2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/229859We prove the existence of a large class of dynamical solutions to the Einstein-Euler equations that have a first post-Newtonian expansion. The results here are based on the elliptic-hyperbolic formulation of the Einstein-Euler equations used in \cite{Oli06}, which contains a singular parameter $\ep = v_T/c$, where $v_T$ is a characteristic velocity associated with the fluid and $c$ is the speed of light. As in \cite{Oli06}, energy estimates on weighted Sobolev spaces are used to analyze the behavior of solutions to the Einstein-Euler equations in the limit $\ep\searrow 0$, and to demonstrate the validity of the first post-Newtonian expansion as an approximation.General Relativity and Quantum Cosmologytext