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math.DS2006
Actions of noncompact semisimple groups on Lorentz manifolds
Mohamed Deffaf, Karin Melnick, Abdelghani Zeghib
The above title is the same, but with "semisimple" instead of "simple," as that of a notice by N. Kowalsky. There, she announced many theorems on the subject of actions of simple L…
math.DS2004
On Lorentz dynamics : From group actions to warped products via homogeneous spaces
Abdelouahab Arouche, Mohamed Deffaf, Abdelghani Zeghib
We show a geometric rigidity of isometric actions of non compact (semisimple) Lie groups on Lorentz manifolds. Namely, we show that the manifold has a warped product structure of a…