> On 8 Feb 2020, at 02:28, Lawrence Crowell <[email protected]> > wrote: > > On Friday, February 7, 2020 at 7:10:54 PM UTC-6, Bruce wrote: > On Sat, Feb 8, 2020 at 11:51 AM Lawrence Crowell <[email protected] > <javascript:>> wrote: > On Friday, February 7, 2020 at 6:16:45 PM UTC-6, Bruce wrote: > On Sat, Feb 8, 2020 at 4:33 AM Stathis Papaioannou <[email protected] <>> > wrote: > On Fri, 7 Feb 2020 at 15:59, Bruce Kellett <[email protected] <>> wrote: > > This argument from Kent completely destroys Everett's attempt to derive the > Born rule from his many-worlds approach to quantum mechanics. In fact, it > totally undermines most attempts to derive the Born rule from any branching > theory, and undermines attempts to justify ignoring branches on which the > Born rule weights are disconfirmed. In the many-worlds case, recall, all > observers are aware that other observers with other data must exist, but each > is led to construct a spurious measure of importance that favours their own > observations against the others', and this leads to an obvious absurdity. In > the one-world case, observers treat what actually happened as important, and > ignore what didn't happen: this doesn't lead to the same difficulty. > > > Carroll and Sebens worked a paper a year ago illustrating how MWI was > consistent with Born rule. They did have to restrict paths or states that > were too far removed from being a good Bayeisan prior, so it is a bit loose. > However, it was not bad. > > Not bad!!!! I suppose if you feel justified in just throwing away anything > that does not suit your favourite theory, then you can get away with > anything. It is the fact that these 'worlds' that are far removed from what > one wants to see cannot just be "thrown away" that destroys MWI. Given that > the probability of particular outcomes no longer has meaning when all > outcomes necessarily occur, one cannot use any observed data to justify any > theory about the probabilities. All theories are just as good, or just as > bad. Consequently, assuming probabilities for particular outcomes no longer > makes any sense. > > > The set of amplitudes or paths thrown away is a small measure. The bounds are > not entirely certain, but they are comparatively small. > > > The inability to define a clear probability to a particular world path is > argued to be one reason that MWI is the best interpretation to work quantum > gravitation. This is a sort of nonlocality. I am not sure this clinches MWI > as the clearly superior interpretation. Much the same nonlocality can be > identified with quantum spacetime if it is built up from quantum > entanglements, thus avoiding the use of an interpretation. > > I doubt that anything along these lines is going to resolve the basic problem. > > MWI is sworn by a number of physicists, though Copenhagen still holds it own > and Qubism is growing adherents. Qubism actually also has a few things going > for it. I frankly see all of these as ancillary postulates that have limited > usefulness and mostly useful in expositories. > > Perhaps some interpretations make more sense than others. It seems, from the > considerations that I have raised, that, despite what many physicists say > about MWI, it is a failure as an interpretation of QM -- it does not allow > one to use experimental data to evaluate the theory one way or the other. As > Kent says, "Everettian quantum theory is essentially useless, as a scientific > theory, unless it can explain the data that confirms the validity of standard > quantum mechanics." And Everett cannot do this. > > Bruce > > The operative word is theory, and I do not see quantum interpretations as > theories.
I can agree if you agree that “0 worlds”, “1 world”, … omega worlds, aleph_1 worlds, … are *all* metaphysical interpretations. Yet I think that the discussion concerns two different theories. Roughly put it is 1) SWE and 2) SWE + collapse. In all models/intepretation of QM with have the MW, and that is why the Copenhagen theory is mainly a theory which says that the SWE is wrong and must be limited, but nobody has found a clue of why and where such a cut occur. With only the SWE, the worlds/histories are just the terms in the superposition, and they provably exist (= are solution of the SWE). > They are more in a sense metaphysics used to provide some explanatory means > to makes QM more understandable to our classical brains. As long as we bandit the theories when refuted that is OK. A today interpretation can become a tomorrow theory, by adding or subtracting some axioms. Interpretations can be tested too, even if it is usually more difficult. Bruno > > LC > > -- > 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] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/e47cec7d-0516-40c1-9677-714039c5d798%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/e47cec7d-0516-40c1-9677-714039c5d798%40googlegroups.com?utm_medium=email&utm_source=footer>. -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/A4C4E5EF-51BA-494A-B54C-0E3C9FB909B3%40ulb.ac.be.
