Magnetars as Laboratories for Strong Field QED

TL;DR

This paper investigates how extremely strong magnetic fields in magnetars influence quantum electrodynamics phenomena like vacuum polarization, birefringence, and electron-positron pair creation, providing analytical and numerical insights into these effects.

Contribution

It introduces a closed-form formula for the one-loop effective action in supercritical magnetic and subcritical electric fields, advancing understanding of strong field QED in astrophysical contexts.

Findings

Analytical and numerical calculation of vacuum birefringence in magnetars.

Identification of conditions for electron-positron pair creation.

Discussion of potential observational measurements in magnetar environments.

Abstract

A strong electromagnetic field polarizes the vacuum and in the presence of an electric field creates pairs of a charged particle and its anti-particle. Magnetars, highly magnetized neutron stars with magnetic field comparable to or greater than the Schwinger field, give a significant amount of the vacuum polarization and vacuum birefringence and the induced electric field can create the electron-positron pairs, which are strong field quantum electrodynamics (QED) processes. In this paper, we use a closed formula for the one-loop effective action in the presence of a supercritical magnetic field and a subcritical electric field, find the vacuum birefringence analytically and numerically, and then discuss possible measurements in magnetars.