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B Extra Variable in Non-realism

  1. Jul 7, 2016 #1

    gva

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    What is the name or term called for this extra variable inside non-realism where it can determine the born rule and correlate spacelike millions of light years away? (counterpart of hidden variable in realism (or counterfactual definiteness))
     
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  3. Jul 7, 2016 #2

    DrChinese

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    I don't think there is a name for it. It is somewhat dependent on the interpretation.

    In Many Worlds, a measurement (of say Alice) places the universe into a state where Bob properly matches. So branching is the mechanism. In some interpretations, it is retrocausal effects (that do not appear in other interpretations).

    Each interpretation has its own basic description of the mechanism, and it either makes more or less sense depending on your own viewpoint. In the Bohmian interpretation, hidden variables are nonlocal. In the Time Symmetric (retrocausal) interpretations, hidden variables are local but reside in the future.
     
  4. Jul 7, 2016 #3

    gva

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    How about Copenhagen with actual collapse. This has less baggage than Many Worlds and is not so newtonian like Bohmian and is more profound. Here observation or interaction really collapse the wave function. What is the extra variable in Copenhagen with actual collapse?
     
  5. Jul 8, 2016 #4

    Demystifier

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    If the collapse is actual, then so is the wave function. The actual wave function means that the wave function is real, so such approach cannot be considered as non-realism. Even if the wave function is not an "extra" variable in this approach, it is a hidden counterfactual variable because the wave function is supposed to exist (in a non-collapsed form) even before measurement.
     
  6. Jul 8, 2016 #5

    gva

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    So non-realism involves collapse that is not actual.. then it's just collapse on a paper computation, here there is classical world so it can't be non-realism too. What then interpretation then does support non-realism?
     
  7. Jul 8, 2016 #6

    Demystifier

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  8. Jul 8, 2016 #7

    gva

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    Just read it. It is written "But then any interpretation of QM is “nonlocal” in that sense, including the
    interpretations [5, 6, 7] that deny the existence of objective reality".

    What are the interpretations that deny the existence of objective reality? Don't have reference 5,6 and 7.
     
  9. Jul 9, 2016 #8

    Demystifier

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  10. Jul 9, 2016 #9

    gva

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    Just read it. Interesting. What other interpretations have non-realism. Mermin stuff is interesting and they are encapsulated in only very few sentences. Who agreed to this (and why do you object if you do):

    (Mermin stated)
    "My complete answer to the late 19th century question “what is electrodynamics trying to tell us" would simply be this:

    Fields in empty space have physical reality; the medium that supports them does not.

    Having thus removed the mystery from electrodynamics, let me immediately do the same for quantum mechanics:

    Correlations have physical reality; that which they correlate does not.

    The first proposition probably sounded as bizarre to most late 19th century physicists as the second sounds to us today; I expect that the second will sound as boringly obvious to late 21st century physicists as the first sounds to us today.

    And that’s all there is to it. The rest is commentary."
     
  11. Jul 10, 2016 #10

    bhobba

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    Well while I agree with it's probable intent, a study of interpretations shows the following would be better:
    Correlations have physical reality; that which they correlate may, or may not - the theory is silent on it.

    Thanks
    Bill
     
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