> On 23 Aug 2018, at 19:49, [email protected] wrote: > > > > On Thursday, August 23, 2018 at 3:16:24 PM UTC, Bruno Marchal wrote: > >> On 23 Aug 2018, at 02:05, Bruce Kellett <[email protected] >> <javascript:>> wrote: >> >> From: Bruno Marchal <[email protected] <javascript:> >>>> On 22 Aug 2018, at 01:54, Bruce Kellett <[email protected] >>>> <javascript:>> wrote: >>>> >>>> From: Bruno Marchal <[email protected] <javascript:>> >>>> >>>>> The other sort of infinity, the one which I think you disagree with, is >>>>> typical for the superposition of tensor products, like the singlet state >>>>> ud - du. Before measurement Alice has the same probability of finding u, >>>>> or d for any measurement she can do in any direction. Both Alice and Bob >>>>> are maximally ignorant of their possible measurement results. The MW on >>>>> this, or a MW way to interpret this, to keep the rotational symmetry, is >>>>> that we have an infinity of couples Alice+Bob, with each couple being >>>>> correlated. If not, some implicit assumption is made on u and d, like it >>>>> is a preferred base. >>>> >>>> But the problems with any such suggestion are obvious. Firstly, Alice does >>>> not choose her measurement angle in that way, so there is no >>>> super-superposition created. Secondly, this construction does not restore >>>> the rotational symmetry in any case. You might have an infinite number of >>>> Alices, measuring the singlet at all possible angles, but that >>>> multi-multiverse is not rotationally symmetric either! All it needs is for >>>> Alice number 7,234,826 to poke her tongue out and the rotational symmetry >>>> is lost! Of course, you could add yet more multiverses to cover every >>>> possible deviation of Alice from the stationary state. But the process >>>> rapidly becomes ridiculous. >>>> >>>> So this Rube Goldberg construction of additional multiverses of >>>> superpositions does not actually restore stable >>>> rotational symmetry. So why propose such a construction? William of Ockham >>>> will rise out of his grave to haunt you for such pointless extravagance of >>>> entities! >>> >>> Alice destroys the rotational symmetry in all its universe. Not of the >>> whole wave, where Alice does not exist as a determinate subsystem. >> >> I can't really parse this. The point is that when Alice interacts with the >> singlet with her magnet she destroys the rotational symmetry of the state. >> This symmetry is not restored by considering and large system, or the whole >> wave. If anything, enlarging the context in this way simply lessens any >> symmetry that might remain. >> >> I think what you have in mind is a situation such as arises if you shine a >> light through a small aperture. The photon emerges as a spherical wave, with >> the rotational symmetry of such a (hemi-)spherical wave. If there is a >> hemispherical screen downstream, the photon will interact with the screen at >> some single point. If you consider only one branch of the SWE evolution, >> this interaction point breaks the rotational symmetry. But if you consider >> all branches of the wave function together, there is a branch for every >> single point at which the photon can hit the screen, so that the symmetry is >> preserved in the wave function as a whole -- over the ensemble of all >> branches. But that is a situation in which the environment with which the >> photon interacts is itself symmetrical. If the screen, rather than being a >> smooth equidistant hemisphere, is just the rough walls of the laboratory, >> there is no symmetry in the points at which the photon can hit the walls, >> and the rotational symmetry is lost, even in the wave function as a whole, >> even by considering the superposition of all possible branches. >> >> The take away message from this is that the symmetry of the original system >> can be lost by interaction with a non-symmetrical environment. The boundary >> conditions of the total system may not have the symmetries of the original >> state. So loss of symmetry is ubiquitous in the universe, even for >> Everettian no-collapse quantum mechanics. If you introduce a non-symmetrical >> interaction into the system, the symmetry is lost. That is all that is >> happening with the measurement of the spin projection of the singlet state >> by Alice. Your idiosyncratic interpretation of the tensor product, and your >> insistence the the symmetry be preserved regardless of the non-symmetrical >> environment, are just misguided. There is no need to try to preserve >> symmetry given non-symmetrical boundary conditions. >> >> Since the symmetry is broken, the singlet state no longer exists in its >> original form, and the state that Bob measured is affected by the >> measurement Alice makes. There is no more to it than this. If Alice and Bob >> are space-like separated, there are some interpretational issues with this >> instantaneous influence at a distance. > > Nice to hear that. It was basically my point.We have never disagreed except > on some definition. I use “symmetry” in a larger sense, and I take > superposition at face value, independently of the base, making the > superposition of tensor products into “many superposition”, which indicate > the relative state locally accessible by the observers. > > > >> But that just means that quantum mechanics is not fully integrated with a >> total quantum theory of space-time. > > Yes. > > >> No need to get agitated by this -- ride with it until we have a more >> complete theory. In the meantime, this is what is meant by non-locality. > > It means violation of Bell’s inequality. I get agitated only by those > implying the existence of instantaneous physical action at a distance, that’s > all. > > Bruno > > But keep in mind that if the wf is epistemic only, it can change > instantaneously with no PHYSICAL action at a distance. This is what Bruce's > horse race example shows, and FWIW, my present assessment of the situation; > wf epistemic only. AG
I can only appreciate this, as it makes QM-without collapse even closer to the physics that we extract from machine self-reference. But some philosophers of QM would disagree. But I agree, we get closer to the universal machine’s many dreams interpretation of arithmetic/combinator/… 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 [email protected] <javascript:>. >> To post to this group, send email to [email protected] >> <javascript:>. >> Visit this group at https://groups.google.com/group/everything-list >> <https://groups.google.com/group/everything-list>. >> For more options, visit https://groups.google.com/d/optout >> <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 [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <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 [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.
