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Decay estimates of solutions to the compressible Euler-Maxwell system in R3

We study the large time behavior of solutions near a constant equilibrium to the compressible Euler-Maxwell system in $\r3$. We first refine a global existence theorem by assuming that the $H^3$ norm of the initial data is small, but the higher order derivatives can be arbitrarily large. If the initial data belongs to $\Dot{H}^{-s}$ ($0\le s<3/2$) or $\dot{B}_{2,\infty}^{-s}$ ($0<s\le3/2$), by a regularity interpolation trick, we obtain the various decay rates of the solution and its higher order derivatives. As an immediate byproduct, the usual $L^p$--$L^2$ $(1\le p\le 2)$ type of the decay rates follow without requiring that the $L^p$ norm of initial data is small.