Non-Gaussian Covariance of the Matter Power Spectrum in the Effective Field Theory of Large Scale Structure

TL;DR

This paper calculates the non-Gaussian covariance of the matter power spectrum at one-loop order using Standard Perturbation Theory and Effective Field Theory of Large Scale Structure, comparing results with simulations.

Contribution

It provides the first complete evaluation of one-loop non-Gaussian covariance including EFT corrections with seven operators, improving theoretical predictions for large scale structure.

Findings

EFT with one free parameter extends accurate predictions to higher k.

SPT matches simulations up to k~0.25 h/Mpc in one case.

Discrepancies between simulations suggest unaccounted systematics.

Abstract

We compute the non-Gaussian contribution to the covariance of the matter power spectrum at one-loop order in Standard Perturbation Theory (SPT), and using the framework of the effective field theory (EFT) of large scale structure (LSS). The complete one-loop contributions are evaluated for the first time, including the leading EFT corrections that involve seven independent operators, of which four appear in the power spectrum and bispectrum. We compare the non-Gaussian part of the one-loop covariance computed with both SPT and EFT of LSS to two separate simulations. In one simulation, we find that the one-loop prediction from SPT reproduces the simulation well to $k_i + k_j \sim$ 0.25 h/Mpc, while in the other simulation we find a substantial improvement of EFT of LSS (with one free parameter) over SPT, more than doubling the range of $k$ where the theory accurately reproduces the simulation. The disagreement between these two simulations points to unaccounted for systematics, highlighting the need for improved numerical and analytic understanding of the covariance.