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Retarded Fields

  1. Apr 9, 2012 #1
    While studying Jackson J.D. "Classical Electrodynamics" 3rd edition in chapter 14.1, page 663 he does something that I don't quite get it.

    He gets an expression for the retarded potencial and says that he can use the integral form of the 4-potencial to easily get an expression for the Maxwell tensor. Then he explains that he must do the derivative and that derivative must apply to both the [itex]\theta[/itex] and [itex]\delta[/itex] function. All that I agree.

    Then he applies the first derivation to the [itex]\theta[/itex] function and explains that it constrains the [itex]\delta[/itex] function and get [itex]\delta(-R^2)[/itex] so that term is only important when [itex]R=0[/itex]. I still agree.
    But then he discards it saying it makes no contribution if one excludes the point [itex]R=0[/itex]...Why can he discard that point?

    Thank you
    Last edited: Apr 10, 2012
  2. jcsd
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