Reconstruction and exact solutions for cosmological perturbations from a generalized gravity theory

TL;DR

This paper derives exact solutions for scalar and tensor cosmological perturbations within a generalized gravity framework during inflation, reconstructs background variables, and constrains models using Planck 2018 data.

Contribution

It provides analytical solutions and background reconstruction for cosmological perturbations in generalized gravity, extending previous models with new ansatze and observational constraints.

Findings

Exact solutions for perturbations obtained

Background variables reconstructed analytically

Models constrained by Planck 2018 data

Abstract

Scalar and tensor cosmological perturbations during an inflationary universe scenario in the context of the a generalized gravity theory are studied. This analyze is carried out considering an ansatz on the variables associated to scalar and tensor perturbation ($z_s$ and $z_t$) in the Jordan frame. In this context, we analyze two different Ansatze for the ratio $z_s/z_t$, and we study in great detail the analytical and exact solutions for the cosmological perturbations together with the corresponding reconstruction of the background variables. Recent observational data from the Planck 2018 results are employed to constrain the parameters of each of the models.