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[Q]Expression of Group velocity in QM

  1. Nov 7, 2008 #1

    We already know Group velocity is [itex] \frac{\partial w }{\partial k } [/itex]

    But, liboff said Group velocity is [itex] \frac{\partial w }{\partial k }|_{k_{max}} [/itex] where [itex] k_{max} [/itex] is wave number which probablity this value can be measured is higher than other wave number.

    is it right? How can?
  2. jcsd
  3. Nov 7, 2008 #2


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    Staff: Mentor

    In general, [itex]\omega[/itex] is a function of k, [itex]\omega(k)[/itex], so [itex]d\omega / dk[/itex] is another function of k. To get a particular velocity, you need to specify some value of k to evaluate [itex]d\omega / dk[/itex] at.
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