Local non-Gaussianity from inflation

TL;DR

This paper reviews how local non-Gaussianity in primordial perturbations, arising from inflationary models, can reveal early Universe physics, using the delta-N formalism and various scenarios like curvaton and ekpyrotic models.

Contribution

It provides a comprehensive review of local non-Gaussianity models and the delta-N formalism for calculating primordial density perturbations.

Findings

Overview of local non-Gaussianity models

Application of delta-N formalism to inflationary scenarios

Comparison of different early Universe models

Abstract

The non-Gaussian distribution of primordial perturbations has the potential to reveal the physical processes at work in the very early Universe. Local models provide a well-defined class of non-Gaussian distributions that arise naturally from the non-linear evolution of density perturbations on super-Hubble scales starting from Gaussian field fluctuations during inflation. I describe the delta-N formalism used to calculate the primordial density perturbation on large scales and then review several models for the origin of local primordial non-Gaussianity, including the cuvaton, modulated reheating and ekpyrotic scenarios. I include an appendix with a table of sign conventions used in specific papers.