On Sat, Feb 8, 2020 at 11:51 AM Lawrence Crowell < [email protected]> 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 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 -- 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/CAFxXSLSRV8j90AO4G0Vn5rKxuZc4w5U0P%3DPLnzFBGxiZLqYvdQ%40mail.gmail.com.
