Gauge Issues in Extended Gravity and f(R) Cosmology

TL;DR

This paper investigates how conformal transformations between Einstein and Jordan frames in f(R) cosmology affect gauge choices, highlighting potential inconsistencies and their implications for numerical calculations.

Contribution

It identifies gauge restrictions necessary for consistent conformal mappings in f(R) cosmology and clarifies which gauges are suitable for such transformations.

Findings

Newtonian gauge remains consistent under conformal mapping.

Synchronous gauge can lead to inconsistencies if not properly handled.

Incorrect gauge choices may contaminate numerical results in f(R) cosmology.

Abstract

We consider issues related to the conformal mapping between the Einstein and Jordan frames in f(R) cosmology. We consider the impact of the conformal transformation on the gauge of a perturbed system and show that unless the system is written in a restricted set of gauges the mapping could produce an inconsistent result in the target frame. Newtonian gauge lies within the restricted group but synchronous gauge does not. If this is not treated carefully it could in principle contaminate numerical calculations.