I. Ayuso, J. A. R. Cembranos
We compute the spectrum, mixing and interaction structure of scalar models with a general coupling to the scalar curvature. As it is well known the perturbative states of these theories are given by two massive spin-0 modes in addition to one massless spin-2 state. This latter mode can be identified with the standard graviton field. Indeed, it is possible to define an Einstein frame, where the dynamics of the massless spin-2 graviton is the one associated with the Einstein-Hilbert action. We explore systematically the interactions of all these degrees of freedom in the mentioned frame, since part of the coupling structure can be anticipated by geometrical arguments.
General Relativity and Quantum Cosmology
Physical Review D
Volume 101, Issue 0440, Page 12