On Tue, Feb 18, 2020 at 11:37 AM 'Brent Meeker' via Everything List < [email protected]> wrote:
> On 2/17/2020 4:09 PM, Bruce Kellett wrote: > > On Tue, Feb 18, 2020 at 9:46 AM 'Brent Meeker' via Everything List < > [email protected]> wrote: > >> >> It's another way of expressing my objection that while alpha=0.5 produces >> a split into two worlds, alpha= 0.499 produces a split into a thousand >> worlds. >> > > You are harking back to the branch counting idea. I agree that that is a > natural way to think of outcomes having different weights -- by being > associated with different numbers of branches. The problem, of course, is > that this is not compatible with linear evolution according to the > Schrodinger equation. Since the selling point of Everett was supposed to be > "The SWE and nothing else!", anything along these lines is contrary to the > hype. > > > >> But proponents of MWI like Sean Carroll and Bruno, essentially assume >> there are already (infinitely?) many branches which, prior to the >> measurement, are identical at the macroscopic level, but which get >> projected (split) onto orthogonal subspaces by a measurement. >> > > > I know that Bruno talks in these terms, but I may have missed something in > Carroll's book because I don't see that idea coming to the fore there. > > > It's implicit in the diagram you posted from his book. > ??? I didn't post any diagrams from his book. There is the branching tree diagram on page 134, which is essentially just my generation of all possible binary strings. Then there is the 'weight' diagram on page 148, in which he talks about worlds getting "thinner" as branching proceeds. Neither seems to me to indicate a pre-existing plethora of worlds that progressively distinguished by branching. ........ So I don't think Sean is into branch counting. His actual argument is > little more than a decision to put the Born rule in by hand, > > > Right. Bruno however independently hypothesizes a big number of branches > as computational threads in his Universal Dovetailer...however, he > apparently can't get the Born rule except in the 1 and 0 cases. > > since it is clear that linear evolution cannot give results that are > sensitive to the coefficients (amplitudes). It is very difficult to make > sense of his idea of branch 'weights' or 'thicknesses' when these do not > change the actual nature of a branch, and are not visible to the 1p view > from within the branch. > > > From within a branch there is never anything visible except sequences of > results. > Yes. And it is from those experimental results that we infer probabilities. The Born rule is just a way to relate observed frequencies to the theoretical wave function. The frequencies came first. How else did we know what the wave function was? > You can make up God's eye view (I don't call it 3p since 3p is a > possible view) hypotheses in which the sequence is created by some > deterministic process, like a random number generator, which experimenters > will never be able to infer within the life of the universe; and then say > it's not a probability. But I think that is not a sufficiently > instrumentalist view of what "probability" means. I think of probability > in science as like energy, it takes lots of different forms: relative > frequency, propensity, measure,... It's essential characteristic is that > its a way to model uncertainty...whether there is some underlying certainty > or not. > I am not sure what you are getting at here. Probability relates to uncertainty in some form or another. And if the probabilities are to be objective, in the sense that they are independent of what we think, then epistemic probabilities are not really adequate to the task of explaining fundamental physics. That is, at heart, why I think that the world is fundamentally stochastic -- measurement results are determined by some underlying stochastic processes in a single world. Many world ideas simply do not help. 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/CAFxXSLSKFwz8O4omrong6ugsPL-UWUUfOO1s%3DVvHab5DW_5WVg%40mail.gmail.com.
