Behaviour of Charged Spinning Massless Particles

TL;DR

This paper revisits the classical theory of massless charged spinning particles, clarifying energy definitions, conservation laws, and showing how spin-field interactions can alter velocity without breaking Lorentz invariance.

Contribution

It provides a proper definition of energy and momentum for massless charged particles with spin and explores their velocity behavior under electromagnetic interactions.

Findings

Energy and momentum conservation laws are established.

Particle velocity can differ from c due to spin-field interactions.

Lorentz invariance remains intact despite velocity deviations.

Abstract

We revisit the classical theory of a relativistic massless charged point particle with spin and interacting with an external electromagnetic field. In particular, we give a proper definition of its kinetic energy and its total energy, the latter being conserved when the external field is stationary. We also write the conservation laws for the linear and angular momenta. Finally, we find that the particle's velocity may differ from $c$ as a result of the spin---electromagnetic field interaction, without jeopardizing Lorentz invariance.