On Sunday, June 3, 2018 at 2:23:46 AM UTC, [email protected] wrote: > > > > 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 previously noted, the formula you meant to write is: > (|+>|A+>|O+>|e+> + |->|A->|O->|e->). What thought experiment would be > appropriate to understand either of the environmental states? AG* >
*Does |e+> represent the eigenstate of the universe, excluding the particle being measured, the apparatus and the observer, when the spin is measured UP? That is, what is the physical content and meaning of |e+> within the standard formalism of QM? AG* > > >> 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 |->). 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. >> >> 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.
