Would an alternative gravity theory developed from an improved gravitational action approach includes negative kinetic energy dynamic degrees of freedom?

The observed unexpected accelerating expansion of the universe, by Riess and his collaborators in 1998, has become one of the most important problems of the contemporary physics. A considerable effort has been spent by theoretical physicists to explain this observation for a while. When one looks at these attempts more closely, two of approaches attract attention: (i) Multi-dimensional alternative gravity models, (ii) Approaches which takes the more general and complex action than it is original Einstein-Hilbert form, which had been given as Ricci scalar R. The second type of these approaches must be examined carefully, because they could be generically involved dynamical degrees of freedom which possess negative kinetic energy (shortly called as 'ghost states' or simply 'ghosts'). In this work, an alternative theory has been studied to understand if it contains ghosts or not. This alternative approach belongs to the second type of the approaches which mentioned above, and it is given as: Sgravity=∫d4x-gf(R,RμνRμλνρRλρ) where Stotal=Sgravity+Smatter. And this model has been examined by this way to see if this specific alternative model could be used to explain the present time acceleration of the universe or not.