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I What do you think of the alternate interpretations of QM?

  1. Dec 29, 2016 #1
    The standard interpretation of QM advocates that there are no "hidden variables", and that the universe is not deterministic. Sure, maybe Bell's work supports that view, but there exist some deterministic theories of quantum mechanics (like the De Broglie-Bohm theory) or other stuff, like the many worlds interpretation, that are consistent with that. What is your personal opinion on such theories?
     
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  3. Dec 29, 2016 #2

    Nugatory

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    It's not clear to me that there is a "standard" interpretation of QM - if there were such a thing, then we wouldn't have so many endless and inconclusive threads on interpretation. (Search for these threads and read them - there's been a lot said on the topic already).

    You are also somewhat misstating the conclusion of Bell's work. It doesn't show that there are no hidden variables, or that the universe is necessarily non-deterministic; it excludes those hidden variable theories that have particular characteristics. It's interesting because these characteristics ("locality" and "realism") are required of any theory that matches our classical intuition of how things work; so in effect it says that we must abandon this classical "common-sense" view of the world.

    All interpretations predict the same experimental results so there is no way of objectively determining which one is "right". You are free to choose whichever interpretation you are most comfortable with, or even to choose one or another according to whatever makes it easiest to reason about the problem you're working on right now. On the one hand, de gustibus non est disputandum, and on the other hand for many people such matters are the only things worth arguing about.
     
  4. Dec 29, 2016 #3
    Sure. That's why I said that some hidden variable theories are consistent with it.

    The Copenhagen interpretation is frequently considered the "standard" interpretation. By "alternate" I mostly meant hidden variable interpretations.
     
  5. Dec 29, 2016 #4
    My opinion is I find it more interesting to get the right answer than to ponder what it all means.
     
  6. Dec 29, 2016 #5
    For me, the biggest problem with Copenhagen is that it artificially bifurcates the world into two incommensurable realms: one for which the formalism of Hilbert spaces, etc., can be applied, and one for which it can’t. What results is an odd, dualistic ontology that is deeply anti-physics, at least in my estimation. The obvious remedy is to apply QM’s formalism to all systems, including the measurement apparatus, the observer, and the ambient environment. What I’m describing, of course, is the Everettian approach. The question then becomes if such a universal, disciplined application of QM’s formalism can somehow reproduce the world of common experience. Based on my understanding of the mechanism of decoherence, I think it can.
     
  7. Dec 29, 2016 #6
    That's a good opinion, but I know it doesn't satisfy some people.
     
  8. Dec 29, 2016 #7
    That approach is very popular from what I have observed, but isn't it a bit... I think the best way to describe it is ad hoc? Don't get me wrong, it intuitively makes more sense, but while the Copenhagen interpretation is more general and does not attempt to explain anything at a deeper level, the many worlds interpretation introduces literal new worlds completely out of the blue! I feel a bit uncomfortable with the way it is hypothesized.
     
  9. Dec 29, 2016 #8
    Nowadays, most Everettians view the so-called 'many worlds' as a consequence of unitary evolution and decoherence, rather than an a priori input to the theory.
     
  10. Dec 30, 2016 #9

    Demystifier

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    I think it is always illuminating to think of different interpretations of the same observed facts.

    Concerning QM, I like the analogy with magic tricks:
    https://www.physicsforums.com/threa...-bohmian-mechanics.898028/page-5#post-5652596
     
  11. Dec 31, 2016 #10

    bhobba

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    I think the importance of different interpretations is twofold:

    1. Pick an aspect of QM you do not like and we have an interpretation that gets rid of it - but not all at once. Note - what one likes or not likes is very personal and beyond science. Its very wise to always keep this in mind when discussing interpretations.

    2. It sheds light on what the formalism says. For example it may seem the formalism is inherently probabilistic, but since we have interpretations where it isn't that's wrong. Similarly for collapse. Once you realize this some of the discussions about the foundations of QM especially in popularizations, beginner texts and the writings of the early pioneers; some love to quote; is well almost laughable. It really allows you to cut through BS.

    Thanks
    Bill
     
  12. Dec 31, 2016 #11

    Paul Colby

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    Classical mechanics is simply a set of rules that provides reliable predictions and models of various phenomena. People claim they understand it which I argue really means they feel "comfortable" with the rules of classical mechanics. Same is true for QM, just different rules which applies to energy and size scales we don't live in. And, of course, no one will allow you to claim to be comfortable QM rules either.
     
  13. Dec 31, 2016 #12
    My last post was removed, because it didn't meet the required standards of a reference. Here it is:

    "So you think it really doesn't matter at all? Well, maybe now it doesn't, but I remember reading something about some physician proposing an experiment involving some macroscopic quantum eraser that could provide evidence supporting an interpretation over the others."

    Well, I looked it up. There was a 1986 paper by David Deutsch titled 'Three experimental implications of the Everett interpretation' that proposed some ways to test the MWI. There's also this very interesting entry: https://plato.stanford.edu/entries/qm-manyworlds/ (read number 5). From what I have understood so far, Deutsch's proposed experiments essentially require using cats (well, not cats, macroscopic objects you get the idea) in the place of electrons and other tiny particles for usual quantum erasure/interference experiments

    There's a very disappointing quote from that source: "These proposals are all for gedanken experiments that cannot be performed with current or any foreseeable future technology."

    I think stuff gets less scientific and more philosophical beyond this point.
     
  14. Jan 1, 2017 #13

    bhobba

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    Well since the modern version of MW is the same as decoherent histories except the histories all occur instead of just one that seems very very unlikely - in fact I would say impossible.

    All these various interpretations were deliberately cooked to have the usual QM formalism. All you would end up doing is confirming that formalism because of the way they were developed.

    A while ago some people though they could tell BM from regular QM and even did some experiments
    https://arxiv.org/abs/quant-ph/0206196

    This caused quite a stir but sounder reasoning prevailed and the flaw discovered (it had something to do with an incorrect use of the Dirac Delta function if I remember correctly) - as it must be for the reason I cited above.

    Thanks
    Bill
     
  15. Jan 2, 2017 #14
    Yes, but either one or the other interpretations must be correct, they can't all be correct at once, so there must be something to distinguish them.
     
  16. Jan 2, 2017 #15
    Different interpretations can all be correct even if they contradict. There is no right or wrong interpretation.
     
  17. Jan 2, 2017 #16

    Paul Colby

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    If this were true, they wouldn't be interpretations they would be distinct theories. My understanding they are the same theory with different words sprinkled on top.
     
  18. Jan 2, 2017 #17

    bhobba

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    That is fallacious reasoning.

    For example it is well known there is no way to tell the difference between LET and standard SR, so much so many physicists would call them the same theory.

    In order to prove your assertion you must figure out a way to do it. Some claim to have done so but they have not stood up.

    Thanks
    Bill
     
  19. Jan 4, 2017 #18
    What does LET stand for?

    From my understanding, all the different interpretations produce the same observations when it comes to wavefunctions etc., but there are differences between them. If you can't possibly distinguish between them, it's not scientific. I might as well say that a flying spaghetti monster comes in and solves everything.
     
  20. Jan 4, 2017 #19

    Nugatory

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    Lorentz Ether Theory.
     
  21. Jan 4, 2017 #20

    Nugatory

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    That's the FSM interpretation. No one uses it because it doesn't seem to make any problems easier to reason about (unlike, for example, collapse interpretations which many people find helpful in talking about many problems) and just about everyone finds it ugly and absurd. But this is just reinforcing the point I tried to make in the last paragraph of post #2 in this thread: interpretations are chosen on the basis of utility and aesthetic appeal to the interpretation-holder.
     
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