Initial data for fluid bodies in general relativity
  We show that there exist asymptotically flat almost-smooth initial data for Einstein-perfect fluid's equation that represent an isolated liquid-type body. By liquid-type body we mean that the fluid energy density has compact support and takes a strictly positive constant value at its boundary. By almost-smooth we mean that all initial data fields are smooth everywhere on the initial hypersurface except at the body boundary, where tangential derivatives of any order are continuous at that boundary.   PACS: 04.20.Ex, 04.40.Nr, 02.30.Jr 
Sergio Dain and Gabriel Nagy