Definition:Heat Equation

Equation
The heat equation is a second order PDE of the form:
 * $$a^2 \left({\frac {\partial^2 w} {\partial x^2} + \frac {\partial^2 w} {\partial y^2} + \frac {\partial^2 w} {\partial z^2}}\right) = \frac{\partial{w}}{\partial{t}}$$