Lee Smolin's LQG may reproduce the standard model

[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