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Apr4-11, 07:06 AM
P: 848
Quote Quote by Dmitry67 View Post
At first, I wanted to add that historically Von Neumann had recognized the problem you are talking about. He developed his own 'flavor' of Copenhagen Interpretation, where "collapse" was just an information update, not a physical process, avoiding issues with relativity.

After the death of Copenhagen Int. (and also Transaction Int) there are 3 viable Int, and they approach this issue differently.

Stochastic Mechanics - macroscopic, not microscopic events are atomic. particles, fields etc are "just the math" to explain the correlations between the macroscopic events. So in SM it is non-issue: math gives you the formula which is in agreement with the reality - then shut up and calculate. Dont think how some weird stuff "propagates" from Alice to Bob. Neither real nor virtual particles exist in that Int - they are just math. On the contrary, particles tracks in cameras are real.

Bohmian Mechanics - is non-local. Some versions even have a hidden preferred frame. Note that no matter how far particles are in real space, they can be very close in some other configurational space. So BM can be local - but not in our space :) BM also has some weird definition of reality, so I dont want to go further.

MWI - is local, nonrealistic (becased on the commonly accepted definition of realism) but is realistic in a wider sense, because the global wavefunction of the universe is well defined in any point of spacetime. Also, in EPR experiment at least 2 copies of Alice and Bob are created independently. Later they synchronize their data using slow than light channels, and reveal the correlations. Nothing is transfered FTL in such case and ordering of events is well defined.

In MWI there is just a unitary evolution of the wavefunction. There are no particles - just waves (even measurement create an illusion of them and even tracks). Ultimately, the whole world is just one big unbound Feynman diagram

Personally, for me by EPR nature is crying that MWI is true, but not all people agree with me, of course. MWI is also deterministic, so God does not play dice after all..
Good stuff, Dimitry67. Thanks a lot for your summary of interpretations of QM. I do get the impression there are still a lot of Copenhgen physicists around (not necesarily the ones who are actively involved with QM though).