On Hydrodynamic Equations at the Limit of Infinitely Many Molecules

We show that weak convergence of point measures and $(2+\epsilon)$-moment conditions imply hydrodynamic equations at the limit of infinitely many interacting molecules. The conditions are satisfied whenever the solutions of the classical equations for $N$ interacting molecules obey uniform in $N$ bounds. As an example, we show that this holds when the initial conditions are bounded and that the molecule interaction, a certain $N$-rescaling of potentials that include all $r^{-p}$ for $1<p$, is weak enough at the initial time. In this case the hydrodynamic equations coincide with the macroscopic equations of Maxwell.