On higher derivative gravity, c-theorems and cosmology

Understand

We consider higher derivative gravity lagrangians in 3 and 4 dimensions, which admit simple c-theorems, including upto six derivative curvature invariants.

• Following a suggestion by Myers, these lagrangians are restricted such that the fluctuations around (anti) de Sitter spaces have second order linearized equations of motion.
• We study c-theorems both in the context of AdS/CFT and cosmology.
• In the context of cosmology, the monotonic function is the entropy defined on the apparent horizon through Wald's formula.