Abstract

           In this paper we give a classification of closed and  connected Lie groups, up to conjugacy in Iso(adS_3), acting by cohomogeneity one on the three dimensional anti de sitter space adS_3. Then we determine the causal character of the orbits in both cases, proper and nonproper actions. When the action is proper, we show that there is no exceptional orbit and causal characters of the principal orbits are the same.