Linear Vs. Nonlinear PDE 1 Operators - University of Kansas
matjohn.ku.edu › Teaching › S19In the rst case, we can write the PDE in \operator form" as L(u) = 0 where L(u) = u t + u xxx + uu x: This operator is quickly seen to be nonlinear (due to the uu x term) since it fails property (ii) above. Thus, the rst PDE listed above is nonlinear. On the other hand, the second PDE can be written in operator form as L(u) = f where L(u) = u t u xx cos(xy)u and f(x;y) = xy2. Since Lis a linear operator (CHECK THIS!!), the second PDE above is a linear PDE.