1305.4754 (Tomi S. Koivisto et al.)

Novel aspects of C-theories in Cosmology    [PDF]

Tomi S. Koivisto, David F. Mota, Marit Sandstad

The field equations in FRW background for the so called C-theories are presented and investigated. In these theories the usual Ricci scalar is substituted with $f(\mathcal{R})$ where $\mathcal{R}$ is a Ricci scalar related to a conformally scaled metric $\hat{g}_{\mu\nu} = \mathcal{C}(\mathcal{R})g_{\mu\nu}$, where the conformal factor itself depends on $\mathcal{R}$. It is shown that homogeneous perturbations of this Ricci scalar around general relativity FRW background of a large class of these theories are either inconsistent or unstable.

View original: http://arxiv.org/abs/1305.4754