On Saturday, May 26, 2018 at 4:50:37 AM UTC, [email protected] wrote: > > > > On Saturday, May 26, 2018 at 4:33:27 AM UTC, Bruce wrote: >> >> From: <[email protected]> >> >> >> 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. >> > *Yes, but when using spin wf's, there is no explicit use of the S. equation; rather, it seems, another principle is invoked; namely, that when a quantum system has several possible states as a result of measurement, the wf before measurement is a superposition of those states. How is this principle or prescription connected to the S. equation, or is it independent, and if so, on what basis? I think it's just the principle of superposition, which seems independent of the S. equation. AG*
> >> * 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.
