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B Bell's Theorem basic question on contextuality & locality

  1. Jan 16, 2016 #1
    I'm familiar with Bell's Theorem.. have studied it over the years. I'd just like to confirm if my belief is correct. In short. It shows either particles don't exist before measurement or there are hidden variables.. you know all those non-counterfactual and locality arguments.. Specker theorem etc. I know them. But I got confused lately when hbobba can't seem to understand what I'm saying.

    So let me repeat. If you don't believe in non-local influence. Then particles don't exist before measurement correct? I tend to believe in the latter.. but is it right thing to say particles don't exist before measurement? What is the right words to say if it is not semantically correct?

    Whatever, the essence is still particles don't exist before measurements.

    In Physicsforums. the Copenhagen camps (note Ensemble is still cousin to Copenhagen) which is believed by Bill Hobba and company. They keep on saying it is all classical reality with only statistics or probability and it's what QM (and even QFT) is all about. But isn't it EPR shows it is not all classical reality? And particles don't really exist before measurements? Since hbobba believes particles exist before measurement (since this is what Newtonian classical world is all about). How does he or others view EPR.. there are non-local influence or everything is deterministic? Just like Neumaier, hbobba is incredibly advanced mathematically that they can no longer communicate well with beginners without using dense math. So hope others can explain in English. Thank you.
  2. jcsd
  3. Jan 16, 2016 #2


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    The point of Bell's theorem is to show that there AREN'T any hidden variables, or at least not if all interactions are local (propagate at lightspeed or slower).
  4. Jan 16, 2016 #3
    So it's either non-local hidden variables or particles don't exist before measurement. Bohr believes the latter where its part of the experimental setup even if they are located light years away. So is it accurate to say particles don't exist before measurement if you don't believe in non-local hidden variables?
  5. Jan 16, 2016 #4
    I guess the "semantically correct" expression would be the particles' status is undefined, or their properties are undefined. To say they don't exist is already saying something definite (like in their place is a vacuum state or something), which is wrong.
  6. Jan 16, 2016 #5
    Ok. I can't fully understand Neumaier present long thread of it with very dense math. I know he believes in classical reality. So does he believe in non-local influence or hidden variables or no-go theorem regarding EPR and bell's theorem? Can anyone summarize his view with simple english? How does the distant correlations work in Neumaier view? determinism? hidden variables? non-local influence.. how can he make it classical?
  7. Jan 16, 2016 #6
    I understood the opposite, that Neumaier doesn't really think the world is classical, just that classical analogues can be made to make QM look not weird. In the end I'll just disagree until he comes up with a serious explanation of EPR.

    Nor does Bhobba think physics is classical, just that the whole point of QM is continuous transformations between pure states which, even though it's surely not a classical concept, for him it is intuitive. For me it's not. A difference between Neumaier and Bhobba is that the former believes in determinism and the latter doesn't.

    So that's my breakdown on these PF's two users, for whatever reason you needed that.
  8. Jan 16, 2016 #7


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    That belief is completely incorrect. Bell's theorem shows that no local hidden variable theory can reproduce all the predictions of quantum mechanics.

    As this thread is based on a misunderstanding, there is no point in continuing the discussion and the thread is closed.
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