I'm having a very simple problem which probably has an equally simple answer. I'm following the wikipedia article: https://en.wikipedia.org/wiki/Landau_quantization
We have a uniform magnetic field in $\hat{z}$-direction $$\mathbf{B}=(0,0,B).$$ The vector potential must fulfill $\nabla\times \mathbf{A}=\mathbf{B}$ and supposedly valid choice is given by the Landau gauge for which the vector potential is $$\mathbf{A}=(0,Bx,0).$$
However I find that with this choice for $\mathbf{A}$ the magnetic field becomes $$\mathbf{B}=(-Bx\partial_z,0,\partial_x(Bx))=(-Bx\partial_z,0,B).$$ Why would the first component vanish?
Or is there something which I have misunderstood completely?
EDIT: Jesus Christ, this is embarrassing. Clearly $$\nabla\times \mathbf{A}=(-\partial_z(Bx),0,\partial_x(Bx))\neq (-Bx\partial_z,0,\partial_x(Bx)).$$ This solves the problem.