Cosmic tango between the very small and the very large: Addressing CMB anomalies through Loop Quantum Cosmology

TL;DR

This paper explores how Loop Quantum Cosmology can address anomalies in the cosmic microwave background by modifying the primordial power spectrum, leading to a more consistent ΛCDM model and new observational predictions.

Contribution

It demonstrates that loop quantum cosmology introduces scale dependence in the primordial power spectrum, alleviating certain CMB anomalies and providing novel testable predictions.

Findings

Large scale power suppression is alleviated.

Lensing amplitude anomalies are reduced.

New predictions for future CMB observations.

Abstract

While the standard, six-parameter, spatially flat $\Lambda$CDM model has been highly successful, certain anomalies in the cosmic microwave background bring out a tension between this model and observations. The statistical significance of any one anomaly is small. However, taken together, the presence of two or more of them imply that according to standard inflationary theories we live in quite an exceptional universe. We revisit the analysis of the PLANCK collaboration using loop quantum cosmology, where an unforeseen interplay between the ultraviolet and the infrared makes the \emph{primordial} power spectrum scale dependent at very small $k$. Consequently, we are led to a somewhat different $\Lambda$CDM universe in which anomalies associated with large scale power suppression and the lensing amplitude are both alleviated. The analysis also leads to new predictions for future observations. This article is addressed both to cosmology and LQG communities, and we have attempted to make it self-contained.