Cohomogeneity one actions on anti de Sitter spacetimes
  In this paper we classify, up to orbit equivalence, cohomogeneity one actions of connected closed Lie subgroups of $U(1,n)$ on the $(2n+1)$-dimensional anti de Sitter spacetime $AdS^{2n+1}$. We also give some new examples of nonproper cohomogeneity one actions on $AdS^{n+1}$ and determine parabolic Lie subgroups of $SO(2,n)$ and their orbits in $AdS^{n+1}$ 
J.C. Diaz-Ramos, S.M.B. Kashani, M.J. Vanaei
math.DG