Large Scale Power Suppression in a Multifield Landscape

TL;DR

This paper explores how power suppression in the cosmic microwave background can arise from multifield inflation models, introducing a new mechanism called flume inflation that could explain observed large-scale anomalies.

Contribution

It demonstrates that multifield inflation can produce power suppression through a novel mechanism, extending single-field models and constraining scalar field dynamics.

Findings

Single-field models do not easily generalize to multifield scenarios for power suppression.

Superhorizon evolution in multifield models tends to erase initial power suppression.

Proposes the flume inflation mechanism as a new way to generate power suppression.

Abstract

Power suppression of the cosmic microwave background on the largest observable scales could provide valuable clues about the particle physics underlying inflation. Here we consider the prospect of power suppression in the context of the multifield landscape. Based on the assumption that our observable universe emerges from a tunnelling event and that the relevant features originate purely from inflationary dynamics, we find that the power spectrum not only contains information on single-field dynamics, but also places strong con- straints on all scalar fields present in the theory. We find that the simplest single-field models giving rise to power suppression do not generalise to multifield models in a straightforward way, as the resulting superhorizon evolution of the curvature perturbation tends to erase any power suppression present at horizon crossing. On the other hand, multifield effects do present a means of generating power suppression which to our knowledge has so far not been considered. We propose a mechanism to illustrate this, which we dub flume inflation.