Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Smolin's - Could quantum mechanics be an approximation to another theory?

  1. Jan 18, 2008 #1


    User Avatar

    I'm curious if the question posed my Smolin

    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. Quantum theory is then to be derived from the cosmological theory by averaging over variables which are not internal to the subsystem, which may be considered non-local hidden variables. We find conditions for arriving at quantum mechanics through such a procedure. The key lesson is that the effect of the coupling to the external degrees of freedom introduces noise into the evolution of the system degrees of freedom, while preserving a notion of averaged conserved energy and time reversal invariance...."

    -- http://arxiv.org/abs/quant-ph/0609109

    Has been reflected/discussed here in some past thread? I'm curious to here how others reflect on this?

    First, how do you reflect over the relevance of the first overall question? and second, how do you reflect over the suggested reasoning

    "Quantum theory is then to be derived from the cosmological theory by averaging over variables which are not internal to the subsystem, which may be considered non-local hidden variables."

    (I tried to use the search function on where with a string in quotes, but it seems to interpret it as a collection of single search words? and thus I get all kind of bogus hits? or how do you search a string?)

    Last edited: Jan 18, 2008
  2. jcsd
  3. Jan 18, 2008 #2


    User Avatar
    Science Advisor

    I remember that Marcus has already started a discussion about this paper, but perhaps only as a part of another thread, not as a separate thread.
  4. Jan 18, 2008 #3


    User Avatar

    Thanks. It seems the PF's internal search function could be alot better.

    OTOH, good old google comes to the rescue, I tried googling "Could quantum mechanics be an approximation to another theory" and "physicsforums" and immediately identified this.

    "String theory and foundations of quantum mechanics"
    -- https://www.physicsforums.com/showthread.php?t=143062

    Which happens to be started by Demystifier :)

  5. Jan 18, 2008 #4


    User Avatar

    What is more impressive is that this thread - started this morning - is already indexed on google. All you need to learn these days is howto google ;-)

  6. Jan 18, 2008 #5


    User Avatar
    Science Advisor

    Actually, I have decided to register on this forum when I googled my name and found a discussion about one of my papers. :-)
  7. Jan 18, 2008 #6


    User Avatar

    I looked at the old thread.

    I've got a question for you Demystifier.

    As per the old thread, you wrote in some paper:
    Here, the Bohmian interpretation is not postulated, but derived from the requirement of covariance.

    SelfAdjoint responds:
    Well, no. It is derived from your desire to have a covariant particle description which is not the same thing.

    You respond:
    SelfAdjoint, you are right that we cannot rule this out. But I hope that you will agree that my desire to have a covariant particle description is not unreasonable.

    Now, I wonder what your reasoning is aroung rating the possibility that the classical "particle concept" is far more twisted than one might thing extrapolating classical intuition?

    And whatever "a particle" really is - how can we define it? ie. wouldn't we expect, indirectly, in terms of processed historied, that even the particle concept is acquired, and can thus be rated according to picturing statistics on the acquisition process?

    I'm sort of questioning the physical basis of the premises. The question is, what kind of premises and initinial conditions that can be "valid" - ie. based on locally available information to the observer.

    For example, the concept of open vs closed systems. Often, one considers a closed system, but the question is of course, how is the concept of closed defined in terms of interactions with the observer? how does an observer inform himself about this? to me, the concept of "closed" is rather a preconception of how the systems is expected to behave, which is no physical basis. If it does behave as expected, it's closed, if not, then in retrospect one could say "we was wrong, it wasn't closed". But then what is going on is nothing but guessing and gambling.

    So to me it seems that some of the premises and initial conditions are, rather than physical in nature, are more like "initial expectations" which one has by definition no other way of verifiying other than to "play on" and gamble. This does itself implement a fundamental uncertainty to nature.

    So there seems to be two dual views here.

    One view is what strategy should someone with incomplete information evolve and implement to survive in an unknown evironment?

    The other view, more closely related to the decoherence ideas, is how someone with "eyes everywhere", can understand the "logic" of the actions witnessed by
    a smaller observer.

    A missing link IMO, is the one connecting the two. Because the concept of "averaging over hidden variables" only makes sense in the latter view? Because for the one to which the variables are truly hidden, what does the statement of averaging over them mean? because to that observer, as I see it, he can not even index or catalog this hidden variables (aside from determining it's value).


  8. Jan 18, 2008 #7


    User Avatar
    Science Advisor

    Fra, I think one can easily understand my point if view by thinking in a manner that is usual in CLASSICAL statistical mechanics.
    To remind you, atoms were also considered hidden variables (supposed to explain thermodynamics) until a century ago. Now they are considered a fact.
    Such a reasoning lies also behind the Smolin's paper above.
  9. Jan 18, 2008 #8


    User Avatar

    Ok, then I think I roughly see your reasoning, I just wanted to check what your thinking was, because I like most of your posed questions about QM issues in past posts, but not always your answers. This intrigues me.

    I appreciate Smolin's question in that papers. I also share your views that a fundamental theory should resolve the issues with the QM formalism.

    But this point (common reasoning to stat mech) is exactly what I do not quite like about his supposed resolution.

    This relates to

    "A possible solution to the problem of time in quantum cosmology"

    where Smolin ponders

    "What is then needed is a new approach to statistical physics based only on the evolving set of possibilities generated by the evolution from a given initial state."

    Isn't it interesting that the foundational issues of QM, really seem inseparable from issues arising in QG? This is why I have problem with the idea that these aren't related. To me the "new statistics" I seek, that I thought Smolin was afte in the above paper (but then again, maybe not?), should answer to us what inertia is, and how the inertia proves to be a key to the stability in a new crazy statistics.

    If anyone on here, radically differs in the view from anything yet put forward, it would be interesting to here a completely new perspective? anyone?

  10. Jan 18, 2008 #9


    User Avatar

    There is nothing that so to speak prevents a speculation to later turn out to be "the expectation of choice".

    This does however not mean that the speculation was true to start with, because this measure refers to the future. The actions back then was nevertheless IMO depending on the information at hand, rather than the future states.

    Statistics itself, is not trivial, and there is also a massive distinction between doing statistics on subatomic particles in labs on earth, as compared to doing statistics on the cosmology scene. I think the idealizations done in the normal statistical reasoning, of making up ensmebles and so on, doesn't quite make sense.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook