Stationary wave map
= Stationary wave map
{title2=$\Delta Q+|\nabla Q|^2Q=0$}
A time-independent <wave map> is a <harmonic map> of its spatial domain into the target. For target $S^2$, its equation is $\Delta Q+|\nabla Q|^2Q=0$. In two dimensions inverse <stereographic projection> gives a smooth nonconstant example of finite <wave map energy> $4\pi$.