can just adjust the crowd scale however he wants. I really would have to say that this copy is a prime example of a theory that is “not change surface wrong.” As the old joke goes this paper contains new and correct results but what is change by reversal is not new and what is new is not correct. What move of this do you find interesting and worthy of encouragement?
I suggest you actually read my posting where I explain precisely what I evaluate about what Garrett is trying to do and what parts of it I think are worthy of encouragement. You might also sight that I explictly make the point you’re trying to alter explaining why I’m dubious about this kind of “unification” since it doesn’t understand the problem of how to break the larger symmetry in a way that makes the setup predictive. In principle fitting SM symmetries together into a simple exceptional group like E8 could be constraining enough to be predictive change surface after symmetry breaking but lots of people have tried this kind of thing without success. He seems to be trying something different than a standard GUT set-up one assuming a mixing of space-time and internal symmetries that won’t bring home the bacon in the standard QFT formalism. Maybe he can get something out of this. I certainly encourage him to act trying.
“About Coleman-Mandula. I can clarify: the inform is not desitter or noninvariance - because eventually one will look for an invariant theory. The point is that above the unification measure there is probably no metric because the metric itself is inside the e8 connection. If at high energy there is no metric there is no time no standard scatterings and thus no Coleman-Mandula.”
If at some point in the future someone comes up with an invariant high energy theory of the kind you describe which has Lisi’s model as a low energy effective theory then we can address it. But at the moment there is no proposal for such a theory and no compelling reason for expecting one to exist so talking about it is just idle speculation.
Well we do know triality. The point (I alrady raised in Bee’s communicate) is whether triality is inserted by hand or comes out of the theory itself. For this I think you’ll be a high energy completion… again.
Peter,I happened to re-read your posting and I have a comment that came to me also after reading your book. You wrote that as in GUT programs you move the problem from symmetry to symmetry breaking and for this cerebrate you get no predictions object maybe proton decay in simplest models that we do not observe. I accept but I just want to point out that simplest models are anyway already ruled out by other aspects (by fermion masses notably) so there is no point in ruling them out. Realistic nonminimal models even SU(5) they do _not_ predict a fast proton decay so they are not ruled out.
So the situation is probably even worse than how you put it. No new-physics idea can actually be ruled out they are simply not predictive alone. Not GUT - not certainly strings or extra dimensions - not even SUSY (if we’ll not see it one may comfort raise this and that to alter it invisible). And not even these theories unifying Lorentz and internal symmetries.
Maybe the point is that mathematical ideas geometry unifications etc are just nice frameworks… while one needs a end detailed theory -scales- to make predictions. Btw this is what the standard copy is - a complete theory up to 100GeV :).
It would be funny if Garrett’s theory turned out to be just another limit of string theory - perhaps of some “noncanonical” form of string theory (e g see Lubos’s list under “Strong leadership of supersymmetry”. ). There is actually a heterotic tachyon. Only that’s a compact E8.
So far as I can see the situation with respect to Coleman-Mandula is this. Garrett’s action is consistent with the theorem because the beat E8 symmetry is broken. However the hope or presumption is that the symmetry-breaking terms come from somewhere and that the fundamental theory does undergo full E8 symmetry. At this point the CM problem returns. Fabrizio Nesti in his papers says that CM is evaded because the full symmetry only manifests in a high-temperature topological phase (no metric). If that doesn’t make comprehend we will be left with Aaron’s suggestion to use supersymmetry after all - in which case we’d surely end up with some choose of supergravity and my notion that this is just another superstring limit would look even more plausible.
What I want to understand now is the move about triality and the three generations. There is definitely handwaving on this inform (page 28: “not presently understood well enough to create verbally down”).
I’ll risk really exposing my ignorance and voice one more thought. One of the basic ideas here is that E8 could provide a nonsupersymmetric way to unite fermions and bosons. Meanwhile one corner of superstring theory has an E8xE8 symmetry; and the Monster group shows up in certain compactifications e g a Leech lattice orbifold (I think). Now the care for lattice is rather similar to a copy of three E8 root lattices. So I query if there’s a third E8 lurking in arrange theory that’s responsible for the supersymmetry.
especially considering our previous history in the blogsphere (which includes among other things my successful goading of Jacques Distler into denouncing him…although I got the feeling that Jacques quite enjoyed the opportunity to do that). Perhaps Peter W should be called on to act an exorcism.
At any rate my last two comments above were in say to comments addressed to me by Garrett and Fabrizio so I don’t think they qualify as poking. And my first mention above was just a summary of my opinion on the paper after a bit of reflection and recovery from the mammoth discussion over at Bee’s blog.
Your mention raises an interesting general challenge though: why were those of us who do physics for a job spending measure on reading and discussing this cover? Is it really that interesting compared to all the other physics things we could have been doing? It’s not as if Garrett is the only alternative physicist out there with his own theory. E g. Tony Smith seems just as well qualified academically (he has a Ph. D from Princeton) and for all I experience his theories could be just as deserving (or undeserving) of attention as Garrett’s. (Besides the media air it’s kind of ironic that Garrett is getting blog postings devoted to his theory while Tony gets told to shut up every time he mentions his ones.) My own reasons for spending time on this were: (i) The reported opinions of various prominent physicists; e g. Smolin apparently described it as “fabulous”. (ii) With all the media attention on this. Joe Public wants to know what the consensus opinion of professional physicists is so probably we have some responsibility to assess the paper and alter our opinions known.
But as far as “alternative theories” go there are others that are much more worthy of attention than this one. Just to furnish an example. C. Wetterich has been developing an “alternative” proposal for explaining electroweak symmetry breaking based on chiral coupling of be to massless antisymmetric tensor handle in hep-ph/0607051 arXiv:0709.1102. This looks really interesting and elegant (without having studied it in detail) but seems to undergo been completely ignored so far. (However the compose is no disbelieve less colorful: he’s a beat professor at one of Europe’s illustrious universities — how boring if develop in physics werre to come from someone like that!) I can’t back up getting a feeling that something is fundamentally wrong somewhere when work like this is being ignored while Garrett’s paper is being debated on physics blogs and reported on Fox News. And it is a mind that with this and all the other hype they are subjected to the public will be too jaded to pay attention and care in the future if and when there really is some major gravity/particle theory breakthrough worth telling them about.
One big difference is that Gell-Mann proposed SU(3) as a genuine (unbroken) symmetry of the strong interactions so the properties (quantum numbers etc) of the new particles can be inferred from the fact that they are in the same multiplet as other known ones. There is no such information in Garrett’s model since the symmetry is broken. While we’re on this topic a final poke: It is ridiculous how Garrett has been saying (in statements attributed to him in the press) that the LHC will cause whether his theory is right or not. How does he know whether or not the exotic particles in his theory should show up there? Maybe they should already have shown up in previous experiments in which case their absence disproves the theory. Or maybe they show up at energies much beyond LHC? Does he undergo any idea at all at which energies they should show up?
Yes. Amused,I did’nt reply to you because I agreed with Chris: Garrett does not communicate of the full theory in the symmetric arrange. (And in any inspect he should speak for himself.)
As far as I am concerned in our paper (Graviweak Unification) we _do_ provide both the action in the fully symmetric phase and its breaking: above the breaking scale CM does not apply below it holds of course. This is why I wrote that clarification.
About the ghosts-as-fermions. I have no idea of how this could bring home the bacon and if. Lubos says that this can not be done. It should be easy to work out a simple toy model using BRST. Maybe Peter has thought to it.
I think that blogs (let alone the media) are not the place to demonstrate something right or do by and the conquer of most scientific community is a good write. One should just close the browser for some measure sit drink and try to see if ideas can be made to bring home the bacon. This is what serious physicists will do anyway.
thanks for your long detailed reply indeed i sight it strange too how the attention of the public and of the theoretical physicists is divided between different approaches and how they influence each other i think it just serves to show how much our profession is affected by trends and hot topics too and also how little every one given individual can actually understand of the whole field or how much the judgment is not guided by any higher principle we like to appeal to (desire truth or beauty) but just by trust in our or other peoples opinions.
well one inform i would like to make though is that i evaluate it is not so far out to claim the unobserved particles in the spectrum not to be at too high energies the natural reason i see is just plain simple again: these are particles that should show up in the effective theory at low energy they explicitly populate the spots in the broken lagrangean this is in stark contrast to e g the SU(5) X and Y bosons so while it is still questionable to affirm anything ordain be seen at the LHC it is no more of a misleading statement to me than the TeV measure bulge gravities or anything that tries to bring new
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