Electromagnetic Couplings of Dark Domain Walls

TL;DR

This paper explores how dark sector domain walls coupled via Chern--Simons terms can induce optical activity, leading to measurable polarization rotation in the cosmic microwave background within observational bounds.

Contribution

It introduces a model extending Maxwell electrodynamics with a Chern--Simons coupling to dark sector domain walls and analyzes its observational implications.

Findings

Dark energy domain walls can cause polarization rotation of CMB.

The model's parameters can satisfy observational bounds.

Predicted polarization rotation is approximately 10^{-3} radians.

Abstract

We extend Maxwell electrodynamics with a Chern--Simons coupling to a dark sector top form sourced by domain walls. Electromagnetic fields which cross such domain walls exhibit optical activity. We outline the parameter space where the theory satisfies the observational bounds from domain wall nucleation rates and cosmic microwave background anisotropies. In this regime, the discretely evanescent dark energy walls can produce a polarization rotation of cosmic microwave background by $\Delta\vartheta \sim 10^{-3} ~{\rm radians}$.