my view on questions about quantum mechanics and relativity is similar to the one given by Steven Weinberg: We incurred in the fundamental laws of nature entailing exactness. So, I personally avoid to try to find what is behind them but rather I like a reformulation work as I did quite recently in http://arxiv.org/abs/1201.5091. Given this, I respect the work of colleagues that think differently from me but, of course, I would appreciate to see a couple of conditions to be satisfied:

1) Concrete models.

2) Experimental predictions to check the idea.

Given these, I could admit that a search for a deeper layer to quantum mechanics or relativity should prove to be viable. So far, I have never seen both conditions met.

Marco

Now I see your point. No, I cannot claim that any many-body quantum system becomes a classical system (I did not do it anywhere), on the basis of these theorems, but that a quite generic effect exists in the limit of an increasing numbers of particles. This is also stated in my post but I think it should made clearer. My take is that such an effect is real, we seem to agree on this, and goes somehow in the direction ‘t Hooft took. But it does not prove him right either for such an extremist take. Maybe, his theory is in need for further work.

Marco