Four-dimensional homogeneous semi-symmetric Lorentzian manifolds
  We give a complete description of semi-symmetric algebraic curvature tensors on a four-dimensional Lorentzian vector space and we use this description to determine all four-dimensional homogeneous semi-symmetric Lorentzian manifolds. 
Abderazak Benroumane, Mohamed Boucetta, Aziz Ikemakhen
math.DG