general relativity

cosmological constant

perfect fluid

cosmological models

space times

sitter space

International Journal of Geometric Methods in Modern Physics

We show that an [Formula: see text]-dimensional generalized Robertson–Walker (GRW) space-time with divergence-free conformal curvature tensor exhibits a perfect fluid stress–energy tensor for any [Formula: see text] gravity model. Furthermore, we prove that a conformally flat GRW space-time is still a perfect fluid in both [Formula: see text] and quadratic gravity where other curvature invariants are considered.

Cosmological perfect-fluids in f(R) gravity