A derivation of the Breit equation from Barut's covariant formulation of electrodynamics in terms of direct interactions

TL;DR

This paper derives the Breit equation for two interacting spin-1/2 particles directly from Barut's covariant formulation of electrodynamics, emphasizing a field-free interaction approach.

Contribution

It presents a derivation of the Breit equation from Barut's covariant direct interaction framework, connecting fundamental theory with an approximate two-particle equation.

Findings

Derivation of the Breit equation from covariant direct interactions

Application of Lagrangian formalism to spinor interactions

Approximate semirelativistic treatment of two-particle systems

Abstract

We study Barut's covariant equations describing the electromagnetic interactions between N spin-1/2 particles. In the covariant formulation each particle is described by a Dirac spinor. It is assumed that the interactions between the particles are not mediated by a bosonic field (direct interactions). Within this formulation, using the Lagrangian formalism, we derive the approximate (semirelativistic) Breit equation for two interacting spin-1/2 particles.