Quote by Urs
Concerning Matrix Models, since they are nonperturbative, there is no need to pick any background. They pick their own solutions. That's what the papers that I was referring to tried to compute, namely the (maybe unique?) solution of the IKKT model. Of course it hasn't been done yet, obviously, but the fact that the IKKT model for one is conceptually exteremely simple and, for finite size N of the matrices, effectively calculable. You should endorse that, because if it turns out that the unique solution to IKKT is not phenomenologically realistic, then that's it.
On the other hand, I would find it hard not to be fascinated by a working theory of quantum gravity in any number of dimensions > 3. That's what I find so hard to understand about the criticism of string theory. If nothing else, there is lots of theoretical insight in string theory. If it really describes our world is a completely different issue. Lots of field theories are also studied only for theoretical reasons, having nothing directly to do with the real world. I don't want to wait for the unique prediction of my telephone number until I consider to find progress in quantum gravity interesting.

I'm no expert on the IKKT model, so don't know exactly what the problems with it are. If it really did give a welldefined, backgroundindependent, nonperturbative formulation of Mtheory, one that seemed to lead to dynamically determining a plausible background, my guess is that everyone in the field would be working on it. As far as I can tell, most people have lost interest in it. When that happens there's generally a good reason. Unfortunately I doubt that killing the IKKT model would kill the whole string/Mtheory field.
I'm not claiming string theory is completely uninteresting. I am claiming it is overhyped and it has become difficult for young people to make careers working on anything else, which is very unhealthy. The reasons I don't believe in string/Mtheory 11d supersymmetric unification are twofold:
1. It's really complicated and ugly
2. It not only doesn't predict your phone number, it doesn't predict anything at all.