http://mccabism.blogspot.be/2010/10/many-worlds-and-quantum-fungibility.html
<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virus-free. www.avg.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> 2017-06-08 12:57 GMT+02:00 Quentin Anciaux <[email protected]>: > > > 2017-06-08 12:40 GMT+02:00 Bruce Kellett <[email protected]>: > >> On 8/06/2017 7:52 pm, David Nyman wrote: >> >> On 8 Jun 2017 1:05 a.m., "Bruce Kellett" < <[email protected]> >> [email protected]> wrote: >> >> >> The question then, is whether many worlds can provide a fully local >> account of this situation. I claim, with most present day physicists, that >> MWI does not provide any such local account. >> >> >> I suspect I'm being obtuse in some way here but, rereading the quote >> attributed to Bell himself by Wikipedia about superdeterminism, it strikes >> me that MWI seems to describe a species of this sort of thing. IOW when >> Alice and Bob make their measurements, the consequence in terms of branches >> is a spectrum of all the possible outcomes. Indeed one could say that this >> is what has been propagating from one to the other, rather than a >> 'particle'. Let's say then that the various versions of Alice and Bob that >> consequently coexist in MWI terms, however far apart they may have been, >> eventually meet to compare notes. Again, the spectrum of possible outcomes >> implicit in the global MWI perspective travels with them, as it were. >> However, of all the possible pairings of the two, it appears to be >> 'superdetermined' that each observed encounter must be consistent with the >> predictions of QM. And so it would appear that the paired results of their >> joint measurements are somehow inseparable, in Wallace's language, without >> there having been any action at a distance. If this depiction were to make >> any sense, one might then enquire what common cause, or other explanatory >> device, could account for this apparent superdetermination of observed >> outcomes? >> >> >> I don't think that superdeterminism and MWI have very much in common. >> Although Bell did acknowledge that superdeterminism provides a possible >> local loophole to his theorem, Bell always thought that superdeterminism >> was sufficiently implausible to be disregarded as a serious contender as an >> explanation. >> >> I tend to agree with the comment from Zeilinger on the same Wiki page, to >> the effect that such absolute superdeterminism would render the whole >> scientific enterprise otiose. I think that non-locality is a better >> approach -- at least then science can still make sense. >> >> The problem with attempts to find local accounts of the correlations >> between Alice and Bob is that their measurements are taken to be >> independent. If they are independent, then they cannot be correlated -- >> that is in the definition of independence. Superdeterminism circumvents >> this, simply by denying that Alice and Bob can freely choose their >> measurements, and are consequently not independent. >> >> As I understand the better attempts to give an account in MWI, it is >> accepted that Alice and Bob are independent, so their results are >> uncorrelated *when they are made*, but the necessary correlation is built >> later when they meet to compare results. I find this unconvincing, and no >> satisfactory account of any mechanism whereby this could be achieved has >> been given. Accounts along this line seem to depend on multiple worlds >> containing all possible results that somehow, miraculously, pair up, >> without any outside intervention, in such a way to give the necessary >> correlations. This is rendered less plausible if one considers timelike >> separations, where Bob, say, is always in Alice's forward light cone, so >> any splitting of either observer is communicated to the other by normal >> decoherence, long before the other measurement is made, and before they >> meet up to compare lab books. >> >> > If I remember David Deutsch explained that the worlds were not "splitting" > but differentiating, and thus are all preexisting... so even if their > measures are independent, this gives only a self localisation... and so > nothing non-local happens ? > > Quentin > > > > > >> 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 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. >> > > > > -- > All those moments will be lost in time, like tears in rain. 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