Generalized Robertson-Walker space times, a survey
  Generalized Robertson-Walker spacetimes extend the notion of Robertson-Walker spacetimes, by allowing for spatial non-homogeneity. A survey is presented, with main focus on Chen's characterization in terms of a timelike concircular vector. Together with their most important properties, some new results are presented. 
Carlo Alberto Mantica and Luca Guido Molinari
math-ph gr-qc math.MP