|
Abstract
|
We consider energy conditions in f(R) cosmology. The main role for the discussion is played by the definition of the stress-energy tensor that can be defined in the Jordan and in the Einstein frame under a conformal transformation. The further degrees of freedom of f(R) gravity can be modeled out as a scalar field that modifies the energy-matter content and the affects the dynamics. In particular, we show that dark energy behaviors, and then generalization of EoS giving rise to accelerated (repulsive) gravity are compatible with energy conditions that, in any case, preserve causality and geodesis structure. Specifically, in the case of power-law f(R) gravity, both the EoS (i.e.w) and the specific cosmological models (given by the power m of R^m) can be combined with energy conditions. The emerging classification selects viable ranges of w and m. In particular, the accelerating/decelerating behaviors (then dark energy behaviors), the presence/absence of Big Rip singularities and other important cosmological features strictly depend on the given energy condition that have to be satisfied.
|