Spin precession of a particle with an electric dipole moment: contributions from classical electrodynamics and from the Thomas effect

TL;DR

This paper derives a covariant equation for the spin precession of particles with electric and magnetic dipole moments, explicitly separating classical electrodynamics contributions from the Thomas effect, using a simple frame-based formulation.

Contribution

It provides a new, fully covariant derivation of the spin precession equation, explicitly distinguishing classical electrodynamics effects from the Thomas precession.

Findings

Derived Lorentz transformations for dipole moments and spin from classical electrodynamics.

Confirmed the tensor construction from basic Maxwell equations.

Presented a simplified, covariant form of the spin precession equation.

Abstract

The new derivation of the equation of the spin precession is given for a particle possessing electric and magnetic dipole moments. Contributions from classical electrodynamics and from the Thomas effect are explicitly separated. A fully covariant approach is used. The final equation is expressed in a very simple form in terms of the fields in the instantaneously accompanying frame. The Lorentz transformations of the electric and magnetic dipole moments and of the spin are derived from basic equations of classical electrodynamics. For this purpose, the Maxwell equations in matter are used and the result is confirmed by other methods. An antisymmetric four-tensor is correctly constructed from the electric and magnetic dipole moments.