On 5 June 2017 at 17:38, Bruno Marchal <marc...@ulb.ac.be> wrote: > > On 05 Jun 2017, at 15:48, David Nyman wrote: > > On 5 June 2017 at 14:22, Bruno Marchal <marc...@ulb.ac.be> wrote: > >> >> On 04 Jun 2017, at 14:48, David Nyman wrote: >> >> >> >> On 4 Jun 2017 1:05 p.m., "Bruno Marchal" <marc...@ulb.ac.be> wrote: >> >> >> On 02 Jun 2017, at 03:01, Bruce Kellett wrote: >> >> On 1/06/2017 10:19 pm, Bruno Marchal wrote: >>> >>>> On 01 Jun 2017, at 02:26, Bruce Kellett wrote: >>>> On 1/06/2017 4:43 am, Bruno Marchal wrote: >>>> >>>>> On 31 May 2017, at 04:01, Bruce Kellett wrote: >>>>>> >>>>>>> On 30/05/2017 9:35 pm, Bruno Marchal wrote: >>>>>>> >>>>>>>> On 30 May 2017, at 11:28, Telmo Menezes wrote: >>>>>>>> >>>>>>>> snip >>>>>>>> >>>>>>>> >> >>> Your claim appears to be that Bell's theorem is not valid in MWI. >>> >> >> Bell's theorem is valid. His inequality does not even assume QM, but just >> locality. It is violate when we do the experience, like Aspect, and this >> shows non-locality in our branch, but when looking at the big picture, we >> see that this non-locality has a local origin. It would need an action at a >> distance to destroy the alternante branches alwailable to Bob, but without >> collapse, non-locality is a local, branch-owned, phenomenon. I take Bells >> theorem + Aspect as a quasi definite proof that if there is one universe, >> then there are many universes. >> >> >> >> >> >> >> This is nonsense. Bell's theorem is a theorem of quantum mechanics, and >>> it is therefore valid in all interpretations of that theory. >>> >> >> Yes, in all interpretation of quantum mechanics, the relevant branches >> violate the inequality, but they do that without involving an action at a >> distance when we look at the entire wave. It is phenomenological. >> >> >> Suppose one were to enquire what makes those branches "relevant". One >> answer is that other pairings would be in conflict both with the >> predictions of QM and with observation, but that is circular. What then? >> Perhaps one might speculate that other pairings would somehow be >> fundamentally inconsistent with any physics that would permit its own >> coherent (or for that matter decoherent) observation. >> >> >> The branches are just the superposed states, and with singlet or with >> simple qubit, the other branches are just the other term of the >> superposition which describes ourselves. To get rid of such superposition, >> we need to get rid of quantum mechanics, *and* of mechanism. >> > > I'm not sure I made myself clear. What I meant by "other pairings" was > the ones we never expect to witness - e.g. the ones that presumably might > not violate Bell's inequalities. > > > OK. You mean this in the context of assuming quantum mechanics. If we say > that we don't see them because QM disallows them, or because things just > aren't that way, that is circular. >
> I am not sure I understand this. If we assume QM, it is standard. Unlike > Mechanism, somehow QM solves the measure problem. > So is the idea then that all possible 'measurements that Alice and Bob could possibly make are already 'paired', in terms of superpositions, in the MWI view? And then the question of which branch either of them is situated in, and consequently which pairing they will be associated with, is determined by the measurement subsequently performed (apparently individually) by each of them? ISTM that saying it's "just the other term of the superposition which > describes ourselves" is equally circular. What about superpositions that > don't "describe ourselves"? > > > With Copenhagen, all superposition don't describe the observers, and we > get standard QM with collapse. Then with Everett, we have an explanation > why, even without collapse, the average observer, when doing a measurement, > entangled itself and correlate his brain with the outcome, and the proba > are justify by the FPI. may be I still miss something? > > (here, by superposition which describes ourself, I meant only something > like (me -- cat alive + me -- cat dead). > > So my question was about whether there is a non-circular answer to the > question of why we don't expect observations by Alice and Bob to lead to > the correlation of such 'malformed' pairs. Perhaps because such correlation > might entail a 'physics' that precluded the act of observation itself. > > > I am not sure what you are asking. If we suppose QM, the reason why the > "malformed pair" are not seen is that QM disallow them, or makes them very > rare. > If we don't suppose QM, like when assuming mechanism, we have to derive > QM, or the correct theory in case QM is incorrect, to answer this. > > But the context here was the question "does the abandon of the collapse > prevents influence at a distance". Bruce claims it does not, and me (but > here there are many others, even on this list) claims it does, or at the > least, that we cannot use the Bell violation to claim MWI is not local. In > that thread we fully assume QM (without collapse). > I think I follow. Wallace, in The Emergent Multiverse which I am slowly reading, claims that MWI implies non-locality but not action at a distance. The non-local information encoding entanglement, in this view, is part of the overall state discoverable upon 'measurement' but is never propagated at more than light speed. > > > > >> >> This might ultimately be related to the speculation that the appearance >> of spacetime itself may emerge as a consequence of entanglement. >> >> >> Possibly, although you might elaborate a little bit. >> > > Well, my (admittedly vague) speculation was that the 'entanglements' we > never expect to observe might be 'malformed' in some way that precluded the > emergence of a spacetime within which such observation could occur. > > > It is a bit vague indeed. I think our allusion between space and > entanglement is related to some approach trying to derive the > space-time-gravity structure of the physical universe from the quantum > entanglement. I am far away to be familiar with this. It would be nice, > notably to simplify the future (very future) extraction of General > Relativity from the "material hypostases". > > A summary is given in this paper: > > http://www.nature.com/news/the-quantum-source-of-space-time-1.18797 > Thanks. David > > Bruno > > > > > >> I certainly like the idea that space emerge from entanglement. There are >> some relation between "entanglement" in knot theory, and the quantum >> entanglement, notably suggested by some work by Louis Kauffman, but that >> too needs some elaboration. I expect that the emergence of space in >> Mechanism will comes from a more primitive notion of entanglement, but for >> this we need to derive the tensor product, and that is not easy at all, and >> requires solution of open problems related to the semantics of the >> "material hypostases". >> >> Bruno >> >> >> David >> >> >> >> >> >> >> >> If it is not valid in MWI, then Many-Worlds is a different theory, and >>> not just an interpretation of standard QM. >>> >> >> It is valid in the MWI, but interpreted differently than in a >> mono-universe interpretation which requires non local action at a distance >> to get the same non-locality. >> (with or without hidden variables). >> >> >> >> >> >>> >>> >>> As on the previous occasion we discussed this, you were unable to >>>>> demonstrate where the notion of 'collapse' is used in Bell's theorem - all >>>>> Bell requires is that measurements give results, and that is what the >>>>> whole >>>>> of physics is based on: in MWI as well as in any other interpretation. >>>>> >>>> >>>> We did eventually agree. May be reread those post. Bell's supposed that >>>> when the two measurement are done, Alice and Bob get a precise answer, >>>> which makes no sense without-collapse. >>>> >>> >>> That is what making a measurement means. It is what happens in all >>> interpretations. It makes no sense to deny counterfactual definiteness -- >>> that is not QM. >>> >> >> It is QM without collapse, and using the simple mechanist FPI. >> >> >> >> >> >>> Alice and Bob get *all* (always correlated) answers, but when >>>> light-separated, it make no sense to compare them. They can only make >>>> comparison with the person accessible in their light cone, where the >>>> contagious superposition spread out. >>>> >>> >>> I presume you mean "space-like separated". Alice and Bob do their >>> measurements; >>> >> >> The infinities of Alices and Bobs do their measurements. >> >> >> >> >> they get their results and write them in their lab books. They meet years >>> later and compare lab books. Are you trying to suggest that they do not >>> have definite answers in their lab books before then? >>> >> >> The infinities of Alices and Bobs get their infinities of definite >> results. >> >> >> >> >> In MWI (with two-outcome experiments), there is a copy of Alice that >>> writes '+' in her lab book, and a copy who writes '-' (for a given >>> orientation theta). Similarly for Bob. There are, therefore, only four >>> possibilities when they meet: '++', '+-', '--', and '-+'. The non-locality >>> is necessary to set the probabilities for each of these four possible >>> combinations of results. If you want to eliminate the non-locality, you >>> have to give a non-magical way of establishing the necessary probabilities. >>> You have never been able to do this. >>> >> >> QM does that, and without collapse, I don't see how any influence leaking >> at the speed of light need to be introduced. >> >> >> >> >>> Remember that in a sequence of such experiments, the probabilities for >>> '+' and '-' are 50/50 for both Alice and Bob. >>> >> >> OK. >> >> >> >> The joint probabilities, or correlations, depend on the relative >>> orientations of their polarizers. >>> >> >> Right. >> >> >> It is information about this relative orientation that must be conveyed >>> non-locally for the correlations to come out correctly when they meet. >>> >> >> Why? That would be the case if you think that it is the same Bob and >> Alice all along the experiences, but that cannot be the case. >> >> >> >> It is not sufficient for them simply to exchange this information later, >>> because their results at particular orientations are already fixed when >>> they meet. >>> >> >> I don't see this. If the angle is some theta different from 0° or 90° >> they will both split/differentiate, and whoever they will meet later will >> be the correspond partner with the correct correlation, obtained by the >> decoherence local to their respective branch. In this case, it is clear >> that it does not make sense to attribute to "Alice and Bob" the same >> identity than the initial one. >> >> 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 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. >>> >> >> http://iridia.ulb.ac.be/~marchal/ >> >> >> >> >> -- >> 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. >> >> >> >> -- >> 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. >> >> >> http://iridia.ulb.ac.be/~marchal/ >> >> >> >> >> -- >> 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. >> > > > -- > 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. > > > http://iridia.ulb.ac.be/~marchal/ > > > > -- > 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. > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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