On Saturday, May 26, 2018 at 4:33:27 AM UTC, Bruce wrote: > > From: <agrays...@gmail.com <javascript:>> > > > On Saturday, May 26, 2018 at 12:06:53 AM UTC, Bruce wrote: >> >> From: <agrays...@gmail.com >> >> On Wednesday, May 23, 2018 at 8:16:07 AM UTC, Bruce wrote: >>> >>> From: <agrays...@gmail.com >>> >>> OK, but how does one jump to the assumption of other worlds? Doesn't >>> each "branch" exist in this world? AG >>> >>> >>> Initially yes. But decoherence diagonalizes the density matrix FAPP, so >>> the other branches become unreachable. That is what one means by separate >>> worlds. >>> >> >> *I am tentatively OK with this conclusion (tentatively until I examine >> the mathematics and verify it), as long as these separate "worlds" do NOT >> contain copies of THIS world. It's the copying that I find hugely >> extravagant, ridiculous, and erroneous! Can decoherence theory be >> consistent without the "copying" claim? Is this the view you adopt to keep >> your sanity? TIA, AG* >> >> >> The fact that the whole world is copied in each branch of the MWI is a >> simple consequence of the mathematics. If one has a state >> >> |psi> = (|+> + |->) >> >> that one measures, which is a superposition of two possible outcome >> states, |+> and |->, then schematically this measurement process looks like >> >> |psi>|A>|O>|e>, >> >> where |A> is the apparatus, |O> is the observer, and |e> is everything >> else, namely the environment. Unitary evolution takes this to: >> >> (|+>|A+>|P+>|e+> + |->|A->|O->|e->) >> >> where |A+> means the apparatus register the |+> result, |O+> means the >> observer sees the |+> result, and |e+> means that information about the |+> >> result leaks into the environment by decoherence and is effectively >> recorded there many times. Similarly for the other |-> branch. >> >> As one can see immediately, this evolution necessarily means that >> everything is duplicated, the apparatus, observer, and the rest of the >> world, differing in the two branches only in consequence of the different >> measurement results (|+> or |->). >> > > *How does disjointedness of the branches follow? AG* > > > Decoherence in the separate branches leads to the approximate > diagonalization of the density matrix. Read about it in Wikipedia or > Schlosshauer's paper/book. >
*I've started to read the Schlosshauer paper Brent posted. AG* > > Decoherence does not cause the "copying", the copying is a result of the >> Schrödinger equation. Decoherence occurs independently in each branch, as >> can be seen in the above schematic outline of the process. >> > > *Not to quibble, but the copying seems to be the consequence of unitary > evolution, not the Schrodinger equation.* > > > The Scrödinger equation embodies unitary evolution. > > * In any event, how does this situation differ from advanced waves in EM > theory, in that the mathematics seems to imply something that doesn't > exist? AG* > > > There is no connection between the two things. > > Look, if you don't want to believe in the many worlds interpretation of > QM, then that is your prerogative. I was merely outlining the mathematics > that leads many people to think that this is the simplest understanding of > the situation. > *Right. I was just making the observation that when we don't see advanced EM waves (coming from the future?), it's generally not seen as a big deal and they're ignored. But when decoherence or the MWI implies the creation of full-blown worlds (that we can't observe), there seems to be a large body of opinion that accepts this bizarre result without serious criticism that there's no mechanism or process for creating full-blown worlds. No. I don't believe in such worlds. I tend to think a large segment of professional physicists have gone mad. AG* > > Bruce > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
