Cosmic microwave background anomalies in an open universe

TL;DR

This paper proposes that large-scale anomalies in the cosmic microwave background can be explained by an open universe model with super-curvature modes, providing a natural explanation for observed asymmetries.

Contribution

It introduces an open universe implementation of the large-scale gradient mechanism to explain CMB anomalies, compatible with current constraints.

Findings

Open universe models can produce large-scale CMB asymmetries.

Super-curvature modes explain dipole power asymmetry.

Model aligns with observational constraints.

Abstract

We argue that the observed large-scale cosmic microwave anomalies, discovered by WMAP and confirmed by the Planck satellite, are most naturally explained in the context of a marginally-open universe. Particular focus is placed on the dipole power asymmetry, via an open universe implementation of the large-scale gradient mechanism of Erickcek et al. Open inflation models, which are motivated by the string landscape and which can excite `super-curvature' perturbation modes, can explain the presence of a very-large-scale perturbation that leads to a dipole modulation of the power spectrum measured by a typical observer. We provide a specific implementation of the scenario which appears compatible with all existing constraints.