On the regularity of the solution map of the Euler-Poisson system

In this paper we consider the Euler-Poisson system (describing a plasma consisting of positive ions with a negligible temperature and massless electrons in thermodynamical equilibrium) on the Sobolev spaces H-s(R-3) , s > 5/2. Using a geometric approach we show that for any time T > 0 the corresponding solution map, (rho(0), u(0)) bar right arrow (rho(T), u(T)) , is nowhere locally uniformly continuous. On the other hand it turns out that the trajectories of the ions are analytic curves in R-3.