Induced Cosmological Anisotropies and CMB Anomalies by a non-Abelian Gauge-Gravity Interaction

TL;DR

This paper explores how non-Abelian $SU(2)$ gauge fields coupled to gravity can induce small cosmological anisotropies, potentially explaining CMB anomalies and impacting the Sachs-Wolfe effect within a perturbative framework.

Contribution

It introduces a non-Abelian gauge-gravity interaction model that generates anisotropies as perturbative corrections to FLRW cosmology, extending previous abelian models.

Findings

Non-Abelian gauge fields induce anisotropies in cosmological models.

Anisotropies influence the Sachs-Wolfe effect.

The model provides a potential explanation for CMB anomalies.

Abstract

We present a non-abelian cousin of the model presented in \cite{Lee:2022rtz} which induces cosmological anisotropies on top of standard FLRW geometry. This is in some sense doing a cosmological mean field approximation, where the mean field cosmological model under consideration would be the standard FLRW, and the induced anisotropies are small perturbative corrections on top of it. Here we mostly focus on the non-abelian $SU(2)$ gauge fields coupled to the gravity to generate the anisotropies, which can be a viable model for the axion-like particle (ALP) dark sector. The induced anisotropies are consequences of the non-trivial back-reaction of the gauge fields on the gravity sector, and by a clever choice of the parametrization, one can generate the Bianchi model we have studied in this note. We also show that the anisotropies influence the Sachs-Wolfe effect and we discuss the implications.