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arXiv · 2411.13444

Conservation Laws with Discontinuous Gradient-Dependent Flux: the Unstable Case

Debora Amadori·Alberto Bressan·Wen Shen
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Abstract

The paper is concerned with a scalar conservation law with discontinuous gradient-dependent flux. Namely, the flux is described by two different functions $f(u)$ or $g(u)$, when the gradient $u_x$ of the solution is positive or negative, respectively. We study here the unstable case where $f(u)>g(u)$ for all $u\in {\mathbb R}$. Assuming that both $f$ and $g$ are strictly convex, solutions to the Riemann problem are constructed. Even for a smooth initial data, examples show that the Cauchy problem can have infinitely many solutions. For an initial data which is piecewise monotone, i.e., increasing or decreasing on a finite number of intervals, a solution can be constructed globally in time. It is proved that such solution is unique under the additional requirement that the number of interfaces, where the flux switches between $f$ and $g$, remains as small as possible.

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Debora Amadori, Alberto Bressan, Wen Shen. 2026-01-23. Conservation Laws with Discontinuous Gradient-Dependent Flux: the Unstable Case. https://doi.org/10.4310/cms.260715020746

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