On the Limit as the Density Ratio Tends to Zero for Two Perfect Incompressible Fluids Separated by a Surface of Discontinuity

We study the asymptotic limit as the density ratio ρ−/ρ+ → 0, where ρ+ and ρ− are the densities of two perfect incompressible 2-D/3-D fluids, separated by a surface of discontinuity along which the pressure jump is proportional to the mean curvature of the moving surface. Mathematically, the fluid motion is governed by the two-phase incompressible Euler equations with vortex sheet data. By rescaling, we assume the density ρ+ of the inner fluid is fixed, while the density ρ− of the outer fluid is set to . We prove that solutions of the free-boundary Euler equations in vacuum are obtained in the limit as → 0.