Nonlinear Stability of Newtonian Galaxies and Stars from a Mathematical Perspective

The stability of equilibrium configurations of galaxies or stars are time honored problems in astrophysics. We present mathematical results on these problems which have in recent years been obtained by Yan Guo and the author in the context of the Vlasov-Poisson and the Euler-Poisson model. Based on a careful analysis of the minimization properties of conserved quantities--the total energy and so-called Casimir functionals--non-linear stability results are obtained for a wide class of equilibria.