QED vacuum fluctuations and induced electric dipole moment of the neutron

TL;DR

This paper explores how quantum vacuum fluctuations in QED induce an electric dipole moment in neutrons with magnetic moments when exposed to external electric fields, revealing non-linear electromagnetic effects.

Contribution

It demonstrates, using the Euler-Heisenberg effective Lagrangian, that neutral particles with magnetic moments can develop induced electric dipoles in external fields, a novel non-linear QED effect.

Findings

Neutrons can acquire an induced electric dipole moment in external electric fields.

The effect is derived using the one-loop Euler-Heisenberg Lagrangian.

Neutrons are proposed as candidates to detect this QED non-linearity.

Abstract

Quantum fluctuations in the QED vacuum generate non-linear effects, such as peculiar induced electromagnetic fields. In particular, we show here that an electrically neutral particle, possessing a magnetic dipole moment, develops an induced electric dipole-type moment with unusual angular dependence, when immersed in a quasistatic, constant external electric field. The calculation of this effect is done in the framework of the Euler-Heisenberg effective QED Lagrangian, corresponding to the weak field asymptotic expansion of the effective action to one-loop order. It is argued that the neutron might be a good candidate to probe this signal of non-linearity in QED.