Spectra, vacua and the unitarity of Lovelock gravity in D-dimensional   AdS spacetimes
  We explicitly confirm the expectation that generic Lovelock gravity in D dimensions has a unitary massless spin-2 excitation around any one of its constant curvature vacua just like the cosmological Einstein gravity. The propagator of the theory reduces to that of Einstein's gravity, but scattering amplitudes must be computed with an effective Newton's constant which we provide. Tree-level unitarity imposes a single constraint on the parameters of the theory yielding a wide range of unitary region. As an example, we explicitly work out the details of the cubic Lovelock theory. 
Tahsin Cagri Sisman, Ibrahim Gullu, Bayram Tekin
hep-th gr-qc