On Wednesday, May 30, 2018 at 9:24:51 AM UTC, Bruno Marchal wrote: > > > On 28 May 2018, at 22:31, [email protected] <javascript:> wrote: > > > > On Monday, May 28, 2018 at 5:24:22 PM UTC, Bruno Marchal wrote: >> >> >> On 26 May 2018, at 06:50, [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. >>> >>> * 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* >> >> >> Good. In the expression “many-worlds”, the problem is indeed in the >> notion of worlds, not in “many”. Both the mathematical reality and the >> physical reality contains many “many”. That’s why there are quantifiers >> like “for all”, and "it exists". >> >> But the reason why we expand the relative states into “worlds”, is that >> the mathematics of the SWE, or just unitarity, entails that those parallel >> histories are as real as ours. >> > > *Then you completely missed my point about advanced EM waves. The > mathematics indicates they exist, but they don't! So why do you place such > faith in mathematics? * > > > The experiments do not confirm them. With the superposed states, or with > the SWE, which lead to the many-histories, we take the math seriously > because they are back-up by the experimental evidence. >
*How can you have experimental evidence for many worlds if they are disjoint from this world? AG * > *When mathematics points to things which don't exist, it's usually, maybe > always, the consequence of some unstated, erroneous assumption in its > application. As I previously explained, it's a fallacy to apply the > principle of superposition of states to entities that fail to have well > defined deBroglie wave lengths (and which therefore can manifest > interference) -- such as cats in a box, or instruments, or "environments". > That's what Schrodinger warned us about, but the lesson has yet to sink in. > AG* > > Then quantum mechanics is false somewhere in between the observed and the > observer, but there are no evidences to back that claim. One history is no > less speculative than many one, and one history makes no sense with the SWE > for which evidences abound. Then, simple independent hypothesis leads > directly to many histories, so QM as known today do confirm those > independent hypothesis, like mechanism in the cognitive science (not in > physics). > *CMIIAW, but I think Everett used superpositions of macro states similar to what Bruce wrote earlier, where sums of tensor products are formed using the apparatus and environment. All I claimed above is NOT that quantum mechanics is false, but rather than one cannot form a legitimate superposition with entities that have no well defined deBroglie wave length -- since the existence of a well defined wave length is a necessary condition for interference, and that's the core property of a superposition. So, if you indulge this error you will get nonsense, such as a cat which is simultaneously alive and dead. AG* > > Bruno > > > > > > >> Now, if you don’t like worlds, you should love mechanism, as those >> histories are only *many* computations seen “from inside”. In that case we >> need not to assume more than very elementary arithmetic for the ontology. >> For the phenomenology all theories are highly incomplete and we can explore >> a lot, but the complexity and unsolvability cannot be bounded. The >> universal machine is a unknown which invites itself to the dialog. >> >> Bruno >> >> >> >> >> >> >>> 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. >> >> >> > -- > 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] <javascript:>. > To post to this group, send email to [email protected] > <javascript:>. > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > > > -- 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.
