Equivalence between Scalar-Tensor theories and f(R)-gravity: from the action to cosmological perturbations. (14th May 2020)

• Record Type: Journal Article
• Authors: Velásquez, Joel; Castañeda, Leonardo
• Is Part Of: Journal of physics communications. Volume 4:Number 5(2020)
• Publication Date: 2020-05-14
• Subjects: modifed gravity -- cosmological perturbations -- sub-horizon approach; Physics -- Periodicals; 530.05
• DOI: 10.1088/2399-6528/ab902f
• Languages: English
• ISSNs: 2399-6528

Abstract

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.