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Poisson Bracket Porperties

  1. Jun 18, 2012 #1
    Hello,

    If you have two observables f and g both of which start off as: f =0 and g =0 and you evaluate their possion bracket:

    {f,g}, will it necessarily be equal to zero?

    Also, if just f=0 and g wasn't zero, would {f,g} =0?

    Thanks!
     
  2. jcsd
  3. Jun 18, 2012 #2

    Physics Monkey

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    What do you think?

    Are f ang g identically zero? or zero at the "start" (= initial time?) only? or zero only when some constraint is applied?
     
  4. Jun 18, 2012 #3
    f and g start out being zero. so because the poisson bracket consists of derivatives of f and g, it need not necessarily be zero even if f and g started off being zero? this is what i would think.

    but i'm reading a research paper that seems to suggest that if f anf g start off being zero, then the poisson bracket {f,g} is always zero.
    but if only one of them started out being zero, {f,g} needn't be zero. i don't understand why this would be true.

    thanks!
     
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