Universal self-force from an extended object approach

We present a simple approach to determine the self-force acting on an accelerating charged particle. In this approach one considers an extended charged object of finite size ε, and calculates the overall contribution of the mutual electromagnetic forces at the limit ε⃗0. Previous implementations of this approach often yielded a divergent term ∝1/ε that could not be cured by mass renormalization. Here we explain the origin of this problem and provide a simple method for fixing it, thereby generalizing and simplifying previous analyses. We obtain a consistent, universal, expression for the extended-object self-force, which conforms with Dirac’s well known formula.