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Should it be upside or downside

  1. Dec 12, 2003 #1
    how does the triangle symbol in Helmholtz Equation should be?
    is it like the attach file in here.
    Last edited: Jan 4, 2006
  2. jcsd
  3. Dec 12, 2003 #2
    or like this attach file.

    btw, can you attach more then one file in here?
    Last edited: Jan 4, 2006
  4. Dec 12, 2003 #3
    If I remember correctly, then they are both the same. nabla squared is sometimes denoted as a triangle with the sharp side up.


    [tex]\nabla^2 \equiv \Delta[/tex]
  5. Dec 12, 2003 #4


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    I've always seen it point down.

  6. Dec 12, 2003 #5
    I also usually see [itex]\nabla^2[/itex]. But [itex]\Delta[/itex] is perfectly valid.

    Personally I prefer [itex]\nabla^2[/itex]. It makes it more clear what operation you're actually performing. Plus it help avoid defining a new symbol for every single mathematical operation. And [itex]\Delta[/itex] is already used enough anyway.

    In the Helmholtz equation in particular [itex]\nabla^2[/itex] looks better.
    [itex]\nabla^2\psi+k^2\psi=0[/itex] is more symmetric.
  7. Dec 12, 2003 #6


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    loop quantum gravity: note well it is [tex]\nabla^2[/tex] and [tex] \Delta[/tex] that are the same not [tex]\nabla [/tex]and [tex] \Delta[/tex]!
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