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Is quantum mechanics fundamental theory?

  1. Aug 23, 2011 #1
    Is there any proof that quantum mechanics is truely fundamental? that is , QM is not an approximation to another more fundamental theory . If this is the case then maybe all theories beyond the standard model that are based on quantum mechanics are only approximations to the true theory of nature .
     
  2. jcsd
  3. Aug 23, 2011 #2

    Fra

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    No there is no such proof, so it's certainly possible QM is an approximation (or limit) of some better theory.

    But, QM is more like a framework. You still need to put in say a lagrangian or hamiltonians. So the question translates into asking wether QM can be an approximation or limiting case to a better "measurement framework" and I personally think there are many quite good reasons to expect that is the case.

    Just to mention some ideas see

    Could quantum mechanics be an approximation to another theory?
    "We consider the hypothesis that quantum mechanics is an approximation to another, cosmological theory, accurate only for the description of subsystems of the universe..."
    -- Lee Smolin,http://arxiv.org/abs/quant-ph/0609109

    Edit: I think that alot of people that ask such a question has a secret desire to restore realistic theories, such as is there a better deterministic theory to which QM is an approxiatmion? I suppose possible may pass, but I really don't think so. What I have in mind, is something that is even more weird than QM. I think quantum mechanics with it's fixed hilbert spaces will appear very "realistic"(read old fashioned) as compared to the yet unknown cosmological measurement theory.

    /Fredrik
     
  4. Aug 23, 2011 #3
    Quantum mechanics is the best theory we have, period. When it comes to quantum mechanics some theories even suggest the whole question of what is "truly fundamental" is meaningless. Along the lines of asking what is north of north or the flavor of the color blue. If you really have to know the answer I suggest asking a priest, politician, or mystic. They also seem to think they know what is truly fundamental.
     
  5. Aug 23, 2011 #4
    OP pissed in your cheerios?
     
  6. Aug 23, 2011 #5
    Blue tastes like blueberries, obviously!
     
  7. Aug 23, 2011 #6
    The sciences and especially physics have enough trouble with institutionalized denial and cranks without encouraging more nonsense.
     
  8. Aug 23, 2011 #7
    It's a question. Science runs on falsification, not blind adherance void of skepticism.
     
  9. Aug 23, 2011 #8
    Physics doesn't have proofs of truth. Theories have domains of applicability. Experimental evidence can disprove or limit the domain of a theory. Quantum mechanics is still standing. Anything further is metaphysics, not physics.
     
  10. Aug 23, 2011 #9

    Chronos

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    This is dangerously close to philosophy. It begs the question of what is a 'complete' theory.
     
  11. Aug 24, 2011 #10
    By that criteria "What is the sound of one hand clapping?" is also a valid scientific question. If you can't define the terms and can't even demonstrate that it isn't just gibberish it doesn't qualify as science.
     
  12. Aug 24, 2011 #11
    I always thought you are allowed to ask that (type of) question here in PF. And I thought, the best answer is "No, sorry, you are missing something. You can't clap with one hand" or like that.
    I don't know anything about the Op though!
     
  13. Aug 24, 2011 #12

    jtbell

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    Staff: Mentor

    Is there any proof that any theory is "truly fundamental?"

    How will we know when we have found a "truly fundamental" theory?
     
  14. Aug 24, 2011 #13

    Fra

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    I'm starting to think you should check your your cheerios too :wink:

    I think most responses trivializes and ridicules a potentially interesting and very valid question.

    Quantum mechanics works on ensembles or statistics, and that very framework simply becomes ambigous at best when you consider cosmological theories or open systems. Quantum mechanics as it's verified mainly predicts scatting matrices, which are perfectly well defined observables as long as you look at a subsystem, such as a collider embraced by a classical laboratory. Here there is no problem to encode the hilbert space and generate statistics in the environmnet.

    But now instead consider that we aren't looking into an atom, we are looking into our environment. Here we can not get away with the same trick.

    This is not really a stupid question at all. It has to do with how to define proper observables and how the observer can verify his own theories. If you think a little bit about this, things we do get away with for scattering experiments will not work out in a cosmologicla model.

    Smolin has in that paper (and in other talks http://pirsa.org/08100049/) made the case that quantum mechanics and in fact ant theory with a fixed timeless state space, is likely to be the limiting case of another model (the limit where you consider a subsystem, and the theory lives in the environment). Smolins arguments and ways might not be the ultimate arguments but at least it's an example of reasoning.

    /Fredrik
     
  15. Aug 24, 2011 #14
    Since the moderators haven't locked this thread I believe that is a safe assumption. By that same criteria, it is also evidently quite acceptable to call such questions gibberish. If people prefer I can be more formal and say something like, "The context is too broad, the terms are undefined, and it is semantically meaningless", but gibberish sums it up nicely.
     
  16. Aug 24, 2011 #15

    Fra

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    How to respond to a poor question?

    You can either just reject it (which seems not so constructive in a forum) or if it's at least in the ballpark, the response might be a suggested refinement of the original question with some following comments. To me the OT was least in the ballpark of an interesting discussion.

    I don't know how deep the OP meant the question, but I at least made an attempt to rectify it before suddently the thread was about troubleshooting your cheerios :)

    /Fredrik
     
  17. Aug 24, 2011 #16
    I don't eat cereal.

    Personally I don't see the question as either interesting or valid. We are innately curious and deeper explanations can be useful so we keep looking. To me such questions are no more useful or interesting then reading nonsense poetry like the Jabberwocky. Such things might be useful for literary or psychological purposes, but this is a physics forum.

    As for Smolin, again, I don't require any abstract rationale to keep looking for deeper answers. Nor am I sure I would recognize any "ultimate arguments" if I saw them. Either he can produce a compelling case that provides some possible avenue to explore or it is just a fancy example of asking what the sound of one hand clapping is.
     
  18. Aug 24, 2011 #17
    I may have stated the question incorrectly but the point of this question is that hidden variables may be missing from the theory to render it deterministic and explain entaglement so faster than light communication will not be needed . If these hidden variables are present then it might have effect on standard model .
     
    Last edited: Aug 24, 2011
  19. Aug 24, 2011 #18

    Fra

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    This was what I suspected. This suggestion of yours is in a completely different direction than I had in mind, it's even in the opposite direction. My suggestion deprives us from even more realism in the sense that not even the statistics and ensembles are real.

    The restoration of realism, as in the original objections of Einstein etc are IMHO really not sound anymore. I'm not sure if you are aware of the historical arguments of EPR objections to QM, Bells inequality etc. It's inequality that a local hidden variable theory must obey, and QM is shown to violate it, both theoretically and experimentally.
    http://en.wikipedia.org/wiki/EPR_paradox
    http://en.wikipedia.org/wiki/Bell's_theorem
    There are some people that still work on this, looking for loopholes tec, but IMO it does not seem like rational objections anymore. Instead the problems I refered to are completely different and much more profound. It really has Nothing to do with the original EPR objections or the desired to restore realism. To try to understand these objections check out smolins talke and paper.

    Note though that there is no actualy FTL communication possible in QM (which would certainly be unacceptable and unreasonable). Non-local correlations is something different than communication and non-locality.

    /Fredrik
     
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