Towards Precision Constraints on Gravity with the Effective Field Theory of Large-Scale Structure

TL;DR

This paper evaluates the effectiveness of the Effective Field Theory of Large-Scale Structure in modeling dark-matter clustering, comparing analytical predictions with simulations in both standard and modified gravity scenarios, and measures differences in model parameters.

Contribution

It demonstrates the application of EFTofLSS to modified gravity, compares resummation schemes, and provides a precision measurement of parameter differences between models.

Findings

EFTofLSS accurately models dark-matter power spectrum up to k≈0.14 h/Mpc.

Infrared resummation schemes agree within 1%.

Measured the proportionality between the speed of sound difference and linear coupling modification.

Abstract

We compare analytical computations with numerical simulations for dark-matter clustering, in general relativity and in the normal branch of DGP gravity (nDGP). Our analytical frameword is the Effective Field Theory of Large-Scale Structure (EFTofLSS), which we use to compute the one-loop dark-matter power spectrum, including the resummation of infrared bulk displacement effects. We compare this to a set of 20 COLA simulations at redshifts $z = 0$, $z=0.5$, and $z =1$, and fit the free parameter of the EFTofLSS, called the speed of sound, in both $\Lambda$CDM and nDGP at each redshift. At one-loop at $z = 0$, the reach of the EFTofLSS is $k_{\rm reach}\approx 0.14 \, h { \rm Mpc^{-1}}$ for both $\Lambda$CDM and nDGP. Along the way, we compare two different infrared resummation schemes and two different treatments of the time dependence of the perturbative expansion, concluding that they agree to approximately $1\%$ over the scales of interest. Finally, we use the ratio of the COLA power spectra to make a precision measurement of the difference between the speeds of sound in $\Lambda$CDM and nDGP, and verify that this is proportional to the modification of the linear coupling constant of the Poisson equation.