On symmetries of generalized Robertson-Walker Space-times and   applications
  The purpose of the present article is to study and characterize sev- eral types of symmetries of generalized Robertson-Walker space-times. Con- formal vector fields, curvature and Ricci collineations are studied. Many im- plications for existence of these symmetries on generalied Robertson-Walker spacetimes are obtained. Finally, Ricci solitons on generalized Robertson- Walker space-times admitting conformal vector fields are investigated. 
H. K. El-Sayied, S. Shenawy and N. Syied
math.DG