Laplacian in spherical, glomar coordinates

Higher-dimensional geometry (previously "Polyshapes").

Laplacian in spherical, glomar coordinates

Postby alkaline » Sat Jan 17, 2004 3:13 pm

I have calculated the laplacian in glomar coordinates. That was quite the task.

The laplacian in spherical coordinates:
(L)[sup]2[/sup] = (d/dr)[sup]2[/sup] + 1/r[sup]2[/sup]*(d/dθ)[sup]2[/sup] + 1/r[sup]2[/sup]sin[sup]2[/sup]θ*(d/dφ)[sup]2[/sup]

The laplacian in glomar coordinates:
(L)[sup]2[/sup] = (d/dr)[sup]2[/sup] + 1/r[sup]2[/sup]*(d/dθ)[sup]2[/sup] + 1/r[sup]2[/sup]sin[sup]2[/sup]θ*(d/dφ)[sup]2[/sup] + 1/r[sup]2[/sup]sin[sup]2[/sup]θsin[sup]2[/sup]φ*(d/dω)[sup]2[/sup]
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Re: Laplacian in spherical, glomar coordinates

Postby alkaline » Sun Jan 18, 2004 4:07 pm

actually, it looks like these might be wrong. The spherical coordinate version is supposed to be:

(L)[sup]2[/sup] = 2/r*d/dr + (d/dr)[sup]2[/sup] + 1/r[sup]2[/sup]*cosθ/sinθ*d/dθ + 1/r[sup]2[/sup]*(d/dθ)[sup]2[/sup] + 1/r[sup]2[/sup]sin[sup]2[/sup]θ*(d/dφ)[sup]2[/sup]
Last edited by alkaline on Mon Jan 19, 2004 7:03 pm, edited 1 time in total.
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Re: Laplacian in spherical, glomar coordinates

Postby Aale de Winkel » Mon Jan 19, 2004 6:05 am

alkaline wrote:(L)[sup]2[/sup] = 2/r*d/dr + (d/dr)[sup]2[/sup] + cosθ/sinθ*d/dθ + 1/r[sup]2[/sup]*(d/dθ)[sup]2[/sup] + 1/r[sup]2[/sup]sin[sup]2[/sup]θ*(d/dφ)[sup]2[/sup]


I don't know why Eric Weisstein put it into the form shown in:
http://mathworld.wolfram.com/Laplacian.html
a quick further derivation of that version shows you are probably correct with the above "quoted version" :lol: A further look though, derivation of wolframs third term your third term looks more like: [1/(r[sup]2[/sup]tan(θ))] δ/δθ (so you missed deviding by r[sup]2[/sup])
the rest of your terms I could reobtain from Eric's more compact version!

I don't know though whether it is correct to write δ[sup]2[/sup]/δθ[sup]2[/sup] as (δ/δθ)[sup]2[/sup]

Boy you have me reaquainting with stuff I have forgotten while back :D, It'l take me a while to understand these things enough to figure the glomar laplacian, or perhaps the more general n-spherical.

I thought the upsidedown delta was called nabla but that doesn't seem to be recognized :?: :evil:
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Postby alkaline » Mon Jan 19, 2004 7:08 pm

yes you're right, i forgot the 1/r[sup]2[/sup] before the third term. I have fixed it above. The form that Eric Weisstein has the Laplacian is the same form that appears in my nonclassical physics book. I would assume that it is prefered because it is more compact.

As for (δ/δθ)[sup]2[/sup], I think you can write as δ[sup]2[/sup]/δθ[sup]2[/sup] by convention (i'm not really sure).
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