Finding structure in the dark: coupled dark energy, weak lensing, and the mildly nonlinear regime

TL;DR

This paper demonstrates that combining galaxy lensing, clustering, and CMB data can constrain dark sector interactions to a few percent using only mildly nonlinear scales, reducing the need for extensive simulations.

Contribution

It introduces a method to constrain dark sector couplings using linear and quasi-linear scales, avoiding costly n-body simulations for a class of models.

Findings

Dark sector coupling constrained to a few percent level.

Mildly nonlinear scales suffice for robust constraints.

Effective field theory can describe these scales.

Abstract

We reexamine interactions between the dark sectors of cosmology, with a focus on robust constraints that can be obtained using only mildly nonlinear scales. While it is well known that couplings between dark matter and dark energy can be constrained to the percent level when including the full range of scales probed by future optical surveys, calibrating matter power spectrum emulators to all possible choices of potentials and couplings requires many computationally expensive n-body simulations. Here we show that lensing and clustering of galaxies in combination with the Cosmic Microwave Background (CMB) is capable of probing the dark sector coupling to the few percent level for a given class of models, using only linear and quasi-linear Fourier modes. These scales can, in principle, be described by semi-analytical techniques such as the effective field theory of large-scale structure.