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Homework Help: Simplification - complicated summation involving delta functions

  1. Apr 2, 2014 #1
    Simplification -- complicated summation involving delta functions

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

    [itex]\frac{1}{\sqrt{(2^3)}}[/itex][itex]\sum[δ(k+1)+δ(k-1)][/itex]|k> for k=0 to 7

    2. Relevant equations

    3. The attempt at a solution
    I am trying to simplify the above expression. I get [itex]\frac{1}{∏*\sqrt{(2^3)}}[/itex] |1>, which is incorrect because |1> should have occurred with a constant 1.
    Is it right to say that the first delta function can be ignored because my K is not defined for -1?
  2. jcsd
  3. Apr 3, 2014 #2


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    Is this really the correct problem statement ? Or just some step in a sequence of steps where you stumble at this point ?

    Any idea what the |k> stand for ?

    What definition of (or prescription for) ##\delta## do you have available under 2. ?
  4. Apr 3, 2014 #3


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    Halaaku, when you post in the homework forum, you need to state the problem more accurately than this, and then show us your thoughts on how to solve it.

    If it's a sum rather than an integral, I have to assume that the deltas are Kronecker deltas rather than Dirac deltas. But if you use the notation ##\delta(k-1)## rather than ##\delta_{k,1}##, I have to assume that these are Dirac deltas. The problem doesn't make much sense as it appears in your post.
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