Outgoing-energy identity for a radial defocusing wave
= Outgoing-energy identity for a radial defocusing wave
For $q=w_t+w_r$ and a radial weight $\psi$,
$$
\frac d{dt}\int_0^\infty\psi\left(\frac12q^2+\frac{|w|^{p+1}}{(p+1)r^{p-1}}\right)dr
=-\frac12\int_0^\infty\psi'q^2dr
+\frac1{p+1}\int_0^\infty\frac{|w|^{p+1}}{r^{p-1}}
\left(\psi'-(p-1)\frac\psi r\right)dr.
$$