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Why do particles act like waves

  1. Mar 6, 2009 #1
    What are the top theories as to why particles show the interference pattern in the double slit experiment.
     
  2. jcsd
  3. Mar 6, 2009 #2

    malawi_glenn

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    The particle-wave duality is 'explained' in quantum field theory.
     
  4. Mar 6, 2009 #3
    Particles do not act like waves, and wave do not act like particles.
    Only very narrow "wave packets" act like particles
     
  5. Mar 6, 2009 #4
    I see that the behavior of particles is described using waves, but I'm not finding where the 'why' is discussed.
     
  6. Mar 6, 2009 #5

    malawi_glenn

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    I said Quantum FIELD theory
     
  7. Mar 6, 2009 #6
    But how Quantum FIELD theory "explain it"?
     
  8. Mar 6, 2009 #7

    malawi_glenn

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  9. Mar 7, 2009 #8
    The interference picture, consisting of "points", shows probabilistic space distribution. A particle is understood as a point solely so it is not possible to explain interference effects with (classical) "particle" theory. At the same time, waves fill the whole available space, not only one point in it. So the waves are used to describe the spatial spread of interference picture. Of course, they are not usual waves but waves of amplitude of probability. It is the experimental facts that lead to this (QM) picture.

    Bob.
     
  10. Mar 8, 2009 #9
    The explanation is unfortunately that particles as such do not exist. You will have to get rid of your concept of reality, which no one gives up without a fight. For quantum mechanics to work particles must exist in a "quantum state" in between measurements where they don't have exact positions, or speeds. This is all very well established classic quantum mechanics. There is pretty much just one theory about this and all the fancy other theories like quantum field theory, Bohmian mechanics, and even string theory (if it ever gets there) are build such that this theory is reproduced.
    The main problem is interpretation, the question is still open how much reality we can get back into the picture. Can we call the wavefuncion real? Does it collapse at a measurement?
    No one knows, and if you have a book that tells you it does, throw it away please.
     
  11. Mar 9, 2009 #10
    I have to agree with malawi_glenn in this instance, that QFT is the best description, in that it predicts the interference pattern given the energies of the particles involved.

    As to *why* they interfere, no-one knows. But no-one knows why objects fall to the ground when left to their own devices. We can explain it well with theory and even predict quite a lot about *how* they will behave. But not why.

    In this specific instance, I think you'll be looking at the path integral formulation. I'm not sure what your level of maths is, but if you don't know what a functional integral is, look up the Douglas Robb memorial lectures where a clever guy gave an overview of QED for the layperson. It's really quite easy to follow and doesn't mislead at all to my knowledge. Anything you learn will not have to be unlearned later.
     
  12. Mar 9, 2009 #11
    These type of why questions aren't really answerable. It's the same as asking 'Why are there electrons?'. In the abscence of available answers, think about it and reach your own conclusion.
     
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