拉普拉斯算子

Laplace operator Laplacian
是 n 维Euclidean空间中的一个二阶微分算子，定义为梯度（▽f）的散度（▽·f）
$D i v (G r a d (f))$

\begin{aligned} \nabla & = \frac{\partial}{\partial x} i + \frac{\partial}{\partial y} j + \frac{\partial}{\partial z} k \\ Δ & = \nabla^{2} = \nabla \cdot \nabla \\ = \frac{\partial^{2}}{\partial x^{2}} + \frac{\partial^{2}}{\partial y^{2}} + \frac{\partial^{2}}{\partial z^{2}} \end{aligned}