Editing Laplace operator (section)

===Use in physics===
An example of the usage of the vector Laplacian is the [[Navier-Stokes equations]] for a [[Newtonian fluid|Newtonian]] [[incompressible flow]]:
<math display="block">\rho \left(\frac{\partial \mathbf{v}}{\partial t}+ ( \mathbf{v} \cdot \nabla ) \mathbf{v}\right)=\rho \mathbf{f}-\nabla p +\mu\left(\nabla ^2 \mathbf{v}\right),</math>
where the term with the vector Laplacian of the [[velocity]] field <math>\mu\left(\nabla ^2 \mathbf{v}\right)</math> represents the [[viscosity|viscous]] [[Stress (physics)|stress]]es in the fluid.

Another example is the wave equation for the electric field that can be derived from [[Maxwell's equations]] in the absence of charges and currents:
<math display="block">\nabla^2 \mathbf{E} - \mu_0 \epsilon_0 \frac{\partial^2 \mathbf{E}}{\partial t^2} = 0.</math>

This equation can also be written as:
<math display="block">\Box\, \mathbf{E} = 0,</math>
where <math display="block">\Box\equiv\frac{1}{c^2} \frac{\partial^2}{\partial t^2}-\nabla^2,</math> is the [[D'Alembertian]], used in the [[Klein–Gordon equation]].