Non-Gaussian Galaxy Stochasticity and the Noise-Field Formulation

TL;DR

This paper develops a new noise-field formulation within the effective field theory of large-scale structure to accurately model non-Gaussian stochastic contributions to galaxy density, enabling improved field-level inference.

Contribution

It introduces an alternative noise-field based formulation of the EFT partition function, capturing all stochastic effects at the field level and suitable for numerical sampling.

Findings

First EFT-based field-level inference with non-Gaussian stochasticity

Demonstration on dark matter halos using LEFTfield

Complete stochastic contributions modeled at the field level

Abstract

We revisit the stochastic, or noise, contributions to the galaxy density field within the effective field theory (EFT) of large-scale structure. Starting from the general, all-order expression of the EFT partition function, we elucidate how the stochastic contributions can be described by local nonlinear couplings of a single Gaussian noise field. We introduce an alternative formulation of the partition function in terms of such a noise field, and derive the corresponding field-level likelihood for biased tracers. This noise-field formulation can capture the complete set of stochastic contributions to the galaxy density at the field level in a normalized, positive-definite probability density which is suitable for numerical sampling. We illustrate this by presenting the first results of EFT-based field-level inference with non-Gaussian and density-dependent stochasticity on dark matter halos using LEFTfield.