I want to solve a 2D-PDE that has the form
NDSolve[{D[u[t, x], t] ==
D[(u[t, x]*(u[t, x]^2 - u0^2) - D[u[t, x], x, x]), x, x],
u[0, x] == 0,
u[t, 0] == 0,
u[t, 5] == 0}, u, {t, 0, 10}, {x, 0, 5}];
However, I would like to have periodic boundary conditions, how do I specify these?