Assessing the viability of successful reconstruction of the dynamics of dark energy using varying fundamental couplings

TL;DR

This paper investigates whether the evolution of dark energy can be accurately reconstructed from variations in fundamental constants, revealing that such reconstructions are generally ambiguous without additional model assumptions.

Contribution

It demonstrates that the same dark energy evolution can correspond to different fundamental coupling variations, highlighting limitations of linear coupling assumptions.

Findings

Reconstruction ambiguity exists between dark energy evolution and fundamental couplings.

Redefining the scalar field can mimic standard quintessence dynamics.

Linear coupling assumptions are insufficient for unique dark energy reconstruction.

Abstract

We assess the viability of successful reconstruction of the evolution of the dark energy equation of state using varying fundamental couplings, such as the fine structure constant or the proton-to-electron mass ratio. We show that the same evolution of the dark energy equation of state parameter with cosmic time may be associated with arbitrary variations of the fundamental couplings. Various examples of models with the same (different) background evolution and different (the same) time variation of fundamental couplings are studied in the letter. Although we demonstrate that, for a broad family of models, it is possible to redefine the scalar field in such a way that its dynamics is that of a standard quintessence scalar field, in general such redefinition leads to the breakdown of the linear relation between the scalar field and the variation of fundamental couplings. This implies that the assumption of a linear coupling is not sufficient to guarantee a successful reconstruction of the dark energy dynamics and consequently additional model dependent assumptions about the scalar field responsible for the dark energy need to be made.