What is spin?
Classical Physics
2007-05-23 v3
Abstract
This is a late answer to question #79 by R.I. Khrapko, "Does plane wave not carry a spin?," Am. J. Phys. /69/, 405 (2001), and a complement (on gauge invariance, massive spin 1 and 1/2, and massless spin 2 fields) to the paper by H.C. Ohanian, "What is spin?," Am. J. Phys. /54/, 500--505 (1985). In particular, it is confirmed that "spin" is a classical quantity which can be calculated for any field using its definition, namely that it is just the non-local part of the conserved angular momentum. This leads to explicit expressions which are bilinear in the fields and which agree with their standard "quantum" counterparts.
Cite
@article{arxiv.physics/0308027,
title = {What is spin?},
author = {Andre Gsponer},
journal= {arXiv preprint arXiv:physics/0308027},
year = {2007}
}
Comments
Submitted to Am. J. Phys., 6 pages