Consistent Nonlinear Interactions for the Graviton

Abstract: This thesis investigates various aspects of massive gravity and bimetric gravity which be- long to a certain class of modifications of general relativity. It provides an introduction to linear massive gravity in flat backgrounds, before reviewing the construction of consistent nonlinear massive gravity that avoids the Boulware-Deser ghost instability. We discuss the structure of the ghost-free action and summarize the consistency proofs for massive gravity in arbitrary backgrounds, using two different formulations. Thereafter we reca- pitulate the generalization of massive gravity to consistent bimetric models of gravity, in which we then solve the equations of motion with a homogeneous, isotropic ansatz and discuss implications for cosmology.