> On 18 Apr 2018, at 15:11, Bruce Kellett <[email protected]> wrote: > > From: Bruno Marchal <[email protected] <mailto:[email protected]>> >>> On 17 Apr 2018, at 00:58, Bruce Kellett < >>> <mailto:[email protected]>[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> From: Brent Meeker <[email protected] <mailto:[email protected]>> >>>> On 4/15/2018 8:33 PM, Bruce Kellett wrote: >>>>>> We have discussed this, and I have never agree with this. The singlet >>>>>> state (in classical non GR QM) describes at all times an infinity of >>>>>> combinations of experimental result. >>>>> >>>>> This is false. Even in Everettian QM there are only two possible outcomes >>>>> for each spin measurement: this leads to two distinct worlds for each >>>>> particle of the pair. Hence only 4 possible parallel universes. Where do >>>>> you get the idea that there are infinitely many parallel universes? This >>>>> is not part of Everettian QM, or any other model of QM. But even if you >>>>> can manufacture an infinity of universes, you still have not shown how >>>>> this removes the non-locality inherent in the quantum formalism. >>>> >>>> Bruno's ontology is all possible computations, so he's already assumed >>>> (countably) infinite worlds. When there are only four or two outcomes of >>>> an experiment it just means his worlds are divided into four or two >>>> equivalent subsets. >>> >>> That might very well be the case. But then that has absolutely nothing to >>> do with Everett or quantum mechanics. Bruno's long-held claim is that >>> Everett's many worlds obviate the need for non-locality. >>> But he has never been able to produce a coherent argument to this effect. >>> It is always this bullshit about an infinite number of worlds -- as if that >>> made any difference at all. >> >> You are the one making the extra-ordinary claims. I don’t say much more than >> maudlin on this issue in his book on Nonon-Locality: it makes no sense in >> the many-world. > > You seriously misrepresent Maudlin. To make this as clear as possible, I have > taken the third edition (2011) of Maudlin's book "Quantum Non-Locality and > Relativity" and typed out all the sections under the heading of "many-worlds > theory" from the index. > > > "The many-worlds theory is incoherent for reasons which have been often > pointed out: since there are no frequencies in the theory there is nothing > for the numerical predictions of quantum theory to mean." (Page 4, Note 1.) > > "So we must either abandon locality or abandon the predictions of quantum > theory for events at space-like separation. I have sketched how some versions > of the many-worlds interpretation of quantum theory appear to do the latter, > and considered in some detail how locality might be abandoned in a > technically precise way." (Page 224, Chapter 10) > > "Other, more popular approaches, though, are taken quite seriously even > though they offer no clear account of local beables at all. Most obviously, > many-worlds theorists typically do not postulate any local ontology in the > foundations of the theory: all there is is the wave-function. A lot of > attention is paid to "observables" and "decoherence", but it is not at all > clear how to generate a local ontology if all one has to work with is the > wave-function. ... But since the wave-function is not itself a local beable, > nothing about its dynamics can yield a local ontology." (Page 250.) > > > Then the most extensive discussion of many-worlds appears in Chapter 10, > which was new for the third edition of his book. > > "Standard quantum theory asserts that measurements always have outcomes, and > furthermore have unique (albeit unpredictable) outcomes. It is exactly > because such experiments always have outcomes that we can ask after the > predictions of the theory for the correlations between the outcomes: if I > measure the polarization of a photon in some direction on one wing of an > experiment and the polarization of an entangled photon on the other wing, how > like is it that the polarization outcomes will be the same (both passed or > both absorbed) or different (one passed and the other absorbed)? > > "If a many-worlds interpretation insists that there are no local beables, > then this is the situation. It cannot possibly reproduce the predictions of > standard quantum theory about the outcome of experiments, and so is not > relevant to our discussion of theories that agree with these predictions. But > the many-worlds interpretation is never presented in this way. It is rather > presented as if instead of no local beables, there is a (largely invisible) > profusion of them. That is, instead of nothing happening on either wing of > the experiment, the standard story is that everything happens on both wings: > on both wings, there is "a world" in which the photon passes its polarizer > and "a world" in which it is absorbed, no matter how the polarizers were > oriented. > > "... If the wave-function never collapses, then the matter density evolves > into a rather indistinct blob, consisting in all the "possible" outcomes of > the experiment (passed and absorbed, for example, with all these results > being recorded in macroscopic ways) literally superposed on one another in > the same space-time region. One then tries to argue that different components > of the blob are causally disconnected from one another, and so would be > mutually transparent: many outcomes co-existing but unaware of each other. > One will typically appeal to decoherence of the wave-function and a > functional analysis of how to separate the blob into distinct worlds to make > out this conclusion. > > "But two facts must be kept in mind. First, as we have seen, the matter > density ontology is not implied by the existence of the wave-function per se. > ... If a many-worldser wants there to be a local matter density in > space-time, then that has to be postulated in addition to the wave-function. > Second, if we produce an account like this, then there still has to be > discussion of what it means to say that the outcomes on the two wings of the > experiment are correlated to some degree. If whenever a polarization > experiment is done, with any orientation of the polarizers, both outcomes are > always produced, then it is not obvious what it might mean to say that these > outcomes are correlated. If no sense can be made, then again the theory does > not reproduce the predictions of standard quantum theory, which predicts > definite correlations for outcomes at space-like separation. And if some > sense can be made of the existence of correlations, we have to understand > how. In particular, if appeal is made to the wave-function to explicate the > sense in which, say, the "passed" outcome on the right is paired with the > "absorbed" outcome on the left to form a single "world", then we have to > recognize that this is not a *local* account of the correlations since the > wave-function is not a local object." (Pages 250-252.) > > > So Maudlin does not support your notion that many-worlds removes the need for > non-locality. In fact, Maudlin is clearly claiming the exact opposite. He > clearly does not like the many-worlds approach, calling it incoherent. But > even if sense can be made of such a theory, there is still no possibility of > a *local* account of the correlations in polarization measurements of the > entangled singlet state. >
I have only the first edition. His “critics” on Everett comes from his missing of the first-person indeterminacy (he choose “materialism” against mechanism!): he does not look at each diaries of the observer of the Schroedinger cat. So, indeed, he needs the “many-mind” theory to give sense to Everett, where, at least im my edition he made clear that the “non locality” does not apply. I quote ”Since there are no *relevant* correlation between space-like separated event [in the many-mind theory] there is no problem of non-locality. As digital mechanism is of the “many-mind” type at the phenomenological outset, all problems that some Everettian can have is due to the Aristotelian assumption, which is inconsistent with computationalism in cognitive science from the start (as I showed). Maudlin’s conclusion: “Or finally, one can both avoid collapses and retain locality by embracing the Many-Minds ontology, exacting a rather high price from common sense”. For this Plato did warn us, and indeed computationalism leads to that same form of price. Note that with comp the “many-minds” is stilll only in the phenomenology. The ontology is given by any Turing universal machinery (combinators, numbers, …). Of course “counter-intuitive” is not a refutation. 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 post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- 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 post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
