Observational Constraints on Early Coupled Quintessence

TL;DR

This paper constrains an early coupled quintessence model with a scalar field mediating a fifth force among dark matter, using cosmological data to limit the interaction strength and its activation epoch.

Contribution

It provides new observational constraints on the coupling strength and activation redshift in an early coupled quintessence model, revealing a degeneracy between these parameters.

Findings

Degeneracy between coupling strength and activation redshift.

Constraints consistent across different scaling regimes.

Limits on fifth force effects in dark matter from cosmological data.

Abstract

We investigate an Early Coupled Quintessence model where a light scalar mediates a fifth force stronger than gravity among dark matter particles and leads to the growth of perturbations prior to matter-radiation equality. Using cosmological data from the $\textit{Planck}$ Cosmic Microwave Background power spectra, the Pantheon+ Type 1a Supernovae, Baryon Acoustic Oscillations, and Big Bang Nucleosynthesis, we constrain the coupling strength $\beta$ and the redshift $z_{\rm OFF}$ at which the interaction becomes effectively inactive, finding a firm degeneracy between these two parameters which holds true regardless of when the scaling regime begins.