On Wednesday, May 30, 2018 at 9:24:51 AM UTC, Bruno Marchal wrote: > > > On 28 May 2018, at 22:31, agrays...@gmail.com <javascript:> wrote: > > > > On Monday, May 28, 2018 at 5:24:22 PM UTC, Bruno Marchal wrote: >> >> >> On 26 May 2018, at 06:50, agrays...@gmail.com wrote: >> >> >> >> On Saturday, May 26, 2018 at 4:33:27 AM UTC, Bruce wrote: >>> >>> From: <agrays...@gmail.com> >>> >>> >>> 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* >> >> >> 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 everything-li...@googlegroups.com. >> To post to this group, send email to everyth...@googlegroups.com. >> 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 everything-li...@googlegroups.com <javascript:>. > To post to this group, send email to everyth...@googlegroups.com > <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 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.
