On 3/3/2022 9:05 AM, smitra wrote:

On 03-03-2022 01:05, Bruce Kellett wrote:On Thu, Mar 3, 2022 at 10:50 AM John Clark <johnkcl...@gmail.com> wrote:On Wed, Mar 2, 2022 at 5:50 PM Bruce Kellett <bhkellet...@gmail.com> wrote:_> Many worlds is not a local theory._Many worlds can explain all known experimental results without resorting to non-local influences because many worlds is not a realistic theory.In that case, if you believe that MWI is local, give me the local account of Bell-type correlations of spin measurements at spacelike separations. I will salute you if you can do this, because no one else has ever managed in the past. Realism is completely beside the point. BruceIt's trivial, as the dynamics is described by a Hamiltonian that onlycontains local interactions. This mans that all non-local effectsarise via common cause effects. The creation of the entangled pair ofspins happens at some space-time point, so it's the result of localinteractions. The later when Alice and Bob each receive one of the twospins, *they get correlated* with the spins they measure, because theyand their measurement gear consist of particles that evolve accordingto the Schrodinger equation too and that evolution also only involveslocal interactions.

`You write "the get correlated", but breaking statistical independence`

`requires that the instrument settings be *already correlated* with the`

`spins before they interact with the instruments and Alice and Bob. That`

`could be thru some common cause, but it seems unlikely when the`

`polarization settings are determined by photons from many light years`

`away on opposite hemispheres of the cosmos. That implies a very long`

`chain of local interactions to the common cause.`

Brent

This then causes Bob and Alice to evolve in superpositions that arecorrelated as a result of the initial entanglement of the spin.What goes wrong in arguments about this issue is when people switch toa classical picture as soon as Bob and Alice arise who with theirmacroscopic measurement devices measure the spin components in certaindirections. The picture in which a macroscopic effectively classicalBob and Alice collapse wavefunctions is not the correct picture. It isonly a FAPP effective description of what really is going on, but itwill hide the local nature of QM due to replacing the exactdescription by an effective description.Another example of how apparent non-locality arises due to replacingan exact QM description by treating effectively classical quantitiesas classical instead of quantum mechanical, is the Aharanov-Bohm effect:https://arxiv.org/abs/1906.03440"In the Aharonov-Bohm (AB) effect, a superposed charge acquires adetectable phase by enclosing an infinite solenoid, in a region wherethe solenoid's electric and magnetic fields are zero. Its generationseems therefore explainable only by the local action ofgauge-dependent potentials, not of gauge-independent fields. This wasrecently challenged by Vaidman, who explained the phase by thesolenoid's current interacting with the electron's field (at thesolenoid). Still, his model has a residual non-locality: it does notexplain how the phase, generated at the solenoid, is detectable on thecharge. In this paper we solve this non-locality explicitly, byquantising the field. We show that the AB phase is mediated locally bythe entanglement between the charge and the photons, like allelectromagnetic phases. We also predict a gauge-invariant value forthe phase difference at each point along the charge's path. We proposea realistic experiment to measure this phase difference locally, bypartial quantum state tomography on the charge, without closing theinterference loop."Saibal

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