Hi, I used NDEigensystem to find eigenfunctions of an operator as shown below.
{vals, funs} =
NDEigensystem[{-\[Pi] D[g[x], {x, 2}] - 0.05Cos[x] g[x] ,
DirichletCondition[g[x] == 0, True]}, g[x], {x, -\[Pi], \[Pi]}, 4]
I then used one of the eigenfunctions obtained from here as an initial condition in a differential equation as shown below
NDSolve[{I D[f[x, t], t] == -D[f[x, t], {x, 2}]/2 -
0.05 (1 + Cos[t]) Cos[x] f[x, t],
f[x, 0] == funs[[2]][x]}, f, {x, -\[Pi], \[Pi]}, {t, 0, 2 \[Pi]}]
But I keep getting the error
NDSolve::mxsst
There are no problems in using the eigenfunction for plots etc. Also when I use a different initial condition I get back a reasonable solution. Only when I use the eigenfunction as an initial condition for this do I get a problem. Can someone help with this please?