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Homework Help: Expression for Yl,-l again

  1. Sep 23, 2012 #1
    I have: [tex]Y_l^m= Ne^{im\varphi}P_l^m(cos\theta)[/tex] where

    [tex]P_l^m(cos\theta)[/tex] is the associated legendre polynomials: [tex] P_l^m(cos\theta)=(-1)^m(sin\theta)^m(\frac{d^m}{d (cos\theta)^m})[/tex]

    The problem is that i want to use this expression to apply on it the creation operator for the orbital angular momentum operator i. e to make this function with m = -l; [tex]Y_{-l}^l \rightarrow Y_{-l+1}^l[/tex]

    When i attempt this, i get a very complicated set of derivatives etc, because i havent specified the "l".
    Now, my question is: can i prove this for the general case or do i have to use a specific case, for example l = 1?

    The creation operator is: [tex] L_+ = L_x + iL_y [/tex]

    1. The problem statement, all variables and given/known data

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    3. The attempt at a solution
  2. jcsd
  3. Sep 23, 2012 #2


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    You can probably show it for the general case by using recurrence relations the associated Legendre polynomials satisfy.
  4. Sep 23, 2012 #3
    Thank you very much vela. but i think i should use the expression for the ladder operator?or do u have any idea how to start with the recurrance?
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