Small non-Gaussianity and dipole asymmetry in the CMB

TL;DR

This paper explores how multi-field inflation models can produce small non-Gaussianity and dipole asymmetry in the CMB, but finds it challenging to fully explain the observed asymmetry within simple scenarios.

Contribution

It proposes a prescription for generating small non-Gaussianity and dipole asymmetry in the CMB using multi-field inflation, highlighting the difficulties in simple models.

Findings

Multi-field inflation can produce large non-Gaussianity with fine cancellations.

The simple slow-roll scenario struggles to explain the observed dipole asymmetry.

Speculative models may be needed to account for the asymmetry.

Abstract

In this paper we provide a prescription for obtaining a small non-Gaussianity and the observed dipole asymmetry in the cosmic microwave background radiation. The observations inevitably lead to multi-field inflationary dynamics, where each field can create positive or negative large non-Gaussianity, resulting a fine cancellation but with an observable imprint on the hemispherical asymmetry. We discuss this possibility within a simple slow-roll scenario and find that it is hard to explain the observed dipole asymmetry. We briefly discuss some speculative scenarios where one can explain dipole asymmetry.