Probing interaction in the dark sector

TL;DR

This paper investigates the precision needed in future measurements of the universe's expansion rate to detect interactions between dark matter and dark energy, using both simulations and analytical methods.

Contribution

It introduces an analytical approach to estimate the measurement accuracy required to identify dark sector interactions, validated against Monte Carlo simulations.

Findings

Analytical method accurately predicts error propagation.

Detection of dark sector interaction requires less than 1% accuracy in $H(z)$ measurements.

Future experiments need high precision to distinguish coupled quintessence models.

Abstract

A phenomenological attempt at alleviating the so-called coincidence problem is to allow the dark matter and dark energy to interact. By assuming a coupled quintessence scenario characterized by an interaction parameter $\epsilon$, we investigate the precision in the measurements of the expansion rate $H(z)$ required by future experiments in order to detect a possible deviation from the standard $\Lambda$CDM model ($\epsilon = 0$). We perform our analyses at two levels, namely: through Monte Carlo simulations based on $\epsilon$CDM models, in which $H(z)$ samples with different accuracies are generated and through an analytic method that calculates the error propagation of $\epsilon$ as a function of the error in $H(z)$. We show that our analytical approach traces simulations accurately and find that to detect an interaction {using $H(z)$ data only, these must reach an accuracy better than 1%.