An Exceptionally Technical Discussion of AESToE

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  • #51
rntsai said:
(1) e8 has a g2+f4 subalgebra; under this :

e8 = (14,1) + (1,52) + (7,26)

To see this in terms of derivations, take a look at Tits' construction on pg. 49 of Baez's http://xxx.lanl.gov/abs/math/0105155v4". Also, see pg. 41 where another g2 shows up in the f4 decomposition.
 
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  • #52
Mitchell,
It would be straightforward to formulate a similar theory -- including gravity, electroweakish gauge fields, and real fermion fields -- using only F4 instead of E8.

A modified BF formulation of Yang-Mills is equivalent to Yang-Mills, just vary the action with respect to B and plug that expression back in. The advantage of a modified BF formulation is that it naturally gives the Dirac action for fermions, via the pure BF term for that part of the algebra. It should be very interesting to calculate how these parameters run, and how the formulation connects with approaches to quantum gravity.

kneemo,
Thanks for pointing out the reference.
 
  • #53
Garrett, I am kind of curious about how Lee Smolin's new paper differs from your approach. I don't want to drag this thread offtopic so I just want to limit this to two technical questions:

Smolin's paper as I understand it covers two subjects: he discusses a general method for integrating LQG with a gauge group unification theory (such as but not limited to E8), then he proposes a different way of incorporating fermions into an E8 symmetry. Much of the paper is taken up by discussion of proposed actions, although I can't tell if this action discussion is part of the LQG/gauge proposal or the fermion proposal or neither (I think it's only part of the LQG/gauge proposal). My questions are:

1. Does Smolin's proposal concerning linking LQG and E8 necessarily require Smolin's proposal considering fermions in E8 to be adopted? Or are they two separate things? (As far as I can tell the answer is that they are separate, but I am not sure...)

2. Does Smolin's suggested alternate method of incorporating the fermions into E8 require actually changing the group decomposition used in your construction, or does it only modify the action?

Thanks!
 
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  • #54
Hi Coin,
The most interesting thing I see in Lee's paper is how he obtains the action for gravity and gauge fields from an initially E8 invariant action. This addresses a dissatisfaction with the "by hand" symmetry breaking in my paper.
1.They're separate. Having the fermions described by non-local links is an interesting and rather speculative idea.
2.Since the full details of this idea aren't worked out, it's hard to say.
 
  • #55
Garrett, thanks! I may have some more questions later :)

Cold Winter said:
Garrett said:
The tables in my paper just involve the roots for E8 -- it is not necessary to consider representations. (Though considering the representations may be needed for quantization -- which is a somewhat terrifying prospect.) If you do try to reproduce the Atlas calculation, let me know so I can send your computer a sympathy card.
LOL, I have no sympathy for iron. I just pound it hard. While the prospect of running my little monster here for 8 weeks straight doesn't bother me ( I have nice cool place for it here in my home ), I want to build a new little monster. The Atlas redo kinda justifies it... sort of gives me an excuse... sort of... :biggrin:. Problem is this is a wait for prices and technology to converge issue. I'm reasonably certain a 16way AMD64 system will be fairly cheap to build in about 18 months.

Hi Cold Winter, you may want to read the ATLAS group's somewhat tortured narrative of exactly how they went about their calculation. The limiting factor turns out to actually be not CPU power, but RAM. Performing the calculation turns out to involve constructing some tables that grow to hundreds of gigs in size, and they found that they essentially had to store the entire table in RAM, as the calculation requires so many more-or-less-random accesses to this table that access times would have been prohibitive had they allowed swapping to disk. It's an interesting read, anyway.

Incidentally, as regards your comment about doing calculations in C, I think actually this is not so necessary as it at first seems. For heavy computation of the exact kind that dominates the E8 stuff-- working with vectors and matrices and such-- C is I think not actually a very good choice. Many higher-level languages can do vector and matrix operations with a highly optimized backend library, removing many of the advantages C would get in this area from being "closer to the metal". On the other hand with C the "close to the metal" nature can actually be a major drawback, since the degree of power given to the programmer in C takes power away from the compiler, thus preventing many useful compiler optimizations from being possible-- and with this kind of stuff a compiler really is usually much better at optimizing than a human is. I can't speak to the efficiency of Mathematica in specific but it would not surprise me if there are language platforms, for example among some of the functional languages, which resemble Mathematica more than C and yet get better performance than C on E8-related calculations. Of course, these languages bring their own problems! And if you are going to be doing something on the scale of the ATLAS calculation I would tend to suspect you have no choice but to use C. Interestingly ATLAS has a package of downloadable software (although I am not sure whether the E8 map program is included) and it is all written in C++.
 
  • #56
Garrett, hi, that Baez link mentioned earlier is actually a link in your paper (apparently four brilliant minds thinking alike (you, Baez, Tits & kneemo and actually a 5th since I think Baez originally got Tits' idea via Tony Smith). You mentioned your E8 idea in simpler form is kind of an F4 one (with real vectors/spinors), and as you mention in your paper you make complex vectors/spinors via E6 and it seems what you get by going up to E8 is a big Jordan Algebra. That big Jordan algebra along with your MacDowell-Mansouri gravity and your D4xD4 bosons are three really interesting things that justify the hype for me and should hopefully stay no matter what you have to change as far as fermions are concerned. Smolin wrote about a big Jordan Algebra for string theory:

http://xxx.lanl.gov/abs/hep-th/0104050

and I know Tony Smith like it for string theory/spin foam too (and Smolin certainly likes spin foam-type models). Smith and Ark Jadczyk are the two physicists I've read about the most. Ark isn't into Jordan Algebras but he is into Clifford Algebra and Dirac Gammas and Tony I know can talk about an E8 model using Gammas instead of Jordan Algebra so in my mind string theory, spin foams, Jordan Algebra, and Dirac Gammas are all kind of related and found in E8 above E6. You seem to be using Jordan Algebra in a spin foam sense too, is that true?

That D4xD4 for bosons is something I've never seen before. Cause of your use of D4xD4, Tony Smith actually added a way of looking at his model in a D4XD4 way so now I've got not only your model but a new version of Tony's to try and learn the best I can (thanks I think). I think I really like the use of D4xD4 though perhaps not for the reason you use it. It seems like even though you only have a 4-dim spacetime that extra D4 kind of creates an extra 4-dim spacetime. Tony actually has an 8-dim spacetime but I don't fully understand yet his D4xD4 (or yours) as well as I understand Tony's version using only one D4. Anyways thank you very very much for making this kind of stuff more mainstream, mainstream physics no longer seems so depressing to me!
 
  • #57
John,
Yep, many connections...
 
  • #58
garrett said:
It would be straightforward to formulate a similar theory -- including gravity, electroweakish gauge fields, and real fermion fields -- using only F4 instead of E8.

Let's give this a shot then! Just to be clear, my objective is to work this through until I can see to my own satisfaction that it is a well-defined quantum theory. So let me sketch in advance how it looks like things are supposed to go. Your equations 3.7 and 3.8 will still hold, except that things are now f4-valued. Gravitational so(3,1) will drop out, and there will be fermions and gauge bosons left over.

First question: which parts of f4 will play the role of \underset{.}{\Psi}? It looks like I can break it down as f4 = so(8)+(8+8+8) or as f4 = so(9)+16 - would these lead to distinct "modified BF F4" theories?
 
  • #59
mitchell,
Things aren't going to be much easier with F4. One 8 will be the first generation of leptons, but... Majorana I think. And the other two 8's will be related by triality, but that leaves the same generation issue as with E8.
 
  • #60
Tony Smith used to hang here. He is brilliant, and unorthodox. I'm a big fan [despite getting booted from 'Arxiv' for no reason]. I think garrett is on the same track with his approach. The E8 concept looks bullet proof to this point.
 
  • #61
How about SO(9)\oplusSpin(9)? Again, this is just for didactic purposes - for someone who wants to be shown how they can get, say, Feynman rules for a theory like this. So far as I can see, there should be a modified BF F4 theory with SO(9) bosons and Spin(9) fermions in which several of your constructions can be carried out.

One thing that had been troubling me was where the uniqueness (no free parameters) comes from. I couldn't follow it down to the phenomenological level. But I guess it's just that the field couplings are determined by the structure constants, and then the masses are determined by the couplings and the Higgs VEVs.
 
  • #62
f4 and e8

Mitchell Porter asks about f4 = so(8)+(8+8+8)

Here is how I see that:

f4
=
so(8) 28 gauge bosons of adjoint of so(8)
+
8 vectors of vector of so(8)
+
8 +half-spinors of so(8)
+
8 -half-spinors of so(8) (mirror image of +half-spinors)


Therefore, you can build a natural Lagrangian from f4 as

8 vector = base manifold = 8-dim Kaluza-Klien 4+4 dim spacetime

fermion term using 8 +half-spinors as left-handed first-generation particles
and the 8 -half-spinors as right-handed first-generation antiparticles.

a normal (for 8-dim spacetime) bivector gauge boson curvature term using
the 28 gauge bosons of so(8).

If you let the second and third fermion generations be composites of the first,
i.e., if the 8 first-gen particles/antiparticles are identified with octonion
basis elements denoted by O,
and
you let the second generation be pairs OxO
and the third generation be triples OxOxO
and
if you let the opposite-handed states of fermions not be fundamental,
but come in dynamically when they get mass,
then
f4 looks pretty good IF you can get gravity and the standard model
from the 28 so(8) gauge bosons.

Recall that n=8 supergravity etc had problems because
the 12-dim Standard Model SU(3)xSU(2)xU(1)
does NOT fit inside 28-dim Spin(8) in a nice subgroup way.

If you want to make gravity from 15-dim Conformal group so(2,4) by McD-M
then
you have 28-15 = 13 so(8) generators left over,
which are enough to make the 12-dim SM,
BUT
the 15-dim CG and 12-dim SM are not both-at-the-same-time
either Group-type subroups of Spin(8)
or Algebra-type Lie algebra subalgebras of so(8).

If you try to get both the 15 CG and 12 SM to fit inside the 28 so(8),
you see that they do not fit as Lie Group subgroups
and
you see that they do not fit as Lie algebra subalgebras
so
what I have done is to look at them as root vectors,
where the so(8) root vector polytope has 24 vertices of a 24-cell
and
the CG root vector polytope has 12 vertices of a cuboctahedron
and
the remaining 24-12 = 12 vertices can be projected in a way that
gives the 12-dim SM.

My root vector decomposition (using only one so(8) or D4) is one of
the things that causes Garrett to say that I [Tony]
have "... a lot of really weird ideas which I[Garrett] can't endorse ...".

So,
from a conservative point of view, that you must use group or Lie algebra
decompositions,
f4 will not work because one copy of D4 so(8) is not big enough for
gravity and the SM.

Also,
f4 has another problem for my approach:
f4 has basically real structures,
while
I use complex-bounded-domain geometry ideas of Armand Wyler to calculate
force strengths and particle masses.

So,
although f4 gives you a nice natural idea of how to build a Lagrangian
as integral over vector base manifold
of
curvature gauge boson term from adjoint so(8)
and
spinor fermion terms from half-spinors of so(8)

f4 has two problems:
1 - no complex bounded domain structure for Wyler stuff (a problem for me)
2 - only one D4 (no problem for me, but a problem for more conventional folks).

So,
look at bigger groups:

e6 is nice, and has complex structure for me,
so I can and have constructed an e6 model,
but
it still has only one D4 (which is still a problem from the conventional view),

so

do what Garrett did, and go to e8
and notice that
if you look at EVIII = Spin(16) + half-spinor of Spin(16)
you see two copies of D4 inside the Spin(16)
(Jacques Distler mentioned that)
which are enough to describe gravity and the SM.

I think that Garrett's use of e8 is brilliant,
and have written up a paper about e8 (and a lot of other stuff) at

http://www.valdostamuseum.org/hamsmith/E8GLTSCl8xtnd.html

which has a link to a pdf version
(there is a misprint on page 2 where I said EVII instead of EVIII,
and probably more misprints, but as I said in the paper
"... Any errors in this paper are not Garrett Lisi's fault. ...".

I use a different assignment of root vectors to particles etc
I don't use triality for fermion generations,
since my second and third generations are composites of the first,
as described above in talking about f4.

For an animated rotation using Carl Brannen's root vector java applet from

http://www.measurementalgebra.com/E8.html

see my .mov file at dotMac at

http://web.mac.com/t0ny5m17h/Site/CB4E8snp.mov

In it:

24 yellow points are one D4
24 purple points are the other D4

64 blue points are the 8 vectors times 8 Dirac gammas (of 8-dim spacetime)

They are the 24+24+64 = 112 root vectors of Spin(16)

64 red points are the 8 fermion particles times 8 Dirac gammas

64 green points are the 8 fermion antiparticles time 8 Dirac gammas.

They are the 64+64 = 128 root vectors of a half-spinor of Spin(16).

If you watch them rotate,
you can see how they are related in interesting ways.


Tony Smith
 
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  • #63
Coin said:
Hi Cold Winter, you may want to read the ATLAS group's somewhat tortured narrative of exactly how they went about their calculation. The limiting factor turns out to actually be not CPU power, but RAM. Performing the calculation turns out to involve constructing some tables that grow to hundreds of gigs in size, and they found that they essentially had to store the entire table in RAM, as the calculation requires so many more-or-less-random accesses to this table that access times would have been prohibitive had they allowed swapping to disk.

I've looked at the Atlas code. Yes it seems to be all "C", but with a few modules that seem more GUI related. I am perhaps a bit more jaded when it comes to iron than others. For e.g. I have a supplier pawning DDR2 ram for $9.99/GB... that puts 128GB in the $1278 range. Same source has a 16 way SATA2 controller at around $600 and of course, 250GB SATA2 drives are now in the $120 range ( 16X means $1920 ) Motherboards are now in the $1500 range for 4 socket Opterons... that leaves 4 cpus ( AMD has announced 4 core units for 2009 ? ) typically in the $1200/piece range. I figure I can build one H...! of a monster for around $10,698 in todays terms.

In 18 months that could be under $4000... which I think I can swing at that time.

BTW, that's 2Terabytes of disk mirrored and striped, so getting around the other difficulties ( capacity and I/O speed ) noted in that article isn't a biggy. That SATA2 controller at 300MB/sec will be hitting all disks at about 192Mb/sec... which should translate into a run time guesstimate of 11,000 seconds ( <200 minutes? ).

I'm inclined to go with FP math on this so that conversion will double the bandwidth requirement at a bit higher speed. Although I have to check the SSE capability with the 32 bit integers that the Atlas programmers originally used. That could certainly impact the run times in both directions.

In effect, given some time ( and a budget to fit my limited means ) I should be able to hammer E8 quite nicely. Certainly for much less than what the LieGroup are talking about.
 
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  • #64
mitchell,
I don't want to go too far with tangents like so(9)+9 because the thread will get confusing. But the modified BF setup in the paper is a very adaptable way to take algebras like this and get models with bosons and fermions. What you said about the couplings (from the structure constants) and the masses (from the Higgs VEVs) is correct.

Hi Tony,
Welcome back to PF. I think it's great that you and several other people have taken this E8 idea and run with it. It's good to have people searching in all different directions. In the paper, I tried to use a bare minimum of mathematical structure, but it's possible a little more will be needed in order to solve the generation question. Even if I can't solve it minimally, it will be satisfying to me if others take the mathematical ideas and tools in the paper and use them in their own models.
 
  • #65
kneemo said:
To see this in terms of derivations, take a look at Tits' construction on pg. 49 of Baez's http://xxx.lanl.gov/abs/math/0105155v4". Also, see pg. 41 where another g2 shows up in the f4 decomposition.

Thanks kneemo for the reference. I didn't realize it before but there's
quite a bit on the algebra decompositions in Baez' paper; he just put
towards the end of the paper...long after the octanion setting has worn
me out. The use of quaternions (and octanions, clifford algebras,...)
is probably intersting in its own right and I think it helps if you
have a deep pool of understanding of such things that you can draw
on to clarify things. Unfortunately I don't, so they end up obscurring
rather than clarifying things for me. For the sake of what's in Garrett's
paper, Lie algebras over the complexes (or reals) is enough.

What I was (and am still) looking for is an explicit description of these
decomposition...something I can run explicit calculations with. I have such
a thing for the f4/d4 : f4=28+8+8+8 case (see an earlier post in this thread);
I'm looking for the e8/(d4+d4) and e8/(g2+f4) equivalent. Something like :

(1)a basis for e8; Cartan basis is good, Chevalley even better since that's
what I have already. The structure constants of e8 in either of these
basis are well known and are accessible for my calculations.

(2)another basis of e8 in terms of (1) that exhibits the decomposition.
This could be just a 248x248 matrix where so for example rows 1 to 52
span f4,...

Table 9 in Lisi's paper in principle has the same information for e8/(d4+d4)
so it should be usable if I can work out the mapping between the 8 columns
(1/(2i))w_T^3,(1/2)w_S^3),U^3,V^3,w,x,y,z and an accessible basis of e8.
Altrenatively I can start with the Chevalley basis that I have and mimic
the rotation/projections Gerrett Lisi describes; but each step is susceptible
to misinterpretting conventions (right vs left matrix action for example), typos,...
 
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  • #66
combining quarks

Garrett,

Is it possible to assign the real physical u-quark particle to a combination of the u-L and C-L roots of your table 9 such that its a vector with w-quantum number of zero, just like the t, b quarks? (and the same w=0 for all leptons and quarks). Would this lift the degeneracy of the quark masses due to the higgs fields? Could the neutrino's get their mass from the new x-i.phi fields rotating them to a (+/- one) w quantum number?

berlin
 
  • #67
rntsai,
I think the basis for the roots in Tables 8 and 9 are pretty standard. You may be able to construct or match up a basis of e8 generators from John Baez's paper, but I haven't worked this out explicitly yet.

Hello Berlin,
Yes, these are all ideas worth playing with. There are many ways to take the framework in this paper and develop it in various directions to try and resolve the remaining mysteries.
 
  • #68
rntsai said:
Unfortunately I don't, so they end up obscurring
rather than clarifying things for me. For the sake of what's in Garrett's
paper, Lie algebras over the complexes (or reals) is enough.

What I was (and am still) looking for is an explicit description of these
decomposition...something I can run explicit calculations with. I have such
a thing for the f4/d4 : f4=28+8+8+8 case (see an earlier post in this thread);
I'm looking for the e8/(d4+d4) and e8/(g2+f4) equivalent.

For explicit calculations, Baez's paper isn't the best reference. If you want to see how the F4 and E6 derivations are constructed see pgs. 29-33 of http://arxiv.org/abs/hep-th/0302079" . The E7 and E8 infinitesimal transformations are merely extensions of these.
 
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  • #69
kneemo said:
For explicit calculations, Baez's paper isn't the best reference. If you want to see how the F4 and E6 derivations are constructed see pgs. 29-33 of http://arxiv.org/abs/hep-th/0302079" . The E7 and E8 infinitesimal transformations are merely extensions of these.

I posted a question about this in the GAP forum and a Scott Murray
was kind enough to send me explicit basis for both d4+d4 and g2+f4.

Looking at the last three columns of Table 9, it seems there's a
relationship between the two decompositions. What's the nature
of this relationship?

We have under d4+d4 : e8=(28,1)+(1,28)+(8,8)+(8',8')+(8'',8'');

The table implies for example that 64 dimensional (8',8') breaks up
as 8(l)+8(l')+24(qI)+24(qI') (under g2? or f4?).
 
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  • #70
rntsai said:
I posted a question about this in the GAP forum and a Scott Murray
was kind enough to send me explicit basis for both d4+d4 and g2+f4.

Looking at the last three columns of Table 9, it seems there's a
relationship between the two decompositions. What's the nature
of this relationship?

The first d4 is a subalgebra of f4, and g2 is a subalgebra of the second d4.

We have under d4+d4 : e8=(28,1)+(1,28)+(8,8)+(8',8')+(8'',8'');

The table implies for example that 64 dimensional (8',8') breaks up
as 8(l)+8(l')+24(qI)+24(qI') (under g2? or f4?).

The 8's are acted on by d4 in f4, and the 1's and 3's for l's and q's are acted on by a2 in g2.
 
  • #71
Hello Mr. Garrett!,

I would like you to comment on this. The guy who pointed you some mistakes (Jacques Distler), made several more remarks about your theory, specially after DEC 9TH. He seems to be changing his mind every day, maybe he is confused.

He is still seems to be very hostile to your theory. But if you discuss with him, it would be profitable, as his got some new maths. He is saying you are not even getting the 1st generation right

http://golem.ph.utexas.edu/~distler/blog/archives/001505.html#AlittleU4
***************

Update (11/29/2007):
David Vogan, from MIT, wrote me to point out that I was too fast in saying that G does not embed in F 4×G 2. It is possible to find such an embedding, but it necessarily leads to a completely nonchiral “fermion” representation (and hence contains no copies of R). I simply didn’t bother considering such embeddings, when I was preparing this post. For the record, though
F 4(−20)⊃Spin(8,1)⊃Spin(3,1)×Spin(5)⊃SL(2,ℂ)×SU(2)×U(1)
and
F 4(4)⊃Spin(5,4)⊃Spin(3,1)×Spin(2,3)⊃SL(2,ℂ)×SU(2)×U(1)
In the latter case, one obtains
26=1+9+16 =(1,1) 0+(4,1) 0+(1,3) 0+(1,1) 2+(1,1) −2 +(2,2) 1+(2,2) −1+(2¯,2) 1+(2¯,2) −1 52=36+16 =(Adj,1) 0+(1,3) 0+(1,1) 0+(1,3) 2+(1,3) −2+(4,3) 0+(4,1) 2+(4,1) −2 +(2,2) 1+(2,2) −1+(2¯,2) 1+(2¯,2) −1
In the former case, there are two distinct embeddings of SU(2)×U(1)⊂Spin(5). For the one under which 4=2 1+2 −1, one obtains the same result as above. For the one under which 4=2 0+1 1+1 −1, one obtains
26 =2(1,1) 0+(4,1) 0+(1,2) 1+(1,2) −1 +(2,2) 0+(2,1) 1+(2,1) −1+(2¯,2) 0+(2¯,1) 1+(2¯,1) −1 52 =(Adj,1) 0+(1,3) 0+(1,1) 0+(4,1) 0+(1,1) 2+(1,1) −2+(1,2) 1+(1,2) −1+(4,2) 1+(4,2) −1 +(2,2) 0+(2,1) 1+(2,1) −1+(2¯,2) 0+(2¯,1) 1+(2¯,1) −1
Putting these, together with the embedding of SU(3)⊂G 2,
7 =1+3+3¯ 14 =8+3+3¯
into (3), one obtains a completely nonchiral representation of G.

Update (12/10/2007):
For more, along these lines, see here http://golem.ph.utexas.edu/~distler/blog/archives/001532.html

Correction (12/11/2007):
Above, I asserted that I had found an embedding of G with two generations. To do that, I had optimistically assumed that there is an embedding of SL(2,ℂ) in a suitable noncompact real form of A 4, such that the 5 decomposes as 5=1+2+2. This is incorrect. It is easy to show that only 5=1+2+2¯ arises. Thus, instead of two generations, one obtains a generation and an anti-generation. That is, the spectrum of “fermions” is, again, completely non-chiral. I believe (but haven’t proven) that this is a completely general result: for any embedding of G in either noncompact real form of E 8, the spectrum of “fermions” is always nonchiral. Let’s have a contest, among you, dear readers, to see who can come up with a proof of this statement.I apologize if I’d gotten anyone’s hopes up, with the above example. Not only can one never hope to get 3 generations out of this “Theory of Everything”; it appears that one can’t even get one generation.

*****************

And here is a post apparently claiming a final blow (not his words, but my emotional interpretation). A certain mark refers to Smolin and you almost as crackpots (again, not his words, but my emotional interpretation)

http://golem.ph.utexas.edu/~distler/blog/archives/001532.html#more

******************

There it is Garrett. Would you have some comments about that?
 
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  • #72
Hello MTd2,
This issue of non-compact subalgebras of non-compact real E8 is pretty tricky. Jacques is trying to pass this stuff off as obvious, but having a hard time doing that since he's been making mistakes. I did the calculations using compact real E8, and figured I could change the signature of part of the Killing form to get a non-compact version, by inserting an i in the roots -- but this was probably naive on my part. In the paper, I do use so(7,1)+so(8), and I though this was in E IX, but it isn't. Jacques asserted in a comment to his first post that so(7,1)+so(8) is in split real E8. This was news to me. Then, in his second post, he said so(7,1)+so(8) isn't in split real E8, as if I were the one who initially said it was. Also, in his second post, Jacques asserted that spin(12,4) was in split real E8 -- another mistake -- then he went back this morning and edited that out of the post, without noting his error.

This behavior makes me pretty wary. Despite his hostility and mistakes, I've learned a bit of useful math from the discussion with Jacques, and will see what I can do with it. I may be able to get things to work with so(7,1)+so(1,7), or with so(12,4), or I might have to try something more drastic. I already knew I was going to have to do something significantly different to get the second and third generations to work in this theory, so, really, not much has changed -- there are now just more clues.
 
  • #73
garrett, a question wrt Distler's comments:

My understanding of lie groups is very limited and Distler's blog is very ranty so I've had a great deal of trouble picking out what exactly Distler is trying to say in his posts. However it does seem there is one specific important criticism he has made which I haven't seen addressed yet, which is his claim in his second post (which MTd2 quotes from above) where Distler claims that, even if you only attempt a single-generation embedding, the fermions one gets out of the E8 connection are nonchiral.

Has Distler found an actual problem with the E8 connection idea here? Or is this a problem which is real but which you had already forseen somewhere? Or would you say there is some reason that Distler's claim about E8 producing nonchiral fermions is either incorrect or misapplied?
 
  • #74
Coin,
The Pati-Salam GUT I'm embedding in E8 is a http://en.wikipedia.org/wiki/Left-right_model" standard model -- but ways to do this are well established.
 
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  • #75
OK, thanks for the clarification.
 
  • #76
I want to highlight the effort of embending a link in the words that Garrett used ... ie. chiral ... this is not an exercise needed for the "math kids".
Thanks
 
  • #77
Nice, so your E(8) naturaly has massive and oscilating neutrinos. Maybe it can shed light on the doubts sorrounding the data from LSND and MiniBooNE experiments, that shows the possibility of sterile neutrinos.

http://en.wikipedia.org/wiki/LSND

http://en.wikipedia.org/wiki/MiniBooNE

Notice that are some anomalies detected in the low energy region of neutrinos, showing a high incidence of eneutrinos. That would be a "confirmation" of brane physics, that is, neutrinos "arriving" from other dimensions, the "bulk of the brane", and intersecting our "brane surface". Some string theorists are excited for that ("Bill Louis, of the MiniBooNE project, has emailed the brane theorists saying: "It is indeed startling to see how well your model appears to fit our excess of low energy events!" There remains the possibly that the effect is a spurious statistical or background anomaly and further analysis is underway."). But, maybe your theory can explain that anomaly without appealing to other dimensions.
 
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  • #78
MTd2,
Neutrino oscillation is going to be a large clue for further development of the theory, but right now the second and third generations aren't described well enough in the theory to make any predictions. Also, this is heading into physical speculation, and I'd like to keep this a technical discussion.
 
  • #79
In keeping with this being "a technical discussion",
here is something that I asked in response to a comment by Thomas Larsson over on Cosmic Variance in Sean's post "Garrett Lisi’s Theory of Everything!":

Could Garrett Lisi’s model be understood in terms of a 7-grading of e8 that was described in a sci physics research thread Re: Structures preserved by e8, in which Thomas Larsson said:

“… … e_8 also seems to admit a 7-grading,
g = g_-3 + g_-2 + g_-1 + g_0 + g_1 + g_2 + g_3,
of the form

e_8 = 8 + 28* + 56 + (sl(8) + 1) + 56* + 28 + 8* .

…[in]… the above god-given 7-grading of e_8 … g_-3 is identified with spacetime translations and one would therefore get that spacetime has 8 dimensions rather than 11. …”.

So, if you used g-3 for an 8-dim Kaluza-Klein spacetime,
could you see the 28* and 28 as the two copies of D4 used by Garrett Lisi to get MacDowell-Mansouri gravity from one and the Standard Model gauge bosons from the other
and
see the central sl(8)+1 being related to transformations of the 8-dim spacetime
(actually being a 64-dim thing that is substantially 8×8* ).

The even part of the grading would then be the 112 elements
28* + 8×8* + 28
and
the odd part of the grading would then be the 128 elements
8 + 56 + 56* + 8*
If the 8 and 8* are used for 8-dim Kaluza-Klein spacetime
so
could the 56 + 56* be used for fermion particles and antiparticles ?

Even if the above assignment needs improvement,
my basic question is

could Thomas Larsson’s 7-grading of e8 be useful in making Garrett Lisi’s model a realistic description of physics ?

Tony Smith

PS - My personal favorite interpretation of the e8 7-grading is a bit different from what I described above, but I altered it to fit Thomas Larsson's explicit idea that the 8 should correspond to a spacetime.
 
  • #80
where's the Z?

Some random questions on exchange particles that I hope are not too basic :

- What happens to the Z boson in your (and Pati-Salam) model;
It looks like the W^+ and W^- bosons show up as is, but
the Z is "replaced" by two new bosons : B_1^+,B_1^-;
The photon is burried somehere inside D2_{ew}; is it
W^3 + B_1^3 -sqrt(2/3)B_2 (page 11)

- I think you use circles as a suggestive notation for
"exchange particles". I can identify the purple and yellow
circles (proudly since age 5). I have trouble with the
green ones, do they correspond to anything that might be
more recongnizable?
 
  • #81
Garrett,

it seem Lee Smolin admited he is wrong, and admited that your theory do not include Pati -Salam model:

# Lee Smolin on Dec 15th, 2007 at 8:36 pm

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
# H-I-G-G-S on Dec 15th, 2007 at 10:15 pm

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 acknowledgment. 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
http://cosmicvariance.com/2007/11/16/garrett-lisis-theory-of-everything/
 
  • #82
garrett said:
Quote:
Now it seems clear that the Coleman-Mandula question pertains only to the unbroken theory, or to put it another way, that in the broken theory, although the connection is still E8-valued, the action is no longer E8-symmetric.
That's right.

If your connection would be valued in the algebra, its would be expandable in the generators of E8. But some components of your connection are fermionic and thus anticommute, or? How can these possibly satisfy any E8 commutation relations? And if not, what on Earth has your construction then to do with E8?

As I was writing over at CV, this is completely different to symmetry breaking (where the proper commutation relations are still satisfied, though non-linearly realized).
 
  • #83
Tony,
There are many gradings of E8, most of them interesting. I haven't thought about 7-gradings much. My favorite grading of E8 is a 13 grading corresponding to weak hypercharge -- which currently only works correctly for the first generation.

rntsai,
The Z and the photon fields are (rotated) combinations of W, B_1, and B_2. Specifically, as 1-form coefficients,
\underline{Z} = \sqrt{\frac{5}{8}}\underline{W}^3 - \sqrt{\frac{3}{8}} (\sqrt{\frac{3}{5}} \underline{B}_1^3 + \sqrt{\frac{2}{5}} \underline{B}_2)
and
\underline{\gamma} = \sqrt{\frac{3}{8}}\underline{W}^3 + \sqrt{\frac{3}{8}}\underline{B}_1^3 + \sqrt{\frac{2}{8}}\underline{B}_2
The B_1^\pm, and a leftover
\underline{X} = \sqrt{\frac{2}{5}} \underline{B}_1^3 - \sqrt{\frac{3}{5}} \underline{B}_2
are "new" gauge fields, as in Pati-Salam. (I'm pretty sure I have those right, but I haven't confirmed them.)

The circles are all gauge fields: green for gravitational \omega_{L/R}^{\wedge/\vee}, yellow for weak W^{\pm}, blue for gluons, and white for B_1^\pm. The Z, photon, and X are in the Cartan subalgebra at the origin, and are conventionally not plotted.

MTd2,
H-I-G-G-S was twisting Lee's words, as is clear from his reply (which was visible when you posted).

moveon,
The connection starts out as an E8 valued 1-form. The action (with E8 symmetry broken by hand in my paper, but not in Lee's) introduces dynamical terms for the D4+D4 part of E8, but leaves only the BF term for the rest of E8. These pure gauge degrees of freedom may be replaced by Grassmann fields valued in the non D4+D4 part of E8 -- these are fermions. The resulting generalized connection consists of Lie(E8) valued 1-forms and Grassmann numbers, with the same E8 brackets between Lie algebra elements. This is a fairly standard mathematical construction, used in an unusual way. I'd be happy to expand on it for you or provide references.
 
  • #84
Garrett, exactly what is the 13-grading of e8 that you like to use?

Tony Smith
 
  • #85
Let me make a guess for garrett. The 13 is a weak grading, so it's going to correspond to the weak hypercharge quantum numbers of the standard model, that is, it will use the 13 values: (-1, -5/6, -2/3, -1/2, -1/3, -1/6, 0, +1/6, +1/3, +1/2, +2/3, +5/6, +1). To see the assignment, I would start by looking for the weak hypercharge quantum numbers assignment in his paper. Then you assign a particular root to a blade according to its weak hypercharge quantum number.

My recollection of the standard model is that the +- 5/6 quantum numbers are missing. These blades would be particles that don't appear in the standard model. But my concentration has always been on the fermions -- are there some bosons with weak hypercharge +- 5/6?

The peculiar pattern of the weak hypercharge quantum numbers that are actually used in the standard model, that is, leaving off the +- 5/6, has 11 values. Since I'm a density matrix proponent, (which are bilinear rather than the usual state vector formalism which is linear) I'm going to link in a paper which gives those 11 values, rather than all 13, as a solution to a bilinear equation. See chapter 5: http://www.brannenworks.com/dmfound.pdf
 
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  • #86
Tony,
If we rotate the E8 root system until the vertical axis is weak hypercharge, and rotate out the other axes horizontally to separate the roots a bit, it looks like this:
http://deferentialgeometry.org/blog/hyper.jpg
This makes it visible exactly what is meant by "the charge assignments only work correctly for the first generation," with the other two (smaller triangles) related by triality.
 
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  • #87
When I count the 13-grading from that image I get:

5 + 6 + 15 + 20 + 30 + 30 + 26 + 30 + 30 + 20 + 15 + 6 + 5

which only add to 238, so I must be miscounting two of them somewhere ?

Anyhow, modulo my error of two, the even graded structure would be

5 + 15 + 30 + 26 + 30 + 15 + 5 = 126-dimensional
(if the missing 2 are even, then 128-dimensional)

and the odd graded structure would be

6 + 20 + 30 + 30 + 20 + 6 = 112-dimensional

so

it seems to me that the odd gradings correspond to the 112 root vectors of the adjoint Spin(16) (120 generators - 8 Cartan subalgebra generators = 112)

and

that the even grading probably have the two I miscounted and are the 128 root vectors corresponding to the half-Spinor of Spin(16).

What bothers me about that is that the fermionic spinor-type things are in the even grading and the bosonic vector/bivector adjoint-type things are in the odd grading,

whereas in Thomas Larsson's 7-grading

8 + 28* + 56 + (sl(8) + 1) + 56* + 28 + 8* = 8 + 28 + 56 + 64 + 56 + 28 + 8

the even grade part is
28 + 64 + 28 = 112 dimensional corresponding to the root vectors of adjoint Spin(16) which seems to represent bosonic vector/bivector stuff
while
the odd grade part is
8 + 56 + 56 + 8 = 128-dimensional corresponding to half-spinor of Spin(16) which seems to represent fermionic spinor-type stuff.

Do you have any thoughts about that ?

Tony Smith
 
  • #88
Tony,
Two gluons overlap. There are many such gradings of E8 -- there may be the same kind of 13 grading along a different direction that gives the even/odd 120/128 split you're after.
 
  • #89
no chiral embedding

Hi Garrett,

I would like to have your comments on http://golem.ph.utexas.edu/~distler/blog/archives/001532.html" ).

I personally feel Distler's argument is fundamental, relatively easy to follow, and seems to be correct, at least up to the level of my knowledge (perhaps I'm making a mistake). Lee has been trying to address it on Cosmic Variance, but hasn't succeeded in finding a mistake or a loophole in it yet. Do you have anything to say about it?

Thanks a lot! :-)
 
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  • #90
garrett said:
The resulting generalized connection consists of Lie(E8) valued 1-forms and Grassmann numbers, with the same E8 brackets between Lie algebra elements. This is a fairly standard mathematical construction, used in an unusual way. I'd be happy to expand on it for you or provide references.

Please! To my knowledge the only algebras that contain both bosonic and fermionic generators are superalgebras, and E8 is not one of them. How can the commutation relations close into E8?
 
  • #91
moveon said "... the only algebras that contain both bosonic and fermionic generators are superalgebras ...".

No, that is not true.
As Pierre Ramond in hep-th/0112261 said "... exceptional algebras relate tensor and spinor representations of their orthogonal subgroups ...",
and
the exceptional algebra 248-dim E8 contains
120 generators corresponding to the tensor/bosonic part 120-dim adjoint Spin(16)
and
128 generators corresponding to the spinor/fermionic part 128-dim half-spinor Spin(16)
and
their commutation relations do close into E8.

However, Pierre Ramond went on to say in that paper:
"... Spin_Statistics requires them [ the adjoint/bosonic and half-spinor/fermionic ] to be treated differently ...",
so
any model you build with E8 must somehow treat them differently.

For example, you might just construct a Lagrangian into which you put
the 128 half-spinor fermionic generators into a fermion term
and
8 of the 120 bosonic generators into a spacetime base manifold term
and
120-8 = 112 of the 120 bosonic generators into a gauge boson curvature term.

Then you might have disagreement as to how natural (or ad hoc) is such an assignment of parts of E8 to terms in a Lagrangian,
but all should agree that you have "treat[ed] them differently" as required by Spin-Statistics.

However, in Garrett's 13-grading decomposition of the 240 root vectors of E8

5 + 6 + 15 + 20 + 30 + 30 + 28 + 30 + 30 + 20 + 15 + 6 + 5

some of the graded parts contain both bosonic terms and fermionic terms,
for example the central 28 has both circles (bosons) and triangles (leptons and quarks),
which has led Thomas Larsson to complain (on Cosmic Variance):
"... both fermions and bosons belong to the same E8 multiplet. This is surely plain wrong. ...".

I think that the point of Thomas Larsson is that
the model must treat the fermions and bosons differently to satisfy Spin-Statistics
so
the fermionic generators must be put into some part of the model where the bosonic generators are not put
so
if you decompose the generators into multiplets some of which contain both fermionic and bosonic generators (as in Garrett's 13-grading decomposition) then you are not respecting your multiplets when you, from a given multiplet, put some of them into a fermionic part of the model and some of them into a bosonic part of the model.

This is not merely an objection of ad hoc assignments of generators to parts of the model,
it is an objection that the assignments do not respect the chosen decomposition into multiplets.

Tony Smith

PS - It is possible to choose a decomposition that does keep the bosonic and fermionic generators separate, the simplest being 64 + 120 + 64
where the 120 is bosonic and the 64+64 = 128 is fermionic.
 
  • #92
Tony Smith said:
moveon said "... the only algebras that contain both bosonic and fermionic generators are superalgebras ...".

No, that is not true.
As Pierre Ramond in hep-th/0112261 said "... exceptional algebras relate tensor and spinor representations of their orthogonal subgroups ...",
and
the exceptional algebra 248-dim E8 contains
120 generators corresponding to the tensor/bosonic part 120-dim adjoint Spin(16)
and
128 generators corresponding to the spinor/fermionic part 128-dim half-spinor Spin(16)
and
their commutation relations do close into E8.


Oh yes, this is of course very well known since ages. But those tensor and spinor rep generators are all bosonic, and close into the usual E8 commutator relations. My point is, apparently still not appreciated, that if some of the generators are made fermionic (as it happens for superalgebras), then they cannot produce the E8 commutation relations (and jacobi identities etc) any more. The opposite seems to be claimed here all over, so I'd like to see, how. Please prove this by writing them down!

And if the E8 commutation relations are not there, there is no E8 to talk about. There is "somewhat" more to E8 than a drawing of the projection of its polytope...
 
  • #93
This from Tony's website might be good to look at (I'm sure Tony can say more if needed):

http://www.valdostamuseum.org/hamsmith/stringbraneStdModel.html
 
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  • #94
One needs to distinguish between spin and statistics.

There are two types of statistics: fermions, which anticommute and obey Pauli's exclusion principle, and bosons, which commute.

There are also two types of spin: spinors, which have half-integer spin, and tensors and vectors, which have integer spin.

The spin-statistics theorem asserts that physical fermions always have half-integer spin and physical bosons have integer spin. But this is non-trivial and surprisingly difficult to prove. In contrast, BRST ghosts are fermions with integer spin, and therefore unphysical. Physical and unphysical fermions are not the same.

What is quite easy to prove is that statistics is conserved, i.e.

[boson, boson] = boson
[boson, fermion] = fermion
{fermion, fermion} = boson.

People like Lee, Peter and Bee know this, of course, and it must be obvious that putting both bosons and fermions into the same E8 multiplet violates this fundamental principle. That they don't emphasize this simple fact but instead complain about manners is something that I find surprising and quite disappointing.
 
  • #95
Here is what I hope is a concrete example of what I think that Thomas Larsson is saying (please feel free to correct my errors):

If you were to (not what Garrett did) make a physics model by decomposing E8 according to its e17 5-grading:

g(-2) = 14-dim physically being spacetime transformations
g(-1) = 64-dim physically being fermion antiparticles
g(0) = so(7,7)+R = 92-dim physically being gauge bosons
g(+1) = 64-dim physically being fermion particles
g(+2) = 14-dim physically being spacetime transformations

then that would be consistent with spin-statistics because
the products fermion(-1) times fermion(+1) would be gauge bosons(-1+1=0)
the products of gauge bosons(0) times gauge bosons(0) would be gauge bosons(0+0=0)
the products of gauge bosons(0) times fermions(-1) would be fermions(0-1=-1)
the products of gauge bosons(0) times fermions(+1) would be fermions(0+1=+1)

etc

The point is that if you have fermions and bosons mixed up together in the same part of the graded decomposition, you do not get good spin-statistics,
but
it is possible to decompose in a way that you do get good spin-statistics
and
that is something that should be taken into account in model-building.

Tony Smith

PS - Sorry for burying stuff like fermion(-1) times fermion(-1) giving spacetime(-2) into an "etc" (sort of like spinor x spinor = vector) but in this comment I am just trying to make a point and not build a complete model here.
 
  • #96
sambacisse,
The issue is a bit more complicated than it appears because of how the real representations are mixed together in exceptional groups into complex representation spaces, relying on an inherent complex structure. This sort of thing is described halfway through John Baez's TWF253 for the case of E6. When describing so(3,1) reps in terms of sl(2,c) this is further complicated, and when swapping in conjugated anti-fermions it's more complicated still -- because one has to be clear in each step which complex structure one is conjugating with respect to. I thought I had this figured out several years ago, but I don't like to make statements about complicated things without having slowly worked through them in detail. So I've stayed out of the arguments. Of course, I can say that the worst case scenario is that one might have to use a complex E8.

moveon,
Tony addressed this a bit, and I'll try to summarize the specific case in the paper. The E8 Lie algebra may be naturally decomposed into a D4+D4 subalgebra, and everything else. In terms of the number of elements, this decomposition is:
(28+28)+64+64+64
which I don't consider a "grading," but it relates to gradings. The important thing is the Lie brackets. If we label the D4+D4 elements "bosons," and the rest "fermions," the brackets are as Thomas Larsson has helpfully described. Now, if the E8 symmetry is broken such that the "fermion" part of the Lie algebra is pure gauge, then that part of the connection may be replaced by Lie algebra valued Grassmann fields. We end up with a D4+D4 valued connection 1-form field, \underline{H}_1+\underline{H}_2, and three other fields, the first of which is the first generation fermions, \Psi, which are Grassmann valued E8 Lie algebra elements. Because of the structure of E8, the Lie brackets between these give the fundamental action:
[\underline{H}_1+\underline{H}_2,\Psi] = \underline{H}_1 \Psi - \Psi \underline{H}_2
The brackets between two \Psi's are in D4+D4, but these terms vanish in the action. Notice that there is no symmetry here relating the fermions to bosons. That symmetry was destroyed when we broke the E8 symmetry by adding the terms we did to the action. I did that by hand in my paper, and Lee talks about how that can happen dynamically in his. There is a cute trick in the BRST literature whereby these objects can be formally added in a generalized connection:
\underline{H}_1+\underline{H}_2+\Psi
Since I like cute math tricks, I used it -- allowing all fields to be written as parts of this "superconnection," with the dynamics coming from its generalized curvature.
 
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  • #97
So, it seems to me that:

1 - Garrett has shown that his physical identifications of E8 generators are consistent with spin-statistics;

2 - Garrett is not claiming that any BRST ghost-fermions-with-integer-spin are physical,
but
is just using one of the technical "math tricks" from BRST literature in order to construct his "superconnection" containing both gauge boson curvature terms and curvature terms derived from spinor/fermions;

3 - Garrett has explicitly broken full E8 symmetry so that it is irrelevant whether or not Garrett's physics stuff (whether it is Pati-Salam or not) fits inside E8,
so that Jacques Distler's arguments about it not fitting inside E8 are irrelevant.

4 - However, just as Jacques Distler's comments were useful in seeing that E8(8) might be more useful than E8(-24),
it may be that his comments about Pati-Salam vs. the Standard Model might also be useful indicators that Garrett's model should perhaps be put directly in terms of the minimal Standard Model than in terms of Pati-Salam.

Tony Smith

PS - If I had to guess, I would guess that Garrett used Pati-Salam because he thought that it was an established particle physics model, and its use would make his E8 model more acceptable to conventional physicists.
Since it has turned out otherwise, maybe just using the plain vanilla minimal Standard Model plus MacDowell-Mansouri gravity might be a way to go.

PPS - It is unfortunate that a "food-fight" atmosphere has obscured much of the sensible physics in discussions on some parts of the web, and I would like to say that I very much appreciate the moderate (in more meanings than one) atmosphere here on Physics Forums. Such moderation-in-climate does not come about without moderation-in-the-other-sense, and that takes effort, which I appreciate very much.
 
  • #98
Garret,

OK so let me translate this in my language.. your superconnection does not take values in the Lie algebra of E8 as some generators are fermionic (they square to zero, eg).
Therefore the curvature, or field strength does not take values in all of E8, but in D4+D4 only. The full commutation relations of E8 are therefore not non-trivially realized. So in what sense then does E8 play a role? It seems that the purpose of your E8 is to organize, as a bookkeeping device, the fermionic part of the spectrum in terms of the coset E8/(D4+D4), as far as their quantum numbers are concerned.

This is linked to the "breaking" of E8. There are different notions of a symmetry being broken. Usually in particle physics a symmetry is spontaneously broken, which means it is "still there" albeit non-linearly realized. It reflects itself in terms of Ward identities of the low energy effective theory.
There is an energy scale above which the symmetry is restored and the theory is in an "unbroken phase". So one may speak of an "underlying" symmetry.

In contrast, you write a theory where there is no E8 symmetry to begin with (ie, its commutation relations are not fully realized) and there is no energy scale above which it is restored. So calling it "breaking" may be misleading...it is just not there. It is a bit like saying the standard model has monster group symmetry, although most of it is broken.


Tony Smith said:
So, it seems to me that:

1 - Garrett has shown that his physical identifications of E8 generators are consistent with spin-statistics;

...

3 - Garrett has explicitly broken full E8 symmetry so that it is irrelevant whether or not Garrett's physics stuff (whether it is Pati-Salam or not) fits inside E8,
so that Jacques Distler's arguments about it not fitting inside E8 are irrelevant.


To 1- ... they are not the generators of E8. They are the generators of some superalgebra whose bosonic piece is D4+D4.


To 2- ... it seems to me that the claim was that that the standard model spectrum can be organized in terms of E8/(D4+D4) (rather, of the relevant non-compact real forms). That has been shown by Distler not to be the case.


I would thus advise to look for superalgebras instead of E8. There exist even exceptional ones; they have been classified by Katz, and a useful ref is hep-th/9607161. Choosing one with D4+D4 as its bosonic piece (and a suitable real form) may be more successful. Also, superalgebras are consistent with Coleman-Mandula (that's why supergravity works).
 
  • #99
moveon, thanks for that; a very very illuminating comment.
 
  • #100
moveon said:
In contrast, you write a theory where there is no E8 symmetry to begin with (ie, its commutation relations are not fully realized) and there is no energy scale above which it is restored. So calling it "breaking" may be misleading...it is just not there. It is a bit like saying the standard model has monster group symmetry, although most of it is broken.

To 1- ... they are not the generators of E8. They are the generators of some superalgebra whose bosonic piece is D4+D4.

To 2- ... it seems to me that the claim was that that the standard model spectrum can be organized in terms of E8/(D4+D4) (rather, of the relevant non-compact real forms). That has been shown by Distler not to be the case.

The full E8 symmetry would seem to be E8/D8, I personally am more familiar with E8/E7xSU(2) and so on down the A-D-E series but maybe one can do something with E8/D8. The D4+D4 part seems after symmetry breaking so one should not expect any E8/(D4+D4) physics.
 
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