Colloquium

We prove that the 3-D free-surface Euler equations with regular initial geometries and velocity fields have solutions which can form a finite-time "splash" (or "splat") singularity, wherein the evolving 2-D hypersurface, the moving boundary of the fluid domain, self-intersects at a point (or on a surface). Such singularities can occur when the crest of a breaking wave falls unto its trough, or in the study of drop impact upon liquid surfaces. Our approach is founded upon the Lagrangian description of the free-boundary problem, combined with a novel approximation scheme of a finite collection of local coordinate charts; as such we are able to analyze a rather general set of geometries for the evolving 2-D free-surface of the fluid. We do not assume the fluid is irrotational, and as such, our method can be used for a number of other fluid interface problems, including compressible flows, plasmas, as well as the inclusion of surface tension effects. This is joint work with D. Coutand.