On the connectedness of the space of initial data for the Einstein equations.
On the geometry of null cones in Einstein-vacuum spacetimes
On the quadric CMC spacelike hypersurfaces in Lorentzian space forms
We deal with complete spacelike hypersurfaces immersed with constant mean curvature in a Lorentzian space form. Under the assumption that the support functions with respect to a fixed nonzero vector are linearly related, we prove that such a hypersurface must be either totally umbilical or isometric to a hyperbolic cylinder of the ambient space.
Onde di discontinuità gravitazionali in relatività generale