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Ehrenfest's Theorem

  1. Jul 28, 2005 #1
    Can anyone tell me what is the Ehrenfest's Theorm in quantum mechanic, I don't understand how it can provide an example for correspondence principle?
  2. jcsd
  3. Jul 28, 2005 #2


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    Are you familiar with the equation of motion:

    [tex]\frac{d}{dt}\langle Q \rangle = \frac{i}{\hbar}\langle [H,Q] \rangle + \langle \frac{\partial Q}{\partial t}\rangle[/tex]

    where Q is an observable?
    Try putting Q=p (momentum) and Q=r (position).
  4. Jul 28, 2005 #3
    Now I am a bit confused. What's the name of that theorem which forbids static electric and magnetic charges to produce stable equillibrium condition in 3D ?
  5. Jul 28, 2005 #4


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    Are you looking for Earnshaw's Theorem?
  6. Jul 28, 2005 #5
    hehehehe....thank you a lot... I am getting old, my son...
  7. Jul 28, 2005 #6

    It is just the result of the theorem! Any mathematical divide inside?
  8. Jul 28, 2005 #7


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    Yes, the mathematics of showing the correspondence principle at work comes from doing what Galileo suggested and arriving at the classical equations of motion.
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