I don't understand this very well either, but I'd like to. I think it's key for understanding MWI's claim to be local.
Simple question for whoever: in what sense precisely does something like an N-particle-wave-function or a quantum field in QFT "live" in space-time? Certainly not in any obvious way at all, right?
I'd like to know what kind of geometrical object it is, exactly. I mean, some arbitrary state in QFT definitely does *not* attribute some particular field value to each point on spacetime. A state is not a field *configuration* in the classical sense. It is, rather, an arbitrary superposition of such configurations. So suppose we have such a thing and it evolves deterministically according to a Sch equation forever. Is this "local"?
Egad. As soon as you go solipsist on me, I stop believing that this can possibly be consistent, in any serious way, with relativity. All this talk of consciousness interacting with... If you take this seriously, isn't the whole idea of a 3+1 universe just one of those delusions in our minds??? etc....