Eigenvalues: k1=2, k2=1
Phase shifts: c1=2, c2=1

u=u1+u2 (decay decomposition)

Below is a combined plot of -u(x,t) (in black and only visible for a couple of frames due to overlap),
the first decay function -u1(x,t) (in red), and the second decay function -u2(x,t) (in blue) versus x.

time steps: t=-0.6,-0.5,...,0.8