Pair creation, backreaction, and resummation in strong fields

TL;DR

This paper analyzes particle creation and backreaction in strong electromagnetic fields using an amplitudes perspective, explicitly evolving the photon state and resumming loop diagrams to go beyond background field approximations.

Contribution

It introduces a method to incorporate backreaction effects by evolving an initial photon coherent state and resumming loop diagrams, advancing beyond traditional background field approaches.

Findings

Expressions for waveform, vacuum persistence, and photon number at next-to-leading order.

Backreaction significantly impacts observable quantities.

Resummation of disconnected loop diagrams is necessary for accurate in-out and in-in amplitude conversions.

Abstract

We revisit particle creation in strong fields, and backreaction on those fields, from an amplitudes perspective. We describe the strong field by an initial coherent state of photons which we explicitly evolve in time, thus going beyond the background field approximation, and then consider observables which quantify the effects of backreaction. We present expressions for the waveform, vacuum persistence probability, and number of produced photons at next-to-leading order, all of which are impacted by backreaction, along with the number and statistics of produced pairs. We find that converting between in-out (amplitude) and in-in (expectation value) expressions requires explicit resummation of an infinite number of disconnected loop diagrams.