= Orientation interval for transient energy growth
{title2=$\rho^\pm=2R(1\pm\sqrt{1-R^{-2}})$}
For $L=\begin{pmatrix}-1/R&1\\0&-1/(4R)\end{pmatrix}$ and $R>1$, write $\rho=x_2/x_1$. The energy derivative is $x_1^2[-1/R+\rho-\rho^2/(4R)]$, positive exactly between the displayed orientations. Linear trajectories cross the sector from $\rho^+$ to $\rho^-$ because $\dot\rho=\rho[3/(4R)-\rho]$. An <energy-neutral rotational nonlinearity> can reverse the crossing direction; the growth sector itself remains the same.
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