On the Monge-Ampère equation

where Ω ⊂ R is some open set, u : Ω → R is a convex function, and the function f : Ω× R× R → R is given. In other words, the Monge-Ampère equation prescribes the product of the eigenvalues of the Hessian of u, in contrast with the “model” elliptic equation ∆u = f which prescribes their sum. As we shall explain later, the convexity of the solution u is a necessary condition to make the equation degenerate elliptic, and therefore to hope for regularity results. The goal of this note is to give first a general overview of the classical theory, and then discuss some recent important developments on this beautiful topic. For our presentation of the classical theory, we follow the survey paper [25].