heinz said:
(1) This paragraph is really dynamite.
(2) Christoph, I still cannot swallow the idea that putting together quantum theory and general relativity is supposed to be as easy as you state here. Thousands of people have tried this without success for almost 100 years, and you state that it the problem is solved in any model for which hbar, c, and G are the same for all observers!? You talk as if this is a student exercise!
(3) And what would this mean for LQG, superstring theory, M theory, Bilson-Thompson, Horava gravity, etc.?
To (1): It is not dynamite; it is just a proposal for a solution. There is nothing violent; take it easy!
To (2): Again, take it *easy* ! In fact, in this case the expression is reallly appropriate. Any unified model must realize certain requirements:
- it must reproduce black hole entropy,
- it must keep c, hbar and G invariant,
- it most probably must contain extended constituents,
- it most probably must have as few new concepts as possible,
- it must explain Lagrangians and the principle of least action,
- it must explain the three gauge symmetries,
- it must explain generations, particle masses, mixings and couplings,
- it must be impossible to modify (or "hard to vary").
This is the riddle nature puts in front of us in fundamental physics. The tough part of the riddle seems to be to state it. You are right to say that the second requirement is an unusual formulation that is equivalent to the requirement
- it must contain general relativity and qauntum field theory.
The "invariant c, h, G" formulation is unusual. But it makes finding the solution much simpler. Solving riddles always depends on the best possible tools, and on finding a formulation that makes the riddle sound as simple as possible. This might be unusual, but it is not "dynamite".
The strand model, with its simple basic postulate, is a candidate solution to the riddle, because it seems to answer each requirement. The strand model also has a clear experimental signature, namely a "desert" up o Planck energy, including a lack of Higgs bosons. Let's see what the LHC and the other experiments will bring us.
Let me comment on another point:the 100 years of effort. The standard model is from the 1960s (and indeed involved thousands of people). Black hole entropy is from 1973/1974. The equivalence of belt trick, quantum theory and tangle description is from 1980. The equivalence of gauge theory with deformations is from 1983/1984. Extended constituents are from the 1980s. The thermodynamics of space-time is from 1995. The invariance of c°4/4G is from 2000. This implies that the last ideas are fairly new: only since a few years is it possible to state the requirements for unification with the words given above. It would not have been possible to state this list before 2000. In other words, the "simple" formulation of the riddle is only a few years old.
It does sound as a student exercise - but then, all physics must sound that way. The many people behind the invariance idea, Planck, Lorentz, Einstein, Bohr, Gibbons, and others, were essential in allowing this simple formulation.
The strand model takes all these simple formulations, adds a few new results - such as the realisation of SU(3) and SU(2) with deformable bodies and the connection to the Reidemeister moves - and proposes a solution for unification that is presented in
http://arxiv.org/abs/0905.3905 and http://www.motionmountain.net/research . The biggest novelty might be that U(1), SU(2) and SU(3) are *not* seen as the part of a sequence that includes SU(5), SO(10), E(8), S0(32) or another gauge groups. Instead, the strand model proposes that the three gauge groups are due to the three Reidemeister moves, and thus that there are no other gauge groups in nature.
To (3): As long as a model fulfils the requirements, it is a candidate for a unified model! I can only encourage everybody to play around with the requirements and come up with other candidates. It is fascinating and rewarding.