Cosmological perfect fluids in higher-order gravity (Q2179691)

The authors discuss higher-order gravity for a FRW spacetime with perfect fluid source. It is shown that cosmography can be an efficient tool to discriminate among concurring models.They rigorously demonstrate that, in the specific case of higher-order gravity, further terms entering the Hilbert-Einstein action can be dealt with the standard of perfect fluid, in the cosmological context of GRW metrics. Besides the mathematical result, the approach is interesting because it allows to point out the fundamental origin of scalar fields entering at early times (through inflation) and at late times (through dark energy) into the cosmological evolution.