Anything to do with heavy ions should keep in mind the difference between new "fundamental" physics, and new physics at the level of QCD with a condensed matter flavour. QCD interactions with that many particles is pushing the theory into less well-studied phases, and one should not be too...
@tom: I don't think there needs to be a problem. As usual, the starting point is to pick an ensemble, which matches a known set of constraints (and which experimentally is known to be sufficient to predict some other set of observables). All that is required is a known set of physically distinct...
Indeed TQFT's seem to have very little contact with "conventional" QFT observables, and therefore theory. Atiyah proposed some straightforward axioms (http://en.wikipedia.org/wiki/Topological_quantum_field_theory#Atiyah-Segal_axioms) but experts do not entirely agree with them (too restrictive...
It's my understanding of Rovelli's view.
As far as theorems go, one should always be very careful. I'm not perfectly intimate with said theorem, but let me outline one possible "get out clause". The spin foams are not generally covariant when one considers any truncation, i.e. any...
It is not truly unique in any precise sense at the moment. I was simply addressing the concerns that student had. The broader picture was given by Rovelli --- we're looking for *a* theory, not *the* theory.
Guess, then check with experiments.
I had a comment on that if only I was there! The student is confused about whether small or large gamma is the classical limit. He thinks that since the "classical" Lagrangian is without the topological term, the correct limit is with gamma going to infinity (since it appears as a 1/gamma...
It seems I misunderstood the request. Good thing marcus is reliable :-)
As far as "true" goes, no one knows. We merely have a theory that might be (strong, but not direct evidence) self-consistent, and consistent with classical GR. That is all.
Also, as far as references go, I would say...
I think you are confused about how the discretisation really works, especially in the presence of Yang-Mills (and attendent fermion) fields. I would suggest taking a look at the lattice QCD literature, and understand how (classical) loop variables work. Intuitively, we write a basis for the (in...
Perhaps this attempt at a historical summary will help: http://physics.stackexchange.com/questions/23474/ionic-vs-covalent-bonds-dividing-line/23479#23479
I have to say, I think this lecture series is fantastic. Nevermind whether the 4D Lorentzian theory is actually true, I think this might be the largest "airing" of the work that the loop community has done. There are *lots* of mathematical theorems which are interesting in and of themselves ---...
I think they (Rovelli and Asheketar) are discussing different aspects. Rovelli's point is only that using the tetrad/triad formalism brings the action into a polynomial form, and which looks similar to local gauge theories, which is good because we kind of know how to do quantisation of those...
One needs to keep in mind that an amplitude is always associated with a boundary state. If you keep adding vertices then eventually the only way to satisfy the tetrahedral inequalities will be to force some faces to be of zero size due to area quantisation. In other words, you can't actually...
It would solve both. The sums that are in Eq 25 of that paper become completely finite --- there are literally only a finite number of terms which contribute.