Laplacian Operator (𝛻·𝛻 | 𝛻·𝛻𝑓 | 𝛻² | 𝛻²𝑓 | 𝛥 | 𝛥𝑓)
- can be thought of as an extension of the second-order derivative 𝑑2𝑓/𝑑𝑥2 but for a scalar-valued function
- is defined as the divergence (𝛻·) of the gradient (𝛻𝑓)
- if 𝑓 is a twice-differentiable scalar-valued function, then the Laplacian of 𝑓 is a scalar-valued function defined by:
- explicitly, the Laplacian of 𝑓 is the sum of all the unmixed second partial derivatives in the Cartesian coordinates 𝑥𝑖: