Isotropisation of Quadratic Gravity: Scalar and Tensor Components
  It is believed that soon after the Planck era, spacetime should have a
semi-classical nature. Therefore, it is unavoidable to modify the theory of
General Relativity or look for alternative theories of gravitation. An
interesting possibility found in the literature considers two geometric
counter-terms to regularize the divergences of the effective action. These
counter-terms are responsible for a higher order derivative metric theory of
gravitation. In the present letter we investigate how isotropisation occurs.
For this reason a single solution is chosen throughout this article. We obtain
perturbatively, by two different methods, that the tensor and scalar components
emerge naturally during the isotropisation process. In this sense our result
provides a numerical example to Stelle's well known result on classical gravity
with higher derivates. Our entire analysis is restricted to the particular
Bianchi type $I$ case.
