Formula_699

\[\operatorname{det}\left(\begin{array}{cc}\partial \omega / \partial I & \omega \\\omega & 0\end{array}\right)=\operatorname{det}\left(\begin{array}{cc}\partial^{2} H / \partial I^{2} & \partial H / \partial I \\\partial H / \partial I & 0\end{array}\right) \neq 0 .\]