How to Distinguish Dark Energy and Modified Gravity?

TL;DR

This paper explores the challenge of distinguishing dark energy from modified gravity, showing that interactions between dark energy and dark matter can make these models indistinguishable using traditional probes, thus requiring new methods.

Contribution

It demonstrates that dark energy-dark matter interactions can mimic modified gravity effects, highlighting the need for additional observational probes beyond expansion and growth histories.

Findings

Dark energy-dark matter interactions can replicate modified gravity signatures.

Traditional probes may be insufficient to distinguish these models.

Complementary observational methods are necessary for accurate differentiation.

Abstract

The current accelerated expansion of our universe could be due to an unknown energy component (dark energy) or a modification to general relativity (modified gravity). In the literature, it has been proposed that combining the probes of the cosmic expansion history and growth history can distinguish between dark energy and modified gravity. In this work, without invoking non-trivial dark energy clustering, we show that the possible interaction between dark energy and dark matter could make the interacting dark energy model and the modified gravity model indistinguishable. An explicit example is also given. Therefore, it is required to seek some complementary probes beyond the ones of cosmic expansion history and growth history.