Efficient exploration of cosmology dependence in the EFT of LSS

TL;DR

This paper introduces efficient methods and public codes for rapidly predicting the matter power spectrum's dependence on cosmological parameters within the EFT of LSS, enabling high-precision analysis for near-Planck cosmologies.

Contribution

It develops two novel, computationally efficient approaches—difference-based and Taylor expansion—for exploring cosmology dependence in the EFT of LSS, with implementations for the matter power spectrum at two loops.

Findings

Power spectrum evaluation within 3σ of Planck cosmology takes minutes with 1% accuracy.

Taylor expansion provides instant, high-precision predictions for similar cosmologies.

Methods are suitable for high-precision, large-scale structure analyses and are publicly available.

Abstract

The most effective use of data from current and upcoming large scale structure~(LSS) and CMB observations requires the ability to predict the clustering of LSS with very high precision. The Effective Field Theory of Large Scale Structure (EFTofLSS) provides an instrument for performing analytical computations of LSS observables with the required precision in the mildly nonlinear regime. In this paper, we develop efficient implementations of these computations that allow for an exploration of their dependence on cosmological parameters. They are based on two ideas. First, once an observable has been computed with high precision for a reference cosmology, for a new cosmology the same can be easily obtained with comparable precision just by adding the difference in that observable, evaluated with much less precision. Second, most cosmologies of interest are sufficiently close to the Planck best-fit cosmology that observables can be obtained from a Taylor expansion around the reference cosmology. These ideas are implemented for the matter power spectrum at two loops and are released as public codes. When applied to cosmologies that are within 3$\sigma$ of the Planck best-fit model, the first method evaluates the power spectrum in a few minutes on a laptop, with results that have 1\% or better precision, while with the Taylor expansion the same quantity is instantly generated with similar precision. The ideas and codes we present may easily be extended for other applications or higher-precision results.