On Vacuum Free Boundary Problem of the Spherically Symmetric Euler Equations with Damping and Solid Core

Abstract: In this paper, the global existence of smooth solution and the long-time asymptotic stability of the equilibrium to vacuum free boundary problem of the spherically symmetric Euler equations with damping and solid core have been obtained for arbitrary finite positive gas constant $A$ in the state equation $p=A \rho^\gamma$ with $p$ being the pressure and $\rho$ the density, provided that $\gamma>4/3,$ initial perturbation is small and the radius of the equilibrium $R$ is suitably larger than the radius of the solid core $r_0$. Moreover, we obtain the pointwise convergence from the smooth solution to the equilibrium in a surprisingly exponential time-decay rate. The proof is mainly based on weighted energy method in Lagrangian coordinate.