I have the next drift-diffusion equation:

where D(z) is a matrice.

To solve this equation i perform the next change of variable: and then I apply the Fourier transformation and when I solve this integrals with maple, at the first integral maple said that it is undefined.

Maybe I can solve the problem applying other change of variable or taking into account in the change of variable like for example or maybe I should replace also in the change of variable (I replace only in ). I am not sure if I can doing this options. Some one can help me?