f(Lovelock) theories of gravity

Understand

f(Lovelock) gravities are simple generalizations of the usual f(R) and Lovelock theories in which the gravitational action depends on some arbitrary function of the corresponding dimensionally-extended Euler densities.

• In this paper we study several aspects of these theories in general dimensions.
• We start by identifying the generalized boundary term which makes the gravitational variational problem well-posed.
• Then, we show that these theories are equivalent to certain scalar-tensor theories and how this relation is characterized by the Hessian of f.