The topic of this talk is the dependence of admissible solutions to hyperbolic conservation laws on physical parameters. I will outline an effective approach that we developed for establishing L¹ estimates between solutions to hyperbolic conservation laws with different flux functions and discuss how solutions of the classical and relativistic Euler equations depend on physical parameters such as the adiabatic constant, the Mach number and the speed of light.

The results presented are obtained jointly with Gui-Qiang Chen and Yongqian Zhang.