Physics of non-Gaussian fields and the cosmological genus statistic

TL;DR

This paper introduces a decomposition technique for the cosmological genus statistic to analyze the effects of various physical processes on non-Gaussian features of the large-scale structure, enhancing the tool's utility in cosmology.

Contribution

A new orthogonal polynomial decomposition method for the genus statistic that isolates effects like galaxy bias, gravitational evolution, and primordial non-Gaussianity.

Findings

Quantifies systematics affecting topological measurements.

Analyzes non-Gaussian deformations in Horizon Run simulations.

Studies genus curve evolution with primordial non-Gaussianity.

Abstract

We report a technique to calculate the impact of distinct physical processes inducing non-Gaussianity on the cosmological density field. A natural decomposition of the cosmic genus statistic into an orthogonal polynomial sequence allows complete expression of the scale-dependent evolution of the morphology of large-scale structure, in which effects including galaxy bias, nonlinear gravitational evolution and primordial non-Gaussianity may be delineated. The relationship of this decomposition to previous methods for analysing the genus statistic is briefly considered and the following applications are made: i) the expression of certain systematics affecting topological measurements; ii) the quantification of broad deformations from Gaussianity that appear in the genus statistic as measured in the Horizon Run simulation; iii) the study of the evolution of the genus curve for simulations with primordial non-Gaussianity. These advances improve the treatment of flux-limited galaxy catalogues for use with this measurement and further the use of the genus statistic as a tool for exploring non-Gaussianity.