Radial component of del^2 in spherical coordinates?

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SUMMARY

The discussion centers on the radial component of the Laplacian operator (del^2) in spherical coordinates, specifically in the context of a 3D isotropic harmonic oscillator. The expression provided by the lecturer, 1/r^2 * d/dr * (r^2 * d/dr), is clarified as not being a simple cancellation of terms. Instead, it represents the radial term of the Laplacian, which is essential for understanding the behavior of the system in spherical coordinates. The confusion arises from the misconception that del^2 has vector components, which it does not.

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philip041
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I'm doing a question on a 3D isotropic harmonic oscillator. At one point I need to find write the radial component of del^2.

The lecturer has written 1/r^2 * d/dr * (r^2 * d/dr)

I don't understand cause it looks like he hasn't actually changed anything, r^2 over r^2 ?
 
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In Latex, with parenthesis, the expression might be more clear:

<br /> \frac{1}{r^{2}} \frac{d}{dr} \left( r^{2} \frac{d}{dr} \right)<br />

You're taking the derivative of r^2*d/dr so the r^2 won't just cancel. Also, del^2 isn't a vector so there aren't components. I guess a more correct way would be the radial term.
 
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Ok, I'm really confused.. why isn't the radial part of del^2 in spherical polar coords just dr^2?
 
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