Hi guys,

sorry for my late reply. Indeed, I made a sign error in the derivation of the PDE system. Thank you very much, Markiyan & Preben! After fixing this one, adjusting some parementers and switching from Direchlet to von Neumann boundary conditions, I get to the following system of PDEs:

with(PDEtools);

delta := 0.1;

#Definition of the initial condition f(x)
g := x-> exp(  - 1/(   1 - ( (x-0.5)/(0.5-delta) )^2 )  );
f := x -> piecewise(x<=delta, 0, delta < x and x < 1-delta, g(x), x>=1-delta, 0);

#Definition of the PDE system
PDE1 := diff(a(x,t),t) = - 2*a(x,t) + 1*b(x,t) + 0.01*( diff(a(x,t),x,x) + a(x,t)*diff(b(x,t),x,x) - b(x,t)*diff(a(x,t),x,x) );

PDE2 := diff(b(x,t),t) = - 1*b(x,t) + 2*a(x,t) + 0.01*( diff(b(x,t),x,x) - a(x,t)*diff(b(x,t),x,x) + b(x,t)*diff(a(x,t),x,x) );

CON := [ a(x,0)=f(x), b(x,0)=0, D[1](a)(0,t) = 0, D[1](a)(1,t) = 0, D[1](b)(0,t) = 0, D[1](b)(1,t) = 0];

SOL:=pdsolve([PDE1,PDE2],CON,numeric,time=t,range=0..1,spacestep=0.01,timestep=0.01);

Unfortunately, calling

SOL:-plot3d(x=0..1,t=0..15,axes=normal);

seems to give just a(x,t). How can I tell Maple to plot b(x,t)? Or which manipulations have I apply to the return value SOL to extract b(x,t)? It would be great, if some one could tell me this ... (sorry if the question is stupid/trivial, but I am new to Maple...).

Greetings,

Herold