Equivalence between Scalar-Tensor theories and f(R)-gravity: from the action to cosmological perturbations
Abstract
In this paper we calculate the field equations for Scalar-Tensor from a variational principle, taking into account the Gibbons-York-Hawking type boundary term. We do the same for the theories f(R), following (Guarnizo (2010), Gen. Rel. Grav. 42, 2713-2728). Then, we review the equivalences between both theories in the metric formalism. Thus, starting from the perturbations for Scalar-Tensor theories, we find the perturbations for f(R) gravity under the equivalences. Working with two specific models of f(R), we explore the equivalences between the theories under conformal-Newtonian gauge. Further, we show the perturbations for both theories under the sub-horizon approach.
- Publication:
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Journal of Physics Communications
- Pub Date:
- May 2020
- DOI:
- 10.1088/2399-6528/ab902f
- Bibcode:
- 2020JPhCo...4e5007V
- Keywords:
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- modifed gravity;
- cosmological perturbations;
- sub-horizon approach