On 11/27/2017 9:10 AM, Lawrence Crowell wrote:
On Sunday, November 26, 2017 at 8:29:22 AM UTC-6, Bruno Marchal wrote: On 24 Nov 2017, at 15:59, Lawrence Crowell wrote: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. BrunoBruceI 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.I don't see this. the MW theory (that is the WWE without the collapse axiom) explains the violation of inequality in a way which avoids any action at a distance, but when we assume one universe, like Einstein explains very clearly already in 1927, you get a notion of simultaneousness incompatible with special relativity and very minimal form of realism. For me, as a logician, I consider that SWE and SWE+collapse are different theories. The first is local, deterministic and admits a local physical realism, the second is not intelligible at all, as the notion of observer is unclear and dualistic. BrunoI suppose I don't know what WWE means. MWI is not a bad idea, but I frankly question whether it along with all other interpretations are properly scientific theories. I see no particular way that any quantum interpretation can be tested. The idea is nice in that it gives an idea of a total universe as unitary, but where the phenomenology has us moving along one particular path in a decoherence event. However, if we are to have a splitting off of the world we might think of there being a many block world perspective, where a decoherence of a quantum event splits off quantum amplitudes on all possible spatial surfaces that contain this event. This has been referred to in the past as the gemische; all possible spacelike manifolds that embed a measurement event. However, we have some ambiguity with respect to probability amplitudes associated with each path in this splitting.
And it's even worse than that. There's not just splitting an well defined "events". "Events" like nuclear decay and the death of Schrodinger's cat happen on a continuum.
Brent -- 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.
