Where the Lorentz-Abraham-Dirac equation for the radiation reaction force fails, and why the "proofs" break down

TL;DR

The paper demonstrates the failure of the Lorentz-Abraham-Dirac equation for radiation reaction in certain systems, showing that common proofs of its validity are flawed and proposing a generalized correction for some cases.

Contribution

It identifies the limitations of the LAD equation, explains the source of discrepancies, and introduces a generalized radiation reaction force to address these issues.

Findings

Discrepancy between coherent radiated energy and LAD-based energy loss

Omission of mixing terms in the Poynting vector causes errors

Generalized equation improves accuracy for some systems

Abstract

We calculate the energy radiated coherently by a system of $N$ charged non relativistic particles. It disagrees with the energy loss which is obtained if one employs the Lorentz Abraham Dirac (LAD) equation for each particle, and sums up the contributions. This fact was already clearly stated in the classical literature long ago. The reason for the discrepancy is the omission of the mixing terms in the Poynting vector. For some simple systems we present a generalized equation for the radiation reaction force which cures this defect. The counter examples show that the LAD equation cannot be generally valid and that all "proofs" must fail somewhere. We demonstrate this failure for some popular examples in the literature.