On 25-03-2022 23:01, Bruce Kellett wrote:

On Sat, Mar 26, 2022 at 6:37 AM smitra <smi...@zonnet.nl> wrote:On 24-03-2022 22:57, Bruce Kellett wrote:OK. I see now that your insistence that QM is local is based ondogma,rather than logic. Your claim is that the unitary time evolutionin QMis local, therefore QM is a local theory, regardless of anythingelse.But that position relies on another hidden assumption. The unitary time evolution of QM depends on the Hamiltonian. The Hamiltonianisnot given by the theory; it is constructed according to thedetails ofthe system one is attempting to model. Generally, one is modelling local systems, so one uses a local Hamiltonian and the timeevolutionis local. But this is by no means necessary. One could always useanon-local Hamiltonian, then the time evolution would not be local.One can indeed write down non-local effective Hamiltonians, but the fundamental laws of physics are strictly local.God told you this, did he? If one needs non-local physics to describe certain experiments, then locality is not universal.

`The Standard Model is local. If you can experimentally verify that for a`

`certain physical system the Standard Model (extended to take into`

`account finite neutrino masses) is not adequate, then you'll win the`

`Nobel prize for that discovery. We know that the Standard model has to`

`fail when quantum gravity will become important. But we cannot probe`

`this regime experimentally, and for the sort of things we're discussing`

`here, it's not relevant.`

This is the situation with the entangled spinor case. The statevectoris non-separable and does not specify any particular separationforthe two entangled particles. If one wants to continue to treatthis asa single system even when the particles are far apart, one mustuse anon-local Hamiltonian.The fundamental Hamiltonian that also describes how the entangled state was created, is local. It's only when you put in the entangled spinor state in by hand that you get an effective non-local Hamiltonian.Where did you get the idea that the entangled spinor state was "put in by hand"? Sure, the entangled spinor state was created locally, but it is intrinsically non-local in that it refers to arbitrarily separated states in terms of a non-separable wave function. The entanglement is created at some point then particles move apart, but this separation preserves the entanglement, and if you are to understand the results of measurements on this entangled pair, you must consider it as a unified system, not as two separated and independent parts. That is, the system is intrinsically non-local, and you will never be able to understand a non-separable system in terms of independent parts. Do you not understand what "non-separable" means?

`What matters is the time evolution step by step proceeds in a manifestly`

`local way. The entangled spin system is created locally, the two`

`particles travel to the locations of Alice and Bob. Alice and Bob and`

`their polarizers considered as large collections of particles interact`

`locally with the spins. While you then do find correlations that exhibit`

`nonlocal properties, there is then a local account of how these`

`correlations arise, namely the time evolution via the Schrodinger`

`equation with a manifestly local Hamiltonian. Such a Hamiltonian is`

`always available because the well established low energy physics won't`

`violate the Standard Model.`

Saibal

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