A new approach to cosmological perturbations in f(R) models

TL;DR

This paper introduces an analytic method to quantify deviations in cosmological perturbations between f(R) gravity models and LCDM, covering large to small scales without the quasi-static approximation.

Contribution

It presents a general analytic procedure for studying linear cosmological perturbations in f(R) models beyond the quasi-static approximation.

Findings

Quantifies deviations in perturbation behavior between f(R) models and LCDM.

Applicable to scales from the Hubble horizon to sub-Hubble scales.

Method is extendable to higher-order perturbations.

Abstract

We propose an analytic procedure that allows to determine quantitatively the deviation in the behavior of cosmological perturbations between a given f(R) modified gravity model and a LCDM reference model. Our method allows to study structure formation in these models from the largest scales, of the order of the Hubble horizon, down to scales deeply inside the Hubble radius, without employing the so-called "quasi-static" approximation. Although we restrict our analysis here to linear perturbations, our technique is completely general and can be extended to any perturbative order.