On Thursday, November 23, 2017 at 5:53:14 PM UTC-6, Bruce wrote: > > On 24/11/2017 10:15 am, Lawrence Crowell wrote: > > On Wednesday, November 22, 2017 at 9:37:48 AM UTC-6, Bruno Marchal wrote: >> >> >> On 20 Nov 2017, at 23:04, Bruce Kellett wrote: >> >> >> You clearly have not grasped the implications of my argument. The idea >> that "MWI replaces all nonsensical weirdness by one fact (many histories)" >> does not work, and is not really an explanation at all -- you are simply >> evading the issue. >> >> >> Without collapse, the apparent correlations are explained by the linear >> evolution, and the linear tensor products only. I have not yet seen one >> proof that some action at a distance are at play in quantum mechanics, >> although I agree that would be the case if the outcome where unique, as >> EPER/BELL show convincingly. >> >> Aspect experience was a shock for many, because they find action at a >> distance astonishing, but are unaware of the many-worlds, or just want to >> dismiss it directly as pure science fiction. But after Aspect, the choice >> is really between deterministic and local QM + many worlds, or one world >> and 3p indeterminacy and non locality. Like Maudlin said, choose your >> poison. >> >> >> Bruno >> >> Bruce >> >> > I am new to this list and have not followed all the arguments here. In > weighing in here I might be making an error of not addressing things > properly. > > Consider quantum entanglements, say the entanglements of two spin 1/2 > particles. In the singlet state |+>|-> + |->|+> we really do not have the > two spin particles. The entanglement state is all that is identifiable. The > degrees of freedom for the two spins are replaced with those of the > entanglement state. It really makes no sense to talk about the individual > spin particles existing. If the observer makes a measurement that results > in a measurement the entanglement state is "violently" lost, the > entanglement phase is transmitted to the needle states of the apparatus, > and the individual spin degrees of freedom replace the entanglement. > > We have some trouble understanding this, for the decoherence of the > entangled state occurs with that state as a "unit;" it is blind to any idea > there is some "geography" associated with the individual spins. There in > fact really is no such thing as the individual spins. The loss of the > entangled state replaces that with the two spin states. Since there is no > "metric" specifying where the spins are before the measurement there is no > sense to ideas of any causal action that ties the two resulting spins. > > This chaffs our idea of physical causality, but this is because we are > thinking in classical terms. There are two ways of thinking about our > problem with understanding whether quantum mechanics is ontic or epistemic. > It could be that we are a bit like dogs with respect to the quantum world. > I have several dogs and one thing that is clear is they do not understand > spatial relationships well; they get leashes and chains all tangled up and > if they get wrapped up around a pole they simply can't figure out how to > get out of it. In this sense we human are simply limited in brain power and > will never be able to understand QM in some way that has a completeness > with respect to causality, reality and nonlocality. There is also a far > more radical possibility. It is that a measurement of a quantum system is > ultimately a set of quantum states that are encoding information about > quantum states. This is the a quantum form of Turing's Universal Turing > Machine that emulates other Turing machines, or a sort of Goedel > self-referential process. If this is the case we may be faced with the > prospect there can't ever be a complete understanding of the ontic and > epistemic nature of quantum mechanics. It is in some sense not knowable by > any axiomatic structure. > > > Hi Lawrence, and welcome to the 'everything' list. I have come here to > avoid the endless politics on the 'avoid' list. > The issue that we have been discussing with EPR pairs is whether many > worlds avoids the implications of Bell's theorem, so that a purely local > understanding of EPR is available in Everettian models. I have argued that > this is not the case -- that non-locality is inherent in the entangled > singlet state, and many worlds does not avoid this non-locality. I think > from what you say above that you might well agree with this position. > > Bruce >
Of course MWI can do nothing of the sort. MWI suffers from much the same problem all quantum interpretations suffer from. With MWI there is a nice idea of the world continuing on as a complete pure state quantum system, but it has the problem that we observers have some restriction on our observational domain. This is because we are thrust into some subset of the Hilbert space of evolution. It really is a sort of collapse, but rather than of an epistemic wave function it is within a map on the ontological domain an observer can access. LC -- 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 https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
