On Fri, Nov 22, 2024 at 12:12 AM smitra <[email protected]> wrote: > On 18-11-2024 07:02, Bruce Kellett wrote: > > On Mon, Nov 18, 2024 at 4:17 PM PGC <[email protected]> > > wrote: > > > >> Your response presents strong points but contains some redundancies > >> and overlapping arguments. Here's a revised version with greater > >> focus, while maintaining the original’s precision and accuracy: > >> ------------------------- > >> > >> Bruce, let’s directly address the epistemic interpretation of the > >> wavefunction. While this view neatly avoids ontological commitments > >> and sidesteps issues like FTL action, it doesn’t fully account for > >> experimentally observed phenomena such as violations of Bell’s > >> inequalities. > > > > The violation of Bell inequalities implies non-locality, and the > > epistemic interpretation of the wave function is perfectly compatible > > with non-locality. > > > > The violation of Bell's inequalities does not imply non-locality. In > fact, the violation of Bell's inequality is a prediction of QM which > when describing the dynamics with a physical Hamiltonian, is a > manifestly local theory. It's only in certain interpretations that there > can be non-local aspects, but then these interpretations make > assumptions that require local dynamics to be violated.
And what might these assumptions be? But there is > nothing whatsoever non-local about the dynamics of how the wavefunction > evolves over time. Not for an isolated non-interacting system. But the Bell inequalities refer to entangled particles, which do not evolve independently. In that case, non-local effects are required to explain the observed correlations. This means that in any interpretation where you stick > to only the wavefunction as describing physical reality, that nothing > non-local can occur. > > >> These correlations are not just statistical artifacts of knowledge > >> updates; they point to an underlying structure that resists > >> dismissal as mere epistemic bookkeeping. The wavefunction’s role > >> in consistently modeling entanglement and its statistical > >> implications suggests questioning the existence of a deeper reality, > >> challenging the sufficiency of an epistemic-only framework. > > > > Unfortunately, Everettian QM, or MWI, cannot even account for the > > correlations, much less the violations of the Bell inequalities. I > > have made this argument before, but failed to make any impact. Let me > > try again. > > > > The essence of Everett, as I see it, is that every possible outcome is > > realized on every experiment, albeit on separate branches, or in > > disjoint worlds. Given this interpretation, when Alice and Bob each > > separately measure their particles, say spin one-half particles, they > > split at random on to two branches, one getting spin-up and the other > > branch seeing spin-down. This happens for both Alice and Bob, > > independent of their particular polarization orientations. If this > > were not so, the correlations could be used to send messages at > > spacelike separations, i.e, FTL. > > It doesn't happen independently, because when Alice makes her > measurement, her state becomes entangled with entangled spin pair. So, > you now have a macroscopic quantum state where Alice plus her > measurement apparatus are entangled with the entangled spin par. According to Everett, Alice splits into two branches, one for each possible result of the spin measurement. That is how the entanglement is manifested. There is nothing particularly classical about this situation. And when Bob makes his measurement, he gets entangled with the spin pair > and > as a result with Alice's sector. When Bob is spacelike separated from Alice and her measurement, he also splits into two independent branches. So, in the end it's because you choose > not to describe Alice and Bob quantum mechanically and treat them as > classical objects That is not the case. Everettian quantum mechanics says that they both split on to two branches, and there is no clear way in the formalism to see how the branches for the two individuals are related. In any model, in which both outcomes are necessarily realized for every measurement, there is no way to relate the outcomes. that you end up missing an essential element and that > leads to a paradox. > Nothing has been missed in my analysis. As usual, you are unable to actually spell out how the correlations are preserved in the many-worlds scenario. Bruce Another example of non-locality arising as an artifact of describing > part of a system classically, is the Aharanmov-Bohm effect: > > https://arxiv.org/abs/1906.03440 > > Here too the fact that within the classical realm, you cannot describe > entanglement causes local dynamics to manifest itself as a seemingly > non-local effect. > > Saibal > > > If N entangled pairs are exchanged, each of Alice and Bob split into > > 2^N branches, covering all possible combinations of UP and DOWN. When > > Alice and Bob meet, there is no control over which Alice-branch meets > > which Bob-branch. If the branch meet-up is random, then in general > > there will be zero correlation, since out of the 2^N Bob branches for > > each Alice branch, only one will give the observed correlations -- a > > 1/2^N chance. In the literature, some attempts have been made to solve > > this problem: for instance, it is sometimes claimed that Alice and Bob > > interact when they meet, and this interaction sorts out the relevant > > branches. But no account of any suitable interaction has ever been > > given, and also, one can reduce the possible interaction between > > Alice and Bob to as little as desired, say by having them exchange > > their data by email, or some such. Another suggestion has been that > > since the original particles are entangled, some magic keeps > > everything straight. I do not find either line of attempted > > explanation in the least convincing, so I conclude that Everettian QM > > cannot account for any correlations, much less those that are observed > > to violate the Bell inequalities. > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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