z-dispersive

See KL for details. Here, it is proposed, and experimentally corroborated, that shocks will travel stably when:

\(\begin{align} S_{\text{eff}}^{(R)}>c_h(\sigma_r):=\left( \int_\Omega\left( \frac{\sigma_r^\prime (x)}{\rho(x)} \right)^{-1/2} dx \right)^{-1}, \end{align} \)