Bohmian mechanics...

Discussion in 'Physics' started by cmartinez, Feb 23, 2016.

  1. cmartinez

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    Jan 17, 2007
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    I had never heard of Bohm's theory.

    "Take the debate over whether an electron is a wave or a particle. Bohm’s theory says that it’s both: an electron is a particle with a definite trajectory, but this path is governed by a wave upon which the electron rides. The wave can also be influenced by other particles, which in turn changes the trajectory of the electron."

    https://www.newscientist.com/articl...rdness-may-hide-an-orderly-reality-after-all/

    In a way, I find it harder to understand than quantum mechanics. It's like saying that the electron is an elementary particle consisting of two discernible parts!
     
  2. Wendy

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    That is how I think of a photon, which has the same paradoxes. It is both a magnetic wave and a electric wave merged. May not be correct, but it is my personal model.

    So what wave does an electron ride? Never heard that idea.
     
  3. crutschow

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    One of the stranger things to me in the quantum world is the interference pattern that an electron or photon creates in the two-slit experiment.
    I can sort of see how that can work from the wave-particle duality. when multiple electrons or photons going through both slots at the same time, but, in fact, you also get an interference pattern even if only 1 photon or 1 electron goes through at a time.
    In effect, the photon or electron is interfering with itself. :eek:
     
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  4. cmartinez

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    And that (as I understand it) is the argument of the multiple worlds interpretation. That is, that the photon in this world goes through one slit, but in another world (or reality) goes through the other one, and so ends up interfering with itself.

    But in Bohmian mechanics the particle goes through one slit, but the wave goes through both... and so the mystery disappears.
     
  5. nsaspook

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    When you measure (with the detector) the wave-particle it's not longer a closed thermodynamic system with only 1 photon or 1 electron. One theory is the joint interaction (an entanglement) between the microscopic particle being measured and the macroscopic measurement apparatus is the cause of the seen interference pattern. So there is no switch between wave/particle, it's only our observation of the event that causes an artifact of the 1 photon or electron true single nature.
     
  6. cmartinez

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    so you're partial to the Copenhagen interpretation?
     
  7. nsaspook

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    Yes. We've had this discussion before. Is there some (non-)local hidden variable interpretation (determinism) like Bohm's theory that explains all the results of QM?

    Maybe, maybe not. http://settheory.net/Bohm

    http://quantumfrontiers.com/2012/11/08/its-been-a-tough-week-for-hidden-variable-theories/

    A non-local hidden reality could mean several things, FTL communication is possible, time travel is possible and there is no free-will because the universe is a set piece with a fixed future we are just unable to currently calculate.

    [​IMG]
    "surrealistic" quantum trajectories
    http://www.physics.utoronto.ca/~aephraim/surreal/surreal.html
     
    Last edited: Feb 25, 2016
  8. cmartinez

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    We probably have... but my memory fails me right now.

    I too prefer Copenhagen over the other theories. I think I understand how Bohm's posture leads to a deterministic universe, but I fail to see how the many worlds interpretation could support it, and therefore deny free will. (I'm a staunch advocate for free will, and highly dislike determinism, btw)
     
  9. nsaspook

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    Many worlds just seems (with my limited knowledge) to be a big cheat (anything is possible with infinite choices) to ignore the fact that QM works but is not 'classic' science. With MWI the universe splits with each measurement so the two-slit experiment interference is the photon in multiple real or unreal universes.

    It might be correct but it just sounds wacky.
    http://www.hedweb.com/manworld.htm#deterministic
    http://www.hedweb.com/manworld.htm#free-will
     
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  10. cmartinez

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    Very interesting reading.... I'll take the time later to read it in its entirety. Thanks!
     
  11. BR-549

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    The electrons that make the slit media are rotating at different speeds. But they are all harmonically related. The electron fields occupying the slit space are stable.

    The solitary electron is free and under acceleration, and therefore it is spinning faster than the electron slit fields. The free electron spin is harmonically related to the slit spins.

    A charged particle has a wobble to the spin. You can think of this as a small marker of the 0 degree mark on the spin.

    If the sequential solitary electrons are emitted with the same velocity, and because of the harmonic rotations, depending at what angle the wobble is in, when the fields interact, only certain discrete trajectories are possible. A interference pattern.

    If you time the wobble with velocity, the electron would only hit one spot.
     
  12. wayneh

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    Is there a cat in a box somewhere around here?
     
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  13. hp1729

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    Why is the electron considered a single particle? Why not a wave of smaller packets of energy?
     
  14. cmartinez

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    There probably is... maybe Mr Schrödinger forgot to take it out of the box and bring it home with him...
     
  15. nsaspook

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    Because the predictions and experiments made by classical GR and Quantum mechanics work with electrons being a elementary point particle. The 'why' question is immaterial as that's just the way it is.

    https://en.wikipedia.org/wiki/Deep_inelastic_scattering
     
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  16. BillO

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    I wouldn't call Bohm's work on this a mechanics of it's own. QM is still used, just the interpretation is changed. In any case it is an interesting line of reasoning. After looking at DeBroglie's abandoned work and taking it a bit further it lead him to his thoughts on the Implicate Order.

    I guess he, like Einstein in a sense, did not believe in the 'mysterious' realm we're not to question under the Copenhagen Interpretation. In other words, something determinate is happening to the cat once you close the lid and it doesn't become an indeterminate wave function that collapses only after observation.

    I like the cut of his jib on this.

    Another example: quantum tunneling - the appearance of a particle across an unpenetrable barrier. The traditional view is, you build the QM model given the appropriate states before the tunneling then predict the possibility of the tunneling occurring, and never, ever ask "how did the particle get from here to there". Bohm would argue that there is something to investigate in how the tunneling occurred, and that we should actually investigate it within pre-space.

    It's more comforting than the quasi-religious tone of the Copenhagen Interpretation, but it certainly requires different thinking.

    The whole implicate / explicate order realm is analogous to work I did in university looking at how n dimensional objects look when inserted into (n-j) dimensional space. For instance, who would some 5D object of some arbitrary but known (the the folks in 5D) shape look to us as it rotated around one or more of its axis. We would indeed have no idea of the shape from our limited view and generally the observable results would not be explainable given the limitation of our 3D view on things. Nonetheless, a 'real' object of certain topography would be producing what we observe.
     
  17. nsaspook

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    Physicist Matt Strassler has some very clear articles on this subject.
    http://profmattstrassler.com/articles-and-posts/particle-physics-basics/tunneling-a-quantum-process/

    http://profmattstrassler.com/articl...basics/quantum-fluctuations-and-their-energy/
     
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