CMB statistical anisotropies of classical and quantum origins

TL;DR

This paper investigates how different types of relics from the early universe influence inflation and the resulting anisotropies in the cosmic microwave background, highlighting the role of initial quantum states in observable signatures.

Contribution

It distinguishes between matter-induced and metric-induced relics in inflationary anisotropies and explores how non-Bunch-Davies states affect scale dependence of these anisotropies.

Findings

Angular dependence of anisotropy is degenerate for both relic types.

Scale dependence differs and is observationally distinctive.

Non-Bunch-Davies states extend anisotropy to shorter scales, affecting scale dependence.

Abstract

We examine the impact of different anisotropic relics on inflation, in particular the predictions on the density perturbations. These relics can be the source of the large scale anomalies in the cosmic microwave background. There are two different types of background relics, one from the matter sector and the other purely from the metric. Although the angular-dependence of the statistical anisotropy in both cases are degenerate, the scale-dependence are observationally distinctive. In addition, we demonstrate that non-Bunch-Davies vacuum states can extend the statistical anisotropy to much shorter scales, and leave a scale-dependence that is insensitive to the different backgrounds but sensitive to the initial quantum state.