On Saturday, May 26, 2018 at 4:33:27 AM UTC, Bruce wrote: > > From: <[email protected] <javascript:>> > > > On Saturday, May 26, 2018 at 12:06:53 AM UTC, Bruce wrote: >> >> From: <[email protected] >> >> On Wednesday, May 23, 2018 at 8:16:07 AM UTC, Bruce wrote: >>> >>> From: <[email protected] >>> >>> 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
