Scalar-Vector-Tensor Gravity Theories

Understand

We construct the consistent ghost-free covariant scalar-vector-tensor gravity theories with second order equations of motion with derivative interactions.

• We impose locality, unitarity, Lorentz invariance and pseudo-Riemannian geometry as the fundamental terms.
• In the tensor sector we require diffeomorphism invariance, whereas we allow the vector sector to be gauge invariant or not.
• The resulting Lagrangians consist of new genuine couplings among these fields with at most two derivatives per field.