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I What is the gradient of a divergence and is it always zero?

  1. Nov 14, 2017 #1
    Hi Folks,

    Was just curious as to what is the gradient of a divergence is and is it always equal to the zero vector. I am doing some free lance research and find that I need to refresh my knowledge of vector calculus a bit. I am having some difficulty with finding web-based sources for the gradient of a divergence.
  2. jcsd
  3. Nov 14, 2017 #2


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  4. Nov 14, 2017 #3
    Thanks for the info fresh_42. I found those two links very helpful and I solved my problem of the reason for my inquiry.
  5. Nov 14, 2017 #4

    Charles Link

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    One very important vector identity, (it is used in showing Maxwell's equations result in an electromagnetic wave equation), is ## \nabla \times \nabla \times \vec{A}=\nabla (\nabla \cdot \vec{A})-\nabla^2 \vec{A} ##. For the case that is often shown to demonstrate the wave equation in a vacuum, ## \nabla \cdot \vec{E}=0 ##, but in general, the first term on the right side of the vector identity equation is not equal to zero.
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