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Help with Poisson Brackets (original paper)

  1. Jan 24, 2008 #1
    Here I have a translation from French to English of the original paper by Poisson about his brackets. I cannot understand why the function a=f(q,u,t) doesn't have a second order derivative (in q or u). The problem is on the top of the third page (second .JPG) after he took the time derivative. Can somebody help me?
     

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    Last edited: Jan 24, 2008
  2. jcsd
  3. Jan 25, 2008 #2
    Also, a=f(q,u,t) is a constant of motion. Is there any restriction about second order derivatives for q or u or (p) for a constant of motion?
     
  4. Jan 26, 2008 #3
    Here is a quotation that I found on Wolfram website:

    "A first integral associated with the independent variable t exist if f is independent of t and does not contain any second or higher derivatives of the coordinates."

    Since we have a=f(q,u,t) as a firt integral, it will not have a second derivative of any canonical variables.

    What I can't understand and ;also, I didn't find anywhere is why a first integral of the motion can't have a second order derivative.

    Does anybody know?
     
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