[deleted]
Tom,
The problem is that if you want to work with greater symmetry you have to go to higher dimensions. A group SO(n) will describe a larger number of states in a symmetry for larger n. I will be honest with you, I think that the universe has a grand symmetry that is utterly enormous. The basic group is the Mathieu group in 24 dimensions, where this exists in an extended Lorentzian spacetime of 26 or 27 dimensions. I will not quibble about the difference here. This system turns out to be an automorphism of the Monster group. The root space for the Mathieu group is 186560 dimensional, where for most physics which might be of value is 1488 dimension --- and this is really highly abstract physics beyond current string theories. Then for various reasons this roots space has to be extended to 186883 dimensions to define the monster group automorphism. Now the monster group is utterly enormous with some ~ 8.1e^{51} dimensions. To be honest this is what I think might be the most fundamental theory possible.
Now obviously it would be crazy to try to write up a theory based on the monster group. At least at this time we have absolutely no basis to draw upon to work with this. So I am content to work in the restricted versions of the Leech lattice (Mathieu group) that connect up with string theory, and to lay down what I think are the extensions of string theory. A part of this involves discrete systems in continuous structures, and certain insight in how time is a quantum field effect. Yet clearly it would be silly to attempt to write up some complete description of the universe according to some grand final (monster) theory. We have to crane things up from physics we have some connection with to the next step and then eventually go up from there to the step beyond that.
Cheers LC