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De Broglie dynamics fine/Bohmian dynamics untenable?

  1. Jun 9, 2013 #1
    An interesting paper within the pilot-wave camp by Colin/Valentini arguing in favour of de Broglie dynamics over Bohmian mechanics:
    Instability of quantum equilibrium in Bohm's dynamics
    http://lanl.arxiv.org/pdf/1306.1576.pdf
     
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  3. Jun 9, 2013 #2

    Demystifier

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    To avoid misunderstanding, it should be stressed that in this paper "Bohmian dynamics" is not the same thing as what one usually means by "Bohmian mechanics". What others call Bohmian mechanics, they call de Broglie dynamics.
     
  4. Jan 4, 2014 #3
    Another paper, this time from Goldstein/Struyve arguing that Bohm's quantum potential dynamics is untenable:
    On quantum potential dynamics
    http://arxiv.org/pdf/1312.1990.pdf
     
  5. Jan 5, 2014 #4
    As far as I understand, to accept Colin/Valentini's arguments, one has to (at least) agree with their statement:

    "if de Broglie's pilot-wave theory is taken seriously it must be admitted that departures from the Born rule (3) are in principle possible -- just as departures from thermal equilibrium are obviously possible in classical dynamics",

    because if such "departures" are not possible, it seems there is no more difference between what they call "de Broglie dynamics" and "Bohmian mechanics" than between, say, different formulations of classical mechanics.

    Their statement does not seem obvious. Let me offer an analogy: it is well-known that the Maxwell equations contain a constraint, but we don't need to believe that departures from this constraint are possible to take the Maxwell equations seriously.
     
  6. Jan 5, 2014 #5

    atyy

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    In my understanding, dBB reduces the interpretive problems of QM to those of classical statistical mechanics, whose interpretive problems are solved by assuming it is incomplete. For example, why can we apply statistical mechanics to "the whole universe at a time"? What ensembles are there if there is only one universe? In statistical mechanics, this is not considered as intractable, because we believe statistical mechanics is an incomplete, effective theory. Also, from an aesthetic point of view, the point of dBB is that QM can be considered incomplete. Either way, if QM is incomplete, there must be departures from QM at some level.
     
  7. Jan 5, 2014 #6
    I may agree or disagree with you that accepting Colin/Valentini's statement "reduces the interpretive problems of QM", but this "reduction" does not make their statement obvious. On the one hand, we don't have any experimental evidence of "departures", on the other hand, de Broglie's pilot-wave theory seems to be still valuable without allowing "departures", even if only a proof that QM allows a realistic interpretation in principle.
     
  8. Jan 5, 2014 #7

    atyy

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    Does this view also mean that you don't find classical statistical mechanics disturbing, given Newton's laws of motion?
     
  9. Jan 5, 2014 #8
    I am not quite sure I understand how this is related to the discussion, but this is my take on classical statistical mechanics: I don't find it disturbing, as it is clear that it is just an approximation: e.g., while Newton's laws do not allow irreversibility, we can live with irreversibility of statistical mechanics regarding it as an approximation.
     
  10. Jan 5, 2014 #9

    atyy

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    I was thinking that if I believe in Newton's laws, I should just need to specify an initial condition for the universe, in which case the applicability of classical stat mech must presumably mean a initial condition was special. Similarly, if I believe in dBB dynamics, I should just need to specify an initial condition for the universe, and the wide applicability of quantum equilibrium must presumably mean something special about the initial condition. In the Newtonian case, it would mean that stat mech is only an approximation valid under some circumstances, and by analogy quantum equilibrium would be valid only under some circumstances.
     
  11. Jan 5, 2014 #10
    Thank you, now I see the relation. However, I don't quite see why a "special" initial condition is impossible in general or incompatible with experimental data. Furthermore, as I said, classical statistical mechanics is just an approximation. I tend to believe that standard quantum mechanics (unlike unitary evolution, which is part of standard quantum mechanics) is also just an approximation, as evidenced by the measurement problem. Also see, e.g., http://arxiv.org/abs/1107.2138 (published in Phys. Rep.), where it is shown for a specific measurement model how deviations from the Born rule and projection postulate appear in the course of unitary evolution.
     
  12. Jan 5, 2014 #11

    atyy

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    Thanks for the reference! I'd actually come across it before. I was interested to find out that Hepp, one of the people they cite is a physicist. I know a little of his work in neurobiology:)
     
  13. Jan 5, 2014 #12
    I don't think this is the same person.
     
  14. Jan 5, 2014 #13

    atyy

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    http://arxiv.org/abs/1107.2138, ref 12: K. Hepp, Helv. Phys. Acta 45, 237 (1972), one of the authors of the Coleman-Hepp model. The paper http://dx.doi.org/10.5169/seals-114381 says Klaus Hepp was at ETH

    There's a Klaus Hepp in neurobiology, also at ETH:
    http://www.ncbi.nlm.nih.gov/pubmed/17728448
    http://www.ncbi.nlm.nih.gov/pubmed/11495962
    http://www.ncbi.nlm.nih.gov/pubmed/8929435
    http://www.ncbi.nlm.nih.gov/pubmed/16572152 (What?)

    Wikipedia has a Klaus Hepp http://en.wikipedia.org/wiki/Klaus_Hepp, whose advisor was Fierz, and who worked in physics and neurobiology. I think that Wikipedia's Hepp is the author of the Coleman-Hepp model, because the Helv Phys Acta paper is dedicated to Fierz. I'm not sure he's the Hepp of the neurobiology papers I linked to, but I thought it was because Wikipedia says he worked on eye movements.
     
    Last edited: Jan 5, 2014
  15. Jan 6, 2014 #14
    Looks like my check was superficial. I apologize. And his breadth of interests is amazing...
     
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