Primordial Non-Gaussianity in the Cosmic Microwave Background

TL;DR

This review discusses how primordial non-Gaussianity in the cosmic microwave background can reveal early universe physics, covering theoretical models, observational methods, current constraints, and non-primordial sources of non-Gaussian signals.

Contribution

It provides a comprehensive overview of theoretical predictions, data analysis techniques, and current observational constraints on primordial non-Gaussianity in the CMB.

Findings

Current constraints on non-Gaussianity from CMB data.

Potential of bispectrum estimators to detect primordial signals.

Identification of non-primordial sources affecting non-Gaussianity measurements.

Abstract

In the last few decades, advances in observational cosmology have given us a standard model of cosmology. We know the content of the universe to within a few percent. With more ambitious experiments on the way, we hope to move beyond the knowledge of what the universe is made of, to why the universe is the way it is. In this review paper we focus on primordial non-Gaussianity as a probe of the physics of the dynamics of the universe at the very earliest moments. We discuss 1) theoretical predictions from inflationary models and their observational consequences in the cosmic microwave background (CMB) anisotropies; 2) CMB--based estimators for constraining primordial non-Gaussianity with an emphasis on bispectrum templates; 3) current constraints on non-Gaussianity and what we can hope to achieve in the near future; and 4) non-primordial sources of non-Gaussianities in the CMB such as bispectrum due to second order effects, three way cross-correlation between primary-lensing-secondary CMB, and possible instrumental effects.