Motion of macroscopic bodies in the electromagnetic field

TL;DR

This paper develops a comprehensive theory for the motion of macroscopic dielectric bodies in electromagnetic fields, applicable in quantum and classical regimes, and confirms classical force consistency and quantum effects like Casimir-induced motion.

Contribution

It introduces a unified theory for dielectric body motion in electromagnetic fields valid in both quantum and classical regimes, addressing momentum and energy considerations.

Findings

Classical force aligns with Abraham momentum

Wave-packet experiences acceleration from Casimir force

Quantum fluctuations induce pair creation within the object

Abstract

A theory is presented for calculating the effect of the electromagnetic field on the centre of mass of a macroscopic dielectric body that is valid in both quantum and classical regimes. We apply the theory to find the classical equation of motion for the centre of mass of a macroscopic object in a classical field, and the spreading of an initially localized wave-packet representing the centre of mass of a small object, in a quantum field. The classical force is found to be consistent with the identification of the Abraham momentum with the mechanical momentum of light, and the motion of the wave-packet is found to be subject to an acceleration due to the Casimir force, and a time dependent fluctuating motion due the creation of pairs of excitations within the object. The theory is valid for any dielectric that has susceptibilities satisfying the Kramers-Kronig relations, and is not subject to arguments regarding the form of the electromagnetic energy-momentum tensor within a medium.