General relativistic corrections and non-Gaussianity in large scale structure

TL;DR

This paper reviews recent efforts to incorporate full general relativistic effects and non-Gaussianities into the analysis of large-scale structure, moving beyond simple linear perturbation models.

Contribution

It summarizes current research directions on second-order perturbations, relativistic observables, and non-Newtonian approaches in large-scale cosmology.

Findings

Highlighting the importance of relativistic corrections in large-scale structure analysis

Discussing the connection between non-Gaussianities and higher-order perturbations

Outlining future theoretical and observational research prospects

Abstract

General relativistic cosmology cannot be reduced to linear relativistic perturbations superposed on an isotropic and homogeneous (Friedmann-Robertson-Walker) background, even though such a simple scheme has been successfully applied to analyse a large variety of phenomena (such as Cosmic Microwave Background primary anisotropies, matter clustering on large scales, weak gravitational lensing, etc.). The general idea of going beyond this simple paradigm is what characterises most of the efforts made in recent years: the study of second and higher-order cosmological perturbations including all general relativistic contributions -- also in connection with primordial non-Gaussianities -- the idea of defining large-scale structure observables directly from a general relativistic perspective, the various attempts to go beyond the Newtonian approximation in the study of non-linear gravitational dynamics, by using e.g., Post-Newtonian treatments, are all examples of this general trend. Here we summarise some of these directions of investigation, with the aim of emphasising future prospects in this area of cosmology, both from a theoretical and observational point of view.