In this work we study how nonminimally coupled theories of gravity modify the usual Friedmann equation, and develop two methods to treat these. The ambiguity in the form of the Lagrangian density of a perfect fluid is emphasized, and the impact of different dominant matter species is assessed. The cosmological constant problem is also discussed.

• Received 21 November 2013

DOI:https://doi.org/10.1103/PhysRevD.89.044012