> On 9 Feb 2020, at 03:53, Bruce Kellett <[email protected]> wrote: > > On Sun, Feb 9, 2020 at 11:08 AM 'Brent Meeker' via Everything List > <[email protected] <mailto:[email protected]>> > wrote: > On 2/8/2020 3:21 PM, Bruce Kellett wrote: >> On Sun, Feb 9, 2020 at 9:48 AM 'Brent Meeker' via Everything List >> <[email protected] <mailto:[email protected]>> >> wrote: >> On 2/8/2020 2:12 PM, Bruce Kellett wrote: >>> On Sun, Feb 9, 2020 at 6:38 AM 'Brent Meeker' via Everything List >>> <[email protected] >>> <mailto:[email protected]>> wrote: >>> On 2/7/2020 11:00 PM, Bruce Kellett wrote: >>>> >>>> It is an indexical theory. The problem is that in MWI there will always be >>>> observers who see the sequences that are improbable according to the Born >>>> rule. This is not the case in the single-world theory. There is no random >>>> sampling from all possibilities in the single-world theory. >>> >>> ?? There's something deterministic in single-world QM? You seem to have >>> taken the position that MWI is not just an interpretation, but a different >>> theory. >>> >>> That is a possibility. I do think that MWI has difficulty with probability, >>> and with accounting for the results of normal observation. >>> >>> That some very improbable results cannot occur in SW QM. I think you are >>> mistaken. >>> >>> I don't know where you got the idea that I might think this. >>> >>> >>> No matter how low a probability the Born rule assigns to a result, that >>> result could occur on the first trial. >>> >>> >>> Yes, but in SW the probability of that is very low: in MWI the probability >>> for that is unity. >> >> You keep saying that; but you're misreferencing what "that" is. The >> probability of any given observer seeing the low probability event is just >> that low probability. "That" isn't unity. >> >> It is unity if the hypothesis is that every outcomes occurs for every trial. >> It is not a matter of any arbitrary observer -- it is that there is an >> observer who definitely sees that result. > > Not "that result" = "every outcome occurs". It's that given an outcome, > there is an observer who sees it. > > Don't twist things around. > And given an outcome there is only a probability P(outcome_i) that you see > it. > > Since it is the existence of such a probability, P(outcome_i) that is in > question, your comment begs the question. >>> However, we seem to be in danger of going round in circles on this, so it >>> might be time to try a new tack. >>> >>> As I said, I have difficulty understanding how the concept of probability >>> can make sense when all results occur in every trial. If you have N >>> independent repetitions of an interaction or experiment that has n possible >>> outcomes, the result, if every outcome occurs every time, is a set of n^N >>> sequences of results. The question is "How does probability fit into such a >>> picture?" >>> >>> In any branch, when the experiment is performed, that branch is deleted and >>> replaced by n new branches, one for each possible outcome of the >>> experiment. This is clearly independent of any model for the probability >>> associated with each outcome. In the literature, people speak about >>> "weights of branches". But what does this mean? -- that there are more of >>> some types of branch?, or that some branches are more 'important' that >>> others? It does not seem clear to me that one can assign any operational >>> meaning to such a concept of "branch weights". >> >> That's why I said that to make it work one needs to postulate that there are >> many more branches than possible results, so that results can be "weighted" >> by having more representation in the ensemble of branches. Then >> probabilities are then proportional to branch count. That gives a definite >> physical meaning to probabilities in MWI. It's a physical model that >> provides "weights". BUT it's a cheat as far as saying MWI implies or >> derives the Born rule. The rule has been slipped in by hand. >> >> >> It certainly is a cheat. And it is a different model. It is not just an >> interpretation of QM -- it is a different model, incompatible with Everett. >> Everett is quite clear: he postulates one branch -- one 'relative state' -- >> for each component of a quantum superposition. This is incompatible with >> multiple branches for each such component. >>> In this situation, the set of n^N sequences of results for this series of >>> trials is independent of any a priori assignment of probabilities to >>> individual outcomes >> >> I don't understand what you mean by that. Are you limiting this to a >> binomial experiment, with H's and T's? And are you assuming that at every >> trial each outcome occurs exactly once in the multiverse? >> >> Did you not see that I speak of 'n' possible outcomes for every experiment? >> It is by no means limited to binary outcomes. And yes, I am following >> Everett and assuming that each trial outcomes occurs exactly once in the >> multiverse. If you go beyond this, then you are talking about a different, >> non-Everettian model. I think that most of your comments are based on your >> assumption that an uncountable infinity of branches is associated with each >> possible outcome (to accommodate all real weights). That is why we seem to >> be constantly talking at cross purposes -- you have not made you assumptions >> clear. > > I was trying to address both at once. But, yes I think Bruno's idea of a > MWI, as well as other people's, requires a very large number of branches; but > not a realized infinity, because that makes it impossible to assign a measure. > > So they are not talking about Everettian QM. > >>> : whatever the probabilities or weights, the set of sequences of results is >>> the same. In other words, for the experimentalist, the data he has to work >>> with is the same for any presumed underlying probabilistic model. >> >> Are you saying the data he obtains has no probabilistic relation to the >> ensemble of possible outcomes? You seem to be putting the Bayesian >> inference backwards. The data he has is in some sense independent of any >> model. But he's evaluating his model given the data. That fact that this >> doesn't change the data is the same in any interpretation. >> >> The point is that the data are independent of any probabilistic model -- >> given a strict Everettian interpretation of the relative states and >> branching. Thus the data cannot be used to evaluate any such model. > > What are you calling "the data"? All the branch results, one per result? All > the branch results with weighting by multiple branches for the same result? > The observations of some particular observer? It seems your conclusion only > applies to the first. > > The first: the set of branches generated by assigning one new branch to each > result in each trial of the experiment. So of course my observations apply > only to this case. This is the model proposed by Everett, and I was exploring > whether the concept of probability made sense in this simple model. My > conclusion is that it does not. Consequently, Everett fails as a scientific > theory. >>> Consequently, experimental data cannot be used to infer any probabalistic >>> model. In particular, experimental data cannot be used to test any prior >>> theory one might have about the probabilities of particular outcomes from >>> individual experiments. >> >> Sure it can. The data can imply a low posterior probability for a given >> model. The experimenter has gotten one particular result. It is irrelevant >> that other results occurred to other copies of the experimenter. >> >> That is only if probabilities and branch weights have an objective meaning. >> My contention is that they do not in a strictly Everettian model. >>> The conclusion would be that such a model is unable to account for standard >>> scientific practice, in which we definitely use experimental data to test >>> our theories, and as the basis for developing new and improved theories. >>> This is impossible on the above understanding of MWI. >>> >>> So this understanding of MWI is presumably flawed. But how? I do not see >>> any other realistic way to implement the idea that all possible results >>> occur in any trial. Talking about branch weights and probabilities seems to >>> be entirely irrelevant because these things have no operational >>> significance in such a model. >> >> They are parameters to the hypothetical model to be evaluated by calculating >> their posterior probability given the observed results. All possible >> results don't occur in any branch. They occur in other branched to other >> observers and that influences the result no more than supposing the results >> are drawn from some ensemble. >> >> Again, you seem to be implicitly relying on the assumption that branch >> weights actually exist and have objective meaning. In other words, your >> comments presume your idea of implementing probabilities as branch counts. >> This is a different model. It is not implicit in the Schrodinger equation, >> and it is certainly not what Everett envisaged. > > But it is implicit, or even explicit in Bruno's model. It's also consistent > with Barbour's model. > > It can be consistent with as many models as you like. It is simply not > Everettian QM. It is some ad hoc concoction that totally undermines the point > that was the basic attraction to Everett in the first place. People like > Carroll and Wallace laud Everett because they see it as quantum mechanics in > the raw -- the Schrodinger equation without extraneous additional > assumptions. You seem bent on adding all these extraneous assumption, most of > which are not even consistent with the Schrodinger equation, and still claim > that you are talking about the same model. > > > My criticism of it is that by requiring this multiple branching, so you need > two branches if Pup=1/2, Pdwn=1/2 but you need a thousand branches if > Pup=501/1000, Pdwn=499/1000, you have now resorted to something outside > Schroedinger's equation and you have to put in Born's rule by hand. > > I agree. Any such addition is ad hoc and ugly. And it probably doesn't even > work if you examine it closely. > > But in Bruno's theory he begins by assuming a potential infinity of > computational threads, which then branch from identical bundles. Whether he > can get QM and Born rule remains to be seen. > > Of course he can't. He can't get any real physics from his models. And it is > very doubtful if he has actually ever proved anything of value.
My work is just a remind that we have not solve the mind-body problem, and that the easiest theory of mind (computer science) transforms the problem into justifying Everett QM from the self-reference applied to the sigma_1 sentences (and the sigma_1^A with A arbitrary oracles, for the view which contains the “& p” (Theaetetus idea). It is of value for those who search the truth, and it has some application, like encouraging people to come back to reason and modesty in metaphysics/theology, which I think would help the humans a lot. 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 [email protected] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/CAFxXSLRDTiBT6x%3DeLFw1mwLCV0DmSMuW%2BGsFgGQz1hTyTQu%3DwQ%40mail.gmail.com > > <https://groups.google.com/d/msgid/everything-list/CAFxXSLRDTiBT6x%3DeLFw1mwLCV0DmSMuW%2BGsFgGQz1hTyTQu%3DwQ%40mail.gmail.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/F5D3B1E0-E4C2-4FB5-8681-23CBC97E18D7%40ulb.ac.be.
