On Thu, Jan 9, 2014 at 11:53 AM, John Clark <johnkcl...@gmail.com> wrote:

> On Wed, Jan 8, 2014 at 1:42 PM, Bruno Marchal <marc...@ulb.ac.be> > > > to me, the Bell's inequality experimental violation is a quite strong >> evidence for MW, that is QM-without collapse. >> > > To me Bell's inequality experimental violation is a quite strong evidence > that reality is not local or not realistic or not either. MWI is not local > so it could be correct, and emotionally it is my favorite interpretation, > but logically I must admit that it is not the only interpretation that > could be correct. > Why do you say "MWI is not local"? Many physicists who advocate the MWI would disagree, like David Deutsch: http://arxiv.org/abs/1109.6223 http://arxiv.org/abs/quant-ph/9906007 This paper by Mark Rubin presents another defense of locality in the MWI: http://arxiv.org/abs/quant-ph/0103079 In it he mentions some of the history of defenses of MWI locality: "In the Everett interpretation the nonlocal notion of reduction of the wavefunction is eliminated, suggesting that questions of the locality of quantum mechanics might indeed be more easily addressed. On the other hand, while wavefunctions do not suffer reduction in the Everett interpretation, nonlocality nevertheless remains present in many accounts of this formulation. In DeWitt’s (1970) often-quoted description, for example, “every quantum transition taking place on every star, in every galaxy, in every remote corner of the universe is splitting our local world on earth into myriads of copies of itself.” Contrary to this viewpoint, others argue (Page, 1982; Tipler, 1986, 2000; Albert and Loewer, 1988; Albert, 1992; Vaidman, 1994, 1998, 1999; Price, 1995; Lockwood, 1996; Deutsch, 1996; Deutsch and Hayden, 2000) that the Everett interpretation can in fact resolve the apparent contradiction between locality and quantum mechanics. In particular, Deutsch and Hayden (2000) apply the Everett interpretation to quantum mechanics in the Heisenberg picture, and show that in EPRB experiments,1 information regarding the correlations between systems is encoded in the Heisenberg-picture operators corresponding to the observables of the systems, and is carried from system to system and from place to place in a local manner. The picture which emerges is not one of measurement-type interactions “splitting the universe” but, rather, producing copies of the observers and observed physical systems which have interacted during the (local) measurement process (Tipler, 1986)." Two more by Rubin: http://arxiv.org/abs/quant-ph/0204024 http://arxiv.org/abs/0909.2673 Conceptually it's not that hard to see how the MWI offers a loophole in Bell's proof--Bell assumed that each spin measurement yielded a single definite outcome, but if you instead imagine that each spin measurement causes the experimenter to split into copies who observe different outcomes and aren't aware of one another, then the universe doesn't have to decide which version of experimenter #1 gets matched up to which version of experimenter #2 until there's been time for signals moving at the speed of light to travel from each experimenter to someone in the middle who can be aware of the results at both locations. If that isn't clear, in post #11 at http://www.physicsforums.com/showthread.php?t=206291 I gave a sort of toy model of how duplicating the experimenters at different locations and matching them up later can allow for each of the matched pairs to observe Bell inequality violations without any need for nonlocality. Jesse > -- > 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 everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > -- 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.