Solution
= Solution
For $\phi(x)=|x|^2-1$, the conormal on the unit sphere is $d\phi=(0,2x)$. Hence
$$
p(d\phi)=4|x|^2=4
$$
on the sphere. It is non-characteristic at every point.
= Solution
For $\phi(x)=|x|^2-1$, the conormal on the unit sphere is $d\phi=(0,2x)$. Hence
$$
p(d\phi)=4|x|^2=4
$$
on the sphere. It is non-characteristic at every point.