Multi-field inflation and cosmological perturbations

TL;DR

This paper reviews multi-field inflation models and cosmological perturbations, focusing on gauge fixing, perturbation actions, and non-linear aspects to facilitate systematic analysis.

Contribution

It offers a comprehensive overview of methods and formalism for studying perturbations in multi-field inflation, including gauge choices and non-linear perturbations.

Findings

Clarifies gauge fixing procedures for perturbations.

Provides formal expressions for perturbation actions in different gauges.

Briefly discusses non-linear perturbation analysis.

Abstract

We provide a concise review on multi-field inflation and cosmological perturbations. We discuss convenient and physically meaningful bases in terms of which perturbations can be systematically studied. We give formal accounts on the gauge fixing conditions and present the perturbation action in two gauges. We also briefly review non-linear perturbations.