TITLE: WELL-POSEDNESS OF THE FREE-SURFACE INCOMPRESSIBLE EULER EQUATIONS WITH OR WITHOUT SURFACE TENSION ABSTRACT: I'll describe a new methodology for treating free boundary problems in me- chanics, and use it to prove local-in-time well-posedness in Sobolev spaces for the free- surface incompressible 3D Euler equations with or without surface tension for arbitrary initial data, and without any irrotationality assumption on the fluid. This is a free boundary problem for the motion of an incompressible perfect liquid in vacuum, wherein the motion of the fluid interacts with the motion of the free-surface at highest-order.