Uniqueness of complete maximal hypersurfaces in spatially open   $(n+1)$-dimensional Robertson-Walker spacetimes with flat fiber
  In this paper, under natural geometric and physical assumptions we provide new uniqueness and non-existence results for complete maximal hypersurfaces in spatially open Robertson-Walker spacetimes whose fiber is flat. Moreover, our results are applied to relevant spacetimes as the steady state spacetime, Einstein-de Sitter spacetime and radiation models. 
Jos\'e A. S. Pelegr\'in, Alfonso Romero and Rafael M. Rubio
math.DG math-ph math.MP