Marginalized Fisher Forecast for Horndeski Dark Energy Models

TL;DR

This paper forecasts how well future supernova and galaxy surveys can constrain Horndeski dark energy models using EFT formalism, accounting for all parameter uncertainties and marginalization effects.

Contribution

It extends previous constraints by allowing all parameters to vary and marginalize, providing more realistic forecasts for dark energy parameter constraints.

Findings

Constraints worsen by a factor of a few after marginalization.

Constraint on dark energy equation of state w remains stable.

Marginalization impacts EFT dark energy parameters more than w.

Abstract

We use effective field theory (EFT) formalism to forecast the constraint on Horndeski class of dark energy models with future supernova and galaxy surveys. Previously (Gleyzes {\it et al.}) computed unmarginalized constraints (68\% CL error $\sim 10^{-3}$--$10^{-2}$) on EFT dark energy parameters by fixing all other parameters. We extend the previous work by allowing all cosmological parameters and nuisance parameters to vary and marginalizing over them. We find that (i) the constraints on EFT dark energy parameters are typically worsen by a factor of few after marginalization, and (ii) the constraint on the dark energy equation of state $w$ is not significantly affected by the inclusion of EFT dark energy parameters.