On Thu, Feb 18, 2021 at 2:21 PM 'Brent Meeker' via Everything List < [email protected]> wrote:
> On 2/17/2021 6:46 PM, Bruce Kellett wrote: > > On Thu, Feb 18, 2021 at 1:05 PM 'Brent Meeker' via Everything List < > [email protected]> wrote: > >> On 2/17/2021 4:29 PM, Bruce Kellett wrote: >> >> Thus previous experience is no guide to the future in MWI. I know this is >> true also in ordinary classical probability theory, but the difference is >> that in MWI, one or more of your successors is bound to see the atypical >> sequences -- that is not guaranteed in classical probability theory. It >> *might* happen, but it is not *bound to* happen. This difference is >> important. >> >> >> I don't think it's even relevant. It isn't "bound to happen" to you. >> It's just a possibility for you, just as it is in the Kolmogorov sample >> space. >> > > > This is the problem with personal identity in many worlds -- the copies > are all *you*, so your comment is without force. You are sneaking in the > collapse that Sabine mentions; or you are making a dualist assumption -- > only one of the copies is *really you*. > > > I don't think so. Every copy post-test is some copy of you pre-test. The > Everett explicitly writes the post-test wave function with all the you's in > it. I don't see that as any more problematic than referring to possible > you's pre-test. In any probabilistic theory only one possibility is > realized > That is where you keep slipping in the implicit collapse (or dualist identity hypothesis). In MWI it is just not the case that only one possibility is realized. > ...that doesn't mean we have to assume there was some realism-spirit that > got passed to it. > If you don't like dualism, then you are left with an implicit collapse hypothesis. There are no other options in MWI. > > <........> > >> >> Yes. I think that the idea that Bob has been pursuing is a >> definite non-starter. Carroll is smart enough to see this, even though he >> does want to finally reduce probability to branch counting. The real >> trouble I see with Sean's approach is that he has to call on Born rule >> insights to know how many additional branches to manufacture. His >> approach is irreducibly circular. >> >> >> But then he could just postulate the Born rule as the way to partition, >> or create, branches and it would work; which is what Sabine says. And that >> tells me that the Hemmo and Pitkowsky objection is wrong. >> > > > That is what Carroll and Bob are doing. But that rather defeats the > purpose of deriving the Born rule from the Schrodinger equation alone. All > such arguments are inherently circular. > > > I agree with that. Do you agree that it would work to simply add the Born > rule to MWI as a postulate? > I have difficulty seeing how that could work. For the Born rule to work, the dynamics have to 'see' the amplitudes rather than just the eigenstate basis vectors. But this does not happen in Everett. The set of histories arising in N repetitions of the spin measurement is the same for any two-component initial state -- there is no differentiation of the histories according to the Born probabilities. You have attempted to remedy this by assuming that the number of branches on each trial splits in the Born rule ratios. But this is inconsistent with unitary evolution and the MWI. You might be able to construct a many worlds theory that has the Born rule as an independent postulate -- but the resultant theory will not be quantum mechanics as we know it. I doubt that it can even be unitary. 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/CAFxXSLSgYLYjRDBnhHUs2Bd1%2Bdk0Cyq1RLobMS9BLZ9vajt3WA%40mail.gmail.com.
