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Why Bohmian theory is bad?

  1. Aug 11, 2004 #1
    that,s the question..why bohmian mechanics is considered to be false and it is not accepted as a real interpretation of our quantum world?...

    If Bell,s inequality fails for Bohmian theory could somebody tell me why?..thanks.

    In fact i prefer Bohmian point of view rather than the ortodox one,Bohmian mechanics can be used for all purposes (quantizy gravity,and so on), it,s a pity is not accepted.

    In fact theory is non-local but is quantum mechanics really local?...is the c speed limit a real imposition? in fact consider two particle "Alice" and "Bob" then call their wave functions A and B you will probably have that <A,B> (scalar product of function is non-zero, so no mather how far they are ,they will be always interacting...

    in fact the c speed limit is a classical limit imposition not a quantum one..then why take special relativity into account ?..
     
  2. jcsd
  3. Aug 11, 2004 #2

    jcsd

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    Bohmian theory is evil, it has been connected to several explosions and fires.

    Bohmian mechanics is essientially is a nonlocal hidden variables theory, so it is not ruled out by Bell's theorum + the Aspect experiment. The problem is that it has field in the form of the 'quantum potential' which clearly behaves in a nonrelativistic manner due to it's relaist nonlocal nature, so BM is fine for explain nonrelativistic QM, but it can't be married to special relativity in a consistent manner (this is how Quantum Mechanics by Alastair Rae has it, which has a very short but technical introduction to the theory in it).
     
    Last edited: Aug 11, 2004
  4. Aug 11, 2004 #3

    selfAdjoint

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    Bohmian mechanics requires instant communication across potentially great distances between the pilot wave and the particle it controls. This is contrary to relativity, which quantum mechanics is based on since Dirac, and so they reject it.

    It is claimed that Bohm makes the same physical predictions that QM does. There are often spats about this claim on sci.physics.research. It is well not to assert it unlesss you are prepared to counter the objections.

    Bohm is not falsified by the experiments supporting the Bell inequalities. These eliminate LOCAL hidden variable theories, i.e. those which respect relativity. Bohm, as noted above, does not fall into this class.
     
  5. Aug 11, 2004 #4

    jcsd

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    Really, so it's not universally agreed that it reproduces the predictions of orthodox quantum mechnaics?

    As I said the source from which nearly all my knowledge of the theory comes says it does, but though the author is an expert on QM, it's clear from his introduction that he isn't an authority on BM.
     
  6. Aug 11, 2004 #5
    I recently went to a summer school given by the contemporary Bohmians and Spontaneous Collapseans, so I think I have a reasonably good grasp of some of the issues here.

    Can't should really be replaced by hasn't, since it has not been proved that it is necessarily impossible to make a Bohmian version of quantum field theory. In fact, several versions of such a theory are currently doing the rounds and which one you prefer depends on whether you prefer a particle or field ontology and whether you are prepared to accept things like Grassman-valued probability measures.

    Particle ontologies are problematic beacuse bosons are treated in a fundamentally different way from fermions. Field ontologies seem to need these weird probability measures to describe fermionic fields.

    It is still an open research problem whether Bohmian mechanics can be fully unified with relativity.

    The cautious thing to say would be that Bohmian mechanics reproduces the predictions of quantum mechanics, up to the point where those predictions are unambiguous. Since it is not clear what constitutes a measurement in ordinary QM, you could try to show for some experiment QM interprets something as a measurement that Bohmian mechanics doesn't. The Bohmian theory reduces all measurements to position ones, and this works for all known experiments performed to date. If you can work out a way of measuring another variable, such as momentum, without translating it into a position (e.g. the position of a pointer on a measuring device) then you might be able to derive a contradiction.
     
  7. Aug 11, 2004 #6
    Everettians tend to consider Bohmian mechanics false because it has superfluous stuff added to the wave function; see this paper, for example.

    Quote from the paper:

    Bohmian mechanics makes baby Occam cry. :tongue2:
     
    Last edited: Aug 11, 2004
  8. Aug 12, 2004 #7

    It is not really the empirical aspect which makes the difference (in spite of some problems related with the stability of atoms,the lower capacity to deal with spin and so on),Bohm's interpretation is as compatible with the standard mathematical formalism of QM (and with all experiments done so far,Aspect's included) as all the other acceptable interpretations.Indeed even if we consider the above mentioned 'drawbacks' (the accusation is that the offered explanations are rather wooly,unsatisfactory due to their ad hoc status) we must never forget that the orthodox interpretation (in Bohr and Heisenberg's acception at least) fails also to give an explanation to the strange correlations at distance observed experimentally (simply labeling such connections as 'non classical' instead of 'non-local' does not really solve the problem) and that it hardly propose an ontology.So the empirical criterion cannot really make a difference.Some non empirical features are involved here,making scientists (a majority anyway) to prefer the orthodox interpretation as the standard of knowledge.

    First and the most important is that the bohmian mechanics (and more generally all the other interpretations) has a lower degree of coherence with the body of already accepted scientific knowledge,not falsified yet (accepted interpretations of previous experiments included).Namely it puts under doubt the actual version of Special Relativity (based on a specific set of Lorentz transformations) because it reintroduce the notion of a privileged frame of reference (the 'physical meaning of the 'quantum potential' can be interpreted as a sort of ether).It deserves underlining here that the accusation that it implies some transfer of information at superluminal velocities is a red herring,no,there is no conflict here (nature is somehow 'wired',possible outside usual spacetime,but we cannot use this to obtain superluminal transfer of information).

    The lack of a relativistic version of bohmian mechanics is another widely used reason to not prefer it.Still this does not mean this is an impossible task.Indeed the actual set of Lorentz transformation is not the only possible one,compatible with observed facts.Well there exist such transformations which could be compatible with Bohmian mechanics,that is with the possibility to define a privileged frame of reference,currently there is sustained effort (very serious,done by scientists) toward obtaining a relativistic version of bohmian mechanics.

    Thirdly bohmian mechanics is too close to the classical view or in the last 100 years scientists liked to believe that the quantum world marks a total break with the old paradigm (I do not find this too persuasive,some literally believe in it,we should always consider this view as fallible too).


    Finally it must be stressed that by assigning the status of standard of knowledge to the orthodox interpretation (a fact not generally accepted,even among scientists,in the light of Feyerabend's criticism) does not forbid scientists to prefer,subjectively other (valid) interpretations (after all they are all equal on empirical ground) by trying to make them at least theoretically evolving...
     
    Last edited: Aug 12, 2004
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