Two-dimensional Riemann problem for a single conservation law

Abstract:

The entropy solutions to the partial differential equation \[ (\partial /\partial t)u(t,x,y) + (\partial /\partial x)f(u(t,x,y)) + (\partial /\partial y)g(u(t,x,y)) = 0,\] with initial data constant in each quadrant of the $(x,y)$ plane, have been constructed and are piecewise smooth under the condition $f''(u) \ne 0, g''(u) \ne 0, (f''(u)/g''(u))\prime \ne 0$. This problem generalizes to several space dimensions the important Riemann problem for equations in one-space dimension. Although existence and uniqueness of solutions are well known, little is known about the qualitative behavior of solutions. It is this with which we are concerned here.