The quantum vacuum in electromagnetic fields: From the Heisenberg-Euler effective action to vacuum birefringence

TL;DR

This paper reviews the quantum vacuum's behavior under electromagnetic fields, deriving the Heisenberg-Euler effective action and exploring vacuum birefringence as a key optical signature of quantum nonlinearity.

Contribution

It provides a pedagogical derivation of the Heisenberg-Euler effective action and applies it to analyze vacuum birefringence phenomena.

Findings

Derivation of the Heisenberg-Euler effective action in constant fields

Analysis of vacuum birefringence as an optical signature of quantum vacuum nonlinearity

Identification of vacuum birefringence as a promising experimental signature

Abstract

The focus of these lectures is on the quantum vacuum subjected to classical electromagnetic fields. To this end we explicitly derive the renowned Heisenberg-Euler effective action in constant electromagnetic fields in a rather pedagogical and easy to conceive way. As an application, we use it to study vacuum birefringence constituting one of the most promising optical signatures of quantum vacuum nonlinearity.