The IR-resummed Effective Field Theory of Large Scale Structures

TL;DR

This paper introduces a Lagrangian-based resummation method within the Effective Field Theory framework to accurately model large scale structure power spectra, effectively removing BAO residuals and extending the UV reach of predictions.

Contribution

It develops a new Lagrangian resummation technique for EFT of large scale structures, improving agreement with simulations and addressing BAO residuals in power spectrum calculations.

Findings

Two-loop EFT results agree with simulations up to k~0.6 h/Mpc within 1%

Lagrangian resummation removes BAO residual oscillations

Tracking velocities enhances the UV reach of momentum power spectra

Abstract

We present a new method to resum the effect of large scale motions in the Effective Field Theory of Large Scale Structures. Because the linear power spectrum in $\Lambda$CDM is not scale free the effects of the large scale flows are enhanced. Although previous EFT calculations of the equal-time density power spectrum at one and two loops showed a remarkable agreement with numerical results, they also showed a 2% residual which appeared related to the BAO oscillations. We show that this was indeed the case, explain the physical origin and show how a Lagrangian based calculation removes this differences. We propose a simple method to upgrade existing Eulerian calculations to effectively make them Lagrangian and compare the new results with existing fits to numerical simulations. Our new two-loop results agrees with numerical results up to $k\sim 0.6 h/$Mpc to within 1% with no oscillatory residuals. We also compute power spectra involving momentum which is significantly more affected by the large scale flows. We show how keeping track of these velocities significantly enhances the UV reach of the momentum power spectrum in addition to removing the BAO related residuals. We compute predictions for the real space correlation function around the BAO scale and investigate its sensitivity to the EFT parameters and the details of the resummation technique.