Scattering in plane-wave backgrounds: infra-red effects and pole structure

TL;DR

This paper investigates scattering in strong plane wave backgrounds, demonstrating infra-red divergence removal via Bloch-Nordsieck and analyzing the pole structure of the Volkov propagator with lightfront quantisation.

Contribution

It reveals how infra-red divergences depend on background structure and shows the pole series describes a single on-shell particle.

Findings

Infra-red divergences can be removed using Bloch-Nordsieck.

The pole series in the propagator corresponds to a single particle.

Analysis uses lightfront quantisation to understand pole structure.

Abstract

We consider two aspects of scattering in strong plane wave backgrounds. First, we show that the infra-red divergences in elastic scattering depend on the structure of the background, but can be removed using the usual Bloch-Nordsieck approach. Second, we analyse the infinite series of shifted-mass-shell poles in the particle (Volkov) propagator using lightfront quantisation. The complete series of poles is shown to describe a single, on-shell, propagating particle.