Non-minimal scalar-tensor theories
  We compute the spectrum of scalar models with a general coupling to the scalar curvature. We find that 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, we are able to define an Einstein frame, where the dynamics of the massless spin-2 graviton is the one associated with the Einstein-Hilbert action. We also explore the interactions of all these degrees of freedom in the mentioned frame, since part of the coupling structure can be anticipated by geometrical arguments. 
Ismael Ayuso (Madrid U.) and Jose A. R. Cembranos (Madrid U. & Colima   U. & Dual C-P Inst. High Energy Phys.)
gr-qc