Viscous Destabilization for Large Shocks of Conservation Laws

TL;DR

This paper examines the stability of shock waves in viscous conservation laws, revealing that a property known as $a$-contraction can fail for large shocks, indicating a viscous destabilization effect.

Contribution

It demonstrates that the $a$-contraction property, previously known to hold for small shocks, can fail for large shocks in viscous systems, highlighting a new destabilization phenomenon.

Findings

$a$-contraction fails for large shocks in some viscous systems.

Viscous destabilization occurs despite inviscid stability.

$a$-contraction is stronger than classical nonlinear stability.

Abstract

The recent theory of $a-$contraction with shifts provides $L^2$-stability for shock waves of $1-$D hyperbolic systems of conservation laws. The theory has been established at the inviscid level uniformly in the shock amplitude, and at the viscous level for small shocks. In this work, we investigate whether the $a-$contraction property holds uniformly in the shock amplitude for some specific systems with viscosity. We show that in some cases, the $a-$contraction fails for sufficiently large shocks. This showcases a "viscous destabilization" effect in the sense that the $a$-contraction property is verified for the inviscid model, but can fail for the viscous one. This also shows that the $a$-contraction property, even among small perturbations, is stronger than the classical notion of nonlinear stability, which is known to hold regardless of shock amplitude for viscous scalar conservation laws.