Lee Smolin's LQG may reproduce the standard model

[marcus]

Bilson updated his article Oct 26, 2006

http://arxiv.org/abs/hep-ph/0503213

A topological model of composite preons

Thanks for flagging that!

The paper has been substantially rewritten at least in the introduction and the conclusion sections. Also a new section was added called
"Unresolved Issues"

It seemed sufficiently different to print out the new version.

Maybe we should have a thread about the new version, just to call attention to it.

 

[R.X.]

Any candidate preon theory must address particle chirality and T'Hooft anomaly matching constraints...

Only too true.. that's why the Rishon model of Harari took a sudden nose dive, namely when it was realized by his student Nati Seiberg that the anomalies do not match. It simply disappered since then.

This is what I thought til today. However, in the paper 0503213 mentioned above it made a surprise reapperance:

"The rishon model explained the number
of leptons and quarks, the precise ratios of their elec-
tric charges, and the origin and nature of colour charge.
The helon model does all this, but in additionin the framework of Loop Quantum Gravity [11]...
"

Christ... but well, it kind of makes sense. Since LQG people do not seem to care about anomalies, why bother and not re-introduce an inconsistent preon theory?

 

[bananan]

Only too true.. that's why the Rishon model of Harari took a sudden nose dive, namely when it was realized by his student Nati Seiberg that the anomalies do not match. It simply disappered since then.

This is what I thought til today. However, in the paper 0503213 mentioned above it made a surprise reapperance:

"The rishon model explained the number
of leptons and quarks, the precise ratios of their elec-
tric charges, and the origin and nature of colour charge.
The helon model does all this, but in additionin the framework of Loop Quantum Gravity [11]...
"

Christ... but well, it kind of makes sense. Since LQG people do not seem to care about anomalies, why bother and not re-introduce an inconsistent preon theory?

I recentally added this to wiki.

Bilson-Thompson has recently updated his paper dated October 27, 2006, [[18]] and acknowledges that his model, while not preon in the strict sense of the term, nevertheless is preon-inspired model, and is open to the possibility other more fundamental theories, such as M-Theory, may account for his topological diagrams, as well as the Higgs boson and gravity. The theoretical objections that apply to classic preon models do not necessarily apply to his preon inspired model, as it is not the particles themselves, but the relations between his preons (braiding) that give rise to the properties of particles. In this newer version of his paper, he has added a new section, section IV, called "unresolved issues" and acknowledges that open issues include mass, spin, cabbibo mixing, and grounding in a more fundamental theory. He states that grounding preons in M-theory is a possibility, as well as loop quantum gravity.

 

[bananan]

Only too true.. that's why the Rishon model of Harari took a sudden nose dive, namely when it was realized by his student Nati Seiberg that the anomalies do not match. It simply disappered since then.

This is what I thought til today. However, in the paper 0503213 mentioned above it made a surprise reapperance:

"The rishon model explained the number
of leptons and quarks, the precise ratios of their elec-
tric charges, and the origin and nature of colour charge.
The helon model does all this, but in additionin the framework of Loop Quantum Gravity [11]...
"

Christ... but well, it kind of makes sense. Since LQG people do not seem to care about anomalies, why bother and not re-introduce an inconsistent preon theory?

What sort of anomalies do you have in mind, in LQG?

 

[R.X.]

What sort of anomalies do you have in mind, in LQG?

Anomaly matching refers to chiral anomalies.

But yours is a tricky question, because it has been suggested (from what I gather from Thiemann's and other's papers), that anomalies simply do not exist in LQG, due to the kind of quantization procedure applied there.

One can only wonder how a standard quantum field theory that suffers from chiral anomalies and thus is inconsistent (gauge invariance broken, longitudinal modes do not decouple, path integral and thus correlation functions ill defined) should suddenly become consistent when treated with those methoids ...well, frankly they do not make much sense, see comments in Distlers' and Helling's blogs.

I think the least what one would require from any extension of ordinary QFT that it should reproduce the known features of QFT, and not plainly contradict them.

 

[selfAdjoint]

think the least what one would require from any extension of ordinary QFT that it should reproduce the known features of QFT, and not plainly contradict them.

Well, reproduced or better the RESULTS but there's no requirement to reproduce the details of the calculations. Particle physicists have over the decades taught themselves to believe six impossible things before breakfast, like Popov ghosts for example.

And this may be off base, but isn't the problem with QCD that it theoretically should have a chiral anomaly but phenomenologically doesn't, so they have to speculate on fine tuning schemes (like axions) to carefully cancel out the anomaly by two counterterms?

 

[R.X.]

Well, reproduced or better the RESULTS but there's no requirement to reproduce the details of the calculations. Particle physicists have over the decades taught themselves to believe six impossible things before breakfast, like Popov ghosts for example.

What's wrong with this neat computational trick? It is simply a clever way to deal with gauge fixing. No one ever has claimed that FP ghosts would be more than ficticious degrees of freedom and be at the same level es eg electrons. The rules of QFT work so well so that one can call it the most accurate theory of all of natural sciences. And giving up proven fundamental principles, like requiring the path integral be well defined, without very very strong reasons does not hold a lot of promise.

And this may be off base, but isn't the problem with QCD that it theoretically should have a chiral anomaly but phenomenologically doesn't, so they have to speculate on fine tuning schemes (like axions) to carefully cancel out the anomaly by two counterterms?

I don't know what you mean. Perhaps there is a confusion between global and local anomalies? Perturbative QCD at high energies is a very well established and experimentally proven theory, it is pointless to argue against its validity.

Frankly, in order to understand these things and hopefully proceed with one's own research in the future, there is no way other than really learning this stuff from the ground, and this takes many years of hard work. I understand the temptation to avoid this by simply declaring the results of many thousand hard working people as misguided, failed and not even wrong, in order to cook up "alternative" theories that are in contradiction with those results.

Well, science just works in a different way, and those who don't recognize this won't get anywhere.

 

[Careful]

The rules of QFT work so well so that one can call it the most accurate theory of all of natural sciences. And giving up proven fundamental principles, like requiring the path integral be well defined, without very very strong reasons does not hold a lot of promise.

I always love this argument, especially when it is known that all QED results such as Lamb shift, g factor, Casimir effect ... can be derived by treating the EM field classically while obtaining similar precision. Nobody really argues that the results of QED and QCD don't come out well perturbatively, but another thing is to appreciate this fact for the right reasons ! The latter might very well shake up some fundamental assumptions seriously (actually I am sure of this). But I agree with you, on the other hand, that in doing so you must always keep QED in mind and progress comes in small steps. I moreover concur that ``background independence'' is not going to solve the problems at hand. On the other hand, there are very good reasons from the theoretical side to protest against QED : sometimes it is good to go against something in order to learn to appreciate it for the right reasons, progress often comes from that direction.

Careful

 

[Kea]

And giving up proven fundamental principles, like requiring the path integral be well defined, without very very strong reasons does not hold a lot of promise.

Indeed.

 

[Chronos]

I'm not willing to surrender SA's point without resistance. Careful is very bright but a bit reckless, IMO. Going against things is all about science, going through the motions is another matter.

 

[Careful]

I'm not willing to surrender SA's point without resistance. Careful is very bright but a bit reckless, IMO. Going against things is all about science, going through the motions is another matter.

A bit reckless ?? Oh yes, I forgot that those who point out that we need to get a better understanding of the calculations we know to work and point out that some fundamentals behind it might be wrong are always guilty. It is indeed much more rewarding to say that everything is more or less correct, work with self contradictory principles and do something which only adds an esthetic argument to the discussion : ``background independent´´ cutoff, instead of a ``naive'' cutoff in some Lorentz frame.

 

[garrett]

No one ever has claimed that FP ghosts would be more than ficticious degrees of freedom and be at the same level es eg electrons.

Err, actually, someone did claim that.

 

[selfAdjoint]

And this may be off base, but isn't the problem with QCD that it theoretically should have a chiral anomaly but phenomenologically doesn't, so they have to speculate on fine tuning schemes (like axions) to carefully cancel out the anomaly by two counterterms?

I don't know what you mean. Perhaps there is a confusion between global and local anomalies? Perturbative QCD at high energies is a very well established and experimentally proven theory, it is pointless to argue against its validity.

This is what I meant:

http://adsabs.harvard.edu/abs/2003APS..SES.DC001G

 

[R.X.]

This is what I meant:

http://adsabs.harvard.edu/abs/2003APS..SES.DC001G

Hm.. I am not able to get hold a copy of that one... it appears not to have been submitted to arXiv, which is suspicious.. But at any rate, there is definitely no problem that QCD would be inconsistent due to local (gauge) anomalies. The whole particle physicist's world would be in turmoil...

As far as global anomalies are concerned, they are not important for consistency per se, but they serve as a device to check whether a preon model is consistent: the global anomalies of the constituents must match those of the bound states.

Actually, I was perhaps a bit too harsh, in that the author of that paper didn't claim to consider a real preon model any more. So the rules of the game with regard to anomalies are unclear; in particular since the issue of anomalies in LQG is (IMHO) unclear. Thus no conclusions can be drawn at this point. One just should be wary that "new" approaches should not be in contradiction of known facts, rather they should complement them.

 

[selfAdjoint]

Hm.. I am not able to get hold a copy of that one... it appears not to have been submitted to arXiv, which is suspicious.. But at any rate, there is definitely no problem that QCD would be inconsistent due to local (gauge) anomalies. The whole particle physicist's world would be in turmoil...

R.X., This is not some marginal crank theory. See this wiki entry on axions, for example. Nobody says QCD is in turmoil, but there is this long-standing, well-known uncertainty within it. http://en.wikipedia.org/wiki/Axion

 

[Kea]

cross link

Returning to the discussion of CarlB's work, we should link to the thread:

https://www.physicsforums.com/showthread.php?t=46055&page=21