Totally umbilic null hypersurfaces in generalized Robertson-Walker spaces

摘要

We show that there is a correspondence between totally umbilic null hypersurfaces in generalized Robertson Walker spaces and twisted decompositions of the fibre. This allows us to prove that nullcones are the unique totally umbilic null hypersurfaces in the closed Friedmann Cosmological model. We also apply this kind of ideas to static spaces, in particular to Reissner-Nordstrom and Schwarzschild exterior spacetimes. (C) 2015 Elsevier B.V. All rights reserved.