Perfect fluid spacetimes with harmonic generalized curvature tensor

We show that n-dimensional perfect fluid spacetimes with divergence-free conformal curvature tensor and constant scalar curvature are generalized RobertsonWalker (GRW) spacetimes; as a consequence a perfect fluid Yang pure space is a GRW spacetime. We also prove that perfect fluid spacetimes with harmonic generalized curvature tensor are, under certain conditions, GRW spacetimes. As particular cases, perfect fluids with divergence-free projective, concircular, conharmonic or quasi-conformal curvature tensor are GRW spacetimes. Finally, we explore some physical consequences of such results.