English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In this paper we calculate the field equations for Scalar-Tensor from avariational principle, in which we have taken into account theGibbons-York-Hawking type boundary term. We do the same for the theories$f(R)$, following, Guarnizo et al. Then, we review the equivalences betweenboth theories in the metric formalism. Thus, starting from the perturbationsunder conformal-Newtonian gauge for Scalar-Tensor theories, we find theperturbations for $f(R)$ gravity under the equivalences in the same gauge.Working with two specific models of $f(R)$, we explore the equivalences betweenthe theories. Further, we show the perturbations for both theories under thesub-horizon approach. Finally, we show how to calculate the cosmologicalperturbations using the package xPand.

Equivalence between Scalar-Tensor theories and $f(R)$-gravity: From the action to Cosmological Perturbations