Non-reductive Homogeneous Pseudo-Riemannian Manifolds of Dimension Four
Non-reductive Homogeneous Pseudo-Riemannian Manifolds of Dimension Four
Abstract A method, due to Élie Cartan, is used to give an algebraic classification of the non-reductive homogeneous pseudo-Riemannian manifolds of dimension four. Only one case with Lorentz signature can be Einstein without having constant curvature, and two cases with (2, 2) signature are Einstein of which one is Ricci-flat. …