Division of the Energy and of the Momentum of Electromagnetic Waves in Linear Media into Electromagnetic and Material Parts

TL;DR

This paper proposes a natural division of electromagnetic energy and momentum in linear media into electromagnetic and material parts, aligning with physical models and relativistic concepts, clarifying longstanding debates.

Contribution

It introduces a division framework for energy and momentum in linear media that aligns with physical models and relativistic momentum concepts, supported by reasonable dispersive models.

Findings

Electromagnetic energy and momentum are divided into electromagnetic and material parts.

The division aligns with models of dispersive, non-absorptive media.

Electromagnetic momentum relates to relativistic momentum, connecting Abraham and Minkowski forms.

Abstract

We defend a natural division of the energy density, energy flux and momentum density of electromagnetic waves in linear media in electromagnetic and material parts. In this division, the electromagnetic part of these quantities have the same form as in vacuum when written in terms of the macroscopic electric and magnetic fields, the material momentum is calculated directly from the Lorentz force that acts on the charges of the medium, the material energy is the sum of the kinetic and potential energies of the charges of the medium and the material energy flux results from the interaction of the electric field with the magnetized medium. We present reasonable models for linear dispersive non-absorptive dielectric and magnetic media that agree with this division. We also argue that the electromagnetic momentum of our division can be associated with the electromagnetic relativistic momentum, inspired on the recent work of Barnett [Phys. Rev. Lett. 104, 070401 (2010)] that showed that the Abraham momentum is associated with the kinetic momentum and the Minkowski momentum is associated with the canonical momentum.