# Finding quantum effects in strong classical potentials

## TL;DR

This paper discusses the challenges and limitations of current semiclassical methods in describing quantum effects, such as radiation and photon emission, in strong classical electromagnetic fields, emphasizing the need for improved theories for laser-plasma experiments.

## Contribution

The paper identifies the breakdown of existing semiclassical methods in highly relativistic regimes and highlights the necessity for their improvement to accurately model quantum effects in strong fields.

## Key findings

- Current methods fail for highly relativistic particles in strong fields.
- Quantum electrodynamics provides a promising framework for better models.
- Experimental efforts are crucial for validating new theories.

## Abstract

The long-standing challenge to describing charged particle dynamics in strong classical electromagnetic fields is how to incorporate classical radiation, classical radiation reaction and quantized photon emission into a consistent unified framework. The current, semiclassical methods to describe dynamics of quantum particles in strong classical fields also provide the theoretical framework for fundamental questions in gravity and hadron-hadron collisions, including Hawking radiation, cosmological particle production and thermalization of particles created in heavy-ion collisions. However, as we show, these methods break down for highly relativistic particles propagating in strong fields. They must therefore be improved and adapted for the description of laser-plasma experiments that typically involve the acceleration of electrons. Theory developed from quantum electrodynamics, together with dedicated experimental efforts, offer the best-controllable context to establish a robust, experimentally-validated foundation for the fundamental theory of quantum effects in strong classical potentials.