Comment Re:Computable? Simulatable? (Score 1) 199
That's exactly right. I just finished reading the paper. He's basically saying that we don't know what the Schrodinger equation predicts for macroscopic systems, because it's completely impossible to do the calculation and find out. Actually, whether P=NP doesn't really matter as far as that goes. Whether or not it will some day be possible to do the calculation, thus far we haven't done it, so we don't know what the result is. We shouldn't go around making claims about half-dead/half-alive cats when we have no idea whether QM predicts that or not.
There's a bit more to the paper than that. It has two main parts. The first is a proof that solving the Schrodinger equation is NP-hard. He then considers the case of a simple test system (for which we can solve the Schrodinger equation) coupled to a complex environment (for which we can't). He makes some heuristic arguments based on a set of reasonable sounding approximations, and shows that they lead to the standard probabilistic behavior and wavefunction collapse for the test system.
I don't think any of this is really new. It's just a different way of looking at decoherence. Still, it makes interesting reading.