The Distinguishability of Interacting Dark Energy from Modified Gravity

TL;DR

This paper investigates whether interacting dark energy models can be distinguished from modified gravity theories using observational data, finding limitations in their distinguishability and viability.

Contribution

It demonstrates that certain interacting dark energy models cannot always replicate the expansion and growth histories of modified gravity cosmologies, highlighting challenges in model differentiation.

Findings

Matched interacting dark energy models are observationally disfavoured compared to DGP models.

It is often impossible to find a physical interacting dark energy model sharing the same histories as scalar-tensor theories.

Some models cannot be distinguished based solely on expansion and growth history comparisons.

Abstract

We study the observational viability of coupled quintessence models with their expansion and growth histories matched to modified gravity cosmologies. We find that for a Dvali-Gabadadze-Porrati model which has been fitted to observations, the matched interacting dark energy models are observationally disfavoured. We also study the distinguishability of interacting dark energy models matched to scalar-tensor theory cosmologies and show that it is not always possible to find a physical interacting dark energy model which shares their expansion and growth histories.