Mode truncations and scattering in strong fields

TL;DR

This paper explores mode truncation in quantum field theories, comparing quantization methods and proposing a new interpretation for depletion effects in strong laser fields based on the dressing approach to QED.

Contribution

It introduces a comparison between instant-form and front-form quantization in mode-truncated QED and offers a novel interpretation of depletion effects using the dressing approach.

Findings

Front-form quantization simplifies calculations with zero modes.

Mode truncation provides a non-perturbative solution approach.

New interpretation of depletion effects based on infra-red structure.

Abstract

Truncating quantum field theories to a dominant mode offers a non-perturbative approach to their solution. We consider here the interaction of charged scalar matter with a single mode of the electromagnetic field. The implied breaking of explicit Lorentz invariance prompts us to compare instant-form quantisation and front-form, with the latter yielding significant simplifications when light-front zero modes are included. Using these field theory results we reassess the validity of existing first-quantised approaches to depletion effects in strong laser fields, and propose an alternative interpretation based on the dressing approach to QED and its infra-red structure.