释义 |
LaplacianThe Laplacian operator for a Scalar function is defined by
 | (1) |
in Vector notation, where the are the Scale Factorsof the coordinate system. In Tensor notation, the Laplacian is written
where is a Covariant Derivative and
 | (3) |
The finite difference form isFor a pure radial function ,
Using the Vector Derivative identity
 | (6) |
so
Therefore, for a radial Power law,
A Vector Laplacian can also be defined for a Vector A by
 | (9) |
in vector notation. In tensor notation, A is written , and the identity becomes
Similarly, a Tensor Laplacian can be given by
 | (11) |
An identity satisfied by the Laplacian is
 | (12) |
where is the Hilbert-Schmidt Norm, is a row Vector, and is theMatrix Transpose of A.
To compute the Laplacian of the inverse distance function , where , and integrate theLaplacian over a volume,
 | (13) |
This is equal to
where the integration is over a small Sphere of Radius . Now, for and , the integralbecomes 0. Similarly, for and , the integral becomes . Therefore,
 | (15) |
where is the Delta Function.See also Antilaplacian
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