Constraining dark sector perturbations I: cosmic shear and CMB lensing

TL;DR

This paper investigates constraints on dark sector perturbations using current and forecasted cosmological data, exploring models including scalar fields, elastic media, and Lorentz-violating gravity, and assessing future experiments' potential to distinguish these models.

Contribution

It develops a theoretical framework for observable effects of diverse dark sector models and evaluates current and future data's ability to constrain their parameters.

Findings

Current data exclude some parameter ranges but remain compatible with a cosmological constant.

Future experiments like CoRE, PRISM, and Euclid will significantly improve constraints.

The models considered can be distinguished with upcoming high-precision cosmological observations.

Abstract

We present current and future constraints on equations of state for dark sector perturbations. The equations of state considered are those corresponding to a generalized scalar field model and time-diffeomorphism invariant $L(g)$ theories that are equivalent to models of a relativistic elastic medium and also Lorentz violating massive gravity. We develop a theoretical understanding of the observable impact of these models. In order to constrain these models we use CMB temperature data from Planck, BAO measurements, CMB lensing data from Planck and the South Pole Telescope, and weak galaxy lensing data from CFHTLenS. We find non-trivial exclusions on the range of parameters, although the data remains compatible with $w=-1$. We gauge how future experiments will help to constrain the parameters. This is done via a likelihood analysis for CMB experiments such as CoRE and PRISM, and tomographic galaxy weak lensing surveys, focussing in on the potential discriminatory power of Euclid on mildly non-linear scales.