Extend sequential transversality beyond strictly hyperbolic genuinely nonlinear systems

Extend the sequential-transversality framework to hyperbolic conservation-law regimes that violate genuine nonlinearity or strict hyperbolicity, including composite waves, contact discontinuities, coinciding or crossing characteristic speeds, and the corresponding adapted admissibility criteria.

Background

The paper’s main structural-stability and genericity results assume strict hyperbolicity and genuine nonlinearity, thereby restricting the analysis to classical Lax shocks and rarefactions. The authors explicitly identify extension to non-convex systems with composite waves and to systems with coinciding or crossing characteristic speeds as an unresolved direction. Such an extension would require replacing the present Lax-wave formulation with admissibility criteria appropriate to the additional wave types.

References

Several directions remain open. Our analysis operates under Assumptions~\ref{ass:SH} (strict hyperbolicity) and~\ref{ass:GN} (genuine nonlinearity), which together restrict attention to classical Lax shocks and rarefactions and exclude composite waves and contact discontinuities. Relaxing Assumption~\ref{ass:GN} admits strictly hyperbolic systems with non-convex flux, such as the van der Waals $p$-system in the supercritical regime, whose inflection points generate composite waves, while relaxing Assumption~\ref{ass:SH} opens the door to systems with coinciding or crossing characteristic speeds. Extending the sequential-transversality framework to these regimes, with admissibility criteria adapted to each wave type, is a natural next step.

— Generic Structural Stability for Riemann Solutions to $n \times n$ Systems of Hyperbolic Conservation Laws  (2609.28714 - Tan et al., 23 Sep 2026) in Section 5, Conclusion and Future Work