Future weak lensing constraints in a dark coupled universe

TL;DR

Future weak lensing surveys like Euclid and LSST, combined with Planck data, could significantly constrain interactions in the dark sector, but degeneracies with other parameters pose challenges.

Contribution

This paper forecasts the potential of upcoming weak lensing surveys to constrain dark sector interactions and highlights parameter degeneracies that could bias cosmological inferences.

Findings

Future data could constrain the coupling to less than a few percent.

The coupling parameter is degenerate with dark matter density and Hubble constant.

Degeneracies may bias cosmological parameter estimates.

Abstract

Coupled cosmologies can predict values for the cosmological parameters at low redshifts which may differ substantially from the parameters values within non-interacting cosmologies. Therefore, low redshift probes, as the growth of structure and the dark matter distribution via galaxy and weak lensing surveys constitute a unique tool to constrain interacting dark sector models. We focus here on weak lensing forecasts from future Euclid and LSST-like surveys combined with the ongoing Planck cosmic microwave background experiment. We find that these future data could constrain the dimensionless coupling to be smaller than a few $\times 10^{-2}$. The coupling parameter $\xi$ is strongly degenerate with the cold dark matter energy density $\Omega_{c}h^2$ and the Hubble constant $H_0$.These degeneracies may cause important biases in the cosmological parameter values if in the universe there exists an interaction among the dark matter and dark energy sectors.