Generation of circular polarization of CMB due to the Euler-Heisenberg Lagrangian

TL;DR

This paper demonstrates that the Euler-Heisenberg Lagrangian can generate circular polarization in the Cosmic Microwave Background (CMB), providing a theoretical basis for potential future observations of this polarization.

Contribution

It introduces a novel mechanism for circular polarization generation in CMB via the Euler-Heisenberg effective Lagrangian, using the Quantum Boltzmann Equation.

Findings

Euler-Heisenberg Lagrangian can produce circular polarization in CMB.

Estimated Faraday conversion phase is around 10^{-13}.

Provides a lower bound on CMB circular polarization.

Abstract

It is known that the dominant contribution of primordial anisotropies of Cosmic Microwave Background (CMB) is linearly polarized via Compton scattering. However circular polarization of this anisotropy has not been observed up to now, but it has not been excluded in observational evidence. Here we show that the Euler-Heisenberg Effective Lagrangian can generate circular polarization in CMB. This generation is calculated by using the Quantum Boltzmann Equation for the time evolution of the Stokes parameter. Also, we estimate the Faraday conversion phase in order of $10^{-13} $ due to this Lagrangian which gives a lower bound on circular polarization of CMB.