A Lorentz and gauge invariant measure of laser intensity

TL;DR

The paper proposes a universal, Lorentz and gauge invariant measure of laser intensity, analyzing classical charge motion in strong electromagnetic fields through various models.

Contribution

It introduces a novel invariant measure of laser intensity and applies it to different electromagnetic field configurations.

Findings

The measure is explicitly calculated for crossed fields, plane waves, and vortex models.

It provides a consistent way to compare laser intensities across different relativistic scenarios.

The measure enhances understanding of charge dynamics in strong laser fields.

Abstract

Focussing on null fields as simple models of laser beams we discuss the classical relativistic motion of charges in strong electromagnetic fields. We suggest a universal, Lorentz and gauge invariant measure of laser intensity and explicitly calculate and interpret it for crossed field, plane wave and vortex models.