Comparison of different forms for the "spin" and "orbital" components of the angular momentum of light

TL;DR

This paper compares three different methods for decomposing the angular momentum of light into spin and orbital parts, revealing no unique preferred decomposition within classical electrodynamics.

Contribution

It provides a comparative analysis of existing decompositions of electromagnetic angular momentum, highlighting the lack of a definitive method.

Findings

All three decompositions differ significantly.

No unique, preferred decomposition exists in classical electrodynamics.

The choice of decomposition depends on the context or application.

Abstract

We compare three attempts that have been made to decompose the angular momentum of the electromagnetic field into components of an "orbital" and "spin" nature. All three expressions are different and it appears, on the basis of classical electrodynamics, that there is no preferred way of decomposing the angular momentum of the electromagnetic field into orbital and spin components, even in an inertial frame.